EXPERIMENTAL RESEARCHES 


IN 


ELECTRICITY. 


BY 

MICHAEL' FARADAY, \D.C.L., ER.S. 

FULLERTAN PROFESSOR OF CHEMISTRY IN THE ROYAL INSTITUTION. 

CORRESPONDING MEMBER, ETC., OF TI1E ROYAL AND IMPERIAL ACADEMIES OF 
SCIENCE OF PARIS, PETERSBURG!!, FLORENCE, COPENHAGEN, BERLIN, 
GOTTINGEN, MODENA, STOCKHOLM, PALERMO, ETC. ETC. 


Reprinted from the I’hii.osopiiicai. Transactions of 1831 — 1838. 


VOLUME I. 


LONDON : 

BERNARD QUAR1TCII, 15 PICCADILLY. 
1839? 

[ Facsimile reprint .] 




PRINTED BY TAYLOR AND ERANCIS 3 
RED LION COURT, FLEET STREET. 



P K E F A C E. 


I ha. ye been induced by various circumstances to collect 
in One Volume the Fourteen Series of Experimental 
Researches in Electricity, which have appeared in the 
Philosophical Transactions during the last seven years : 
the* chief reason has been the desire to supply at a 
moderate price the whole of these papers, with an 
Index, to those who may desire to have them. 

The readers of the volume will, I hope, do me the 
justice to remember that it was not written as a whole , 
but in parts ; the earlier portions rarely having any 
known relation at the time to those which might follow. 
If I had rewritten the work, I perhaps might have con- 
siderably varied the form, but should not have altered 
much of the real matter : it would not, however, then 
have been considered a faithful reprint or statement 
of the course and results of the whole investigation, 
"which only I desired to supply. 

I may be allowed to express my great satisfaction at 
finding, that the different parts, written at intervals 
during seven years, harmonize so well as they do. 
Th^re would have been nothing particular in this, if 
the parts had related only to matters well ascertained 
before any of them were written : — but as each pro- 
fesses to contain something of original discovery, or of 



iv 


PREFACE. 


correction of received views, it does surprise even my 
partiality, that they should have the degree of con- 
sistency and apparent general accuracy which they 
seem to me to present. 

I have made some alterations in the text, but* tjxey 
have been altogether of a typographical or grammati - 
cal character ; and even where greatest, have been in- 
tended to explain the sense, not to alter it. I have 
often added Notes at the bottom of the pf ige, as to 
paragraphs 59, 360, 439, 521, 552, 555, 598, 657, 883, 
for the correction of errors, and also the purpose of 
illustration : but these are all distinguished from the 
Original Notes of the Researches by the date of *Dec. 
1838. 

The date of a scientific paper containing any preten- 
sions to discovery is frequently a matter of serious im- 
portance, and it is a great misfortune that there are 
many most valuable communications, essential to the 
history and progress of science, with respect to which 
this point cannot now be ascertained. This arises from 
the circumstance of the papers having no dates attached 
to them individually, and of the journals in which they 
appear having such as are inaccurate, i. e . dates of a 
period earlier than that of publication. I may refer to 
the note at the end of the Eirst Series, as an illustration 
of the kind of confusion thus produced. These circum- . 
stances have induced me to affix a elate at the top of 
every other page, and I have thought myself justified in 
using that placed by the Secretary of the Royal Society 
on each paper as it was received. An author has no 
right, perhaps, to claim an earlier one, unless it has 
received confirmation by some public act or officer. * 



PREFACE. 


y 


Before conbluding these lines I would beg leave to 
make a reference or two ; first, to my own Papers on 
Electro-magnetic Potations in the Quarterly Journal 
of Science, 1822., xii. 74. 18G. 283. 416. and also to my 
Letter*on Magneto-electric Induction in the Annales 
de Chimie, li. p. 404. These might, as to the matter, 
vqry properly have appeared in this volume, but they 
would have interfered with it as a simple reprint of 
the “Experimental Researches” of the Philosophical 
Transactions. 

Then I wish to l'efer, in relation to the Fourth Series 
on a new law of Electric Conduction, to Franklin’s ex- 
periments on the non-conduction of icc, which have 
been very properly separated and set forth by Professor 
Bachc, (Journal of the Franklin Institute, 1836. xvii. 
183). These, which I did not at all remember as to 
the extent of the effect, though they in no way antici- 
pate the expression of the law I state as to the general 
effect of liquefaction on electrolytes, still should never 
be forgotten when speaking of that law as applicable 
to the case of water. 

There are two papers which I am anxious to refer 
to, as corrections or criticisms of parts of the Experi- 
mental Researches. The first of these is one by J acobi, 
^Philosophical Magazine, 1838, xiii. 401) relative to 
the possible production of a spark on completing the 
junction of the two metals of a single pair of plates 
(915.)*. It is an excellent paper, and though I have 
not repeated the experiments, the description of them 
convinces me that I must have been in error. The 
second is by that excellent philosopher, Marianini, 
(Memoria della Societa Italiana di Modena, xxi. 205), 
and is a critical and experimental examination of 



vi 


PREFACE. 


Series viii, and of the question whether metallic con- 
tact is or is not productive of a part of the electricity 
of the voltaic pile. I see no reason as yet to alter the 
opinion I have given ; but the paper is so very valu- 
able, comes to the question so directly, and tKe point 
itself is of such great importance, that I intend at the 
first opportunity renewing the inquiry, and, if I can, 
rendering the proofs either on the one side or the other 
undeniable to all. 

Other parts of these researches have received the 
honor of critical attention from various philosophers, 
to all of whom I am obliged, and some of whose cor- 
rections I have acknowledged in the foot notes. * There 
are, no doubt, occasions on which I have not felt the 
force of the remarks, but time and the progress o£ 
science will best settle such cases ; and, although I 
cannot honestly say that I wish to be found in error, 
yet I do fervently hope that the progress of science in 
the hands of its many zealous present cultivators will 
be such, as by giving us new and other developments, 
and laws more and more general in their applications, 
will even make me think that what is written and 
illustrated in these experimental researches, belongs 
to the by-gone parts of science. 

MICHAEL EAEADAY. ' 

Royal Institution, 

March, 1839. 



CONTENTS. 


. jrar. 

Series I. §. 1. Induction of electric currents 0 

§. 2. Evolution of electricity from magnetism .... 27 

§. 3. Hew electrical state or condition of matter . . 60. 
§. 4. Explication of Arago’s magnetic phenomena . 31 

Series II. §. 5. Terrestrial magneto-electric induction 140 

§. 6. Force and direction of magneto -electric induc- 
tion generally 193 

Series III. §. 7. Identity of electricities from different sources 265 

i Voltaic electricity . 268 

ii Ordinary electricity 284 

iii Magneto-elect licity 343 

iv Thermo-electricity 349 

v Animal electricity 351 

§. 8. Itclation by measure of common and voltaic 

electricity 361 

Note respecting Ampere’s inductive results 

after 379 

Series IV. §. 9. Hew law of electric conduction 380 

§. 10. On conducting power generally 418 

Series V. §. 11. Electro -chemical decomposition 450 

1. Hew conditions of electro- chemical de- 
composition 453 

2. Influence of water in such decomposition 472 

3. Theory of electro- chemical decomposi- 
tion 477 

Series VI. §. 12. Power of platina &c. to induce combination . 564 

Series VII. §. 11.* Electro-chemical decomposition continued 

(nomenclature) 661 

If 4. Some general conditions of electro-che- 
mical decomposition 669 

5. Volta- electrometer 704 

% 6. Primary and secondary results 742 

7. Definite nature and extent of electro- 
chemical forces 783 

Electro -chemical equivalents 822 



V1U 


CONTENTS. 


Par. 

§.'13. Absolute quantity of electricity iti the mole- 

, <5ules of matter . . 852 

Series VIII. §. 14. Electricity of the voltaic pile 875 

^f 1. Simple voltaic circles 875 

% 2. Electrolytic intensity 966 

If 3. Associated voltaic circles ; or battery*. . 989 

9jj 4. Resistance of an electrolyte to decompo- 
sition 1007 

If 5. General remarks on the active battery, . 1034 

Series IX. §. 15. Induction of a current on itself 1048 

Inductive action of currents generally 1101 

Series X. §. 10. Improved voltaic battery 1119 

§. 17. Practical results with the voltaic battery , . 1130 

Sorics XI. §. 18. On static induction . . . . « 1161 

If 1 . Induction an action of contiguous particles 1161 

^f 2. Absolute charge of matter 1169 

*f[ 3. Electrometer and inductive apparatus » . 1179 

^f.4. Induction in curved lines 1215 

Conduction by glass, lac, sulphur, &c. . . 1233 

If 5. Specific inductive capacity 1252 

If 6. General results as to the nature of induc- 
tion 1295 

Differential inductometer 1307 

Series XII. If 7. Conduction or conductive discharge, . . . 1320 

If 8. Electrolytic discharge 1343 

If 9. Disruptive discharge 1359 

Insulation 1362 

— as spark 1406 

as brush 1425 

positive and negative 1465 

Series XIII. as glow 1526 

* — dark 1544 

% 10. Convection ; or carrying discharge . . 1562 

If 11. Relation of a vacuum to electrical phe- 
nomena 1613 

§.19. Naturo of the electric current c . 1617 

its transverse forces 1653 

Series XIV, §. 20. Xature of the electric force or forces 1667 

§. 21. Relation of the electric and magnetic forces «i 1709 
§. 22. Note on electrical oxcitation 17^7 



EXPERIMENTAL researches 

IN 

ELECTRICITY. 


FIRST SERIES. 

§ 1. On the Induction of Electric Currents, § 2. On the Evo- 
lution of Electricity from Magnetism. §3. On a new Elec- 
trical Condition of Matter . § 4. On Arago's Magnetic Phe- 

nomena. 

[Read November 24, 1831.] 

i. The power which electricity of tension possesses of cau- 
sing an opposite electrical state in its vicinity has been ex- 
pressed by the general term Induction; which, as it has been 
received into scientific language, may also, with propriety, be 
used in the same general sense to express the power which 
electrical currents may possess of inducing any particular state 
upon matter in their immediate neighbourhood, otherwise in- 
different. It is with this meaning that I purpose using it in 
the present paper. 

2. .Certain effects of the induction of electrical currents have 
already been recognised and described: as those of magneti- 
zation ; Ampere's experiments of bringing a copper disc near 
to a flat spiral ; his repetition with electro -magnets of Arago's 
extraordinary experiments, and perhaps a few others. Still it 
appeared unlikely that these could be all the effects which in- 
duction "by currents could produce ; especially as, upon dis- 
pensing with iron, almost the whole of them disappear, whilst 
yet an infinity of bodies, exhibiting definite phenomena of in- 



2 Induction of Electric Currents. [Series I. 

duction with electricity of tension, still remain to be acted upon 
by the induction of electricity in motion. 

3. Further : Whether Ampere's beautiful theory were adop- 
ted, or any otjier, or whatever reservation were mentally made, 
still it appeared very extraordinary, that as every electric cur- 
rent was accompanied by a corresponding intensity of magnetic 
action at right angles to the current, good conductors of elec- 
tricity, when placed within the sphere of this action, should 
not have any current induced through them, or some sensible 
effect produced equivalent in force to such a current. 

4. These considerations, with their consequence, the hope 
of obtaining electricity from ordinary magnetism, have stimu- 
lated me at various times to investigate experimentally the in- 
ductive effect of electric currents. I lately arrived at positive 
results ; and not only had my hopes fulfilled, hut obtained a 
key which appeared to me to open out a full explanation of 
Arago's magnetic phenomena, and also to discover a new state, 
which may probably have great influence in some of the most 
important effects of electric currents. 

5. These results I purpose describing, not as they w r ere ob- 
tained, but in such a manner as to give the most concise view 
of the whole. 


§ 1. Induction of Electric Currents. 

6. About twenty-six feet of copper wire one twentieth of an 

inch in diameter were wound round a cylinder of wood as a 
helix, the different spires of which were prevented from touch- 
ing by a thin interposed twine. This helix was covered with 
calico, and then a second wire applied in the same manner. In 
this way twelve helices were superposed, each containing an 
average length of wire of twenty-seven feet, and all in the same 
direction. The first, third, fifth, seventh, ninth, and eleventh 
of these helices were connected at tlicir extremities qnd to 
end, so as to form one helix ; the others were connected in a 
similar maimer ; and thus two principal helices were produced, 
closely interposed, having the same direction, not touching any- 
where, and each containing one hundred and fifty-five feet in 
length of wire. « 

7. One of these helices was connected with a galvanometer, 
the other with a voltaic battery of ten pairs of plates four inches 



3 


Nov. 1831.] Induction of Electric Currents . 

square, with dguble coppers and well charged; yet not the 
slightest sensible deflection of the galvanometer needle could 
be observed. 

8. A similar compound helix, consisting of six lengths of 
copper .and six of soft iron wire, was constructed. The result- 
ing iron helix contained two hundred and fourteen feet of wire, 
the resulting copper helix two hundred and eight feet; but 
whether the current from the trough was passed through the 
copper or the iron helix, no effect upon the other could be per- 
ceived at the galvanometer. 

9. In these and many similar experiments no difference in 
action of any kind appeared between iron and other metals. 

10. Two hundred and three feet of copper wire in one length 
were coiled round a Targe block of wood ; other two hundred 
and three feet of similar wire were interposed as a spiral be- 
tween the turns of the first coil, and metallic contact every- 
where prevented by twine. One of these helices was connected 
with a galvanometer, and the other with a battery of one hun- 
dred pairs of plates four inches square, with double coppers, 
and well charged. When the contact was made, there was a 
sudden and very slight effect at the galvanometer, and there 
was also a similar slight effect when the contact with the bat- 
tery was broken. But whilst the voltaic current was continu- 
ing to pass through the one helix, no galvanomctrical appear- 
ances nor any effect like induction upon the other helix could 
be perceived, although the active power of the battery was 
proved to be great, by its heating the whole of its own helix, 
and by the brilliancy of the discharge when made through 
charcoal. 

11. Repetition of the experiments with a battery of one hun- 
dred and twenty pairs of plates produced no other effects; but 
it was ascertained, both at this and the former time, that the 
slight*deflection of the needle occurring at the moment of com- 
pleting the connexion, was always in one direction, and that 
the equally slight deflection produced when the contact was 
broken, was in the other direction ; and also, that these effects 
occurred^when the first helices were used (6. 8.). 

12. The results which I had by this time obtained with mag- 
nets led me to believe that the battery current through one 
wire, did, in reality, induce a similar current through the other 

b 2 



4 Iihluction of Electric Currents. [Series I. 

wire, but that it continued for an instant only, and partook 
more of the nature of the electrical wave passed through from 
the shock of a common Leyden jar than of the current from a 
voltaic battery, and therefore might magnetise a steel needle, 
although it scarcely affected the galvanometer. 

13. This expectation was confirmed; for on substituting a 
small hollow helix, formed round a glass tube, for the galvano- 
meter, introducing a steel needle, making contact as before 
between the battery and the inducing wire (7. 10.), and then 
removing the needle before the battery contact was broken, it 
was found magnetised. 

14. When the battery contact was first made, then an unmag- 
netised needle introduced into the small indicating helix (13.), 
and lastly the battery contact broken, “the needle was found 
magnetised to an equal degree apparently as before ; but the 
poles were of the contrary kind. 

15. The same effects took place on using the large compound 
helices first described (6. 8.). 

16. When the unmagnetised needle was put into the indica- 
ting helix, before contact of the inducing wire with the battery, 
and remained there until the contact was broken, it exhibited 
little or no magnetism ; the first effect having been nearly neu- 
tralised by the second (13. 14.). The force of the induced cur- 

I rent upon making contact was found always to exceed that of 
, the induced current at breaking of contact ; and if therefore 
the contact was made and broken many times in succession, 
whilst the needle remained in the indicating helix, it at last 
came out not unmagnetised, but a needle magnetised as if the 
induced current upon making contact had acted alone on it. 

. , cflect ma y hc due t0 accumulation (as it is called) at 
tie poles of the unconnected pile, rendering the current upon 
first making contact more powerful than what it is afterwards, 
at the moment of breaking contact. 

17. If the circuit between the helix or wire under induction 
and the galvanometer or indicating spiral was not rendered 
complete before the connexion between the battery and the in- 
ducing wire was completed or broken, then no effects were 
perceived at the galvanometer. Thus, if the batter/ commu- 
nications were first made, and then the; wire under induction 

connected with the indicating helix no * 

g nenx, no magnetising power \yas 



5 


Nov. 1831.] Induction of Electric Currents . 

there exhibited,. But still retaining the latter communications, 
when those with the battery were broken, a magnet was formed 
in the helix, but of the second kind (11.), i.e. with poles indi- 
cating a current in the same direction to that belonging to the 
batter^ current, or to that always induced by that current at 
its cessation. 

18. In the preceding experiments the wires were placed near 
t<j each other, and the contact of the inducing one with the 
battery made Avhen the inductive effect was required; but as 
the particular action might be supposed to be exerted only at 
the moments of making and breaking contact, the induction 
was produced in another way. Several feet of copper wire 
were stretched in wide zigzag forms, representing the letter W, 
on one surface of a bio ad board ; a second wire was stretched 
in precisely similar forms on a second board, so that when 
brought near the first, the wires should everywhere touch, ex- 
cept that a sheet of thick paper was interposed. One of these 
wires was connected with the galvanometer, and the other with 
a voltaic battery. The first wire was then moved towards the 
second, and as it approached, the needle was deflected. Being 
then removed, the needle was deflected in the opposite direc- 
tion. By first making the wires approach and then recede, si- 
multaneously with the vibrations of the needle, the latter soon 
became very extensive; but when the wires ceased to move 
from or towards each other, the galvanometer-needle soon camp 
to its usual position. 

19. As the wires approximated, the induced current was in 
the contrary direction to the inducing current. As the wires 
receded, the induced current was in the same direction as the 
inducing current. When the wires remained stationary, there 
was no induced current (51-.). 

20. When a small voltaic arrangement was introduced into 
the circuit between the galvanometer (10.) and its helix or wire, 
so as to cause a permanent deflection of 30° or 40°, and then 
the battery of one hundred pairs of plates connected with the 
inducing wire, there was an instantaneous action as before (11.) ; 
but the galvanometer-needle immediately resumed and retained 
its place* unaltered, notwithstanding the continued contact of 
tlffe inducing wire with the trough : such was the case in 
whichever way the contacts were made (33.). 



6 Induction of Electric Currents , [Series I. 

21. Hence it would appear that collateral currents, either in 
the same or in opposite directions, exert no permanent inducing 
power on each other, affecting their quantity or tension. 

' 22. I could obtain no evidence by the tongue, by spark, or 
by heating fine wire or charcoal, o£ the electricity passing 
through the wire under induction ; neither could I obtain any 
chemical effects, though the contacts with metallic and other 
solutions were made and broken alternately with those of the 
battery, so that the second effect of induction should not oppose 
or neutralize the first (13. 16.). 

23. This deficiency of effect is not because the induced cur- 
rent of electricity cannot pass fluids, but probably because of 
its brief duration and feeble intensity ; for on introducing two 
large copper plates into the circuit on the induced side (20.), 
the plates being immersed in brine, but prevented from touch- 
ing each other by an interposed cloth, the effect at the indica- 
ting galvanometer or helix occurred as before. The induced 
electricity could also pass through a voltaic trough (20.). 
When, however, the quantity of interposed fluid was reduced 
to a drop, the galvanometer gave no indication. 

24. Attempts to obtain similar effects by the use of wires 
conveying ordinary electricity were doubtful in the results. A 
compound helix similar to that already described, containing 
eight elementary helices (6.), was used. Four of the helices had 
their similar ends bound together by wire, and the two general 
terminations thus produced connected with the small magneti- 
sing helix containing an unmagnetised needle (13.). The 
other four helices were similarly arranged, but their ends con- 
nected with a Leyden jar. On passing the discharge, the 
needle was found to be a magnet; but it appeared probable 
that a part of the electricity of the jar had passed off to the small 
helix, and so magnetised the needle. There was indeed no 
reason to expect that the electricity of a jar possessingc as it 
does great tension, would not diffuse itself through all the me- 
tallic matter interposed between the coatings. 

I 25. Still it does not follow that the discharge of ordinary 
• electricity through a wire does not produce analagous' pheno- 
; raena to those arising from voltaic electricity ; but as if appears 
; impossible to separate the effects produced at the moment when 
I the discharge begins to pass, from the equal and contrary effects 



7 


NoV. 1831.] Evolution of Electricity from Magnetism . 

produced when it ceases to pass (16.) , inasmuch as with ordi- 
nary electricity* these periods are simultaneous, so there can be 
scarcely any hope that in this form of the experiment they can 
be perceived. 

26. Hence it is evident that currents of voltaic electricity 
present phenomena of induction somewhat analagous to those 
produced by electricity of tension, although, as will be seen here- 
after, many differences exist between them. The result is the 
production of other currents, (but which are only momentary,) 
parallel, or tending to parallelism, with the inducing current. 
By reference to the poles of the needle formed in the indicating 
helix (13. 14.) and to the deflections of the galvanometer- 
needle (11.), it was found in all cases that the induced current, 
produced by the first action of the inducing current, was in 
the contrary direction to the latter, but that the current pro- 
duced by the cessation of the inducing current was in the same 
direction (19.). For the purpose of avoiding periphrasis, I 
propose to call this action of the current from the voltaic bat- 
tery volta-electric induction. The properties of the second 
wire, after induction has developed the first current, and whilst 
the electricity from the battery continues to flow through its 
inducing neighbour (10. 18.), constitute a peculiar electric con- 
dition, the consideration of which will be resumed hereafter 
(60.) . All these results have been obtained with a voltaic ap- 
paratus consisting of a single pair of plates. 

§ 2. Evolution of Electricity from Magnetism. 

27. A welded ring was made of soft round bar-iron, the 
metal being seven eighths of an inch in thickness, and the ring 
six inches in external diameter. Three helices were put round 
one part of this ring, each containing about twenty-four feet of 
copper wire one twentieth of an inch thick ; they were insula- 
ted from the iron and each other, and superposed in the manner 
before described (6.), occupying about nine inches in length 
upon the ring. They could be used separately or conjointly ; 
the group may be distinguished by the letter A (PL I. fig. 1.). 
On the other part of the ring about sixty feet of similar copper 
ijire in two pieces were applied in the same manner, forming a 
helix B, which had the same common direction with the helices 



8 Evolution of Electricity from Magnetism. [Series I. 

of A, but being separated from it at each extremity by about 
half an inch of the uncovered iron. 

28. The helix B was connected by copper wires with a galva- 
nometer three feet from the ring. The helices of A were 
connected end to end so as to form one common helix, the ex- 
tremities of which were connected with a battery of ten pairs 
of plates four inches square. The galvanometer was immedi- 
ately affected, and to a degree far beyond what has been 
described when with a battery of tenfold power helices without 
iron were used (10.) ; but though the contact was continued, 
the effect was not permanent, for the needle soon came to rest 
in its natural position, as if quite indifferent to the attached 
electro- magnetic arrangement. Upon breaking the contact 
with the battery, the needle was again powerfully deflected, 
but in the contrary direction to that induced in the first in- 
stance. 

29. Upon arranging the apparatus so that B should be out 
of use, the galvanometer be connected with one of the three 
wires of A (27.), and the other two made into a helix through 
which the current from the trough (28.) was passed, similar 
but rather more powerful effects were produced. 

30. When the battery contact was made in one direction, 
the galvanometer-needle was deflected on the one side; if made 
in the other direction, the deflection was on the other side. 
The deflection on breaking the battery contact, was always the 
reverse of that produced by completing it. The deflection on 
making a battery contact always indicated an induced current 
in the opposite direction to that from the battery ; but on 
breaking the contact the deflection indicated an induced cur- 
rent in the same direction as that of the battery. No making 
or breaking of the contact at B side, or in any part of the gal- 
vanometer circuit, produced any effect at the galvanometer. 
No continuance of the battery current caused any deflection of 
the galvanometer-needle. As the above results are common 
to all these experiments, and to similar ones with ordinary 
magnets to be hereafter detailed, they need not be again parti- 
cularly described. 

31. Upon using the power of one hundred pairs of plates 
(10.) with this ring, the impulse at the galvanometer, when* 



Nov. 1831.] Evolution of Electricity from Magnetism. 9' 

contact was completed or broken, was so great as to make tlie 
needle spin round rapidly four or five times, before the air and 
terrestial magnetism could reduce its motion to mere oscilla- 
tion. 

32. By using charcoal at the ends of the B helix, a minute 
spai'k could be perceived when the contact of the battery with 
A was completed. This spark could not be due to any diver- 
sion of a part of the current of the battery through the iron to 
the helix B ; for when the battery contact was continued, the 
galvanometer still resumed its perfectly indifferent state (28.). 
The spark was rarely seen on breaking contact. A small pla- 
tina wire could not be ignited by this induced current ; but 
there seems every reason to believe that the effect would be 
obtained by using a stronger original current or a more power- 
ful arrangement of helices. 

33. A feeble voltaic current was sent through the helix B, 
and the galvanometer, so as to deflect the needle of the latter 
30° or 40°, and then the battery of one hundred pairs of plates 
connected with A ; but after the first effect was over, the gal- 
vanometer-needle resumed exactly the position due to the 
feeble current transmitted by its own wire. This took place 
in whichever way the battery contacts were made, and shows 
that here again (20.) no permanent influence of the currents 
upon each other, as to their quantity and tension, exists. 

34. Another arrangement was then employed connecting 
the former experiments on volta-electric induction (6 — 26.) with 
the present. A combination of helices like that already de- 
scribed (6.) was constructed upon a hollow cylinder of paste- 
board : there were eight lengths of copper wire, containing 
altogether 220 feet ; four of these helices were connected end 
to end, and then with the galvanometer (7.) ; the other inter- 
vening four were also connected end to end, and the battery 
of oi\e hundred pairs discharged through them. In this form 
the effect on the galvanometer was hardly sensible (11.), though 
magnets could be made by the induced current (13.). But 
when a soft iron cylinder seven eighths of an inch thick, and 
twelve inches long, was introduced into the pasteboard tube, 
surrounded by the helices, then the induced current affected 
the galvanometer powerfully, and with all the phenomena just 
described (30.). It possessed also the power of making mag- 



10 Evolution of Electricity from Magnetism . [Series I, 

nets ■with more energy, apparently, than when no iron cylinder 
was present. 

35. When the iron cylinder was replaced by an equal cylin- 
vder of copper, no effect beyond that of the helices alone was 
produced. The iron cylinder arrangement was not so powerful 
as the ring arrangement already described (27 .) . 

36. Similar effects were then produced by ordinary mag- 
nets : thus the hollow helix just described (34.) had all its ele- 
mentary helices connected with the galvanometer by two cop- 
per wires, each five feet in length ; the soft iron cylinder was 
introduced into its axis ; a couple of bar magnets, each twenty- 
four inches long, were arranged with their opposite poles at 
one end in contact, so as to resemble a horse-shoe magnet, and 
then contact made between the other polos and the ends of the 
iron cylinder, so as to convert it for the time into a magnet 
(fig. 2.) : by breaking the magnetic contacts, or reversing .them, 
the magnetism of the iron cylinder could be destroyed or re- 
versed at pleasure. 

37. Upon making magnetic contact, the needle was deflected ; 
continuing the contact, the needle became indifferent, and re- 
sumed its first position ; on breaking the contact, it was again 
deflected, but in the opposite direction to the first effect, and 
then it again became indifferent. When the magnetic con- 
tacts were reversed the deflections were reversed. 

38. When the magnetic contact was made, the deflection 
was such as to indicate an induced current of electricity in the 
opposite direction to that fitted to form a magnet, having the 
same polarity as that really produced by contact with the bar 
magnets. Thus when the marked and umnarked poles were 
placed as in fig. 3, the current in the helix was in the direction 
represented, P being supposed to be the end of the wire going 
to the positive pole of the battery, or that end towards which 
the zinc plates face, and N the negative wire. Such a current 
would have converted the cylinder into a magnet of the oppo- 
site kind to that formed by contact with the poles A and 13 ; 
and such a current moves in the opposite direction to the cur- 
rents which in M. Ampere's beautiful theory are considered as 
constituting a magnet in the position figured *. 

* The relative position of an electric current and a magnet is by most pejv 
sons found very difficult to remember, and three or four helps to the memory 



Nov. 1831.] Evolution of Electricity from Magnetism . 11 

39. But as might be supposed that in all the preceding 
experiments of this section, it was by some peculiar effect 
taking place during the formation of the magnet, and not by its 
mere virtual approximation, that the momentary induced cur- 
rent was excited, the following experiment was made. All the 
similar ends of the compound hollow helix (34.) were bound 
together by copper wire, forming two general terminations, 
apd_ these were connected with the galvanometer. The soft 
iron cylinder (31.) was removed, and a cylindrical magnet, 
three quarters of an inch in diameter and eight inches and a 
half in length, used instead. One end of this magnet was in- 
troduced into the axis of the helix (fig. 4.), and then, the gal- 
vanometer-needle being stationary, the magnet was suddenly 
thrust in ; immediately the needle was deflected in the same 
direction as if the magnet had been formed by cither of the 
two preceding processes (34. 30.) - Being left in, the needle 
resumed its first position, and then the magnet being with- 
drawn the needle was deflected in the opposite direction. 
These effects were not great; but by introducing and with-! 
drawing the magnet, so that the impulse each time should bet 
added to those previously communicated to the needle, the lat- 
ter could be made to vibrate through an are of 180° or more. 

40. In this experiment the magnet must not be passed en- 
tirely through the helix, for then a second action occurs, i 
When the magnet is introduced, the needle at the galvanome- 
ter is deflected in a certain direction ; but being in, whether it 
be pushed quite through or withdrawn, the needle is deflected 1 
in a direction the reverse of that previously produced. When 
the magnet is passed in and through at one continuous motion, 

have been devised by M. Ampere and others. I venture to suggest the follow- 
ing as a very simple and effectual assistance in these and similar latitudes. Let 
the experimenter think he is looking down upon a dipping needle, or upon the 
pole o # f the earth, and then let him think upon the direction of the motion of 
the hands of a watch, or of a screw moving direct; currents in that direction 
round a needle would make it into such a magnet as the dipping needle, or 
would themselves constitute an electro-magnet of similar qualities; or if 
brought near a magnet would tend to make it take that direction ; or would 
themselves be moved into that position by a magnet so placed ; or in M. 
Ampere’s* theory .are considered as moving in that direction in the magnet. 
Xhese two points of the position of the dipping-needle and the motion of the 
watch hands being remembered, any other relation of the current and the 
magnet can be at once deduced from it. 



12 ' Evolution of Electricity from Magnetism . [Series T. 

the needle moves one way, is then suddenjy stopped, and 
finally moves the other way. 

41 . If such a hollow helix as that described (34.) be laid 
east and west (or in any other constant position), and a magnet 
be retained east and west, its marked pole always being one 
way ; then whichever end of the helix the magnet goes in at, 
and consequently whichever pole of the magnet enters first, 
still the needle is deflected the same way : on the other hand, 
whichever direction is followed in withdrawing the magnet, 
the deflection is constant, but contrary to that due to its en- 
trance. 

42. These effects are simple eonsequeuces of the law here- 
after to be described (1 1 4.) . 

43. When the eight elementary helices were made one long 
helix, the effect was not so great as in the arrangement de- 
scribed. When only one of the eight helices was used, the 
effect was also much diminished. All care was taken to guard 
against any direct action of the inducing magnet upon the 
galvanometer, and it was found that by moving the magnet in 
the same direction, and to the same degree on the outside of 
the helix no effect on the needle was produced. 

44. The Royal Society are in possession of a large com- 
pound magnet formerly belonging to Dr. Gowin Knight, 
which, by permission of the President and Council, I w as al- 
lowed to use in the prosecution of these experiments : it is at 
present in the charge of Mr. Christie, at his house at Wool- 
wich, where, by Mr. Christie’s kindness, I was at liberty to 
work ; and I have to acknowledge my obligations to him for 
his assistance in all the experiments and observations made 
with it. This magnet is composed of about 450 bar magnets, 
each fifteen inches long, one inch wide, and half an inch thick, 
arranged in a box so as to present at one of its extremities two 
external poles (fig. 5.). These poles projected horizontally six 
inches from the box, were each twelve inches high and three 
inches wide. They were nine inches apart* and when a soft 
iron cylinder, three quarters of an inch in diameter and twelve 
inches long, was put across from one to the other, it required 
a force of nearly one hundred pounds to break the Contact. 
The pole to the left in the figure is the marked pole*. 

* To avoid any confusion as to tlio pole* of the magnet, I shall designate the 



Nov. 1831.] Evolution of Electricity from Magnetism. * 13 

45. The indicating galvanometer, in all experiments made 
with this magnet, was about eight feet from it, not directly in 
front of the poles, but about 16° or 17° on one side. It was 
found that on making or breaking the connexion of the poles by 
soft iron, the instrument was slightly affected ; but all error of 
observation arising from this cause was easily and carefully 
avoided. 

46. The electrical effects exhibited by this magnet were very 
striking. When a soft iron cylinder thirteen inches long was 
put through the compound hollow helix, with its ends arranged 
as two general terminations (39.), these connected with the 
galvanometer, and the iron cylinder brought in contact with 
the two poles of the magnet (fig. 5.), so powerful a rush of 
electricity took place- that the needle whirled round many times 
in succession*. 

47. Notwithstanding this great power, if the contact w r as 
continued, the needle resumed its natural position, being en- 
tirely uninfluenced by the position of the helix (30.). But on 
breaking the magnetic contact, the needle was whirled round 
in the opposite direction with a force equal to the former. 

48. A piece of copper plate wrapped once round the iron 
cylinder like a socket, but wifh interposed paper to prevent 
contact, had its* edges connected with the wires of the galva- 
nometer. When the iron was brought in contact with the poles 
the galvanometer was strongly affected. 

49. Dismissing the helices and sockets, the galvanometer 
wire was passed over, and consequently only half round the 
iron cylinder (fig. 6.) ; but even then a strong effect upon the 
needle was exhibited, when the magnetic contact was made or 
broken. 

50. As the helix with its iron cylinder was brought towards 
the magnetic poles, but without making contact , still powerful 
effects were produced. When the helix, without the iron cy- 
linder, and consequently containing no metal but copper, was 
approached to, or placed between the poles (44.), the needle 

pole pointing to the north as the marked pole ; I may occasionally speak of 
the north and south ends of the needle, but do not mean thereby north and 
south pofes. That is by many considered the true north pole of a needle which 
points to the south ; but in this country it is often called the south pole. 

* * A soft iron bar in the form of a lifter to a horse-shoe magnet, when sup- 
plied with a coil of this kind round the middle of it, becomes, byjuxtaposition 
with a magnet, a ready source of a brief but determinate current of electricity % 



14 Evolution of Electricity from Magnetism. [Series I. 

was thrown 80°, 90°, or *morc, from its natural position. The 
inductive force was of course greater, the nearer the helix, 
either with or without its iron cylinder, was brought to the 
poles ; but otherwise the same effects were produced, whether 
the helix, &c. was or was not brought into contact with the 
magnet ; i. e. no permanent effect on the galvanometer was 
produced ; and the effects of approximation and removal were 
the reverse of each other (30.) . 

51. When a bolt of copper corresponding to the iron cylin- 
der was introduced, no greater effect was produced by the he- 
lix than without it. But when a thick iron wire was substitu- 
ted, the magncto-elcctric induction was rendered sensibly 
greater. 

52. The direction of the electric current produced in all 
these experiments with the helix, was the same as that already 
described (38.) as obtained with the weaker bar magnets.* 

53. A spiral containing fourteen feet of copper wire, being 
connected with the galvanometer, and approximated directly 
towards the marked pole in the line of its axis, affected the in- 
strument strongly; the current induced in it was in the reverse 
direction to the current theoretically considered by M. Am- 
pere as existing in the magnet (38.), or as the current in an 
electro-magnet of similar polarity. As the ‘spiral was with- 
drawn, the induced current was reversed. 

54. A similar spiral had the current of eighty pairs of 4-incli 
plates sent through it so as to form an electro-magnet, and then 
the other spiral connected with the galvanometer (53.) approx- 
imated to it ; the needle vibrated, indicating a current in the 
galvanometer spiral the reverse of that in the battery spiral 
(18. 26.). On withdrawing the latter spiral, the needle passed 
in the opposite direction. 

55. Single wires, approximated in certain directions towards 
the magnetic pole, had currents induced in them. On their re- 
moval, the currents were inverted. In such experiments the 
wires should not be removed in directions different to those in 
which they were approximated ; for then occasionally compli- 
cated and irregular effects arc produced, the causes of which 
will be very evident in the fourth part of this paper. * 

56. All attempts to obtain chemical effects by the induced 
current of electricity failed, though the precautions before de- 
scribed (22.), and all others that could be thought of, were e m - 



Nov. 1831.] Evolution of Electricity from Magnetism. 15 

ployed. Neither was any sensation on the tongue, or any con- 
vulsive effect upon tlie limbs of a frog, produced. Nor could 
charcoal or fine wire be ignited (133.) . But upon repeating 
the experiments more at leisure at the Royal Institution, with 
an armed loadstone belonging to Professor Danicll and capable 
of lifting about thirty pounds, a frog was very powerfully con- 
vulsed each time magnetic contact was made. At first the 
convulsions could not be obtained on breaking magnetic con- 
tact ; but conceiving the deficiency of effect was because of 
the comparative slowness of separation, the latter act was ef- 
fected by a blow, and then the frog was convulsed strongly. 
The more instantaneous the union or disunion is effected, the 
more powerful the convulsion. I thought also I could perceive 
the sensation upon the tongue and the flash before the eyes ; 
but I could obtain no evidence of chemical decomposition. 

57. The various experiments of this section prove, I think, 
most completely the production of electricity from ordinary 
magnetism. That its intensity should be very feeble and quan- 
tity small, cannot be considered wonderful, when it is remem- 
bered that like thermo-electricity it is evolved entirely within 
the substance of metals retaining all their conducting power. 
But an agent which is conducted along metallic wires in the 
manner described ; which, whilst so passing possesses the pe- 
culiar magnetic actions and force of a current of electricity ; 
which can agitate and convulse the limbs of a frog ; and which, 
finally, can produce a spark* by its discharge through charcoal 
(32.), can only be electricity. As all the effects can be pro- 
duced by ferruginous electro-magnets (34.), there is no doubt 
that arrangements like the magnets of Professors Moll, Henry, 
Ten Eyke, and others, in which as many as two thousand 
pounds have been lifted, may be used for these experiments ; 
in which case not only a brighter spark may be obtained, but 
wires also ignited, and, as the current can pass liquids (23.), 
chemical action be produced. These effects are still more 
likely to be obtained when the magneto-electric arrangements 
to be ^explained in the fourth section are excited by the powers 
of such apparatus. 

* Por a mode of obtaining tlie spark from the common magnet which I 
hp.ve found effectual, see the Philosophical Magazine for June 1832, p. 5. In 
the same Journal for November 3834, vol. v. p. 349, will be found a method 
of obtaining the magneto-electric spark, still simpler in its principle, the use 
of soft iron being dispensed with altogether. — Dec. 1838. 



16 Electro-tonic State of Matter . [Series I. 

58. The similarity of action, almost amounting to identity, 
between common magnets and either electro-magnets or volta- 
electric currents, is strikingly in accordance with and confirma- 
tory of M. Ampere's theory, and furnishes powerful reasons 
for believing that the action is the same in both cases ; but, as 
a distinction in language is still necessary, I propose to call the 
agency thus exerted by ordinary magnets, magneto -electric or 
magnelectric induction (26.) . 

59. The only difference which powerfully strikes the atten- 
tion as existing between volta-eleetric and magneto-electric in- 
duction, is the suddenness of the former, and the sensible time 
required by the latter : but even in this early state of investi- 
gation there are circumstances which seem to indicate, that 
upon further inquiry this difference will/ as a philosophical di- 
stinction, disappear (68.) *. 

§ 3. New Electrical State or Condition of Matter f . 

60. Whilst the wire is subject to either volta-electric or mag- 
neto-electric induction, it appears to be in a peculiar state ; for 
it resists the formation of an electrical current in it, whereas, 
if in its common condition, such a current would be produced ; 
and when left uninfluenced it has the power of originating a 
current, a power which the wire does not possess under com- 
mon circumstances. This electrical condition of matter lias 
not hitherto been recognised, but it probably exerts a very im- 
portant influence in many if not most of the phenomena pro- 
duced by currents of electricity. For reasons which will imme- 
diately appear (71.), I have, after advising with several learned 
friends, ventured to designate it as the electro-tonic state. 

61. This peculiar condition shows no known electrical effects 
whilst it continues ; nor have I yet been able to discover any 

* For important additional phenomena and developments of the induction 
of electrical currents, see now the ninth series, 1048-1118.— Dec. 1838. 

t This section having been read at the Royal Society and reported upon, 
and having also, in consequence of a letter from myself to M. Hachette, been 
noticed at the F rench Institute, I feel bound to let it stand aspart of the paper ; 
but later investigations (intimated 73. 76. 77.) of the laws governing these 
phenomena, induce me to think that the latter can be fully explained with- 
out admitting the electro-tonic state. JNIy views on this point will appear *iti 
the second series of these researches. — M. F. 



Nov. 1831.] 


Electrotonic state. 


17 


peculiar powers exerted, or properties possessed, by matter 
whilst retained in this state. 

62. It shows no reaction by attractive or repulsive powers. 
The various experiments which have been made with powerful 
magnets upon such metals as copper, silver, and generally those 
substances not magnetic, prove this point ; for the substances 
experimented upon, if electrical conductors, must have acquired 
this state ; and yet no evidence of attractive or repulsive 
powers has been observed. I have placed copper and silver 
discs, very delicately suspended on torsion balances in vacuo 
near to the poles of very powerful magnets, yet have not been 
able to observe the least attractive or repulsive force. 

63. I have also arranged a fine slip of gold-leaf very near to 
a bar of copper, the two being in metallic contact by mercury 
at their extremities. These have been placed in vacuo, so that 
metal rpds connected with the extremities of the arrangement 
should pass through the sides of the vessel into the air. I have 
then moved powerful magnetic poles, about this arrangement, 
in various directions, the metallic circuit on the outside being 
sometimes completed by wires, and sometimes broken. But I 
never could obtain any sensible motion of the gold-leaf, cither 
directed to the magnet or towards the collateral bar of copper, 
which must have been, as far as induction was concerned, in a 
similar state to itself. 

64. In some cases it has been supposed that, under such cir- 
cumstances, attractive and repulsive forces have been exhibited, 
i. e. that such bodies have become slightly magnetic. But the 
phenomena now described, in conjunction with the confidence 
we may reasonably repose in M. Amperc^s theory of magnet- 
ism, tend to throw doubt on such cases ; for if magnetism de- 
pend upon the attraction of electrical currents, and if the pow- 
erful currents at first excited, both by volta-electric and mag- 
neto-electric induction, instantly and naturally cease (12. 28. 
47.), causing at the same time an entire cessation of magnetic 
effects at the galvanometer needle, then there can be little or 
no expectation that any substances not partaking of the pecu- 
liar relation in which iron, nickel, and one or two other bodies, 
stand, should exhibit magneto-attractive powers. It seems far 
morp probable, that the extremely feeble permanent effects ob- 

c 



IB 'Electrotonic state. [Series I. 

served have been due to traces of iron, or perhaps some other 
unrecognized cause not magnetic. 

65. This peculiar condition exerts no retarding or accele- 
rating power upon electrical currents passing through metal 
thus circumstanced (20. 33.). Neither could any such poWer 
upon the inducing current itself he detected ; for when masses 
of metal, wires, helices, &c. were arranged in all possible ways 
by the side of a wire or helix, carrying a current measured by 
the galvanometer (20.), not the slightest permanent change in 
the indication of the instrument could be perceived. Metal in 
the supposed peculiar state, therefore, conducts electricity in 
all directions with its ordinary facility, or, in other words, its 
conducting power is not sensibly altered by it. 

66. All metals take on the peculiar ‘state. This is proved 
in the preceding experiments with copper and iron (9.), an^l 
with gold, silver, tin, lead, zinc, antimony, bismuth, mercury, 
&c. by experiments to be described in the fourth part (132.), 
admitting of easy application. With regard to iron, the expe- 
riments prove the thoroiigh and remarkable independence of 
these phenomena of induction, and the ordinary magnetical 
appearances of that metal. 

67. This state is altogether the effect of the induction ex- 
erted, and ceases as soon as the inductive force is removed. 
It is the same state, whether produced by the collateral passage 
of voltaic currents (26.), or the formation of a magnet (34. 36.), 
or the mere approximation of a magnet (39. 50.) ; and is a strong 
proof in addition to those advanced by M. Ampere, of the iden- 
tity of the agents concerned in these several operations. It 
probably occurs, momentarily, during the passage of the com- 
mon electric spark (24.), and may perhaps be obtained hereafter 
in bad conductors by weak electrical currents or other means 
(74. 76.). 

68. The state appears to be instantly assumed (12.), re- 
quiring hardly a sensible portion of time for that purpose. The 
difference of time between volta-electric and magneto-electric 
induction, rendered evident by the galvanometer (59.), may 
probably be thus explained. When a voltaic current is sent 
through one of two parallel wires, as those of the hollow helix 
(34.), a current is produced in the other wire, as brief in its 



Electrotonic state. 


19 


Nov. 1831.] 

continuance as the time required for a single action of this kind, 
and which, By experiment, is found to be inappreciably small. 
The action will seem still more instantaneous, because, as there 
is an accumulation of power in the poles of the battery before 
contact, the first rush of electricity in the wire of communica- 
tion is greater than that sustained after the contact is com- 
pleted ; the wire of induction becomes at the moment electro- 
tonic to an equivalent degree, which the moment after sinks 
to fhe state in which the continuous current can sustain it, but 
in sinking, causes an opposite induced current to that at first 
produced. The consequence is, that the first induced wave 
of electricity more resembles that from the discharge of an elec- 
tric jar, than it otherwise would do. 

69. But when the iron cylinder is put into the same helix 
(34.), previous to the connexion being made with the battery, 
then the current from the latter may be considered as active in 
inducing innumerable currents of a similar kind to itself in the 
iron, rendering it a magnet. This is known by experiment to 
occupy time ; for a magnet so formed, even of soft iron, does 
not rise to its fullest intensity in an instant, and it may be be- 
cause the currents within the iron are successive in their forma- 
tion or arrangement. But as the magnet can induce, as well as 
the battery current, the combined action of the two continues to 
evolve induced electricity, until their joint effect is at a maxi*, 
mum, and thus the existence of the deflecting force is pro* 
longed sufficiently to overcome the inertia of the galvanometer 
needle. 

70. In all those cases where the helices or wires are advanced 
towards or taken from the magnet (50. 55.), the direct or in- 
verted current of induced electricity continues for the time 
occupied in the advance or recession ; for the electro- tonic 
state is rising to a higher or falling to a lower degree during 
that time, and the change is accompanied by its corresponding 
evolution of electricity ; but these form no objections to the 
opinion that the electro- tonic state is instantly assumed. 

71. This peculiar state appears to be a state of tension, and 
may be considered as equivalent to a current of electricity, at 
least equal to that produced either when the condition is in- 
duced or destroyed. The current evolved, however, first or 
last, is not to be considered a measure of the degree of tension 

c 2 



20 


Electrotonic state. 


[Series I. 


to which the electro- tonic state has risen; for as the metal re- 
tains its conducting powers unimpaired (65.), and as the elec- 
tricity evolved is but for a moment, (the peculiar state being 
instantly assumed and lost (68.),) the electricity which may be 
led away by long wire conductors, oflering obstruction^ in their 
substance proportionate to their small lateral and extensive 
linear dimensions, can be but a very small portion of that really 
evolved within the mass at the moment it assumes this con- 
dition. Insulated helices and portions of metal instantly as- 
sumed the state; and no traces of electricity could be disco- 
vered in them, however quickly the contact with the electro- 
meter was made, after they were put under induction, either 
by the current from the battery or the magnet. A single drop 
of water or a small piece of moistened paper (23. 56.) was ob- 
stacle sufficient to stop the current through the conductors, 
the electricity evolved returning to a state of equilibrium 
through the metal itself, and consequently in an unobserved 
manner. 

72. The tension of this state may therefore be comparatively 
very great. But whether great or small, it is hardly conceivable 
that it should exist without exerting a reaction upon the 
original inducing current, and producing equilibrium of some 
kind. It might be anticipated that this w^ould give rise to a 
retardation of the original current ; but I have not been able 
to ascertain that this is the case. Neither have I in any other 
way as yet been able to distinguish effects attributable to such 
a reaction. 

73. All the results favour the notion that the electro-tonic 
state relates to the particles, and not to the mass, of the wire 
or substance under induction, being in that respect different 
to the induction exerted by electricity of tension. If so, the 
state may be assumed in liquids when no electrical current is 
sensible, and even in non-conductors ; the current itself, when 
it occurs, being as it were a contingency due to the existence 
of conducting power, and the momentary propulsive force ex- 
erted by the particles during their' arrangement. Even when 
conducting power is equal, the currents of electricity, which as 
yet are the only indicators of this state, may be unequal, be- 
. cause of differences as to number, size, electrical condition,, &c. 
&c. in the particles themselves. It will only be after the laws 



Electrotonic state . 


21 


Nov. 1831.] 

which govern this new state are ascertained, that we shall be 
able to predict w£at is the true condition of, and what are the 
electrical results obtainable from, any particular substance. 

74. The current of electricity which induces the electro- 
tonic state in a neighbouring wire, probably induces that state 
also in fts own wire ; for when by a current in one wire a col- 
lateral wire is made electro-tonic, the latter state is not rendered 
any way incompatible or interfering with a current of electricity 
passing through it (62.) . If, therefore, the current were sent 
through the second wire instead of the first, it does not seem 
probable that its inducing action upon the second would be 
less, but on the contrary more, because the distance between 
the agent and the matter acted upon would be very greatly 
diminished. A copper ‘bolt had its extremities connected with 
a galvanometer, and then the poles of a battery of one hundred 
pairs of plates connected with the bolt, so as to send the cur- 
rent through it ; the voltaic circuit was then suddenly broken, 
and the galvanometer observed for any indications of a return 
current through the copper bolt due to the* discharge of its 
supposed electro-tonic state. No effect of the kind was ob- 
tained, nor indeed, for two reasons, ought it to be expected ; 
for first, as the cessation of induction and the discharge of the 
electro-tonic condition are simultaneous, and not successive, 
the return current would only be equivalent to the neutralization 
of the last portion of the inducing current, and w ould not there- 
fore show any alteration of direction ; or assuming that time 
did intervene, and that the latter current was really distinct 
from the former, its short, sudden -character (12. 26.) would 
prevent it from being thus recognized. 

75. No difficulty arises, I think, in considering the wire thus 
rendered electro-tonic by its own current more than by any 
external current, especially when the apparent non-interference 
of that state with currents is considered (62. 71.). The si- 
multaneous existence of the conducting and electro-tonic states 
finds an analogy in the manner in which electrical currents can be 
passed through magnets, where it is found that both the cur- 
rents passed, and those of the magnets, preserve all their proper- 
ties distinct from each other, and exert their mutual actions. 

7§. The reason given with regard to metals extends also to 
fluids and all other conductors, and leads to the conclusion 
that when electric currents are passed through them they also 



22 Electrotonic state. [Series I. 

assume the electro-tonic state. Should tha^ prove to be the 
case, its influence in voltaic decomposition, and the transference 
of the elements to the poles, can hardly be doubted. In the 
electro-tonic state the homogeneous particles of matter appear 
to have assumed a regular hut forced electrical arrangement 
in the direction of the current, which if the matter he unde- 
Composable, produces, when relieved, a return current ; but in 
decomposable matter this forced state may be sufficient to rn^ke 
an elementary particle leave its companion, with which it is in 
a constrained condition, and associate with the neighbouring 
similar particle, in relation to which it is in a more natural con- 
dition, the forced electrical arrangement being itself discharged 
or relieved, at the same time, as effectually as if it had been 
freed from induction. But as the original voltaic current is 
continued, the electro-tonic state may be instantly renewed,., 
producing the forced arrangement of the compound particles, 
to be as instantly discharged by a transference of the element- 
ary particles of the opposite kind in opposite directions, but 
parallel to the current. Even the differences between common 
and voltaic electricity, when applied to effect chemical decom- 
position, which Dr. Wollaston has pointed out*, seem expli- 
cable by the circumstances connected with the induction of 
electricity from these two sources (25.). But as I have reserved 
this branch of the inquiry, that I might follow out the investi- 
gations contained in the present paper, I refrain (though much 
tempted) from offering further speculations. 

77. Marianini has discovered and described a peculiar affec- 
tion of the surfaces of metallic discs, when, being in contact 
with humid conductors, a current of electricity is passed througli 
them ; they are then capable of producing a reverse current of 
electricity, and Marianini has well applied the effect in expla- 
nation of the phenomena of Ritter's piles f. M. A. de la Rive 
has described a peculiar property acquired by metallic con- 
ductors, when being immersed in a liquid as poles, they have 
completed, for some time, the voltaic circuit, in consequence 
of which, when separated from the battery and plunged into 
the same fluid, they by themselves produce an electric current J. 
M. A. Van Beek has detailed cases in which the electrical re- 
lation of one metal in contact with another has been preserved 

* Philosophical Transactions, 1801, p. 247. 

t Annales de Chimie, XXXVIII, 5. % Ibid. XXVIII. 190- 



23 


Nov. 1831.] Amp&re’s inductive results . 

after separation, and accompanied by its corresponding chemical 
effects *. These* states and results appear to differ from the 
electro-tonic state and its phenomena ; but the true relation 
of the former to the latter can only be decided when our know- 
ledge of all these phenomena has been enlarged. 

78. I liad occasion in the commencement of this paper (2.) 
to refer to an experiment by Ampere, as one of those depend- 
ent upon the electrical induction of currents made prior to 
th£ present investigation, and have arrived at conclusions which 
seem to imply doubts of the accuracy of the experiment (62. 
&c.) : it is therefore due to M. Ampere that I should attend 
to it more distinctly. When a disc of copper (says M. Ampere) 
was suspended by a silk thread and surrounded by a helix or 
spiral, and when the bharge of a powerful voltaic battery was 
sent through the spiral, a strong magnet at the same time being 
presented to the copper disc, the latter turned at the moment 
to take a position of equilibrium, exactly as the spiral itself 
would have turned had it been free to move. I have not been 
able to obtain this effect, nor indeed any motion ; but the cause 
of my failure in the latter point may be due to the momentary 
existence of the current not allowing time for the inertia of the 
plate to be overcome (11. 12.). M. Ampere has perhaps suc- 
ceeded in obtaining motion from the superior delicacy and 
power of his electro-magnetical apparatus, or he may have ob- 
tained only the motion due to cessation of action. But all my 
results tend to invert the sense of the proposition stated by M. 
Ampere, “ that a current of electricity tends to put the elec- 
tricity of conductors near which it passes in motion in the same 
direction,” for they indicate an opposite direction for the pro- 
duced current (26. 53.) ; and they show that the effect is mo- 
mentary, and that it is also produced by magnetic. induction, 
and that certain other extraordinary effects follow thereupon. 

79. The momentary existence xff the phenomena of induction 
now described is sufficient to furnish abundant reasons for the 
uncertainty or failure of the experiments, hitherto made to ob- 
tain electricity from magnets, or to effect chemical decomposi- 
tion or arrangement by their means f. 

« * Annales de Chirnie, XXXVIII. 49. 

1* The Lycde, No. 36, for January 1st, has a long and rather premature article, 
in which it endeavours to show anticipations by French philosophers of my re- 
searches. It however mistakes the erroneous results of MM. Fresnel and Am- 



24 Arago’ s magnetic phenomena. [Series I. 

80. It also appears capable of explaining fully the remarkable 
phenomena observed by M. Arago between metals and magnets 
when either are moving (120.), as well as most of the results 
obtained by Sir John Herschel, Messrs. Babbage, Harris, and 
others, in repeating his experiments ; accounting at the same 
time perfectly for what at first appeared inexplicable ; namely, 
the non-action of the same metals and magnets when, at rest. 
These results, which also afford the readiest means of obtaining 
electricity from magnetism, I shall now proceed to describe. 

§ 4. Explication of Arago? s Magnetic Phenomena. 

81. If a plate of copper be revolved close to a magnetic needle, 
or magnet, suspended in such a way that the latter may rotate 
in a plane parallel to that of the former, the magnet tends to 
follow the motion of the plate ; or if the magnet be revolved, 
the plate tends to follow its motion ; and the effect is so^power- 
ful, that magnets or plates of many pounds weight may be thus 
carried round. If the magnet and plate be at rest relative to 
each other, not the slightest effect, attractive or repulsive, or of 
any kind, can be observed between them (62.). This is the phe- 
nomenon discovered by M. Arago ; and he states that the effect 
takes place not only with all metals, but with solids, liquids, and 
even gases, i . e. with all substances (180.). 

82. Mr. Babbage and Sir John Herschel, on conjointly re- 
peating the experiments in this country *, could obtain the 
effects only with the metals, and with carbon in a peculiar state 
(from gas retorts), i. e. only with excellent conductors of elec- 
tricity. They refer the effect to magnetism induced in the plate 
by the magnet ; the pole of the latter causing an opposite pole 
in the nearest part of the plate, and round this a more diffuse 

pere for true ones, find then imagines my true results are like those erroneous 
ones. I notice it here, however, for the purpose of doing honour to Fresnel in 
a much higher degree than would have been merited by a feeble anticipation 
of the present investigations. That great philosopher, at the same time with 
myself and fifty other persons, made experiments which the present paper 
proves could give no expected result. lie was deceived for the moment, and 
published his imaginary success ; but on more carefully repeating his trials, 
he could find no proof of their accuracy ; and, in the high and pure philosophic 
desire to remove error us well as discover truth, he recanted his first statement. 
The example of Berzelius regarding the first Thorina is another instance of 
this fine feeling ; and as occasions are not rare, it would be to the dignity of 
science if such examples were more frequently followed. — February 10th, 1832. 

* Philosophical Transactions, 1.^25, p. 407. 



Their nature illustrated. 


25 


Nov. 1831.] 

polarity of its own kind (120.). The essential circumstance in 
producing the rotation of the suspended magnet is, that the 
substance revolving below it shall acquire and lose its mag- 
netism in sensible time, and not instantly (124.). This theory 
refers the effect to an attractive force, and is not agreed to by 
the discoverer, M. Arago, nor by M. Ampere, who quote against 
it the absence of all attraction when the magnet and metal are 
at rest (62. 12'!.), although the induced magnetism should still 
remain ; and who, from experiments made with a long dipping 
needle, conceive the action to be always repulsive (125.). 

83. Upon obtaining electricity from magnets by the means 
already described (36. 46.), I hoped to make the experiment 
of M. Arago a new source of electricity ; and did not despair, 
by reference to terrestrial magneto-electric induction, of being 
able to construct a new electrical machine. Thus stimulated, 
numerous experiments were made with the magnet of the Royal 
Society at Mr. Christie's house, in all ol* which I had the ad- 
vantage of his assistance. As many of these were in the course 
of the investigation superseded by more perfect arrangements, 
I shall consider myself at liberty to rearrange them in a manner 
calculated to convey most readily what appears to me to be a 
correct view of the nature of the phenomena. 

84. The magnet has been already described (44.). To con- 
centrate the poles, and bring them nearer to each other, two 
iron or steel bars, each about six or seven inches long, one inch 
wide, and half an inch thick, were put across the poles as in 
fig. 7, and being supported by twine from slipping, could be 
placed as near to or far from each other as was required. Oc- 
casionally two bars of soft iron were employed, so bent that 
when applied, one to each pole, the two smaller resulting poles 
were vertically over each other, either being uppermost at 
pleasure. 

85. A disc of copper, twelve inches in diameter, and about 
one fifth of an inch in thickness, fixed upon a brass axis, was 
mounted in frames so as to allow of revolution either vertically 
or horizontally, its edge being at the same time introduced moie 
or less between the magnetic poles (fig. 7). The edge of the 
plate was well amalgamated for the purpose of obtaining a good 
but moveable contact, and a part round the axis was also pre- 
pared in a similar manner. 



26 Arago’s magnetic phenomena . [Series I. 

86. Conductors or electric^ collectors of copper and lead were 
constructed so as to come in contact with the edge of the cop- 
per disc (85.), or with other forms of plates hereafter to be 
described (101.). These conductors were about four inches 
long, one third of an inch wide, and one fifth of an inch thick ; 
one end of each was slightly grooved, to allow of more exact 
adaptation to the somewhat convex edge of the plates, and then 
amalgamated. Copper wires, one sixteenth of an inch in thick- 
ness, attached, in the ordinary manner, by convolutions to tfie 
other ends of these conductors, passed away to the galvano- 
meter. 

87. The galvanometer was roughly made, yet sufficiently 
delicate in its indications. The wire was of copper covered 
with silk, and made sixteen or eighteen convolutions. Two 
sewing-needles were magnetized and fixed on to a stem, of dried ^ 
grass parallel to each other, hut in opposite directions, and 
about half an inch apart ; this system was suspended by a fibre 
of unspun silk, so that the lower needle should be between the 
convolutions of the multiplier, and the upper above them. 
The latter was by much the most powerful magnet, and gave 
terrestrial direction to the whole ; fig. 8 represents the di- 
rection of the wire and of the needles when the instrument was 
placed in the magnetic meridian : the ends of the wires are 
marked A and B for convenient reference hereafter. The let- 
ters S and N designate the south and north ends of the needle 
when affected merely by terrestrial magnetism ; the mid N is 
therefore the marked pole (44.) . The whole instrument was 
protected by a glass jar, and stood, as to position and distance 
relative to the large magnet, under the same circumstances as 
before (45.). 

88. All these arrangements being made, the copper disc was 
adjusted as in fig. 7, the small magnetic poles being about half 
an inch apart, and the edge of the plate inserted . about half 
their width between them. One of the galvanometer wires was 
passed twice or thrice loosely round the brass axis of the plate, 
and the other attached to a conductor (86.), which itself was 
retained by the hand in contact with the amalgamated edge of 
the disc at the part immediately between the magnetic poles. 
Under these circumstances all was quiescent, and the galva- 
nometer exhibited no effect. But the instant the plate moved. 



Nov. 1831.] Electricity from revolving copper plates. 27 

the galvanometer was influenced, and by revolving the plate 
quickly the neeclle could be deflected 90° or more. 

$9. It was difficult under the circumstances to make the 
contact between the conductor and the edge of the revolving 
disc uniformly good and extensive ; it was also difficult in 
the firsl experiments to obtain a regular velocity of rotation : 
both these causes tended to retain the needle in a continual 
state of vibration ; but no difficulty existed in ascertaining to 
which side it was deflected, or generally, about what line it vi- 
brated. Afterwards, when the experiments were made more 
carefully, a permanent deflection of the needle of nearly 45° 
could be sustained. 

90. Here therefore was demonstrated the production of a 
permanent current of electricity by ordinary magnets (57.). 

91. When the motion of the disc was reversed, every other 
circumstance remaining the same, the galvanometer needle was 
deflected with equal power as before ; but the deflection was 
on the opposite side, and the current of electricity evolved, 
therefore, the reverse of the former. 

92. When the conductor was placed on the edge of the disc 
a little to the right or left, as in the dotted positions fig. 9, the 
current of electricity was still evolved, and in the same direction 
as at first (88. 91.). This occurred to a considerable distance, 
i. e. 50° or 60° on each side of the place of the magnetic poles. 
The current gathered by the conductor and conveyed to the 
galvanometer was of the same kind on both sides of the place 
of greatest intensity, but gradually diminished in force from 
that place. It appeared to be equally powerful at equal di- 
stances from the place of the magnetic poles, not being affected 
in that respect by the direction of the rotation. When the ro- 
tation of the disc was reversed, the direction of the current of 
electricity was reversed also ; but the other circumstances were 
not affected. 

93. On raising the plate, so that the magnetic poles were 
entirely hidden from each other by its intervention, [a. fig. 10,) 
the same effects were produced in the same order, and with 
equal intensity as before. On raising it still higher, so as to 
bring the place of the poles to c , still the effects were pro- 
duced, and apparently with as much power as at first. 

94. When the conductor was held against the edge as if fixed 



28 Electricity from revolving copper plates. [Series I. 

to it, and with it moved between the poles, even though but 
for a few degrees, the galvanometer needle moved and indicated 
a current of electricity, the same as that which would have 
been produced if the wheel had revolved in the same direction, 
the conductor remaining stationary. 

95. When the galvanometer connexion with the axis was 
broken, and its wires made fast to two conductors, both. applied 
to the edge of the copper disc, then currents of electricity were 
produced, presenting more complicated appearances, but in 
perfect harmony with the above results. Thus, if applied as 
in fig. 11, a current of electricity through the galvanometer 
was produced ; but if their place was a little shifted, as in fig. 
12, a current in the contrary direction resulted; the fact being, 
that in the first instance the galvanometer indicated the differ- 
ence between a strong current through A and a weak one 
through B, and in the second, of a weak current through A 
and a strong one through B (92.), and therefore produced op- 
posite deflections. 

96. So also when the two conductors were equidistant from 
the magnetic poles, as in fig. 13, no current at the galvanometer 
was perceived, whichever way the disc was rotated, beyond 
what was momentarily produced by irregularity of contact ; 
because equal currents in the same direction tended to pass 
into both. But when the two conductors were connected with 
one wire, and the axis with the other wire, (fig. 11,) then the 
galvanometer showed a current according with the direction of 
rotation (91.) ; both conductors now acting consentaneously, 
and as a single conductor did before (88). 

97. All these effects could be obtained when only one of the 
poles of the magnet was brought near to the plate ; they were 
of the same kind as to direction, &c., but by no means so 
powerful. 

98. All care was taken to render these results independent 
of the earth's magnetism, or of the mutual magnetism of the 
magnet and galvanometer needles. The contacts were made 
in the magnetic equator of the plate, and at other parts ; the 
plate was placed horizontally, and the poles vertically 1 ; and 
other precautions were taken. But the absence of any inter- 
ference of the kind referred to, was readily shown by the want 
of all effect when the disc was removed from the poles, or the 



29 


Nov. 1831.] Direction of the electric current produced . 

poles from the disc ; every other circumstance remaining the 
same, 

99. The relation of the current of electricity produced, to 
the magnetic pole, to the direction of rotation of the plate, &c. 
&e., may be expressed by saying, that when the unmarked 
pole (44. 84.) is beneath the edge of the plate, and the latter 
revolves horizontally, screw-fashion, the electricity which can 
be collected at the edge of the plate nearest to the pole is po- 
sitive. As the pole of the earth may mentally be considered 
the unmarked pole, this relation of the rotation, the pole, and 
the electricity evolved, is not difficult to remember. Or if, in 
fig. 15, the circle represent the copper disc revolving in the 
direction of the arrows, and a the outline of the unmarked 
pole placed beneath the plate, then the electricity collected at 
h and the neighbouring parts is positive, whilst that collected 
at tlie # centre c and other parts is negative (88.) . The currents 
in the plate are therefore from the centre by the magnetic 
poles towards the circumference. 

100. If the marked pole be placed above, all other things 
remaining the same, the electricity at h> fig. 15, is still positive. 
If the marked pole be placed below, or the unmarked pole 
above, the electricity is reversed. If the direction of revolu- 
tion in any case is reversed, the electricity is also reversed. 

101. It is now evident that the rotating plate is merely 
another form of the simpler experiment of passing a piece of 
metal between the magnetic poles in a rectilinear direction, and 
that in such cases currents of electricity arc produced at right 
angles to the direction of the motion, and crossing it at the 
place of the magnetic pole or poles. This was sufficiently 
shown by the following simple experiment : A piece of copper 
plate one-fifth of an inch thick, one inch and a half wide, and 
twelve inches long, being amalgamated at the edges, was 
placed between the magnetic poles, whilst the two conductors 
from the galvanometer were held in contact with its edges ; it 
was then drawn through between the poles of the conductors 
in the direction of the arrow, fig. 16 ; immediately the galvano- 
meter needle was deflected, its north or marked end passed 
eastward, indicating that the wire A received negative and the 
wire B positive electricity ; and as the marked pole was above, 



30 Electricity from moving conductors, [Series I. 

the result is in perfect accordance with the effect obtained by 
the rotatory plate (99.) . 

102. On reversing the motion of the plate, the needle at the 
galvanometer was deflected in the opposite direction, showing 
an opposite current. 

103. To render evident the character of the electribal cur- 
rent existing in various parts of the moving copper plate, dif- 
fering in their ^relation to the inducing poles, one collector 
(86.) only was applied at the part to be examined near to the 
pole, the other being connected with the end of the plate as 
the most neutral place : the results are given at figs. 17 — 20, 
the marked pole being above the plate. In fig. 17, B received 
positive electricity ; but the plate moving in the same direction, 
it received on the opposite side, fig. 18, f negative electricity ; 
reversing the motion of the latter, as in fig. 20, B received^ 
positive electricity ; or reversing the motion of the first ar- 
rangement, that of fig. 17 to fig. 19, B received negative elec- 
tricity. 

104. When the plates were previously removed sideways 
from between the magnets, as in fig. 21, so as to be quite out 
of the polar axis, still the same effects were produced, though 
not so strongly. 

105. When the magnetic poles were in contact, and the 
copper plate was drawn between the conductors near to the 
place, there was but very little effect produced. When the 
poles were opened by the width of a card, the effect was some- 
what more, but still very small. 

106. When an amalgamated copper wire, one eighth of an 
inch thick, was drawn through between the conductors and 
poles (101.), it produced a very considerable effect, though not 
so much as the plates. 

107. If the conductors were held permanently against any 
particular parts of the copper plates, and carried between the 
magnetic poles with them, effects the same as those described 
were produced, in accordance with the results obtained with 
the revolving disc (94.). 

108. On the conductors being held against the ends of the 
plates, and the latter then passed between the magnetic poles, 
in a direction transverse to their length) the same effects were 



31 


Nov. 1831.] Electricity from moving conductors . 

produced (fig. 22.). The parts of the plates towards the end 
may be considered either as mere conductors, or as portions of 
metal in which the electrical current is excited, according to 
their distance and the strength of the magnet ; but the results 
were in perfect harmony with those before obtained. The ef- 
fect waS as strong as when the conductors were held against 
the sides of the plate (101.). 

109. When a mere wire, connected with the galvanometer 
so* as to form a complete circuit, was passed through between 
the poles, the galvanometer was affected ; and upon moving 
the wire to and fro, so as to make the alternate impulses pro- 
duced correspond with the vibrations of the needle, the latter 
could be increased to 20° or 30° on each side the magnetic 
meridian. 

110. Upon connecting the ends of a plate of metal with the 
gal variometer wires, and then carrying it* between the poles 
from end to end (as in fig. 23.), in either direction, no effect 
whatever was produced upon the galvanometer. But the mo- 
ment the motion became transverse, the needle was deflected. 

111. These effects were also obtained from electro-magnetic 
poles , resulting from the use of copper helices or spirals, either 
alone or with iron cores (34. 54.). The directions of the mo- 
tions were precisely the same ; but the action was much greater 
when the iron cores were used, than without. 

112. When a flat spiral was passed through edgewise be- 
tween the poles, a curious action of the galvanometer resulted ; 
the needle first went strongly one way, but then suddenly 
stopped, as if it struck against some solid obstacle, and imme- 
diately returned. If the spiral were passed through from 
above downwards, or from below upwards, still the motion of 
the needle was in the same direction, then suddenly stopped, 
and then was reversed. But on turning the spiral" half-way 
round, i. e. edge for edge, then the directions of the motions 
were reversed, but still were suddenly interrupted and inverted 
as before. This double action depends upon the halves of the 
spiral (divided by a line passing through its centre perpendi- 
cular to the direction of its motion) acting in opposite directions ; 
and the reason why the needle went to the same side, whether 
the spiral passed by the poles in the one or the other direction, 
was the circumstance, that upon changing the motion, the di- 



32 Law of magneto-electric induction . [Series I. 

rection of the wires in the approaching half of the spiral was 
changed also. The effects, curious as they appear when wit- 
nessed, are immediately referable to the action of single wires 
(40. 109.). 

113. Although the experiments with the revolving plate, 
wires, and plates of metal, were first successfully made with 
the large magnet belonging to the Royal Society, yet they 
were all ultimately repeated with a couple of bar magnets two 
feet long, one inch and a half wide, and half an inch thick ; 
and, by rendering the galvanometer (87.) a little more delicate, 
with the most striking results. Ferro -electro-magnets, as those 
of Moll, Henry, &c. (57.), are very powerful. It is very essen- 
tial, when making experiments on different substances, that 
thermo-electric effects (produced by contact of the fingers, &c.) 
be avoided, or at least appreciated and accounted for ; they 
are easily distinguished by their permanency, and their inde-" 
pendence of the magnets, or of the direction of the motion. 

114. The relation which holds between the magnetic pole, 
the moving wire or metal, and the direction of the current 
evolved, i . e. the law which governs the evolution of electricity 
by magneto-electric induction, is very simple, although l’ather 
difficult to express. If in fig. 21. PN represent a horizontal 
wire passing by a marked magnetic pole, so that the direction 
of its motion shall coincide with the curved line proceeding 
from below upwards ; or if its motion parallel to itself be in a 
line tangential to the curved line, but in the general direction 
of the arrows ; or if it pass the pole in other directions, but so 
as to cut the magnetic curves * in the same general direction, 
or on the same side as they would be cut by the wire if moving 
along the dotted curved line ; — then the current of electricity 
in the wire is from P to N. If it be carried in the reverse di- 
rections, the electric current will be from N to P. Or if the 
wire be in the vertical position, figured P' N', and it be carried 
in similar directions, coinciding with the dotted horizontal 
curve so far, as to cut the magnetic curves on the same side 
with it, the current will he from P 1 to N f . If the wire he con- 
sidered a tangent to the curved surface of the cylindrical mag- 

* By magnetic curves I mean the lines of magnetic forces, however modi- 
fied b^the juxtaposition of poles, which would he depicted by iron filings ; or 
those to which a very small magnetic needle would form a tangent. 



33 


Nov. 1831.] Direction of the magneto-electric current . 

let, and it be carried round that surface into any other posi- 
;ion, or if the magnet itself be revolved on its axis, so as to 
3 ring any part opposite to the tangential wire, — still, if after- 
yards the wire be moved in the directions indicated, the cur- 
rent of electricity will be from P to N; or if it be moved in the 
? opposite* direction, from N to P; so that as regards the mo- 
tions of. the wire past the pole, they may be reduced to two, 
directly opposite to each other, one of which produces a cur- 
rent from P to N, and the other from N to P. 

115. The same holds true of the unmarked pole of the mag- 
net, except that if it be substituted for the one in the figure, 
then, as the wires are moved in the direction of the arrows, the 
current of electricity would be from N to P, and when they 
move in the reverse direction, from P to N. 

116. Hence the current of electricity which is excited in 
metal when moving in the neighbourhood of a magnet, depends 
for its direction altogether upon the relation of the metal to the 
resultant of magnetic action, or to the magnetic curves, and 
may be expressed in a popular way thus : Let A B (fig. 25.) 
represent a cylinder magnet, A being the marked pole, and B 
the unmarked pole; let P N he a silver knife-blade resting 
across the magnet with its edge upward, and with its marked 
or notched side towards the pole A ; then in whatever direction 
or position this knife be moved edge foremost, either about 
the marked or the unmarked pole, the current of electricity 
produced will be from P to N, provided the intersected curves 
proceeding from A abut upon the notched surface of the knife, 
and those from B upon the unnotclied side. Or if the knife 
be moved with its back foremost, the current will be from N 
to P in every possible position and direction, provided the in- 
tersected curves abut on the same surfaces as before. , A little 
model is easily constructed, by using a cylinder of wood for a 
magnet, a flat piece for the blade, and a piece of thread con- 
necting one end of the cylinder with the other, and passing 
through a hole in the blade, for the magnetic curves : this 
readily gives the result of any possible direction. 

117. When the wire under induction is passing by an electro- 
magnetic pole, as for instance one end of a copper helix tra- 
versed by the electric current (34.), the direction of the current 
in the approaching wire is the same with that of the current 



34 Explication of Ar ago’ s magnetic phenomena. [Series L 

in the parts or sides of the spirals nearest to it, and in the re- 
ceding wire the reverse of that in the parts nearest to it. 

118. All these results show that the power of inducing 
electric currents is circumferentially exerted by a magnetic 
resultant or axis of power, just as circumferential magnetism 
is dependent upon and is exhibited by an electric current. 

119. The experiments described combine to prove that when 
a piece of metal (and the same may be true of all conducting 
matter (213.) ) is passed either before a single pole, or between 
the opposite poles of a magnet, or near electro-magnetic poles, 
whether ferruginous or not, electrical currents are produced 
across the metal transverse to the direction of motion ; and 
which therefore, in Aragons experiments, will approximate 
towards the direction of radii. If a single wire be moved like 
the spoke of a wheel near a magnetic pole, a current of elec- 
tricity is determined through it from one end towards the 
other. If a wheel be imagined, constructed of a great num- 
ber of these radii, and this revolved near the pole, in the 
manner of the copper disc (85.), each radius will have a cur- 
rent produced in it as it passes by the pole. If the radii 
be supposed to be in contact laterally, a copper disc results, 
in which the directions of the currents will be generally the 
same, being modified only by the coaction which can take 
place between the particles, now that they arc in metal- 
lic contact. 

120. Now that the existence of these currents is known, 
Aragons phenomena may be accounted for without considering 
them as due to the formation in the copper of a pole of the 
opposite kind to that approximated, surrounded by a diffuse 
polarity of the same kind (82.) ; neither is it essential that the 
plate should acquire and lose its state in a finite time ; nor on 
the other hand does it seem necessary that any repulsive force 

hould be admitted as the cause of the rotation (82.) . 

121. The effect is precisely of the same kind as the electro- 
magnetic rotations which I had the good fortune to discover 
some years ago*. According to the experiments then made, 
which have since been abundantly confirmed, if a wire (P N 
fig. 26«) be connected with the positive and negative ends of a 
voltaic battery, so that the positive electricity shall pass from 

* Quarterly Journal of Science, vol. xii. pp. 74, 180, 416, 283? 



Nov. 1831.] Influence of time on the effects. 35 

P to N, and a piarked magnetic pole N be placed near the 

wire between it and the spectator, the pole will move in a di- 

rection tangential to the wire, i. e. towards the right, and the 
wire Will move tangentially towards the left, according to the 
directions of the' arrows. This is exactly what takes place in 
the rotation of a plate beneath a magnetic pole ; for let N (fig. 
27.) be fl marked pole above the circular plate, the latter being 
rotated in the direction of the arrow : immediately currents of 
positive electricity set from the central parts in the general di- 
rection of the radii by the pole to the parts of the circum- 
ference a on the other side of that pole (99. 119.), and are 

therefore exactly in the same relation to it as the current in 
the wire (P N, fig. 2 t (>), and therefore the pole in the same 
manner moves to the right hand. 

122. If the rotation of the disc be reversed, the electric cur- 
rents are reversed (91.), and the pole therefore moves to the 
left hand. If the contrary pole be employed, the effects are 
the same, i. e . in the same direction, because currents of elec- 
tricity, the reverse of those described, are produced, and by 
reversing both poles and currents, the visible effects remain 
unchanged. In whatever position the axis of the magnet be 
placed, provided the same pole be applied to the same side 
of the plate, the electric current produced is in the same di- 
rection, in consistency with the law already stated (114, &c.) ; 
and thus every circumstance regarding the direction of the mo- 
tion may be explained. 

123. These currents are discharged or return in the parts 
of the plate on each side of and more distant from the place of 
the pole, where, of course, the magnetic induction is weaker : 
and when the collectors are applied, and a current of electricity 
is carried away to the galvanometer (88.), the deflection there 
is merely a repetition, by the same current or part of it, of the 
effect of rotation in the magnet over the plate itself. 

124. It is under the point of view just put forth that I have 
ventured to say it is not necessary that the plate should ac- 
quire and lose its state in a finite time (120.) ; for if it; were 
possible for the current to be fully developed the instant before 
it arrived at its state of nearest approximation to the vertical 
pole of the magnet, instead of opposite to or a little beyond* 
it, still the relative motion of the pole and plate would be the 

d 2 



36 Explication of Ar ago' s magnetic phenomena. [Series I. 

same, the resulting force being in fact tangential instead of 
direct. 

125. But it is possible (though not necessary for the rotation^ 
that time may be required for the development of the maxi- 
mum current in the plate, in which case the resultant of all the 
forces would be in advance of the magnet when the plate is 
rotated, or in the rear of the magnet when the latter is -rotated, 
and many of the effects with pure electro -magnetic poles tepd 
to prove this is the case. Tlaen, the tangential force may be 
resolved into two others, one parallel to the plane of rotation, 
and the other perpendicular to it : the former would be the 
force exerted in making the plate revolve with the magnet, or 
the magnet with the plate ; the latter would be a repulsive 
force, and is probably that, the effects of which M. Arago has 
also discovered (82.) . 

126. The extraordinary circumstance accompanying this ac- 
tion which has seemed so inexplicable, namely, the cessation 
of all phenomena when the magnet and metal are brought to 
rest, now receives a full explanation (82.) ; for then the elec- 
trical currents which cause the motion cease altogether. 

127. All the effects of solution of metallic continuity, and 
the consequent diminution of power described by Messrs. Bab- 
bage and Herschel*, now receive their natural explanation, as 
well also as the resumption of power when the cuts were filled 
up by metallic substances, which, though conductors of elec- 
tricity, were themselves very deficient in the power of influen- 
cing magnets. And new modes of cutting the plate may be de- 
vised, which shall almost entirely destroy its power. Thus, if 
a copper plate (81.) be cut through at about a fifth or sixth of 
its diameter from the edge, so as to separate a ring from it, 
and this ring be again fastened on, but with a thickness of 
paper intervening (fig. 29), and if Arago's experiment be made 
with this compound plate so adjusted that the section shall 
continually travel opposite the pole, it is evident that the 
magnetic currents will be greatly interfered with, and the plate 
probably lose much of its effect f. 

* Philosophical Transactions, 1825, p. 481. 

t This experiment has actually been made by Mr. Christie, with the results 
Here described, and is recorded in the Philosophical Transactions for 1827 , 

p. 82 . 



37 


Nov. 1831.] Bodies in which they occur . 

An elemental^ result of this kind was obtained by using two 
pieces of thick copper, shaped as in fig. 28. When the two 
neighbouring edges were amalgamated and put together, and 
the arrangement passed between the poles of the magnet, in a 
direction parallel to these edges, a current was urged through 
the wires attached to the outer angles, and the galvanometer 
became* strongly affected; but when a single film of paper was 
interposed, and the experiment repeated, no sensible effect 
could be produced. 

128. A section of this kind could not interfere much with 
the induction of magnetism, supposed to be of the nature ordi- 
narily received by iron. 

129. The effect of rotation or deflection of the needle, which 
M. Arago obtained by ordinary magnets, M. Ampere succeeded 
in procuring by electro-magnets. This is perfectly in harmony 
with the results relative to volta-electrie and magneto-electric 
induction described in this paper. And by using flat spirals 
of copper wire, through which electric currents were sent, in 
place of ordinary magnetic poles (HI.), sometimes applying a 
single one to one side of the rotating plate, and sometimes two 
to opposite sides, I obtained the induced currents of electricity 
from the plate itself, and could lead them away to, and ascer- 
tain their existence by, the galvanometer. 

130. The cause which has now been assigned for the rota- 
tion in Arago’s experiment, namely, the production of electri- 
cal currents, seems abundantly sufficient in all cases where the 
metals, or perhaps even other conductors, are concerned ; but 
with regard to such bodies as glass, resins, and, above all, 
gases, it seems impossible that currents of electricity, capable 
of producing these effects, should be generated in them. Yet 
Arago found that the effects in question were produced by 
these and by all bodies tried (81.). Messrs. Babbage and 
Herschel, it is true, did not observe them with any substance 
not metallic, except carbon, in a highly conducting state (82.). 
Mr. Harris has ascertained their occurrence with wood, marble, 
freestone and annealed glass, but obtained no effect with sul- 
phuric acid and saturated solution of sulphate of iron, although 
these are better conductors of electricity than the former sub- 
stances. 

131. Future investigations will no doubt explain these diffi- 



38 Abundance of the magneto-electric current. [Series I. 

culties, and decide the point whether the retarding or dragging 
action spoken of is always simultaneous with electric currents*. 
The existence*^ the action in metals, only whilst the currents 
exist, i. e. whilst motion is given (82. 88.), and the explication 
of tlip repulsive action observed by M. Arago (82. 125.), are 
powerful reasons for referring it to this cause ; but it may be 
combined with others which occasionally act alone. 

132. Copper, iron, tin, zinc, lead, mercury, and all the metals 
tried, produced electrical currents when passed between the 
magnetic poles : the mercury was put into a glass tube for the 
purpose. The dense carbon deposited in coal gas retorts, also 
produced the current, but ordinary charcoal did not. Neither 
could I obtain any sensible effects with brine, sulphuric acid, 
saline solutions, &c., whether rotated in basins, or inclosed in 
tubes and passed between the poles. 

133. I have never been able to produce any sensation upon 
the tongue by the wires connected with the conductors applied 
to the edges of the revolving plate (88.) or slips of metal (101.). 
Nor have I been able to heat a fine platina wire, or produce 
a spark, or convulse the limbs of a frog. I have failed also 
to produce any chemical effects by electricity thus evolved 
(22.56.). 

134. As the electric current in the revolving copper plate 
occupies but a small space, proceeding by the poles and being 
discharged right and left at very small distances comparatively 
(123.) ; and as it exists in a thick mass of metal possessing al- 
most the highest conducting power of any, and consequently 
offering extraordinary facility for its production and discharge ; 
and as, notwithstanding this, considerable currents may be 
drawn off which can pass through narrow wires, forty, fifty, 
sixty, or even one hundred feet long ; it is evident that the 
current existing in the plate itself must be a very powerful one, 
when the rotation is rapid and the magnet strong. This is 
also abundantly proved by the obedience and readiness with 
which a magnet ten or twelvp pounds in weight follows the 

* Experiments which X have since made convince me that this particular 
action is always due to the electrical currents formed ; and they supply a 
test by which it may be distinguished from the action of ordinary magnetism, 
or any other cause, including those which are mechanical or irregular, pro- 
ducing similar effects (254.). 



Nov. 1831.] Magneto-electric machines. 39 

motion of the plate and will strongly twist up the cord by which 
it is suspended. 

135. Two rough trials were made with the intention of con- 
structing magneto-electric machines . In one, a ring one inch 
and a half broad and twelve inches external diameter, cut 
from a thick copper plate, was mounted so as to revolve between 
the poles of the magnet and represent a plate similar to those 
formerly used (101.), but of interminable length ; the inner and 
outer edges were amalgamated, and the conductors applied, 
one to each edge, at the place of the magnetic poles. The 
current of electricity evolved did not appear by the galvano- 
meter to be stronger, if so strong, as that from the circular 
plate (88.). 

136. In the other, s*mall thick discs of copper or other metal, 
half an inch in diameter, were revolved rapidly near to the 
poles, but with the axis of rotation out of the polar axis ; the 
electricity evolved was collected by conductors applied as be- 
fore to the edges (86.). Currents were procured, but of 
sti*ength much inferior to that produced by the circular plate. 

137. The latter experiment is analogous to those made by t 
Mr. Barlow with a rotating iron shell, subject to the influence 
of the earth*. The effects obtained by him have been referred 
by Messrs. Babbage and Herschel to the same cause as that 
considered as influential in Aragons experiment t ; but it would 
be interesting to know how far the electric current which might 
be produced in the experiment would account for the deflexion 
of the needle. The mere inversion of a copper wire six or 
seven times near the poles of the magnet, and isochronously 
with the vibrations of the galvanometer needle connected with 
it, was sufficient to make the needle vibrate through an arc of 
60° or 70°. The rotation of a copper shell would perhaps de- 
cide the point, and might even throw light upon the more per- 
manent, though somewhat analogous effects obtained by Mr. 
Christie. 

138. The remark which has already been made respecting 
iron (66.), and the independence of the ordinary magnetical 
phenomena of that substance, and the phenomena now de- 
scribed of magneto-electric induction in that and other metals, 
was fully confirmed by many results of the kind detailed in this 

* Philosophical Transactions, 1825, p, 317. f Ibid, 1825, p, 485. 



40 Magneto-electric induction in different metals. [Series I. 

section. When an iron plate similar to the copper one formerly 
described (101.) was passed between the iffagnetic poles, it 
gave a current of electricity like the copper plate, but de- 
cidedly of less power; and in the experiments upon the in- 
duction of electric currents (9.), no difference in the kind of 

action between iron and other metals could he perceived. The 
power therefore of an iron plate to drag a magnet after it, or 
to intercept magnetic action, should be carefully distinguished 
from the similar power of such metals as silver, copper, &c. 

, &c., inasmuch as in the iron by far the greater part of the ef- 
fect is due to what may be called ordinary magnetic action. 

There can be no doubt that the cause assigned by Messrs. 

Babbage and Ilerschcl in explication of Aragons phenomena is 
the true one, when iron is the metal used*. 

139. The very feeble powers which were found by those 
philosophers to belong to bismuth and antimony, when moving, 
of affecting the suspended magnet, and which has been con- 
firmed by Mr. Harris, seem at first disproportionate to their 
conducting powers ; whether it be so or not must be decided 
by future experiment (73.)*. These metals are highly cry- 
stalline, and probably conduct electricity with different degrees 
of facility in different directions ; and it is not unlikely that 
where a mass is made up of a number of crystals heterogene- 
ously associated, an effect approaching to that of actual divi- 
sion may occur (127.) ; or the currents of electricity may be- 
come more suddenly deflected at the confines of similar cry- 
stalline arrangements, and so be more readily and completely 
discharged within the mass. 

* I have since been able to explain these differences, and prove, with several 
metals, that the effect is in the order of the conducting power ; for I have 
been able to obtain, by magneto -electric induction, currents of electricity 
which are proportionate in strength to the conducting power of the bodies 
experimented with (211.). 

Royal Institution, November 1831. 


Note . — In consequence of the long period which has intervened between the 
reading and printing of the foregoing paper, accounts of the experiments have 
been dispersed, and, through a letter of my own to M. Hachette, have reached 
France and Italy. That letter was translated (with some errors), and read to 
the Academy of Sciences at Paris, 26th December, 1881. A copy of it in Le 
Temps of the 28th December quickly reached Signor Nobili, who, with Signor 



41 


Nov. 1831.] Corrective chronological note. 

Antinori, immediately experimented upon the subject, and obtained many of 
the results mention^! in my letter; others they could not obtain or understand, 
because of the brevity of my account. These results by Signori Nobili and An- 
tinori have been embodied in a paper dated 31st January 1-632, and printed 
and published in the number of the Antologia dated November 1831, (accord- 
ing at least to the copy of the paper kindly sent me by Signor Nobili). It is 
evident tTiewoik could not have been then printed; and though Signor Nobili, in 
his paper, has inserted my letter as the text of his experiments, yet the circum- 
stance of back date has caused many here who have heard of Nobili’s experi- 
mtnts by report only, to imagine his results were anterior to, instead of being 
dependent upon, mine. 

I maybe allowed under these circumstances to remark, that I experimented 
on this subject several years ago, and have published results. (See Quarterly 
Journal of Science for July 1825, p. 338.) The following also is an extract 
from my note-book, dated November 28, 1825: “ Expeiimenta on induction 
by connecting wire of voltaic battery : — a battery of four troughs, ten pairs of 
plates, each arranged side by side — the poles connected by a wire about four 
feet long, parallel to which Avas another similar wire sepaiftted from it only by 
twothicknessesof paper, the ends of the latter were attached to n galvanometer: 
— exhibited no action, &c. &c. &c.—- Could not in any way render any induction 
evident from the connecting wire.” The calico of failure at that time is now 
evident (79). — M. F., April 1832, 



42 


SECOND SERIES. 

THE BAKERIAN LECTURE. 

§ 5. Terrestrial Magneto-electric Induction. § 6. Force an$ 
Direction of Magneto-electric Induction generally. 

Read January 12, 1832. 

§ 5. Terrestrial Magneto -electric Induction. 

140. When the general facts described* in the former paper 
were discovered, and the law of magneto-electric induction re-, 
lative to direction was ascertained (114.), it was not difficult to 
perceive that the earth would produce the same effect as a 
magnet, and to an extent that would, perhaps, render it avail- 
able in the construction of new electrical machines. The follow- 
ing are some of the results obtained in pursuance of this view. 

141. The hollow helix already described (6.) was connected 
with a galvanometer by wires eight feet long; and the soft 
iron cylinder (34.) after being heated red hot and slowly cooled, 
to remove ail traces of magnetism, was put into the helix so as 
to project equally at both ends, and fixed there. The combined 
helix and bar were held in the magnetic direction or line of 
dip, and (the galvanometer needle being motionless) were then 
inverted, so that the lower end should become the upper, but 
the whole still correspond to the magnetic direction ; the needle 
was immediately deflected. As the latter returned to its first 
position, the helix and bar were again inverted ; and by doing 
this two or three times, making the inversions and vibrations 
to coincide, the needle swung through an arc of 150° or 160°. 

142. When one end of the helix, which may be called A* 
was uppermost at first (B end consequently being belbw), then 
it mattered not in which direction it proceeded during the in- 
version, whether to the right hand or left hand, or through any 
other course ; still the galvanometer needle passed in the same 
direction. Again, when B end was uppermost, the inversion 
of the helix and bar in any direction always caused the needle 



Jan. 1832.] Terrestrial magneto-electric induction • 43 

to be deflected one way ; that way being the opposite to the 
course of the deflection in the former ease. 

143. When the helix with its iron core in any given position 
was inverted, the effect was as if a magnet with its marked pole 
downwards had been introduced from above into the inverted 
helix. Thus, if the end B were upwards, such a magnet in- 
troduced-from above would make the marked end of the galva- 
nometer needle pass west. Or the end B being downwards, 
and the soft iron in its place, inversion of the whole produced 
the same effect. 

144. When the soft iron bar was taken out of the helix and 
inverted in various directions within four feet of the galvano- 
meter, not the slightest effect upon it was produced. 

145. These phenomena are the necessary consequence of 
the inductive magnetic power of the earth, rendering the soft 
iron cylinder a magnet with its marked pole downwards. The 
experiment is analogous to that in which two bar magnets were 
used to magnetize the same cylinder in the same helix (3(h), 
and the inversion of position in the present experiment is equi- 
valent to a change of the poles in that arrangement. But the 
result is not less an instance of the evolution of electricity by 
means of the magnetism of the globe. 

116. The helix alone was then liekl permanently in the mag- 
netic direction, and the soft iron cylinder afterwards intro- 
duced ; the galvanometer needle was instantly deflected ; by 
withdrawing the cylinder as the needle* returned, and con- 
tinuing the two actions simultaneously, the vibrations soon ex- 
tended through an arc of 180°. The effect was precisely the same 
as that obtained by using a cylinder magnet with its marked pole 
downwards ; and the direction of motion, &c. was perfectly in 
accordance with the results of former experiments obtained 
with such a magnet (39.). A magnet in that position* being 
used, gave the same deflection, but stronger. When the helix 
was put at right angles to the magnetic direction or dip, then 
the introduction or removal of the soft iron cylinder produced 
no effect at the needle. Any inclination to the dip gave results 
of the same kind as those already described, but increasing in 
strength as the helix approximated to the direction of the dip. 

147. A cylinder magnet, although it has great power of 
affecting the galvanometer when moving into or out of the helix, 



44 Direct magneto -electric induction of the earth . [Series II. 

has no power of continuing the deflection (39*) ; and therefore, 
though left in, still the magnetic needle comes to its usual place 
of rest. But upon repeating (with the magnet) the experiment 
of inversion in the direction of the dip (141.), the needle was 
affected as powerfully as before ; the disturbance of the mag- 
netism in the steel magnet, by the earth's inductive force upon 
it, being thus shown to be nearly, if not quite, equal in amount 
and rapidity to that occurring in soft iron. It is probable that 
in this way magneto-electrical arrangements may become very 
useful in indicating the disturbance of magnetic forces, where 
other means will not apply ; for it is not the whole magnetic 
power which produce the visible effect, but only the difference 
due to the disturbing causes. 

148. These favourable results led me to hope that the direct 
magneto-electric induction of the earth might be rendered 
sensible ; and I ultimately succeeded in obtaining the effect in 
several ways. When the helix just referred to (141. 6.) was 
placed in the magnetic dip, but without any cylinder of iron or 
steel, and was then inverted, a feeble action at the needle was 
observed. Inverting the helix ten or twelve times, and at such 
periods that the deflecting forces exerted by the currents of elec- 
tricity produced in it should be added to the momentum of the 
needle (39.), the latter was soon made to vibrate through an 
arc of 80° or 90°. Here, therefore, currents of electricity were 
produced by the direct inductive power of the earth's magnet- 
ism, without the use of any ferruginous matter, and upon a 
metal not capable of exhibiting any of the ordinary magnetic 
phenomena. The experiment in everything represents the ef- 
fects produced by bringing the same helix to one or both poles 
of any powerful magnet (50.). 

149. Guided by the law already expressed (114.), I expected 
that all the electric phenomena of the revolving metal plate 
could now be produced without any other magnet than the 
earth. The plate so often referred to (85.) was therefore 
fixed so as to rotate in a horizontal plane. The magnetic 
curves of the earth (114. note) y i. e. the dip, passes though 
this plane at angles of about 70°, which it was expected would 
be an approximation to perpendicularity, quite enough to allow 
of magneto-electric induction sufficiently powerful to produce 
a current of electricity. 



Jan. 1832.] The revolving plate, a new electrical machine. 45 

150. Upon rotation of the plate, the currents ought, accord- 
ing to the law (ll4. 121.), to tend to pass in the direction of 
the radii, through all parts of the plate, either from the centre 
to the circumference, or from the circumference to the centre, 
as the direction of the rotation of the plate was one way or the 
other. One of the wires of the galvanometer was therefore 
brought in contact with the axis of the plate, and the other at- 
tached to a leaden collector or conductor (86.) , which itself was 
placed against the amalgamated edge of the disc. On rotating 
the plate there was a distinct effect at the galvanometer needle ; 
on reversing the rotation, the needle went in the opposite di- 
rection ; and by making the action of the plate coincide with 
the vibrations of the needle, the arc through which the latter 
passed soon extended to half a circle. 

151. Whatever part of the edge of the plate was touched by 
the conductor, the electricity was the same, provided the di- 
rection of rotation continued unaltered. 

152. When the plate revolved screw -fashion, or as the hands 
of a watch, the current of electricity (150.) was from the centre 
to the circumference ; when the direction of rotation was 
screw , the current was from the circumference to the centre. 
These directions are the same with those obtained when the 
unmarked pole of a magnet was placed beneath the revolving 
plate (99.). 

153. When the plate was in the magnetic meridian, or in any 
other plane coinciding with the magnetic dip, then its rotation 
produced no effect upon the galvanometer. When inclined to 
the dip but a few degrees, electricity began to appear upon 
rotation. Thus when standing upright in a plane perpendicu- 
lar to the magnetic meridian, and when consequently its own 
plane was inclined only about 20° to the dip, revolution of the 
plate evolved electricity. As the inclination was increased, the 
electricity became more powerful until the angle formed by 
the plane of the plate with the dip was 90°, when the electri- 
city for a given velocity of the plate was a maximum. 

154. It is a striking thing to observe the revolving copper 
plate become thus a new electrical machine ; and curious results 
arise on comparing it with the common machine. In the one, 
the plate is of the best non-conducting substance that can be ap- 
plied ; in the other, it is the most perfect conductor : in the one, 



46 Strength of the current , magneto -electric machines. [Series II. 

insulation is essential ; in the other it is fatal. # In comparison of 
the quantities of electricity produced, the metal machine does 
not at all fall below the glass one ; for it can produce a constant 
current capable of deflecting the galvanometer needle, whereas 
the latter cannot. It is quite true that the force of the current 
thus evolved has not as yet been increased so as to render it 
available in any of our ordinary applications of this power ; but 
there appears every reasonable expectation that this may here- 
after be effected ; and probably by several arrangements. 
Weak as the current may seem to be, it is as strong as, if not 
stronger than, any thermo-electric current ; for it can pass 
fluids (23.), agitate the animal system, and in the case of an 
electro-magnet has produced sparks (32.) . 

155. A disc of copper, one fifth of an* inch thick and only 
one inch and a half in diameter, was amalgamated at the edge ; 
a square piece of sheet lead (copper would have been better) 
of equal thickness had a circular hole cut in it, into which the 
disc loosely fitted ; a little mercury completed the metallic com- 
munication of the disc and its surrounding ring ; the latter was 
attached to one of the galvanometer wires, and the other wire 
dipped into a little metallic cup containing mercury, fixed upon 
the top of the copper axis of the small disc. Upon rotating 
the disc, in a horizontal plane, the galvanometer needle could 
be affected, although the earth was the only magnet employed, 
and the radius of the disc but three quarters of an inch ; in 
w r hich space only the current was excited. 

1 56. On putting the pole of a magnet under the revolving 
disc, the galvanometer needle could be permanently deflected. 

, 157. On using copper wires one sixth of an inch in thickness 
instead of the smaller wires (86.) hitherto constantly employed, 
far more powerful effects were obtained. Perhaps if the gal- 
vanometer had consisted of fewer turns of thick wire instead 
of many convolutions of thinner, more striking effects would 
have been produced. 

158. One form of apparatus which I purpose having ar- 
ranged, is to have several discs superposed; the discs are to 
be metallically connected, alternately at the edges and at the 
centres, by means of mercury; and are then to be revolved 
alternately in opposite directions, i. e. the first, third, fifth, &c. 
to the right hand, and the second, fourth, sixth, &c. to the 



47 


Jan. 1832] Electric currents of a revolving globe . 

left Land ; the whole being placed so that the discs are per- 
pendicular to the v dip, or intersect most directly the magnetic 
curves of powerful magnets. The electricity will be from the 
centre to the circumference in one set of discs, and from the 
circumference to the centre in those on each side of them ; 
thus the*action of the whole will conjoin to produce one com- 
bined and more powerful current. 

159. I have rather, however, been desirous of discovering 
new facts and new relations dependent on magneto-electric in- 
duction, than of exalting the force of those already obtained ; 
being assured that the latter would find their full development . 
hereafter. 

160. I referred in niy former paper to the probable influence 
of terrestrial magneto-electric, induction (137.) in producing, 
either altogether or in part, the phenomena observed by Messrs. 
Christie and Barlow*, whilst revolving ferruginous bodies; 
and especially those observed by the latter when rapidly rota- 
ting an iron shell, which were by that philosopher referred to 
a change in the ordinary disposition of the magnetism of the 
ball. I suggested also that the rotation of a copper globe 
would probably insulate the effects due to electric currents 
from those due to mere derangement of magnetism, and throw 
light upon the true nature of the phenomena. 

161. Upon considering the law already referred to (114.), it 
appeared impossible that a metallic globe could revolve under 
natural circumstances, without having electric currents pro- 
duced within it, circulating round the revolving globe in a 
plane at right angles to the plane of revolution, provided its 
axis of rotation did not coincide with the dip ; and it appeared 
that the current would be most powerful when the axis of re- 
volution was perpendicular to the dip of the needle : for then 
aU those parts of the ball below a plane passing through its 
centre and perpendicular to the dip, would in moving cut the 
magnetic curves in one direction, whilst all those parts above 
that plane would intersect them in the other direction ; currents 
therefore would exist in these moving parts, proceeding from 
one pole of rotation to the other ; but the currents above would 

* Christie, Phil. Trans. 1825, pp. 58, 347, &c. Barlow, Phil. Trans. 1825, 
p. 317. 



48 


Electric currents of a revolving globe. (Series II. 

be in the reverse direction to those below, and in conjunction 
with them would produce a continued circulation of electri- 
city. 

162. As the electric currents are nowhere interrupted in the 
ball, powerful effects were expected, and I endeavoured to 
obtain them with simple apparatus. The ball I used was of 
brass ; it had belonged to an old electrical machine, was hollow, 
thin (too thin), and four inches in diameter; a brass wire was 
screwed into it, and the ball cither turned in the hand by the 
wire, or sometimes, to render it more steady, supported by its 
wire in a notched piece of wood, and motion again given by the 
hand. The ball gave no signs of magnetism when at rest. 

163. A compound magnetic needle was used to detect the 
currents. It was arranged thus : a sewiftg-needle had the head 
and point broken off, and was then magnetized ; being broken 
in halves, the two magnets thus produced were fixed on«a stem 
of dried grass, so as to be perpendicular to it, and about four 
inches asunder ; they were both in one plane, but their similar 
poles in contrary directions. The grass was attached to a piece 
of unspun silk about six inches long, the latter to a stick pass- 
ing through a cork in the mouth of a cylindrical jar ; and thus 
a compound arrangement was obtained, perfectly sheltered 
from the motion of the air, but little influenced by the magnet- 
ism of the earth, and yet highly sensible to magnetic and elec- 
tric forces, when the latter were brought into the vicinity of the 
one or the other needle. 

164. Upon adjusting the needles to the plane of the mag- 
netic meridian ; arranging the ball on the outside of the glass jar 
to the west of the needles, and at such a height that its centre 
should correspond horizontally with the upper needle, whilst 
its axis was in the plane of the magnetic meridian, but perpen- 
dicular to the dip ; and then rotating the ball, the needle was 
immediately affected. Upon inverting the direction of rotation, 
the needle was again affected, but in the opposite direction. 
When the ball revolved from east over to west, the marked 
pole went eastward ; when the ball revolved in the opposite di- 
rection, the marked pole went westward or towards the ball. 
Upon placing the ball to the east of the needles, still the needle 
was deflected in the same way ; i. e. when the ball revolved 
from east over to west, the marked pole went eastward (or to- 



49 


Jan. 1832.] Electric currents in a revolving ball. 

wards the ball) ; when the rotation was in the opposite direc- 
tion, the marked pt)le went westward. 

165. By twisting the silk of the needles, the latter were 
brought into a position perpendicular to the plane of the mag- 
netic meridian ; the ball was again revolved, with its axis 
parallel tt) the needles ; the upper was affected as before, and 
the deflection was such as to show that both here and in the 
former case the needle was influenced solely by currents of 
electricity existing in the brass globe. 

166. If the upper part of the revolving ball be considered 
as a wire moving from east to west, over the unmarked pole of 
the earth, the current of electricity in it should be from north 
to south (99. 114. 150.) ; if the under part be considered as a 
similar wire, moving frOm west to east over the same pole, the 
electric current should be from south to north ; and the circula- 
tion of electricity should therefore be from north above to south, 
and below back to north, in a metal ball revolving from east 
above to west in these latitudes. Now these currents are ex- 
actly those required to give the directions of the needle in the 
experiments just described ; so that the coincidence of the 
theory from which the experiments were deduced with the ex- 
periments themselves, is perfect. 

167. Upon inclining the axis of rotation considerably, the 
revolving ball was still found to affect the magnetic needle ; 
and it was not until the angle which it formed with the mag- 
netic dip was rendered small, that its effects, even upon this 
apparatus, were lost (153.). When revolving with its axis 
parallel to the dip, it is evident that the globe becomes analo- 
gous to the copper plate ; electricity of one kind might be col- 
lected at its equator, and of the other kind at its poles. 

168. A current in the ball, such as that described above 
(161.), although it ought to deflect a needle the same way 
whether it be to the right or the left of the ball and of the 
axis of rotation, ought to deflect it the contrary way when 
above or l?elow the ball ; for then the needle is, or ought to 
be, acted upon in a contrary direction by the current. This 
expectation was fulfilled by revolving the ball beneath the mag- 
netic needle, the latter being still inclosed in its jar. When 
the ball was revolved from east over to west, the marked pole 
of the needle, instead of passing eastward, went westward; 



50 Terrestrial magneto-electric induction . [Series II. 

and when revolved from west over to east, the marked pole 
went eastward. 

169. The deflections of the magnetic needle thus obtained 
with a brass ball are exactly in the same direction as those 
observed by Mr. Barlow in the revolution of the iron shell ; 
and from the manner in which iron exhibits the pheriomena of 
magneto -electric induction like any other metal, and -distinct 
from its peculiar magnetic phenomena (132.) , it is impossible but 
that* electric currents must have been excited, and become active 
in those experiments. What proportion of the whole effect 
obtained is due to this cause, must be decided by a more 
elaborate investigation of all the phenomena. 

170. These results, in conjunction with the general law, 
before stated (114.) suggested an experiment of extreme simpli- 
city, which yet, on trial, was found to answer perfectly. The 
exclusion of all extraneous circumstances and complexity of 
arrangement, and the distinct character of the indications af- 
forded, render this single experiment an epitome of nearly all 
the facts of magneto -electric induction. 

171. A piece of common copper wdre, about eight feet long, 
and one twentieth of an inch in thickness, had one of its ends 
fastened to one of the terminations of the galvanometer wire, 
and the other end to the other termination ; thus it formed an 
endless continuation of the galvanometer wire : it was then 
roughly adjusted into the shape of a rectangle, or rather of a 
loop, the upper part of which could be carried to and fro over 
the galvanometer, whilst the lower part, and the galvanometer 
attached to it, remained steady (Plate II. fig. 30.). Upon 
moving this loop over the galvanometer from right to left, the 
magnetic needle was immediately deflected ; upon passing the 
loop back again, the needle passed in the contrary direction to 
what it did before ; upon repeating these motions of the loop 
in accordance with the vibrations of the needle (39.), the latter 
soon swung through 90° or more. 

172. The relation of the current of electricity produced in 
the wire, to its motion, may be understood by supposing the 
convolutions of the galvanometer aw ay, and the wire arranged 
as a rectangle, with its lower edge horizontal and in the plane 
of the magnetic meridian, and a magnetic needle suspended 
above and over the middle part of this edge,* and directed by 



51 


Jan. 1832,] Electric currents in a moving wire . 

the earth (fig. 30.) . On. passing the upper part of the rect- 
angle from west to east in the position represented by the 
dotted line, the marked pole of the magnetic needle went west ; 
the electric current was therefore from north to south in the 
part of the wire passing under the needle, and from south to 
north in ’the moving or upper part of the parallelogram. On 
passing the upper part of the rectangle from east to west over 
the ^ galvanometer, the marked pole of the needle went east, 
and the current of electricity was therefore the reverse of the 
former. 

173. When the rectangle was arranged in a plane east and 
west, and the magnetic needle made parallel to it, either by 
the torsion of its suspension thread or the action of a magnet, 
still the general effects were the same. On moving the upper 
part of the rectangle from north to south, the marked pole 
of the cieedle went north ; when the w r ire w as moved in the 
opposite direction, the marked pole went south. The same 
effect took place when the motion of the wire was in any 
other azimuth of the line of dip ; the direction of the cur- 
rent always being conformable to the law formerly expressed 
(114.), and also to the directions obtained with the rotating 
ball (164.). 

174. In these experiments it is not necessary to move the 
galvanometer or needle from its first position. It is quite suf- 
ficient if the wire of the rectangle is distorted where it leaves 
the instrument, and bent so as to allow the moving upper part 
to travel in the desired direction. 

175. The moveable part of the wdre was then arranged 
below the galvanometer, but so as to be carried across the dip. 
It affected the instrument as before, and in the same direction ; 
i, e. when carried from w r cst to east under the instrument, the 
marked end of the needle went west, as before. This should, 
of course be the case ; for when the wire is cutting the mag- 
netic dip in a certain direction, an electric current also in a 
certain direction should be induced in it. . 

176. If in fig. 31. dp be parallel to the dip, and B A be con- 
sidered as the upper part of the rectangle (171.), with an ar- 
row c attached to it, both these being retained in a plane per- 
pendicular to the dip, — then, however B A w ith its attached 
arrow is moved upon dp as an axis, if it afterwards proceed 

f 2 



52 Terrestrial magneto -electric induction . [Series II. 

in the direction of the arrow, a current of electricity will move 
along it from B towards A. 

177. When the moving part of the wire was carried up or 
down parallel to the dip, no effect was produced on the galva- 
nometer. When the direction of motion was a little inclined 
to the dip, electricity manifested itself ; and was at a maximum 
when the motion was perpendicular to the magnetic direction. 

178. When the wire was bent into other forms and moved, 
equally strong effects were obtained, especially when instead 
of a rectangle a double catenarian curve was formed of it on 
one side of the galvanometer, and the two single curves or 
halves were swung in opposite directions at the same time ; 
their action then combined to affect the galvanometer : but all 
the results were reducible to those above described. 

179. The longer the extent of the moving wire, and the 
greater the space through which it moves, the greater is the 
effect upon the galvanometer. 

180. The facility with which electric currents are produced 
in metals when moving under the influence of magnets, sug- 
gests that henceforth precautions should always be taken, in 
experiments upon metals and magnets, to guard against such 
effects. Considering the universality of the magnetic influence 
of the earth, it is a consequence which appears very extraordi- 
nary to the mind, that scarcely any piece of metal can be moved 
in contact with others, either at rest, or in motion with dif- 
ferent velocities or in varying directions, without an electric 
current existing within them. It is probable that amongst 
arrangements of steam-engines and metal machinery, some 
curious accidental magneto -electric combinations maybe found, 
producing effects which have never been observed, or, if noticed, 
have never as yet been understood. 


181. Upon considering the effects of terrestrial magneto- 
electric induction which have now been described, it is almost 
impossible to resist the impression that similar effects, but in- 
finitely greater in force, may be produced by the action of the 
globe, as a magnet, upon its own mass, in consequence of its di- 
urnal rotation. It would seem that if a bar of metal be laid in 
these latitudes on the surface of the earth parallel to the mag- 



53 


Jan, 1832.] Currents induced by the earth's rotation. 

netic meridian, a cjurrent of electricity tends to pass through it 
from south to north, in consequence of the travelling of the bar 
from west to east (172.), by the rotation of the earth; that if 
another bar in the same direction be connected with the first 
by wires* it cannot discharge the current of the first, because 
it has an equal tendency to have a current in the same direc- 
tion induced within itself : but that if the latter be carried from 
eas^ to west, which is equivalent to a diminution of the motion 
communicated to it from the earth (172.), then the electric cur- 
rent from south to north is rendered evident in the first bar, 
in consequence of its discharge, at the same time, by means of 
the second. 

182. .Upon the supposition that the rotation of the earth 
tended, by magneto -electro induction, to cause currents in its 
own mass, these would, according to the law (114.) and the 
exper intents, be, upon the surface at least, from the parts in 
the neighbourhood of or towards the plane of the equator, in 
opposite directions to the poles ; and if collectors could be ap- 
plied at the equator and at the poles of the globe, as has been 
done with the revolving copper plate (150.), and also with mag- 
nets (220.), then negative electricity would be collected at the 
equator, and positive electricity at both poles (222.) . But with- 
out the conductors, or something equivalent to them, it is evi- 
dent these currents could not exist, as they could not be dis- 
charged. 

183. I did not think it impossible that some natural differ- 
ence might occur between bodies, relative to the intensity of 
the current produced or tending to be produced in them by 
magneto -electric induction, which might be shown by oppo- 
sing them to each other; especially as Messrs. Arago, Bab- 
bage, Herschel, and Harris, have all found great differ- 
ences, not only between the metals and other substances, but 
between the metals themselves, in their power of receiving mo- 
tion from or giving it to a magnet in trials by revolution (130.). 
I therefore took two wires, each one hundred and twenty feet 
long, one of iron and the other of copper. These were con- 
nected with each other at their ends, and then extended in the 
direction of the magnetic meridian, so as to form two nearly 
parallel lines, nowhere in contact except^ at the extremities. 
The copper wire was then divided in the middle^ and examined 



54 * Terrestrial magneto-electric inductiqn . [Series II. 

by a delicate galvanometer, but no evidence o£ an electrical cur- 
rent was obtained. 

184. By favour of His Royal Highness the President of the 
Society, I obtained the permission of His Majesty to make ex- 
periments at the lake in the gardens of Kensington-palace, for 
the purpose of comparing, in a similar manner, water and 
metal. The basin of this lake is artificial ; the water is sup- 
plied by the Chelsea Company ; no springs run into it, and it 
presented what I required, namely, a uniform mass of still pure 
water, with banks ranging nearly from east to west, and from 
north to south. 

185. Two perfectly clean bright copper plates, each expo- 
sing four square feet of surface, were soldered to the extremi- 
ties of a copper wire ; the plates were immersed in the water, 
north and south of each other, the wire which connected them 
being arranged upon the grass of the bank. The plates were 
about four hundred and eighty feet from each other, in a right 
line ; the wire was probably six hundred feet long. This wire 
was then divided in the middle, and connected by two cups of 
mercury with a delicate galvanometer. 

186. At first, indications of electric currents were obtained ; 
but when these were tested by inverting the direction of con- 
tact, and in other ways, they were found to be due to other 
causes than the one sought for. A little difference in tempe- 
rature ; a minute portion of the nitrate of mercury used to 
amalgamate the wires, entering into the water employed to re- 
duce the two cups of mercury to the same temperature ; was 
sufficient to produce currents of electricity, which affected the 
galvanometer, notwithstanding they had to pass through nearly 
five hundred feet of water. When these and other interfering 
causes were guarded against, no- effect was obtained ; ' and 
it appeared that even such dissimilar substances as water and 
copper, when cutting the magnetic curves of the earth with 
equal velocity, perfectly neutralized each other’s action. 

187. Mr. Pox of Falmouth has obtained some highly im- 
portant results respecting the electricity of metalliferous veins 
in the mines of Cornwall, which have been published in the 
Philosophical Transactions*. I have examined the paper 
with a view to ascertain whether any of the effects were pro- 

* 1830, p. 399. 



Jan. 1832.] Currents induced by the earth’s rotation. 55 

bably referable to magneto -electric induction • but, though un- 
able to form a verj- strong opinion, believe they are not. When 
parallel veins running east and west were compared, the general 
tendency of the electricity in the wires was from north to south ; 
when the comparison was made between parts towards the sur- 
face and at some depth, the current of electricity in the wires 
was from, above downwards. If there should be any natural 
difference in the force of the electric currents produced by 
magneto-electric induction in different substances, or substances 
in different positions moving with the earth, and which might 
be rendered evident by increasing the masses acted upon, then 
the wires and veins experimented with by Mr. Fox might per- 
haps have acted as dischargers to the electricity of the mass of 
strata included between them, and the directions of the cur- 
rents would agree with those observed as above. 

188. •Although the electricity obtained by magneto -electric 
induction in a few feet of wire is of but small intensity, and has 
not yet been observed except in metals, and carbon in a parti- 
cular state, still it has power to pass through brine (23.) ; and, 
as increased length in the substance acted upou produces 
increase of intensity, I hoped to obtain effects from extensive 
moving masses of water, though quiescent water gave none. I 
made experiments therefore (by favour) at Waterloo Bridge, 
extending a copper wire nine hundred and sixty feet in length 
upon the parapet of the bridge, and dropping from its ex- 
tremities other wires with extensive plates of metal attached to 
them to complete contact with the water. Thus the wire and 
the water made one conducting circuit ; and as the water ebbed 
or flowed with the tide, I hoped to obtain currents analogous 
to those of the brass ball (161.). 

189. 1 constantly obtained deflections at the galvanometer, 
but they were very irregular, and were, in succession, referred 
to other causes than that sought for. The different condition 
of the water as to purity on the two sides of the river ; the 
difference in temperature ; slight differences in the plates, in the 
solder used, in the more or less perfect contact made by twisting 
or otherwise ; all produced effects in turn : and though I expe- 
rimented on the water passing through the middle arches only; 
used platina plates instead of copper ; and took every other pre- 
caution, I could not after three days obtain any satisfactory results . 



56 Terrestrial magneto -electric induction. [Series II. 

190. Theoretically, it seems a necessary consequence, that 
where water is flowing, there electric currents' should be formed : 
thus, if a line be imagined passing from Dover to Calais through 
the sea, and returning through the land beneath the water to 
Dover, it traces out a circuit of conducting matter, one part of 
which, when the water moves up or down the channel, is cut- 
ting the magnetic curves of the earth, whilst the other is rela- 
tively at rest. This is a repetition of the wire experiment 
(171.), but with worse conductors. Still there is every reason 
to believe that electric currents do run in the general direction 
of the circuit described, either one way or the other, according 
as the passage of the water is up or down the channel. Where 
the lateral extent of the moving water is enormously increased, 
it does not seem improbable that the effect should become sen- 
sible ; and the gulf stream may thus, perhaps, from electric 
currents moving across it, by magneto-electric induction from 
the earth, exert a sensible influence upon the forms of the lines 
of magnetic variation*. 

191. Though positive results have not yet been obtained by 
the action of the earth upon water and aqueous fluids, yet, as 
the experiments are very limited in their extent, and as such 
fluids do yield the current by artificial magnets (23.), (for 
transference of the current is proof that it may be produced 
(213.),) the supposition made that the earth produces these 
induced currents within itself (181.) in consequence of its di- 
urnal rotation, is still highly probable (222. 223.) ; and when 
it is considered that the moving masses extend for thousands 
of miles across the magnetic curves, cutting them in various di- 
rections wdthin its mass, as well as at the surface, it is possible 
the electricity may rise to considerable intensity. 

192. I hardly dare venture, even in the most hypothetical 
form, to ask whether the Aurora Borealis and Australis may 
not be the discharge of electricity, thus urged towards the 
poles of the earth, from whence it is endeavouring to return 
by natural and appointed means above the earth to the equa- 
torial regions. The non-occurrence of it in very high latitudes 

* Theoretically, even a ship or a boat when passing on the surface of the 
water, in northern or southern latitudes, should have currents of electricity 
running through it directly across the line of her motion ; or if the water is 
flowing past the ship at anchor, similar currents should occur. 



Jan. 1832.] Differences of currents induced in different bodies . 57 

is not at all against the supposition ; and it is remarkable that 
Mr. Fox, who observed the deflections of the magnetic needle 
at Falmouth, by the Aurora Borealis, gives that direction of it 
which perfectly agrees with the present view. He states that 
all the variations at night were towards the east *, and this is 
what would happen if electric currents were setting from south 
to north -in the earth under the needle, or from north to south 
in t s pace above it. 

§ 6. General remarks and illustrations of the Force and Di- 
rection of Magneto-electric induction. 

193. In the repetition and variation of Aragons experiment 
by Messrs. Babbage, Herschel, and Harris, these philosophers 
directed their attention to the differences of force observed 
amongst the metals and other substances in their action on the 
magnot. These differences were very great f, and led me to 
hope that by mechanical combinations of various metals import- 
ant results might be obtained (183). The following experi- 
ments were therefore made, with a view to obtain, if possible, 
any such difference of the action of two metals. 

194. A piece of soft iron bonnet-wire covered with cotton 
was laid bare and cleaned at one extremity, and there fastened 
by metallic contact with the clean end of a copper wire. Both 
wires were then twisted together like the strands of a rope, 
for eighteen or twenty inches ; and the remaining parts being 
made to diverge, their extremities were connected with the 
wires of the galvanometer. The iron wire was about two feet 
long, the continuation to the galvanometer being copper. 

195. The twisted copper and iron (touching each other no- 

where but at the extremity) were then passed between the poles 
of a powerful magnet arranged horse-shoe fashion (fig. 32.) ; 
but not the slightest effect was observed at the galvanometer, 
although the arrangement seemed fitted to show any electrical 
difference between the two metals relative to the action of 
the magnet. , 

196. A soft iron cylinder was then covered with paper at the 
middle part, and the twisted portion of the above compound 
wire coiled as a spiral around it, the connexion with the galva- 

* Philosophical Transactions, 1831, p. 202. t Ibid. 1825, p. 472 ; 1831, p. 78. , 



58 Magneto-electric induction. [Series II. 

nometer still being made at the ends A B. The iron cylin- 
der was then brought in contact with the poles of a powerful 
magnet capable of raising thirty pounds ; yet no signs of elec- 
tricity appeared at the galvanometer. Every precaution was 
applied in making and breaking contact to accumulate effect, 
but no indications of a current could be obtained. 

197. Copper and tin, copper and zinc, tin and zinc, tin and 
iron, and zinc and iron, were tried against each other in a simi- 
lar manner (194), but not the slightest sign of electric currents 
could be procured. 

198. Two flat spirals, one of copper and the other of iron, 
containing each eighteen inches of wire were connected with 
each other and with the galvanometer, and then put face to 
face so as to be in contrary directions. 'When brought up to 
the magnetic pole (53.), no electrical indications at the galva- 
nometer were observed. When one was turned round so that 
both were in the same direction, the effect at the galvanometer 
was very powerful. 

199. The compound helix of copper and iron wire formerly 
described (8.) was arranged as a double helix, one of the helices 
being all iron and containing two hundred and fourteen feet, 
the other all copper and containing two hundred and eight 
feet. The two similar ends A A of the copper and iron helix 
were connected together, and the other ends B B of each helix 
connected with the galvanometer ; so that when a magnet was 
introduced into the centre of the arrangement, the induced 
currents in the iron and copper would tend to proceed in con- 
trary directions. Yet when a magnet was inserted, or a soft 
iron bar within made a magnet by contact with poles, no effect 
at the needle was produced. 

200. A glass tube about fourteen inches long was fllled with 
strong sulphuric acid. Twelve inches of the end of a clean 
copper wire were bent up into a bundle and inserted into the 
tube, so as to make good superficial contact with the acid, and 
the rest of the wire passed along the outside of the tube mad 
away to the galvanometer. A wire similarly bent up afcjfthe 
extremity was immersed in the other end of the sulphuric j$sid, 
and also connected with the galvanometer, so that the acid and 
copper wire were in the same parallel relation to each other in 
this experiment as iron and copper were in the first (194). 



Jan. 1832.] Strength of current induced in different bodies. 59 

When this arrangement was passed in a simiJarmanner between 
the poles of the magnet, not the slightest effect at the galva- 
nometer could be perceived. 

201. From these experiments it would appear, that when 
metals gf different kinds connected in one circuit are equally 
subject in every circumstance to magneto -electric induction, 
they exhibit exactly equal powers with respect to the currents 
which either arc formed, or tend to form, in them. The same 
evqn appears to be the case with regard to fluids, and probably 
all other substances. 

202. Still it seemed impossible that these results could indi- 
cate the relative inductive power of the magnet upon the differ- 
ent metals ; for that the effect should be in some relation to 
the conducting power seemed a necessary consequence (139), 
end the influence of rotating plates upon magnets had been 
found *to bear a general relation to the conducting power of the 
substance used. 

203. In the experiments of rotation (81.), the electric cur- 
rent is excited and discharged, in the same substance, be it a 
good or bad conductor ; but in the experiments just described 
the current excited in iron could not be transmitted but through 
the copper, and that excited in copper had to pass through 
iron ; i. e. supposing currents of dissimilar strength to be 
formed in the metals proportionate to their conducting power, 
the stronger current had to pass through the worst conductor, 
and the weaker current through the best. 

204. Experiments were therefore made in which different 
metals insulated from each other were passed between the poles 
of the magnet, their opposite ends being connected with the 
same end of the galvanometer wire, so that the currents 
formed and led away to the galvanometer should oppose each 
other } and when considerable lengths of different wires were 
used, feeble deflections were obtained. 

205. To obtain perfectly satisfactory results a new galva- 
nometer was constructed, consisting of two independent coils, 
each containing eighteen feet of silked copper wire. These 
coils were exactly alike in shape and number of turns, and were 
fixed side by side with a small interval between them, in which 
a double needle could be hung by a fibre of silk exactly as in 
the former instrument (87.) The coils may be distinguished by 



60 Magneto-electric induction. [Series II. 

the letters K L, and when electrical currents were sent through 
them in the same direction, acted upon the needle with the 
sum of their powers; when in opposite directions, with the 
difference of their powers. 

206. The compound helix (199. 8.) was now connected, the 
ends A and B of the iron with A and B ends of galvanometer 
coil K, and the ends A and B of the copper with B and A ends 
of galvanometer coil L, so that the currents excited in the two 
helices should pass in opposite directions through the coils K 
and L. On introducing a small cylinder magnet within the 
helices, the galvanometer needle was powerfully deflected. On 
disuniting the iron helix, the magnet caused with the copper 
helix alone still stronger deflection in the same direction. On 
reuniting the iron helix, and unconnectmg the copper helix, 
the magnet caused a moderate deflection in the contrary direc- 
tion. Thus it was evident that the electric current induced by 
a magnet in a copper wire was far more powerful than the cur- 
rent induced by the same -magnet in an equal iron wire. 

207. To prevent any error that might arise from the greater 
influence, from vicinity or other circumstances, of one coil on 
the needle beyond that of the other, the iron and copper ter- 
minations were changed relative to the galvanometer coils K L, 
so that the one which before carried the current from the cop- 
per now conveyed that from the iron, and vice versA But the 
same striking superiority of the copper was manifested as be- 
fore. This precaution was taken in the rest of the experiments 
with other metals to be described. 

208. I then had wires of iron, zinc, copper, tin, and lead, 
drawn to the same diameter (very nearly one twentieth of an 
inch), and I compared exactly equal lengths, namely sixteen 
feet, of each in pairs in the following manner : The ends of the 
copper wire were connected with the ends A and B of galva- 
nometer coil K, and the ends of the zinc wire with the termi- 
nations. A and B of the galvanometer coil L. The middle part 
of each wire was then coiled six times round a cylinder of soft 
iron covered with paper, long enough to connect the poles of 
Daniell's horse-shoe magnet (56,) (fig. 33.), so that similar 
helices of copper and zinc, each of six turns, surrounded the 
bar at two places equidistant from each other and from the 
poles of the magnet ; but these helices were purposely arranged 



Jan. 1832.] Induced current varies with the conductor used . 61 

so as to be in. contrary directions, and therefore send contrary 
currents through *t he galvanometer coils K and L. 

209. On making and breaking contact between the soft iron 
bar and the poles of the magnet, the galvanometer was strongly 
affected ; on detaching the zinc it was still more strongly 
affected *in the same direction. On taking all the precautions 
before alluded to (207.) , with others, it was abundantly proved 
that the current induced by the magnet in copper was far more 
powerful than in zihc. 

210. The copper Avas then compared in a similar manner 
with tin, lead, and iron, and surpassed them all, even more 
than it did zinc. The zinc was then compared experimentally 
with the tin, lead, and iron, and found to produce a more 
powerful current than* any of them. Iron in the same manner 
proved superior to tin and lead. Tin came next, and lead 
tlie lasj;. 

211. Thus the order of these metals is copper, zinc, iron, 
tin, and lead. It is exactly their order with respect to con- 
ducting power for electricity, and, with the exception of iron, 
is the order presented by the magneto -rotation experiments 
of Messrs. Babbage, Ilerschel, Harris, &c. The iron has ad- 
ditional power in the latter kind of experiments, because of its 
ordinary magnetic relations, and its place relative to magneto- 
electric action of the kind now under investigation cannot be 
ascertained by such trials. In the manner above described it 
may be correctly ascertained.* 

212. It must still be observed that in these experiments the 
whole effect between different metals is not obtained ; for of 
the thirty-four feet of wire included in each circuit, eighteen 
feet are copper in both, being the wire of the galvanometer 
coils ; and as the whole circuit is concerned in the resulting 
force of the current, this circumstance must tend to diminish 
the difference which would appear between the metals if the 
circuits were of the same substances throughout. In the 
present case the difference obtained is probably not more than 

* Mr. Christie, who being appointed reporter upon this paper, had it in his 
hands before it was complete, felt the difficulty (202.) ; and to satisfy his 
mind, made experiments upon iron and copper with the large magnet (44.), 
and came to the same conclusions as I have arrived at. The two set# of ex- 
periments were perfectly independent of each other, neither of us being aware 
of the other’s proceedings. 



62 Magneto -electric induction . [Series II. 

a half of that which would be given if the whole of each circuit 
were of one metal. 

213. These results tend to prove that the currents produced 
by magneto- electric induction in bodies is proportional to their 
conducting power. That they are exactly proportional to and 
altogether dependent upon the conducting power, is, 1 think, 
proved by the perfect neutrality displayed when two metals or 
other substances, as acid, water, &c. &c. (201. 186.), are opposed 
to each other in their action. The feeble current which tends 
to be produced in the worse conductor, has its transmission 
favoured in the better conductor, and the stronger current 
which tends to form in the latter has its intensity diminished 
by the obstruction of the former ; and the forces of generation 
and obstruction are so perfectly balanced* as to neutralize each 
other exactly. Now r as the obstruction is inversely as the con- 
ducting power, the tendency to generate a current must be 
directly as that power to produce this perfect equilibrium. 

214. The cause of the equality of action under the various 
circumstances described, where great extent of wire (183.) or 
wire and water (184.) were connected together, which yet pro- 
duced such different effects upon the magnet, is now evident 
and simple. 

215. The effects of a rotating substance upon a needle or 
magnet ought, where ordinary magnetism has no influence, to 
be directly as the conducting power of the substance ; and I 
venture now to predict that such will be found to be the case ; 
and that in all those instances where non-conductors have been 
supposed to exhibit this peculiar influence, the motion has 
been due to some interfering cause of an ordinary kind ; as 
mechanical communication of motion through the parts of the 
apparatus, or otherwise (as in the case Mr. Harris has pointed 
out *) ; or else to ordinary magnetic attractions. To distinguish 
the effects of the latter from those of the induced electric cur- 
rents, I have been able to devise a most perfect test, which 
shall be almost immediately described (243.) . 

216. There is every reason to believe that the magnet or 
magnetic needle will become an excellent measurer of the con- 
ducting power of substances rotated near it ; for I have found 

* Philosophical Transactions, 1831, p. 68. 



Jan. 1832.] Essential condition of magneto-electric induction. 63 

by careful experiment, that when a constant current of elec- 
tricity was sent successively through a series of wires of cop- 
per, plat in a, zinc, silver, lead, and tin, drawn to the same 
diameter ; the deflection of the needle was exactly equal by 
them all. It must be remembered that when bodies are rotated 
in a horizontal plane, the magnetism of the earth is active upon 
them. As the effect is general to the whole of the plate, it 
may not interfere in these eases ; but in some experiments and 
calculations may be of important consequence. 

217. Another point which I endeavoured to ascertain, was, 
whether it was essential or not that the moving part of the wire 
should, in cutting the magnetic curves, pass into positions of 
greater or lesser magnetic force ; or whether, always inter- 
secting curves of equal magnetic intensity, the mere motion was 
sdfhcieyt for the production of the current. That the latter is 
true, has been proved already in several of the experiments on 
terrestrial magneto-electric induction. Thus the electricity 
evolved from the copper plate (149.), the currents produced in 
the rotating globe (161, &c.), and those passing through the 
moving wire (171.), arc all produced under circumstances in 
which the magnetic force could not but be the same during the 
whole experiments. 

218. To prove the point with an ordinary magnet, a copper 
disc was cemented upon the end of a cylinder magnet, with 
paper intervening ; the magnet and disc were rotated together, 
and collectors (attached to the galvanometer) brought in contact 
with the circumference and the central part of the copper plate. 
The galvanometer needle moved as in former cases, and the 
direction of motion was the same as that which would have re- 
sulted^ if the copper only had revolved, and the magnet been 
fixed. Neither was there any apparent difference in the quan- 
tity of deflection. Hence, rotating the magnet causes no dif- 
ference in the results ; for a rotatory and a stationary magnet 
produce the same effect upon the moving copper. 

219. A copper cylinder, closed at one extremity, was then 
put over the magnet, one half of which it inclosed like a cap ; 
it was firmly fixed, and prevented from touching the magnet 
anywhere by interposed paper. The arrangement was then 
floated in a narrow jar of mercury, so that the lower edge of the 



64 Electricity evolved from a rotating magnet . [Series II. 

copper cylinder touched the fluid metal ; one wire of the galva- 
nometer dipped into this mercury, and the other into a little 
cavity in the centre of the end of the copper cap. Upon rota- 
ting the magnet and its attached cylinder, abundance of elec- 
tricity passed through the galvanometer, and in the same di- 
rection as if the cylinder had rotated only, the magrfet being 
still. The results therefore were the same as thbse with the 
disc (218.) . 

220. That the metal of the magnet itself might be substituted 
for the moving cylinder, disc, or wire, seemed an inevitable 
consequence, and yet one which would exhibit the effects of 
magneto -electric induction in a striking form. A cylinder mag- 
net had therefore a little hole made in the centre of each end 
to receive a drop of mercury, and was*then floated pole up- 
wards in the same metal contained in a narrow jar. One wire 
from the galvanometer dipped into the mercury of Ijie jar, 
and the other into the drop contained in the bole at the upper 
extremity of the axis. The magnet was then revolved by a 
piece of string passed round it, and the galvanometer-needle 
immediately indicated a powerful current of electricity. On 
reversing the order of rotation, the electrical current was re- 
versed. The direction of the electricity was the same as if the 
copper cylinder (219.) or a copper wire had revolved round the 
fixed magnet in the same direction as that which the magnet 
itself had followed. Thus a singular independence of the mag- 
netism and the bar in which it resides is rendered evident. 

221. In the above experiment the mercury reached about 
half way up the magnet ; but when its quantity was increased 
until within one eighth of an inch of the top, or diminished 
until equally near the bottom, still the same effects and the 
same direction of electrical current was obtained. But in those 
extreme proportions the effects did not appear so strong as 
when the surface of the mercury was about the middle, or 
between that and an inch from each end. The magnet was 
eight inches and a half long, and three quarters of an inch in 
diameter. 

222. Upon inversion of the magnet, and causing rotation 
in the same direction, i. e. always screw or always unscrew, 
then a contrary current of electricity was produced. Blit when 
the motion of the magnet was continued in a direction constant 



Jan. 1832.] Evolution of electricity from a revolving magnet. 65 

in relation to its own axis , then electricity of the same kind 
was collected at both poles, and the opposite electricity at the 
equator, or in its neighbourhood, or in the parts corresponding 
to it. If the magnet be held parallel to the axis of the earth, 
with its unmarked pole directed to the pole star, and then ro- 
tated so •that the parts at its southern side pass from west to 
east in conformity to the motion of the earth; then positive 
electricity may be collected at the extremities of the magnet, 
and negative electricity at or about the middle of its mass. 

223. When the galvanometer was very sensible, the mere 
spinning of the magnet in the air, whilst one of the galvano- 
meter wires touched the extremity, and the other the equatorial 
parts, was sufficient to evolve a current of electricity and de- 
flect the needle. 

224. Experiments were then made with a similar magnet, 
for the purpose of ascertaining whether any return of the elec- 
tric current could occur at the central or axial parts, they 
having the same angular velocity of rotation as the other parts 
(259.); the belief being that it could not. 

225. A cylinder magnet, seven inches in length, and three 
quarters of an inch in diameter, had a hole pierced in the di- 
rection of its axis from one extremity, a quarter of an inch in 
diameter, and three inches deep. A copper cylinder, sur- 
rounded by paper and amalgamated at both extremities, was 
introduced so as to be in metallic contact at the bottom of the 
hole, by a little mercury, with the middle of the magnet ; in- 
sulated at the sides by the paper; and projecting about a 
quarter of an inch above the end of the steel. A quill was put 
over the copper rod, which reached to the paper, and formed 
a cup to receive mercury for the completion of the circuit. A 
high paper edge was also raised round that end of the magnet 
and mercury put within it, which however had no metallic con- 
nexion with that in the quill, except through the magnet itself 
and the copper rod (fig. 34.). The wires A and B from the 
galvanometer were dipped into these two portions of mercury ; 
any current through them could, therefore, only pass down the 
magnet towards its equatorial parts, and then up the copper 
rod ; or vice versa. 

226. When thus arranged and* rotated screw fashion, the 
marked end of the galvanometer needle went west, indicating 



66 Electricity obtained from, a revolving magnet . [Series II. 

that there was a current through the instrument from A to B, 
and consequently from B through the magnfet and copper rod 
to A (fig. 34.). 

22 7. The magnet was then put into a jar of mercury (fig. 
35.) as before (319.); the wire A left in contact with the cop- 
per axis, but the wire B dipped in the mercury of thd jar, and 
therefore in metallic communication with the equatprial parts 
of the magnet instead of its polar extremity. On revolving the 
magnet screw fashion, the galvanometer needle was deflected 
in the same direction as before, but far more powerfully. Yet 
it is evident that the parts of the magnet from the equator to 
the pole were out of the electric circuit. 

228. Then the wire A was connected with the mercury on the 
extremity of the magnet, the wire B still remaining in contact 
with that in the jar (fig. 36.), so that the copper axis was al- 
together out of the circuit. The magnet was again revolved 
screw fashion, and again caused the same deflection of the 
needle, the current being as strong as it was in the last trial 
(2 27.), and much stronger than at first (226.). 

229. Hence it is evident that there is no discharge of the 
current at the centre of the magnet, for the current, now freely 
evolved, is up through the magnet ; but in the first experiment 
(226.), it was down. In fact, at that time, it was only the part 
of the moving metal equal to a little disc extending from the 
end of the wire B in the mercury to the wire A that was ef- 
ficient, i. e. moving with a different angular velocity to the rest 
of the circuit (258.) ; and for that portion the direction of the 
current is consistent with the other results. 

230. In the two after experiments, the lateral parts of the 
magnet or of the copper rod are those which move relative to 
the other parts of the circuit, i. e. the galvanometer wires ; and 
being more extensive, intersecting more curves, or moving 
with more velocity, produce the greater effect. For the discal 
part, the direction of the induced electric current is the same 
in all, namely, from the circumference towards the centre. 

231. The law under which the induced electric current ex- 
cited in bodies moving relatively to magnets, is made dependent 
on the intersection of the magnetic curves by the metal (114.) 
being thus rendered more precise and definite (217. 220. 224:), 



Jan. 1832.] Volt a* electric and magneto~electric induction . 67 

seem now even to apply to the cause in the first section of the 
former paper (26.^ ; and by rendering a perfect reason for the 
effects produced, take away any for supposing that peculiar 
condition, which I ventured to call the electro-tonic state (60.) . 

232. When an electrical current is passed through a wire, 
that wire is surrounded at every part by magnetic curves, ^di- 
minishing in intensity according to their distance from the wire, 
and which in idea may be likened to rings situated in planes 
perpendicular to the wire or rather to the electric current 
within it. These curves, although different in form, are per- 
fectly analogous to those existing between two contrary mag- 
netic poles opposed to each other ; and when a second wire, 
parallel to that which carries the current, is made to approach 
the latter (18.), it passes through magnetic curves exactly 
of the same kind as those it would intersect when carried be- 
tween opposite magnetic poles (100.) in one direction ; and as 
it recedes from the inducing wire, it cuts the curves around it 
in the same manner that it would do those between the same 
poles if moved in the other direction. 

233. If the wireN P (fig. 40.) have an electric current passed 
through it in the direction from P to N, then the dotted ring 
may represent a magnetic curve round it, and it is in such 
a direction that if small magnetic needles be placed as tangents 
to it, they will become arranged as in the figure, n and s indi- 
cating north and south ends (44. note ) . 

234. But if the current of electricity were made to cease for 
a while, and magnetic poles were used instead to give direction 
to the needles, and make them take the same position as when 
under the influence of the current, then they must be arranged 
as at fig. 41 ; the marked and unmarked poles a b above the 
wire, being in opposite directions to those a' b ' below. In such 
a position therefore the magnetic curves between the poles a 
b and a 1 b f have the same general direction with the cor- 
responding parts of the ring magnetic curve surrounding the 
wire N P carrying an electric Current. 

235. If the second wire p n (fig. 40.) be now brought to- 
wards the principal wire? carrying a current, it will cut an in- 
finity of magnetic curves, similar in direction to that figured, 
and consequently similar in direction to those between the 
poles a b of the magnets (fig. 41.), and it will intersect 

v 2 



68 Volta-electric and magneto -electric induction . [Series II. 

these current curves in the same manner as it would the mag- 
net curves, if it passed from above between the poles down- 
wards, Now, such an intersection would, with the magnets, 
induce an electric current in the wire from p to n (114,); and 
therefore as the curves are alike in arrangement, the same ef- 
fect ought to result from the intersection of the magnetic 
curves dependent on the current in the wire N P ; and such is 
the case, for on approximation the induced current is in £he 
opposite direction to the principal current (19.). 

236. If the wire p 1 n 1 be carried up from below, it will pass 

in the opposite direction between the magnetic poles ; but then 
also the magnetic poles themselves are reversed (fig. 41.), and 
the induced current is therefore (114.) still in the same direc- 
tion as before. It is also, for equally ‘sufficient and evident 
reasons, in the same direction, if produced by the influence of 
the curves dependent upon the wire. <> 

237. When the second wire is retained at rest in the vicinity 
of the principal wire, no current is induced through it, for it is 
intersecting no magnetic curves. When it is removed from 
the principal wire, it intersects the curves in the opposite di- 
rection to what it did before (235.) ; and a current in the op- 
posite direction is induced, which therefore corresponds with 
the direction of the principal current (19.). The same effect 
would take place if by inverting the direction of motion of the 
wire in passing between either set of poles (fig. 41.), it were 
made to intersect the curves there existing in the opposite di- 
rection to what it did before. 

238. In the first experiments (10. 13.), the inducing wire 
and that under induction were arranged at a fixed distance 
from each other, and then an electric current sent through the 
former. In such cases the magnetic curves themselves must 
be considered as moving (if I may use the expression) across 
the wire under induction, from the moment at which they begin 
to be developed until the magnetic force of the current is at its 
utmost; expanding as it were from the wire outwards^ and 
consequently being in the same relation to the fixed wire under 
induction, as if it had moved in the opposite direction across 
them, or towards the wire carrying the current. Hence the first 
current induced in such cases was in the contrary direction to 
the principal current (17 . 235.) . On breaking the battery con- 



J an. 1832.] Relation of the magnetic curves fy evolved current. 69 

tact, the magnetic curves (which are mere expressions for ar- 
ranged magnetic forces) may be conceived as contracting npon 
and returning towards the failing electrical current, and there- 
fore move in the opposite direction across the wire, and cause 
an opposite induced current to the first. 

239. When, in experiments with ordinary magnets, the latter, 
in place* of being moved past the wires, were actually made 
ne^r them (27. 36.), then a similar progressive development of 
the magnetic curves may be considered as having taken place, 
producing the effects which would have occurred by motion of 
the wires in one direction ; the destruction of the magnetic 
power corresponds to the motion of the wire in the opposite 
direction. 

240. If, instead of intersecting the magnetic curves of a straight 
wire carrying a current, by approximating or removing a se- 
cond wire (235.), a revolving plate be used, being placed for that 
purpose near the wire, and, as it were, amongst the magnetic 
curves, then it ought to have continuous electric currents in- 
duced within it ; and if a line joining the wire with the centre 
of the plate were perpendicular to both, then the induced cur- 
rent ought to be, according to the law (114.), directly across 
the plate, from one side to the other, and at right angles to 
the direction of the inducing current. 

241. A single metallic wire one twentieth of an inch in dia- 
meter had an electric current passed through it, and a small 
copper disc one inch and a half in diameter revolved near to 
and under, but not in actual contact with it (fig. 39.). Collec- 
tors were then applied t at the opposite edges of the disc, and 
wires from them connected with the galvanometer. As the 
disc revolved in one direction, the needle was deflected on one 
side ; and when the direction of revolution was reversed, the 
needle was inclined on the other side, in accordance with the 
results anticipated. 

24 2. Thus the reasons which induce me to suppose a parti- 
cular state in the wire (60.) have disappeared ; and though it 
still seems to me unlikely that a wire at rest in the neighbour- 
hood of another carrying a powerful electric current is entirely 
indifferent to it, yet I am not aware of any distinct facts which 
authorize the conclusion that it is in a particular state. 

&43, In considering the nature of the cause assigned in these 



70 


Magnetic and magneto-electric [Series II. 

papers to account for the mutual influence of magnets and 
moving metals (120.), and comparing it with that heretofore 
admitted, namely, the induction of a feeble magnetism like that 
produced in iron, it occurred to me that a most decisive ex- 
perimental test of the two views could be applied (215.). 

244. No other known power has like direction with that 
exerted between an electric current and a magnetic pole ; it is 
tangential, while all other forces, acting at a distance, are direct. 
Hence, if a magnetic pole on one side of a revolving plate fol- 
low its course by reason of its obedience to the tangential force 
exerted upon it by the very current of electricity which it has 
itself caused, a similar pole on the opposite side of the plate 
should immediately set it free from this force ; for the currents 
which tend to be formed by the action of' the two poles are in 
opposite directions ; or rather no current tends to be formed, 
or no magnetic curves are intersected (114.) ; and therefore the 
magnet should remain at rest. On the contrary, if the action 
of a north magnetic pole were to produce a southness in the 
nearest part of the copper plate, and a diffuse northness else- 
where (82.) , as is really the case with iron ; then the use of 
another north pole on the opposite side of the same part of the 
plate should double the effect instead of destroying it, and 
double the tendency of the first magnet to move with the 
plate. 

245. A thick copper plate (85.) was therefore fixed on a 
vertical axis, a bar magnet was suspended by a plaited silk 
cord, so that its marked pole hung over the edge of the plate, 
and a sheet of paper being interposed, the plate was revolved ; 
immediately the magnetic pole obeyed its motion and passed 
off in the same direction. A second magnet of equal size and 
strength was then attached to the first, so that its marked pole 
should hang beneath the edge of the copper plate in a corre- 
sponding position to that above, and at an equal distance (fig. 
37.). Then a paper sheath or screen being interposed as be- 
fore, and the plate revolved, the poles were found entirely in- 
different to its motion, although either of them alone would 
have followed the course of rotation. 

246. On turning one magnet round, so that opposite poles 
were on each side of the plate, then the mutual action of the, 
poles and the moving metal was a maximum. 

247. On suspending one magnet so that its axis was level 



Jan. 1832.] induction distinguished . 71 

with the plate, and either pole opposite its edge, the revolution 
of the plate caused no motion of the magnet. The electrical 
currents dependent upon induction would now tend to be pro- 
duced in a vertical direction across the thickness of the plate, 
but could not be so discharged, or at least only to so slight a 
degree as to leave all effects insensible ; but ordinary magnetic 
induction, or that on an iron plate, would be equally if not more 
powerfully developed in such a position (251.). 

218. Then, with regard to the production of electricity in 
these cases : — whenever motion was communicated by the plate 
to the magnets, currents existed ; when it was not communi- 
cated, they ceased. A marked pole of a large bar magnet was 
put under the edge of the plate ; collectors (86.) applied at the 
axis and edge of the* plate as on former occasions (fig. 38.), 
and these connected with the galvanometer; when the plate 
was rewlved, abundance of electricity passed to the instrument. 
The unmarked pole of a similar magnet was then put over the 
place of the former pole, so that contrary poles were above 
and below; on revolving the plate, the electricity was more 
powerful than before. The latter magnet was then turned end 
for end, so that marked poles were both above and below the 
plate, and then, upon revolving it, scarcely any electricity was 
procured. By adjusting the distance of the poles so as to cor- 
respond with their relative force, they at last were brought so 
perfectly to neutralize each other's inductive action upon the 
plate, that no electricity could be obtained with the most rapid 
motion, 

249. I now proceeded to compare the effect of similar and dis- 
similar poles upon iron and copper, adopting for the purpose 
Mr. Sturgeon's very useful form of Arago's experiment. This 
consists in a circular plate of metal supported in a vertical 
plane by a horizontal axis, and weighted a little at one edge or 
rendered ekcentric so as to vibrate like a pendulum. The 
poles of the magnets are applied near the side and edges of 
these plates, and then the number of vibrations, required to 
reduce the vibrating are a certain constant quantity, noted. 
In the first description of this instrument* it is said that 
opposite poles "produced the greatest retarding effect, and 
similar poles none; and yet within a page of the place the 
* Edin, Phil. Journal, 1825, p, 124. 



72 Magnetic and magneto-electric [Series II. 

effect is considered as of the same kind with that produced in 
iron. 

250. I had two such plates mounted, one of copper, one of 
iron. The copper plate alone gave sixty vibrations, in the 
average of several experiments, before the arc of vibration was 
reduced from one constant mark to another. On placing op- 
posite magnetic poles near to, and on each side of, the same 
place, the vibrations were reduced to fifteen. On putting 
similar poles on each side of it, they rose to fifty ; and on pla- 
cing two pieces of wood of equal size with the poles equally 
near, they became fifty- two. So that, when similar poles were 
used, the magnetic effect was little or none (the obstruction 
being due to the confinement of the air, rather) , whilst with 
opposite poles it was the greatest possible. When a pole was 
presented to the edge of the plate, no retardation occurred. t 

251. The iron plate alone made thirty-two vibrations; whilst 
the arc of vibration diminished a certain quantity. On pre- 
senting a magnetic pole to the edge of the plate (247.), the 
vibrations were diminished to eleven • and when the pole was 
about half an inch from the edge, to five. 

252. When the marked pole, was put at the side of the 
iron plate at a certain distance, the number of vibrations was 
only five. When the marked pole of the second bar was put 
on the opposite side of the plate at the same distance (250.), the 
vibrations were reduced to two. But when the second pole 
was an unmarked one, yet occupying exactly the same position, 
the vibrations rose to twenty-two. By removing the stronger 
of these two opposite poles a little way from the plate, the 
vibrations increased to thirty-one, or nearly the original num- 
ber. But on removing it altogether , they fell to between five 
and six. 

253. Nothing can be more clear, therefore, than that with 
iron, and bodies admitting of ordinary magnetic induction, 
opposite poles on opposite sides of the edge of. the plate neu- 
tralize each other's effect, whilst similar poles exalt the action ; 
a single pole end on is also sufficient. But with copper* and 
substances not sensible to ordinary magnetic impressions, simi* 
lar poles on opposite sides of the plate neutralize each other ; 
opposite poles exalt the action ; and a single pole at the edge 
or end on does nothing. 



Jan. 1832.] induction distinguished. 73 

254. Nothing can more completely show the thorough inde- 
pendence of the Effects obtained with the metals by Arago, and 
those due to ordinary magnetic forces ; and henceforth, there- 
fore, the application of two poles to various moving substances 
will, if they appear at all magnetically a fleeted, afford a proof 
of the nature of that affection. If opposite poles produce a 
greater effect than one pole, the result will be due to electric 
currents. If similar poles produce more effect than one, then 
the power is not electrical ; it is not like that active in the 
metals and carbon when they are moving, and in most cases 
will probably be found to be not even magnetical, but the re- 
sult of irregular causes not anticipated and consequently not 
guarded against. 

255. The result of these investigations tends to show that 
there are really but very few bodies that are magnetic in the 
manner of iron. I have often sought for indications of this 
power in the common metals and other substances ; and once 
in illustration of Aragons objection ( 82 .) , and in hopes of ascer- 
taining the existence of currents in metals by the momentary 
approach of a magnet, suspended a disc of copper by a single 
fibre of silk in an excellent vacuum, and approximated power- 
ful magnets on the outside of the jar, making them approach 
and recede in unison with a pendulum that vibrated as the disc 
would do : but no motion could be obtained ; not merely, no in- 
dication of ordinary magnetic powers, but none of any electric 
current occasioned in the metal by the approximation and re- 
cession of the magnet. I therefore venture to arrange sub- 
stances in three classes a*s regards their relation to magnets ; 
first, those which are affected when at rest, like iron, nickel, 
&c., being such as possess ordinary magnetic properties ; then, 
those which are affected when in motion, being conductors of 
electricity in which are produced electric currents by the in- 
ductive force of the magnet ; and, lastly, those which are per- 
fectly indifferent to the magnet, whether at rest or in motion. 

256. Although it will require further research, and probably 
close investigation, both experimental and mathematical, before 
the exact mode of action between a magnet and metal moving 
relatively to each other is ascertained ; yet many of the results 
appear sufficiently clear and simple to allow of expression in a 



74 Conditions of magneto-electric induction . [Series II. 

somewhat general manner. — 1£ a terminated wire move so as to 
xut a magnetic curve, a- power is called into action which tends 
to urge an electric current through it ; but this current cannot 
be brought into existence unless provision be made at the ends 
of the wire for its discharge and renewal. 

257. If a second wire move in the same direction as the first, 
the same power is exerted upon it, and it is therefore unable 
to alter the condition of the first : for there appear to be no 
natural differences among substances when connected in a 
series, by which, when moving under the same circumstances 
relative to the magnet, one tends to produce a more powerful 
electric current in the whole circuit than another (201. 214.). 

258. But if the second wire move with a different velocity, 
or in some other direction, then variation^ in the force exerted 
take place ; and if connected at their extremities, an electric 
current passes through them. 

259. Taking, then, a mass of metal or an endless wire, and 
referring to the pole of the magnet as a centre of action, (which 
though perhaps not strictly correct may be allowed for facility 
of expression, at present,) if all parts move in the same direc- 
tion, and with the same angular velocity, and through magnetic 
curves of constant intensity, then no electric currents are pro- 
duced. This point is easily observed with masses subject to 
the earths magnetism, and may be proved with regard to small 
magnets ; by rotating them, and leaving the metallic arrange- 
ments stationary, no current is produced. 

260. If one part of the wire or metal cut the magnetic curves, 
whilst the other is stationary, then currents are produced. All 
the results obtained with the galvanometer are more or less of 
this nature, the galvanometer extremity being the fixed part. 
Even those with the wire, galvanometer, and earth (170.) , may 
be considered so without any error in the result. 

261. If the motion of the metal be in the same direction, but 
the angular velocity of its parts relative to the pole of the mag- 
net different, then currents are produced. This is the case in 
Arago's experiment, and also in the wire subject to the earth's 
induction (172.), when it was moved from west to east-* 

262. If the magnet moves not directly to or from the ar- 
rangement, but laterally, then the case is similar to the last. 

263. If different parts move in opposite directions across 



Jan. 1832.] Conditions of magneto -electric induction . 75 

the magnetic curves, then the effect is a maximum for equal 
velocities. 

264. All these in fact are variations of one simple condition, 
namely, that all parts of the mass shall not move in the same 
direction across the curves, and with the same angular velocity. 
But they are forms of expression which, being retained in the 
mind, I have found useful when comparing the consistency of 
particular phenomena with general results. 

Royal Institution , 

December 21 , 1831 . 



76 


THIRD SERIES. 

§ 7. Identity of Electricities derived from different* sources , 
§ 8. Relation by measure of common and voltaic Electri- 
city. 

[Read January 10th and 17th, 1833,] 

§ 7. Identity of Electricities derived from different sources . 

265. The progress of the electrical researches which I have 
had the honour to present to the Royal Society, brought me 
to a point at which it was essential for tfye further prosecution 
of my inquiries that no doubt should remain of the identity or 
distinction of electricities excited by different means. It is per- 
fectly true that Cavendish*, Wollaston +, Colladon J, and others, 
have in succession removed some of the greatest objections to 
the acknowledgement of the identity of common, animal, and 
voltaic electricity, and I believe that most philosophers con- 
sider these electricities as really the same. But on the other 
hand it is also true, that the accuracy of Wollaston^s experi- 
ments have been denied § ; and also that one of them, which 
really is no proper proof of chemical decomposition by com- 
mon electricity (309. 327.), has been that selected by several 
experimenters as the test of chemical action (336. 346.) . It is 
a fact, too, than many philosophers are still drawing distinc- 
tions between the electricities of different sources ; or at 
least doubting whether their identity is proved. Sir Humphry 
JDavy, for instance, in his paper on the Torpedo ||, thought it 

* Phil. Trans. 1776, p. 196. t Ibid. 1801, p. 484, 

X Annales d© Chimie, 1826, p. 62, &c. § Phil, Trans. 1832, p. 282, note. 
j| Phil. Trans. 1829, p. 17, w Common electricity is excited upon non-con- 
ductors, and is readily carried off by conductors and imperfect conductors. 
Voltaic electricity is excited upon combinations of perfect and imperfect con- 
ductors, and is only transmitted by perfect conductors or imperfect conductors 
of the best kind. Magnetism, if it be a form of electricity, belongs only to per- 
fect conductors; and, in its modifications, to a peculiar class of them 1 . Animal 
electricity resides only in the imperfect conductors forming the organs of living 
animals, &c.” 

1 Dr. Ritchie has shown this is not the case, Phil. Trans, 1882, p. 294. 



77 


Jan. 1833.] Supposed diversity of electricities. 

probable that animal electricity would be found of a peculiar 
kind ; and referring to it, to common electricity, voltaic elec- 
tricity and magnetism, has said, “ Distinctions might be esta- 
blished in pursuing the various modifications or properties of 
electricity in these different forms, & c.” Indeed I need only 
refer to the last volume of the Philosophical Transactions 
to show that - the question is by no means considered as set- 
tled*. 

266. Notwithstanding, therefore, the general impression of 
the identity of electricities, it is evident that the proofs have 
not been sufficiently clear and distinct to obtain the assent of 
all those who were competent to consider the subject ; and the 
question seemed to me very much in the condition of that which 
Sir H. Davy solved so beautifully, — namely, whether voltaic 
electricity in all cases merely eliminated, or did not in some 
actually produce, the acid and alkali found after its action 
upon water. The same necessity that urged him to decide the 
doubtful point, which interfered with the extension of his views, 
and destroyed the strictness of his reasoning, has obliged me 
to ascertain the , identity or difference of common and voltaic 
electricity. I have satisfied myself that they arc identical, and 
I hope the experiments which I have to offer, and the proofs 
flowing from them, will be found worthy the attention of the 
Royal Society. 

* Phil. Trans. 1832, p. 259. Dr. Davy, in making experiments on the tor- 
pedo, obtains effects the same as those produced by common and voltaic elec- 
tricity, and says that in its magnetic and chemical power it does not seem to 
be essentially peculiar, — p. 274 ; but then he says, p. 275, there are other points 
of difference j and after referring to them, adds, “ IIow are these differences to 
be explained P Do they admit of explanation similar to that advanced by Mr. 
Cavendish in his theory of the torpedo j or may we suppose, accordingly the 
analogy of the solar ray, that the electrical power, whether excited by the com- 
mon machine, or by the voltaic battery, or by the torpedo, is not a simple 
power, but a combination of powers, which may occur variously associated, and 
produce all the varieties of electricity with which we are acquainted ?” 

At p. 279 of the same volume of Transactions is Dr. Ritchie’s* paper, from 
which the following are extracts : “Common electricity is diffused over the sur- 
face of the metal j — voltaic electricity exists within the metal. Free electricity 
is conducted over the surface of the thinnest gold leaf as effectually as over a 
mass of metal having the same surface ; — voltaic electricity requires thickness 
of metal for its conduction,” p. 280 : and again, “ The supposed analogy be- 
tween common and voltaic electricity, which was so eagerly traced after the 
invention of the pile, completely fails in this case, which was thought to afford 
the most striking resemblance.” p. 291. 



78 Identity of electricities. [Series III. 

267\ The various phenomena exhibited by electricity may, 
for the purpose of comparison, be arranged under two heads ; 
namely, those connected with electricity of tension, and those 
belonging to electricity in motion. This distinction is taken at 
present not as philosophical, but merely as convenient. The ef- 
fect of electricity of tension, at rest, is either attraction'or repul- 
sion at sensible distances. The effects of electricity in. motion or 
electrical currents may be considered as 1st, Evolution of heat ; 
2nd, Magnetism; 3rd, Chemical decomposition; 4th, Physio- 
logical phenomena ; 5th, Spark. It will be my object to compare 
electricities from different sources, and especially common and 
voltaic electricities, by their power of producing these effects. 

I. Voltaic 'Electricity . 

268. Tension . — When a voltaic battery of 100 pairs of plates 
has its extremities examined by the ordinary electrometer, it' is 
well known that they are found positive and negative, the gold 
leaves at the same extremity repelling each other, the gold 
leaves at different extremities attracting each other, even when 
half an inch or more of air intervenes. 

269. That ordinary electricity is discharged by points with 
facility through air; that it is readily transmitted through 
highly rarefied air ; and also through heated air, as for instance 
a flame ; is due to its high tension. I sought, therefore, for 
similar effects in the discharge of voltaic electricity, using as 
a test of the passage of the electricity either the galvanometer 
or chemical action produced by the arrangement hereafter to 
be described (312. 316.). 

270. The voltaic battery I had at my disposal consisted of 
140 pairs of plates four inches square, with double coppers. 
It w r as insulated throughout, and diverged a gold leaf electro- 
meter about one third of an inch. On endeavouring to dis- 
charge this battery by delicate points very nicely arranged and 
approximated, either in the air or in an exhausted, receiver, I 
could obtain no indications of a current, either by magnetic or 
chemical action. In this, however, was found no point of dis- 
cordance between voltaic and common electricity ; for when a 
Leyden battery (291.) was charged so as to deflect the gold 
leaf electrometer to the same degree, the points were found 
equally unable to discharge it with such effect as to produce 
either magnetic or chemical action. This was, not because 



79 


J an . 1833.] Voltaic electricity , — discharged by hot air. 

common electricity could not produce both these effects 
(307. 310.) > but because when of such low intensity the quan- 
tity required to make the effects visible (being enormously 
great (371. 375),) could not be transmitted in any reasonable 
time. In conjunction with the other proofs of identity here- 
after to b'e given, these effects of points also prove identity in- 
stead of difference between voltaic and common electricity. 

271. As heated air discharges common electricity with far 
greater facility than points, I hoped that voltaic electricity 
might in this way also be discharged. An apparatus was there- 
fore constructed (Plate III. fig. 46.), in which AB is an insu- 
lated glass rod upon which two copper wires, C, D, are fixed 
firmly ; to these wires are soldered two pieces of fine platina 
wire, the ends of which tire brought very close to each other at 
e , but without touching ; the copper wire C was connected with 
the' positive pole of a voltaic battery, and the wire D with a 
decomposing apparatus (312. 316.), from which the communi- 
cation was completed to the negative pole of the battery. In 
these experiments only two troughs, or twenty pairs of plates, 
were used. 

272. Whilst in the state described, no decomposition took 
place at the point «, but when the side of a spirit-lamp flame 
was applied to the two platina extremities at e, so as to make 
them bright red-hot, decomposition occurred ; iodine soon ap- 
peared at the point a, and the transference of electricity through 
the heated air was established. On raising the temperature 
of the points e by a blowpipe, the discharge was rendered still 
more free, and decomposition took place instantly. On re- 
moving the source of he$t, the current immediately ceased. 
On putting the ends of the wires very close by the side of and 
parallel to each other, but not touching, the effects were 
perhaps more readily obtained than before. On using a larger 
voltaic battery (270.), they were also more freely obtained. 

273. On removing the decomposing apparatus and interpo- 
sing a galvanometer instead, heating the points e as the needle 
would swing one way, and removing the heat during the time of 
its return (302.), feeble deflections were soon obtained: thus 
also proving the current through heated air ; but the instru- 
ment used was not so sensible under the circumstances as 
chemical action. 



80 Identity of electricities. [Series III. 

274. These effects, not hitherto known or expected under 
this form, are only cases of the discharge which takes place 
through air between the charcoal terminations of the poles of 
a powerful battery, when they are gradually separated after 
contact. Then the passage is through heated air exactly as 
with common electricity, and Sir H. Davy has recbrded that 
with the original battery of the Royal Institution this dis- 
charge passed through a space of at least four inches *. In 
the exhausted receiver the electricity would strike through 
nearly half an inch of space, and the combined effects of rare- 
faction and heat was such upon the inclosed air as to enable 
it to conduct the electricity through a space of six or seven 
inches. 

275. The instantaneous charge of a* Leyden battery by the 
poles of a voltaic apparatus is another proof of the tension, and 
also the quantity of electricity evolved by the latter. fl Sii 'H. 
Davy says +, “ When the two conductors from the ends of the 
combination were connected with a Leyden battery, one with 
the internal, the other with the external coating, the battery 
instantly became charged ; and on removing the wires and ma- 
king the proper connexions, either a shock or a spark could 
be perceived : and the least possible time of contact was suffi- 
cient to renew the charge to its full intensity.” 

276. In motion ; i. Evolution of Heat. — The evolution of 
heat in wires and fluids by the voltaic current is matter of ge- 
neral notoriety. 

2 77. ii. Magnetism. — No fact is better known to philoso- 
phers than the power of the voltaic current to deflect the 
magnetic needle, and to make magnets according to certain 
laws ; and no effect can be more distinctive of an electrical cur- 
rent. 

278. iii. Chemical decomposition. — The chemical powers of 
the voltaic current, and their subjection to certain laws , are 
also perfectly well known. 

279. iv. Physiological effects . — The power of the voltaic 
current, when strong, to shock and convulse the whole animal 
system, and when weak to affect the tongue and the eyes, is 
very characteristic. 

280. v. Spark . — The brilliant star of light produced by the 

* Elements of Chemical Philosophy, p. 153. t Ibid. p. 154. 



81 


Jan. 1833.] Nature of the electric current . 

\ 

discharge of a voltaic battery is known to all as the most beau- 
tiful light that maji can produce by art. 

281. That these effects may be almost infinitely varied, some 
being exalted whilst others are diminished, is universally ao»* 
knowledged j and yet without any doubt of the identity of cha- 
racter of the voltaic currents thus made to differ in their effect. 
The beautiful explication of these variations afforded by Ca- 
vendish's theory of quantity and intensity requires no support 
at present, as it is not supposed to be doubted. 

282. In consequence of the comparisons that will hereafter 
arise between wires carrying voltaic and ordinary electricities, 
and also because of certain views of the condition of a wire or 
any other conducting substance connecting the poles of a vol- 
taic apparatus, it will be necessary to give some definite ex- 
prCSsion r of what is called the voltaic current, in contradistinc- 
tion to any supposed peculiar state of arrangement, not pro- 
gressive, which the wire or the electricity within it may be sup- 
posed to assume. If two voltaic troughs P N, P' 1ST, fig. 42, 
be symmetrically arranged and insulated, and the ends N P' 
connected by a wire, over which a magnetic needle is sus- 
pended, the wire will exert no effect over the needle ; but imme- 
diately that the ends P N' arc connected by another wire, the 
needle will be deflected, and will remain so as long as the cir- 
cuit is complete. Now if the troughs merely act by causing a 
peculiar arrangement in the wire either of its particles or its 
electricity, that arrangement constituting its electrical and mag- 
netic state, then the wire N P' should be in a similar state of 
arrangement before P and N / were connected, to what it is 
afterwards, and should have deflected the needle, although 
less powerfully, perhaps to one half the extent which would 
result when the communication is complete throughout. But 
if the magnetic effects depend upon a current, then it is evi- 
dent why they could not be produced in any degree before 
the circuit was complete ; because prior to that no current 
could exist. 

283. By current , I mean anything progressive, whether it 
be a fluid of electricity, or two fluids moving in opposite direc- 
tions, or merely vibrations, or, speaking still more generally, 
progressive** forces. By arrangementj I understand a, local ad- 



82 Identity of electricities. [Series III. 

justment of particles, or fluids, or forces, not progressive. 
Many other reasons might be urged in support of the view of 
a current rather than an arrangement , but I am anxious to 
avoid stating unnecessarily what will occur to others at the 
moment. 

II. Ordinary Electricity . 

284. By ordinary electricity I understand that which can be 
obtained from the common machine, or from the atmosphere, 
br by pressure, or cleavage of crystals, or by a multitude of 
other operations ; its distinctive character being that of great 
intensity, and the exertion of attractive and repulsive powers, 
not merely at sensible but at considerable distances. 

285. Tension . The attractions and .repulsions at sensible 
distances, caused by ordinary electricity, are well known to be 
so powerful in certain cases, as to surpass, almost infinitely, 
the similar phenomena produced by electricity, otherwise ex- 
cited. But still those attractions and repulsions are exactly of 
the same nature as those already referred to under the head 
Tension , Voltaic electricity ( 268 .) ; and the difference in de- 
gree between them is not greater than often occurs between 
cases of ordinary electricity only. I think it will be unneces- 
sary to enter minutely into the proofs of the identity of this 
character in the two instances. They are abundant ; are ge- 
nerally admitted as good ; and lie upon the surface of the sub- 
ject : and whenever in other parts of the comparison I am 
about to draw, a similar case occurs, I shall content myself 
with a mere announcement of the similarity, enlarging only 
upon those parts where the great question of distinction or 
identity still exists. 

286. The discharge of common electricity through heated 
air is a well-known fact. The parallel case of voltaic electri- 
city has already been described (272, &c.) . 

287. In motion . i. Evolution of heat. — The heating power 
vof common electricity, when passed through wires or other sub- 
stances, is perfectly well known. The accordance between it 
and voltaic electricity is in this respect complete. Mr. Harris 
has constructed and described* a very beautiful and sensible 

* Philosophical Transactions, 1827, p. 18. Edinburgh Transactions, 1831 
Harris on a New Electrometer, <Sjc, &c. 



83 


Jan. 1833.] Magnetic effects of ordinary electricity. 

instrument on this principle, in which the heat produced in 
a wire by the discharge of a small portion of common electri- 
city is readily shown, and to which I shall have occasion to 
refer for experimental proof in a future part of this paper 
(344.). 

288. il. Magnetism . — Voltaic electricity has most extraordi- 
nary and exalted magnetic powers. If common electricity be 
identical with it, it ought to have the same powers. In ren- 
dering needles or bars magnetic, it is found to agree with vol- 
taic electricity, and the direction of the magnetism, in both 
cases, is the same ; but in deflecting the magnetic needle, com- 
mon electricity has been found deficient, so that sometimes its 
power has been denied altogether, and at other times distinc- 
tions have been hypothetically assumed for the purpose of 
avoiding the difficulty*. 

289. M. Colladon, of Geneva, considered that the differ- 
ence might be due to the use of insufficient quantities of com- 
mon electricity in all the experiments before made on this head ; 
and in a memoir read to the Academic dcs Sciences in 1826 f, 
describes experiments, in which, by the use of a battery, points, 
and a delicate galvanometer, jie succeeded in obtaining de- 
flections, and thus establishing identity in that respect. MM. 
Arago, Ampere, and Savary, are mentioned in the paper as 
having witnessed a successful repetition of the experiments. 
But as no other one has come forward in confirmation, MM. 
Arago, Ampere, and Savary, not having themselves published 
(that I am aware of) their admission of the results, and as some 
have not been able to obtain them, M. Col lad on's conclusions 
have been occasionally doubted or denied; and an important 
point with me was to establish their accuracy, or remove them 
entirely from the body of received experimental research. I 
am happy to say that my results fully confirm fjiosc by M. 
Colladon, and I should have had no occasion to describe them, 
but that they are essential as proofs of the accuracy of the 
final and general conclusions I am enabled to draw respecting 
the magnetic and chemical action of electricity, (360. 366. 367. 
377. See.). 

290. The plate electrical machine I have used is fifty inches 

* Demonferrand’s Manuel d’Electricitd dynamique, p. 121, 

t Annates de Ckimie, xxxiii. p. 62. 

o 2 



84? Identity of electricities. [Series III, 

in diameter ; it has two sets of rubbers ; its prime conductor 
consists of two brass cylinders connected by ft third, the whole 
length being twelve feet, and the surface in contact with air 
about 1422 square inches. When in good excitation, one re- 
volution of the plate will give ten or twelve sparks from the 
conductors, each an inch in length. Sparks or flashes from 
ten to fourteen inches in length may easily be drawn from the 
conductors. Each turn of the machine, when worked mode- 
rately, occupies about '^ths of a second. 

291. The electric battery consisted of fifteen equal jars. 
They are coated eight inches upwards from the bottom, and 
are twenty-three inches in circumference, so that each con- 
tains one hundred and eighty-four square inches of glass, 
coated on both sides ; this is independent of the bottoms, 
which are of thicker glass, and contain each about fifty square 
inches. 

292. A good discharging train was arranged by connecting 
metallically a sufficiently thick wire with the metallic gas pipes 
of the house, with the metallic gas pipes belonging to the pub- 
lic gas works of London; and also with the metallic water 
pipes of London. It was so effectual in its office as to carry 
off instantaneously electricity of the feeblest tension, even that 
of a single voltaic trough, and was essential to many of the 
experiments. 

293. The galvanometer was one or the other of those for- 
merly described (87. 205.), but the glass jar covering it and 
supporting the needle was coated inside and outside with tin- 
foil, and the upper part (left uncoated, that the motions of the 
needle might be examined,) was covered with a frame of wire- 
work, having numerous sharp points projecting from it. When 
this frame and the two coatings were connected with the dis- 
charging train (292.), an insulated point or ball, connected 
with the machine when most active, might be brought within 
an inch of any part of the galvanometer, yet without affecting 
the needle within by ordinary electrical attraction or repulsion. 

294. In connexion with these precautions it may be neces- 
sary to state that the needle of the galvanometer is very liable 
to have its magnetic power deranged, diminished, or even in- 
verted by the passage of a shock through the instrument. If 
the needle be at all oblique, in the wrong direction, to the coils 



Jan. 1833.] Magnet deflected by ordinary electricity . 85 

of the galvanometer when the shock passes, effects of this 
kind are sure to happen. 

295. It was to the retarding power of bad conductors, with 
the intention of diminishing its intensity without altering its 
quantity, that I first looked with the hope of being able to 
make common electricity assume more of the characters and 
power of- voltaic electricity, than it is usually supposed to 
ha%e. 

296. The coating and armour of the galvanometer were first 
connected with the discharging train (292.) ; the end B (87.) 
of the galvanometer wire was connected with the outside coat- 
ing of the battery, and then both these with the discharging 
train ; the end A of the galvanometer wire was connected with 
a discharging rod by a wet thread four feet long; and, finally, 
wl^cn the battery (291.) had been positively charged by about 
forty ttirns of the machine, it was discharged by the rod and 
the thread through the galvanometer. The needle immediately 
moved. 

297. During the time that the needle completed its vibration 
in the first direction, and returned, the machine was worked, 
and the battery recharged; and when the needle in vibrating 
resumed its first direction, the discharge was again made 
through the galvanometer. By repeating this action a few 
times, the vibrations soon extended to above 40° on each side 
of the line of rest. 

298. This effect could be obtained at pleasure. Nor was 
it varied, apparently, either in direction or degree, by using a 
short thick string, or even four short thick strings in place of 
the long fine thread. With a more delicate galvanometer, an 
excellent swing of the needle could be obtained by one dis- 
charge of the battery. 

299. On reversing the galvanometer communications so as 
to pass the discharge through from B to A, the needle was 
equally well deflected, but in the opposite direction. 

300. The deflections were in the same direction as if a vol- 
taic current had been passed through the galvanometer, i. e . 
the positively charged surface of the electric battery coincided 
with the positive end of the voltaic apparatus (268.), and the 
negative surface of the former with the negative end of the 
latter# 



86 Identity of electricities. [Series III. 

301. The battery was then thrown out of^use, and the com* 
munications so arranged that the current could be passed from 
the prime conductor, by the discharging rod held against it, 
through the wet string, through the galvanometer coil, and 
into the discharging train (292.), by which it was finally di- 
spersed. This current could be stopped at any moment by 
removing the discharging rod, and either stopping the machine 
or connecting the prime conductor by another rod with the dis- 
charging train ; and could be as instantly renewed. The nee- 
dle was so adjusted, that whilst vibrating in moderate and small 
arcs, it required time equal to twenty-five beats of a watch to 
pass in one direction through the arc, and of course an equal 
time to pass in the other direction. 

302. Thus arranged, and the needle being stationary, the 
current, direct from the machine, was sent through the gal- 
vanometer for twenty-five beats, then interrupted for other 
twenty-five beats, renewed for twenty-five beats more, again 
interrupted for an equal time, and so on continually. The 
needle soon began to vibrate visibly, and after several alterna- 
tions of this kind the vibration increased to 40° or more. 

303. On changing the direction of the current through the 
galvanometer, the direction of the deflection of the needle was 
also changed. In all cases the motion of the needle was in di- 
rection the same as that caused either by the use of the elec- 
tric battery or a voltaic trough (300.). 

304. I now rejected the wet string, and substituted a cop- 
per wire, so that the electricity of the machine passed at once 
into wires communicating directly with the discharging train, 
the galvanometer coil being one of the wires used for the dis- 
charge. The effects were exactly those obtained above (302.) . 

305. Instead of passing the electricity through the system, 
by bringing the discharging rod at the end of it into contact 
with the conductor, four points were fixed on to the rod ; when 
the current was to pass they were held about twelve inches 
from the conductor, and when it was not to pass, they were 
turned away. Then operating as before (302.), except with 
this variation, the needle was soon powerfully deflected, and 
in perfect consistency with the former results. Points afforded 
the means by which Colladon, in all cases, made his discharges. 

306. Finally, I passed the electricity first through an ex- 



87 


Jan. 1833.] Chemical effects of common electricity . 

hausted receiver, so as to make it there resemble the aurora 
borealis, and then through the galvanometer to the earth ; and 
it was found still effective in deflecting the needle, and appa- 
rently with the same force as before. 

307. From all these experiments, it appears that a current 
of common electricity, whether transmitted through water or 
metal, or rarefied air, or by means of points in common air, is 
still^able to deflect the needle ; the only requisite being, appa- 
rently, to allow time for its action : that it is, in fact, just as 
magnetic in every respect as a voltaic current, and that in this 
character therefore no distinction exists. 

308. Imperfect conductors, as water, brine, acids, &c. &c. 
will be found far more convenient for exhibiting these effects 
than other modes of discharge, as by points or balls ; for the 
former convert at once the charge of a powerful battery into a 
feeble spark discharge, or rather continuous current, and in- 
volve little or no risk of deranging the magnetism of the nee- 
dles (294.). 

309. iii. Chemical decomposition . — The chemical action of 
voltaic electricity is characteristic of that agent, but not more 
characteristic than are the laws under which the bodies 
evolved by decomposition arrange themselves at the poles. 
Dr. Wollaston showed* that common electricity resembled it in 
these effects, and “ that they are both essentially the same”; but 
he mingled with his proofs an experiment having a resemblance, 
and nothing more, to a case of voltaic decomposition, which 
however he himself partly distinguished ; and this has been 
more frequently referred to by some, on the one hand, to prove 
the occurrence of electrochemical decomposition, like that of 
the pile, and by others to throw doubt upon the whole paper, 
than the more numerous and decisive experiments which he 
has detailed. 

310. I take the liberty of describing briefly my results, and 
of thus adding my testimony to that of Dr. Wollaston on the 
identity of voltaic and common electricity as to chemical action, 
not only that I may facilitate the repetition of the experiments, 
but also lead to some new consequences respecting electro- 
chemical decomposition (376. 377.) . 

311. I first repeated Wollaston's fourth experiment f, in 

* Philosophical Transactions, 1801, p. 427, 434. t Ibid. 1801, p. 429. 



88 Identity of electricities. [Series III. 

which the ends of coated silver wires are immersed in a drop 
of sulphate of copper. By passing the electricity of the ma- 
chine through such an arrangement, that end in the drop which 
received the electricity became coated with metallic copper. 
One hundred turns of the machine produced an evident effect ; 
two hundred turns a very sensible one. The decomposing ac- 
tion was however very feeble. Very little copper w,as precipi- 
tated, and no sensible trace of silver from the other pole ap- 
peared in the solution. 

312. A much more convenient and effectual arrangement for 
chemical decompositions by common electricity, is the following. 
Upon a glass plate, fig. 43, placed over, but raised above a 

. piece of white paper, so that shadows may not interfere, put 
two pieces of tinfoil a , b ; connect one of these by an insulated 
wire c, or wire and string (301.), with the machine, and the other 
y , witli the discharging train (292.) or the negative conductor ; 
provide two pieces of fine platina wire, bent as in fig. 44, so 
that the part d } f shall be nearly upright, whilst the whole is 
resting on the three bearing points p, e,f; place these as in 
fig. 43 ; the points p , n then become the decomposing poles. In 
this way surfaces of contact, as minute as possible, can be ob- 
tained at pleasure, and the connexion can be broken or renewed 
in a moment, and the substances acted upon examined with 
the utmost facility. 

313. A coarse line was made on the glass with solution of 
sulphate of copper, and the terminations p and n put into it ; 
the foil a w r as connected with the positive conductor of the ma- 
chine by wire and wet string, so that no sparks passed : twenty 
turns of the machine caused the precipitation of so much copper 
on the end n , that it looked like copper wire; no apparent 
change took place at p. 

314. A mixture of equal parts of muriatic acid and water 
was rendered deep blue by sulphate of indigo, and a large drop 
put on the glass, fig. 43, so that p and n were immersed at op- 
posite sides : a single turn of the machine showed bleaching 
effects round p } from evolved chlorine. After twenty revolu- 
tions no effect of the kind was visible at n , but so much chlorine 
had been set free at p , that when the drop was stirred the 
whole became colourless. 

315. A drop of solution of iodide of potassium mingled with 



89 


Jan. 1833.] Chemical action by ordinary electricity. 

starch was put into the same position at p and n ; on turning 
the machine, iodine was evolved at p } but not at n . 

316. A still further improvement in this form of apparatus 
consists in wetting a piece of filtering paper in the solution to 
be experimented on, and placing that imder the points p and n, 
on the glass : the paper retains the substance evolved at the 
point of eyolution, by its whiteness renders any change of 
colour visible, and allows of the point of contact between it and 
the decomposing wires being contracted to the utmost degree. 
A piece of paper moistened in the solution of iodide of potas- 
sium and starch, or of the iodide alone, with certain precautions 
(322.) , is a most admirable test of electro-chemical action ; and 
when thus placed and acted upon by the electric current, will 
show iodide evolved at* p by only half a turn of the machine. 
With these adjustments and the use of iodide of potassium 
on pape#, chemical action is sometimes a more delicate test of 
electrical currents than the galvanometer (273.). Such cases 
occur when the bodies traversed by the current are bad con- 
ductors, or when the quantity of electricity evolved or transmit- 
ted in a given time is very small. 

317. A piece of litmus paper moistened in solution of com- 
mon salt of sulphate of soda, was quickly reddened at p. A 
similar piece moistened in muriatic acid was very soon bleached 
at p. No effects of a similar kind took place at n. 

318. A piece of turmeric paper moistened in solution of sul- 
phate of soda was reddened at n by two or three turns of the 
machine, and in twenty or thirty turns plenty of alkali was 
there evolved. On turning the paper round, so that the spot came 
under p f and then working the machine, the alkali soon disap- 
peared, the place became yellow, and a brown alkaline spot 
appeared in the new part under n. 

, 319. On combining a piece of litmus with a piece of turme- 
ric paper, wetting both with solution of sulphate of soda, and 
putting the paper on the glass, so that p was on the litmus and 
n on the turmeric, a very few turns of the machine sufficed to 
show the evolution of acid at the former and alkali at the latter, 
exactly in the manner effected by a volta-electric current. 

320. All these decompositions took place equally well, 
whether the electricity passed from the machine to the foil «, 
through water, or through wire only ; by contact with the con- 



90 Identity of electricities. [Series III. 

ductor, or by sparks there ; provided the sparks were not so 
large as to cause the electricity to pass in %parks from p to n 9 
or towards n; and I have seen no reason to believe that in 
cases of true electro-chemical decomposition by the machine, 
the electricity passed in sparks from the conductor, or at any 
part of the current, is able to do more, because of its tension, 
than that which is made to pass merely as a regular current. 

321. Finally, the experiment was extended into the following 
form, supplying in this case the fullest analogy between com- 
mon and voltaic electricity. Three compound pieces of litmus 
and turmeric paper (319.) were moistened in solution of sul- 
phate of soda, and arranged on a plate of glass with platina 
wires, as in fig. 45. The wire wiwas connected with the prime 
conductor of the machine, the wire t wifh the discharging train, 
and the wires r and s entered into the course of the electrical 
current by means of the pieces of moistened paper ; they were 
so bent as to rest each on three points, n y r, p ; n y s, p y the 
points r and s being supported by the glass, and the others 
by the papers : the three terminations p , p y p rested on 
the litmus, and the other three n y n } n on the turmeric 
paper. On working the machine for a short time only, acid 
was evolved at all the poles or terminations p y p y p y by which 
the electricity entered the solution, and alkali at the other 
poles, n y n y n y by which the electricity left the solution. 

322. In all experiments of electro-chemical decomposition by 
the common machine and moistened papers (316.), it is neces- 
sary to be aware of and to avoid the following important source 
of error. If a spark passes over moistened litmus and turmeric 
paper, the litmus paper (provided it be delicate and not too al- 
kaline,) is reddened by it ; and if several sparks are passed, it 
becomes powerfully reddened. If the electricity pass a little 
way from the wire over the surface of the moistened paper, 
before it finds mass and moisture enough to conduct it, then 
the reddening extends as far as the ramifications. If similar 
ramifications occur at the termination n y on the turmeric paper, 
they prevent the occurrence of the red spot due to the alkali, 
which would otherwise collect there : sparks or ramifications 
from the points n will also redden litmus paper. If paper 
moistened by a solution of iodide of potassium (which is an ad- 
mirably delicate test of electro-chemical action,) be exposed to 



91 


Jan. 1833.] Effect of electric sparks on air . 

the sparks or ramifications, or even a feeble stream of electricity 
through the air fronf either the point p or n y iodine will be im- 
mediately evolved. 

323. These effects must not be confounded with those due 
to the true electro-chemical powers of common electricity, and 
must be carefully avoided when the latter are to be observed. 
No sparks should be passed, therefore, in any part of the cur- 
rent, por any increase of intensity allowed, by which the elec- 
tricity may be induced to pass between the platina wires and 
the moistened papers, otherwise than by conduction ; for if it 
burst through the air, the effect referred to above (322.) ensues. 

324. The effect itself is due to the formation of nitric acid 
by the combination of the oxygen and nitrogen of the air, and 
is, in fact, only a delicate repetition of Cavendish's beautiful 
experiment. The acid so formed, though small in quantity, is 
in a high state of concentration as to water, and produces the 
consequent effects of reddening the litmus paper ; or preventing 
the exhibition of alkali on the turmeric paper ; or, by acting on 
the iodide of potassium, evolving iodine. 

325. By moistening a very small slip of litmus paper in solu- 
tion of caustic potassa, and then passing the electric spark over 
its length in the air, I gradually neutralized the alkali, and ulti- 
mately' rendered the paper red ; on drying it, I found that ni- 
trate of potassa had resulted from the operation, and that the 
paper had become touch paper. 

326. Either litmus paper or white paper, moistened in a 
strong solution of iodide of potassium, offers therefore a very 
simple, beautiful, and ready means of illustrating Cavendish's 
experiment of the formation of nitric acid from the atmosphere. 

327. I have already had occasion to refer to an experiment 
(265. 309.) made by Dr. Wollaston, which is insisted upon too 
much, both by those who oppose and those who agree with the 
accuracy of his views respecting the identity of voltaic and or- 
dinary electricity. By covering fine wires with glass or other 
insulating substances, and then removing only so much matter 
as to expose the point, or a section of the wires, and by passing 
electricity through two such wires, the guarded points of which 
were immersed in water, Wollaston found that the water could 
be decomposed even by the current from the machine, without 
sparks, and that two streams of gas arose from the points. 



92 Identity of electricities. [Series III, 

exactly resembling, in appearance, those prdduced by voltaic 
electricity, and, like the latter, giving a mixture of oxygen and 
hydrogen gases. But Dr. Wollaston himself points out that 
the effect is different from that of the voltaic pile, inasmuch as 
both oxygen and hydrogen are evolved from each pole ; he calls 
it “ a very close imitation of the galvanic phenomena,” but adds 
that “ in fact the resemblance is not complete,” jand does not 
trust to it to establish the principles correctly laid down in his 
paper. 

328. This experiment is neither more nor less than a re- 
petition, in a refined manner, of that made by Dr. Pearson in 
1797*, and previously by MM. Pacts Van Troostwyk and 
Deiman in 1789 or earlier. That the experiment should never 
be quoted as proving true electro-chemical decomposition, is 
sufficiently evident from the circumstance, that the law which 
regulates the transference and final place of the evolved bodies 
(278. 309.) has no influence here. The water is decomposed at 
both poles independently of each other, and the oxygen and 
hydrogen evolved at the wires are the elements of the water 
existing the instant before in those places. That the poles, or 
rather points, have no mutual decomposing dependence, may be 
shown by substituting a wire, or the finger, for one of them, a 
change which does not at all interfere with the other, though it 
stops all action at the changed pole. This fact may be ob- 
served by turning the machine for some time ; for though bub- 
bles will rise from the point left unaltered, in quantity sufficient 
to cover entirely the wire used for the other communication, if 
they could be applied to it, yet not a single bubble will appear 
on that wire. 

329. When electro-chemical decomposition takes place, there 
is great reason to believe that the quantity of matter decom- 
posed is not proportionate to the intensity, but to the quan- 
tity of electricity passed (320.) . Of this I shall be able to offer 
some proofs in a future part of this paper (375. 377.). But in 
the experiment under consideration, this is not the case. If, 
with a constant pair of points, the electricity be passed from 
the machine in sparks, a certain proportion of gas is evolved ; 
but if the sparks be rendered shorter, less gas is evolved ; and 
if no sparks be passed, there is scarcely a sensible portion of 

* Nicholson’s Journal, 4to. vol. 1. pp. 241, 299, 349, 



Jan. 1833.] Wollaston's water-decomposition experiment . 93 

gases set free. On substituting solution of sulphate of soda for 
water, scarcely a sensible quantity of gas could be procured even 
with powerful sparks, and nearly none with the mere current ; 
yet the quantity of electricity in a given time was the same in 
all these cases. 

330. I do not intend to deny that with such an apparatus 
common electricity can decompose water in a manner analogous 
to that*of the voltaic pile ; I believe at present that it can. But 
when what I consider the true effect only was obtained, the 
quantity of gas given off was so small that I could not ascertain 
whether it was, as it ought to be, oxygen at one wire and hy- 
drogen at the other. Of the two streams one seemed more 
copious than the other, and on turning the apparatus round, 
still the same side in relation to the machine gave the largest 
stream. On substituting solution of sulphate of soda for pure 
water (32$.), these minute streams were still observed. But 
the quantities were so small, that on working the machine for 
half an hour I could not obtain at either pole a bubble of gas 
larger than a small grain of sand. If the conclusion which I 
have drawn (377.) relating to the amount of chemical action be 
correct, this ought to be the case. 

331. I have been the more anxious to assign the true value of 
this experiment as a test of electro-chemical action, because I 
shall have occasion to refer to it in cases of supposed chemical 
action by magneto-electric and other electric currents (336. 
346.) and elsewhere. But, independent of it, there cannot be 
now a doubt that Dr. Wollaston was right in his general con- 
clusion ; and that voltaic and common electricity have powers 
of chemical decomposition, .alike in their nature, and governed 
by the same law of arrangement. 

332. iv. Physiological effects . — The power of the common 
electric current to shock and convulse the animal system, and 
when weak to affect the tongue and the eyes, may be considered 
as the same with the similar power of voltaic electricity, account 
being taken of the intensity of the one electricity and duration 
of the other. When a wet thread was interposed in the course 
of the current of common electricity from the battery (291.) 
charged by eight or ten* revolutions of the machine in good 
action (290.) and the discharge made by platina spatulas 
through the tongue or the gums, the effect upon the tongue 

* Or even from thirty to forty. 



94 Identity of electricities. [Series III. 

and eyes was exactly that of a momentary feeble voltaic 
circuit. 

333. v. Spark . — The beautiful flash of light attending the 
discharge of common electricity is well known. It rivals in 
brilliancy, if it does not even very much surpass, the light from 
the discharge of voltaic electricity; but it endures for an instant 
only, and is attended by a sharp noise like that of a small ex- 
plosion. Still no difficulty can arise in recognizing it to* be the 
same spark as that from s the voltaic battery, especially under 
certain circumstances. The eye cannot distinguish the differ- 
ence between a voltaic and a common electricity spark, if they 
be taken between amalgamated surfaces of metal, at intervals 
only, and through the same distance of air. 

334. When the Leyden battery • (291.) was discharged 
through a wet string placed in some part of the circuit away 
from the place where the spark was to pass, the spark was yel- 
lowish, flamy, having a duration sensibly longer than if the 
water had not been interposed, was about three-fourths of an 
inch in length, was accompanied by little or no noise, and whilst 
losing part of its usual character had approximated in some de- 
gree to the voltaic spark. When the electricity retarded by 
water was discharged between pieces of charcoal, it was exceed- 
ingly luminous and bright upon both surfaces of the charcoal, 
resembling the brightness of the voltaic discharge on such 
surfaces. When the discharge of the unretarded electricity 
was taken upon charcoal, it was bright upon both the surfaces, 
(in that respect resembling the voltaic spark,) but the noise 
was loud, sharp, and ringing. 

335. I have assumed, in accordance, I believe, with the 
opinion of every other philosopher, that atmospheric electricity 
is of the same nature with ordinary electricity (284.), and I 
might therefore refer to certain published statements of chemi- 
cal effects produced by the former as proofs that the latter en- 
joys the power of decomposition in common with voltaic elec- 
tricity. But the comparison I am drawing is far too rigorous 
to allow me to use these statements without being fully assured 
of their accuracy ; yet I have no right to suppress them, be- 
cause, if accurate, they establish what I am labouring to put 
on an undoubted foundation, and liave priority to my results. 

336. M, Bonijol of Geneva* is said to have constructed 

* Bibliothfcque Umverselle, 1830, tome xlv. p. 213. 



Jan. 1833.] Decomposition by atmospheric electricity . 95 

very delicate apparatus for the decomposition of water by com- 
mon electricity. By 0 connecting an insulated lightning rod with 
his apparatus, the decomposition of the water proceeded in a 
continuous and rapid manner even when the electricity of the 
atmosphere was not very powerful. The apparatus is not de- 
scribed j but as the diameter of the wire is mentioned as very 
small, it appears to have been similar in construction to that of 
Wollaston (327.) ; and as that does not furnish a case of true 
polar “electro- chemical decomposition (328.) , this result of M. 
Bonijol does not prove the identity in chemical action of com- 
mon and voltaic electricity. 

337. At the same page of the Bibliothfcque Universelle, M. 
Bonijol is said to have decomposed potash , and also chloride of 
silver by putting them into very narrow tubes and passing elec- 
tric sparks from an ordinary machine over them. It is evident 
that *thesp offer no analogy to cases of true voltaic decompo- 
sition, where the electricity only decomposes when it is con- 
ducted by the body acted upon, and ceases to decompose, 
according to its ordinary laws, when it passes in sparks. These 
effects are probably partly analogous to that which takes place 
with water in Pearson's or Wollaston's apparatus, and may be 
due to very high temperature acting on minute portions of mat- 
ter ; or they may be connected with the results in air (322.) . 

As nitrogen can combine directly with oxygen under the in- 
fluence of the electric spark (321.), it is not impossible that it 
should even take it from the potassium of the potash, especially 
as there would be plenty of potassa in contact with the acting 
particles to combine with the nitric acid formed. However dis- 
tinct all these actions may be from true polar electro- chemical 
decompositions, they are still highly important, and well worthy 
of investigation. 

338. The late Mr. Barry communicated a paper to the Boyal 
Society* last year, so distinct in the details, that it would seem 
at once to prove the identity in chemical action of common and 
Voltaic electricity ; but r when examined, considerable difficulty 
arises in reconciling certain of the effects with the remainder. 
He used two tubes, each having a wire within it passing through 
the closed end, as is usual for voltaic decompositions. The 
tubes were filled with solution of sulphate of soda, coloured 
with syrup of violets, and connected by a portion of the same 
* Philosophical Transactions, 1831, p. 166. 



96 Identity of electricities . [Series III. 

solution, in the ordinary manner ; the wire in one tube was 
connected by a gilt thread with the string pf an insulated elec- 
trical kite, and the, wire in the other tube by a similar gilt thread 
with the ground. Hydrogen soon appeared in the tube con- 
nected with the kite, and oxygen in the other, and in ten 
minutes the liquid in the first tube was green from the alkali 
evolved, and that in the other red from free acid produced. The 
only indication of the strength or intensity of the atmospheric 
electricity is in the expression, “ the usual shocks were ffelt on 
touching the string.” 

339. That the electricity in this case does not resemble that 
from any ordinary source of common electricity, is shown by 
several circumstances. Wollaston could not effect the decom- 
position of water by such an arrangement, and obtain the gases 
in separate vessels, using common electricity ; nor have any of 
the numerous philosophers, who have employed sucfy an appa- 
ratus, obtained any such decomposition, either of water or of a 
neutral salt, by the use of the machine. I have lately tried the 
large machine (290.) in full action for a quarter of an hour, 
during which time seven hundred revolutions were made, with- 
out producing any sensible effects, although the shocks that it 
would then give must have been far more powerful and nume- 
rous than could have been taken, with any chance of safety, 
from an electrical kite- string ; and by reference to the compari- 
son hereafter to be made (371.), it will be seen that for common 
electricity to have produced the effect, the quantity must have 
been awfully great, and apparently far more than could have 
been conducted to the earth by a gilt thread, and at the same 
time only have produced the “ usual shocks .” 

340. That the electricity was apparently not analogous to 
voltaic electricity is evident, for the usual shocks ” only were 
produced, and nothing like the terrible sensation due to a vol- 
taic battery, even when it has a tension so feeble as not to strike 
through the eighth of an inch of air. 

341. It seems just possible that the air which was passing 
by the kite and string, being in an electrical state sufficient to 
produce the “ usual shocks ” only, could still, when the elec- 
tricity was drawn off below, renew the charge, and so continue 
the current. The string was 1500 feet long, and contained two 
double threads. But when the enormous quantity which must 
have been thus collected is considered (371 . 376.) , the expla- 



Jan. 1833.] Identity of electricities.' 97 

nation seems very doubtful. I charged a voltaic battery of 
twenty pairs of places four indhes square with double coppers 
very strongly, insulated it, connected its positive extremity with 
the discharging train (292.), and its negative pole with an appa- 
ratus like that qf Mr. Barry, communicating by a wire inserted 
three inches into the wet soil of the ground. This battery 
thus arranged produced feeble decomposing effects, as nearly 
as I ceukl judge answering the description Mr. Barry has given. 
Its intensity was, of course, far lower than the electricity of the 
kite string, but the supply of quantity from the discharging 
train was unlimited. It gave no shocks to compare with the 
(( usual shocks 99 of a kite-string. 

342. Mr. Barry's experiment is a very important one to repeat 
and verify. If confirmed, it will be, as far as I am aware, the 
first recorded case of true electro- chemical decomposition of 
water by^common electricity, and it will supply a form of elec- 
trical current, which, both in quantity and intensity, is exactly 
intermediate with those of the common electrical machine and 
the voltaic pile. 

III. Magneto-Electricity . 

313. Tension. — The attractions and repulsions due to the 
tension of ordinary electricity have been well observed with 
that evolved by magneto-electric induction. M. Pixii, by using 
an apparatus, clever in its construction and powerful in its ac- 
tion*, was able to obtain great divergence of the gold leaves 
of an electrometer f. 

344. In motion : i. Evolution of Heat. — The current pro- 
duced by magneto -electric induction can heat a wire in the 
manner of ordinary electricity. At the British Association of 
Science at Oxford, in June of the present year, I had the 
pleasure, in conjunction with Mr. Harris, Professor Daniell, 
Mr. Duncan, and others, of making an experiment, for which 
the great magnet, in the museum, Mr. Harris's new electro- 
meter (287.), and the magneto-electric coil described in my first 
paper (34.), were put in requisition. The latter had been mo- 
dified in the manper I have elsewhere described J, so as to pro- 
duce an electric spark when its contact with the magnet was made 

* Annales de Chimie, 1, p. 322, t Ibid. li. p. 77. 

I Phil. Mag, and Annals, 1832, vol. xi. p. 405. 



98 Identity of electricities. [Series III. 

or broken. The terminations of the spiral, adjusted so as to 
have their contact with each other broken ^hen the spark was 
to pass, were connected with the wire in the electrometer, and 
it was found that each time the magnetic contact was made 
and broken, expansion of the air within the instrument occur- 
red, indicating an increase, at the moment, of the temperature 
of the wire. 

345. ii. Magnetism . — These currents were discovered by 
their magnetic power. 

346. iii. Chemical decomposition. — I have made many en- 
deavours to effect chemical decomposition by magneto- electri- 
city, but unavailingly. In July last I received an anonymous 
letter (which has since been published*,) describing a magneto- 
electric apparatus, by which the decomposition of water w r as 
effected. As the term “ guarded points 3> is used, I suppose 
the apparatus to have been "Wollaston's (327. &c.), in, which 
case the results did not indicate polar electro-chemical decom- 
position. Signor Botto has recently published certain results 
which he has obtained +; but they are, as at present described, 
inconclusive. The apparatus he used was 'apparently that of 
Dr. Wollaston, which gives only fallacious indications (327. 
&c.) . As magneto- electricity can produce sparks, it would be 
able to show the effects proper to this apparatus. The appa- 
ratus of M. Pixii already referred to (343s) has however, in the 
hands of himself % and M. Hachette§, given decisive chemi- 
cal results, so as to complete this link in the chain of evidence. 
Water was decomposed by it, and the oxygen and hydrogen 
obtained in separate tubes according to the law governing 
volta-electric and machine-electric decomposition. 

- 347. iv. Physiological effects. — A frog was convulsed in the 
earliest experiments on these currents (56.). The sensation 
upon the tongue, and the flash before the eyes, which I at first 
Obtained only in a feeble degree (56.) , have been since exalted 
by more powerful apparatus, so as to become even disagree- 
able. 

348. v. Spark . — The feeble spark which I first obtained with 
these currents (32.), has been varied and strengthened by Sig- 

• Bond, and Edin. Phil. Mag. and Joum, 1832, vol. i. p. 161. 

t Ibid. 1832, vol. i. p. 441. ' 1 Annales de Chimie, li. p. 77. 

§ Ibid. li. p. 72. 



Jan. 1833.] Identity of electricities, 99 

nori Nobili and Antinori, and others, so as to leave no doubt 
as to its identity with the common electric spark. 

IV. Thermo-Electricity , 

349. With regard to thermo-electricity, (that beautiful form 
of electricity discovered by Seebeek,) the very conditions under 
which it is excited are such as to give no ground for expecting 
that ft can be raised like common electricity to any high degree 
of tension ; the effects, therefore, due to that state arc not to 
be expected. The sura of evidence respecting its analogy to 
the electricities already described, is, I believe, as follows : — 
Tension, The attractions and repulsions due to a certain de- 
gree of tension have not been observed. In currents : i. Evo- 
lution of Heat. I am hot aware that its power of raising tem- 
perature has been observed, ii. Magnetism. It was discovered, 
and is best recognised, by its magnetic powers, iii. Chemical 
decomposition has not been effected by it. iv. Physiological 
effects. Nobili has shown * that these currents arc able to 
cause contractions in the limbs of a frog. v. Spark. The spark 
has not yet been seen. 

350. Only those effects are weak or deficient which depend 
upon a certain high degree of intensity ; and if common elec- 
tricity be reduced in that quality to a similar degree with the 
thermo-electricity, it can produce no effects beyond the latter. 

Y. Animal Electricity. 

351. After an examination of the experiments of Walsh f, 
IngenhouszJ, Cavendish §, Sir H. Davy||, and Dr. Davy 1 ^, no 
doubt remains on my mind, as to the identity of the electricity of 
the torpedo with common and voltaic electricity; and I presume 
that so little will remain on the minds of others as to justify my 
refraining from entering at length into the philosophical proofs 
of that identity. The doubts raised by Sir H. Davy have 
been removed by his brother Dr. Davy ; the results of the lat- 
ter being the reverse of those of the former. At present the 
sum of evidence is as follows : — 

* Bibliotheque Universelle, xxxvii. 15. 

t Philosophical Transactions, 1773, p. 461. t Ibid. 1776, p. 1. 

§ Ibid. 1776, p. 196. ' || Ibid. 1829, p. 16. 



100 Identity of electricities . [Semes III. 

352. Tension. — No sensible attractions or repulsions due to 
tension have been observed. 

353. In motion : i. Evolution of Heat ; not yet observed ; I 
have little or no doubt that Harris’s electrometer would show 
it (287. 359.). 

354. ii. Magnetism . — Perfectly distinct. According to Hr. 
Davy*, the current deflected the needle and made magnets 
under the same law, as to direction, which governs curreftts of 
ordinary and voltaic electricity. 

355. iii. Chemical decomposition. — Also distinct; and 
though Dr. Davy used an apparatus of similar construction 
with that of Dr. Wollaston (327.), still no eri'or in the present 
case is involved, for the decompositions were polar, and in 
their nature truly electro chemical. By the direction of the 
magnet, it was found that the under surface of the fish was 
negative, and the upper positive ; and in the chemical decom- 
positions, silver and lead were precipitated on the wire con- 
nected with the under surface and not on the other; and 
when these wires were either steel or silver, in solution of com- 
mon salt, gas (hydrogen ?) rose from the negative wire, but 
none from the positive. 

356. Another reason for the decomposition being electro- 
chemical is, that a Wollaston’s apparatus constructed with wires , 
coated with sealing wax, would most probably not have decom- 
posed water, even in its own peculiar way, unless the elec- 
tricity had risen high enough in intensity to produce sparks in 
some part of the circuit ; whereas the torpedo was not able to 
produce sensible sparks. A third reason is, that the purer the 
water in Wollaston’s apparatus, the more abundant is the de- 
composition : and I have found that a machine and wire points 
which succeeded perfectly well with distilled water, failed alto- 
gether when the water w as rendered a good conductor by sul- 
phate of Soda, common salt, or other saline bodies. But in Dr. 
Davy’s experiments with the torpedo, strong solutions of salt, 
nitrate of silver, and superacetate of lead were used success- 
fully, and there is no doubt w ith more success than weaker ones. 

357. iv. Physiological effects. — These are so characteristic, 
that by them the peculiar powers of the torpedo and gymnotus 
are principally recognised. 

* PLilosophical Tiansactions, 1832, p. 260. 



Jan. 1833.] Animal electricity. 101 

358. v. Spark . — The electric spark has not yet been ob- 
tained, or at least l 1 think not ; but perhaps I had better refer 
to the evidence on this point. Humboldt, speaking of results 
obtained by M. Fahlberg, # of Sweden, says, “This philosopher 
has spen an electric spark, as Walsh and Ingenhousz had done 
before him at London, by placing the gymnotus in the air, and 
interrupting the conducting chain by two gold leaves pasted 
upon # glass, and a line distant from each other*.” 1 cannot, 
however, find any record of such an observation by either 
Walsh or Ingenhousz, and do not know where to refer to that 
by M. Fahlberg. M. Humboldt could not himself perceive any 
luminous effect. 

Again, Sir John Leslie, in his dissertation on the progress of 
mathematical and physical science, prefixed to the seventh edi- 
tion of the Encyclopaedia Britannica, Edinb. 1830, p. 622, says, 

“ From a healthy specimen ” of the Silurus electricus , meaning 
rather the gymnotus , “ exhibited in London, vivid sparks were 
drawn in a darkened room ” ; but he does not say he saw them 
himself, nor state who did see them ; nor can I find any account 
of such a phenomenon ; so that the statement is doubtful f. 

359. In concluding this summary of the powers of torpedi- 

nal electricity, I cannot refrain from pointing out the enormous 
absolute quantity of electricity which the animal must put in 
circulation at each effort. It is doubtful whether any common 
electrical machine has as yet been able to supply electricity 
sufficient in a reasonable time to cause true electro-chemical 
decomposition of water (330. 339.), yet the current from the 
torpedo has done it. The same high proportion is shown by 
the magnetic effects (296/371.) These circumstances indicate 
that the torpedo has power (in the way probably that Caven- 
dish describes,) to continue the evolution for a sensible time, 
so that its successive discharges rather resemble those of a 
voltaic arrangement, intermitting in its action, than those of a 
Leyden apparatus, charged and discharged many times in suc- 
cession. In reality, however, there is no philosophical differ- 
ence between these two cases. ' 

360. The general conclusion which must, I think, be drawn 

* Edinburgh Phil. Journal, ii. p. 249. 

t Mr. Brayley, who referred me to these statements, and has extensive 
knowledge of recorded facts, is unacquainted with any further account relat- 
ing to them. 



102 Identity of electricities. [Series III. 

from this collection of facts is, that electricity , whatever may 
be its source , is identical in its nature . Th6 phenomena in the 
five kinds or species quoted, differ, not in their character but 
only in degree ; and in that respect vary in proportion to the 
variable circumstances of quantity and intensity* which can at 
pleasure be made to change in almost any one of the kinds of 
electricitv, as much as it does between one kind and another. 
Table of the experimental Effects common to the Electricities 
derived from different Sources +• 



Physiological 

Effects. 

Magnetic 

Deflection. 

Magnets 

made. 

• Spark. 

Heating 

Power. 

True chemical 
Action. 

Attraction and 
Repulsion. 

Discharge by 
Hot Air. 

1, Voltaic electricity . ... 

X 

X x | X 

X 

X 

X 

X 

2. Common electricity . . . 

X 

XXX 

X 

X 

x c 

X 

3. Magneto-Electricity. . 

X 

XXX 

X * 

X 

X 


4. Thermo-Electricity... 

X 

X 

JL 

+ 

4* 

4* 



6. Animal Electricity, . , 

X 

X 

X 

+ 

4- 

X 


i 


§ 8. Relation by Measure of common and voltaic Electricity .J 
361. Believing the point of identity to be satisfactorily esta- 
blished, I next endeavoured to obtain a common measure, or 

* The term quantity in electricity is perhaps sufficiently definite as to sense ; 
the term intensity is more difficult to define strictly. I am using the terms in 
their ordinary and accepted meaning. 

t Many of the spaces in this table originally left blank may now be filled. 
Thus with thermo-electricity , Botto made magnets and obtained polar chemi- 
cal decomposition : Antinori produced the spark j and if it has not been done 
before, Mr. Watkins has recently heated a wire in Harris’s thermo- electro- 
meter. In respect to animal electricity , Matteucci and Linari have obtained 
the spark from the torpedo, and I have recently procured it from the gym- 
notus: Dr, Davy has observed the heating power of the current from the 
torpedo. I have therefore filled up these spaces with crosses, in a different 
position to the others originally in the table. There remain but five spaces 
unmarked, two under attraction and repulsion , and three under discharge by 
hot air ; and though these effects have not yet been obtained, it is a necessary 
conclusion that they must be possible, since the spark corresponding to them 
h$s been procured. For when a discharge across cold air can occur, that in- 
tensity which is the only essential additional requisite for the other effects 
niust be present. — Dec. 13, 1838. 

% In further illustration of this subject see 866-873 in Series VII,— Dec. 1838. 



Jan. 1833.] Measure of electricities . 103 

a known relation as to quantity, of the electricity excited by a 
machine, and that* from a voltaic pile ; for the purpose not 
only of confirming their identity (378.), but also of demonstra- 
ting certain general principles (366. 377, &c.), and creating an 
extension of the means of investigating and applying the che- 
mical powers of this wonderful and subtile agent. 

362. The # first point to be determined was, whether the same 
absolute quantity of ordinary electricity, sent through a galva- 
nometer, under different circumstances, would cause the same 
deflection of the needle. An arbitrary scale was therefore at- 
tached to the galvanometer, each division of which was equal 
to about 4°, and the instrument arranged as in former experi- 
ments (296.). The machine (290.), battery (291.), and other 
parts of the apparatus were brought into good order, and 
retained for the time as nearly as possible in the same condi- 
tion. The experiments were alternated so as to indicate any 
change in the condition of the apparatus and supply the neces- 
sary corrections. 

363. Seven of the battery jars were removed, and eight re- 
tained for present use. It was found that about forty turns 
would fully charge the eight jars. They were then charged 
by thirty turns of the machine, and discharged through the 
galvanometer, a thick wet string, about ten inches long, being 
included in the circuit. The needle was immediately deflected 
five divisions and a half, on the one side of the zero, and in 
vibrating passed as nearly as possible through five divisions 
and a half on the other side. 

364. The other seven jars were then added to the eight, and 
the whole fifteen charged by thirty turns of the machine. The 
Henley's electrometer stood not quite half as high as before ; 
but when the discharge was made through the galvanometer, 
previously at rest, the needle immediately vibrated, passing 
exactly to the same division as in the former instance. These 
experiments with eight and with fifteen jars were repeated 
several times alternately with the same results. 

365. Other > experiments were than made, in which all the 
battery was used, and its charge (being fifty turns of the ma- 
chine,) sent through the galvanometer : but it was modified by 
being passed sometimes through a mere wet thread, sometimes 
through thirty -eight inches of thin string wet ted by distilled water 



104 Measure of electricities . [Series III. 

and sometimes through a string of twelve times the thickness, 
only twelve inches in length, and soaked ill dilute acid (298.) . 
With the thick string the charge passed at once ; with the thin 
string it occupied a sensible timd, and with the thread it re- 
quired two or three seconds before the electrometer ' fell en- 
tirely down. The current therefore must have varied extremely 
in intensity in these different cases, and yet the deflection of 
the needle was sensibly the same in all of them. If any differ- 
ence occurred, it was that the thin string and thread caused 
greatest deflection ; and if there is any lateral transmission, as 
M. Colladon says, through the silk in the galvanometer coil, it 
ought to have been so, because then the intensity is lower and 
the lateral transmission less. 

366. Hence it would appear that if the same absolute quan- 
tity of electricity pass through the galvanometer , whatever may 
be its intensity , the deflecting force upon the magnetic needle 
is the same. 

367. The battery of fifteen jars was then charged by sixty 
revolutions of the machine, and discharged, as before, through 
the galvanometer. The deflection of the needle was now as 
nearly as possible to the eleventh division, but the graduation 
was not accurate enough for me to assert that the arc was ex- 
actly double the former arc ; to the eye it appeared to be so. 
The probability is, that the ' deflecting force of an electric cur- 
rent is directly proportional to the absolute quantity of elec- 
tricity passed , at whatever intensity that electricity may be*. 

368. Dr. Ritchie has shown that in a case where the inten- 
sity of the electricity remained the same, the deflection of the 
magnetic needle was directly as the quantity of electricity passed 
through the galvanometer f* Mr. Harris has shown that the 
heating power of common electricity on metallic wires is the 
same for the same quantity of electricity whatever its intensity 
might have previously been J. 

* The great and general value of the galvanometer, as an actual measure 
of the electricity passing through it, either continuously or interruptedly, must 
be evident from a consideration of these two conclusions. As constructed by 
Professor Ritchie with glass threads (see Philosophical Transactions, 1830, p. 
218, and Quarterly Journal of Science, New Series, vol. i, p. 29), it apparently 
seems to leave nothing unsupplied in its own department. 

t Quarterly Journal of Science, New Series, vol. i. p. 33. 

% Plymouth Transactions, page 22. 



Jan. 1833.] Definite magnetic action of electricity . 


105 


369. The next point was to obtain a voltaic arrangement 
producing an effect fcqual to that j ust described (367) . A platina 
and a zinc wire were passed through the same hole of a draw- 
plate, being then one eighteenth of an inch in diameter ; these 
were fastened to a support, so that their lower ends projected, 
were parallel, and five sixteenths of an inch apart. The upper 
ends were well connected with the galvanometer wires. Some 
acid jvas diluted, and, after various preliminary experimeuts, 
that adopted as a standard which consisted of one drop strong 
sulphuric acid in four ounces distilled water. Finally, the time 
was noted which the needle required in swinging either from 
right to left or left to right : it was equal to seventeen beats of 
my watch, the latter giving one hundred and fifty in a minute. 
The object of these preparations was to arrange a voltaic appa- 
ratus, which, by immersion in a given acid for a given time, 
much less than that required by the needle to swing in one 
direction, should give equal deflection to the instrument with the 
discharge of ordinary electricity from the battery (363, 364.) ; 
and a new part of the zinc wire having been brought into position 
with the platina, the comparative experiments were made. 

370. On plunging the zinc and platina wires five eighths of 
an inch deep into the acid, and retaining them there for eight 
beats of the watch, (after which they were quickly withdrawn,) 
the needle was deflected, and continued to advance in the same 
direction some time after the voltaic apparatus had been re- 
moved from the acid. It attained the five-and-a-half division, 
and then returned, swinging an equal distance on the other side. 
This experiment was repeated many times, and always with the 
same result. 

371. Hence, as an approximation, and judging from magnetic 
force only at present (376.) , it would appear that two wires, 
one of platina and one of zinc, each one eighteenth of an inch 
in diameter, placed five sixteenths of an inch apart and im- 
mersed to the depth of five ^eighths of an inch in acid, consisting 
of one drop oil of vitriol and four ounces distilled water, at a 
temperature about 60°, and connected at the other extremities 
by a copper wire eighteen feet long and one eighteenth of an 
inch thick (being the wire of the galvanometer coils), yield as 
much electricity in eight beats of my watch, or in -j-f^ths of a 
minute, as the electrical battery charged by thirty turns of the 



106 1 Measure of electricities. [Seeies III. 

large machine, in excellent order (363. 364.). Notwithstanding 
this apparently enormous disproportion, the results are per- 
fectly in harmony with those effects which are known to be 
produced by variations in the intensity and quantity of the elec- 
tric fluid. 

372. In order to procure a reference to chemical action , the 
wires were now retained immersed in the acid to the depth of 
five eighths of an inch, and the needle, when stationary, ob- 
served ; it stood, as nearly as the unassisted eye could decide, 
at division. Hence a permanent deflection to that extent 
might be considered as indicating a constant voltaic current, 
which in eight beats of my watch (369.), could supply as much 
electricity as the electrical battery charged by thirty turns of 
the machine. 

373. The following arrangements and results are selected 
from many that were made and obtained relative to Chemical 
action. A platina wire one twelfth of an inch in diameter, 
weighing two hundred and sixty grains, had the extremity ren- 
dered plain so as to offer a definite surface equal to a circle of 
the same diameter as the wire ; it was then connected in turn 
with the conductor of the machine, or with the voltaic appa- 
ratus (369.), so as always to form the positive pole, and at the 
same time retain a perpendicular position, that it might rest, 
with its whole weight, upon the test paper to be employed. 
The test paper itself was supported upon a platina spatula, 
connected either with a discharging train (292.), or with the 
negative wire of the voltaic apparatus, and it consisted of four 
thicknesses, moistened at all times to an equal degree in a 
standard solution of hydriodate of potassa (316.). 

374. When the platina wire was connected with the prime 
conductor of the machine, and the spatula with the discharging 
train, ten turns of the machine had such decomposing power as 
to produce a pale round spot of iodine of the diameter of the 
wire ; twenty turns made a much darker mark, and thirty turns 
made a dark brown spot penetrating to the- second * thickness 
of the paper. The difference in effect produced by two or 
three turns, more or less, could be distinguished with facility. 

376. The wire and spatula were then connected with the 
voltaic apparatus (369.) the galvanometer being also included 
in the arrangement ; and, a stronger acid having been prepared, 



Jan. 1833.] Definite chemical force of electricity . 107 

consisting of nitric acid and water, the voltaic apparatus was 
immersed so far as £o give a permanent deflection of Jhe needle 
to the 5J division (372.) , the fourfold moistened paper inter- 
vening as before.* Then by shifting the end of the wire from place 
to place upon the test paper, the effect of the current for five, 
six, seven, or any number of the beats of the watch (369.) was 
observed, and compared with that of the machine. After alter- 
nating and repeating the experiments of comparison many times, 
it was constantly found that this standard current of voltaic 
electricity, continued for eight beats of the watch, was equal, 
in chemical effect, to thirty turns of the machine ; twenty-eight 
revolutions of the machine were sensibly too few. 

376. Hence it results that both in magnetic deflection (371.) 
and in chemical force, the current of electricity of the standard 
voltaic battery for eight beats of the watch was equal to that of 
the machine evolved by thirty revolutions. 

377. It also follows that for this case of electro-chemical de- 
composition, and it is probable for all cases, that the chemical 
power, like the magnetic force (366.) is in direct proportion to 
the absolute quantity of electricity which passes. 

378. Hence arises still further confirmation, if any were 
required, of the identity of common and voltaic electricity, and 
that the differences of intensity and quantity are quite suffi- 
cient to account for what were supposed to be their distinctive 
qualities. 

379. The extension which the present investigations have 
enabled me to make of the facts and views constituting the 
theory of electro- chemical decomposition, will, with some other 
points of electrical doctrine, be almost immediately submitted 
to the Royal Society in another series of these Researches, 

* Of course the heightened power of the voltaic battery was necessary to 
compensate for the bad conductor now interposed. 

Royal Institution, 

15*4 Dec, 1832. 


Note. — I am anxious, and am permitted, to add to this paper a correction 
of an error which I have attributed to M. Ampere in the first series of these 
Experimental Researches. In referring to his experiment on the induction of 
electrical currents (78.), I have called that a disc which X should have called a 



108 Amp&re’s inductive results . [Series III. 

circle or a ring. M. Ampere used a ring, or a very short cylinder made of a 
narrow plate of copper bent into a circle, and he tells mg that by such an arrange- 
ment the motion is very readily obtained. I have not doubted that M. Ampere 
obtained the motion he described ; but merely mistook the kind of mobile 
conductor used, and so far I described his experiment erroneously. 

In the same paragraph I have stated that M. Ampere says the disc turned 
" to take a position of equilibrium exactly as the spiral itself would have turned 
had it been free to move” ; and further on I have said that my results tended 
to invert the sense of the proposition u stated by M. Ampere, that a current of 
electricity tends to put the electricity of conductors near which it passes id' motion 
in the same direction M. Ampere tells me in a letter which I have just re- 
ceived from him, that he carefully avoided, when describing the experiment, 
any reference to the direction of the induced current} and on looking at the 
passages he quotes to me, I find that to be the case. I have therefore done him 
injustice in the above statements, and am anxious to correct my error. 

But that it may not be supposed I lightly wrote those passages, I will briefly 
refer to my reasons for understanding them in the sense I did. At first the ex- 
periment failed. When re-made successfully about a year afterwards, it was 
at Geneva in company with M. A, De la Rive : the latter philosopher described 
the results*, and says that the plate of copper bent into a circle which was used 
as the mobile conductor u sometimes advanced between the two branches of 
the (horse-shoe) magnet, and sometimes was repelled, according to the direc- 
tion of the current in the surrounding conductors.” 

I have been in the habit of referring to Demonferrand’s Manuel d' Electricite 
Bynamique , as a book of authority in France ; containing the general results 
and laws of this branch of science, up to the time of its publication, in a well- 
arranged form. At p. 173, the author when describing this experiment says, 
“ The mobile circle turns to take a position of equilibrium as a conductor 
would do in which the current mo\ed in the same direction as in the spiral ; ” 
and in the same paragraph he adds, “ it is therefore proved that a current of elec- 
tricity tends to put the electricity of conductors, near which it 2 >asses, in motion in 
the same direction .” These are the words I quoted in my paper (78,). 

Le Lycde of 1st of January, 1832, No. 3G, in an article written after the re- 
ceipt of my first unfortunate letter to M. Hachette, and before my papers were 
printed, reasons upon the direction of the induced currents, and says, that there 
ought to be “ an elementary current produced in the same direction as the cor- 
responding portion of the producing current. A little further on it says, 
“ therefore we ought to obtain currents, moving in the same direction , produced 
* upon a metallic wire, either by a magnate or a current. M. Ampere was so 
thoroughly persuaded that such ought to be the direction of the currents by influ- 
ence, that he neglected to assure himself of it in his experiment at Geneva.” 

It was the precise statements in Demonferrand’s Manuel, agreeing as they 
did with the expression iu M. De la Rive’s paper, (which, however, I now un- 
derstand as only meaning that when the inducing current was changed, the 
motiop of the mobile circle changed also) and not in discordance with anything 
expressed by M. Ampere himself where he speaks of the experiment, which 

* Biblioth&que Universelle, xxi. p. 48. 



109 


Jan. 1833.} Ampere’s inductive results . 

made me conclude, when I wrote the paper, that what I wrote was really his 
avowed opinion^ and when the Number of the Lyc«5e referred to appeared, 
which was before my pajSer was, printed, it could excite no suspicion that X was 
in error. 

Hence the mistake into which I unwittingly fell. I am proud to correct it 
and do full justice to the acuteness and accuracy which, as far as I can under- 
stand the subjects, M. Ampere carries into all the branches of philosophy which 
he investigates. 

Finally, my note to (79.) says that the Lycee, No. 36, “ mistakes the erro- 
neous results of MM. Fresnel and Ampere for true ones,” &c. &c. In calling 
M. Ampere’s results erroneous, I spoke of the results described in, and referred 
to by the Lycde itself ; but now that the expression of the direction of the in- 
duced current is to be separated, the term erroneous ought no longer to be 
attached to them. 

April 29, 1833. M. F. 



110 


FOURTH SERIES. 

§9 . On a new Law of Electric Conduction , § 10. On Con- 

ducting Power generally. 

Received April 24, — Read May 23, 1833. 

§ 9. On a new Law of Electric Conduction*. 

380. It was during the progress of investigations relating to 
electro-chemical decomposition, which I still have to submit to 
the Royal Society, that I encountered effects due to a very 
general law of electric conduction not hitherto rccogiysed* and 
though they prevented me from obtaining the condition I sought 
for, they afforded abundant compensation for the momentary 
disappointment, by the new and important interest which they 
gave to an extensive part of electrical sciencp. 

381. I was working with ice, and the solids resulting from 
the freezing of solutions, arranged either as barriers across a 
substance to be decomposed, or as the actual poles of a voltaic 
battery, that I might trace and catch certain elements in their 
transit, when I was suddenly stopped in my progress by finding 
that ice was in such circumstances a non-conductor of electri- 
city ; and that as soon as a thin film of it was interposed, in 
the circuit of a very powerful voltaic battery, the tranmission 
of electricity was prevented, and all decomposition ceased. 

' 382. At first the experiments were made with common ice, 
during the cold freezing weather of the latter end of January 
1833; but the results were fallacious, from the imperfection 
Of the arrangements, and the following more unexceptionable 
form of experiment was adopted. 

383. Tin vessels were formed, five inches deep, one inch and 
a quarter wide in one direction, of different widths from three 
eights to five eights of an inch in the other, and open at 
one extremity. Into these were fixed by corks, plates of platina, 
* In reference to this law see further considerations at 910. 1358. 1705.— 
Ztec. 1838, 



Ill 


April 1833.] Non-conduction of electricity by ice. 

so that the latter should not touch the tin cases ; and copper 
wires having previously been soldered to the plates, these were 
easily connected, when required, with a voltaic pile. Then dis- 
tilled water, previously boiled for three hours, was poured into 
the vessels, and frozen by a mixture of salt and snow, so that 
pure transparent solid ice intervened between the platina and 
tin : and finally these metals were connected with the opposite 
extremities of the voltaic apparatus, a galvanometer being at 
the satne time included in the circuit. 

384. In the first experiment, the platina pole was three inches 
and a half long, and seven eights of an inch wide ; it was wholly 
immersed in the water or ice, and as the vessel was four eighths 
of an inch in width, the average thickness of the intervening 
ice was only a quarter of an inch, whilst the surface of contact 
with it at both poles was nearly fourteen square inches. After 
the water, was frozen, the vessel was still retained in the frigo- 
rific mixture, whilst contact between the tin and platina re- 
spectively was made with the extremities of a well-charged 
voltaic battery, consisting of twenty pairs of four-inch plates, 
each with double coppers. Not the slightest deflection of the 
galvanometer needle occurred. 

385. On taking the frozen arrangement out of the cold mix- 
ture, and applying warmth to the bottom of the tin case, so as 
to melt part of the ice, the connexion with the battery being in 
the mean time retained, the needle did not at first move; and 
it was only when the thawing process had extended so far as to 
liquefy part of the ice touching the platina pole, that conduction 
took place ; but then it occurred effectually, and the galvano- 
meter needle was permanently deflected nearly 70°. 

386. In another experiment, a platina spatula, five inches in 
length and seven eighths of an inch in width, had four inches 
fixed in the ice, and the latter was only three sixteenths of an 
inch thick between one metallic surface and the other ; yet thiB 
arrangement insulated as perfectly as the former. 

387. Upon pourihg a little water in at the top of this vessel 
on the ice, still the arrangement did not conduct; yet fluid 
water was evidently there. This result was the consequence 
of the cold metals having frozen the water where they touched 
it, and thus insulating the fluid part ; and it well illustrates 
the non-conducting power of ice, by showing how thin a film 



112 New Iqw of electric conduction . [Series IV. 

could prevent the transmission of the battery current. Upon 
thawing parts of this thin film, at both metals, conduction oc- 
curred. 

338. Upon warming the tin case and removing the piece of 
ice, it was found that a cork having slipped, one of the edges 
of the platina had been all but in contact with the inner surface 
of the tin vessel ; yet, notwithstanding the extreme thinness of 
the interfering ice in this place, no sensible portion of electri- 
city had passed. 

389. These experiments were repeated many time# with the 
same results. At last a battery of fifteen troughs, or one 
hundred and fifty pairs of four-inch plates, powerfully charged, 
was used; yet even here no sensible quantity of electricity 
passed the thin barrier of ice. 

390. It seemed at first as if occasional departures from these 
effects occurred; but they could always be traced to some in- 
terfering circumstances. The water should in every instance 
be well frozen ; for though it is not necessary that the ice should 
reach from pole to pole, since a barrier of it about one pole 
would be quite sufficient to prevent conduction, yet, if part re- 
main fluid, the mere necessary exposure of the apparatus to the 
air, or the approximation of the hands, is sufficient to produce, 
at the upper surface of the water and ice, a film of fluid, ex- 
tending from the platina to the tin ; and then conduction oc- 
curs. Again, if the corks used to block the platina in its place 
are damp or wet within, it is necessary that the cold be suffi- 
ciently well applied to freeze the water in them, or else when 
the surfaces of their contact with the tin become slightly warm 
by handling, that part will conduct, and the interior being feady 
to conduct also, the current will pass. The water should be 
pure, not only that unembarrassed results may be obtained, but 
also that, as the freezing proceeds, a minute portion of concen- 
trated saline solution may not be formed, which remaining fluid, 
and being interposed in the ice, or passing into cracks resulting 
from contraction, may exhibit conducting powers independent 
of the ice itself. 

391. On one occasion I was surprised to find that after thaw- 
ing much of the ice the conducting power had not been restored ; 
but I found th&t a cork which held the wire just where it joined 
the platina, dipped so far into the ice, that with the ice itself.* 



113 


April 1833.] Fused chloride of lead conducts . 

it protected the platina from contact with the melted part long 
after that contact was expected. 

392. This insulating power of ice is not effective with elec- 
tricity of exalted intensity. On touching a diverged gold-leaf 
electrometer with a wire connected with the platina, whilst 
the tin case was touched by the hand or another wire, the elec- 
trometer was instantly discharged (419.) . 

393. * But though electricity of an intensity so low that it 
cannoff diverge the electrometer, can still pass (though in very 
limited quantities (419.),) through ice ; the comparative relation 
of water and ice to the electricity of the voltaic apparatus is 
not less extraordinary on that account, or less important in its 
consequences. 

394. As it did not seem likely that this laiv of the assumption 
of conducting power during liquefaction , and loss of it during 
congestion , would be peculiar to water, I immediately pro- 
ceeded to ascertain its influence in other cases, and found it to 
be very general. For this purpose bodies were chosen which 
were solid at common temperatures, but readily fusible ; and of 
such composition as, for other reasons connected with electro- 
chemical action, led to the conclusion that they would be able 
when fused to replace water as conductors. A voltaic battery 
of two troughs, or twenty pairs of four-inch plates (384.), was 
used as the source of electricity, a*ul a galvanometer introduced 
into the circuit to indicate the presence or absence of a 
current. 

395. On fusing a little chloride of lead by a spirit-lamp on a 
fragment of a Florence flask, and introducing two platina wires 
connected with the poles of the battery, there was instantly 
powerful action, the galvanometer was most violently affected, 
and the chloride rapidly decomposed. On removing the lamp, 
the instant the chloride solidified all current and consequent 
effects ceased, though the platina wires remained inclosed in 
the chloride not more than the one-sixteenth of an inch from 
each other. On renewing the heat, as soon as the fusion had 
proceeded far enough to allow liquid matter to connect the 
poles, the electrical current instantly passed. 

396. On fusing the chloride, with one wire introduced, and 
then touching the liquid with the other, the latter being cold, 
caused a little knob to concrete on its extremity, and no current 



114s New law of electric conduction . [Series V* 

passed ; it was only when the wire became so hot as to be able 
to admit or allow of contact with the liquid matter, that con- 
duction took place, and then it was very powerful. 

397. When chloride of silver and chlorate of potassa were 
experimented with, in a similar manner, exactly the same re- 
sults occurred. 

398. Whenever the current passed in these cases, there was 
decomposition of the substances ; but the electro-chemical part 
of this subject I purpose connecting with more general views 
in a future paper*. 

399. Other substances, which could not be melted on glass/ 
were fused by the lamp and blowpipe on platina connected 
with one pole of the battery, and then a wire, connected with 
the other, dipped into them. In this- way chloride of sodium, 
sulphate of soda, protoxide of lead, mixed carbonates of potash 
and soda, &c. &c., exhibited exactly the same phenomena as 
those already described : whilst liquid, they conducted and were 
decomposed ; whilst solid, though very hot, they insulated the 
battery current even when four troughs were used. 

400. Occasionally the sub- 
stances were contained in small 
bent tubes of green glass, and 
when fused, the platina poles in- 
troduced, one on each side. In 
such cases the same general re- 
sults as those already described were procured ; but a further 
advantage was obtained, namely, that whilst the substance 
was conducting and suffering decomposition, the final arrange- 
ment of the elements could be observed. Thus, iodides of po- 
tassium and lead gave iodine at the positive pole, and potas- 
sium or lead at the negative pole. Chlorides of lead and silver 
gave chlorine at the positive, and metals at the negative pole. 

* In 1801, Sir H. Davy knew that t( dry nitre, caustic potash, and soda are 
conductors of galvanism when rendered fluid by a high degree of heat,” (Jour- 
nals of the Royal Institution, 1802, p. 53,) but was not aware of the general 
law which I have been engaged in developing. It is remarkable, that eleven 
years after that, he should say, “ There are no fluids known except such as 
contain water, which are capable of being made the medium of connexion 
between the metal or metals of the voltaic apparatus,” Elements of Chemi- 
cal Philosophy, p. 169. 




115 


April 1833.] Bodies subject to the law , 

Nitre and chlorate of potassa gave oxygen, &c., at the positive, 
and alkali, or even potassium, at the negative pole. 

401. A fourth arrangement was used for substances requiring 
very high temperatures for their fusion. A platina wire was 
connected with one pole of the battery ; its extremity bent into 
a small ring, in the manner described by Berzelius, for blow- 
pipe experiments ; a little of the salt, glass, or other substance, 
was melted on this ring by the ordinary blowpipe, or even in 
some fcases by the oxy-hydrogen blowpipe, and when the drop, 
retained in its place by the ring, was thoroughly hot and fluid, 
a platina wire from the opposite pole of the battery was made 
to touch it, and the effects observed. 

402. The following are various substances, taken from very 
different classes chemically considered, which are subject to 
this law. The list might, no doubt, be enormously extended ; 
but I have not had time to do more than confirm the law by a 
sufficient number of instances. 

First, water . 

Amongst oocides ; — potassa, protoxide of lead, glass of anti- 
mony, protoxide of antimony, oxide of bismuth. 

Chlorides of potassium, sodium, barium, strontium, calcium, 
magnesium, manganese, zinc, copper (proto-) , lead, tin (proto-) , 
antimony, silver. 

Iodides of potassium, zinc and lead, protiodide of tin, perio- 
dide of mercury ; fluoride of potassium ; cyanide of potassium ; 
sulpho -cyanide of potassium. 

Salts, Chlorate of potassa ; nitrates of potassa, soda, baryta, 
strontia, lead, copper, and silver; sulphates of soda and lead, 
proto-sulphate of mercury > phosphates of potassa, soda, lead, 
copper, phosphoric glass or acid phosphate of lime ; carbonates 
of potassa and soda, mingled and separate ; borax, borate' of 
lead, per-borate of tin ; chromate of potassa, bi-chromate of 
potassa, chromate of lead ; acetate of potassa. 

Sulpkurets. Sulphuret of antimony, sulphuret of potassium 
made by reducing sulphate of potassa by hydrogen ; ordinary 
sulphuret of potassa. 

. Silicated potassa ; chameleon mineral. 

403. It is highly interesting in the instances of those sub- 
stances which soften before they liquefy, to observe at what 
period the conducting power is acquired, and to what degree 

i 2 



116 


New law of electric conduction . [Series IV. 

it is exalted by perfect fluidity. Thus, with the borate of lead, 
when heated by the lamp upon glass, it ^becomes as soft as 
treacle, but it did not conduct, and it was only when urged by 
the blowpipe and brought to a fair red heat, that it conducted. 
When rendered quite liquid, it conducted with extreme fa- 
cility. 

404. I do not mean to deny that part of the increased con- 
ducting power in these cases of softening was probably due to 
the elevation of temperature (432. 445 .) ; but I have no 'doubt 
that by far the greater part was due to the influence of the ge- 
neral law already demonstrated, and which in these instances 
came gradually, instead of suddenly, into operation. 

405. The following are bodies which acquired no conducting 
power upon assuming the liquid state 

Sulphur, phosphorus ; iodide of sulphur, per-iodidc of tin ; 
orpiment, realgar ; glacial acetic acid, mixed inargaric -and oleic 
acids, artificial camphor ; caffeine, sugar, adipocire, stearine of 
cocoa-nut oil, spermaceti, camphor, naphthaline, resin, gum 
sandarach, shell lac. 

406. Perchloride of tin, chloride of arsenic, and the hydrated 
chloride of arsenic, being liquids, had no sensible conducting 
power indicated by the galvanometer, nor were they decom- 
posed. 

407. Some of the above substances are sufficiently remark- 
able as exceptions to the general law governing the former 
cases. These are orpiment, realgar, acetic acid, artificial cam- 
phor, per-iodide of tin, and the chlorides of tin and arsenic. I 
shall have occasion to refer to these cases in the paper on 
Electro -chemical Decomposition. 

408. Boracic acid was raised to the highest possible tempe- 
rature by an oxy-hydrogen flame (401.), yet it gained no con- 
ducting powers sufficient to affect the galvanometer, and under- 
went no apparent voltaic decomposition. It seemed to be quite 
as bad a conductor as air. Green bottle-glass, heated in the 
same manner, did not gain conducting power sensible to the gal- 
vanometer. Flint glass, when highly heated, did conduct a little 
and decompose ; and as the proportion of potash or oxide of. 
lead was increased in the glass, the effects were more powerful. 
Those glasses, consisting of boracic aoid on the one hand, and 
oxide of lead or potassa on the other, show the assumption of 



117 


April 1833.] Degree of conducting power conferred. 

conducting power upon fusion and the accompanying decompo- 
sition very well. 

409. I was very anxious to try the general experiment with 
sulphuric acid, of about specific gravity 1* 783, containing that 
proportion of water which gives it the power of crystallizing at 
40° Fahr. ; but I found it impossible to obtain it so that I could 
be sure the whole would congeal even at 0° Fahr. A ten-thou- 
sandtj part of water, more or less than necessary, would, upon 
cooling the whole. Cause a portion of uncongealable liquid to 
separate, and that remaining in the interstices of the solid mass, 
and moistening the planes of division, would prevent the correct 
observation of the phenomena due to entire solidification and 
subsequent liquefaction. 

410. With regard to fhe substances on which conducting power 
is thus conferred by liquidity, the degree of power so given is 
generally very great. Water is that body in which this ac- 
quired power is feeblest. In the various oxides, chlorides, 
salts, &c., &c., it is given in a much higher degree. I have not 
had time to measure the conducting power in these cases, but 
it is apparently some hundred times that of pure water. The 
increased conducting power known to be given to water by the 
addition of salts, would seem to be in a great degree depend- 
ent upon the high conducting power of these bodies when in 
the liquid state, that state being given them for the time, not 
by heat but solution in the water*. 

411. Whether the conducting power of these liquefied bo- 
dies is a consequence of their decomposition or not (413.), or 
whether the two actions of conduction and decomposition are 
essentially connected or not, would introduce no difference af- 
fecting the probable accuracy of the preceding statement. 

412. This general assumption of conducting power by bodies 
as soon as they pass from the solid to the liquid state, offers a 
new and extraordinary character, the existence of which, as far 
as 1 know, has not before been suspected ; and it seems im- 
portantly connected with some properties and relations of the 
particles of matter which I may now briefly point out. 

413. In almost all the instances, as yet observed, which are 
governed by this law, the substances experimented with have 
been those which were not only compound bodies, but such as 

* See a doubt on this point at 1356. — Dec. 1838, 



na 


New law of electric conduction. - [Semes IV. 

contain elements known to arrange themselves at the opposite 
poles ; and were also such as could be decomposed by the elec- 
trical current. When conduction took place, decomposition 
occurred ; when decomposition ceased, conduction ceased also ; 
and it becomes a fair and an important question, Whether the 
conduction itself may not, wherever the law holds good, be a 
consequence not merely of the capability, but of the act of de- 
composition ? And that question may be accompanied J»y an- 
other, namely. Whether solidification does not prevent conduc- 
tion, merely by chaining the particles to their places, under the 
influence of aggregation, and preventing their final separation 
in the manner necessary for decomposition ? 

414. But, on the other hand, there is one substance (and 
others may occur) , the per -iodide of mercury , which, being ex- 
perimented with like the others (400.), was found to insulate 
when solid, and to acquire conducting power when fluid ; yet it 
did not seem to undergo decomposition in the latter case. 

415. Again, there are many substances which contain ele- 
ments such as would be expected to arrange themselves at the 
opposite poles of the pile, and therefore in that respect fitted 
for decomposition, which yet do not conduct. Amongst these 
are the iodide of sulphur, per-iodide of zinc, per-chloride of 
tin, chloride of arsenic, hydrated chloride of arsenic, acetic 
acid, orpiment, realgar, artificial camphor, &c. ; and from these 
it might perhaps be assumed that decomposition is dependent 
upon conducting power, and not the latter upon the former. 
The true relation, however, of conduction and decomposition in 
those bodies governed by the general law which it is the object 
o£ this paper to establish, can only be satisfactorily made out 
from -a far more extensive series of observations than those I 
have yet been able to supply*. 

416. The relation, under this law, of the conducting power 
for electricity to that for heat, is very remarkable, and seems 
tp imply a natural dependence of the two. As the solid becomes 
a fluid, it loses almost entirely the power of conduction 
for heat, but gains in a high degree that for electricity ; but as 
it reverts back to the solid state, it gains the power of Conduct- 
ing heat, and loses that of conducting electricity. If, therefore, 
the properties are not incompatible, still they are most strongly 

* See 679, &c. &c.— Dec. 1838. 



119 


April 1833.] Conduction by ice and solid salts. 

contrasted, one being lost as the other is gained. We may 
hope, perhaps, hereafter to understand the physical reason of 
this very extraordinary relation of the two conducting powers, 
both of which appear to be directly connected with the corpus- 
cular condition of the substances concerned. 

417. The assumption of conducting power and a decompo- 
sable condition by liquefaction, promises new opportunities of, 
and great facilities in, voltaic decomposition. Thus, such bodies 
as the oxides, chlorides, cyanides, sulpho* cyanides, fluorides, 
certain vitreous mixtures, &c. & e., may be submitted to 
the action of the voltaic battery under new circumstances ; and 
indeed I have already been able, with ten pairs of plates, to de- 
compose common salt, chloride of magnesium, borax, &c. &c., 
and to obtain sodium, magnesium, boron, &c., in their separate 
states. 

§ 10. On Conducting Power generally*. 

418. It is not my intention here to enter into an examination 
of all the circumstances connected with conducting power, but 
to record certain facts and observations which have arisen 
during recent inquiries, as additions to the general stock of 
knowledge relating to this point of electrical science. 

419. I was anxious, in the first place, to obtain some idea of 
the conducting power of ice and solid salts for electricity of 
high tension (392.), that a comparison might be made between 
it and the large accession of the same power gained upon lique- 
faction. For this purpose the large electrical machine (290.) 
was brought into excellent action, its conductor connected with 
a delicate gold-leaf electrometer, and also with the platina in- 
closed in the ice (383.), whilst the tin case was connected with 
the discharging train (292.) . On working the machine mode- 
rately, the gold leaves barely separated ; on working it rapidly, 
they could be opened nearly two inches. In this instance the 
tin ease was five eighths of an inch in width ; and as, after the 
experiment, the platina plate was found very nearly in the 
middle of the ice, the average thickness of the latter had been 
five sixteenths of an inch, and the extent of surface of contact 
with tin and platina fourteen square inches (384.). Yet, under 

* In reference to this § refer to 983 in series viii., and the results connected 
with it. — Pee. 1838. 



120 Conduction by solid iodide of potassium, [Series IV 

these circumstances, it was but just able to conduct the small 
quantity of electricity which this machine could evolve (371.), 
even when of a tension competent to open the leaves two inches ; 
no wonder, therefore, that it could not conduct any sensible 
portion of the electricity of the troughs (384.), which, though 
almost infinitely surpassing that of the machine in quantity, 
had a tension so low as not to be sensible to an electro- 
meter. 

420. In another experiment, the tin case was only four eighths 
of an inch in width, and it was found afterwards that the pla- 
tina had been not quite one eighth of an inch distant in the ice 
from one side of the tin vessel. When this was introduced 
into the course of the electricity from the machine (419.), the 
gold leaves could be opened, but not iftorc than half an mch ; 
the thinness of the ice favouring the conduction of the electri- 
city, and permitting the same quantity to pass in the same time, 
though of a much lower tension. 

421. Iodide of potassium which had been fused and cooled 
was introduced into the course of the electricity from the 
machine. There were two pieces, each about a quarter of an inch 
in thickness, and exposing a surface on each side equal to 
about half a square inch ; these were placed upon platina plates, 
one connected with the machine and electrometer (419.), and 
the other with the discharging train, whilst a fine platina wire 
connected the two pieces, resting upon them by its two points. 
On working the electrical machine, it was possible to open the 
electrometer leaves about two thirds of an inch. 

422. As the platina wire touched only by points, the facts 
show that this salt is a far better conductor than ice ; but as 
the leaves of the electrometer opened, it is also evident with 
what difficulty conduction, even of the small portion of elec- 
tricity produced by the machine, is effected by this body in the 
solid state, when compared to the facility with which enormous 
quantities at very low tensions are transmitted by it when in the 
fluid state. 

423. In order to confirm these results by others, obtained 
from the voltaic apparatus, a battery of one hundred and fifty 
plates, four inches square, was well charged : its action was 
good ; the shock from it strong ; the discharge would continue 
from copper to copper through four teuths of an inch of air. 



April 1833.] Conduction by ice . 121 

and the gold-leaf electrometer before used could be opened 
nearly a quarter of^in inch. 

424. The ice vessel employed (420.) was half an inch in 
width : as the extent of contact of the ice with the tin and pla- 
tina was nearly fourteen square inches, the whole was equivalent 
to a plate of ice having a surface of seven square inches of per- 
fect contact at. each side, and only one fourth of an inch thick. 
It wad retained in a freezing mixture during the experiment. 

425. The order of arrangement in the course of the electric 
current was as follows. The positive pole of the battery was 
connected by a wire with the platina plate in the ice ; the plate 
was in contact with the ice, the ice with the tin jacket, the 
jacket with a wire, which communicated with a piece of tin foil, 
on which rested one eifd of a bent platina wire (312.), the other 
or decomposing end being supported on paper moistened with 
solution of iodide of potassium (316.) : the paper was laid flat 
on a platina spatula connected with the negative end of the bat- 
tery. All that part of the arrangement between the ice-vessel 
and the decomposing wire point, including both these, was in- 
sulated, so that no electricity might pass through the latter 
which had not traversed the former also. 

426. Under these circumstanoes, it was found that a pale 
brown spot of iodine was slowly formed under the decomposing 
platina point, thus indicating that ice could conduct a little of 
the electricity evolved by a voltaic battery charged up to the de- 
gree of intensity indicated by the electrometer. But it is quite 
evident that notwithstanding the enormous quantity of elec- 
tricity which the battery could furnish, it was, under present 
circumstances, a very inferior instrument to the ordinary ma- 
chine ; for the latter could send as much through the ice as it 
could carry, being of a far higher intensity, i. e. able to open 
the electrometer leaves half an inch or more (419. 420.) . 

427. The decomposing wire and solution of iodide of potas- 
sium were then removed, and replaced by a very delicate galva- 
nometer (205.) ; it was so nearly astatic, that it vibrated to and 
fro in about sixty-three beats of a watch giving one hundred 
and fifty beats in a minute. The same feebleness of current as 
before was still indicated ; the galvanometer needle was de- 
flected, but it required to break and make contact three or four 
times (297.), before the effect was decided. 



122 Conduction by solid compounds, [Series IY. 

428. The galvanometer being removed, two platina plates 
were connected with the extremities of tfie wires, and the 
tongue placed between them, so that the whole charge of the 
battery, so far as the ice would let it pass, was free to go through 
the tongue. Whilst standing on the stone floor, there was 
shock, &e., but when insulated, I could feel no sensation. I 
think a frog would have been scarcely, if at all, affected. 

429. The ice was now removed, and experiments madd with 
other solid bodies, for which purpose they were placed under the 
end of the decomposing wire instead of the solution of iodide of 
potassium (425.) . For instance, a piece of dry iodide of potassium 
was placed on the spatula connected with the negative pole of 
the battery, and the point of the decomposing, wire placed upon 
it, whilst the positive end of the battery Communicated with the 
latter. A brown spot of iodine very slowly appeared, indicating 
the passage of a little electricity, and agreeing in that' respect 
with the results obtained by the use of the electrical machine 
(421.). When the galvanometer was introduced into the cir- 
cuit at the same time with the iodide, it was with difficulty that 
the action of the current on it could be rendered sensible. 

430. A piece of common salt previously fused and solidified 
being introduced into the circuit was sufficient almost entirely 
to destroy the action on the galvanometer. Fused and cooled 
chloride of lead produced the same effect. The conducting 
power of these bodies when fluid, is very great (395. 402.). 

431. These effects, produced by using the common machine 
and the voltaic battery, agree therefore with each other, and 
with the law laid down in this paper (394.) ; and also with the 
opinion I have supported, in the Third Series of these Re- 
searches, of the identity of electricity derived from different 
sources (360.). 

432. The effect of heat in increasing the conducting power 
of many substances, especially for electricity of high tension, is 
well known. I have lately met with an extraordinary case of 
this kind, for electricity of low tension, or that of the voltaic 
pile, and which is in direct contrast with the influence of heat 
upon metallic bodies, as observed and described by Sir Hum- 
phry Davy *. 

433. The substance presenting this effect is sulphuret of sil- 

* Philosophical Transactions, 1821, p, 431. 



123 


April 1833.] Increase of conducting power by heat, 

ver. It was made by fusing a mixture of precipitated silver 
and sublimed sulphur, removing the film of silver by a file from 
the exterior of the fused mass, pulverizing the sulphuret, min- 
gling it with more sulphur, and fusing it again in a green glass 
tube, so that no air should obtain access during the process. 
The surface of the sulphuret being again removed by a file or 
knife, it was. considered quite free from uncombined silver. 

434* When a piece of this sulphuret, half an inch in thick- 
ness, was put between surfaces of platina, terminating the poles 
of a voltaic battery of twenty pairs of four-inch plates, a galva- 
nometer being also included in the circuit, the needle was 
slightly deflected, indicating a feeble conducting power. On 
pressing the platina poles and sulphuret together with the fin- 
gers, the conducting power increased as the whole became 
warm. On applying a lamp under the sulphuret between the 
poles, thS conducting power rose rapidly with the heat, and at 
last the galvanometer needle jumped into a fixed position, and 
the sulphuret was found conducting in the manner of a metal. 
On removing the lamp and allowing the heat to fall, the effects 
were reversed, the needle at first began to vibrate a little, then 
gradually left its transverse direction, and at last returned to a 
position very nearly that which it would take when no current 
was passing through the galvanometer. 

435. Occasionally, when the contact of the sulphuret with the 
platina poles was good, the battery freshly charged, and the 
commencing temperature not too low, the mere current of elec- 
tricity from the battery was sufficient to raise the temperature 
of the sulphuret j and then, without any application of extra- 
neous heat, it went on increasing conjointly in temperature and 
conducting power, until the cooling influence of the air limited 
the effects. In such cases it was generally necessary to cool 
the whole purposely, to show the returning series of pheno- 
mena. 

436. Occasionally, also, the effects would sink of themselves, 
and could not be renewed until a fresh surface of the sulphuret 
had been applied to the positive pole. This was in consequence 
of peculiar results of decomposition, to which I shall have oc- 
casion to revert in the section on Electro -chemical Decompo- 
sition, and was conveniently avoided by inserting the ends of 
two pieces of platina wire into the opposite extremities of a 



124 Conducting power of metallic sulphurets . [Series IV. 

portion of sulphuret fused in a glass tube, and placing this 
arrangement between the poles of the battery. 

437. The hot sulphuret of silver conducts sufficiently well to 
give a bright spark with charcoal, &e. &c., in the manner of a 
metal. 

438. The native grey sulphuret of silver, and the ruby silver 
ore, both presented the same phenomena. The native mallea- 
ble sulphuret of silver presented precisely the same appearances 
as the artificial sulphuret. 

439. There is no other body with which I am acquainted, 
that, like sulphuret of silver, can compare with metals in con- 
ducting power for electricity of low tension when hot, but which, 
unlike them, during cooling, loses in power, whilst they, on the 
contrary, gain. Probably, however, inany others may, when 
sought for, be found*. 

440. The proto- sulphuret of iron, the native pcr-sulp! uret 
of iron, arsenical sulphuret of iron, native yellow sulphuret of 
copper and iron, grey artificial sulphuret of copper, artificial 
sulphuret of bismuth, and artificial grey sulphuret of tin, all 
conduct the voltaic battery current when cold, more or less, 
some giving sparks like the metals, others not being sufficient 
for that high effect. They did not seem to conduct better 
when heated, than before; but I had not time to enter accu- 
rately into the investigation of this point. Almost all of them 
became much heated by the transmission of the current, and 
present some very interesting phenomena in that respect. The 
sulphuret of antimony does not conduct the same current sensi- 
bly either hot or cold, but is amongst those bodies acquiring 
conducting power when fused (402.). The sulphuret of silver 
and perhaps some others decompose whilst in the solid state ; 
but the phenomena of this decomposition will be reserved for 
its proper place in the next series of these Researches. 

441. Notwithstanding the extreme dissimilarity between sul- 
phuret of silver and gases or vapours, I cannot help suspecting 
the action of heat upon them to be the same, bringing them all 
into the same class as conductors of electricity, although with 
those great differences in degree, which afe found to exist 
tinder common circumstances. When gases are heated, they 
increase in conducting power, both for common and voltaic elec- 

* See now on this subject, 1840, 1841. — Dee. 1888. 



Apbil 1833.] General conditions of conduction. 125 

tricity (271.) ; and it is probable that if we could compress and 
condense them at the same time, we should still further increase 
their conducting power. Cagniard de la Tour has shown that 
a substance, for instance, water, may be so expanded by heat 
whilst in the liquid state, or condensed whilst in the vaporous 
state, that the two states shall coincide at one point, and the 
transition from one to the other be so gradual that no line of 
demar<¥ition can be pointed out*; that, in fact, the two states 
shall become one ; — which one state presents us at different 
times with differences in degree as to certain properties and re- 
lations ; and which differences are, under ordinary circum- 
stances, so great as to be equivalent to two different states. 

442. I cannot but suppose at present that at that point where 
the liquid and the gaseous state coincide, the conducting pro- 
perties are the same for both ; but that they diminish as the ex- 
pansion gf the matter into a rarer form takes place by the re- 
moval of the necessary pressure ; still, however, retaining, as 
might be expected, the capability of having what feeble con- 
ducting power remains, increased by the action of heat. 

443. I venture to give the following summary of the conditions 
of electric conduction in bodies, not however, without fearing 
that I may have omitted some important points! • 

444. All bodies conduct electricity in the same manner from 
metals to lac and gases, but in very different degrees. 

445. Conducting power is in some bodies powerfully in- 
creased by heat, and in others diminished, yet without our per- 
ceiving any accompanying essential electrical difference, either 
in the bodies or in the changes occasioned by the electricity 
conducted. 

446. A numerous class of bodies, insulating electricity of low 
intensity, when solid, conduct it very freely when fluid, and are 
then decomposed by it. 

447. But there are many fluid bodies which do not sensibly 
conduct electricity of this low intensity; there are some which 
conduct it and are not decomposed ; nor is fluidity essential to 
decomposition! . 

*- Annales de Chimie, xxi. pp. 127, 178. 
t See now in relation to this subject, 1320 — 1342. — Dec. 1838. 
t See the next series of these Experimental Researches. 



126 Conducting power generally . {Series IV. 

448. There is hut one body yet discovered* which, insulating 
a voltaic current when solid, and conducting it when fluid, is 
not decomposed in the latter case (414.) . 

449. There is no strict electrical distinction of conduction 
which can, as yet, be drawn between bodies supposed to be ele- 
mentary, and those known to be compounds. 

* It is just possible that this case may, by more delicate experiment, here- 
after disappear. (See now, 1340, 1341, in relation to this note. — D&. 1838.) 

Royal Institution , 

April 15, 1833. 



127 


FIFTH SERIES. 

§ 11. On Electro-chemical Decomposition, i. New conditions 

of Electro-chemical Decomposition. ^ ii. Influence of Water 
in J^lectro-ch'emical Decomposition, iii. Theory of Electro- 
chemical Decomposition. 

Received June 18, — Read June 20, 1833. 

§ 11. On Electro-chemical Decomposition*. 

450. I have in a recent scries of these Researches (265.) 
proved (to my own satisfaction, at least,) the identity of electri- 
cities derived from different sources, and have especially dwelt 
upomthg proofs of the sameness of those obtained by the use of 
the common electrical machine and the voltaic battery. 

451. The great distinction of the electricities obtained from 
these two sources is the very high tension to which the small 
quantity obtained by aid of the machine may be raised, and 
the enormous quantity (371. 376.) in which that of compara- 
tively low tension, supplied by the voltaic battery, may be pro- 
cured ; but as their actions, whether magnctical, chemical, or 
of any other nature, are essentially the same (360.), it appeared 
evident that we might reason from the former as to the maimer 
of action of the latter ; and it was, to me, a probable conse- 
quence, that the use of electricity of such intensity as that 
afforded by the machine, would, when applied to effect and eluci- 
date electro-chemical decomposition, show some new conditions 
o£ that action, evolve new views of the internal arrangements 
and changes of the substances under decomposition, and per- 
haps give efficient powers over matter as yet undecomposed. 

452. For the purpose of rendering the bearings of the dif- 
ferent parts of this series of researches more distinct, I shall 
divide it into several heads. 

% i. New conditions of Electro-chemical Decomposition. 

453. The tension of machine electricity causes it, however 

* Refer to the note after 1047, Series viii.— Dec, 1838. 



128 Bodies evolved at great distances . [Series V. 

small in quantity, to pass through any length of water, solutions, 
or other substances classing with these as conductors, as fast 
as it can be produced, and therefore, in relation to quantity, 
as fast as it could have passed through much shorter portions 
of the same conducting substance. With the voltaic battery 
the case is very different, and the passing current of electricity 
supplied by it suffers serious diminution in any substance, by 
considerable extension of its length, but especially in, such 
bodies as those mentioned above. 4 

454. I endeavoured to apply this facility of transmitting the 
current of electricity through any length of a conductor, - to an 
investigation of the transfer of the elements in a decomposing 
body, in contrary directions, towards the poles. The general 
form of apparatus used in these experiments has been already 
described (312. 316.) ; and also a particular experiment (319.), 
in which, when a piece of litmus paper and a piece of Jur/neric 
paper were combined and moistened in solution of sulphate of 
soda, the point of the wire from the machine (representing the 
positive pole) put upon the litmus paper, and the receiving 
point from the discharging train (292. 316.), representing the 
negative pole, upon the turmeric paper, a very few turns of the 
machine sufficed to show the evolution of acid at the former, 
and alkali at the latter, exactly in the manner effected by a 
volta-electric current. 

455. The pieces of litmus and turmeric paper were now 
placed each upon a separate plate of glass, and connected by an 
insulated string four feet long, moistened in the same solution of 
sulphate of soda ; the terminal decomposing wire points were 
placed upon the papers as before. On working the machine, 
the same evolution of acid and alkali appeared as in the former 
instance, and with equal readiness, notwithstanding that the 
places of their appearance were four feet apart fropi each other. 
Finally, a piece of string, seventy feet long, was used. It was 
insulated in the air by suspenders of silk, so that the electricity 
passed through its entire length : decomposition took place 
exactly, as in former cases, alkali and acid appearing at the two 
extremities in their proper places. 

456. Experiments were then made both with sulphate of 
soda and iodide of potassium, to ascertain if ally diminution 
of decomposing effect was produced by such great extension as 



129 


June 1833.] Decompositions by a single pole, 

those just described of the moist conductor or body under de- 
composition ; but whether the contact of the decomposing 
point connected with* the discharging train was made with tur- 
meric paper touching the prime conductor, or with other tur- 
meric paper connected with it through the seventy feet of 
string, the spot of alkali for an equal number of turns of the 
machine had equal intensity of colour. The same results oc- 
curred §.t the ’other decomposing wire, whether the salt or the 
iodide Were used ; and it was fully proved that this great ex- 
tension of the distance between the poles produced no effect 
whatever on the amount of decomposition, provided the same 
quantity of electricity were passed in both cases (377.) . 

457. The negative point of the discharging train, the tur- 
meric paper, and the string were then removed; the positive 
point was left resting upon the litmus paper, and the latter 
touched by a piece of moistened string held in the hand. A 
few turns of the machine evolved acid at the positive point as 
freely as before. 

458. The end of the moistened string, instead of being held 
in the hand, was suspended by glass in the air. On work- 
ing the machine the electricity proceeded from the conductor 
through the wire point to the litmus paper, and thence away 
by the intervention of the string to the air, so that there was 
(as in the last experiment,) but one metallic pole; still acid 
was evolved there as freely as in any former case. 

459. When any of these experiments were repeated with 
electricity from the negative conductor, corresponding effects 
were produced whether one or two decomposing wires were 
used. The results were always constant, considered in rela- 
tion to the direction of the electric current. 

460. These experiments were varied so as to include the 
action of otily one metallic pole, but that not the pole connected 
with the machine. Turmeric paper was moistened in solution 
of sulphate of soda, placed upon glass, and connected with the 
discharging train (292.) by a decomposing wire (312.) ; a piece 
of wet string was hung from it, the lower extremity of which 
was brought opposite a point connected with the positive prime 
conductor of the machine. The machine was then worked for 
a few turns, and alkali immediately appeared at the point of 
the discharging train which rested on the turmeric paper. 



130 Electro-chemical decomposition in air . [Series V. 

Corresponding effects took place at the negative conductor of 
a machine. 

461. These cases are abundantly sufficient to show that elec- 
tro-chemical decomposition does not depend upon the simul- 
taneous action of two metallic poles, since a single pole might 
be used, decomposition ensue, and one or other of the ele- 
ments liberated, pass to the pole, according as it was positive 
or negative. In considering the course taken byi and the final 
arrangement of, the other element, I had little doubt that I 
should find it had receded towards the other extremity, and 
that the air itself had acted as a pole, an expectation which 
was fully confirmed in the following manner. 

462. A piece of turmeric paper, not more than 0*4 of an inch 
in length and 0*5 of an inch in width ,«was moistened with sul- 
phate of soda and placed upon tho edge of a glass plate oppo- 
site to, and about two inches from, a point connected with the 
discharging train (Plate IV. fig. 47.) ; a piece of tinfoil, resting 
upon the same glass plate, was connected with the machine, 
and also with the turmeric paper, by a decomposing wire a 
(312) , The machine was then worked, the positive electricity 
passing into the turmeric paper at the point p , and out at the 
extremity n. After forty or fifty turns of the machine, the ex- 
tremity n was examined, and the two points or angles found 
deeply coloured by the presence of free alkali (fig. 48.) . 

463. A similar piece of litmus paper, dipped in solution of 
sulphate of soda n , fig. 49, was now supported upon the end 
of the discharging train a , and its extremity brought opposite 
to a point p } connected with the conductor of the machine. 
After working the machine for a short time, acid was developed 
at both the corners towards the point, i. e . at both the corners 
receiving the electricities from the air. Every precaution was 
taken to prevent this acid from being formed by sparks or 
brushes passing through the air (322.) ; and these, with the 
accompanying general facts, are sufficient to show Ahat the 
acid was really the result of electro- chemical decomposition 
(466.). 

464. Then a long piece of turmeric paper, large at one end 
and pointed at the other, was moistened in the saline solution, 
and immediately connected with the conductor of the machine, 
»9 that its pointed extremity was opposite a point upon the 



June 1833.] No metallic poles used. 131 

discharging train. When the machine was worked, alkali was 
evolved at that point ; and even when the discharging train 
was removed, and the electricity left to be diffused and carried 
off altogether by the air, still alkali was evolved where the 
electricity left the turmeric paper. 

465. Arrangements were then made in which no metallic 
communication with the decomposing matter was allowed, but 
both pt>les (if they might now be called by that name,) formed 
of air only. A piece of turmeric paper a fig. 50, and a piece 
of litmus paper b , were dipped in solution of sulphate of soda, 
put together so as to form one moist pointed conductor, and 
supported on wax between two needle points, one p connected 
by a wire with the conductor of the machine, and the other, n y 
with the discharging train. The interval in each case between 
the points was about half an inch : the positive point p was 
opposite the litmus paper ; the negative point n opposite the 
turmeric. The machine was then worked for a time, upon 
which evidence of decomposition quickly appeared, for the 
point of the litmus b became reddened from acid evolved there, 
and the point of the turmeric a red from a similar and simul- 
taneous evolution of alkali. 

466. Upon turning the paper conductor round, so that the 
litmus point should now give off the positive electricity, and 
the turmeric point receive it, and working the machine for a 
short time, both the red spots disappeared, and as on continu- 
ing the action of the machine no red spot >vas rc-formed at the 
litmus extremity, it proved that in the first instance (463.) the 
effect was not due to the action of brushes or mere electric 
discharges causing the formation of nitric acid from the air 
(322.). 

467. If the combined litmus and turmeric paper in this' ex- 
periment be considered as constituting a conductor independ- 
ent of the machine or the discharging train, and the final 
places of the elements evolved be considered in relation to this 
conductor, then it will be found that the acid collects at the 
negative or receiving end or pole of the arrangement, and the 
alkali at the positive or delivering extremity. 

468. Similar litmus and turmeric paper points were now 
placed upon glass plates, and connected by a string six feet 
long, both string and paper being moistened in solution of 

& 2 



132 Polar decompositions in air . [Series V, 

sulphate of soda ; a needle point connected with the machine 
was brought opposite the litmus paper point, and ahother 
needle point connected with the discharging train brought op- 
posite the turmeric paper. On working the machine, acid ap- 
peared on the litmus, and alkali on the turmeric paper ; but 
the latter was not so abundant as in former cases, for much of 
the electricity passed off from the string into the air, and 
diminished the quantity discharged at the turmeric poinfc 

469. Finally, a series of four small compound conductors, 
consisting of litmus and turmeric paper (fig. 51.) moistened in 
solution of sulphate of soda, were supported on glass rods, in 
a line at a little distance from each other, between the points 
p and n of the machine and discharging train, so that the elec- 
tricity might pass in succession through them, entering in at 
the litmus points b , b , and passing out at the turmeric points a , 
a. On working the machine carefully, so' as to avoid sparks and 
brushes (322.), I soon obtained evidence of decomposition in 
each of the moist conductors, for all the litmus points exhibited 
free acid; and the turmeric points equally showed free alkali. 

470. On using solutions of iodide of potassium, acetate of 
lead, &c., similar effects were obtained ; but as they were all 
consistent Avitli the results above described, I refrain from de- 
scribing the appearances minutely. 

471. These cases of electro-chemical decomposition arc in 
their nature exactly of the same kind as those affected under 
ordinary circumstances by the voltaic battery, notwithstanding 
the great differences as to the presence or absence, or at least 
as to the nature of the parts usually called poles ; and also of 
the final situation of the elements eliminated at the electrified 
boundary surfaces (467.). They indicate at once an internal 
action of the parts suffering decomposition, and appear to show 
that the power which is effectual in separating the elements is 
exerted there, and not at the poles. But I shall defer the con- 
sideration of this point for a short time (493. 518.), that I may 
previously consider another supposed condition of electro- 
chemical decomposition *. 

* I find (since making and describing these results,) from a note to Sir 
Humphry Davy’s paper in the Philosophical Transactions, 1807, p. 31, that 
that philosopher, in repeating Wollaston’s experiment of the decomposition: of 
water bv common electricity (327. 330.) used an arrangement somewhat like 



June 1833.] Is water required in decompositions ? 133 

% ii. Influence of Water in Electro-chemical Decomposition . 

472. It is the opinion o£ several philosophers, that the pre- 
sence of water is essential in electro- chemical decomposition, 
and also for the evolution of electricity in the voltaic battery 
itself. As the decomposing cell is merely one of the cells of 
the battery, into which particular substances are introduced for 
the purpose qf experiment, it is probable that what is an essen- 
tial condition in the one case is more or less so in the other. The 
opinion, therefore, that water is necessary to decomposition, 
may have been founded on the statement made by Sir Humphry 
Davy, that “ there are no fluids known, except such as contain 
water, which are capable of being made the medium of connex- 
ion between the metals or metal of the voltaic apparatus * : ” and 
again, ff when any substance rendered fluid by heat, consisting 
of water , oxygen, and inflammable or metallic matter, is exposed 
to those ftires, similar phenomena (of decomposition) occur f,” 

473. This opinion has, I think, been shown by other philo- 
sophers not to be accurate, though I do not know where to 
refer for a contradiction of it. Sir Humphry Davy himself 
said in 1801 }, that dry nitre, caustic potash and soda are con- 
ductors of galvanism when rendered fluid by a high degree of 
heat ; but he must have considered them, or the nitre at least, 
as not suffering decomposition, for the statements above were 
made by him eleven years subsequently. In 1826 he also 
pointed out, that bodies not containing water, as fused litharge 
and chlorate of potassa , were sufficient to form, with platina 
and zinc, powerful electromotive circles §; but he is here speak- 
ing of the production of electricity in the pile, and not of its 
effects when evolved ; nor do his words at all imply that any 
correction of his former distinct statements relative to decom- 
position was required. 

474. I may refer to the last series of these Experimental 
some of those I have described. He immersed a guarded platina point con- 
nected with the machine in distilled water, and dissipated the electricity from 
the water into the air by moistened filaments of cotton. In this way he states 
that he obtained oxygen and hydrogen separately from each other. This ex- 
periment, had I known of it, ought to have been quoted in an earlier series of 
these Researches (342.) ; but it does not remove any of the objections I have 
made to the use of Wollaston’s apparatus as a test of true chemical action (331.). 

* Elements of Chemical Philosophy, p. 169, &c. t Ibid. pp. 144, 145. 

t Journal of the Royal Institution, 1802, p. 53. 

§ Philosophical Transactions, 1826, p. 406. 



134 Water not necessary to electro-chemical action . [Series V. 

Researches (380. 402.) as setting the matter at rest, by pro- 
ving that there are hundreds of bodies equally influential with 
water in this respect ; that amongst binary compounds, oxides, 
chlorides, iodides, and even sulphurets (402.) were effective; 
and that amongst more complicated compounds, cyanides and 
salts of equal efficacy, occurred in great numbers (402.) . 

475. Water, therefore, is in this respect merely .one of a very 
numerous class of substances, instead of being the only fwe and 
essential ; and it is of that class one of the worst as to its capa- 
bility of facilitating conduction and suffering decomposition. 
The reasons why it obtained for a time an exclusive character 
which it so little deserved are evident, and consist, in the 
general necessity of a fluid condition (394.) ; in its being the 
only one of this class of bodies existing in the fluid state at 
common temperatures ; its abundant supply as the great natu- 
ral solvent ; and its constant use in that character iff philoso- 
phical investigations, because of its having a smaller interfering, 
injurious, or complicating action upon the bodies, either dis- 
solved or evolved, than any other substance. 

476. The analogy of the decomposing or experimental cell 
to the other cells of the voltaic battery, renders it nearly cer- 
tain that any of those substances which are decomposable when 
fluid, as described in my last paper (402.), would, if they could 
be introduced between the metallic plates of the pile be equally 
effectual with water if not more so. Sir Humphry Davy found 
that litharge and chlorate of potassa were thus effectual*. I 
have constructed various voltaic arrangements, and found the 
above conclusion to hold good. When any of the following 
substances in a fused state were interposed between copper 
and platina, voltaic action more or less powerful was produced. 
Nitre ; chlorate of potassa ; carbonate of potassa ; sulphate of 
soda; chloride of lead, of sodium, of bismuth, of calcium; 
iodide of lead ; oxide of bismuth ; oxide of lead : the electric 
current was in the same direction as if acids had acted upon 
the metals. When any of the same substances, or phosphate 
of soda, were made to act on platina and iron, still m&e power- 
ful voltaic combinations of the same kind were produced* 
When either nitrate of silver or chloride of silver was the fluid 
substance interposed, there was voltaic action, but the electric 
current was in the reverse direction. 

* Philosophical Transactions, 1826, p. 406. 



J one 1833.] Electro-chemical decomposition . 135 

iii. Theory of Electro-chemical Decomposition. 

4*77 . The extreme beauty and value of electro-chemical de- 
compositions have given to that power which the voltaic pile 
possesses of causing their occurrence an interest surpass- 
ing that of any other of its properties; for the power is not 
only intimately connected with the continuance, if not with the 
produition, of the electrical phenomena, but it has furnished 
us wi£h the most beautiful demonstrations of the nature of 
many compound bodies ; has in the hands of Becquerel been 
employed in compounding substances ; has given us several 
new combinations, and sustains us with the hope that when 
thoroughly understood it will produce many more. 

478. What may be Considered as the general facts of electro- 
chemical decomposition are agreed to by nearly all who have 
written-on the subject. They consist in the separation of the 
decomposable substance acted upon into its proximate or some- 
times ultimate principles, whenever both poles of the pile are 
in contact with that substance in a proper condition ; in the 
evolution of these principles at distant points, i. e. at the poles 
of the pile, where they are either finally set free or enter into 
union with the substance of the poles ; and in the constant de- 
termination of the evolved elements or principles to particular 
poles according to certain well ascertained laws. 

479. But the views of men of science vary much as to the 
nature of the action by which these effects are produced ; and 
as it is certain that we shall be better able to apply the power 
when we really understand the manner in which it operates, 
this difference of opinion is a strong inducement to further in- 
quiry. I have been led to hope that the following investiga- 
tions might be considered, not as an increase of that which is 
doubtful, but a real addition to this branch of knowledge. 

480. It will be needful that I briefly state the views of elec- 
tro-chetnical decomposition already put forth, that their pre- 
sent contradictory and unsatisfactory state may be seen before 
I give that which seems to me more -accurately to agree with 
facts ; and I haVe ventured to discuss them freely, trusting that 
I should give no offence to their high-minded authors ; for I 
felt convinced, that if I were right, they would be pleased that 
their views should serve as stepping-stones for the advance of 



186 


Theory of Grotthuss } — of Davy, [Series V 

science ; and that if I were wrong, they would excuse the zeal 
which misled me, since it was exerted for the service of that 
great cause whose prosperity and progress tfiey have desired. 

481. Grotthuss, in the year 1805, wrote expressly on the de- 
composition of liquids by voltaic electricity* * * § . He considers 
the pile as an electric magnet, i. e. as an attractive and repul- 
sive agent; the poles having attractive and repelling powers. 
The pole from whence resinous electricity issues attracts hy- 
drogen and repels oxygen, whilst that from which vitreous elec- 
tricity proceeds attracts oxygen and repels hydrogen ; so that 
each of the elements of a particle of water, for instance, is sub- 
ject to an attractive and a repulsive force, acting in contrary 
directions, the centres of action of which are reciprocally op- 
posed. The action of each force in relation to a molecule of 
water situated in the course of the electric current is in the in- 
verse ratio of the square of the distance at which it is #ex€rted, 
thus giving (it is stated) for such a molecule a constant force f. 
He explains the appearance of the elements at a distance from 
each other by referring to a succession of decompositions and 
recompositions occurring amongst the intervening particles J, 
and he thinks it probable that those which are about to sepa- 
rate at the poles unite to the two electricities there, and in 
consequence become gases §. 

482. Sir Humphry Davy's celebrated Bakerian Lecture on 
some chemical agencies of electricity was read in November 
1806, and is almost entirely occupied in the consideration of 
electro-chemical decompositions . The facts are of the utmost 
value, and, with the general points established, are universally 
known. The mode of action by which the effects take place 
is stated very generally, so generally, indeed, that probably a 
dozen precise schemes of electro-chemical action might be 
drawn up, differing essentially from each other, yet all agree- 
ing with the statement there given. 

483. When Sir Humphry Davy uses more particular ex- 
pressions, he seems to refer the decomposing effects to the at- 
tractions of the poles. This is the case in the “ general ex- 

* Annales de Chimie, 1800, tom. lviii. p. 04. 

f Ibid. pp. 60, 67, also tom. Ixiii. p. 20. 

% Ibid. tom. lviii. p 68, tom. Ixiii, p. 20. 

§ Ibid. tom. Ixiii, p. 84. 



June 1833.] Theory of Riffault and Chompre. 


137 


pression of facts ” given at pp. 28 and 29 of the Philosophical 
Transactions for 1807, also at p. 30. Again at p. 161 of the 
Elements of Chemical Philosophy, he speaks of the great attract- 
ing powers of the surfaces of the poles. He mentions the pro- 
bability of a succession of decompositions and recompositions 
throughout the fluid, — agreeing in that respect with Grott- 
huss * ; and supposes that tlie attractive and repellent agencies 
may he communicated from the metallic surfaces throughout 
the whole of the menstruum f, being communicated from one 
particle to another particle of the same kind J, and diminishing 
in strength from the place of the poles to the middle point, which 
is necessarily neutral §. In reference to this diminution of power 
at increased distances from the poles, he states that in a circuit 
of ten inches of water, solution of sulphate of potassa placed 
four inches from the positive pole, did not decompose; whereas 
when." only two inches from that pole, it did render up its 
elements ||. 

484. When in 1826 Sir Humphry Davy wrote again on this 
subject , he stated that he found nothing to alter in the funda- 
mental theory laid down in the original communication If, and 
uses the terms attraction and repulsion apparently in the same 
sense as before **. 

485. Messrs. Riffault and Chompre experimented on this 
subject in 1807. They came to the conclusion that the voltaic 
current caused decompositions throughout its whole course in 
the humid conductor, not merely as preliminary to the recom- 
positions spoken of by Grotthuss and Davy, but producing final 
separation of the elements in the course of the current, and 
elsewhere than at the poles. They considered the negative 
current as collecting and carrying the acids, &c., to the positive 
pole, and the positive current as doing the same duty with the 
bases, and collecting them at the negative pole. They likewise 
consider the currents as more powerful the nearer they are to 
their respective poles, and state that the positive current is 
supeHor in power to the negative current ft* 

486. M. Biot is very cautious in expressing an opinion as to 


* Philosophical Transactions, 1807, pp. 29, 30. 

4 Ib d. p, 29. § Ibid. p. 42. 

11 Ibid. 1820, p, 383. . ** Ibid. pp. 389, 407, 415. 

TT Annales de Chimie, 1807, tom. lxiii. p, 83, &c. 


t Ibid. p. 89. 
|| Ibid. p. 42. 



138 Theory of Biot . [Series V. 

the cause of the separation of the elements of a compound 
body*. But as far as the effects can be understood, he refers 
them to the opposite electrical states of the portions of the de- 
composing substance in the neighbourhood of the two poles. 
The fluid is most positive at the positive pole ; that state gra- 
dually diminishes to the middle distance, where the fluid is 
neutral or not electrical ; but from thence to the negative pole 
it becomes more and more negative f. When a partible in 
salt is decomposed at the negative pole, the acid particle is 
considered as acquiring a negative electrical state from the pole, 
stronger than that of the surrounding undecomposed particles, 
and is therefore repelled from amongst them, and from out of 
that portion of the liquid towards the positive pole, towards 
which also it is drawn by the attraction of the pole itself and 
the particles of positive undecomposed fluid around it J. 

487. M. Biot does not appear to admit the successive de- 
compositions and recompositions spoken of by Grotthuss, Davy, 
&c. &c. ; but seems to consider the substance whilst in transit 
as combined with, or rather attached to, the electricity for the 
time§, and though it communicates this electricity to the sur- 
rounding undecomposed matter with which it is in contact, yet 
it retains during the transit a little superiority with respect to 
that kind which it first received from the pole, and is, by virtue 
of that difference, carried forward through the fluid to the op- 
posite pole || . 

488. This theory implies that decomposition takes place at 
both poles upon distinct portions of fluid^ and not at all in the 
intervening parts. The latter serve merely as imperfect con- 
ductors, which, assuming an electric state, urge particles elec- 
trified more highly at the poles through them in opposite direc- 
tions, by virtue of a series of ordinary electrical attractions and 
repulsions^. 

489. M. A. de la Rive investigated this subject particularly, 
and published a paper on it in 1825**. He thinks those who 
have referred the phenomena to the attractive powers of the 
poles, rather express the general fact than give any expfeation 

* Precis Etementaire de Physique, 8 me Edition, 1824, tom. i. p. 641. 

t Ibid. p. 637. t Ibid. pp. 641, 642. § Ibid, p, 686. 

j| Ibid. p. 642. 51 Ibid. pp. 683, 642. 

** Annaiea de Chimie, tom. xxviii. p. 190. 



139 * 


June 1833.] Theory of De la Rive , — of Hachette . 

of it. He considers the results as due to an actual combination 
of the elements, or rather of half of them, with the electricities 
passing from the poles in consequence of a kind of play of 
affinities between the matter and electricity*. The current 
from the positive pole combining with the hydrogen, or the 
bases it finds there, leaves^the oxygen and acids at liberty, but 
carries the substances it is united with across to the negative 
pole, where, because of the peculiar character of the metal as 
a conduct orf, it is separated from them, entering the metal 
and leaving the hydrogen or bases upon its surface. In the 
same manner the electricity from the negative pole sets the 
hydrogen and bases which it finds there, free, but combines 
with the oxygen and acids, carries them across to the positive 
pole, and there deposits themj. In this respect M. de la Rive's 
hypothesis accords in part with that of MM. Riffault and 
Choinprd (485.). 

490. M. de la Rive considers the portions of matter which 
are decomposed to be those contiguous to both poles §. He 
does not admit with others the successive decompositions and 
recompositions in the whole course of the electricity through 
the humid conductor ||, but thinks the middle parts are in them- 
selves unaltered, or at least serve only to conduct the two con- 
trary currents of electricity and matter which set off: from the 
opposite poles^f. The decomposition, therefore, of a particle 
of water, or a particle of salt, may take place at either pole, 
and when once effected, it is final for the time, no recombina- 
tion taking place, except the momentary union of the transferred 
particle with the electricity be so considered. 

491. The latest communication that I am aware of on the 
subject is by M. Hachette : its date is October 1832**. It is 
incidental to the description of the decomposition of water by 
the magneto-electric currents (346.). One of the results of the 
experiment is, that “ it is not necessary, as has been supposed, 
that for the chemical decomposition of water, the action of the 
two electricities, positive and negative, should b6 simultaneous." 

492* It is more than probable that many other views of elec- 
tro-chemical decomposition may have been published, and per- 
haps amongst them some which, differing from those above, 

* Annaies de Chimie, tom. xxviii. pp. 200, 202. 

t Ibid. p. 20 2. % Ibid. p. 201. 

II Ibid. pp. 192, 199. f Ibid. p. 200. 


§ Ibid. pp. 197, 198. 
** Ibid, tom, li. p. 78. 



140 Theory of electro -chemical decomposition, [Series Y. 

might, even in my own opinion, were I acquainted with them, 
obviate the necessity for publication of my views. If such 
be the case, I have to regret my ignorance of them, and apolo- 
gize to the authors. 

493. That electro-chemical decomposition does not depend 
upon any direct attraction and repulsion oh the poles (meaning 
thereby the metallic terminations either of the voltaic battery, 
or ordinary electrical machine arrangements (312), ) upon the 
elements in contact with or near to them, appeared very evident 
from the experiments made in air (462, 465, &c.), when the 
substances evolved did not collect about any poles, but, in 
obedience to the direction of the current, were evolved, and I 
would say ejected, at the extremities of the decomposing sub- 
stance. But notwithstanding the extreme dissimilarity in the 
character of air and metals, and the almost total difference ex- 
isting between them as to their mode of conducting electricity, 
and becoming charged with it, it might perhaps still be contended, 
although quite hypothetically, that the bounding portions of 
air were now the surfaces or places of attraction, as the metals 
had been supposed to be before. In illustration of this and 
other points, I endeavoured to devise an arrangement by which 
I could decompose a body against a surface of water, as well 
as against air or metal, and succeeded in doing so unexception- 
ably in the following manner. As the experiment for very 
natural reasons requires many precautions, to be successful, 
and will be referred to hereafter in illustration of the views I 
shall venture to give, I must describe it minutely. 

494. A glass basin (fig. 52.), four inches in diameter and 
four inches deep, had a division of mica a , fixed across the upper 
part so as to descend one inch and a half below the edge, and 
be perfectly water-tight at the sides : a plate of platina b , three 
inches wide, was put into the basin on one side of the division 
a, mid retained there by a glass block below, so that any gas 
produced by it in a future stage of the experiment should not 
ascend beyond the mica, and cause currents in the liquid on 
that side. A strong solution of sulphate of magnesia was care- 
fully poured without splashing into the basin, until it rose a 
little above the lower edge of the mica division a, great care 
being taken that the glass or mica on the unoccupied or c side 
of the division in the figure, should not be moistened by agita- 



141 


June 1833.] Decomposition against a water-pole • 

tion of the solution above the level to which it rose. A thin 
piece of clean cork, well wetted in distilled water, was then 
carefully and lightly placed on the solution at the c side, and 
distilled water poured gently on to it until a stratum the eighth 
of an inch in thickness appeared over the sulphate of magnesia ; 
all was then left fo r a few ^ minutes. that any solution adhering 
to the cork might Sunk away from it, or be removed by the 
water # on which it now floated; and then more distilled water 
was a&ded in a similar manner, until it reached nearly to the 
top of the glass. In this way solution of the sulphate occupied 
the lower part of the glass, and also the upper on the right hand 
side of the mica ; but on the left hand side of the division a 
stratum of water from c to d> one inch and a half in depth, re- 
posed upon it, the two presenting, when looked through hori- 
zontally, a comparatively definite plane of contact. A second 
platiu? pole e, was arranged so as to be just under the surface 
of the water, in a position nearly horizontal, a little inclination 
being given to it, that gas evolved during decomposition might 
escape : the part immersed was three inches and a half long by 
one inch wide, and about seven eighths of an inch of water in- 
tervened between it and the solution of sulphate of magnesia. 

495. The latter pole e was now connected with the negative 
end of a voltaic battery^ of forty pairs of plates four inches 
square, whilst the former pole b was connected with the posi- 
tive end. There was action and gas evolved at both poles ; 
but from the intervention of the pure water, the decomposition 
Mas very feeble compared to what the battery would have 
effected in a uniform solution. After a little while (less than 
a minute), magnesia also appeared at the negative side : it did 
not make its appearance at the negative metallic pole , but in 
the water , at the plane where the solution and the water met ; 
and on looking at it horizontally, it could be there perceived 
lying in the "water upon the solution, not rising more than the 
fourth of an inch above the latter, whilst the water between it 
and the negative pole was perfectly clear. On. continuing the 
action, the bubbles of hydrogen rising upwards from the nega- 
tive pole impressed a circulatory movement on the stratum 
of water, upwards in the middle, and downwards at the 
side, which gradually gave an ascending, form to the cloud of 
magnesia in the part just under the pole, having an appearance 



142 Decomposition against mater or air . [Series V. 

as if it were there attracted to it ; but this was altogether an 
effect of the currents, and did not occur until long after the 
phenomena looked for were satisfactorily ascertained, 

496. After a little while the voltaic communication was 
broken, and the platina poles removed with as little agitation 
as possible from the water and solpliQTU* for the purpose of 
examining the liquid adhering to them. The pole e , when 
touched by turmeric paper, gave no trace of alkali, norc could 
anything but pure water be found upon it. The pole b t though 
drawn through a much greater depth and quantity of fluid, was 
found so acid as to give abundant evidence to litmus paper, the 
tongue, and other tests. Hence there had been no interference 
of alkaline salts in any way, undergoing first decomposition, 
and then causing the separation of the magnesia at a distance 
from the pole by mere chemical agencies. This experiment 
was repeated again and again, and always successfully. ’ 

497. As, therefore, the substances evolved in cases of electro- 
chemical decomposition may be made to appear against air 
(465. 469.), — which, according to common language, is not a 
conductor, nor is decomposed, or against water (495.), which 
is a conductor, and can be decomposed, — as well as against 
the metal poles, which are excellent conductors, but undecom- 
posable, there appears but little reason to consider the pheno- 
mena generally, as due to the attraction or attractive powers 
of the latter, when used in the ordinary way, since similar at- 
tractions can hardly be imagined in the former instances. 

498. It may be said that the surfaces of air or of water in 
these cases become the poles, and exert attractive powers ; but 
what proof is there of that, except the fact that the matters 
evolved collect there, which is the point to be explained, and 
cannot be justly quoted as its own explanation ? Or it may be 
said, that any section of the humid conductor, as that in the 
present case, where the solution and the water meet, may be 
considered as representing the pole. But such does not appear- 
to me to be the view of those who have written on the subject, 
certainly not of some of them, and is inconsistent with the sup- 
posed laws which they have assumed, as governing the diminution 
of power at increased distances from the poles. 

499. Grotthuss, for instance, describes the poles as centres 
of attractive and repulsive forces (481.), these forces varying 



June 1833.]' Theories of electro-chemical decomposition . 143 

inversely as the squares of the distances, and says, therefore, 
that a particle placed anywhere between the poles will be acted 
upon by a constant %rce. But the compound force, resulting 
from such a combination as he supposes, would be anything 
but a constant force ; it would evidently be a force greatest at 
the poles, and dimin^ing to the middle distance. Grotthuss 
is right, however, m the fact , according to my experiments 
(502. «505.), that the particles are acted upon by equal force 
everywhere in the circuit, when the conditions of the experi- 
ment are the simplest possible ; but the fact is against his theory, 
and is also, I think, against all theories that place the decom- 
posing effect in the attractive power of the poles. 

500. Sir Humphry Davy, who also speaks of the diminution 
of power with increase ftf distance from the poles* (483.), sup- 
poses, that when both poles are acting on substances to decom- 
pose Tfeem, still the power of decomposition diminishes to the 
middle distance. In this statement of fact he is opposed to 
Grotthuss, and quotes an experiment in which sulphate of 
potassa, placed at different distances from the poles in a humid 
conductor of constant length, decomposed w hen near the pole, 
but not when at a distance. Such a consequence would neces- 
sarily result theoretically from considering the poles as cen- 
tres of attraction and repulsion; but I have not found the 
statement borne out by other experiments (505.) ; and in the 
one quoted by him the effect was doubtless due to some of the 
many interfering causes of variation w hich attend such investi- 
gations. 

501. A glass vessel had a platina plate fixed perpendicularly 
across it, so as to divide it into two cells : a head of mica was 
fixed over it, so as to collect the gas it might evolve during ex- 
periments ; then each cell, and the space beneath the mica, was 
filled with dilute sulphuric acid. Two poles were provided, 
consisting each of a platina wire terminated by a plate of the 
same metal; each was fixed into a tube passing through its 
upper end by an air-tight joint, that it might be moveable, and 
yet that the gas evolved at it might be collected. The tubes 
were filled with the acid, and one immersed in each cell. Each 
platina pole was equal in surface to one side of the dividing 
plate in the middle glass vessel, and the whole might be coti- 

* Philosophical Transactions, 1807, p. 42. 



144 Strength of the decomposing force. [Series V 

sidered as an arrangement between the poles of the battery of 
a humid decomposable conductor divided in the middle by the 
interposed platina diaphragm. It was easy, when required, to 
draw one of the poles further up the tube, and then the platina 
diaphragm was no longer in the middle of the humid conductor. 
But whether it was thus arrange d at the middle, or towards 
one side, it always evolved a quanfity of oxygen and hydrogen 
equal to that evolved by the extreme plates*. 

502. If the wires of a galvanometer be terminated by*plates, 
and these be immersed in dilute acid, contained in a regularly 
formed rectangular glass trough, connected at each end with a 
voltaic battery by poles equal to the section of the fluid, a part 
of the electricity will pass through the instrument and cause a 
certain deflection. And if the plates are always retained at the 
same distance from each other, and from the sides of the trough, 
are always parallel to each other, and uniformly placed jmiiitive 
to the fluid, then, whether they are immersed near the middle 
of the decomposing solution, or at one end, still the instrument 
will indicate the same deflection, and consequently the same 
electric influence. 

503. It is very evident, that when the width of the decom- 
posing conductor varies, as is always the case when mere wires 
or plates, as poles, are dipped into or are surrounded by solu- 
tion, no constant expression can be given as to the action upon 
a single particle placed in the course of the current, nor any 
conclusion of use, relative to the supposed attractive or repul- 
sive force of the poles, be drawn. The force will vary as the 
distance from the pole varies ; as the particle is directly between 
the poles, or more or less on one side ; and even as it is nearer 
to or further from the sides of the containing vessels, or as the 
shape of the vessel itself varies ; and, in fact by making 
variations in the form of the arrangement, the force upon any 
single particle may be made to increase, or diminish, or remain 
constant, whilst the distance between the particle and the pole 
shall remain the same ; or the force may be made to increase, 
or diminish, or remain constant, either as the distance increases 
or as it diminishes. 

* There are certain precautions, in this and such experiments, which can 
only be understood and guarded against by a knowledge of the phenomena to 
be described in the first part of the Sixth Series of these Researches. 



June 1833.] Constant chemical action of electricity r 145 

504. From numerous experiments, I am led to believe the 
following general expression to be correct ; but I purpose ex- 
amining it much further, and would therefore wish not to be 
considered at present as pledged to its accuracy. The sum of 
chemical decomposition is constant for any section taken across 
a decomposing cond , ^uniform in its nature, at whatever 
distance the poles may be from each other or from the section ; 
or hoover that section may intersect the currents, whether 
directly across them, or so oblique as to reach almost from pole 
to pole, or whether' it be plain, or curved, or irregular in the 
utmost degree ; provided the current of electricity be retained 
constant in quantity (377.), and that the section passes through 
every paid of the current through the decomposing conductor. 

505. I have reason to believe that the statement might be 
made still more general, and expressed thus : That for a con- 
stant qfotmtity of electricity , whatever the decomposing con- 
ductor may be, whether water , saline solutions , acids, fused 
bodies , fyc., the amount of electro -chemical action is also a 
constant quantity , i. e . would always be equivalent to a stand- 
ard chemical effect founded upon ordinary chemical affinity . 
I have this investigation in hand, with several others, and shall 
be prepared to give it in the next series but one of these Re- 
searches. 

506. Many other argument^ might be adduced against the 
hypotheses of the attraction of the poles being the cause of 
electro- chemical decomposition; but I would rather pass on to 
the view I have thought more consistent with facts, with this 
single remark ; that if decomposition by the voltaic battery 
depended upon the attraction of the poles, or the parts about 
them, being stronger than the mutual attraction of the particles 
separated, it would follow that the weakest electrical attraction 
was stronger than, if not the strongest, yet very strong chemical 
attraction, namely, such as exists between oxygen and hydrogen, 
potassium and oxygen, chloride and sodium, acid and alkali, 
&c., a consequence which, * although perhaps not impossible, 
seems in the present state of the subject very unlikely. 

507. The view which M. De la Rive has taken (489.), and 
also MM. Riffault and Chompr^ (485.), of the manner in which 
electro-chemical decomposition is effected, is very different to' 
that already . considered, and is not affected by either the argu- 



146 Theory of electro-chemical decomposition. [Sebies V . 

ments or facts urged against the latter. Considering it as gtated 
by the former philosopher, it appears to me to be incompetent 
to account for the experiments of decomposition against surfaces 
of air (462. 469.) and water (495.), which I have described; for 
if the physical differences between metals and humid con- 
ductors, which M. de la Rive supposes ie -account for the trans- 
mission of the compound of matter and electricity in the latter, 
and the transmission of the electricity only with the rejection 
of the matter in the former, be allowed for a moment, still the 
analogy of air to metal is, electrically considered, so small, that 
instead of the former replacing the latter (462.), an effect the 
very reverse might have been expected. Or if even that were 
allowed, the experiment with water (495.) at once sets the matter 
at rest, the decomposing pole being n6w of a substance which 
is admitted as competent to transmit the assumed compound of 
electricity and matter. 

508. With regard to the views of MM. Riffault and Chompre 
(485.), the occurrence of decomposition alone in the course of 
the current is so contrary to the well-known effects obtained in 
the forms of experiment adopted up to this time, that it must 
be proved before the hypothesis depending on it need be con- 
sidered. 

509. The consideration of the various theories of electro- 
chemical decomposition, whilst it has made me diffident, has 
also give me confidence to add another to the number ; for it is 
because the one I have to propose appears, after the most atten- 
tive consideration, to explain and agree with the immense collec- 
tion of facts belonging to this branch of science, and to remain 
uncontradicted by, or unopposed to, any of them, that I have 
been encouraged to give it. 

510. Electro- chemical decomposition is well-known to depend 
essentially upon the current of electricity. I have shown that in 
certain cases (375.) the decomposition is proportionate to the 
quantity of electricity passing, whatever may be its intensity or 
its source, and that the same is probably true for all cases (377.), 
even when the utmost generality is taken on the one hand, and 
great precision of expression on the other (505.). 

511. In speaking of the current, I find myself obliged to be 
still more particular than on a former occasion (283.), in conse- 
quence of the variety of views 'taken by philosophers, all agree"- 



147 


June 1833.} Various views of the electric current, 

mg in the effect of the current itself. Some philosophers, with 
Franklin, assume bryt one electric fluid ; and such must agree 
together in the general uniformity and character of the electric 
current. Others assume two electric fluids ; and here singular 
differences have arisen, 

512. MM. Riffault and Chpmpre, for instance, consider the 
positive and negative currents each as causing decomposition, 
and st^fe that the positive current is more powerful than the 
negative current*; the nitrate of soda being, under similar cir- 
cumstances, decomposed by the former, but not by the latter. 

513. M. Hachette states f that “ it is not necessary, as has 
been believed, that the action of the two electricities, positive 
and negative, should be simultaneous for the decomposition of 
water/'* The passage implying, if I have caught the meaning 
aright, that one electricity can be obtained, and can be applied 
in effecting decompositions, independent of the other. 

514. The view of M. de la Hive to a certain extent agrees 
with that of M. Hachette, for he considers that the two elec- 
tricities decompose separate portions of water (490.) %. In one 
passage lie speaks of the two electricities as two influences, 
wishing perhaps to avoid offering a decided opinion upon the 
independent existence of electric fluids ; but as these influences 
are considered as combining with the elements set free as by a 
species of chemical affinity, and for the time entirely masking 
their character, great vagueness of idea is thus introduced, in- 
asmuch as such a species of combination can only be conceived 
to take place between things having independent existences. 
The two elementary electric currents, moving in opposite direc- 
tions, from pole to pole, constitute the ordinary voltaic current . 

515. M. Grotthuss is inclined to believe that the elements of 
water, when about to separate at the poles, combine with the 
electricities, and so become gases. M. dc la Rive's view is the 
exact reverse of this : whilst passing through the fluid, they are, 
according to him, compounds with the electricities ; when evolved 
at the poles, they are de- electrified. 


510. I have sought amongst the various experiments quoted 

* Ammles de Cliimie, 1807, tom. lxiii. p, 84. f Ibid. 1832, tom. lkp. 73. 

% Ibid. 1825, tom. xxviii. pp. 107, 201. 



148 Constant nature of the electric current . [Sbkiks V. 

in support of these views, or connected with electro-chemical 
decompositions or electric currents, for c any which might be 
considered as sustaining the theory of two electricities rather 
than that of one, but have not been able to perceive a single 
fact which could be brought forward for such a purpose : or, 
admitting the hypothesis of two ^electricities, much lOss have I 
been able to perceive the slightest grounds for believing that one 
electricity in a current can be more powerful than the other, or 
that it can be present without the other, or that one can be 
varied or in the slightest degree affected, without a correspond- 
ing variation in the other*. If, upon the supposition of two elec- 
tricities, a current of one can be obtained without the other, or 
the current of one be exalted or diminished more than the other, 
we might surely expect some variation either of the chemical or 
magnetical effects, or of both ; but no such variations hpve been 
observed. If a current be so directed that it may act chemically 
in one part of its course, and magnetically in another, the two 
actions are always found to take place together. A current has 
not, to my knowledge, been produced which could act chemi- 
cally and not magnetically, nor any which can act on the magnet, 
and not at the same time chemically t. 

517. Judging from facts only , there is not as yet the slightest 
reason for considering the influence which is present in what we 
call the electric current, — whether in metals or fused bodies or 
humid conductors, or even in air, flame, and rarefied elastic media, 
— as a compound or complicated influence. It has never been 
resolved into simpler or elementary influences, and may perhaps 
best be conceived of as an axis of power having contrary forces , 
exactly equal in amount , in contrary directions . 


518. Passing to the consideration of electro- chemical decom- 
position, it appears to me that the effect is produced by an in- 
ternal corpuscular action , exerted according to the direction of 
the electric current, and that it is due to a force either super- 
added to , or giving direction to the ordinary chemical affinity 
of the bodies present. The body under decomposition may be 

* Bee How in relation to this subject, 1027 — lMd.—JDec. 1838. 
t Thermo-electric currents are of course no exception, because when they 
fail to act chemically they also fail to he eunents. 



June 1833.] Theory of electro-chemical decomposition. 149 

considered as a mass of acting particles, all those which are in- 
cluded in the course (*f the electric current contributing to the 
final effect ; and it is because the ordinary chemical affinity is 
relieved, weakened, or partly neutralized by the influence of 
the electric current in one direction parallel to the course of 
the latter, and strengthened or added to in the opposite direc- 
tion, that the -combining particles have a tendency to pass in 
opposite courses. 

519. In this view the effect is considered as essentially de- 
pendent upon the mutual chemical affinity of the particles of 
opposite kinds. Particles a a , fig. 53, could not be transferred 
or travel from one pole N towards the other P, unless they 
found particles of the opposite kind b b f ready to pass in the 
contrary direction : for it is by virtue of their increased affinity 
for tho.^ particles, combined with their diminished affinity for 
such as are behind them in their course, that they arc urged 
forward : and when any one particle a , fig. 54, arrives at the 
pole, it is excluded or set free, because the particle b of the 
opposite kind, with which it was the moment before in combi- 
nation, has, under the superinducing influence of the current, 
a greater attraction for the particle a , which is before it in its 
course, than for the particle a, towards which its affinity has 
been weakened. 

520. As far as regards any single compound particle, the 
case may be considered as analogous to one of ordinary decom- 
position, for in fig. 54, a may be conceived to be expelled from 
the compound a b by the superior attraction of a' for b , that 
superior attraction belonging to it in consequence of the relative 
position of a’ b and a to the direction of the axis of electric 
power (517.) superinduced by the current. But as all the com- 
pound particles in the course of the current, except those 
actually in contact with the poles, act conjointly, and consist of 
elementary particles, which, whilst they are in one direction ex- 
pelling, are in the other being expelled, the case becomes more 
complicated* but not more difficult of comprehension. 

521. It is not here assumed that the acting particles must be 
in a right line between the poles. The lines of action which 
may be supposed to represent the electric currents passing 
through a decomposing liquid, have in many experiments very 
irregular \ and even in the simplest case of two wires or 
points immersed as poles in a drop or larger single portion of 



150 


Theory of electro-chemical decomposition. [Series V . 


fluid, these lines must diverge rapidly from the poles ; and the 
direction in which the chemical affinity between particles is most 
powerfully modified (519. 520.) will vary with the direction of 
these lines, according constantly with them. But even in refer- 
ence to these lines or currents, it is not supposed that the par- 
ticles which mutually affect each other- must of necessity be 
parallel to them, but only that they shall accord generally with 
their direction. Two particles, placed in a line perpendicular 
to the electric current passing in any particular place, are not 
supposed to have their ordinary chemical relations towards each 
other affected ; but as the line joining them is inclined one way 
to the current their mutual affinity is increased ; as it is inclined 
in the other direction it is diminished and the effect is a max-'' 
imum, when that line is parallel to the current *. 

522. That the actions, of whatever kind they mayj^e, take 
place frequently in oblique directions is evident from the cir- 
cumstance of those particles being included which in numerous 
cases are not in a line between the poles. Thus, when wires are 
used as poles in a glass of solution, the decompositions and re- 
compositions occur to the right or left of the direct line between 
the poles, and indeed in every part to which the currents ex- 
tend, as is proved by many experiments, and must therefore 
often occur between particles obliquely placed as respects the 
current itself ; and when a metallic vessel containing the solution 
is made one pole, whilst a mere point or wire is used for the 
other, the decompositions and recompositions must frequently 
be still more oblique to the course of the currents. 

523. The theory which I have ventured to put forth (almost) 
requires an admission, that in a compound body capable of elec- 
tro-chemical decomposition the elementary particles have a mu- 
tual relation to, and influence upon each other, extending 
beyond those with which they are immediately combined. Thus 
in water, a particle of hydrogen in combination with oxygen is 
considered as not altogether indifferent to other particles of 
oxygen, although they are combined with other particles of 
hydrogen ; but to have an affinity or attraction towards them, 
which, though it does not at all approach in force, under ordi- 
nary circumstances, to that by which it is combined with its 
own particle, can, under the electric influence, exerted hi a defi- 


„ * In JJ ference 10 thia subject see now electrolytic induction and diecfaaim 
Senei XII. If viiL 1843—1361, &c.—I)ec, 1888. * 



June 1833.] Theory of electro-chemical decomposition. 151 

nite direction, be made even to surpass it. This general rela- 
tion of particles already in combination to other particles with 
which they are not combined, is sufficiently distinct in nume- 
rous results of a purely chemical character ; especially in those 
where partial decompositions only take place, and in Berthollet's 
experiments on the effects of quantity upon affinity : and it 
probably has a direct relation to, and connexion with, attraction 
of aggregation, both in solids and fluids. It is a remarkable 
circumstance, that in gases and vapours, where the attraction 
of aggregation ceases, there likewise the decomposing powers 
of electricity apparently cease, and there also the chemical 
action of quantity is no longer evident. It seems not unlikely, 
that the inability to suffer decomposition in these cases may be 
dependent upon the absfcnce of that mutual attractive relation 
of the particles which is the cause of aggregation. 

524.**i hope I have now distinctly stated, although in general 
terms, the view I entertain of the cause of clectro-cliemical de- 
composition, as far as that cause can at present he traced and 
understood . I conceive the effects to arise from forces which 
are internal , relative to the matter under decomposition — and 
not external, as they might be considered, if directly dependent 
upon the poles. I suppose that the effects are due to a modi- 
fication, by the electric current, of the chemical affinity of the 
particles through or by which that current is passing, giving 
them the power of acting more forcibly in one direction than in 
another, and consequently making them travel by a series of 
successive decompositions and recompositions in opposite di- 
rections, aqd finally causing their expulsion or exclusion at the 
boundaries of the body under decomposition, in the direction 
of the current, and that in larger or smaller quantities, according 
as the current is more or less powerful (377.). I think, there- 
fore, it would, be more philosophical, and more directly express- 
ive of the facts, to speak of such a body, in relation to the cur- 
rent passing through it, rather than to the poles, as they are 
usually called in contact with it ; and say that whilst under de- 
composition, oxygen, chlorine, iodine, acids, &c., are rendered 
at "its negative extremity, and combustibles, metals, alkalies, 
bases, &e,, at its positive extremity (467.). I do not believe 
that a- substance can be transferred in the electric current be- 
yond the point where it ceases to find particles with which it 
•can combine s anud I may refer to the experiments made in air 



152 


Transference of acid and alkali. [Series V, 

(465.), and in water (495.), already quoted, for facts illustrating 
these views in the first instance ; to which I will now add others. 

525. In order to show the dependence of the decomposition 
and transfer of elements upon the chemical affinity of the sub- 
stances present, experiments were made upon sulphuric acid in 
the following manner. Dilute sulphuric acid was prepared : 
its specific gravity was 1021 *2. A solution of sulphate of soda 
was also prepared, of such strength that a measure of dt con- 
tained exactly as much sulphuric acid as an equal measure of 
the diluted acid just referred to. A solution of pure soda, and 
another of pure ammonia, were likewise prepared, of such 
strengths that a measure of either should be exactly neutralized 
by a measure of the prepared sulphuric acid. 

526. Four glass cups were then arranged, as in fig. 55 ; 
seventeen measures of the free sulphuric acid (525.) were put 
into each of the vessels a and b } and seventeen measures of the 
solution of sulphate of soda into each of the vessels A and B. 
Asbcstus, which had been well washed in acid, acted upon by 
the voltaic pile, well washed in water, and dried by pressure, 
was used to connect a with b and A with B, the portions being 
as equal as they could be made in quantity, and cut as short as 
was consistent with their performing the part of effectual com- 
munications. b and A were connected by two platina plates 
or poles soldered to the extremities of one wire, and the cups a 
and B were by similar platina plates connected with a voltaic 
battery of forty pairs of plates four inches square, that in a 
being connected with the negative, and that in B with the posi- 
tive pole. The battery, which was not powerfully charged, was 
retained in communication above half an hour. In this manner 
it was certain that the same electric current had passed through 
a b and A B, and that in each instance the same quantity and 
strength of acid had been submitted to its action, but in one 
case merely dissolved in water, and in the other dissolved and 
also combined with an alkali. 

527 . On breaking the connexion with the battery , the por- 
tions of asbestus were lifted out , and the drops hanging at the 
ends allowed to fall each into its respective vessel. The acids 
in a and b were then first compared, for which purpose two 
evaporating dishes were balanced, and the acid from « put into 
one, and that from b into the other; but as one was a little 
heavier than the other, a small drop was transferred from the 



153 


June 1833.] Transference of acid and alkali. 

heavier to the lighter, and the two rendered equal in weight. 
Being neutralized by^the addition of the soda solution (525.), 
that from a , or the negative vessel, required 15 parts of the 
soda solution, and that from b y or the positive vessel, required 
16*3 parts. That the sum of these is not 34 parts is prin- 
cipally due to the acid removed with the asbestus; but 
taking the mean of 1565 parts, it would appear that a 
twenty*fourth part of the acid originally in the vessel a had 
passed, through the influence of the electric current, from a 
into b. 

528. In comparing the difference of acid in A and B, the 
necessary equality of weight was considered as of no conse- 
quence, because the solution was at first neutral, and would 
not, therefore, affect the test liquids, and all the evolved acid 
would be in B, and the free alkali in A. The solution in A re- 
quired b‘2 measures of the prepared acid (525.) to neutralize it, 
and the solution in B required also 3‘2 measures of the soda 
solution (525.) to neutralize it. As the asbestus must have re- 
moved a little acid and alkali from the glasses, these quantities 
are by so much too small ; and therefore it would appear that 
about a tenth of the acid originally in the vessel A had been 
transferred into B during the continuance of the electric action. 

529. In another similar experiment, whilst a thirty -fifth part 
of the acid passed from a to b in the free acid vessels, between 
a tenth and an eleventh passed from A to B in the combined acid 
vessels. Other experiments of the same kind gave similar results. 

530. The variation of electro-chemical decomposition, the 
transfer of elements and their accumulation at the poles, accord- 
ing as the substance submitted to action consists of particles 
opposed more or less in their chemical affinity, together with 
the consequent influence of the latter circumstances, are suf- 
ficiently obvious in these cases, where sulphuric acid is acted 
upon in the Same quantity by . the same electric current, but in 
one case opposed to the comparatively weak affinity of water for 
it, and in the. other to the stronger one of soda. . In the latter 
case the quantity transferred is from two and a half to three 
times what it is in the former ; and it appears therefore very 
evident that the transfer is greatly dependent upon the mutual 
action of the particles of the decomposing bodies*. 

' * Bee the note to (675).— Dec. 1838, 



154 Transference of acids and bases [Series V. 

531 . In some of the experiments the acid from the vessels a 
and b was neutralized by ammonia, then gvaporated to dryness, 
heated to redness, and the residue examined for sulphates. In 
these cases more sulphate was always obtained from a than 
from b ; showing that it had been impossible to exclude saline 
bases (derived from the asbcstus, the glass, or perhaps impuri- 
ties originally in the acid,) and that they had helped in trans- 
ferring the acid into But the quantity was small, £nd the 
acid was principally transferred by relation to the water pre- 
sent. 

532. I endeavoured to arrange certain experiments by which 
saline solutions should be decomposed against surfaces of water ; 
and at first worked with the electric machine upon a piece of 
bibulous paper, or asbestus moistened in the solution, and in 
contact at its two extremities with pointed pieces of paper 
moistened in pure water, which served to carry the elecfric cur- 
rent to and from the solution in the middle piece. But I found 
numerous interfering difficulties. Thus, the water and solutions 
in the pieces of paper could not be prevented from mingling at 
the point where they touched. Again, sufficient acid could be 
derived from the paper connected with the discharging train, 
or it may be even from the air itself, undor the influence of 
electric action, to neutralize the alkali developed at the positive 
extremity of the decomposing solution, and so not merely pre- 
vent its appearance, but actually transfer it on to the metal ter- 
mination : and, in fact, when the paper points were not allowed 
to touch there, and the machine was worked until alkali was 
evolved at the delivering or positive end of the turmeric paper, 
containing the sulphate of soda solution, it was merely neces- 
sary to place the opposite receiving point of the paper connected 
with the discharging train, which had been moistened by distil- 
led water, upon the brown turmeric point and press them to- 
gether, when the alkaline effect immediately disappeared. 

533. The experiment with sulphate of magnesia already de- 
scribed (495.) is a case in point, however, and shows most clearly 
that the sulphuric acid and magnesia contributed to each 
other's transfer and final evolution, exactly as the same add and 
soda affected each other in the results just given (527, &c.) ; 
and that so soon as the magnesia advanced beyond the reach of 
the acid, and found no other substance with which it could 



155 


June 1833.] Evolution of bodies at the poles . 

combine, it appeared in its proper character, and was no longer 
able to continue its progress towards the negative pole. 

534. The theory I have ventured to put forth appears to me 
to explain all the prominent features of electro-chemical decom- 
position in a satisfactory manner. 

535. In the first place, it explains why, in all ordinary cases, 
the ewolved substances appear only at the poles ; for the poles 
are the limiting surfaces of the decomposing substance, and ex- 
cept at them, every particle finds other particles having a con- 
trary tendency with which it can combine. 

536. Then it explains why, in numerous cases, the elements 
or evolved substances are not retained by the poles ; and this is 
no small difficulty in those theories which refer the decompo- 
sing effect directly to the attractive power of the poles. If, in 
accordance with the usual theory, a piece of platina be supposed 
to have sufficient power to attract a particle of hydrogen from 
the particle of oxygen with which it was the instant before com- 
bined, there seems no sufficient reason, nor any fact, except 
those to be explained, which show why it should not, according 
to analogy with all ordinary attractive forces, as those of gravi- 
tation, magnetism, cohesion, chemical affinity, &e., retain that 
particle which it had just before taken from a distance and from 
previous combination. Yet it does not do so, but allows it to 
escape freely. Nor docs this depend upon its assuming the 
gaseous state, for acids and alkalies, &o., arc left equally at 
liberty to diffuse themselves through the fluid surrounding the 
pole, and show no particular tendency to combine with or 
adhere to the latter. And though there are plenty of cases 
where combination with the pole does take place, they do not at 
all explain the instances of non-combination, and do not there- 
fore in their particular action reveal the general principle of 
decomposition. - 

537* Jlut in the theory that I have just given, the effect ap- 
pears to be a natural consequence of the action : the evolved 
substances are expelled from the decomposing mass (518. 519.), 
not drawn out by an attraction which ceases to act on one par- 
ticle without any assignable reason, while it continues to act on 
another Of the same kind : and whether the poles be metal, 
water, or air, still the substances are evolved, and are sometimes 
•set free, whilst at others they unite to the matter of the poles. 



136 


Transference of combined bodies. [Series V. 

according to the chemical nature of the latter, i . e. their chemical 
relation to those particles which are leavingithe substance under 
operation. 

538. The theory accounts for the transfer of elements in a 
manner which seems to me at present to leave nothing unex- 
plained ; and it was, indeed, the phenomena of transfer in the 
numerous cases of decomposition of bodies rendered fluid by 
heat (380. 402.), which, in conjunction with the experiments in 
air, led to its construction. Such cases as the former where 
binary compounds of easy decomposability are acted upon, are 
perhaps the best to illustrate the theory. 

539. Chloride of lead, for instance, fused in a bent tube (400.), 
and decomposed by platina wires, evolves lead, passing to what 
is usually called the negative pole, and chlorine, which being 
evolved at the positive pole, is in part set free, and in part com- 
bines with the platina. The chloride of platina formed, being 
soluble in the chloride of lead, is subject to decomposition, and 
the platina itself is gradually transferred across the decomposing 
matter, and found with the lead at the negative pole. 

540. Iodide of lead evolves abundance of lead at the negative 
pole, and abundance of iodine at the positive pole. 

541. Chloride of silver furnishes a beautiful instance, espe- 
cially when decomposed by silver wire poles. Upon fusing a 
portion of it on a piece of glass, and bringing the poles into 
contact with it, there is abundance of silver evolved at the nega- 
tive pole, and an equal abundance absorbed at the positive pole, 
for no chlorine is set free : and by careful management, the 
negative wire may be withdrawn from the fused globule as the 
silver is reduced there, the latter serving as the continuation of 
the pole, until a wire or thread of revived silver, five or six 
inches in length, is produced ; at the same time the silver at 
the positive pole is as rapidly dissolved by the chlorine, which 
seizes upon it, so that the wire has to be continually advanced 
as it is melted away. The whole experiment includes the action 
of only two elements, silver and chlorine, and illustrates in a 
beautiful manner their progress in opposite directions, parallel 
to the electric current, which is for the time giving a uniform 
general direction to their mutual affinities (524.). 

542. According to my theory, an element or a substance not 
decomposable under the circumstances of the experiment, (as, 
for instance, a dilute acid or alkali,) should not be. transferred 



157 


June 1833.] Uncombined bodies not transferable . 

or pass from pole to pole, unless it be in chemical relation to 
some other element or substance tending to pass in the opposite 
direction, for the effefct is considered as essentially due to the 
mutual relation of such particles. But the theories attributing 
the determination of the elements to the attractions and repul- 
sions of the poles require no such condition, i. e. there is no 
reason apparent why the attraction of the positive pole, and the 
repulsion of ‘the negative pole, upon a particle of free acid, 
placed fn water between them, should not (with equal currents 
of electricity) be as strong as if that particle were previously 
combined with alkali ; but, on the contrary, as they have not a 
powerful chemical affinity to overcome, there is every reason to 
suppose they would be stronger, and would sooner bring the 
acid to rest at the positWe pole*. Yet such is not the case, as 
has been shown by the experiments on free and combined acid 
(526.528.). 

543. Neither does M. de la Rivers theory, as I understand it, 
require that the particles should be in combination : it does not 
even admit, where there are two sets of particles capable of 
combining with and passing by each other, that they do combine, 
but supposes that they travel as separate compounds of matter 
and electricity. Yet in fact the free substance cannot travel, 
the combined one can. 

544. It is very difficult to find cases amongst solutions or 
fluids which shall illustrate this point, because of the difficulty 
of finding two fluids which shall conduct, shall not mingle, and 
in which an element evolved from one shall not find a combi - 
nable element in the other. Solutions of acids or alkalies will not 
answer, because they exist by virtue of an attraction ; and in- 
creasing the solubility of a body in one direction, and diminish- 
ing it in the opposite, is just as good a reason for transfer, as 
modifying the affinity between the acids and alkalies them- 
selves f, Nevertheless the case of sulphate of magnesia is in 
point (494. 495.), and shows that one element or principle only 
has no power of transference or of passing towards either pole. 

545. Many of the metals, however, in their solid state, offer 
very fair instances of the kind required. Thus, if a plate of 
platina be used as the positive pole in a solution of sulphuric 

* Even Sir Humphry Davy considered the attraction of the pole as being 
communicated: from one particle to another of the same kind (483). 

t See the note to 675.— Dec. 1838. 



158 Theory of transference of bodies. [Series V. 

acid, oxygen will pass towards it, and so will acid ; but these 
are not substances having such chemical relation to the platina 
as* even under the favourable eonditiorf superinduced by the 
current (518. 524.), to combine with it; the platina therefore 
remains where it was first placed, and has no tendency to pass 
towards the negative pole. But if a plate of iron, zinc or cop- 
per, be substituted for the platina, then’ the oxygen and acid 
can combine with these, and the metal immediately begins to 
travel (as an oxide) to the opposite pole, and is finally deposited 
there. Or if, retaining the platina pole, a fused chloride, as 
of lead, zinc, silver, &c., be substituted for the sulphuric acid, 
then, as the platina finds an element it can combine with, it 
enters into union, acts as other elements do in cases of voltaic 
decomposition, is rapidly transferred across the melted matter, 
and expelled at the negative pole. 

546. I can see but little reason in the theories referring the 
electro-chemical decomposition to the attractions and repul- 
sions of the poles, and I can perceive none in M. de la Rive's 
theory, why the metal of the positive pole should not be trans- 
ferred across the intervening conductor, and deposited at the 
negative pole, even when it cannot act chemically upon the 
element of the fluid surrounding it. It cannot be referred to 
the attraction of cohesion preventing such an effect ; for if the 
pole be made of the lightest spongy platina, the effect is the 
same. Or if gold precipitated by sulphate of iron be diffused 
through the solution, still accumulation of it at the negative 
pole will not take place ; and yet in it the attraction of cohesion 
is almost' perfectly overcome, the particles are so small as to 
remain for hours in suspension, and are perfectly free to move 
by the slightest impulse towards either pole ; and if in relation 
by chemical affinity to any substance present, are powerfully 
determined to the negative pole*. 

* In making this experiment, care must be taken that no substance be pre- 
sent that can act chemically on the gold. Although I used the metal very 
carefully washed, and diffused through dilute sulphuric acid, yet in the first 
instance I obtained gold at the negative pole, and the effect was repeated 
when the platina poles were changed. But on examining the clear liquor in 
the cell, after subsidence of the metallic gold, I found a little of that metal in 
solution, and a little chlorine was also present. I therefore well washed the 
gold which had thus been subjected to voltaic action, diffused it through other 
pure dilute sulphuric acid, and then found, that on subjecting it to the action 
of the pile, not the slightest tendency to the negative pole could be perceived. 



159 


June 1833.] Uncombined bodies not transferable. 

547. In support of these arguments, it may be observed, that 
as yet no determination of a substance to a pole, or tendency 
to obey the electric current, has been observed (that I am aware 
of,) in cases of mere mixture ; i.e. a substance diffused through 
a fluid, but having no sensible chemical affinity with it, or with 
substances that may be evolved from it during the action, does 
not in any case seeni to be affected by the electric current. 
Pulverised charcoal was diffused through dilute sulphuric acid, 
and subjected with the solution to the action of a voltaic bat- 
tery, terminated by platina poles ; but not the slightest ten- 
dency of the charcoal to the negative pole could be observed. 
Sublimed sulphur was diffused through similar acid, and sub- 
mitted to the same action, a silver plate being used as the 
negative pole ; but the Sulphur had no tendency to pass to that 
pole, the silver was not tarnished, nor did any sulphuretted 
hydrogen appear. The case of magnesia and water (195. 533.), 
with those of comminuted metals in certain solutions (5 10.), 
are also of this kind ; and, in fact, substances which have the 
instant before been powerfully determined towards the pole, as 
magnesia from sulphate of magnesia, become entirely indifferent 
to it the moment they assume their independent state, and pass 
away, diffusing themselves through the surrounding fluid. 

548. There are, it is true, many instances of insoluble bodies 
being acted upon, as glass, sulphate of baryta, marble, slate, 
basalt, &c., but they form no exception ; for the substances 
they give up are in direct and strong relation as to chemical 
affinity with those which they find in the surrounding solution, 
so that these decompositions enter into the class of ordinary 
effects. 


549. It may be expressed as a general consequence, that the 
more directly bodies are opposed to each other in chemical 
affinity, the more ready is their separation from each other in 
cases of ©leeiro-chemical decomposition, i . e.- provided other 
circumstances, as insolubility, deficient conducting power, pro- 
portions, &e., do not interfere. This is well known to be the 
case with water and saline solutions ; and I have found it to be 
equally true with dry chlorides, iodides, salts, &c., rendered 
subject to electro-chemical decomposition by fusion (402.) . So 
that ih applying the voltaic battery for the purpose* of decom- 



160 Transfer of bodies during decomposition . [Series V* 

posing bodies not yet resolved into forms of matter simpler than 
their own, it must be remembered, that success may depend 
not upon the weakness, or failure upon the strength, of the 
affinity by which the elements sought for are held together, 
but contrariwise; and then modes of application may be de- 
vised, by which, in association with ordinary chemical powers, 
and the assistance of fusion (394. 417.), we may be able to 
penetrate much further than at present into the constitution of 
our chemical elements. 

550. Some of the most beautiful and surprising cases of 
electro-chemical decomposition and transfer which Sir Hum- 
phry Davy described in his celebrated paper*, were those in 
which acids were passed hrough alkalies, and alkalies or earths 
through acids f ; and the way in whitfh substances having the 
most powerful attractions for each other were thus prevented 
from combining, or, as it is said, had their natural affinity 
destroyed or suspended throughout the whole of the circuit, 
excited the utmost astonishment. But if I be right in the view 
I have taken of the effects, it will appear, that that which made 
the wonder , is in fact the essential condition of transfer and 
decomposition, and that the more alkali there is in the course 
of an acid, the more will the transfer of that acid be facilitated 
from pole to pole ; and perhaps a better illustration of the 
difference between the theory I have ventured, and those pre- 
viously existing, cannot be offered than the views they respec- 
tively give of such facts as these. 

551. The instances in which sulphuric acid could not be 
passed through baryta, or baryta through sulphuric acid J, 
because of the precipitation of sulphate of baryta, enter within 
the pale of the law already described (380. 412.), by which 
liquidity is so generally required for conduction and decompo- 
sition. In assuming the solid state of sulphate of baryta, these 
bodies became virtually non-conductors to electricity of so low 
a tension as that of the voltaic battery, and the power of the 
latter over them was almost infinitely diminished. 

552. The theory I have advanced accords in a most satis- 
factory manner with the fact of an element or substance find- 
ing its place of rest, or rather of evolution, sometimes at one 

* Philosophical Transactions, 1807, p. 1* t Ibid. p. 24, &c. 

X Ibid. p. 25, &c. 



161 


JtfNE 1833.] Bodies which pass to either pole . 

pole and sometimes at the other. Sulphur illustrates this 
effect very well*. When sulphuric acid is decomposed by the 
pile, sulphur is evolved at 'the negative pole; but when sul- 
phuret of silver is decomposed in a similar way (436.), then the 
sulphur appears at the positive pole ; and if a hot platina pole 
be used so as to vaporize the sulphur evolved in the latter case, 
then the relation of that pole to the sulphur is exactly the same 
as the relation- of the same pole to oxygen upon its immersion 
in water* In both cases the element evolved is liberated at the 
pole, but not retained by it; but by virtue of its elastic, un- 
combinable, and immiscible condition passes away into the sur- 
rounding medium. The sulphur is evidently determined in 
these opposite directions by its opposite chemical relations to 
oxygen and silver ; and ijt is to such relations generally that I 
have referred all electro-chemical phenomena. Where they 
do not exist, no electro-chemical action can take place. Where 
they are strongest, it is most powerful ; where they arc re- 
versed, the direction of transfer of the substance is reversed 
with them. 

553. Water may be considered as one of those substances 
which can be made to pass to either pole. When the poles 
are immersed in dilute sulphuric acid (527.), acid passes to- 
wards the positive pole, and water towards the negative pole; but 
when they arc immersed in dilute alkali, the alkali passes towards 
the negative pole, and water towards the positive pole. 

554. Nitrogen is another substance which is considered as 
determinable to either pole ; but in consequence of the nume- 
rous compounds which it forms, some of which pass to one 
pole, and some to the other, I have not always found it easy to 
determine the true circumstances of its appearance. A pure 
strong solution of ammonia is so bad a conductor of electricity 
that it is scarcely more decomposable than pure water ; but if 
sulphate of ammonia be dissolved in it, then decomposition 
takes place very well ; nitrogen almost pure, and in some cases 
quite, is evolved at the positive pole, and hydrogen at the nega- 
tive pole. 

* At 681 and 757 of Series VII. will be found corrections of the statement 
here made respecting sulphur and sulphuric acid. At present there is no well- 
ascertained fact which proves that the same body can go directly to either of 
the two poles at pleasure. — Dec. 1838. 

M 



162 Electro -chemical decomposition . [Series V. 

555. On the other hand, if a strong solution of nitrate of 
ammonia be decomposed, oxygen appears at the positive pole, 
and hydrogen, with sometimes nitrogen, at the negative pole. 
If fused nitrate of ammonia be employed, hydrogen appears at 
the negative pole, mingled with a little nitrogen. Strong nitric 
acid yields plenty of oxygen at the positive pole, but no gas 
(only nitrous acid,) at the negative pole. Weak nitric acid 
yields the oxygen and hydrogen of the water present, o the acid 
apparently remaining unchanged. Strong nitric acid with nitrate 
of ammonia dissolved in it, yields a gas at the negative pole, of 
which the greater part is hydrogen, but apparently a little 
nitrogen is present. I believe that in some of these cases a 
little nitrogen appeared at the negative pole. I suspect, how- 
ever, that in all these, and in all former cases, the appearance of 
the nitrogen at the positive or negative pole is entirely a 
secondary effect, and not an immediate consequence of the de- 
composing power of the electric current*. 

556. A few observations on what are called the poles of the 
voltaic battery now seem necessary. The poles are merely the 
surfaces or doors by which the electricity enters into or passes 
out of the substance suffering decomposition. They limit the 
extent of that substance in the course of the electric current, 
being its terminations in that direction : hence the elements 
evolved pass so far and no further. 

557. Metals make admirable poles, in consequence of their 
high conducting power, their immiscibilility with the substances 
generally acted upon, their solid form, and the opportunity 
afforded of selecting such as are not chemically acted upon by 
ordinary substances. 

558. Water makes a pole of difficult application, except in a 
few cases (494.), because of its small conducting power, its 
miscibility with most of the substances acted upon, and its 
general relation to them in respect to chemical affinity. It 
consists of elements, which in their electrical and chemical rela- 
tions are directly and powerfully opposed, yet combining to 
produce a body more neutral in its character than any other. 
So that there are but few substances which do not come into 
relation, by chemical affinity, with water or one of its elements ; 
* Refer for proof of the truth of this supposition to 748, 762, &c. — Dec, 1838. 



163 


June 1883.] Character and nature of the poles. 

and therefore either the water or its elements are transferred 
and assist in transferring the infinite variety of bodies which, 
in association with it, can be placed in the course of the elec- 
tric current. Hence the reason why it so rarely happens that 
the evolved^ substances rest at the first surface of the water, 
and why it therefore does not exhibit the ordinary action of a 
pole. 

559. Air, however, and some gases are free from the latter 
objection, and may be used as poles in many cases (461, &c .) ; 
but, in consequence of the extremely low degree of conducting 
power belonging to them, they cannot be employed, with the 
voltaic apparatus. This limits their use; for the voltaic appa- 4 
ratus is the only one as jet discovered which supplies sufficient 
quantity of electricity (371. 376.) to effect electro-chemical de- 
composition with facility. 

560. When the poles are liable to the chemical action of the 
substances evolved, either simply in consequence of their natural 
relation to them, or of that relation aided by the influence of 
the current (518.), then they suffer corrosion, and the parts 
dissolved are subject to transference, in the same manner as the 
particles of the body originally under decomposition. An 
immense series of phenomena of this kind might be quoted in 
support of the view I have taken of the cause of electro-chemical 
decomposition, and the transfer and evolution of the elements. 
Thus platina being made the positive and negative poles in a 
solution of sulphate of soda, has no affinity or attraction for the 
oxygen, hydrogen, acid, or alkali evolved, and refuses to com- 
bine with or retain them. Zinc can combine with the oxygen 
and acid ; at the positive pole it docs combine, and immediately 
begins to travel as oxide towards the negative pole. Charcoal, 
which cannot combine with the metals, if made the negative 
pole in a metallic solution, refuses to unite to the bodies which 
are ejected from the solution upon its surface; but if made the 
positive pole in a dilute solution of sulphuric acid, it is capable 
of combining with the oxygen evolved there, and consequently 
unites with it, producing both carbonic acid and carbonic oxide 
in abundance, 

561. A great advantage is frequently supplied, by the oppor- 
tunity afforded amongst the metals of selecting a substance for 
the pole, which shall or shall not be acted upon by the elements 

m 2 



164 


Electro-chemical decomposition. 


[Series V. 


to be evolved. The consequent use of platina is notorious. In 
the decomposition of sulphuret of silver tnd other sulphurets, a 
positive silver pole is superior to a platina one, because in the 
former case the sulphur evolved there combines with the silver, 
and the decomposition of the original sulphuret is rendered 
evident ; whereas in the latter case it is dissipated, and the 
assurance of its separation at the pole not easily -obtained. 

562. The effects which take place when a succession of con- 
ducting decomposable and undecomposable substances are 
placed in the electric circuit, as, for instance, of wires and 
solutions, or of air and solutions (465. 469.), are explained in 
the simplest possible manner by the theoretical view I have 
given. In consequence of the reaction of the constituents of 
each portion of decomposable matter, affected as they are by 
the supervention of the electric current (524.), portions of the 
proximate or ultimate elements proceed in the direction of the 
current as far as they find matter of a contrary kind capable of 
effecting their transfer, and being equally affected by them ; and 
where they cease to find such matter, they are evolved in their 
free state, i. e. upon the surfaces of metal or air bounding the 
extent of decomposable matter in the direction of the current. 

563. Having thus given my theory of the mode in which 
electro-chemical decomposition is effected, I will refrain for the 
present from entering upon the numerous general considerations 
which it suggests, wishing first to submit it to the test of publi- 
cation and discussion. 

Royal Institution , 

June 1833. 



165 


SIXTH SERIES. 

§ 12. 0% the power of Metals arid other Solids to induce the 
Combination of Gaseous Bodies . 

Received November 80, 1838, — Read January 11, 1884. 

564. The conclusion at which I have arrived in the present com- 
munication may seem to render the whole of it unfit to form part 
of a series of researches* in electricity ; since, remarkable as 
the phenomena are, the power which produces them is not to 
be considered as of an electric origin, otherwise than as all at- 
traction of particles may have this subtile agent for their com- 
mon cause. But as the effects investigated arose out of elec- 
trical researches, as they are directly connected with other 
effects which arc of an electric nature, and must of necessity 
be understood and guarded against in a very extensive series 
of electro- chemical decompositions (707.), I have felt myself 
fully justified in describing them in this place, 

365. Believing that I had proved (by experiments hereafter 
to be described (705.), ) the 'constant and definite chemical 
action of a certain quantity of electricity, whatever its intensity 
might be, or however the circumstances of its tranmission 
through either the body under decomposition or the more per- 
fect conductors were varied, I endeavoured upon that result to 
construct a new measuring instrument, which from its use 
might be called, at least provisionally,, a Volt a- electrometer 
(739.)* 

566. During the course of the experiments made to render 
the ir^trument efficient, I was occasionally surprised at obser- 
ving a deficiency of the gases resulting from the decomposi- 
tions of water, and at last an * actual disappearance of poi'tions 
which had been evolved, collected, and measured. The cir- 
cumstances of the disappearance were these. A glass tube, 
about twelve inches in length and f ths of an inch in diameter, 
had two platina poles fixed into its uppei’, hermetically sealed, 

* Or Voltameter. —Dee. 1888. 



166 Disappearance of gases around the poles. [Series VI. 

extremity : the poles, where they passed through the glass, 
were o£ wire ; but terminated below in plates, which were 
soldered to the wires with gold (Plate V. fig. 56.). The tube 
was filled with dilute sulphuric acid, and inverted in a cup of 
the same fluid ; a voltaic battery was connected with the two 
wires, and sufficient oxygen and hydrogen evolved to occupy 
^ths of the tube, or by the graduation, 116 parts. Oja separa- 
ting the tube from the voltaic battery the volume of gas imme- 
diately began to diminish, and in about five hours only 13£ 
parts remained, and these ultimately disappeared. 

567. It was found by various experiments, that this effect 
was not due to the escape or solution of the gas, nor to recom- 
bination of the oxygen or hydrogen in consequence of any pe- 
culiar condition they might be supposed to possess under the 
circumstances ; but to be occasioned by the action of one or 
both of the poles within the tube upon the gas around them. 
On disuniting the poles from the pile after they had acted 
upon dilute sulphuric acid, and introducing them into separate 
tubes containing mixed oxygen and hydrogen, it was found 
that the positive pole effected the union of the gases, but the 
negative pole apparently not (588.). It was ascertained also 
that no action of a sensible kind took place between the posi- 
tive pole with oxygen or hydrogen alone. 

568. These experiments reduced the phenomena to the con- 
sequence of a power possessed by the platina, after it had been 
the positive pole of a voltaic pile, of causing the combination 
of oxygen and hydrogen at common, or even at low, tempera- 
tures. This effect is, as far as I am aware, altogether new, 
and was immediately followed out to ascertain whether it was 
really of an electric nature, and how far it would interfere with 
the determination of the quantities evolved in the cases of elec- 

. tro-chemical decomposition required in the fourteenth section 
of these Researches. 

.569. Several platina plates were prepared (fig. 57.). They 
were nearly half an inch wide, and two inches and a half long : 
some were ^J^dth of an inch, others not more than ^J^dth, 
whilst some were as much as ^th of an inch in thickness. 
Each had a piece of platina wire, about seven inches long, sol- 
dered to it by pure gold. Then a number of glass tubes Were 
prepared : they were about nine or ten inches in length, fths 



167 


Nov. 18&3.]s Circumstances of the peculiar action . 

of an inch in internal diameter, were sealed hermetically at one 
extremity, and were graduated. Into these tubes was put a 
mixture of two volumes of hydrogen and one of oxygen, at the 
water pneumatic trough, and when one of the plates described 
had been connected with the positive or negative pole of the 
voltaic battery for a given time, or had been otherwise pre- 
pared, it was introduced through the water into the gas within 
the tub^ ; the whole set aside in a test-glass (fig. 58.), and left 
for a longer or shorter period, that the action might be ob- 
served. 

570. The following result may be given as an illustration of 
the phenomenon to be investigated. Diluted sulphuric acid, 
of the specific gravity 1*336, was put into a glass jar, in which 
was placed also a larg^ platina plate, connected with the nega- 
tive end of a voltaic battery of forty pairs of four-inch plates, 
with double coppers, and moderately charged. One of the 
plates above described (569.) was then connected with the 
positive extremity, and immersed in the same jar of acid for 
five minutes, after which it was separated from the battery, 
washed in distilled water and introduced through the water 
of the pneumatic trough into a tube containing the mixture of 
oxygen and hydrogen (509.). The volume of gases immedi- 
ately began to lessen, the diminution proceeding more and 
more rapidly until about |ths of the mixture had disappeared. 
The upper end of the tube became quite warm, the plate itself 
so hot that the water boiled as it rose over it; and in less 
than a minute a cubical inch and a half of the gases were gone, 
having been combined by the power of the platina, and con- 
verted into water. 

* 571. This extraordinary influence acquired by the platina at 
the positive pole of the pile, is exerted far more readily and 
effectively on oxygen and hydrogen than on any other mixture 
of gases that I have tried. One volume of nitrous gas was 
mixed with a volume of hydrogen, and introduced into a tube 
with a plate which had been made positive in the dilute sulphu- 
ric acid for four minutes (570.). There was no sensible action 
in an hour; being left for thirty-six hours, there was a diminution 
of about one eighth of the whole volume. Action had taken 
place, but it had been very feeble. 

57J& A mixture of two volumes of nitrous oxide with one 



168 Combination of oxygen and hydrogen by plate*. [Series VI. 

volume of hydrogen was put with a plate similarly prepared 
into a tube (569. 570.) . This also showed no action immedi- 
ately ; but in thirty-six hours nearly a fourth of the whole had 
disappeared, i.e. about half of a cubic inch. By comparison 
with another tube containing the same mixture without a plate, 
it appeared that a part of the diminution was due to solution, 
and the other part to the power of the platina ; but the action 
had been very slow and feeble. 

573. A mixture of one volume olefiant gas and three volumes 
oxygen was not affected by such a platina plate, even though 
left together for several days (640. 641.). 

574. A mixture of two volumes carbonic oxide and one vo- 
lume oxygen was also unaffected by the prepared platina plate 
in several days (645. &c\). 

575. A mixture of equal volumes of chlorine and hydrogen was 
used in several experiments, with plates prepared in a similar 
manner (570.) . Diminution of bulk soon took place ; but when 
after thirty- six hours the experiments were examined, it was 
found that nearly all the chlorine had disappeared, having been 
absorbed, principally by the water, and that the original volume 
of hydrogen remained unchanged. No combination of the 
gases, therefore, had here taken place. 

576. Reverting to the action of the prepared plates on 
mixtures of oxygen and hydrogen (570.), I found that the 
power, though gradually diminishing in all cases, could still be 
retained for a period, varying in its length with circumstances. 
When tubes containing plates (569.) were supplied with fresh 
portions of mixed oxygen and hydrogen as the previous portions 
were condensed, the action was found to continue for above 
thirty hours, and in some cases slow combination could be ob- 
served even after eighty hours ; but the continuance of the 
action greatly depended upon the purity of the gases used 
(638.). 

577. Some plates (569.) were made positive for four minutes 
in dilute sulphuric acid of specific gravity 1*336 : they were 
rinsed in distilled water, after which two were put into a small 
bottle and closed up, whilst others were left exposed to the air. 
The plates preserved in the limited portion of *air were found 
to retain their power after eight days, but those exposed to the, 
atmosphere had lost their force almost entirely in twelve hours 



Nov. 1833 ,] Preparation of the platina plates . 169 

and in some situations, where currents existed, in a much 
shorter time. 

578 . plates were made positive for five minutes in sulphuric 
acid, specific gravity 1*336. One of these was retained in 
similar acid for eight minutes after separation from the battery ; 
it then acted on mixed oxygen and hydrogen with apparently 
undiminished vigour. Others were left in similar acid for forty 
hours, $nd some even for eight days, after the electrization, 
and then acted as well in combining oxygen and hydrogen gas 
as those which were used immediately after electrization. 

579. The effect of a solution of caustic potassa in .preserving 
the platina plates was tried in a similar manner. After being 
retained in such a solution for forty hours, they acted exceed- 
ingly well on oxygen and hydrogen, and one caused such rapid 
condensation of the gases, that the plate became mtfbh heated, 
and I expected the temperature would have risen to ignition. 

580. When similarly prepared plates (569.) had been put into 
distilled water for forty hours, and then introduced into mixed 
oxygen and hydrogen, they were found to act but very slowly 
and feebly as compared with those which had been preserved 
in acid or alkali. When, however, the quantity of water was 
but small, the power was very little impaired after three or four 
days. As the water had been retained in a wooden vessel, 
portions of it were redistilled # in glass, and this was found to 
preserve prepared plates for a great length of time. Prepared 
plates were put into tubes with this water and closed up ; some 
of them, taken out at the end of twenty-four days, were found 
very active on mixed oxygen and hydrogen ; others, which were 
left in the water for fifty-three days, were still found to cause 
the combination of the gases. The tubes had been closed only 
by corks. 

581. The act of combination always seemed to diminish, or 
apparently" exhaust, the power of the platina plate. It is true, 
that in most, if not all instances, the combination of the gases, 
at first insensible, gradually increased in rapidity, and some- 
times reached to explosion ; but when the latter did not happen, 
the rapidity of combination diminished ; and although fresh 
portions' of gas were introduced into the tubes, the combination 
wont on more and more slowly, and at last ceased altogether. The 
first effect of an increase in the rapidity of combination dependent 



170 Power of the plates affected, [Series VI. 

in part upon the water flowing off from the platina plate, and 
allowing a better contact with the gas, and in part upon the 
heat evolved during the progress of the combination (630.). 
But notwithstanding the effect of these causes, diminution, and 
at last cessation of the powfer, always occurred. It must not, 
however, be unnoticed, that the purer the gases subjected to 
the action of the plate, the longer was its combining power re- 
tained. With the mixture evolved at the poles of tlxQt voltaic 
pile, in pure dilute sulphuric acid, it continued longest ; and 
with oxygen and hydrogen, of perfect purity, it probably would 
not be diminished at all. 

582. Different modes of treatment applied to the platina plate, 
after it had ceased to be the positive pole of the pile, affected 
its power very curiously. A plate which had been a positive 
pole in diluted sulphuric acid of specific gravity 1336 for four 
or five minutes, if rinsed in water and put into mixed oxygen 
and hydrogen, would act very well, and condense perhaps one 
cubic inch and a half of gas in six or seven minutes ; but if that 
same plate, instead of being merely rinsed, had been left in 
distilled water for twelve or fifteen minutes, or more, it would 
rarely fail, when put into the oxygen and hydrogen, of becoming, 
in the course of a minute or two, ignited, and would generally 
explode the gases. Occasionally the time occupied in bringing 
on the action extended to eight ctr nine minutes, and sometimes 
even to forty minutes, and yet ignition and explosion would 
result. This effect is due to the removal of a portion of acid 
which otherwise adheres firmly to the plate *. 

583. Occasionally the platina plates (569.), after being made 
the positive pole of the battery, were washed, wiped with filter- 
ing-paper or a cloth, and washed and wiped again. Being then 
introduced into mixed oxygen and hydrogen, they acted ap- 
parently as if they had been unaffected by the treatment. Some- 
times the tubes containing the gas were opened in the air for 
an instant, and the plates put in dry ; but no sensible difference 
in action was perceived, except that it commenced sooner. 

584. The power of heat in altering the action of the prepared 
platina plates was also tried (595.). Plates which had been 
rendered positive in dilute sulphuric acid for four minutes 
^yere well washed in water, and heated to redness in the flame 

* In proof that this is the case, refer to 1038. — Dec. 1838. 



171 


Nov, 1833.] Action of heat, acid, alkali, §c. 

of a spirit-lamp : after this they acted very well on mixed oxygen 
and hydrogen. Others, which had been heated more power- 
fully by the blowpipe, acted afterwards on the gases, though 
not so powerfully as the former. Hence it appears that heat 
does not take away the power acquired by the platina at the 
positive pole of the pile : the occasional diminution of force 
seeme^ always referable to other causes than the mere heat. 
If, for instance, the plate had not been avcII washed from the 
acid, or if the flame used was carbonaceous, or was that of an 
alcohol lamp trimmed with spirit containing a little acid, or 
having a wick on which salt, or other extraneous matter, had 
been placed, then the power of the plate was quickly and greatly 
diminished (634. 636.)*. 

585. This remarkable property was conferred upon platina 
when it was made the positive pole in sulphuric acid of specific 
gravity 1*336, or when it was considerably weaker, or when 
stronger, even up to the strength of oil of vitriol. Strong and 
dilute nitric acid, dilute acetic acid, solutions of tartaric, citric, 
and oxalic acids, were used with equal success. When muri- 
atic acid was used, the plates acquired the power of condensing 
the oxygen and hydrogen, but in a much inferior degree. 

586. Plates which were made positive in solution of caustic 
potassa did not show any sensible action upon the mixed oxygen 
and hydrogen. Other plates made positive in solutions of 
carbonates of potassa and soda exhibited the action, but only 
in a feeble degree. 

587. When a neutral solution of sulphate of soda, or of nitre, 
or of chlorate of potassa, or of phosphate of potassa, or acetate 
of potassa, or sulphate of copper, was us.ed, the plates, rendered 
positive in them for four minutes, and then washed in water, 
acted very readily and powerfully on the mixed oxygen and 
hydrogen. 

588. It Jbecame a very important point, in reference to the 
cause of this action of the . platina, to determine whether the 
positive pole only could confer it (567.), or whether, notwith- 
standing the numerous contrary cases, the negative pole might 
not have the power' when such circumstances as could interfere 
with or prevent the action were avoided. Three .plates were 
therefor rendered negative, for four minutes in diluted sul- 
phuric acid of specific gravity 1*336, washed in distilled water ; 



1?2 Clean platina induces combination. [Series YI. 

and put into mixed oxygen and hydrogen. All of them acted , 
though not so strongly as they would h&ve done if they had 
been rendered positive. Each combined about a cubical inch 
and a quarter of the gases in twenty-five minutes. On every 
repetition of the experiment the same result was obtained ; and 
when the plates were retained in distilled water for ten or 
twelve minutes, before being introduced into the gas (58^,), the 
action was very much quickened. 

589. But when there was any metallic or other substance 
present in the acid, which could be precipitated on the negative 
plate, then that plate ceased to act upon the mixed oxygen and 
hydrogen. 

590. These experiments led to the expectation that the power 
of causing oxygen and hydrogen to combine, which could be 
conferred upon any piece of platina by making it the positive 
pole of a voltaic pile, was not essentially dependent upon the 
action of the pile, or upon any structure or arrangement of 
parts it might receive whilst in association with it, but belonged 
to the platina at all times , and was always effective when the 
surface was perfectly clean . And though, when made the 
positive pole of the pile in acids, the circumstances might well 
be considered as those which would cleanse the surface of the 
platina in the most effectual manner, it did not seem impossible 
that ordinary operations should' produce the same result, 
although in a less eminent degree. 

591. Accordingly, a platina plate (569.) was cleaned by being 
rubbed with a cork, a little water, and some coal- fire ashes upon 
a glass plate : being washed, it was put into mixed oxygen and 
hydrogen, and was found to aGt at first slowly, and then more 
rapidly. In an hour, a cubical inch and a half had disappeared. 

592. Other plates were cleaned with ordinary sand-paper 
and water ; others with chalk and water ; others with emery 
and water ; others, again, with black oxide of manganese and 
water ; and others with a piece of charcoal and water. All of 
these acted in tubes of oxygen and hydrogen, causing combina- 
tion of the gases. The action was by no means so powerful as 
that produced by plates having been in communication with the 
battery ; but from one to two cubical inches of the gases dis- 
appeared, in periods extending from twenty-five to eighty or 
ninety minutes. 



173 


Nov. 1833.] Effect of heat on the platina. 

593. Upon cleaning the plates with a cork, ground emery, 
and dilute sulphuric acid, they were found to act still better. 
In ordOr to simplify ftie conditions, the cork was dismissed, and 
a piece of platina foil used instead ; still the effect took place. 
Then the acid was dismissed, and a solution of potassa used, 
but the effect occurred as before. 

594. These results are abundantly sufficient to show that the 
mere n^chanical cleansing of the surface of the platina is suf- 
ficient to enable it to exert its combining power over oxygen 
and hydrogen at common temperatures. 

595. I now tried the effect of heat in conferring this property 
upon platina (584.) . Plates which had no action on the mixture 
of oxygen and hydrogen were heated by the flame of a freshly 
trimmed spirit-lamp, urged by a mouth blowpipe, and when 
cold were put into tubes of the mixed gases : they acted slowly 
at first, but after two or three hours condensed nearly all the 
gases. 

596. A plate of platina, which was about one inch wide and 
two and three quarters in length, and which had not been used 
in any of the preceding experiments, was curved a little so as 
to enter a tube, and left in a mixture of oxygen and hydrogen 
for thirteen hours : not the slightest action or combination of 
the gases occurred. It was withdrawn at the pneumatic trough 
from the gas through the water, heated red hot by the spirit- 
lamp and blowpipe, and then returned when cold into the same 
portion of gas. In the course of a few minutes diminution of 
the gases could be observed, and in forty-five minutes about one 
cubical inch and a quarter had disappeared. In many other 
experiments platina plates when heated were found to acquire 
the power of combining oxygen and hydrogen. 

597. But it happened not unfrequently that plates, after being 
heated, showed no power of combining oxygen and hydrogen 
gases, though left undisturbed in them for two hours. Some- 
times also it would happen that a plate which, having been 
heated to dull redness, acted feebly, upon being heated to white- 
ness ceased to act ; and at other times a plate which, having 
been slightly heated, did not act, was rendered active by a more 
powerful ignition. 

. 598. Though thus uncertain in its action, and though often 

diminishing the power given to the plates at the positive pole 



174s Platina cleansed by acids and alkalies. [Series VI.' 

of the pile (581.), still it is evident that heat can render platina 
active, which before was inert (595.) The cause of its occa- 
sional failure appears to be due to the sufface of the metal be- 
coming soiled, either from something previously adhering to it, 
which is made to adhere more closely by the action of the heht, 
or from matter communicated from the flame of the lamp, or 
from the air itself. It often happens that a polished plate of 
platina, when heated by the spirit-lamp and a blowpipe, be- 
comes dulled and clouded on its surface by something either 
formed or deposited there ; and this, and much less than this, 
is sufficient to prevent it from exhibiting the curious power 
now under consideration (634. 636.). Platina also has been 
said to combine with carbon ; and it is not at all unlikely that 
in processes of heating, where carbon c or its compounds are 
present, a film of such a compound may be thus formed, and 
thus prevent the exhibition of the properties belonging to pure 
platina*. 

599. The action of alkalies and acids in giving platina this 
property was now experimentally examined. Platina plates 
(569.) having no action on mixed oxygen and hydrogen, being 
boiled in a solution of caustic potassa, washed, and then put 
into the gases, were found occasionally to act pretty well, but 
at other times to fail. In the latter case I concluded that the 
impurity upon the surface of the platina was of a nature not to 
be removed by the mere solvent action of the alkali, for when 
the plates were rubbed with a little emery, and the same solu- 
tion of alkali (592.), they became active. 

600. The action of acids was far more constant and satis- 
factory. A platina plate was boiled in dilute nitric acid : being 
washed and put into mixed oxygen and hydrogen gases, it 
acted well. Other plates were boiled in strong nitric acid for 
periods extending from half a minute to four minutes, and then 
being washed in distilled water, were found to act very well, 
condensing one cubic inch and a half of gas in the space of 
eight or nine minutes, and rendering the tube warm (570.) . 

601. Strong sulphuric acid was very effectual in rendering 
the platina active. A plate (569.) was heated in it for a minute, 

* When heat does confer the property it is only by the destruction or dissi- 
pation of organic or other matter which had previously soiled the plate (632.* 
633. 634.). — Dec. 1838. 



Nov, 1833.] Effective preparation of platina plates . 175 

then washed and put into the mixed oxygen and hydrogen, 
upon which it acted as well as if it had been ipade the positive 
pole of a voltaic pile {570.) . 

602. Plates which, after being heated or electrized in alkali, 
or after other treatment, were found inert, immediately received 
power by being dipped for a minute or two, or even only for 
an instant, into hot oil of vitriol, and then into water. 

603. When the plate was dipped into the oil of vitriol, taken 
out, an & then heated so as to drive off the acid, it did not act, 
in consequence of the impurity left by the acid upon its surface. 

604. Vegetable acids, as acetic and tartaric, sometimes ren- 
dered inert platina active, at other times not. This; I believe, 
depended upon the character of the matter previously soiling 
the plates, and which iqay easily be supposed to be sometimes 
of such a nature as to be removed by these acids, and at other 
times not. Weak sulphuric acid showed the same difference, 
but strong sulphuric acid (601.) never failed in its action. 

605. The most favourable treatment, except that of making 
the plate a positive pole in strong acid, was as follows. The 
plate was held over a spirit-lamp flame, and when hot, rubbed 
with a piece of potassa fusa (caustic potash) , which melting, 
covered the metal with a coat of very strong alkali, and this 
was retained fused upon the surface for a second or two* : it 
was then put into water for four or five minutes to wash oft’ the 
alkali, shaken, and immersed for about a minute in hot strong 
oil of vitriol; from this it was removed into distilled water, 
where it was allowed to remain ten or fifteen minutes to remove 
the last traces of acid (582.). Being then put into a mixture 
of oxygen and hydrogen, combination immediately began, and 
proceeded rapidly ; the tube became warm, the platina became 
red hot, and the residue of the gases was inflamed. This effect 
could be repeated at pleasure, and thus the maximum pheno- 
menon could be produced without the aid of the voltaic battery. 

606. When a solution of tartaric or acetic acid was substi- 
tuted, in this mode of preparation, for the sulphuric acid, still 
the plate was found to acquire the same power, and would 

* The heat need not be raised so much as to make the alkali tarnish the 
platina, although if that effect does take place it does not prevent the ultimate 
Action 



176 Dobereiner* s extraordinary discovery . [Series VI. 

often produce explosion in the mixed gases ; but the strong 
sulphuric acid was most certain and powerful. 

607. If borax, or a mixture of the carbonates of potash and 
soda, be .fused on the surface of a platina plate, and that plate 
be well washed in water, it will be found to have acquired the 
power of combining oxygen and hydrogen, but only in a mo- 
derate degree ; but if, after the fusion and washing, it be dip- 
ped in the hot sulphuric acid (601.), it will become very active. 

608. Other metals than platina were then experimented with. 
Gold and palladium exhibited the power either when made the 
positive pole of the voltaic battery (570.), or when acted on by 
hot oil of vitriol (601.). When palladium is used, the action 
of the battery or acid should be moderated, as that metal is 
soon acted upon under such circumstances. Silver and cop- 
per could not be made to show any effect at common tempera- 
tures. 

609. There can remain no doubt that the property of indu- 
cing combination, which can thus be conferred upon masses of 
platina and other metals by connecting them with the poles of 
the battery, or by cleansing processes either of a mechanical 
or chemical nature, is the same as that which was discovered 
by Dobereiner*, in 1823, to belong in so eminent a degree to 
spongy platina, and which was afterwards so well experimented 
upon and illustrated by MM. Etulong and Thenardf, in 1823. 
The latter philosophers even quote experiments in which a 
very fine platina wire, which had been coiled up and digested 
in nitric, sulphuric, or muriatic acid, became ignited when put 
into a jet of hydrogen gasj. This effect I can now, produce at 
pleasure with either wires or plates by the processes described 
(570. 601. 605.) ; and by using a smaller plate cut so that it 
shall rest against the glass by a few points, and yet allow the 
water to flow off (fig. 59.), the loss of heat is less, the metal is 
assimilated somewhat to the spongy state, and the probability 
of failure almost entirely removed. 

610. M. Dobereiner refers the effect entirely to an electric 
action. He considers the platina and hydrogen as forming a 
voltaic element of the ordinary kind, in which the hydrogen, 

* Aunales de Chimie, tom. xxiv. p. 93. 

f Ibid. tom. xxiii. p. 44ft ; tom. xxiv. p. 380, % Ibid. tom. xxiv, p. 383. 



177 


Nov. 1833.] Dulong and Thenard on power ofplatina. 

being very highly positive, represents the zinc of the usual 
arrangement, and like it, therefore, attracts oxygen and com- 
bines with it *. 

611. In the two excellent experimental papers by MM. Du- 
long and Thenard f, those philosophers show that elevation of 
temperature favours the action, but does not alter its charac- 
ter; Sir Humphry DaVy's incandescent platina wire being the 
same phenomeiion with Dobereiner's spongy platina. They 
show that all metals have this power in a greater or smaller 
degree, and that it is even possessed by such bodies as char- 
coal, pumice, porcelain, glass, rock crystal, &c., when their 
temperatures are raised ; and that another of Davy's effects, 
in which oxygen and hydrogen had combined slowly together 
at a heat below ignition* was really dependent upon the pro- 
perty of the heated glass, which it has in common with the 
bodies named above. They state that liquids do not show 
this effect, at least that mercury, at or below the boiling point, 
has not the power; that it is not due to porosity; that the 
same body varies very much in its action, according to its state ; 
and that many other gaseous mixtures besides oxygen and 
hydrogen are affected, and made to act chemically, when the 
temperature is raised. They think it probable that spongy 
platina acquires its power from contact with the acid evolved 
during its reduction, or from the heat itself to which it is then 
submitted. 

(J12. MM. Dulong and Thenard express themselves with 
great caution on the theory of this action ; but, referring to 
the decomposing power of metals on ammonia when heated to 
temperatures not sufficient alone to affect the alkali, they re- 
mark that those metals which in this case are most efficacious, 
are the least so in causing the combination of oxygen and hy- 
drogen ; whilst platina, gold, &c., which have least power of 
decomposing ammonia, have most power of combining the ele- 
ments of water : — from which they are led to believe, that 
amongst gases, some tend to unite under the influence of me- 
tals, whilst others tend to separate , and that this property 
varies in ppposite directions with the different metals. At the 

* Annalcs d« Chimie, tom. xxiv. pp. 94, 96. Also Bibliothque Universelle, 
t<pn. xxiv. p. 64. 

t Ibid. tom. xxiii. p. 440 ; tom, xxiv. p. 380. 

N 



178 j Fusinieri on power of platina. [Series VI. 

close of their second paper they observe, that the action is of 
a kind that cannot be connected with any known theory ; and 
though it is very remarkable that the effects are transient, like 
those of most electrical actions, yet they state that the greater 
number of the results observed by them are inexplicable, by 
supposing them to be of a purely electric origin. 

613. Dr. Fusinieri has also written on this subject, and 
given a theory which he considers as sufficient to acgpunt for 
the phenomena *. He expresses the immediate cause thus : 
“ The platina determines upon its surface a continual renovation 
of concrete lamina of the combustible substance of the gases 
or vapours, which flowing over it arc burnt, pass away, and 
are renewed : this combustion at the surface raises and sus- 
tains the temperature of the metal/* The combustible sub- 
stance, thus reduced into imperceptible laminae, of which the 
concrete parts arc in contact with the oxygen, is presumed to be 
in a state combinable with the oxygen at a much lower tempe- 
rature than when it is in the gaseous state, and more in analogy 
with what is called the nascent condition. That combustible 
gases should lose their elastic state, and become concrete, assum- 
ing the form of exceedingly attenuated but solid strata, is con- 
sidered as proved by facts, some of which are quoted in the 
Giornalc di Fisica for 1824 f ; and though the theory requires 
that they should assume this state at high temperatures, and 
though the similar films of aqueous and other matter are dis- 
sipated by the action of heat, still the facts are considered as 
justifying the conclusion against all opposition of reasoning. 

614. The power or force which makes combustible gas or 
vapour abandon its elastic state in contact with a solid, that it 
may cover the latter with a thin stratum of its own proper sub- 
stance, is considered as being neither attraction nor affinity. 
It is able also to extend liquids and solids in concrete laminse 
over the surface of the acting solid body, and consists in a re- 
pulsion , which is developed from the parts of the solid body 
by the simple fact of attenuation, and is highest when the at- 
tenuation is most complete. The force has a progressive de- 
velopment, and acts most powerfully, or at first, in the Erec- 
tion in which the dimensions of the attenuated mass decrease, 
and then in the direction of the angles or comers which from 

* Giomale di Fisica, &c., 1825, tom. viii. p. 250. ' + pp. 188, 871, 



Nov. 1883.] Cleanness the essential condition . 179 

any cause may exist on the surface. This force not only 
causes spontaneous diffusion of gases and other substances 
over the surface* but is considered as very elementary in its 
v nature, and competent to account for all the phenomena of ca- 
pillarity, chemical affinity, attraction of aggregation, rarefac- 
tion, ebullition, volatilization, explosion, and other tliermome- 
tric effects, as well as inflammation, detonation, &c. &c. It is 
considered as a form of heat to which the term native caloric 
is given, and is still further viewed as the principle of the two 
electricities and the two magnetisms. 

615. I heave been the more anxious to give a correct abstract 
of Dr. Shtsinieri’s view, both because I cannot form a distinct 
idea of the power to which he refers the phenomena, and be- 
cause of my imperfect knowledge of the language in which the 
memoir is written. I would therefore beg to refer those who 
pursue the subject to the memoir itself. 

616. Not feeling, however, that the problem has yet been 
solved, I venture to give the view which seems to me sufficient, 
upon known principles , to account for the effect. 

617. It may be observed of this action, that, with regard to 
platina, it cannot be due to any peculiar, temporary condition, 
cither of an electric or of any other nature : the activity of 
plates rendered either positive or negative by the pole, or 
cleaned with such different substances as acids, alkalies, or 
water ; charcoal, emery, ashes, or glass ; or merely heated, is 
sufficient to negative such an opinion. Neither does it de- 
pend upon the spongy and porous, or upon the compact and 
burnished, or upon the massive or the attenuated state of the 
metal, for in any of these states it may be rendered effective, 
or its action may be taken away. The only essential condi- 
tion appears to be a perfectly clean and metallic surface , for 
whenever that is present the platina acts, whatever its form 
and condition in other respects may be ; and though variations 
in the latter points will very much affect the rapidity, and 
therefore the visible appearances and secondary effects, of the 
action^ i. e. the ignition of the metal and the inflammation of 
the |$ies, they, even in their most favourable state, cannot 
produce any effect unless the condition of a clean, pure, metallic 
surface be also fulfilled. 

618; The effect is evidently produced by most, if not all, 
n 2 



180 Combining power of platina. .[Series VI. 

solid bodies, weakly perhaps by many of them, but rising to a 
high degree in platina. Dulong and TJienard have very phi- 
losophically extended our knowledge of the property to its 
possession by all the metals, and by earths, glass, stones, &c. 
(611.) ; and every idea of its being a known and recognised 
electric action is in this way removed. 

619. All the phenomena connected with this subject press 
upon my mind the conviction that the effects in question are 
entirely incidental and of a secondary nature ; that they are 
dependent upon the natural conditions of gaseous elasticity, 
combined with the exertion of that attractive force possessed 
by many bodies, especially those which are solid, in an emi- 
nent degree, and probably belonging to all ; by which they are 
drawn into association more or less close, without at the same 
time undergoing chemical combination, though often assuming 
the condition of adhesion ; and which occasionally leads, under 
very favourable circumstances, as in the present instance, to 
the combination of bodies simultaneously subjected to this 
attraction. I am prepared myself to admit (and probably many 
others are of the same opinion), both with respect to the at- 
traction of aggregation and of chemical affinity, that the sphere 
of action of particles extends beyond those other particles with 
which they are immediately and evidently in union (523.), and 
in many cases produces effects rising into considerable im- 
portance : and 1 think that this kind of attraction is a deter- 
mining cause of Dobereiner's effect, and of the many others of 
a similar nature. 

620. Bodies which become wetted by fluids with which they 
do not combine chemically, or in which they do not dissolve, 
arc simple and well known instances of this kind of attrac- 
tion. 

621. All those cases of bodies which being insoluble in water 
and not combining with it are hygrometric, and condense its 
vapour around or upon their surface, are stronger instances of 
the same power, and approach a little nearer to the cases under 
investigation. If pulverised clay, protoxide or peroxide of 
iron, oxide of manganese, charcoal, or even metals, as spongy 
platina or precipitated silver, be put into an atmosphere con- 
taining vapour of water, they soon become mpist by virfue of 
an attraction which is able to condense the Vapour upon. 



181 


Nov. 1833.] Theory of its action . 

although not to combine it with, the substances; and if, as is 
well known, these bodies so damped be put into a dry atmo- 
sphere, as, for instance, one confined over sulphuric acid, 
or if they be heated, then they yield up this water again almost 
entirely, it not being in direct or permanent combination*. 

622. Still better instances of the power I refer to, because 
they are more analogous to the cases to be explained, are fur- 
nished by^he attraction existing between glass and air, so well 
known to barometer and thermometer makers, for here the ad- 
hesion on attraction is exerted between a solid and gases, bodies 
having very different physical conditions, having no power "of 
combination with each other, and each retaining, during the 
time of action, its physical state unchangcdf. When mercury 
is poured into a barometer tube, a film of air will remain 
between the metal and glass for months, or, as far as is known, 
for years, for it has never been displaced except by the action 
of means especially fitted for the purpose. These consist in 
boiling the mercury, or in other words, of forming an abun- 
dance of vapour, which coming in contact with every part of 
the glass and every portion of surface of the mercury, gradu- 
ally mingles with, dilutes, and carries off the air attracted by, 
and adhering to, those surfaces, replacing it by other vapour, 
subject to an equal or perhaps greater attraction, but which 
when cooled condenses into the §ame liquid as that with which 
the tube is filled. 

623. Extraneous bodies, which, acting as nuclei in crystal- 
lizing or depositing solutions, cause deposition of substances 
on them, when it does not occur elsewhere in the liquid, seem 
to produce their effects by a power of the same kind, i. e. a 
power of attraction extending to neighbouring particles, and 
causing them to become attached to the nuclei, although it is 
not strong enough to make them combine chemically with their 
substance. 

* I met at Edinburgh with a case, remarkable as to its extent, of liygrometric 
action, assisted a little perhaps by very slight sol\ eut power. Some turf had 
been well dried by long exposure in a coveied place to thu atmosphere, but 
being then submitted to the action of a hydrostatic press, it yielded, by the 
mere inflttence of the pressure, 54 per cent, of water. 

f. Fusinieri and Bellani consider the air as forming solid concrete films . 
these cases.—' Giornale di Fisica, tom. viii. p. 202. 1825. 



182 


Combining power of platina. ^Series Ylr 

624. It would appear from many cases of nuclei in solutions, 
and from the effects of bodies put into m atmospheres containing 
the vapours of water, or camphor, or iodine^ &c., as if this at- 
traction were in part elective, partaking in its characters both 
of the attraction of aggregation and chemical affinity ; nor is 
this inconsistent with, but agreeable to, the idea entertained, 
that it is the power of particles acting, not upon r others with 
which they can immediately and intimately combinef but upon 
such as are cither more distantly situated with respect to them, 
or which, from previous condition, physical constitution, or 
feeble relation, are unable to enter into decided union with 
them. 

625. Then, of all bodies, the gasps are those which might 
be expected to show some mutual action whilst jointly under 
the attractive influence of the platina or other solid acting 
substance. Liquids, such as water, alcohol, &c., are in so 
dense and comparatively incompressible a state, as to favour 
no expectation that their particles should approach much 
closer to each other by the attraction of the body to which 
they adhere, and yet that attraction must (according to its 
effects) place their particles as near to those of the solid wetted 
body as they are to each other, and in many cases it is evident 
that the former attraction is the stronger. But gases and va- 
pours are bodies competent to*suffer very great changes in the 
relative distances of their particles by external agencies ; and 
where they are in immediate contact with the platina, the ap- 
proximation of the particles to those of the metal may be very 
great. In the case of the hygrometric bodies referred to (621.), 
it is sufficient to reduce the vapour to the fluid state, frequently 
from atmospheres so rare that without this influence it would 
be needful to compress them by mechanical force into a bulk 
not more than ^ or even ^ of their original volume before 
the vapours would become liquids. 

626. Another most important consideration in relation to 
this action of bodies, and which, as far as I am aware, has not 
hitherto been noticed, is the condition of elasticity under 
which the gases are placed against the acting surface. We 
have but very imperfect notions of the real and intimate con- 
ditions of the particles of a body existing in the solid, the liquid, 
and the gaseous state ; but when we speak of the gaseous state 



Nov. 1833.] Favourable condition of the gases . » 183 

as being due to the mutual repulsions of the particles or of 
their atmospheres, although we may err in imagining each par- 
ticle to be a little nucleus to an atmosphere of heat, or electri- 
city, or any jother agent, we arc still not likely to be in error in 
considering the elasticity as dependent on mutuality of action. 
Now this mutual relation fails altogether on the side of the 
gaseous particles next to the platina, and we might be led to 
expect ^ priori a deficiency of clastic force there to at least 
one half; for if, as Dalton has shown, the elastic force of the 
particles of one gas cannot act against the clastic force of the 
particles of another, the two being as vacua to each other, so 
is it far less likely that the particles of the platina can exert 
any influence on those of the gas against it, such as would be 
exerted by gaseous particles of its own kind. 

627. But the diminution of power to one half on the side of 
the gaseous body towards the metal is only a slight result of 
what seems to me to flow as a necessary consequence of the 
known constitution of gases. An atmosphere of one gas or 
vapour, however dense or compressed, is in effect as a vacuum 
to another ; thus, if a little water were put into a vessel contain- 
ing a dry gas, as air, of the pressure of one hundred atmo- 
spheres, as much vapour of the water would rise as if it were 
in a perfect vacuum. Here the particles of watery vapour ap- 
pear to have no difficulty in approaching within any distance of 
the particles of air, being influenced solely by relation to par- 
ticles of their own kind ; and if it be so with respect to a body 
having the same elastic powers as itself, how much more surely 
must it be so with particles, like those of the platina, or other 
limiting body, iVhich at the same time that they have not these 
elastic powers, are also unlike it in nature. lienee it would 
seem to result that the particles of hydrogen or any other gas 
or vapour which are next to the platina, &c., must be in such 
contact with it as if they were in the liquid state, and there- 
fore almost infinitely closer to it than they are to each other, 
even though the tnetal be supposed to exert no attractive in- 
fluence over them . 

A third and very important consideration in favour of 
the mutual^ action qf gases under these circumstances is their 
jjeyfhdt miscibility. If fluid bodies capable of combining toge- 
ther me also capable of mixture, they do combine when they 



184 Combining power of platina. [Series VI. 

are mingled, not waiting for any other determining circum- 
stance ; but if two such gases as oxygen and hydrogen are put 
together, though they are elements having such powerful affi- 
nity as to unite naturally under a thousand different circum- 
stances, they do not combine by mere mixture. Still it is evi- 
dent that, from their perfect association, the particles are in the 
most favourable state possible for combination, upon the super- 
vention of any determining cause, such either as the^negative 
action of the platina in suppressing or annihilating, as it were, 
tteir elasticity on its side ; or the positive action of the metal 
in condensing them against its surface by an attractive force ; 
or the influence of both together. 

629. Although there are not many distinct cases of combina- 
tion under the influence of forces e/ternal to the combining 
particles, yet there are sufficient to remove any difficulty which 
might arise on that ground. Sir James Hall found carbonic 
acid and lime to remain combined under pressure at tempera- 
tures at which they would not have remained combined if the 
pressure had been removed ; and I have had occasion to observe 
a case of direct combination in chlorine*, which being com- 
pressed at common temperatures will combine with water, and 
(orm a definite crystalline hydrate, incapable either of being 
formed or of existing if that pressure be removed. 

630. The course of events when platina acts upon, and com- 
bines oxygen and hydrogen, may be stated, according to these 
principles, as follows. From the influence of the circumstances 
mentioned (619. &c.), i. e. the deficiency of elastic power and 
the attraction of the metal for the gases, the latter, when they 
are in association with the former, are so far condensed as to be 
brought within the action of their mutual affinities at the exist- 
ing temperature ; the deficiency of elastic power, not merely 
subjecting them more closely to the attractive influence of the 
metal, but also bringing them into a more favourable state for 
union, by abstracting a part of that power (upon which depends 
their elasticity,) which elsewhere in the mass of gases is op- 
posing their combination. The consequence of their combina- 
tion is the production of the vapour of water and m elevation 
of temperature. But as the attraction of the platina for the 
water formed is not greater than for the gases, if so grea£, 

* Philosophical Transactions, 1823, p. 161. 



Theory of the effects. 


185 


Nov. 1833.] 


(for the metal is scarcely hygrometric,) the vapour is quickly 
diffused through the # remaining gases ; fresh portions of the 
latter, therefore, come into juxtaposition with the metal, com- 
bine, and the fresh vapour formed is also diffused, allowing 
new portions of gas to be acted upon. In this way the process 
advances, but is accelerated by the evolution of heat, which is 
known by experiment to facilitate the combination in propor- 
tion to intensity, and the temperature is thus gradually ex- 
alted until ignition results. 

631. The dissipation of the vapour produced at the surface 
of the platina, and the contact of fresh oxygen and hydrogen 
with the metal, form no difficulty in this explication. The 
platina is not considered as causing the combination of any par- 
ticles with itself, but only associating them closely around it ; 
and the compressed particles arc as free to move from the pla- 
tina, being replaced by other particles, as a portion of dense 
air upon the surface of the globe, or at the bottom of a deep 
mine, is free to move by the slightest impulse, into the upper 
and rarer parts of the atmosphere. 

632. It can hardly be necessary to give any reasons why pla- 
tina does not show this effect under ordinary circumstances. 
It is then not sufficiently clean (617.), and the gases are pre- 
vented from touching it, and suffering that degree of effect 
which is needful to commence their combination at common 
temperatures, and which they can only experience at its sur- 
face. In fact, the very power which causes the combination 
of oxygen and hydrogen, \s competent, under the usual casual 
exposure of platina, to condense extraneous matters upon its 
surface, which soiling it, take away for the time its power of 
combining oxygen and hydrogen, by preventing their contact 
with it (598.). 

633. Clean platina, by which I mean such as has been made 
the positive pole of a pile (570.), or has been treated with acid 
(605.), and has then been put into distilled water for twelve or 
fifteen minutes, has a peculiar friction when one piece is rubbed 
against another. It wets freely with pure water, even after 
it has been shaken and dried by the heat of a spirit lamp ; 
and if made the pole of a voltaic pile in a dilute acid, it evolves 
minute bubbles from every part of its surface. But platina in 
its common state wants that peculiar friction : it will not wet 



^186 Character of clean surfaces . [Series VI. 

freely with water as the clean platina does; and when made 
the positive pole of a pile, it for a time ^ives off large bubbles, 
which seem to cling or adhere to the metal, and are evolved 
at distinct and separate points of the surface. These appear- 
ances and effects, as well as its want of power on oxygen and 
hydrogen, are the consequences, and the indications, of a soiled 
surface. 

634. I found also that platina plates which had beei^cleaned 
perfectly soon became soiled by mere exposure to the air; for 
after twenty-four hours they no longer moistened freely with 
water, but the fluid run up into portions, leaving part of the 
surface bare, whilst other plates which had been retained in water 
for the same time, when they were dried (580.) did moisten, and 
gave the other indications of a clean surface. 

635. Nor was this the case with platina or metals only, but 
also with earthy bodies. Rock crystal and obsidian would not 
wet freely upon the surface, but being moistened with strong 
oil of vitriol, then w ashed, and left in distilled water to remove 
all the acid, they did freely become moistened, wdiether they 
were previously dry or whether they were left wet ; but being 
dried and left exposed to the air for twenty-four hours, their 
surface became so soiled that water would not then adhere 
freely to it, but ran up into partial portions. ' Wiping with a 
cloth (even the cleanest) was still worse than exposure to air ; 
the surface either of the minerals or metals immediately became 
as if it were slightly greasy. The floating upon water of small 
particles of metals under ordinary circumstances is a conse- 
quence of this kind of soiled surface. The extreme difficulty of 
cleaning the surface of mercury when it has once been soiled 
or greased, is due to the same cause. 

636. The same reasons explain why the power of the platina 
plates in some circumstances soon disappear, and especially 
upon use : MM. Dulong and Thenard have observed the same 
effect with the spongy metal*, as indeed have all those who 
have used Dobereiner's instantaneous light machines. If left 
in the air, if put into ordinary distilled water, if made to act 
upon ordinary oxygen and hydrogen, they can still find in all 
these cases that minute portion of impurity which, when pnee 
in contact with the surface, of the platina, is retained there, and 

* Aaaales de Ohimie, tom. xxiv. p. 386. 



Nov. 1833.] Interferences : — olefiant gas . 187 

is sufficient to prevent its full action upon oxygen and hydrogen 
at common temperatures : a slight elevation of temperature is 
again sufficient to compensate this effect, and cause combina- 
tion. 

637. No state of a solid body can be conceived more favour- 
able for the production of the effect than that which is possessed 
by platina obtained from the ammonio-muriate by heat. Its 
surfae% is most extensive and pure, yet very accessible to the 
gases brought in contact with it : if placed in impurity, the in- 
terior, as Thcnard and Dulong have observed, is preserved 
clean by the exterior ; and as regards temperature, it is so bad 
a conductor of heat, because of its divided condition, that 
almost all which is evolved by the combination of the first por- 
tions of gas is retained within the mass, exalting the tendency 
of the succeeding portions to combine. 

038. I have now to notice some very extraordinary inter- 
ferences with this phenomenon, dependent, not upon the nature 
or condition of the metal or other acting solid, but upon the 
presence of certain substances mingled with the gases acted 
upon; and as I shall have occasion to speak frequently of a 
mixture of oxygen and hydrogen, I wish it always to be under- 
stood that I mean a mixture composed of one volume oxygen 
to two volumes of hydrogen* being the proportions that form 
water. Unless otherwise expressed, the hydrogen was always 
that obtained by the action of dilute sulphuric acid on pure 
zinc, and the oxygen that obtained by the action of heat from 
the, chlorate of potassa, 

639. Mixtures of oxygen and hydrogen with air , containing 
one fourth, one half, and even two thirds of 'the latter, being 
introduced with prepared platina plates (570. 605.), into tubes, 
were acted upon almost as well as if no air were present : the 
retardation was far less than might have been expected from 
the mere dilution and consequent obstruction to the contact of 
the gases with the plates. In two hours and a half nearly all 
the oxygen and hydrogen introduced as mixture was gone. 

BnUwhen similar experiments were made with olefiant 
(the platiha plates having been made the positive poles of 
a voltaic pile (570.) in acid) , very different results occurred. 
A mixture was made of 29‘2 volumes hydrogen and 14*6 volumes 



188 


Interferences : — carbonic oxide . [Series VI. 


oxygen, being the proportions for water; and to this was added 
another mixture of 3 volumes oxygen and one volume olefiant 
gas, so that the olefiant gas formed but T Vth P ar ^ °f whole ; 
yet in this mixture the platina plate would not act in forty-five 
hours. The failure was not for want of any power in the plate, 
for when after that time it was taken out of this mixture and put 
into one of oxygen and hydrogen, it immediately acted, and in 
seven minutes caused explosion of the gas. This resvAt was 
obtained several times, and when larger proportions of olefiant 
gas were used, the action seemed still more hopeless. 

641. A mixture of forty-nine volumes oxygen and hydrogen 
(638.) with one volume of olefiant gas had a w ell -prepared 
platina plate introduced. The diminution of gas was scarcely 
sensible at the end of two hours, during which it was watched ; 
but on examination twenty-four hours afterwards, the tube was 
found blown to pieces. The action, therefore, though it had 
been very much retarded, had occurred at last, and risen to a 
maximum. 

642. With a mixture of ninety -nine volumes of oxygen and 
hydrogen (638.) with one of olefiant gas, a feeble action was 
evident at the end of fifty minutes; it went on accelerating (630.) 
until the eighty-fiftli minute, and then became so intense that 
the gas exploded. Here also the retarding effect of the olefiant 
gas was very beautifully illustrated. 

643. Plates prepared by alkali and acid (605.) produced 
effects corresponding to those just described. 

644. It is perfectly clear from these experiments, that ole- 
fiant gas , even in small quantities, has a very remarkable influ- 
ence in preventing the combination of oxygen and hydrogen 
under these circumstances, and yet without at all injuring or 
affecting the power of the platina. 

645. Another striking illustration of similar interference may 
be shown in carbonic oocide ; especially if contrasted with car- 
bonic acid. A mixture of one volume oxygen and hydrogen 
(638.) with four volumes of carbonic acid was affected at once 
by a platina plate prepared with acid, &c. (605.), and in one 
hour and a quarter nearly all the oxygen and hydrogen was 
gone. Mixtures containing less carbonic acid were still more 
readily affected. 

616. But when carbonic oxide was substituted for the car* 



189 


Nov. 1833.] Interferences: — of various substances, 

bonic acid, not the slightest effect of combination was pro- 
duced ; and when the carbonic oxide was only one eighth of 
the whole volume, no action occurred in forty and fifty hours. 
Yet the plates had not lost their power ; for being taken out 
and put into pure oxygen and hydrogen, they acted well and 
at once, 

647. IVo volumes of carbonic oxide and one of oxygen were 
mingle<^with nine volumes of oxygen and hydrogen (638). 
This mixture was not affected by a plate which had been made 
positive in acid, though it remained in it fifteen hours. But 
when to the same volumes of cai'bonic oxide and oxygen were 
added thirty-three volumes of oxygen and hydrogen, the car- 
bonic oxide being then only ^th part of the whole, the plate 
acted, slowly at first, and at the end of forty-two minutes the 
gases exploded. 

648. These experiments were extended to various gases and 
vapours, the general results of which may be given as follow. 
Oxygen, hydrogen, nitrogen, and nitrous oxide, when used to 
dilute the mixture of oxygen and hydrogen, did not prevent 
the action of the plates even when they made four-fifths of 
the whole volume of gas acted upon. Nor was the retarda- 
tion so great in any case as might have been expected from 
the mere dilution of the oxygen and hydrogen, and the conse- 
quent mechanical obstruction^ to its contact with the platina. 
The order in which carbonic acid and the>c substances seemed 
to stand was as follows, the first interfering least with the 
action; nitrous oxide , hydrogen , carbonic acid, nitrogen , oxygen’. 
but it is possible the plates were not equally well prepared in 
all the cases, aud that other circumstances also were unequal ; 
consequently more numerous experiments would be required 
to establish the order accurately, 

649. As to cases of retardation , the powers of olefiant gas 
and carbonic oxide have been already described. Mixtures of 
oxygen and hydrogen, containing from ^th to ^th of sulphu- 
retted hydrogen or phosphuretted hydrogen, seemed to show 
a little action at first, but were not further affected by the pre- 
pared plates* though in contact with them for seventy hours. 
Wlren the plates were removed they had lost all power over 
# pute oxygen and hydrogen, and the interference of these gases 
was therefore of a different nature from that of the two former* 
having permanently affected the plate. 



190 Interferences : — using spongy platina. [Series VI. 

650. A small piece of cork was dipped in sulplmret of car_ 
bon and passed up through water into a tube containing oxy- 
gen and hydrogen (638.), so as to difeuse a portion of its 
vapour through the gases. A plate being introduced appeared 
at first to act a little, but after sixty-one hours the diminution 
was very small. Upon putting the same plate into a ppre mix- 
ture of oxygen and hydrogen, it acted at once and powerfully* 
having apparently suffered no diminution of its force. ( 

651. A little vapour of ether being mixed with the oxygen 
and hydrogen retarded the action of the plate, but did not pre- 
vent it altogether. A little of the vapour of the condensed oil- 
gas liquor* retarded the action still more, but not nearly so 
much as an equal volume of olefiant gas would have done. In 
both these cases it was the original* oxygen and hydrogen 
which combined together, the ether and the oil-gas vapour 
remaining unaffected, and in both cases the plates retained the 
power of acting on fresh oxygen and hydrogen. 

652. Spongy platina was then used in place of the plates, 
and jets of hydrogen mingled w ith the different gases thrown 
against it in air. The results were exactly of the same kind, 
although presented occasionally in a more imposing form. 
Thus, mixtures of one volume of olefiant gas or carbonic oxide 
with three of hydrogen could not heat the spongy platina when 
the experiments were commenced at common temperatures; 
but a mixture of equal volumes of nitrogen and hydrogen acted 
very well, causing ignition. With carbonic acid the results 
were still more striking. A mixture of three volumes of. that 
gas with one of hydrogen caused ignition of the platina, yet 
that mixture would not continue to burn from the jet when 
attempts were made to light it by a taper. A mixture even of 
seven volumes of carbonic acid and one ofdiydrogcn will thus 
cause the ignition of cold # spongy platina, and yet, as if to sup- 
ply a contrast, than which none can be greater, it cannot 'burn 
at a taper , but causes the extinction of the latter. On the 
other hand, the mixtures of carbonic oxide or olefiant gas, 
which can do nothing wfith the platina, are inflamed by the 
taper, burning well. 

653. Hydrogen mingled with the , vapour of ether or oilgas 
liquor causes the ignition of the spongy platina. The mixturq 
with oil-gas burns with a flame far brighter than that of the 

* Philosophical Transactions, 1825, p. 440. 



191 


Nov. 1838.] Interferences with platina action . 

mixture of hydrogen and olefiant gas already referred to, so 
that it would appear that the 'retarding action of the hydro- 
carbons is not at all *Ln proportion merely to the quantity of 
carbon present. 

654. In connexion with these interferences, I must state, 
that hydrogen itself, prepared from steam passed over ignited 
iron, was found when mingled with oxygen to resist the action 
of plating. It* had stood over water seven days, and had lost 
all fetid smell ; but a jet of it would not cause the ignition of 
spongy platina, commencing at common temperatures; nor 
would it combine with oxygen in a tube cither under the influ- 
ence of a prepared plate or of sjiongy platina. A mixture of 
one volume of this gas with three of pure hydrogen, and the 
due proportion of oxygeli, was not affected by plates after fifty 
hours. I am inclined to refer the effect to carbonic oxide pre- 
sent in the gas, but have not had time to verify the suspicion. 
The power of the plates was not destroyed (610. 616.). 

655. Such are the general facts of these remarkable inter- 
ferences, Whether the effect produced by such small quan- 
tities of certain gases depends upon any direct action which 
they may exert upon the particles of oxygen and hydrogen, 
by which the latter are rendered less inclined to combine, or 
whether it depends upon their modifying the action of the plate 
temporarily (for they produce no real change on it), by invest- 
ing it through the agency of a stronger attraction than that of 
the hydrogen, or otherwise, remains to be decided by more ex- 
tended experiments. 

656. The theory of action which I have given for the original 
phenomena appears to me quite sufficient to account for all the 
effects by reference to known properties, and dispenses with 
the assumption of any new power of matter. I have pursued 
this subject at some length, as one of great consequence, be- 
cause I am convinced that the superficial actions of matter, 
whether between two bodies, or of one piece of the same body, 
and the actions of particles not directly or strongly in combi- 
n at ion, are becoming daily more and more important to our 
thecas of chemical as well as mechanical philosophy*. In 

* As a curious illustration of the influence of mechanical forces over chemi- 
cal affinity, I will quote the refusal of certain substances to effloresce when 



192 Relation of liquid and vaporous particles. [Series VI. 

all ordinary cases of combustion it is evident that an action of 
the kind considered, occurring upon the surface of the carbon 
in the fire, and also in the bright part V)f a flame, must have 
great influence over the combinations there taking place.' 

657. The condition of elasticity upon the exterior of the 
gaseous or vaporous mass already referred to (626. 627.), must 
be connected directly with the action of solid bodies, as nuclei, 
on vapours, causing condensation upon them in preference to 
any condensation in the vapours themselves ; and in the well- 
known effect of nuclei on solutions a similar condition may have 
existence (623.), for an analogy in condition exists between the 
parts of a body in solution, and those of a body in the vaporous 
or gaseous state. This thought leads us to the consideration 
of what are the respective conditions at the surfaces of contact 
of two portions of the same substance at the same temperature, 
one in the solid or liquid, and the other in the vaporous state ; 
as, for instance, steam and water. It would seem that the par- 
ticles of vapour next to the particles of liquid are in a different 
relation to the latter to what they would be with respect to any 
other liquid or solid substance; as, for instance, mercury or 
platina, if they were made to replace the water, i. e . if the view 
of independent action which I have taken (626. 627.) as a con- 
sequence of Dalton's principles, be correct. It would also seem 
that the mutual relation of similar particles, and the indiffer- 
ence of dissimilar particles which Dalton has established as a 
matter of fact amongst gases and vapours, extends to a certain 
degree amongst solids and fluids, that is, when they are in 
relation by contact with vapours, cither of their own substance 
or of other bodies. But though I view these points as of great 
importance with respect to the relations existing between dif- 
ferent substances and their physical constitution in the solid, 

tlieir surfaces are perfect, which yield immediately upon the surface being 
broken. If crystals of caibonate of soda, or phosphate of soda, or sulphate 
of soda, having no part of their surfaces broken, be preserved irom external 
violence, they will not effloresce., I have thus retained crystals of carbonate 
of soda perfectly transparent and unchanged from September 1827 to January 
1833 ; and crystals of sulphate of soda from May 1832 to the present time, 
November 1838. If any part of the surface were scratched or broken, then 
efflorescence began at that part, and covered the whole. The crystals were 
merely placed in evaporating basins and covered with paper. » 



193 


Nov. 1833.] Influence of the nascent state. 

liquid, or gaseous state, I have not sufficiently considered them 
to' venture any strong opinions or statements here * * * § . 

658. There are numerous well-known cases, in which’ sub- 
stances, such as oxygen and hydrogen, act readily in their 
nascent state, and produce chemical changes which they are not 
able to effect if once they have assumed the gaseous condition. 
Such instances are very common at the poles of the voltaic 
pile, an^ are, I think, easily accounted for, if it be considered 
that at the moment of separation of any such particle it is 
entirely surrounded by other particles of a different kind with 
which it is in close contact, and has not yet assumed those 
relations and conditions which it has in its fully developed state, 
and which it can only assume by association with other particles 
of its own kind. For, at the moment, its elasticity is absent, 
and it is in the same relation to particles with which it is in 
contact, and for which it has an affinity, as the particles of 
oxygen and hydrogen are to each other on the surface of clean 
platina (620. 627.) . 

659. The singular effects of retardation produced by very 
small quantities of some gases, and not by large qtiantities of 
others (640. 645. 652.), if dependent upon any relation of the 
added gas to the surface of the solid, will then probably be 
found immediately connected with the curious phenomena which 
are presented by different gases when passing through narrow 
tubes at low pressures, which I observed many years ago f ; 
and this action of surfaces must, I think, influence the highly 
interesting phenomena of the diffusion of gases, at least in the 
form in which it has been experimented upon by Mr. Graham 
in 1829 and 1831 J, and also by Dr. Mitchell of Philadelphia § 
in 1830. It seems very probable that if such h substance as 
spongy platina were used, another law for the diffusion of gases 
under the circumstances would come out than that obtained by 
the use of plaster of Paris. 

* In reference to this paragraph and also 626, see a correction by Dr. C. 
Henry, in his valuable paper on this curious subject. Philosophical Magazine, 
1835, vol. vi. p. — Dec. 1838. 

f Quarterly .Journal of Science, 1819, vol. vii. p. 106. 

t Quarterly Journal of Science, vol. xxviii. p. 74., and Edinburgh Trans- 
actions, 1831, * * 

§ Journal of the Royal Institution for 1831, p. 101. 



194 Peculiar conditions of metals. [Series YI. 

660. I intended to have followed this section by one on the 
secondary piles of Ritter, and the peculiar properties of the 
poles of the pile, or of metals through 0 which electricity has 
passed, which have been observed by Ritter, Yan Marum, 
Yelin, Do la Rive, Marianini, Berzelius, and others. It ap- 
pears to me that all these phenomena bear a satisfactory ex- 
planation on known principles, connected with the investigation 
just terminated, and do not require the assumption of p-ny new 
state or new property. But as the experiments advanced, 
especially those of Marianini, require very careful repetition 
and examination, the necessity of pursuing the subject of elec- 
tro-chemical decomposition obliges me for a time to defer the 
researches to which I have just referred. 

Royal Institution , 

November 30, 1833. 



193 


SEVENTH SERIES. 

§ 11. On Electro-chemical Decomposition, continued*. «([ iv. 
On sojge general conditions of Electro-decomposition. v. On 
a new Measurer of Volta-electricity . vi. On the primary 
or secondary character of bodies evolved in Electro -decom- 
position. Tf vii. On the definite nature and extent of Elec- 
tro-chemical Decompositions. § 13. On the absolute quantity 
of Electricity associated with the particles or atoms of 
Matter. 

Received January 9. — Read January 23, February G and 13, 1834. 

Preliminary. 

661. The theory which I believe to be a true expression of 
the facts of electro-chemical decomposition, and which I have 
therefore detailed in a former series of these Researches, is so 
much at variance with those previously advanced, that I find 
the greatest difficulty in stating results, as I think, correctly, 
whilst limited to the use of terms which are current with a cer- 
tain accepted meaning. Of this kind is the term pole, with its 
prefixes of positive and negative, and the attached ideas of at- 
traction and repulsion. The general phraseology is that the 
positive pole attracts oxygen, acids, &c., or more cautiously, 
that it determines their evolution upon its surface ; and that the 
negative pole acts in an equal manner upon hydrogen, combus- 
tibles, metals, and bases. According to my view, the deter- 
mining force is not at the poles, but within the body under 
decomposition ; and the oxygen and acids are rendered at the 
negative extremity of that body, whilst hydrogen, metals, &c., 
are evolved at the positive extremity (318. 524.). 

662. To avoid, therefore, confusion and circumlocution, and 
for the sake pf greater precision of expression than I can other- 
wise obtain, I have deliberately considered the subject with two 
friends, and with their assistance and concurrence in framing 

Refer to the note after 1047, Series VIII. — Dec. 1838. 
o 2 



196 Definitions of new terms. [Series VII. 

them, I purpose henceforward using certain other terms, which 
I will now define. The poles , as they are usually called, are 
only the doors or ways by which the electric current passes into 
and out of the decomposing body (556.) ; and they of course, 
when in contact with that body, are the limits of its extent in 
the direction of the current. The term has been generally ap- 
plied to the metal surfaces in contact with the decomposing 
substance ; but whether philosophers generally would^also ap- 
ply it to the surfaces of air (465.471.) and water (493.), against 
which I have effected electro-chemical decomposition, is sub- 
ject to doubt. In place of the term pole, I propose using that 
of Electrode *, and I mean thereby that substance, or rather 
surface, whether of air, water, metal, or any other body, which 
bounds the extent of the decomposing matter in*the direction 
of the electric current. 

663. The surfaces at which, according to common phraseo- 
logy, the electric current enters and leaves a decomposing body, 
are most important places of action, and require to be distin- 
guished apart from the poles, with which they are mostly, and 
the electrodes, with which they are always, in contact. Wishing 
for a natural standard of electric direction to which I might 
refer these, expressive of their difference and at the same time 
free from all theory, I have thought it might be found in the 
earth. If the magnetism of th/3 earth be due to electric cur- 
rents passing round it, the latter must be in a constant direction, 
which, according to present usage of speech, would be from 
east to west, or, which will strengthen this help to the memory, 
that in which the sun appears to move. If in any case of elec- 
tro-decomposition we consider the decomposing body as placed 
so that the current passing through it shall be in the same 
direction, and parallel to that supposed to exist in the earth, then 
the surfaces at which the electricity is passing into and out of 
the substance would have an invariable reference, and exhibit 
constantly the same relations of powers. Upon this notion we 
purpose calling that towards the east the anode f, and that 
towards the west the cathode { ; and whatever changes may take 
place in our views of the nature of electricity and electrical 
* rfktKTpovj and <58os a way. * 

t £vo> upwards, and 6B6s a way ; the way which the sun rises. 

X Kara downwards, and 686s a way ; the way which the sun sets, 



Jan. 1834.] Definitions of new terms . 197 

action, as they must affect the natural standard referred to, in 
the same direction, an£ to an equal amount with any decom- 
posing substances to which these terms may at any time be 
applied, there seems no reason to expect that they will lead to 
confusion, or tend in any way to support false views. The 
anode is therefore that surface at which the electric current ac- 
cording to our present expression, enters : it is the negative 
extremity of the decomposing body ; is where oxygen, chlorine, 
acids, &c:, are evolved; and is against or opposite the positive 
electrode. The cathode is that surface at which the current 
leaves the decomposing body ; and is its positive extremity ; the 
combustible bodies, metals, alkalies, and bases, are evolved there, 
and it is in contact withjdie negative electrode. 

604. I shall have occasion in these Researches, also, to class 
bodies together according to certain relations derived from their 
electrical actions (822.) ; and wishing to express those relations 
without at the same time involving the expression of any hypo- 
thetical views, I intend using the following names and terms. 
Many bodies are decomposed directly by the electric current, 
their elements being set free : these I propose to (‘all electro- 
lytes*. Water, therefore, is an electrolyte. The bodies which, 
like nitric or sulphuric acids, arc decomposed in a secondary 
manner (752. 757.), are not included under this term. Then 
for electro-chemically decomposed, I shall often use the term 
electrolyzed , derived in the same way, and implying that the 
body spoken of is separated into its components under the in- 
fluence of electricity : it is analogous in its sense and sound to 
analyze , which is derived in a similar manner. The term elec- 
trotytical will be understood at once : muriatic acid is electro- 
lytical, boracic acid is not. 

665. Finally, I require a term to express those bodies which 
can pass to the electrodes , or, as they are usually called, the 
poles. Substances are frequently spoken of as being electro- 
negative, or electro-positive, according as they go under the 
supposed influence of a direct attraction to the positive or nega- 
tive pole. But these terms are much too significant for the use 
to which I should have to put them; for though the meanings are 
perhaps right, they are only hypothetical, and may be wrong ; 
apd then, through a very imperceptible, but still very dangerous, 
* rfktKTpov, and Avw, solvo. N. Electrolyte, V. Electrolyze. 



198 Definitions of new terms. [Series VII. 

because continual, influence, they do great injury to science, 
by contracting and limiting the habitual views of those engaged 
in pursuing it. I propose to distinguish such bodies by calling 
those anions* which go to the anode of the decomposing body ; 
and those passing to the cathode , cations f; and when I have 
occasion to speak of these together, I shall call them ions. 
Thus, the chloride of lead is an electrolyte , and when electro- 
lyzed evolves the two ions , chlorine and lead, the fonder being 
an anion, and the latter a cation. 

666. These terms being once well defined, will, I hope, in 
their use enable me to avoid much periphrasis and ambiguity of 
expression. I do not mean to press them into service more 
frequently than will be required, for I am fully aware that names 
are one thing and science another J. 

667. It will be well underssood that I am giving no opinion 
respecting the nature of the electric current now, beyond what 
I have done on former occasions (283. 517.); and that though 
1 speak of the current as proceeding from the parts which are 
positive to those which arc negative (663.), it is merely in ac- 
cordance with the conventional, though in some degree tacit, 
agreement entered into by scientific men, that they may have 
a constant, certain, and definite means of referring to the direc- 
tion of the forces of that current. 

iv. On some general conditions of electro-chemical 
Decomposition. 

669. From the period when electro-chemical decomposition 
was first effected to the present time, it has been a remark, that 
those elements which in the ordinary phenomena of chemical 
affinity, were the most directly opposed to each other, and com- 
bined with the greatest attractive force, were those which were 
the most readily evolved at the opposite extremities of the decom- 
posing bodies (549.) . 

670. If this result was evident when water was supposed to 
be essential to, and was present, in almost every case of such 

# apiwv that which goes up, (Neuter participle.) 

t Kariiov that which goes down 

t Since this paper was read, I have changed some of the terms which were 
first proposed, that 1 might employ only such as were at the same time simple 
in their nature, clear in their reference, and from hypothesis. 



199 


* Jan. 1834.] Electro-chemical decomposition . 

decomposition (472.), it is far more evident now that it has 
been shown and proved that water is not necessarily concerned 
in the phenomena (£74.), and that other bodies much surpass 
it in some of the effects supposed to be peculiar to that 
substance. 

671. Water^ from its constitution and the nature of its ele- 
ments, and from its frequent presence in cases of electrolytic 
action, Jias hitherto stood foremost in this respect. Though a 
compound formed by very powerful affinity, it yields up its ele- 
ments under the influence of a very feeble electric current; and 
it is doubtful whether a case of electrolyzation can occur, where, 
being present, it is not resolved into its first principles. 

672. The various oxides, chlorides, iodides, and salts, which 
I have shown are decomposable by the electric current when in 
the liquid state, under the same general law with water (102.), 
illustrate in an equally striking manner the activity, in such de- 
compositions, of elements directly and powerfully opposed to 
each other by their chemical relations. 

673. On the other hand, bodies dependent on w r cak affinities 
very rarely give way. Take, for instance, glasses : many of those 
formed of silica, lime, alkali, and oxide of lead, may be consi- 
dered as little more than solutions of substances one in another*. 
If bottle-glass be. fused, and subjected to the voltaic pile, it 
does not appear to be at all, decomposed (408.) If flint glass, 
which contains substances more directly opposed, be operated 
upon, it suffers some decomposition ; and if borate of lead glass, 
which is a definite chemical compound, be experimented with, 
it readily yields up its elements (408.) . 

674. But the result which is found to be so striking in the 
instances quoted is not at all borne out by reference to other 
cases where a similar consequence might have been expected. It 
may be said, that my own theory of electro * chemical decomposi- 
tion would lead to the expectation that all compound bodies 
should give way under the influence of the electric current with 
a facility proportionate to the strength of the affinity by which 
theiy .elements, either proximate or ultimate, are combined. I 
am not sure that that follows as a consequence of the theory ; 
but if the objection is supposed to be one presented by the facts, 
I have no doubt it will be removed when we obtain a more inti- 

* Philosophical Transactions, 1830, p. 49. 



200 Bodies capable of electrolyzation . [Series VII. 

mate acquaintance with, and precise idea of, the nature of che- 
mical affinity and the mode of action of an electric current over 
it (518. 524.) : besides which it is just as directly opposed to 
any other theory of electro-chemical decomposition as the one 
I have propounded ; for if it be admitted, as is generally the 
case, that the more directly bodies are opposed to each other in 
their attractive forces, the more powerfully do they combine, then 
the objection applies with equal force to any of the theories of 
electrolyzation which have been considered, and is an addition 
to those which I have taken against them. 

675 . Amongst powerful compouu ds which are not decomposed, 
boraoic acid stands prominent (408.). Then again, the iodide of 
sulphur, and the chlorides of sulphur, phosphorus, and carbon, 
are not decomposable under common circumstances, though 
their elements are of a nature which would lead to a contrary 
expectation. Chloride of antimony (402. 690.), the hydro- 
carbons, acetic acid, ammonia, and many other bodies undecom- 
posable by the voltaic pile, would seem to be formed by an 
affinity sufficiently strong to indicate that the elements were so 
far contrasted in their nature as to sanction the expectation that 
the pile would separate them, especially as in some cases of mere 
solution (530. 544.), where the affinity must by comparison be 
very weak, separation takes place*. 

676. It must not be forgotten, however, that much of this 
difficulty, and perhaps the whole, may depend upon the absence 
of conducting power, which, preventing the transmission of the 
current, prevents of course the effects due to it. All known com- 
pounds being non-conductors when solid, but conductors when 
liquid, are decomposed, with perhaps the single exception at pre- 
sent known of periodide of mercury (679. 691.) f; and even 
water itself, which so easily yields up its elements when the cur- 
rent passes, if rendered quite pure, scarcely suffers change, 
because it then becomes a very bad conductor. 

677. If it should hereafter be proved that the want of de- 
composition in those cases where, from chemical considerations, 
it might be so strongly expected (669. 672. 674,), is due to the 

* With regard to solution, I have met with some reasons for supposing that 
it will probably disappear as a cause of transference, and intend resuming the 
consideration at a convenient opportunitv. 

t See now, 1340, 1341. — Deo. 1838. 



201 


Jan. 1831?.] Proportions of elements in electrolytes . 

absence or deficiency of conducting power, it would also at the 
same time be proved that decomposition depends upon con- 
duction, and not the latfer upon the former (413.) ; and in water 
this seems to be very nearly decided. On the other hand, the 
conclusion is almost irresistible, that in electrolytes the power 
of transmitting the electricity across the substance is dependent 
upon their capability of suffering decomposition ; taking place 
only whilst they are decomposing, and being proportionate to 
the quantity of elements separated (821.). I may not, however, 
stop to discuss this point experimentally at present. 

678. When a compound contains such elements as are known 
to pass towards the opposite extremities of the voltaic pile, still 
the proportions in which they are present appear to be inti- 
mately connected with capability in the compound of suffering 
or resisting decomposition. Thus, the protochloride of tin 
readily conducts, and is decomposed (402.), but the perehloride 
neither conducts nor is decomposed (406.). The protiodide of 
tin is decomposed when fluid (402.) ; the periodide is not (405.). 
The periodide of mercury when fused is not decomposed (691.), 
even though it does conduct. I was unable to contrast it with 
the protiodide, the latter being converted into mercury and 
periodide by heat. 

679. These important differences induced me to look more 
closely to certain binary compounds, with a view' of ascertaining 
whether a law regulating the decomposability according to 
some relation of the proportionals or eqvivalents of the ele- 
ments, could be discovered. The proto compounds only, 
amongst those ju$t referred to, were decomposable ; and on re- 
ferring to the substances quoted to illustrate the force and gene- 
rality of the law of conduction and decomposition which I dis- 
covered (402.), it will be found that all the oxides, chlorides, 
and iodides subject to it, except the chloride of antimony and 
the periodide of mercury, (to which may now perhaps be added 
corrosive sublimate,) are also decomposable, whilst many per 
compounds of the same elements, not subject to the law, were 
not so (405. 406.), 

680. The substances which appeared to form the strongest 
exceptions tty this general result were such bodies as the sul- 
phuric, phosphoric, nitric, arsenic, and other acids. 

81. On experimenting with sulphuric acid, I found no rea- 



202 Electro-chemical decomposition. [Series VIJ. 

son to believe that it was by itself a conductor of, or decom- 
posable by, electricity, although I had previously been of that 
opinion (552,). When very strong it is h much worse conductor 
than if diluted*. If then subjected to the action of a powerful 
battery, oxygen appears at the anode , or positive electrode, al- 
though much is absorbed (728.), and hydrogen and sulphur ap- 
pear at the cathode , or negative electrode. Now the hydrogen has 
with me always been pure, not sulphuretted, and has been de- 
ficient in proportion to the sulphur present, so that it is evident 
that when decomposition occurred water must have been de* 
composed. I endeavoured to make the experiment with anhy- 
drous sulphuric acid ; and it appeared to me that, when fused, 
such acid was not a conductor, nor decomposed ; but I had not 
enough of the dry acid in my possession to allow me to decide 
the point satisfactorily. My belief is, that when sulphur appears 
during the action of the pile on sulphuric acid, it is the result 
of a secondary action, and that the acid itself is not eleetro- 
lyzablc (757.). 

682. Phosphoric acid is, I believe, also in the same condition ; 
but I have found it impossible to decide the point, because of 
the difficulty of operating on fused anhydrous phosphoric acid. 
Phosphoric acid which has once obtained water cannot be de- 
prived of it by heat alone. When heated, the hydrated acid 
volatilizes. Upon subjccting.phosphoric acid, fused upon the 
ring end of a wire (401.), to the action of the voltaic apparatus, 
it conducted, and was decomposed ; but gas, which I believe to 
be hydrogen, was always evolved at the negative electrode, and 
the wire was not affected as would have happened had phos- 
phorus been separated. Gas was also evolved at the positive 
electrode* From all the facts, I conclude it was, the water and 
not the acid which was decomposed. 

G83. Arsenic acid. This substance conducted, and was de- 
composed; but it contained water, and I was unable at the 
time to' press the investigation so as to ascertain whether a fusi- 
ble anhydrous arsenic acid could be obtained. It forms, there- 
fore, at present no exception to the general result. 

684. Nitrous* acid, obtained by distilling nitrate of lead, and 
keeping it in contact with strong sulphuric acid, was found to 
conduct and decompose slowly. But on examination there were 
* De la Hive, 



203 


Jan. 1834-.] Bodies not electrolyzable alone . 

strong reasons for believing that water was present, and that 
the decomposition and conduction depended upon it. I en- 
deavoured to prepare a* perfectly anhydrous portion, but could 
not spare the time required to procure an unexceptionable 
result. 

685. Nitric acid is a substance which I believe is not decom- 
posed directly by the electric current. As I want the facts in 
illustration of the distinction existing between primary and 
secondary decomposition, I will merely refer to them in this 
place (752.). 

686. That these mineral acids should confer facility of con- 
duction and decomposition on water, is no proof that they are 
competent to favour and suffer these actions in themsehes, 
Boracic acid does the same thing, though not decomposable. 
JV1. de la Rive has pointed out that chlorine has this power 
also ; but being to us an elementary substance, it cannot be due 
to its capability of suffering decomposition. 

687. Chloride of sulphur does not conduct, nor is it decom- 
posed, It consists of single proportionals of its elements, but 
is not on that account an exception to the rule (679.), which 
docs not affirm that all compounds of single proportionals of 
elements are decomposable, but that such as are decomposable 
are so constituted. 

688. Protochloride of photyhorus does not conduct nor 
become decomposed. 

689. Protochloride of carbon does not conduct nor suffer de- 
composition. In association with this substance, I submitted 
the hydro-chloride of carbon from olefiant gas and chlorine to 
the action of the electric current ; but it also refused to conduct 
or yield up its elements. 

690. With regard to the exceptions (679.), upon closer ex- 
amination, some of them disappear. Chloride of antimony (a 
compound of one proportional of antimony and one and a half 
of chlorine) of recent preparation was put into a tube (fig. 68.) 
(789.), and submitted when fused to the action of the current, 
the positive electrode being of plumbago. No electricity passed, 
and no appearance of decomposition was visible at first ; but 
when the -positive and negative electrodes were brought very 
near each other in the chloride, then a feeble action occurred 

.tf* a feeble current passed. The effect altogether was so 



204 Proportions in decomposable bodies. - [Series VII* 

small (although quite amenable to the law before given (394.) ), 
and so unlike the decomposition and conduction occurring in 
all the other cases, that I attribute it to the presence of a mi- 
nute quantity of water, (for which this and many other chlorides 
have strong attractions, producing hydrated chlorides,) or per- 
haps of a true protochloride consisting of single proportionals 
(695. 796.). 

691. Periodide of mercury being examined in the ssgxic man- 
ner, was found most distinctly to insulate whilst solid, but con- 
duct when fluid, according to the law of liquido-conduction 
(402.) but there was no appearance of decomposition. No 
iodine appeared at the anode y nor mercury or other substance 
at the cathode . The case is, therefore, no exception to the 
rule, that only compounds of single proportionals are decom- 
posable j but it is an exception, and I think the only one, to the 
statement, that all bodies subject to the law of liquido-con- 
duction are decomposable. I incline, however, to believe, that 
a portion of protiodide of mercury is retained dissolved in the 
periodide, and that to its slow decomposition the feeble con- 
ducting power is due. Periodide would be formed, as a se- 
condary result, at the anode ; and the mercury at the cathode 
would also form, as a secondary result, protiodide. Both these 
bodies would mingle with the fluid mass, and thus no final se- 
paration appear, notwithstanding the continued decomposition. 

692. When perchloride of mercury was subjected to the vol- 
taic current, it did not conduct in the solid state, but it did con- 
duct when fluid. I think, also, that in the latter case it was de- 
composed ; but there are many interfering circumstances which 
require examination before a positive conclusion can be drawn*. 

693. WfTen the ordinary protoxide of antimony is subjected 
to the voltaic current in a fused state, it alsg is decomposed, 
although the effect from other causes soon ceases (402. 801.). 
This oxide consists of one proportional of antimony and one 
and a half of oxygen, and is therefore an exception to the 
general law assumed. But in working with this oxide and the 
chloride, I observed facts which lead me to doubt whether the 
compounds usually called the protoxide and the protochloricte 
do not often contain other compounds, consisting of single* pro- 

* With regard to perchloride and periodide of mercury, see now 134CL 
T341.— Pec. 1838. 



Jan. 1834-.] Supposed new compounds of antimony. 205 

portions, which are the true proto compounds, and which, in 
the case of the oxide, might give rise to the decomposition 
above described. 

69d. The ordinary sulphuret of antimony is considered as 
being the compound with the smallest quantity of sulphur, and 
analogous in its proportions to the ordinary protoxide. But I 
find' that if it be fused with metallic antimony, a new sulphuret 
is formed.^ containing much more of the metal than the former, 
and separating distinctly, when fused, both from the pure 
metal on the one hand, and the ordinary gray sulphuret on. the 
other. In some rough experiments, the metal thus taken up 
by the ordinary sulphuret of antimony was equal to half the 
proportion of that previously in the sulphuret, in which case 
the new sulphuret would consist of single proportionals. 

695. When this new sulphuret was dissolved in muriatic acid, 
although a little antimony separated, yet it appeared to me that 
a true protocliloride, consisting of single proportionals, was 
formed, and from that, by alkalies, &e., a true protoxide, con- 
sisting also of single proportionals, was obtainable. But 1 could 
not stop to ascertain this matter strictly by analysis. 

696. I believe, however, that there is such an oxide ; that it 
is often present in variable proportions in what is commonly 
called protoxide, throwing uncertainty upon the results of its 
analysis, and causing the electrolytic decomposition above 
described *. 

697. Upon the whole, it appears probable that all those 
binary compounds of elementary bodies which are capable of 
being electrolyzed when fluid, but not whilst solid, according 
to the law of liquido- conduction (394.), consist of single pro- 
portionals of their elementary principles ; and it r\ ay be be- 
cause of their departure from this simplicity of composition, 
that boracic acicf, ammonia, perchlorides, periodides, and many 
other direct compounds of elements, are indecomposable. 

v 698. With regard to salts and combinations of compound 
bodies, the same sitnple relation does not appear to hold good. 
I could not decide this by bisulphates of the alkalies, for as long 

* In relation to this and the three preceding paragraphs, and also 801, see 
Berzelius's correction of the nature of the supposed new sulphuret and oxide, 
Phih'Mag. 18B6, vol. tiii. 476 : and for the probable explanation of the etfeets 
obtained with the protoxide, refer to 1340, 1341. — Dec. 1838. 



296 Influence of proportions in electrolytes . [Series VII. 

as the second proportion of acid remained, water was retained 
with it. The fused salts conducted, and were decomposed ; but 
hydrogen always appeared at the negative electrode. 

699. A biphosphate of soda was prepared by heating, and 
ultimately fusing, the ammonia-phosphate of soda. In this 
case the fused bisalt conducted, and was decomposed ; but a 
little gas appeared at the negative electrode ; and though I be- 
lieve the salt itself was electrolyzed, I am not quite satisfied that 
water was entirely absent. 

700. Then a biborate of soda was prepared ; and this, I 
' think, is an unobjectionable case. The salt, when fused, con- 
ducted, and was decomposed, and gas appeared at both elec- 
trodes : even when the boracic acid was increased to three 
proportionals, the same effect took place. 

701. Hence this class of compound combinations docs not 
seem to be subject to the same simple law as the former class 
of binary combinations. Whether we may find reason to con- 
sider them as mere solutions of the compound of single pro- 
portionals in the excess of acid, is a matter which, with some 
apparent exceptions occurring amongst the sulpliurets, must be 
left for decision by future examination. 

702. In any investigation of these points, great care must be 
taken to exclude water ; for if present, secondary effects are so 
frequently produced as often seemingly to indicate an electro- 
decomposition of substances, when no true result of the kind 
has occurred (742, &c.). 

703. It is evident that all the cases in which decomposition 
does not occur , may depend upon the want of conduction 
(677. 413.) ; but that does not at all lessen the interest excited 
by seeingNdie great difference of effect due to a change, not in 
the nature of the elements, but merely in their proportions ; 
especially in any attempt which may be made to elucidate and 
expound the beautiful theory put forth by Sir Humphry Davy*, 
and illustrated by Berzelius and other eminent philosophers, 

• that ordinary chemical affinity is a mere result of the electrical 
attractions of the particles of matter. 

If v. On a new Measurer of Volta-electricity . 

704. I have already said, when engaged in reducing common 

* Philosophical Transactions, 1807, pp. 32, 39; also 1826, pp, 387, 389.* 



207 


Jan. 1834.] Electro -chemical action is definite. 

and voltaic electricity to one standard of measurement (3 77.), 
and again when introducing my theory of electro-chemical de- 
composition (504. 505*510.), that the chemical decomposing 
action of a current is constant for a constant quantity of elec- 
tricity, notwithstanding the greatest variations in its sources, 
in its intensity, in the size of the electrodes used, in the nature 
of tlie conductors (or non conductors (307.) ) through which it 
is passed, or in* other circumstances. The conclusive proofs of 
the truth of these statements shall he given almost immediately 
(783, &c.). 

705. I endeavoured upon this law to construct an instrument 
which should measure out the electricity passing through it, 
and which, being interposed in the course of the current used 
in any particular experiment, should serve at pleasure, either as 
a comparative standard of effect, or as a positive measurer of 
this subtile agent. 

706. There is no substance better fitted, under ordinary cir- 
cumstances, to be the indicating body in such an instrument 
than water ; for it is decomposed with facility when rendered 
a better conductor by the addition of acids or salts ; its ele- 
ments may in numerous cases be obtained and collected with- 
out any embarrassment from secondary action, and, being 
gaseous, they are in the best physical condition for separation 
and measurement. Water, therefore, acidulated by sulphuric 
acid, is the substance 1 shall generally refer to, although it 
may become expedient in peculiar cases or forms of experiment 
to use other bodies (843.). 

707. The first precaution needful in the construction of the 
instrument was to avoid the recombination of the evolved gases, 
an effect which the positive electrode has been fo^md so ca- 
pable of producing (571.). For this purpose various forms of 
decomposing apparatus were used. The first consisted of 
straight tubes, each containing a plate and wire of platina 
soldered together by gold, and fixed hermetically in the glass 
at the closed extremity of the tube (Plate V. fig. 60.). The 
tubes were about eight inches long, 0*7 of an inch in diameter, 
and graduated. The platina plates were about an inch long, 
as wid,e as the tubes would permit, and adjusted as near to the 
mouths of the tubes as was consistent with the safe collection 
of flio gases evolved. In certain cases, where it was required 



208 


New measurer of voltaic electricity. [Series VII, 

to evolve tlie elements upon as small a surface as possible, the 
metallic extremity, instead of being a plate, consisted of the 
wire bent into the form of a ring (fig. 61.), When these tubes 
were used as measures, they were filled with the dilute sul- 
phuric acid, inverted in a basin of the same liquid (fig. 62.), 
and placed in an inclined position, with their mouths near to 
each other, that as little decomposing ‘matter should intervene 
as possible ; and also, in such a direction that the platina plates 
should be in vertical planes (720.). # 

708. Another form of apparatus is that delineated (fig. 63.). 
The tube is bent in the middle ; one end is closed ; in that end 
is fixed a wire and plate, a, proceeding so far downwards, that, 
when in the position figured, it shall be as near to the angle as 
possible, consistently with the collection, at the closed ex- 
tremity of the tube, of all the gas evolved against it. The 
plane of this plate is also perpendicular (720.). The other 
metallic termination, b , is introduced at the time decomposition 
is to be effected, being brought as near the angle as possible, 
without causing any gas to pass from it towards the closed end 
of the instrument. The gas evolved against it is allowed to 
escape. 

709. The third form of apparatus contains both electrodes 
in the same tube ; the transmission, therefore, of the electricity, 
and the consequent decomposition, is far more rapid than in the 
separate tubes. The resulting gas is the sum of the portions 
evolved at the two electrodes, and the instrument is better 
adapted than either of the former as a measurer of the quan- 
tity of voltaic electricity transmitted in ordinary eases. It con- 
sists of a straight tube (fig. 64.) closed at the upper extremity, 
and gracUtated, through the sides of which pass platina wires 
(being fused into the glass), which are connected with two 
plates within. The tube is fitted by grinding into one mouth 
of a double- necked bottle. If the latter be one half or two thirds 
full of the dilute sulphuric acid (706.), it will, upon inclination 
of the whole, flow into the tube and fill it. When an electric 
current is passed through the instrument, the gases evolved 
against the plates collect in the upper portion of the tube, and 
are not subject to the recombining power of the platina. 

710. Another form of the instrument is given at fig. 65. 

711. A fifth form is delineated (fig. 66.) . This I have iStand 



209 


3 an. 1834.] Definite action with varying electrodes. 

exceedingly useful in experiments continued in succession for 
days together, and where large quantities of indicating gas 
were to be collected. H; is fixed on a weighted foot, and has the 
form of a small retort containing the two electrodes : the neck 
is narrow, and sufficiently long to deliver gas issuing from it 
into a jar placed in a small pneumatic trough. The electrode 
chamber, sealed hermodcally at the part held in the stand, is 
five finches in length, and 0*6 of an inch in diameter ; the neck 
about nine inches in length, and 0*4 of an inch in diameter in- 
ternally. The figure will fully indicate the construction. 

712. Ii can hardly be requisite to remark, that in the arrange- 
ment of any of these forms of apparatus, they, and the wires 
connecting them with the substance, which is collaterally sub- 
jected to the action of the* same electric current, should be so far 
insulated as to ensure a certainty that all the electricity which 
passes through the one shall also be transmitted through the 
other. 

713. Next to the precaution of collecting the gases, if 
mingled, out of contact with the platinum, was the necessity 
of testing the law of a definite electrolytic action, upon water at 
least, under all varieties of condition ; that, with a conviction 
of its certainty, might also be obtained a knowledge of those 
interfering circumstances which would require to be practically 
guarded against. 

714. The first point investigated was the influence or indif- 
ference of extensive variations in the size of the electrodes, for 
which purpose instruments like those last described (709. 710. 
711.) were used. One of these had plates 0*7 of an inch wide, 
and nearly four inches long ; another had plates onlyjO‘5 of an 
inch wide, and 0*8 of an inch long ; a third had wires 0 02 of 
an inch in diameter, and three inches long ; and a fourth, similar 
wires only half an inch in length. Yet when these were filled with 
dilute sulphuric aeid, and, being placed in succession, had one 
common current of electricity passed through them, very nearly 
the same quantity of gas was evolved in all. The difference was 
sometimes in favour of one, and sometimes on the side of another; 
but the general result was that the largest quantity of gases was 
evqlvejf at the smallest electrodes, namely, those consisting 
merdy of platiha wires. 



210 Voltameter .* — definite decomposing action . [Series VII, 

715. Experiments of a similar kind were made with the single- 
plate, straight tubes (707.), and also with the curved tubes 
(708.), with similar consequences; and when these, with the 
former tubes, were arranged together in various ways, the re- 
sult, as to the equality of action of large and small metallic sur- 
faces when delivering and receiving the same current of electri- 
city, was constantly the same. As an illustration, the following 
numbers are given. An instrument with two wires evolved 
74*3 volumes of mixed gases ; another with plates 7325 volumes; 
whilst the sum of the oxygen and hydrogen in two separate tubes 
amounted to 73*65 volumes. In another experiment the volumes 
were 55*3, 55*3, and 54*4. 

716. But it was observed in these experiments, that in single- 
plate tubes (707.) more hydrogen was* evolved at the negative 
electrode than was proportionate to the oxygen at the positive 
electrode ; and generally, also, more than was proportionate to 
the oxygen and hydrogen in a double plate- tube. Upon more 
minutely examining these effects, I was led to refer them, and 
also the differences between wires and plates (714.), to the solu- 
bility of the gases evolved, especially at the positive electrode. 

717. When the positive and negative electrodes are equal in 
surface, the bubbles which rise from them in dilute sulphuric 
acid are always different in character. Those from the positive 
plate are exceedingly small, aqd separate instantly from every 
part of the surface of the metal, in consequence of its perfect 
cleanliness (633.) ; whilst in the liquid they give it a hazy ap- 
pearance, from their number and minuteness ; are easily carried 
down by currents ; and therefore not only present far greater 
surface of contact with the liquid than larger bubbles would do, 
but are Mtained a much longer time in mixture with it. But 
the bubbles at the negative surface, though they constitute twice 
the volume of the gas at the positive electrode, are nevertheless 
very inferior in number. They do not rise so universally from 
every part of the surface, but seemed to be evolved at different 
points ; and though so much larger, they appear to cling to the 
metal, separating with difficulty from it, and when separated, 
instantly rising to the top of the liquid. If, therefore, oxygen 
and hydrogen ^had equal solubility in, or powers of combining 
with, water under similar circumstances, still under the Wesent 
conditions the oxygen would be far the most Kable to solution ; 



Variation of the electrodes. 


211 


Jan. 1834.] 


but when to thesels added its well-known power of forming a 
compound with water, it is no longer surprising that such a 
compound should be produced in small quantities at the positive 
electrode ; and indeed the bleaching power which some philo- 
sophers have observed in a solution at this electrode, when 
chlorine and similar bodies have been carefully excluded, is 
probably due to the formation there, in this manner, of oxy- 
water, 

718. Tlfat more gas was collected from the wires than from 
the plates, I attribute to the circumstance, that as equal quan- 
tities were evolved in equal times, the bubbles at the wires 
having been more rapidly produced, in relation to any part of 
the surface, must have been much larger ; have been therefore 
in contact with the fluid by a much smaller surface, and for a 
much shorter time than those at the plates ; hence less solution 
and a greater amount collected. 

719. There was also another effect produced, especially by 
the use of large electrodes, which was both a consequence and 
a proof of the solution of part of the gas evolved there. The 
collected gas, when examined, was found to contain small por- 
tions of nitrogen. This I attribute to the presence of air dis- 
solved in the acid used for decomposition. It is a well-known 
fact, that when bubbles of a gas but slightly soluble in water or 
solutions pass through them, the portion of this gas which is 
dissolved displaces a portion of that previously in union with 
the liquid : and so, in the decompositions under consideration, 
as the oxygen dissolves, it displaces a part of the air, or at 
least of the nitrogen, previously united to the acid ; and this 
effect takes place most extensively with large plates, because 
the gas evolved at them is in the most favourable condition for 
solution. 

720. With the intention of avoiding this solubility of the gases 
as much as possible, I arranged the decomposing plates in a 
vertical position (707. 708.), that the bubbles might quickly 
escape upwards, and that the downward currents in the fluid 
should not meet ascending currents of gas. This precaution I 
found to assist greatly in producing constant results, and espe- 
cially in experiments to be hereafter referred to, in which other 
liquid^ than dilute sulphuric acid, as for instance solution of 
potash, were used. 

p'2 



,212 Voltameter : — definite action* [Series VII. 

721. The irregularities in the indications of the measurer 
proposed, arising from the solubility just referred to, are but 
small, and may be very nearly corrected b^ comparing the results 
of two or three experiments. They may also be almost entirely 
avoided by selecting that solution which is found to favour them 
in the least degree (728.) ; and still further by collecting the 
hydrogen only, and using that as the indicating gas ; for being 
much less soluble than oxygen, being evolved with twice the 
rapidity and in larger bubbles (717.), it can be collected more 
perfectly and in greater purity. 

722. From the foregoing and many other experiments, it re- 
sults that variation in the size of the electrodes causes no varia- 
tion in the chemical action of a given quantity of electricity upon 
water. 

723. The next point in regard to which the principle of con- 
stant electro- chemical action was tested, was variation of inten- 
sity. In the first place, the preceding experiments were re- 
peated, using batteries of an equal number of plates, strongly 
and weakly charged ; but the results were alike. They were 
then repeated, using batteries sometimes containing forty, and 
at other times only five pairs of plates; but the results were 
still the same. Variations therefore in the intensity , caused by 
difference in the strength of charge, or in the number of alter- 
nations used, produced no difference as to the equal qction of 
large and small electrodes . 

724. Still these results did not prove that variation in the 
intensity of the current was not accompanied by a corresponding 
variation in the electro-chemical effects, since the actions at ail 
the surfa^gs might have increased or diminished together. The 
deficiency in the evidence is, however, completely supplied by 
the former experiments on different-sized electrodes ; for with 
variation in the size of these, a variation in the intensity must 
haye occurred. The intensity of an electric current traversing 
conductors alike in their nature, quality, and length, is probably 
as the quantity of electricity passing through a given sectional 
area perpendicular to the current, divided by the time (360. 
note) and therefore when 'large plates were contrasted with 
wires separated by an equal length of the same ' decontoosing 
conductor (714.), whilst one current of electricity passed thrbugh 



Jan. 1834.] 


Variations of the current . 


213 


both arrangements, that electricity must have been in a very 
different state, as to tension, between the plates and between 
the wires ; yet the chemical results were the same. 

725. The difference in intensity, under the circumstances 
described, may be easily shown practically, by arranging two 
decomposing apparatuses in fig. 67, where the same fluid is sub- 
jected to the decomposing power of the same current of electri- 
city, passing in the vessel A. between large platina plates, and in 
the vessel B. between small wires. If a third decomposing appa- 
ratus, such as that delineated fig. 66. (711.), be connected with 
the wires at «, h , fig. 67, it will serve sufficiently well, by the 
degree of decomposition occurring in it, to indicate the relative 
state of the two plates a* to intensity > and if it then be applied 
in the same way, as a test of the state of the wires at a' b 1 , it 
will, by the increase of decomposition within, show how much 
greater the intensity is there than at the former points. The 
connexions of P and N with the voltaic battery arc of course to 
be continued during the whole time. 

726. A third form of experiment in which difference of inten- 
sity was obtained, for the purpose of testing the principle of equal 
chemical action, was to arrange three volta-electrometers, so that 
after the electric current had passed through one, it should divide 
into two parts, each of which should traverse one of the remain- 
ing instruments, and should then reunite. The sum of the 
decomposition in the two latter vessels was always equal to the 
decomposition in the former vessel. But the intensity of the 
divided current could not be the same as that it had in its origi- 
nal state ; and ‘therefore variation of intensity has no influence 
on the results if the quantity of electricity remain the same . 
The experiment, in fact, resolves itself simply into dn increase 
in the size of the electrodes (725.). 


727. The third point , in respect to which the principle of 
equal electro-chemical action on water w as tested, was variation 
of the strength of the solution used. In order to render the water 
a conductor, sulphuric acid had been added to it (707.) ; and it 
did not seem unlikely that this substance, with many others, 
might render the water more subject to decomposition, the 
electricity remaining the same in quantity. But such did not 



214 Voltameter ; — change of th$ solution . [Series VII. 

prove to be the case. Diluted sulphuric acid, o£ different 
strengths, was introduced into different Recomposing apparatus, 
and submitted simultaneously to the action of the same electric 
current (714.) . Slight differences occurred, as before, sometimes 
in one direction, sometimes in another ; but the final result was, 
that exactly the same quantity of water, was decomposed in all 
the solutions by the same quantity of electricity , though the 
sulphuric acid in some was seventy-fold what it was r in others. 
The strengths 'used were of specific gravity 1*495, and down- 
wards. 

728. When an acid having a specific gravity of about 1*336 
was employed, the results were most uniform, and the oxygen 
and hydrogen (716.) most constantly in the right proportion to 
each other. Such an acid gave more gas than one much weaker 
acted upon by the same current, apparently because it had less 
solvent power. If the acid were very strpng, then a remark- 
able disappearance of oxygen took place ; thus, one made by 
mixing two measures of strong oil of vitriol with one of water, 
gave forty-two volumes of hydrogen, but only twelve of oxygen. 
The hydrogen was very nearly the same with that evolved from 
acid of the specific gravity 1*232. I have not yet had time to 
examine minutely the circumstances attending the disappear- 
ance of the oxygen in this case, but imagine it is due to the 
formation of oxy water, which Thenard has shown is favoured 
by the presence of acid. 

729. Although not necessary for the practical use of the 
instrument I am describing, yet as connected with the import- 
ant point of constant electro-chemical action upon water, I now 
investigate the effects produced by an electric current passing 
through aqueous solutions of acids, salts, and compounds, ex- 
ceedingly different from each other in their nature, and found 
them to yield astonishingly uniform results. But many of them 
which are connected with a secondary action will be more use- 
fully described hereafter (778.). 

730. When solutions of caustic potassa or soda, or sulphate 
of magnesia, or sulphate of soda, were acted upon by the elec- 
tric current, just as much oxygen and hydrogen was evolved 
from them as from the diluted sulphuric acid, with which they 
were compared. When a solution of ammonia, rendered a better 



215 


Jan. 1834.] Definite electrolyzation of water . 

conductor by sulphate of ammonia (554.), or a solution of sub- 
carbonate of potassa was experimented with, the hydrogen evolved 
was in the same quantity as that set free from the diluted sul- 
phuric acid with which they were compared. Hence changes 
in the nature of the solution do not alter the constancy of electro- 
lytic action upon water . 

731. I have already said, respecting large and small elec- 
trodes, thg-t change of order caused no change in the general 
effect (715.). The same was the case with different solutions, 
or with different intensities ; and however the circumstances of 
an experiment might be varied, the results came forth exceed- 
ingly consistent, and proved that the electro-chemical action was 
still the same. 

732. I consider the foregoing investigation as sufficient to 
prove the very extraordinary and important principle with 
respect to water, that when subjected to the influence of the 
electric current , a quantity of it is decomposed exactly propor- 
tionate to the quantity of electricity which has passed , notwith- 
standing the thousand variations in the conditions and circum- 
stances under which it may at the time be placed ; and further, 
that when the interference of certain secondary effects (742. &c.), 
together with the solution or recombination of the gas and the 
evolution of air, are guarded against, the products of the decom- 
position may be collected with such accuracy , as to afford a very 
excellent and valuable measurer of the electricity concerned in 
their evolution . 

733. The forms of instrument which I have given, figg. 64, 
65, 66 (709. 710. 711.), are probably- those which will be 
found most useful, as they indicate the quantity pf* electricity, 
by the largest volume of gases, and cause the least obstruction 
to the passage of the current. The fluid which my present 
experience leads me to prefer, is a solution of sulphuric acid 
of specific gravity about 1*336, or from that to 1*25 , but it is 
very essential that there should be no organic substance, nor 
any vegetable acid, nor other body, which, by being liable to 
the action of the oxygen or hydrogen evolved at the electrodes 
(773. &c.), shall diminish their quantity, or add other gases to 
them. 

734. In many cases when the instrument is used as a com- 



210 General forms of the voltameter . [Series VII. 

parative standard , or even as a measurer , it may be desirable 
to collect the hydrogen only, as being less liable to absorption 
or disappearance in other ways than thd oxygen ; whilst at the 
same time its volume is so large, as to render it a good and 
sensible indicator. In such cases the first and second form of 
apparatus have been used, figg. 62, 63 (707. 708.). The in- 
dications obtained were very constant, the variations being 
much smaller than in those forms of apparatus collecting both 
gases ; and they can also be procured when solutions are used 
in comparative experiments, which, yielding no oxygen or only 
secondary results of its action, can give no indications if the 
educts at both electrodes be collected. Such is the case when 
solutions of ammonia, muriatic acid, chlorides, iodides, acetates 
or other vegetable salts, &c., are employed. 

735. In a few cases, as where solutions of metallic salts liable 
to reduction at the negative electrode are acted upon, the 
oxygen may be advantageously used as the measuring sub- 
stance. This is the case, for instance, with sulphate of 
copper. 

736. There are therefore two general forms of the instru- 
ment which I submit as a measurer of electricity; one, in 
which both the gases of the water decomposed are collected 
(709. 710. 711.); and the other, in which a single gas, as the 
hydrogen only, is used (707. 708.). When referred to as a 
comparative instrument , (a use I shall now make of it very ex- 
tensively,) it will not often require particular precaution in the 
observation ; but when used as an absolute measurer , it will be 
needful that the barometric pressure and the temperature be 
taken into account, and that thp graduation of the instruments 
should b^ JJo one scale : the hundredths and smaller divisions 
of a cubical inch are quite fit for this purpose, and the hun- 
dredth may be very conveniently taken as indicating a degree 
of electricity. 

73 7. It can scarcely be needful to point out further than has 
been done how this instrument is to be used. It is to be in- 
troduced into the course of the electric current, the action of 
which is to be exerted anywhere else, and. if 60° or 70° of elec- 
tricity are to be measured out, either in one or several portions, 
the current, whether strong or weak, is to be ' continued 
until the gas in the tube occupies that number of divisions or 



Use of the voltameter . 


217 


Jan* 1334.] 


hundredths of a cubical inch. Or if a quantity competent to 
produce a certain effect is to be measured, the effect is to be 
obtained, and then the indication read off. In exact experi- 
ments it is necessary to correct the volume of gas for changes 
in temperature and pressure, and especially for moistuie*. 
For the latter object the volta-eleetrometcr (fig. 66.) is most 
accurate, as its gas can be measured over water, whilst the 
others regain it over acid or saline solutions. 

738. I have not hesitated to apply the term degree (736), in 
analogy with the use made of it with respect to another most 
important imponderable agent, namely, heat ; and as the de- 
finite expansion of air, water, mercury, &c., is there made use 
of- to measure heat, so the equally definite evolution of gases is 
here turned to a similar use for electricity. 

739. The instrument offers the only actual measurer of vol- 
taic electricity which we at present possess. For without being 
at all affected by variations in time or intensity, or alterations 
in the current itself, of any kind, or from any cause, or even of 
intermissions of action, it takes note with accuracy of the 
quantity of electricity which has passed through it, and reveals 
that quantity by inspection ; I have therefore named it a volta- 

ELECTKOMETER. 

740. Another mode of measuring volta- electricity may be 
adopted with advantage in many cases, dependent on the quan- 
tities of metals or other substances evolved either as primary 
or as secondary results ; but I refrain from enlarging on this 
use of the products, until the principles on which their con- 
stancy depends have been fully established (791. 843.). 

741. By the aid of this instrument I have been able to esta- 
blish the definite character of electro-chemical action in it% 
most general sense ; and I am persuaded it will become of the 
utmost use in the extensions of the science which these views 
afford. I do not pretend to have made its detail perfect, but 
to have demonstrated the truth of .the principle, and the utility 
of the applicationf. 

* For a simple table of correction for moisture, I may take the liberty of 
referring to tny Chemical Manipulation, edition of 1830, p. 370. 

t As early as the year 1811, Messrs. Gay Lussac, and Th^nard, employed 
chetr/ieal decomposition as a, measure of the electricity of the voltaic pile. See 
JZecherckes PhysteQ^chymiqiies, p. 12. The principles and precautions by which 
it becomes an exact measure were of course not then known. — Dec. 1838. 



218 Results of electrolyzation. [Series VII. 

T vi. On the primary or secondary character of the bodies 
evolved at the Electrodes. 

742. Before the volta-electrometer could be employed in de- 
termining, as a general law , the constancy of electro -decom- 
position, it became necessary to examine a distinction, already 
recognised among scientific men, relative to the products of 
that action, namely, their primary or secondary character; 
and, if possible, by some general rule or principle, to decide 
when they were of the one or the other kind. It will appear 
hereafter that great mistakes respecting electro-chemical action 
and its consequences have arisen from confounding these two 
classes of results together. 

743. When a substance under decomposition yields at the 
electrodes those bodies uncombined and unaltered which the 
electric current has separated, then they may be considered as 
primary results, even though themselves compounds. Thus 
the oxygen and hydrogen from water are primary results ; and 
so also are the acid and alkali (themselves compound bodies) 
evolved from sulphate of soda. But when the substances 
separated by the current are changed at the electrodes before 
their appearance, then they give rise to secondary results, 
although in many cases the bodies evolved are elementary. 

744. These secondary results occur in two ways, being some- 
times due to the mutual action of the evolved substance and 
the matter of the electrode, and sometimes to its action upon 
the substances contained in the body itself under decomposition. 
Thus, when carbon is made the positive electrode in dilute sul- 
phuric acid, carbonic oxide and carbonic acid occasionally ap- 
pear there instead of oxygen ; for the latter, acting upon the 
matter of the electrode, produces these secondary results. Or if 
the positive electrode, in a solution of nitrate or acetate of lead, 
be platina, then peroxide of lead appears there, equally a 
secondary result with the former, but now depending upon an 
action of the oxygen on a substance in the solution. Again, 
when ammonia is decomposed by platina electrodes, nitrogen 
appears at the anode * ; but though an elementary body, it is a 
secondary result in this case, being derived from the chemical 
action of the oxygen electrically evolved there, upon thd am- 

♦ Annales de Chimie, 1804, tom. li. p. 187, 



219 


Jan. 1834.] Primary or secondary results. 

monia in the surrounding solution (554.) . In the same manner 
when aqueous solutions of metallic salts are decomposed by the 
current, the metals evolved at the cathode , though elements, 
are always secondary results, and not immediate consequences 
of the decomposing power of the electric Current. 

.745. Many of these secondary results are extremely valu- 
able ; for instance, all the interesting compounds which M. Bee- 
querel h^ obtained by feeble electric currents are of this 
nature; but they are essentially chemical, and must, in the 
theory of electrolytic action, be carefully distinguished- from 
those which are directly due to the action of the electric current. 

746. The nature of the substances evolved will often lead to a 
correct judgment of thejr primary or secondary character, but 
is not sufficient alone to establish that point. Thus, nitrogen 
is said to be attracted sometimes by the positive and sometimes 
by the negative electrode, according to the bodies with which 
it may be combined (554. 555.), and it is on such occasions 
evidently viewed as a primary result* ; but I think I shall show, 
that, when it appears at the positive electrode, or rather at the 
anode } it is a secondary result (748.). Thus, also. Sir Hum- 
phry Davyf, and with him the great body of chemical philo- 
sophers, (including myself,) have given the appearance of cop- 
per, lead, tin, silver, gold, &c., at the negative electrode, when 
their aqueous solutions were acted upon by the voltaic current, 
as proofs that the metals, as a class, were attracted to that 
surface ; thus assuming the metal, in each case, to be a pri- 
mary result. These, however, I expect to prove, are all 
secondary results ; the mere consequence of chemical action, 
and no proofs either of the attraction of the law announced 
respecting their places J. 

747. But when we take to our assistance the law of constant 
electro-chemical action already proved with regard to water 
(732.), and which I hope to extend satisfactorily to all bodies 

* Annaies de Chimie, 1804, tom.li. p..l72. 

t Elements of Chemical Philosophy, pp, 144, 161. 

% It is remarkable that up to 4804 it was the received opinion that the 
metals were reduced by the nascent hydrogen. At that date the general opi- 
nion was reversed by Hisinger and Berzelius (Annales de Chimie, 1804, tom. 
li. p. 174.), who stated that the metals were evolved directly by the electricity : 
in which opinion It appears, from that^tiine, Davy coincided (Philosophical 
Transactions, 1826, p, 888.). 



220 


Secondary results with ammonia . [Series YU. 

(821.), and consider the quantities as well as the nature of the 
substances set free, a generally accurate judgment of the pri- 
mary or secondary character of the results may be formed : 
and this important point, so essential to the theory of electro- 
lyzation, since it decides what are the particles directly under the 
influence of the current, (distinguishing them from such as are 
not affected), and what are the results to be expected, may be 
established with such degree of certainty as to removp innume- 
rable ambiguities and doubtful considerations from this branch 
of the science. 

748. Let us apply these principles to the case of ammonia, 
and the supposed determination of nitrogen to one or the other 
electrode (554. 555.). A pure strong solution of ammonia is as 
bad a conductor, and therefore as little liable to electrolyzation, 
as pure water ; but when sulphate of ammonia is dissolved in it, 
the whole becomes a conductor j nitrogen almost and- occasion- 
ally quite pure is evolved at the anode , and hj'drogen at the 
cathode ; the ratio of the volume of the former to that of the 
latter varying, but being as 1 to about 3 or 4. This result 
would seem at first to imply that the electric current had de- 
composed ammonia, and that the nitrogen had been determined 
towards the positive electrode. But when the electricity- used 
was measured out by the volt a- electrometer (707. 736.), it was 
found that the hydrogen obtained was exactly in the proportion 
which would have been supplied by decomposed water, whilst 
the nitrogen had no certain or constant relation whatever. 
When, upon multiplying experiments, it was found that, by 
using a stronger or weaker solution, or a more or less powerful 
battery, the gas evolved at the anode was a mixture of oxygen 
and ni^™oge*v varying both in proportion and absolute quantity, 
whilst the hydrogen at the cathode remained constant, no doubt 
could be entertained that the nitrogen at the anode was a second- 
ary result, depending upon the chemical action of the nascent 
oxygen, determined to that surface by the electric current, upon 
the ammonia in solution. It was the water, therefore, which 
was electrolyzed, not the ammonia. Further, the experiment 
gives no real indication of the tendency of the element nitrogen 
to either one electrode or the other ; nor do I know of any ex- 
periment with nitric acid, or other compounds of nitrogen, 
which shows the tendency of this element, under the influence 



221 


Jan* 1834.] Secondary results with acetates. 

of the electric current, to pass in either direction along its 
course. 

749. As another illustration of secondary results, the effects 
on a solution of acetate of potassa may be quoted. When a 
very strong solution was used, more gas was evolved at the 
anode than at the cathode , in the proportion of 4 to 3 nearly : 
that from the anode Was a mixture of carbonic oxide and car- 
bonic acid ; that from the cathode pui*e hydrogen. When a 
much weaker solution was used, less gas was evolved at the 
anode than at the cathode ; and it now contained carburetted 
hydrogen, as well as carbonic oxide and carbonic acid. This 
result of carburetted hydrogen at the positive, electrode has a 
very anomalous appearance, if considered as an immediate con- 
sequence of the decom]fosing power of the current. It, how- 
ever, as well as the carbonic oxide and acid, is only a secondary 
result ; for it is the water alone which suffers electro-decompo- 
sition, and it is the oxygen eliminated at the anode which, re- 
acting on the acetic acid, in the midst of which it is evolved, 
produces those substances that finally appear there. This is 
fully proved by experiments with the volta-eleotromctcr (707.) ; 
for then the hydrogen evolved from the acetate at the cathode 
is always found to be definite, being exactly proportionate to 
the electricity which has passed through the solution, and, in 
quantity, the same as the hydrogen evolved in the volta-clec- 
trometer itself. The appearance of the carbon in combination 
with the hydrogen at the positive electrode, and its non-ap- 
pearance at the negative electrode, are in curious contrast with 
the results which might have been expected from the law 
usually accepted respecting the final places of the elements. 

750. If the salt in solution be an acetate of lead., then the 
results at both electrodes are secondary, and cannot be used to 
estimate or express, the amount of electro-chemical action, ex- 
cept by a circuitous process (843.). In place of oxygen or even 
the gases already described (749.), peroxide of lead now ap- 
pears at the positive, and lead itself at the negative electrode. 
WJien other metallic solutions are used, .containing, for instance, 
peroxides, as that of copper, combined with this or any other 
decomposable acid, still more complicated results will be ob- 
tained ; which, viewed as direct results of the electro- chemical 



222 


Secondary results with nitric acid. [Series VII. 

action, will, in their proportions, present nothing but confusion, 
but will appear perfectly harmonious and simple if they be con- 
sidered as secondary results, and will accord in their propor- 
tions with the oxygen and hydrogen evolved from water by the 
action of a definite quantity of electricity. 

751. I have experimented upon many bodies, -with a view to 
determine whether the results were primary or secondary. I 
have been surprised to find how many of them, in ordinary 
cases, are of the latter class, and how frequently water is the 
only body electrolyzed in instances where Qther substances have 
been supposed to give way. Some of these results I will give 
in as few words as possible. 

752. Nitric acid . — When very strong, it conducted well, and 
yielded oxygen at the positive electrode. No gas appeared at 
the negative electrode ; but nitrous acid, and apparently nitric 
oxide, were formed there, which, dissolving, rendered the acid 
yellow or red, and at last even effervescent, from the spontaneous 
separation of nitric oxide. Upon diluting the acid with its bulk 
or more of water, gas appeared at the negative electrode. Its 
quantity could be varied by variations, either in the strength of 
the acid or of the voltaic current : for that acid from which no 
gas separated at the cathode , with a weak voltaic battery, did 
evolve gas there with a stronger ; and that battery which 
evolved no gas there with a strong acid, did cause its evolution 
with an acid more dilute. The gas at the anode was always 
oxygen ; that at the cathode hydrogen. When the quantity of 
products was examined by the volta-electrometer (707.), the 
oxygen, whether from strong or weak acid, proved to be in the 
same proportion as from water. When the acid was diluted 
to specific* gravity 1*24, or less, the hydrogen also proved to be 
the same in quantity as from water. Hence I conclude that 
the nitric acid does not undergo electrolyzation, but the water 
only ; that the oxygen at the anode is always a primary result, 
but that the products at the cathode are often secondary, and 
due to the reaction of the hydrogen upon the nitric acid. 

753. Nitre . — A solution of this salt yields very variable re- 
sults, according as one or other form of tube is used, or as the 
electrodes are large or small. Sometimes the whole of the hy- 
drogen of the water decomposed may be obtained at the nega- 



223 


Jan. 1834.] Sulphurous and sulphuric acids. 

tive electrode; at other times, only a part of it, because of the 
ready formation of secondary results. The solution is a very 
excellent conductor of electricity. 

754. Nitrate of ammonia > in aqueous solution, gives rise to 
secondary results very varied and uncertain in their propor- 
tions. 

755. Sulphurous acid . — Pure liquid sulphurous acid does 
not conduct nor suffer decomposition by the voltaic current*, 
but, wheif dissolved in water, the solution acquires conducting 
power, and is decomposed, yielding oxygen at the anode y and 
hydrogen and sulphur at the cathode . 

756. A solution containing sulphuric acid in addition to the 
sulphurous acid, was a better conductor. It gave very little 
gas at either electrode : that at the anode was oxygen, that at 
the cathode pure hydrogen. From the cathode also rose a 
white turbid stream, consisting of diffused sulphur, which soon 
rendered the whole solution milky. The volumes of gases were 
in no regular proportion to the quantities evolved from water 
in the voltameter. I conclude that the sulphurous acid was not 
at all affected by the electric current in any of these cases, and 
that the water present was the only body electro- chemically 
decomposed; that, at the anode , the oxygen from the water 
converted the sulphurous acid into sulphuric acid, and, at the 
cathode , the hydrogen electrically evolved decomposed the sul- 
phurous acid, combining with its oxygen, and setting its sul- 
phur free. I conclude that the sulphur at the negative elec- 
trode was only a secondary result ; and, in fact, no part of it 
was ^found combined with the small portion of hydrogen which 
escaped when weak solutions of sulphurous acid were used. 

757. Sulphuric acid . — I have already given my reasons for 
concluding that sulphuric acid is not electrolyzable, i. e. not 
decomposable directly by the electric current, but occasionally 
suffering by a secondary action at the cathode from the hydro- 
gen evolved there (681.). In the year 1800, Davy considered 
the sulphur from sulphuric acid as the result of the action of the 
nascent hydrogenf. In 1804, Hisinger and Berzelius stated 

* See also De la Rive, Biblioth&que Universelle, tom. xl. p. 205 ; or 
Quarterly Journal of Science, vol. xxvii. p. 407. 

t Nicholson’s Quarterly Journal, vol. iv. pp. 280, 281. 



224 Electrolyzation of muriatic acid. [Series VII. 

that it was the direct result of the action of the voltaic pile*, 
an opinion which from that time Davy seems to have adopted, 
and which has since been commonly received by' all. The 
change of my own opinion requires that I should correct what 
I have already said of the decomposition of sulphuric acid in a 
former series of these Researches (552.) : I do not now think 
that the appearance of the sulphur at the negative electrode is 
an immediate consequence of electrolytic action.* 

7 58. Muriatic acid. — A strong solution gave hydrogen at 
the negative electrode, and chlorine only at the positive elec- 
trode ; of the latter, a part acted on the platina and a part was 
dissolved. A minute bubble of gfts remained ; it was not oxy- 
gen, but probably air previously held in solution. 

759. It was an important matter tef determine whether the 
chlorine was a primary result, or only a secondary product, due 
to the action of the oxygen evolved from water at the anode 
upon the muriatic acid ; i. e. whether the muriatic acid was 
electrolyzable, and if so, whether the decomposition was 
definite. 

760. The muriatic acid was gradually diluted. One part 
with six of water gave only chlorine at the anode . One part 
with eight of water’gave only chlorine ; with nine of water, a 
little oxygen appeared with the chlorine : but the occurrence or 
non-occurrence of oxygen at thpse strengths depended, in part, 
on the strength of the voltaic battery used. With fifteen parts 
of water, a little oxygen, with much chlorine, was evolved at the 
anode . As the solution was now becoming a bad conductor of 
electricity, sulphuric acid was added to it : this caused piore 
ready decomposition, but did not sensibly alter the proportion 
of chlorine ajad oxygen. 

761. The muriatic acid was now diluted with 100 times its 
volume of dilute sulphuric acid. It still gave a large propor- 
tion of chlorine at the anode , mingled with oxygen ; and the re- 
sult ^was the same, whether a voltaic battery of 40 pairs of plates 
or one containing only 5 pairs were used. With acid of this 
strength, the oxygen evolved at the anode was to the hydrogen 
at the cathode , in volume, as 17 is to 64; and therefore* the 
chlorine would have been 30 volumes, had it not been dissolved 
by the fluid. 

* Annales de Chimfe, 1804, tom. li. p. 173. 



Jan. 1834.] Primary or secondary decomposition . 225 

762. Next with respect to the quantity of elements evolved. 
On using the volta-electrometer, it was found that, whether the 
strongest or the weakesfcmuriatie acid were used, whether chlo- 
rine alone or chlorine mingled with oxygen appeared at the 
anode , still the hydrogen evolved at the cathode was a constant 
quantity, i. e. exactly the same as the hydrogen which the same 
quantity of electricity could evolve from water. 

763. This constancy does not decide whether the muriatic 
acid is electrolyzed or not, although it proves that if so, it must 
be in definite proportions to the quantity of electricity used. 
Other considerations may, however, be allowed to decide the 
point. The analogy between chlorine and oxygen, in their 
relations to hydrogen, is so strong, as to lead almost to the cer- 
tainty, that, when combir^d with that element, they would per- 
form similar parts in the process of electro-decomposition. 
They both unite with it in single proportional or equivalent 
quantities ; and the number of proportionals appearing to have 
an intimate and important relation to the deeomposability of a 
body (697.), those in muriatic acid, as well as in water are the 
most favourable, or those perhaps even necessary, to decompo- 
sition. 1 In other binary compounds of chlorine also, where 
nothing equivocal depending on the simultaneous presence of it 
and oxygen is involved, the chlorine is directly eliminated at the 
anode by the electric current. Such is the case with the chlo- 
ride of lead (395.), which may be justly compared with protoxide 
of lead (402.), and stands in the same relation to it as muriatic 
acid to water. The chlorides of potassium, sodium, barium, 
&c., are in the same relation to the protoxides of the same 
metals and present the same results under the influence of the 
electric current (402.). 

764. From all the experiments, combined with" these con- 
siderations, I conclude that muriatic acid is decomposed by the 
direct influence of the electric current, and that the quantities 
evolved are, and therefore the chemical action is, definite for a 
definite quantity of electricity . For* though I have not col- 
lected jand measured the chlorine, in its separate state, at the 
anode , -there can exist no doubt as to its being proportional to 
the hydrogen at the cathode : and the results arc therefore suf- 
ficient to establish the general law of constant electro -chemical 
action in the case of muriatic acid. 

Q 



226 ‘Primary or secondary decomposition. [Series VII. 

765. In the dilute acid (761.), I conclude that a part of the 
water is electro-chemically decomposed, giving origin to the 
oxygen, which appears mingled with the chlorine at the anode . 
The oxygen may he viewed as a secondary result ; hut I incline 
to hclieve that it is not so : for, if it were, it might he expected 
in largest proportion from the stronger acid, whereas the re- 
verse is the fact. This consideration, with others, also leads 
me to conclude that muriatic acid is more easily decomposed 
hy the electric current than water ; since, even when diluted 
with eight or nine times its quantity of the latter fluid, it alone 
gives w r ay, the water remaining unaffected. 

766. Chlorides. — On using solutions of chlorides in water, — 
for instance, the chlorides of sodium or calcium, — there was 
evolution of chlorine only at the positive electrode, and of hy- 
drogen, with the oxide of the hase, as soda or lime, at the ne- 
gative electrode. The process of decomposition may be viewed 
as proceeding in two or three ways, all terminating in the same 
results. Perhaps the simplest is to consider the chloride as the 
substance electrolyzed, its chlorine being determined to and 
evolved at the anode , and its metal passing to the cathode , 
where, finding no more chlorine, it acts upon the water, pro- 
ducing hydrogen and an oxide as secondary results. As the 
discussion would detain me from more important matter, and 
is not of immediate consequence, I shall defer it for the present. 
It is, however, of great consequence to state, that, on using the 
volta- electrometer, the hydrogen in both cases was definite ; 
and if the results do not prove the definite decomposition of 
chlorides, (which shall be proved elsewhere,— 789. 794. 814.,) 
they are not in the slightest degree opposed to such a con- 
clusion, <md_do support the general law . 

767. Hydriodic acid. — A solution of hydriodic acid was af- 
fected exactly in the same manner as muriatic acid. When 
strong, hydrogen was evolved at the negative electrode, in de- 
finite proportion to the quantity of electricity which had passed, 
i. e. in the same proportion as was evolved by the same current 
from water ; and iodine without any oxygen was evolved at the 
positive electrode. But when diluted, small quantities of oxy- 
gen appeared with the iodine at the anpde , the proportion of 
hydrogen at the cathode remaining undisturbed. 

768. I believe the decomposition of the hydriodic a6id in this 



Jan. 1834.] Iodides : — fluorides : — cyanides. 227 

case to be direct, for the reasons already given respecting mu- 1 
riatic acid (763. 764.). 

769. Iodides. — A solution of iodide of potassium being sub- 
jected to the voltaic current, iodine appeared at the positive 
electrode (without any oxygen), and hydrogen with free alkali 
at the negative electrode. The same observations as to the 
mode of decomposition are applicable here as were made in re- 
lation to the clilorides when in solution (766.). 

770. ify dr o -fluoric acid\ and fluorides. — Solution of hydro- 
fluoric acid did not appear to be decomposed under the influ- 
ence of the electric current : it was the water which gave way 
apparently. The fused fluorides were electrolyzed (117.); but 
having during these actions obtained fluorine in the separate 
state, I think it better fo refer to a future series of these Ite- 
searehes, in which I purpose giving a fuller account of the re- 
sults than would be consistent with propriety here *. 

771. Hydro- cyanic acid in solution conducts very badly* 
The definite proportion of hydrogen (equal to that from water) 
was set free at the cathode, whilst at the anode a small 
quantity of oxygen was evolved and apparently a solution of 
cyanogen formed. The action altogether corresponded with 
that on a dilute muriatic or hydriodic acid. When the hydro- 
cyanic acid was made a better conductor by sulphuric acid, the 
same results occurred. 

Cyanides. — -With a solution of the cyanide of potassium, the 
result was precisely the same as with a chloride or iodide. No 
oxygen was evolved at the positive electrode, but a brown 
solution formed there. For the reasons given when speaking 
of the chlorides (766.), and because a fused cyanide of potas- 
sium evolves cyanogen at the positive electrode f*. 1 incline to 
believe that the cyanide in solution is directly decomposed. 

772. Ferro-cyanic acid and the ferro-cyanides, as also sul- 
pha- cyanic acid and the sulpha -cyanides, presented results 
corresponding with those just described (771.). 

* I have not obtained fluorine : my expectations, amounting to conviction, 
passed away one by one when subjected to rigorous examination ; some very 
1838^ ar resu ^' 8 w ® re obtained ; and to one of these I refer at 1340. — (Dec. 

t It is a very remarkable thing to see carbon and nitrogen in this case 
determined powerfully towards the positive surface of the voltaic battery ; but 
it is perfectly in harmony with the theory of electro-chemical decomposition 
which I have adtanced. 

Q 2 



228 Primary or secondary decomposition. [Series VII. 

773. Acetic acid. — Glacial acetic acid, when fused (405.), is 
not decomposed by, nor does it conduct, electricity. On add- 
ing a little water to it, still there were tio signs of action ; on 
adding more water, it acted slowly and about as pure water 
would do. Dilute sulphuric [acid was added to it in order to 
make it a better conductor ; then the definite proportion of hy- 
drogen was evolved at the cathode , and a mixture of oxygen in 
very deficient quantity, with carbonic acic, and a little carbonic 
oxide, at the anode. Hence it appears that acetic a$id is not 
electrolyzable, but that a portion of it is decomposed by the 
oxygen evolved at the anode , producing secondary results, 
varying with the strength of the acid, the intensity of the cur- 
rent, and other circumstances. 

774. Acetates. — One of these has been referred to already, 
as affording only secondary results relative to the acetic acid 
(749.). With many of the metallic acetates the results at both 
electrodes are secondary (746. 750.) . 

Acetate of soda fused and anhydrous is directly decomposed, 
being, as I believe, a true electrolyte, and evolving soda and 
acetic acid at the cathode and anode. These however have 
no sensible duration, but are immediately resolved into other 
substances ; charcoal, sodiuretted hydrogen, &c. being set free 
at the former, and, as far as 1 could judge under the circum- 
stances, acetic acid mingled # with carbonic oxide, carbonic 
acid, &c. at the latter. 

775. Tartaric acid. — Pure solution of tartaric acid is almost 
as bad a conductor as pure water. On adding sulphuric 
acid, it conducted well, the results at the positive electrode 
being primary or secondary in different proportions, according 
to variations jn the strength of the acid and the power of the 
electric current (752.). Alkaline tartrates gave a large pro- 
portion of secondary results at the positive electrode. The 
hydrogen at the negative electrode remained constant unless 
certain triple metallic salts were used. 

776. Solutions, of salts containing other vegetable acids, as 
the benzoates ; of sugar, gum, &c., dissolved in dilute sulphu- 
ric acid ; of resin, albumen, &c,, dissolved in alkalies, were in 
turn submitted to the electrolytic power of the voltaic current. 
In all these cases, secondary results to a greater or smaller ex- 
tent were produced at the positive electrode. . 

777. In concluding this division of these Researches, it can- 



Jan. 1834.] Secondary results of decomposition. 229 

not but occur to the mind that the final result of the action of 
the electric current upon substances placed between the elec- 
trodes, instead of being simple may be very complicated. 
There are two modes by which these substances may be de- 
composed, either by the direct force of the electric current, or 
by the action of bodies which that current may evolve. There 
are also two modes by which new compounds may be formed, 
i . e . by cqpabination of the evolving substances whilst in their 
nascent state (658.), directly with the matter of the electrode ; 
or else their combination with those bodies, which being con- 
tained in, or associated with, the body suffering decomposition, 
are necessarily present at the anode and cathode. The com- 
plexity is rendered still ^greater by the circumstance that two 
or more of these actions may occur simultaneously, and also in 
variable proportions to each other. But it may in a great 
measure be resolved by attention to the principles already laid 
down (747.). 

778. When aqueous solutions of bodies arc used, secondary 
results are exceedingly frequent. Even when the water is not 
present in large quantity, but is merely that of combination, 
still secondary results often ensue : for instance, it is very pos- 
sible that in Sir Humphry Davy’s decomposition of the hydrates 
of potassa and soda, a part of the potassium produced was the 
result of a secondary action. Hence, also, a frequent cause for 
the disappearance of the oxygen and hydrogen which would 
otherwise be evolved : and when hydrogen does not appear at 
the cathode iu an aqueous solution , it perhaps always indicates 
that a secondary action has taken place there. No exception 
to this rule has as yet occurred to my observation, 

779. Secondary actions are not confined to aqueous solutions , 
or cases where water is present. For instance, various chlo- 
rides acted upon, when fused (402.), by platina electrodes, 
have the chlorine determined electrically to the anode. In 
many cases, as with the chlorides of lead, potassium, barium, 
&c., the chlorine acts on the platina and forms a compound 
'with it, which dissolves but when protochloride of tin is used, 
the chlorine at the anode does not act upon the platina, but 
upon the chloride already there, forming a perchloride which 
rises in vapour (790. 804.) . These are, therefore, instances of 



230 Definite electro-chemical decomposition . [Series VII. 

secondary actions of both kinds, produced in bodies containing 
no water. 

780. The production of boron from /used borax (402, 417.) 
is also a case of secondary action ; for boracic acid k not de- 
composable by electricity (408.), and it was the sodium evolved 
at the cathode which, re-acting on the boracic acid around it, 
took oxygen from it, and set boron free in the experiments 
formerly described. 

781. Secondary actions have already in the hands of M. 
Becquerel, produced many interesting results in the formation 
of compounds; some of them new, others imitations of those 
occurring naturally *. It is probable they may prove equally 
interesting in an opposite direction, L e» as affording cases of 
analytic decomposition. Much information regarding the com- 
position, and perhaps even the arrangement, of the particles of 
such bodies as the vegetable acids and alkalies, and organic 
compounds generally, will probably be obtained by submitting 
them to the action of nascent oxygen, hydrogen, chlorine, &c. 
at the electrodes; and the action seems the more promising, 
because of the thorough command which we possess over at- 
tendant circumstances, such as the strength of the current, the 
size of the electrodes, the nature of the decomposing conductor, 
its strength, &c., all of which may be expected to have their 
corresponding influence upon the final result. 

782. It is to me a great satisfaction that the extreme variety 
of secondary results has presented nothing opposed to the 
doctrine of a constant and definite electro-chemical action, to 
the particular consideration of which I shall now proceed. 


% vii. On the definite nature and extent of 'Electro -Chemical 
Decomposition. 

783. In the third series of these Researches, after proving 
the identity of electricities derived from different sources, and 
showing, by actual measurement, the extraordinary quantity of 
electricity evolved by a very feeble voltaic arrangement (371. 
376.),' I announced a law, derived from experiment, which 
seemed to me of the utmost importance to the science of elec- 


Annalos de Chirnie, tom. xxxv. 113. 



231 


Jan. 183 1.] Water: — muriatic acid, fyc. 

tricity in general, and that branch of it denominated electro- 
chemistry in particular. The law was expressed thus : The 
chemical power of a current of electricity is in direct propor- 
tion to the absolute quantity of electricity which passes (3 77.). 

784. In the further progress of the successive investigations, 
I have had frequent occasion to refer to the same law, some- 
times in circumstances offering powerful corroboration of its 
truth (456. 501. 505.) ; and the’prcsent scries already supplies 
numerou! new cases in which it holds goad (70 k 722. 726. 7 32.) . 
It is now my object to consider this great principle more closely, 
and to develope some of the consequences to which it leads. 
That the evidence for it may be the more distinct and appli- 
cable, I shall quote cases of decomposition subject to as few in- 
terferences from secondary results as possible, effected upon 
bodies very simple, yet very definite in their nature. 

785. In the first place, I consider the law as so fully es- 
tablished with respect to the decomposition of water, and under 
so many circumstances which might be supposed, if anything 
could, to exert an influence over it, that I may be excused 
entering into further detail respecting that substance, or even 
summing up the results here (732.) . I refer, therefore, to the 
whole of the subdivision of this series of Researches which 
contains the account of the volta-electrometer (70 b &c.). 

786. In the next place, I also consider the law as established 
with respect to muriatic acid *by the experiments and reason- 
ing already advanced, when speaking of that substance, in the 
subdivision respecting primary. and secondary results (758. &c.). 

787. I consider the law as established also with regard to 
hydriodic acid by the experiments and considerations already 
advanced in the preceding division of this scrips of Researches 
(767. 768.) . 

788. Without speaking with the same confidence, yet from 
the experiments described, and many others not described, re- 
lating to hydro -fluoric, hydro -cyanic, ferro-cyanic, and sulpho- 
cyanic acids (770. 771. 772.), and from the close analogy which 
holds between these bodies and the liydracids of chlorine, 
iodine, bromine, &c., I consider these also as coming under 
subjection to the law, and assisting to prove its truth. 

789. In the preceding cases, except the first, the water is 
believed to be inactive; but to avoid any ambiguity arising 



232 Definite electro-chemical decomposition. [Series VII. 

from its presence, I sought for substances from which it should 
be absent altogether ; and, taking advantage of the law of con- 
duction already developed (380. &c.), I«soon found abundance, 
amongst which protochloride of tin was first subjected to de- 
composition in the following manner. A piece of platina wire 
had one extremity coiled up into a small knob, and, having been 
carefully weighed, was sealed hermetically into a piece of bottle- 
glass tube, so that the knob should be at the bottom of the 
tube within (fig. 68.). The tube was suspended by a piece of 
platina wire, so that the heat of a spirit-lamp could be applied 
to it. Recently fused protochloride of tin was introduced in 
sufficient quantity to occupy, when melted, about one half of 
the tube ; the wire of the tube was connected with a volta-elec- 
trometer (711.), which was itself connected with the negative 
end of a voltaic battery ; and a platina wire connected with the 
positive end of the same battery was dipped into the fused 
chloride in the tube ; being however so bent, that it could not 
by any shake of the hand or apparatus touch the negative elec- 
trode at the bottom of the vessel. The whole arrangement is 
delineated in fig. 69. 

790. Under these circumstances the chloride of tin was de- 
composed : the chlorine evolved at the positive electrode 
formed bichloride of tin (779.), which passed away in fumes, 
and the tin evolved at the negative electrode combined with the 
platina, forming an alloy, fusible at the temperature to which 
the tube was subjected, and therefore never occasioning metallic 
communication through the decomposing chloride. When the 
experiment had been continued so long as to yield a reasonable 
quantity of gas in the volta-electrometer, the battery connexion 
was broken, the positive electrode removed, and the tube and 
remaining chloride allowed to cool. When cold, the tube was 
Broken open, the rest of the chloride and the glass being easily 
separable from the platina wire and its button of alloy. The 
latter when washed was then reweighed, and the increase gave 
the weight of the tin reduced. 

791. I will give the particular results of one experiment, in 
illustration of the mode adopted in this and others, the results 
of which I shall have occasion to quote. The negative elec- 
trode weighed at first 20 grains ; after the experiment, it, with 
its button of alloy, weighed 23*2 grains. The tin evolved by 



233 


Jan. 1834.] Chlorides of tin and lead. 

the electric current at the cathode weighed therefore 3*2 
grains. The quantity of oxygen and hydrogen collected in the 
volta-electrometer = 365 cubic inches. As 100 cubic inches 
of oxygen and hydrogen, in the proportions to form water, may 
be considered as weighing 12*92 grains, the 3*85 cubic inches 
would weigh 0*49742 of a grain ; that being, therefore, the 
weight of water decomposed by the same electric current as 
was able to decompose such weight of protochloride of tin as 
could yiefd 3*2 grains of metal. Now 0*49742 : 3*2 : : 9 the 
equivalent of water is to 57*9, which should therefore be the 
equivalent of tin, if the experiment had been made without er- 
ror, and if the electro-chemical decomposition is in this case 
also definite . In some chemical works 58 is given as the che- 
mical equivalent of tin, fn others 57*9. Both are so near to the 
result of the experiment, and the experiment itself is so subject 
to slight causes of variation (as from the absorption of gas in 
the volta-electrometer (716.), &c.), that the numbers leave little 
doubt of the applicability of the law of definite action in this 
and all similar cases of electro-decomposition. 

792. It is not often I have obtained an accordance in num- 
bers so near as that I have just quoted. Tour experiments 
were made on the protochloride of tin, the quantities of gas 
evolved in the volta-electrometer being from 2*05 to 10*29 cubic 
inches. The average of the i;our experiments gave 58*53 as 
the electro- chemical equivalent for tin. 

793. The chloride remaining after the experiment was pure 
protochloride of tin ; and no one can doubt for a moment that 
the equivalent of chlorine had been evolved at the anode , and, 
having formed bichloride of tin as a secondary result, had 
passed away. 

794. Chloride of lead was experimented upon in a manner 
exactly similar, except that a change was made in the nature of 
the positive electrode ; for as the chlorine evolved at the anode 
forms no perchloride of lead, but acts directly upon the platina, 
it produces, if that metal be used, a solution of chloride of 
platina in the chloride of lead ; in consequence of which a por- 
tion of platina can pass to the cathode , and would then pro- 
duce a vitiated result. I therefore sought for, and found in 
plumbago, another substance, which could be used safely as 
the positive electrode in such bodies as chlorides, iodides, &c. 



234 Definite electro- chemical decomposition . [Series VII. 

The chlorine or iodine does not act upon it, but is evolved in 
the free state ; and the plumbago has no re-action, under the 
circumstances, upon the fused chloride* or iodide in which it is 
plunged. Even if a few particles of plumbago[]skould separate 
by the heat or the mechanical action of the evolved gas, they 
can do no harm in the chloride. 

795. The mean of three experiments gave the number of 
100*85 as the equivalent for lead. The chemical equivalent is 
103*5. The deficiency in my experiments I attribute to the 
solution of part of the gas (716.) in the volta-electrometer ; but 
the results leave no doubt on my mind that both the lead and 
the chlorine are, in this case, evolved in definite quantities by 
the action of a given quantity of electricity (814. &c.) . 

796. Chloride of antimony . — rt was in endeavouring to ob- 
tain the clcctro-chemical equivalent of antimony from the chlo- 
ride, that I found reasons for the statement I have made re- 
specting the presence of water in it in an earlier part of these 
Researches (690. 693. &c.). 

797. I endeavoured to experiment upon the oxide of lead ob- 
tained by fusion and ignition of the titrate in a platina crucible, 
but found great difficulty, from the high temperature required 
for perfect fusion, and the powerful fluxing qualities of the 
substance. Green-glass tubes repeatedly failed. I at last 
fused the oxide in a small porcelain crucible, heated fully in a 
charcoal fire ; and, as it was essential that the evolution of the 
lead at the cathode should take place beneath the surface, the 
negative electrode was guarded by a green-glass tube, fused 
around it in such a manner as to expose only the knob of pla- 
tina at the lower end (fig. 70.), so that it could be plunged be- 
neath the surface, and thus exclude contact of air or oxygen 
with the lead reduced there. A platina wire Was employed for 
the positive electrode, that metal not being subject to any action 
from the oxygen evolved against it. The arrangement is given 
in fig. 71. 

798. In an experiment of this kind the equivalent for the 
lead came out 93*17, which is very much too small. Thi^ I 
believe, was because of the small interval between the positive 
and negative electrodes in the oxide of lead ; so that it was not 
unlikely that some of the froth and bubbles formed by the 
oxygen at the anode should occasionally even touch the lead 



235 


- Jan. 1834.] Fused oxides of lead , fyc. 

reduced At the cathode , and re-oxidize it. When I endea- 
voured to correct this by having more litharge, the greater 
heat required to keep it Jill fluid caused a quicker action on the 
crucible, which was soon eaten through, and the experiment 
stopped. 

799. In one experiment of this kind I used borate of lead 
(108. 673.). It evolves lead, under the influence of the elec- 
tric current, at the anode , and oxygen at the cathode ; and as 
the boracic acid is not either directly (408.) or incidentally 
decomposed during the operation, I expected a result depend- 
ent on the oxide of lead. The borate is not so violent a flux 
as the oxide, but it requires a higher temperature to make it 
quite liquid; and if not very hot, the bubbles of oxygen cling 
to the positive electrode, and retard the transfer of electricity. 
The number for lead came out 101*29, which is so near to 103*5 
as to show that the action of the current had been definite. 

800. Oxide of bismuth . — I found this substance required 
too high a temperature, and acted too powerfully as a flux, 
to allow of any experiment being made on it, without the 
application of more time and care than I could give at 
present. 

801. The ordinary 'protoxide of antimony , which consists of 
one proportional of metal and one and a half of oxygen, was 
-subjected to the action of the electric current in a green-glass 
tube (789.), surrounded by a jacket of platina foil, and heated 
in a charcoal fire. The decomposition began and proceeded 
very well at first, apparently indicating, according to the ge- 
neral law (679.697.), that this substance was one containing such 
elements and in such proportions as made it amenable to the 
power of the electric current. This effect I have, already given 
reasons for supposing may be due to the presence of a true 
protoxide, consisting of single proportionals (696. 693.). The 
action soon diminished, and finally ceased, because of the for- 
mation of a higher oxide of the metal at the positive electrode. 
This compound, which was probably the peroxide, being in- 

and insoluble in the protoxide, formed a crystalline crust 
around the positive electrode ; and thus insulating it, prevented 
the transmission of the electricity. Whether, if it had been 
fusible and still immiscible, it would have decomposed, is doubt- 
ful, because of its departure from the required composition 



236 Definite electrolyzation .* — iodides. [Series VII. 

(697.). It was a very natural secondary product at the positive 
electrode (779.) . On opening the tube it was found that a little 
antimony had been separated at tlie^negative electrode; but 
the quantity was too small to allow of any quantitative result 
being obtained*. 

802. Iodide of lead . — This substance can be experimented 
with in tubes heated by a spirit-lamp (789.) ; but I obtained no 
good results from it, whether I used positive electrqdes of pla- 
tina or plumbago. In two experiments the numbers for the 
lead came out only 75*46 and 73*45, instead of 103*5. This 
I attribute to the formation of a periodide at the positive 
electrode, which, dissolving in the mass of liquid iodide, 
came in contact with the lead evolved at the negative electrode, 
and dissolved part of it, becoming itself again protiodide. 
Such a periodide does exist; and it is very rarely that the 
iodide of lead formed by precipitation, and well washed, 
can be fused without evolving much iodine, from the presence 
of this percompound ; nor does crystallization from its hot 
aqueous solution free it from this substance. Even when a 
little of the protiodide and iodine are merely rubbed together 
in a mortar, a portion of the periodide is formed. And though 
it is decomposed by being fused and heated to dull l^edness 
for a few minutes, and the whole reduced to protiodide, yet 
that is not at all opposed to the possibility, that a little of that 
which is formed in great excess of iodine at the anode , should 
be cai'ricd by the rapid currents in the liquid into contapt with 
the cathode. 

803. This view of the result was strengthened by a third 
experiment, where the space between the electrodes was in- 
creased to on£ third of an inch ; for now the interfering effects 
were much diminished, and the number of the lead came out 
89*04 ; and it was fully confirmed by the results obtained in 
the cases of transfer to be immediately described (818.). 

The experiments on iodide of lead therefore offer no excep- 
tion to the general law under consideration, but on the con- 
trary may, from general considerations, be admitted as inclu- 
ded in it. 

804. ^ Protiodide of tin . — This substance, when fused (402.), 

* This paragraph is subject to the corrective note now appended to para- 
graph 696.— Dec. 1838. 



Jan. 1834.] Simultaneous definite action . 237 

conducts and is decomposed by the electric current, tin is evol- 
ved at the anode , and periodide of tin as a secondary result 
(779. 790.) at the cathode. The temperature required for its 
fusion is too high to allow of the production of any results fit 
for weighing. 

805. Iodide of potassium was subjected to electrolytic action 
in a tube, like that in fig, 68. (789.). The negative electrode was 
a globule of lead, and I hoped in this way to retain the potas- 
sium, and obtain results that could be weighed and compared 
with the volta-electrometer indication ; but the difficulties de- 
pendent upon the high temperature required, the action upon 
the glass, the fusibility of the platina induced by the presence 
of the leady and other circumstances, prevented me from pro- 
curing such results. Th« iodide was decomposed with the evo- 
lution of iodine at the anode , and of potassium at the cathode , 
as in former cases. 

806. In some of these experiments several substances were 
placed in succession, and decomposed simultaneously by the 
same electric current : thus, protochloride of tin, chloride of 
lead, and water, were thus acted on at once. It is needless to 
say that the results were comparable, the tin, lead, chlorine, 
oxygen, and hydrogen evolved being definite in quantity and 
electro- chemical equivalents to each other. 

807. Let us turn to another kmd of proof of the definite che- 
mical action of electricity , If any circumstances could be sup- 
posed to exert an influence over the quantity of the matters 
evolved during electrolytic action, one would expect them to 
be present when electrodes of different substances, and pos- 
sessing very different chemical affinities for such, matters, were 
used. Platina has no power in dilute sulphuric Ucid of combi- 
ning with the oxygen at the anode , though the latter be evol- 
ved in the nascent state against it. Copper, on the other hand, 
immediately unites with the oxygen, as the electric current sets 
it free from the hydrogen ; and zinc is not only able to combine 
with it, but can, without any help from the electricity, abstract 
it directly from the water, at the same time setting torrents of 
hydrogen free., Yet in cases where these three substances 
were used as the positive electrodes in three similar portions 
of the same dilute sulphuric acid, specific gravity 1*336 pre- 



238 Definite electro-chemical action. [Series VIL 

cisely the same quantity of water was decomposed by the elec- 
tric current, and precisely the same quantity of hydrogen set 
free at the cathodes of the three solutionis. 

808. The experiment was made thus. Portions of the di- 
lute sulphuric acid were put into three basins. Three volta- 
electromcter tubes, of the form figg. 60, 62. were filled with 
the same acid, and one inverted in each basin (707.). A zinc 
plate, connected with the positive end of a voltaic battery, was 
dipped into the first basin, forming the positive electrode there, 
the hydrogen, which was abundantly evolved from it by the di- 
rect action of the acid, being allowed to escape. A copper 
plate, which dipped into the acid of the second basin, was con- 
nected with the negative electrode of the first basin ; and a 
platina plate, which dipped into th& acid of the third basin, 
was connected with the negative electrode of the second basin. 
The negative electrode of the third basin was connected with a 
volta-elcctrometer (71 1.), and that with the negative end of the 
voltaic battery. 

809. Immediately that the circuit was complete, the electro- 
chemical action commenced in all the vessels. The hydrogen 
still rose in, apparently, undiminished quantities from the po- 
sitive zinc electrode in the first basin. No oxygen was evolved 
at the positive copper electrode in the second basin, but a sul- 
phate of copper was formed there ; whilst in the third basin 
the positive platina electrode evolved pure oxygen gas, and was 
itself unaffected. But in all the basins the hydrogen liberated 
at the negative platina electrodes was the same in quantity , and 
the same with the volume of hydrogen evolved in the volta- 
electromcter, showing that in all the vessels the current had 
decomposed an equal quantity of water. In this trying case, 
therefore, the chemical action of electricity proved to be per- 
fectly definite . 

810. A similar experiment was made with muriatic acid dilu- 
ted with its bulk of water. The three positive electrodes were 
zinc, silver, and platina ; the first being able to separate and 
combine with the chlorine without the aid of the current ; the 
second combining with the chlorine only after the current had 
set it free ; and the third rejecting almost the whole of it- The 
three negative electrodes were, as before, platina plates fixed 
within glass tubes. In this experiment, as M'the former, the 



Jan. 1834.] 


Fused chlorides : — silver. 


239 


quantity of hydrogen evolved at the cathodes was the same for 
all, and the same as the hydrogen evolved in the volta-electro- 
meter. I have already jgivcn my reasons for believing that in 
these experiments it is the muriatic acid which is directly de- 
composed by the electricity (764.) ; and the results prove that 
the quantities so decomposed are perfectly definite and pro- 
portionate to the quantity of electricity which has passed. 

811. In this experiment the chloride of silver formed in the 
second basin retarded the passage of the current of electricity, 
by virtue of the law of conduction before described (391.), so 
that it had to be cleaned off four or five times during the course 
of the experiment ; but this caused no difference betw ecu the 
results of that vessel and the others. 

812. Charcoal was used as the positive electrode in both 
sulphuric and muriatic acids (808. 810.) ; but this change pro- 
duced no variation of the results. A zinc positive electrode, 
in sulphate of soda or solution of common salt, gave the same 
constancy of operation. 

813. Experiments of a similar kind were then made with 
bodies altogether in a different state, i . e. with fused chlorides, 
iodides, &c. I have already described an experiment with 
fused chloride of silver, in which the electrodes were of metal- 
lic "sil\er, the one rendered negative becoming increased and 
lengthened by the addition of metal, whilst the other was dis- 
solved and eaten away by its abstraction. This experiment 

,was repeated, two weighed pieces of silver wire being used as 
the electrodes, and a volta-electrometer included in the circuit. 
Great care was taken to withdraw r the negative electrode so re- 
gularly and steadily that the crystals of reduced silver should 
not form a metallic communication beneath the surface of the 
fused chloride. On concluding the experiment thb positive elec- 
trode was re- weighed, and its loss ascertained. The mixture 
of chloride of silver, and metal, withdrawn in successive por- 
tions at the negative electrode, was digested in solution of am- 
monia> to remove the chloride, and the metallic silver remaining 
also weighed : it was the reduction at the cathode , and exactly 
equalled the solution at the anode ; and each portion was as 
nearly as possible the equivalent to the water decomposed in 
the volta- electrometer. 

814. The inft^lble condition of the silver at the temperature 



240 Definite electrolyzation of chloride of lead. [Semes VII. 

used, and the length and ramifying character of its crystals, 
render the above experiment difficult to perform, and uncer- 
tain in its results. I therefore wrought with chloride of lead, 
using a green-glass tube, formed as in fig. 72. A weighed 
platina wire was fused into the bottom of a small tube, as be- 
fore described (789.). The tube was then bent to an angle, 
at about half an inch distance from the closed end ; and the 
part between the angle and the extremity being softened, was 
forced upward, as in the figure, so as to form a bridge, or 
rather separation, producing two little depressions or basins a, 
by within the tube. This arrangement was suspended by a 
platina wire, as before, so that the heat of a spirit-lamp could 
be applied to it, such inclination being given to it as would 
allow all air to escape during the fusiop of the chloride of lead. 
A positive electrode was then provided, by bending up the end 
of a platina wire into a knot, and fusing about twenty grains of 
metallic lead on to it, in a small closed tube of glass, which was 
afterwards broken away. Being so furnished, the wire with 
its lead was weighed, and the weight recorded. 

815. Chloride of lead was now introduced into the tube, and 
carefully fused. The leaded electrode was also introduced ; 
after which the metal, at its extremity, soon melted. In this 
state of things the tube was filled up to c with melted chloride 
of lead ; the end of the electrode to be rendered negative was 
in the basin by and, the electrode of melted lead was retained 
in the basin a } and, by connexion with the proper conducting 
wire of a voltaic battery, was rendered positive. A volta-elec- 
trometer was included in the circuit. 

816. Immediately upon the completion of the communication 
with the voltaic battery, the current passed, and decomposition 
proceeded. No chlorine was evolved at the positive electrode ; 
but as the fused chloride was transparent, a button of alloy 
could be observed gradually forming and increasing in size at 
by whilst the lead at a could also be seen gradually to diminish. 
After a time, the experiment was stopped ; the tube allowed to 
cool, and broken open ; the wires, with their buttons, cleaned 
and weighed ; and their change in weight compared with the 
indication of the volta- electrometer. 

817. In this experiment the positive electrode had lost just 
as much lead as the negative one had gained (795.)* and the 



241 


Jan. 1834.] DefinHe electro -chemical action . 

loss and gain were very nearly the equivalents of the water de- 
composed in the volta-electrometer, giving for lead the number 
101*5. It is therefore evident, in this instance, that causing a 
strong affinity , or no affinity, for the substance evolved at the 
anode , to be active during the experiment (807.), produces no 
variation in the definite action of the electric current. 

818. A similar experiment was then made with iodide of lead, 
and in this manner all confusion from the formation of a perio- 
dide avoided (803.). No iodine was evolved during the whole 
action, and finally the loss of lead at the anode was the same as 
the gain at the cathode , the equivalent number, by comparison 
with the result in the volta-eleetrometer, being 103*5. 

819. Then protochloride of tin was subjected to the electric 
current in the same manner, using of course, a tin positive elec- 
trode. No bichloride of tin was now formed (779. 790.). On 
examining the two electrodes, the positive had lost precisely as 
much as the negative had gained ; and by comparison with the 
volta-electromcter, the number for tin came out 59. 

820. It is quite necessary in these and similar experiments 
to examine the interior of the bulbs of alloy at the ends of the 
conducting wires; for occasionally, and especially with those 
which have been positive, they are cavernous, and contain por- 
tions of the chloride or iodide used, which must be removed 
before the final weight is ascertained. This is more usually 
the case with lead than tin. 

821. All these facts combine into, I think, an irresistible 
mass of evidence, proving the truth of the important proposi- 
tion which I at first laid down, namely, that the chemical power 
of a current of electricity is in direct proportion to the abso- 
lute quantity of electricity which passes (377. 783.). They 
prove, too, that this is not merely true with one substance, as 
water, but generally with all electrolytic bodies; and, further, 
that the results obtained with any one substance do not merely 
agree amongst themselves, but also with those obtained from 
other substances , the whole combining together into one series 
of definite electro -chemical actions (505.). I do not mean to 
say that no exceptions xyill appear : perhaps some may arise, 
especially amongst substances existing only by weak affinity ; 
but I do not expect that any will seriously disturb the result 
announced. „ If, in the well considered, well examined, and, I 

a* 



242 


Definite electro-chemical action. [Series VII. 

may surely say, well ascertained doctrines of the definite na- 
ture of ordinary chemical affinity, such exceptions occur, as 
they do in abundance, yet, without being allowed to disturb 
our minds as to the general conclusion, they ought also to be 
allowed if they should present themselves at this, the opening 
of a new view of electro-chemical action ; not being held up as 
obstructions to those who may be engaged in rendering that 
view more and more perfect, but laid aside for a while, in hopes 
that their perfect and consistent explanation will ultimately 
appear. 

822. The doctrine of definite electro-chemical action just 
laid down, and, I believe, established, leads to some new view's 
of the relations and classifications of bodies associated with or 
subject to this action. Some of these I shall proceed to con- 
sider. 

823. In the first place, compound bodies may be separated 
into two great classes, namely, those which are decomposable 
by the electric current, and those which are not : of the latter, 
some are conductors, others non-conductors, of voltaic elec- 
tricity*. The former do not depend for their decomposability 
upon the nature of their elements only; for, of the same two 
elements, bodies may be formed, of which one shall belong to 
one class and another to the other class ; but probably on the 
proportions also (697.). It is' further remarkable, that with 
very few, if any, exceptions (414. 691.), these decomposable 
bodies are exactly those governed by the remarkable law of 
conduction I have before described (394.) ; for that law does 
not extend to the many compound fusible substances that are 
excluded from this class. I propose to call bodies of this, the 
decomposable class, Electrolytes (664.). 

824. Then, again, the substances into which these divide, un- 
der the influence of the electric current, form an exceedingly im- 
portant general class. They are combining bodies; are directly 
associated with the fundamental parts of the doctrine of chemi- 
cal affinity ; and have each a definite proportion, in which they 
are always evolved during electrolytic action. I have proposed 
to call these bodies generally ions } or particularly aniofis and 

* I mean here by voltaic electricity, merely electricity $om a most abun- 
dant source, but having very small intensity. 



Jan. 1834.] General propositions. 243 

cations, according as they appear at the anode or cathode 
(665.) ; and the numbers representing the proportions in which 
they are evolved electrochemical equivalents . Thus hydrogen, 
oxygen, chlorine, iodine, lead, tin are ions; the three former 
are anions , the two metals are cations, and 1, 8, 36, 125, 104, 
58, are their electro -chemical equivalents nearly. 

825. A summary of certain points already ascertained re- 
specting electrolytes , ions, and electro -chemical equivalents , 
may be gi^en in the following general form of propositions, 
without, I hope, including any serious error. 

826. i. A single ion, i. e . one not in combination with another, 
will have no tendency to pass to either of the electrodes, and 
will be perfectly indifferent to the passing current, unless it be 
itself a compound of mc*rc elementary ions , and so subject to 
actual decomposition. Upon this fact is founded much of the 
proof adduced in favour of the new theory of electro-chemical 
decomposition, which I put forth in a former series of these 
llcsearches (518. &c.). 

827. ii. If one ion be combined in right proportions (697.) 
with another strongly opposed to it in its ordinary chemical re- 
lations, i. e. if an anion be combined with a cation , then both 
will travel, the one to the anode, the other to the cathode, of the 
decomposing body (530. 542 . 547.). 

828. iii. If, therefore, an ion yass towards one of the elec- 
trodes, another ion must also be passing simultaneously to the 
other electrode, although, from secondary action, it may not 
make its appearance (743.). 

829. iv. A body decomposable directly by the electric cur- 
rent, i. e. an electrolyte, must consist of two ions, and must also 
render them up during the act of decomposition. 

830. v. There is but one electrolyte composed of fhe same tw o 
elementary ions ; at least such appears to be the fact (697.), de- 
pendent upon a law, that only single electro-chemical equivalents 
of elementary ions can go to the electrodes, and not multiples . 

831. vi. A body not decomposable when alone, as boracic 
acid, is not directly decomposable by the electric current when 
in combination (780.) , It may act as an ion going wholly to the 
anode pr cathode^ hot does not yield up its elements, except 
occasionally by a .' secondary action. Perhaps it superfluous 
for me to point out that this proposition has no relation to such 



244 Definite electro-chemical action . [Series VII. 

cases as that of water, which, by the presence of other bodies, 
is rendered a better conductor of electricity, and therefore is 
more freely decomposed. 

832. vii. The nature of the substance of which the electrode 
is formed, provided it be a conductor, causes no difference in 
the electro-decomposition, either in kind or degree (807. 813.) : 
but it seriously influences, by secondary action (741.), the state 
in which the ions finally appear. Advantage ihay be taken of 
this principle in combining and collecting such tons as, if 
evolved in their free state, would be unmanageable*. 

833. viii. A substance which, being used as the electrode, 
can combine with the ion evolved against it, is also, I believe, 
an ion , and combines, in such cases, in the quantity represented 
by its electro-chemical equivalent. AK the experiments I have 
made agree with this view ; and it seems to me, at present, to 
result as a necessary consequence. Whether, in the secondary 
actions that take place, where the ion acts, not upon the mat- 
ter of the electrode, but on that which is around it in the liquid 
(744.), the same consequence follows, will require more extended 
investigation to determine. 

834. ix. Compound ions are not necessarily composed of 
electro-chemical equivalents of simple ions. For instance, sul- 
phuric acid, boracic acid, phosphoric acid, are ions, but not 
electrolytes, i. e. not composed of electro-chemical equivalents 
of simple ions. 

835. x. Electro-chemical equivalents are always consistent; 
i. e. the same number which represents the equivalent of a 
substance A when it is separating from a substance B, will also 
represent A when separating from a third substance C. Thus, 
8 is the electro-chemical equivalent of oxygen, whether sepa- 
rating from hydrogen, or tin, or lead ; and 103*5 is the electro- 
chemical equivalent of lead, whether separating from oxygen, 
or chlorine, or iodine. 


* It will often happen that the electrodes used may be of such a nature as, 
with the fluid in which they are immersed, to produce an electric current, either 
according with or opposing that of the voltaic arrangement used, and in this 
way, or by direct chemical action, may sadly disturb the results. Still* in the 
midst of all these confusing effects, the electric currept, which actually passes 
in any direction through the body suffering decomposition, will produce its own 
definite electrolytic action. 



Jan. 1834.] General propositions. 245 

836. xi. Electro-chemical equivalents coincide, and are the 
same, with ordinary chemical equivalents. 

837 . By means of experiment and the preceding propositions, 
a knowledge of ions and their electro-chemical equivalents may 
be obtained in various ways. 

838. In the first place, they may be determined directly, as 
has been done with hydrogen, oxygen, lead, and tin, in the nu- 
merous experiments already quoted. 

839. In the next place, from propositions ii. and iii., may be 
deduced the knowledge of many other ions , and also their 
equivalents. When chloride of lead was decomposed, platina 
being used for both electrodes (395.), there could remain no 
more doubt that chlorine was passing to the anode , although it 
combined with the platifia there, than when the positive elec- 
trode, being of plumbago (794.), allowed its evolution in the 
free state ; neither could there, in either case, remain any doubt 
that for every 1035 parts of lead evolved at the cathode , 36 
parts of chlorine were evolved at the anode , for the remaining 
chloride of lead was unchanged. So also, when in a metallic 
solution one volume of oxygen, or a secondary compound con- 
taining that proportion, appeared at the anode , no doubt could 
arise that hydrogen, equivalent to two volumes, had been de- 
termined to the cathode, although, by a secondary action, it 
had been employed in reducing pxides of lead, copper, or other 
metals, to the metallic state. In this manner, then, we learn 
from the experiments already described in these Researches, 
that chlorine, iodine, bromine, fluorine, calcium, potassium, 
strontium, magnesium, manganese, &c., are ions , and that their 
electroTchernical equivalents are the same as their ordinary 
chemical equivalents . 

840. Propositions iv. and v. extend our means of gaining in- 
formation. For if a body of known chemical composition is 
found to be decomposable, and the nature of the substance 
evolved as a primary or even a secondary result (743. 777.) at 
one of the electrodes, be ascertained, the electro-chemical 
equivalent of that body may be deduced from the known con- 
stant composition of the substance evolved. Thus, when fused 
protiodide of tin is decomposed by the voltaic current (804.), 
the eonclusipn may be drawn, that both the iodine and tin 
are ions , and that the proportions in which they com ine in the 



246 Definite electro -chemical action. [Series VII. 

fused compound express their electro-chemical equivalents. 
Again, with respect to the fused iodide of potassium (805.), it 
is an electrolyte ; and the chemical equivalents will also be the 
electro- chemical equivalents. 

841. If proposition viii. sustain extensive experimental in- 
vestigation, then it will not only help to confirm the results ob- 
tained by the use of the other propositions, but will give 
abundant original information of its oun. 

842. In many instances, the secondary results obtained by 
the action of the evolved ion on the substances present in the 
surrounding liquid or solution, will give the electro-chemical 
equivalent. Thus, in the solution of acetate of lead, and, as 
far as I have gone, in other proto-salts subjected to the re- 
ducing action of the nascent hydrogen* at the cathode , the metal 
precipitated has been in the same quantity as if it had been a 
primary product, (provided no free hydrogen escaped there,) 
and therefore gave accurately the number representing its elec- 
tro-chemical equivalent. 

813. Upon this principle it is that secondary results may oc- 
casionally be used as measurers of the volta-electric current 
(706. 740.) but there are not many metallic solutions that an- 
swer this purpose well : for unless the metal is easily precipi- 
tated, hydrogen will be evolved at the cathode and vitiate the 
result. If a soluble peroxide is formed at the anode , or if the 
precipitated metal crystallize across the solution and touch the 
positive electrode, similar vitiated results are obtained. I ex- 
pect to find in some salts, as the acetates of mercury and zinc, 
solutions favourable for this use. 

841. After the first experimental investigations to establish 
the definite chemical action of electricity, I have not hesitated 
to apply the more strict results of chemical analysis to correct 
the numbers obtained as electrolytic results. This, it is evident, 
may be done in a great number of cases, without using too 
much liberty towards the due severity of scientific research. 
The series of numbers representing electro-chemical equivalents 
must, like those expressing the ordinary equivalents of chemi- 
cally acting bodies, remain subject to the continual correction 
of experiment and sound reasoning. 

845. I give the following brief Table of iom and their elec- 
tro-chemical equivalents, rather as a specimen of a first attempt 



Ions , anions 3 and cations . 


247 


Jan. 1834.] 

than as anything that can supply the want which must very 
quickly be felt, of a full and complete tabular account of this 
class of bodies. LooMng forward to such a table as of extreme 
utility (if well constructed) in developing the intimate relation 
of ordinary chemical affinity to electrical actions, and identify- 
ing the two, not to the imagination merely, but to the conviction 
of the senses and a sound judgement, I may be allowed to ex- 
press a hope, that the endeavour will always be to make it a 
table of real, and not hypothetical, electro* chemical equiva- 
lents; for we shall else overrun the facts, and lose all sight and 
consciousness of the knowledge lyiug directly in our path. 

846. The equivalent numbers do not profess to be exact, 
and are taken almost entirely from the chemical results of other 
philosophers in whom T could repose more confidence, as to 
these points, than in myself. 


847, Table op Ions. 


Oxygen 8 

Chlorine 355 

Iodine 120* 

Bromine 78*3 

l luorine 18*7 

Cyanogen 26 

Sulphuric acid . . 40 


Anions . 


Selenic acid .... 01 

Nitric acid 54 

Chloric acid .... 75*5 
Phosphoric acid. . 35*7 
Carbonic acid. .. . 22 
Boracic acid .... 24 
Acetic acid* 51 


Tartaric acid .... 

66 

Citric acid 

58 

Oxalic acid 

36 

Sulphur (?) .... 

16 

Selenium (?) .... 


Sulpho-cyanogen 



1 

$)*2 
23-3 
10 
68-7 
43*8 
2041 
12*7 
27*7 
32*5 
57*0. 

Y - 103*5 

Iron 28 

Copper 31*6 | 


Cations, 

Cadmium .... 55*8 

Cerium 46 

Cobalt 29*5 

Nickel 29*5 

Antimony .... 64*6? 

Bismuth 71 

Mercury 200 

Silver 108 

Platina 98*6? 

Gold (?) 


Ammonia .... 17 

Potassa 47*2 


! Soda 31 *3 

Lilhia 18 

Baryta 76*7 

Slronti.a 51*8 

Lime 28* 

Magnesia 20*7 

Alumina (?) 

Protoxides generally. 

Quinia . . > 171*6 

Cinchona 160 

Morphia 290 

Vegeto-alkalies gene- 
rally. 


Hydrogen 

Potassium . . , . 

Sodium 

Lithium 

Barium 

Strontium . . . , 

Calcium 

Magnesium .... 
Manganese .... 

Zinc 

Tin 


This TaMta might be further arranged into groups of 
such substances as either act with, or replace, each other. 
Thus, for instance, acids and bases act in relation to each 



248 Definite electro-chemical action. [Series VII. 

other ; but they do not act in association with oxygen, hydro- 
gen, or elementary substances. There is indeed little or no 
doubt tli at, when the electrical rclation^of the particles of mat- 
ter come to be closely examined, this division must be made. 
The simple substances, with cyanogen, sulpho-cyanogen, and 
one or two other compound bodies, will probably form the first 
group ; and the acids and bases, with such analogous com- 
pounds as may prove to be ions , the second group. 9 Whether 
these will include all ions , or whether a third class of more 
complicated results will be required, must be decided by future 
experiments. 

819. It is probable that all our present elementary bodies 
are ions , but that is not as yet certain . There are some, such 
as carbon, phosphorus, nitrogen, silicon, boron, alumium, the 
right of which to the title of ion it is desirable to decide as soon 
as possible. There are also many compound bodies, and 
amongst them alumina and silica, which it is desirable to class 
immediately by unexceptionable experiments. It is also pos- 
sible , that all combinable bodies, compound as well as simple, 
may enter into the class of ions ; but at present it does not 
seem to me probable. Still the experimental evidence I have 
is so small in proportion to what must gradually accumulate 
around, and bear upon, this point, that I am afraid to gi\e a 
strong opinion upon it. 

850. I think I cannot deceive myself in considering the doc- 
trine of definite electro-chemical action as of the utmost import- 
ance. It touches by its facts more directly and closely than 
any former fact, or set of facts, have done, upon the beautiful 
idea, that ordinary chemical affinity is a mere consequence of 
the electrical attractions of the particles of different kinds of 
matter ; and it will probably lead us to the means by which we 
may enlighten that which is at present so obscure, and either 
fully demonstrate the truth of the idea, or develope that which 
ought to replace it. 

851. A very valuable use of electro-chemical equivalents will 
be to decide, in cases of doubt, what is the true chemical equi- 
valent, or definite proportional, or atomic number of a body ; 
for I have such conviction that the power which governs elec- 
tro-decomposition and ordinary chemical attractions is thosame ; 
and such confidence in the overruling influence of those natu- 



249 


Jan. 1834.] Quantity of electricity in matter . 

ral laws which render the former definite, as to feel no hesita- 
tion in believing that the latter must submit to them also. Such 
being the case, lean lufveno doubt that, assuming hydrogen 
as 1, and dismissing small fractions for the simplicity of expres- 
sion, the equivalent number or atomic weight of oxygen is 8, 
of chlorine 36, of bromine 78*4, of lead 103*5, of tin 59, &c., 
notwithstanding that a very high authority doubles several of 
these numbers. 

§ 13. On the absolute quantity of Electricity associated with 
the particles or atoms of Matter . 

852. The theory of definite electrolytieal or electro-chemical 
action appears to me to # touch immediately upon the absolute 
quantity of electricity or electric power belonging to different 
bodies. It is impossible, perhaps, to speak on this point with- 
out committing oneself beyond what present facts will sustain ; 
and yet it is equally impossible, and perhaps would be impoli- 
tic, not to reason upon the subject. Although we know no- 
thing of what an atom is, yet we cannot resist forming some 
idea of a small particle, which represents it to the mind ; and 
though we are in equal, if not greater, ignorance of electricity, 
so as to be unable to say whether it is a particular matter or 
matters, or mere motion of ordinary matter, or somethin! kind 
of power or agent, yet there is an immensity of facts which jus- 
tify us in believing that the atoms of matter are in some way 
endowed or associated with electrical powers, to which they 
owe their most striking qualities, and amongst them their 
mutual chemical affinity. As soon as we perceive, through the 
teaching of Dalton, that chemical powers are, however, varied 
the circumstances in which they are exerted, definite for each 
body, we learn to estimate the relative degree of force which 
resides in such bodies : and when upon that knowledge comes 
the fact, that the electricity, which we appear to be. capable of 
loosening from its habitation for a while, and conveying from 
place to place, whilst it retains its chemical force , can be mea- 
sured out, and being so measured is found to be as definite in 
its action as any of those portions which, remaining associated 
with the particles of matter, give them their chemical rela- 
tion ; we seem to have found the link which connects the pro- 



250 


Quantity of electric force in matter . [Series VII. 

portion of that we have evolved to the proportion of that belong- 
ing to the particles in their natural state/ 

853. Now it is wonderful to observe how small a quantity 
of a compound body is decomposed by a certain portion of elec- 
tricity. Let us, for instance, consider this and a few other 
points in relation to water. One grain of water, acidulated to 
facilitate conduction, will require an electric current to be con- 
tinued for three minutes and three quarters of timp to effect 
its decomposition, which current must be powerful enough to 
retain a platina wire r ^ T of an inch in thickness*, red hot, in 
the air during the whole time; and if interrupted anywhere by 
charcoal points, will produce a very brilliant and constant star 
of light. If attention be paid to the instantaneous discharge* of 
electricity of tension, as illustrated in the beautiful experiments 
of Mr. AYheatstonef, and to what I have said elsewhere on the 
relation of common and voltaic electricity (371. 375.), it will not 
be too much to say that this necessary quantity of electricity is 
equal to a very powerful flash of lightning. Yet we' have it 
under perfect command ; can evolve, direct, and employ it at 
pleasure ; and when it has performed its full work of electro- 
lyzation, it has only separated the elements of a single grain 
of water . 

854. On the other hand, the relation between the conduction 
of the electricity and the decomposition of the water is so close, 
that one cannot take place without the other. If the water is 
altered only in that small degree which consists in its having 

* I ha\e not stated the length of wire used, because I find by experiment, 
as would be expected in theory, that it is indifferent, The same quantity of 
electricity which, passed in a ghen time, can heat an inch of platina wire of a 
certain diameter red hot, can also heat a hundred, a thousand, or any length 
of the same wire to the same degree, provided the cooling circumstances are 
the same for every part in all cases. This I have proved by the volta-electro- 
meter. I found that whether half an inch or eight inches were retained at one 
constant temperature of dull redness, equal quantities of water were decom- 
posed in equal times. When the half-inch was used, only the centre portion of 
wire was ignited. A fine wire may even be used as a rough but ready regula- 
tor of a voltaic current; for if it be made part of the circuit, and the larger 
wires communicating with it be shifted nearer to or further apart, so as to keep 
the portion of wire in the circuit sensibly nt the same temperature, the extent 
passing through it will be nearly uniform. 

t Literary Gazette, 1833, March 1 and 8. Philosophical Magazine, 1833, 
p. 204. LTnstitute, 1833, p. 201. 



251 


Jan. 1834.] Quantity of electric force in matter. 

the solid instead of the fluid state, the conduction is stopped, 
and the decomposition is stopped with it. Whether the con- 
duction be considered »as depending upon the decomposition, 
or not (413. 703.), still the relation of the two functions is 
equally intimate and inseparable. 

855. 'Considering this close and twofold relation, namely, 
that without decomposition transmission of electricity does not 
occur; and, that for a given definite quantity of electricity 
passed, an equally definite and constant quantity of water or 
other matter is decomposed ; considering also that the agent, 
which is electricity, is simply employed in overcoming electri- 
cal powers in the body subjected to its action ; it seems a pro- 
bable, and almost a natural consequence, that the quantity 
which passes is the equivalent of, and therefore equal to, that 
of the particles separated ; i . e. that if the electrical power 
which holds the elements of a grain of water in combination, 
or which makes a grain of oxygen and hydrogen in the right 
proportions unite into water when they arc made to combine, 
could be thrown into the condition of a current, it would ex- 
actly equal the current required for the separation of that gram 
of water into its elements again. 

850. This view of the subject gives an almost overwhelming 
idea of the extraordinary quantity or degree of electric power 
which naturally belongs to the particles of matter ; but it is not 
inconsistent in the slightest degree with the facts which can be 
brought to bear on this point. To illustrate this I must say a 
few' words on the voltaic pile*. 

857. Intending hereafter to apply the results given in this 
and the preceding series of Researches to a close investigation 
of the source of electricity in the voltaic instrument, I have re- 
frained from forming any decided opinion on the subject ; and 
without at all meaning to dismiss metallic contact, or the con- 
tact of dissimilar substances, being conductors, but not metal- 
lic, as if they had nothing to do with the origin of the current, 

* By the term voltaic pile, I mean such apparatus or arrangement of metals 
as up to this time have been called so, and which contain water, brine, acid*, 
or other aqueous solutions or decomposable substances (476.), between their 
plates; Other kinds of electric apparatus may be hereafter invented, and I 
hope to construct Some not belonging to the class of instruments discov ered 

by Volta. 



252 


[Series VII. 


Nature of the voHuic pile. 

I still am fully of opinion with Davy, that it is at least continued 
by chemical action, and that the supply constituting the current 
is almost entirely from that source. 

858. Those bodies which, being interposed betw een the metals 
of the voltaic pile, render it active, are all of them electro - 
lytes (476.) ; and it cannot but press upon the attention of 
every one engaged in considering this subject, that in those 
bodies (so essential to the pile) decomposition and Die trans- 
mission of a current are so intimately connected, that one cannot 
happen without the other. This I have shown abundantly in 
water, and numerous other cases (402. 476.). If, then, a voltaic 
trough have its extremities connected by a body capable of being 
decomposed, as water, we shall have a continuous current through 
the apparatus ; and whilst it remains iti this state we may look 
at the part where the acid is acting upon the plates, and that 
where the current is acting upon the water, as the reciprocals 
of each other, in both parts we have the two conditions in- 
separable in such bodies as these , namely, the passing of the 
current, and decomposition; and this is as true, of the cells in 
the battery as of the water cell ; for no voltaic battery has as 
yet been constructed in which the chemical action is only that 
of combination : decomposition is always included , and is, 1 
believe, an essential chemical part. 

859. But the difference in the two parts of the connected 
battery, that is, the decomposition or experimental cell, and 
the acting cells, is simply this. In the former we urge the cur- 
rent through, but it, apparently of necessity, is accompanied 
by decomposition : in the latter we cause decompositions by 
ordinary chemical actions, (which are, however, themselves 
electrical*) and, as a consequence, have the electrical current ; 
and as the decomposition dependent upon the current is definite 
in the former case, so is the current associated with the decom- 
position also definite in the latter (862. &e\). 

860. Let us apply this in support of what I have surmised 
respecting the enormous electric power of each particle or atom 
of matter (8o6.). I showed in a former series of these Re- 
searches on the relation by measure of common and voltaic 
electricity, that two wires, one of platina and one of zinc, 
each one eighteenth of an inch in diameter, placed five six- 
teenths of an inch apart, and immersed to -the depth of five 



253 


Jan. 1834.] Quantity of electric force in matter . 

eighths of an inch in acid, consisting of one drop of oil of vitriol 
and four ounces pf distilled water at a temperature of about 60° 
Fahr., and connected at # the other extremities by a copper wire 
eighteen feet long, and one eighteenth of an inch in thickness, 
yielded as much electricity in little more than three seconds of 
time as a Leyden battery charged by thirty turns of a very 
large and powerful plate electric machine in full action (371.). 
This quantity, though sufficient if passed at once through the 
head of a •rat or cat to have killed it, as by a flash of lightning, 
was evolved by the mutual action of so small a portion oP the 
zinc wire and water in contact with it, that the loss of weight 
sustained by either would be inappreciable by our most deli- 
cate instruments ; and as to the water which could be decom- 
posed by that current, it*must have been insensible in quantity, 
for no trace of hydrogen appeared upon the surface of the 
platina during those three seconds. 

801. What an enormous quantity of electricity, therefore, is 
required for the decomposition of a single grain of water ! W T e 
have already seen that it must lx? in quantity sufficient to sus- 
tain a platina wire ^03 an inch in thickness, red hot, in con- 
tact with the air, for three minutes and three quarters (853.), a 
quantity which is almost infinitely greater than that which 
could be evolved by the little standard voltaic arrangement to 
which I have just referred (860. 371.). I have endeavoured to 
make a comparison by the loss of weight of such a Avire in a given 
time in such an acid, according to a principle and experiment 
to be almost immediately described (862.) ; but the proportion 
is so high that I, am almost afraid to mention it. It would 
appear that 800,000 such charges of the Leyden battery as I 
have referred to above, would be necessary to supply electricity 
sufficient to decompose a single grain of water ; or, if 1 am 
right, to equal the quantity of electricity which is naturally 
associated with the elements of that grain of water, endowing 
them with their mutual chemical affinity. 

862. In further proof of this high electric condition of the 
particles of matter, and the identity - as to quantity of that be- 
longing to them with that necessary for their separation , I will 
describe an experiment of great simplicity hut extreme beauty, 
wheij viewed in relation to the evolution of an electric current 
and its decomposing powers. 



254 Quantity of Electric force in matter . [Series VII. 

863. A dilute sulphuric acid, made by adding about one part 
by measure of oil of vitriol to thirty parts of water, will act 
energetically upon a piece of zinc plate jn its ordinary and sim- 
ple state : but, as Mr. Sturgeon as shewn*, not at all, or 
scarcely so, if the surface of the metal has in the first instance 
been amalgamated ; yet the amalgamated zinc will act power- 
fully with platina as an electromotor, hydrogen being evolved 
on the surface of the latter metal, as the zinc is oxidized and 
dissolved. The amalgamation is best effected by sprinkling a 
few drops of mercury upon the surface of the zinc, the latter 
being moistened with the dilute ’ acid, and rubbing with the 
fingers or tow so as to extend the liquid metal over the whole 
of the surface. Any mercury in excess, forming liquid drops 
upon the zinc, should be wiped offf. 

804. Two plates of zinc thus amalgamated were dried and 
accurately weighed; one, which we will call A, weighed 163T 
grains ; the other to be called 13, weighed 1483 grains. They 
were about five inches long, and 04 of an inch wide. An 
earthenware pneumatic trough was filled with dilute sulphuric 
acid, of the strength just described (863.), and a gas jar, also filled 
with the acid, inverted in itj. A plate of platina of nearly the 
same length, but about three times as wide as the zinc plates, 
was put up into this jar. The zinc plate A was also introduced 
into the jar, and brought in contact with the platina, and at the 
same moment the plate B was put into the acid of the trough, 
but out of contact with other metallic matter. 

865. Strong action immediately occurred in the jar upon the 
contact of the zinc and platina plates. Hydrogen gas rose 
from the platina, and was collected in the jar, but no hydrogen 
or other gas rose from either zinc plate. In about ten or twelve 
minutes, sufficient hydrogen having been collected, the experi- 
ment was stopped ; during its progress a few small bubbles had 
appeared upon plate B, but none upon plate A. The plates 

* Recent Experimental Researches, &c., 1830, p. 74, &c, 

t The experiment may be made with pure zinc, wbiclq as chemists well 
know, is hut slightly acted upon by dilute sulphuric acid in comparison with 
ordinary zinc, which during the action is subject to an infinity of voltaic 
actions. See I)e la Rive on this subject, Bibliotheque UniVerselle, 1 830, p. JOE 

t The acid was left during a night with a small piea$ of unamalgfth^ted 
zinc in it, for the purpose of evolving such air as might be incline^ to separate, 
and bringing the whole into a constant state, 



255 


Jan, 1834.] Voltaic decomposition of water. 

were washed in distilled water, dried, and reweighed. Plate B 
weighed 148 '3 grains, as before, having lost nothing by the 
direct chemical action of the acid. Plate A weighed 151*65 
grains, 8*45 grains of it having been oxidized and dissolved 
during the experiment. 

8G6. The hydrogen gas was next transferred to a water- 
trough and measured ; it amounted to 12*5 cubic inches, the 
temperature being 52°, and the barometer 29*2 inches. This 
quantity, «orrected for temperature, pressure, and moisture, 
becomes 12*15453 cubic inches of dry hydrogen at mean tem- 
perature and pressure ; which, increased by one half for the oxy- 
gen that must have gone to the anode , i.e. to the zinc, gives 
18*232 cubic inches as the quantity of oxygen and hydrogen 
evolved from the water Recomposed by the electric curicnt. 
According to the estimate of the weight of the mixed gas before 
adopted (791.), this volume is equal to 2*35355 1 i grains, winch 
therefore is the weight of water decomposed ; an<j this quantity 
is to 8*45, the quantity of zinc oxidized, as 9 is to 32*31. Now 
taking 9 as the equivalent number of water, the number 32*5 is 
given as the equivalent number of zinc ; a coincidence suf- 
ficiently near to show, wliat indeed could not but happen, that 
for an equivalent of zinc oxidized an equivalent of water must 
be decomposed*. 

867. But let us observe how the water is decomposed. It 
is electrolyzed, i.e is decomposed voltaically, and not in the 
ordinary manner (as to appearance) of chemical decompositions; 
for the oxygen appears at the anode and the hydrogen at the cath- 
ode of the body under decomposition, and these were in many 
parts of the experiment above an inch asunder. Again, the ordi- 
nary chemical affinity wa$*not enough under the circumstances 
to effect the decomposition of the water, as was abundantly 
proved by the inaction on plate B; the voltaic current was essen- 
tial. And to prevent any idea that the chemical affinity was 
almost sufficient to decompose the water, and that a smaller 
current of electricity might under the circumstances, cause the 
hydrogen to pass to the cathode , I need only refer to the results 
which I have given {807. 813.) to show that the chemical action 
^^plectrodes -has not the slightest influence over the quanti- 
#e#t»C5water or other substances decomposed between them, but 
* The experiment was repeated several times with the same results. 



256 Quantity of electric force in matter . [Series VII. 

that they are entirely dependent upon the quantity of electricity 
which passes. 

868. What, then, follows as a necessary consequence of the 
whole experiment ? Why, this : that the chemical action upon 
32*31 parts, or one equivalent of zinc, in this simple voltaic 
circle, was able to evolve such quantity of electricity in the form 
of a current, as passing through water, should decompose 9 
parts, or one equivalent of that substance : And considering 
the definite relations of electricity as developed in the preceding 
parts of the present paper, the results prove that the quantity 
of electricity which, being naturally associated with the particles 
of matter, gives them their combining power, is able, when thrown 
into a current, to separate those particles from their state of 
combination; or, in other words, thaj the electricity which- de- 
composes, and that which is evolved by the decomposition of, a 
certain quantity of matter, are alike, 

869. The harmony which this theory of the definite evolution 
and the equivalent definite action of electricity introduces into 
the associated theories of definite proportions and electro- 
chemical affinity, is very great. According to it, the equivalent 
weights of bodies are simply those quantities of them which 
contain equal quantities of electricity, or have naturally equal 
electric powers ; it being the electricity which determines the 
equivalent number, because it determines the combining force. 
Or, if we adopt the atomic thebry or phraseology, then the atoms 
of bodies which are equivalents to each other in their ordinary 
chemical action, have equal quantities of electricity naturally 
associated with them. But I must confess I am jealous of the 
term atom ; for though it is very easy to talk of atoms, it is 
very difficult to form a clear idea of their nature, especially 
when coinpormd bodies are under consideration. 

870. I cannot refrain from recalling here the beautiful idea 
put forth, I believe, by Berzelius (703.). in his development of 
his views of the electro-chemical theory of affinity, that the heat 
and light evolved during cases of powerful combination are the 
consequence of the electric discharge which is at the moment 
taking place. The idea is in perfect accordance with the view 
I have taken of the quantity of electricity associated with the 
particles of matter. 

871. In this exposition of the law of the definite action of 



257 


Jan. 1834] Definite electro-chemical action. 

electricity, and its corresponding definite proportion in the par- 
ticles of bodies, I do not pretend to have brought, as yet, every 
case of chemical or electro- chemical action under its dominion. 
There are numerous considerations of a theoretical nature, 
especially respecting the compound particles of matter and the 
resulting electrical forces which they ought to possess, which I 
hope - will gradually receive their development ; and there are 
numerous experimental cases, as, for instance, those of com- 
pounds formed by weak affinities, the simultaneous decompo- 
sition of water and salts, &c., which still require investigation. 
But' whatever the results on these and numerous other points 
may be, I do not believe that the facts which I have advanced, 
or even the general laws deduced from them, will suffer any 
sei’ious change ; and they arc of sufficient importance to justify 
their publication, though much may yet remain imperfect or 
undone. Indeed, it is the great beauty of our science, chemis- 
try, that advancement in it, whether in a degree great or 
small, instead of exhausting the subjects of research, opens the 
doors to further and more abundant knowledge, overflowing 
with beauty and utility, to those who will be at the easy personal 
pains of undertaking its experimental investigation. 

872. The definite production of electricity (808.) in associa- 
tion with its definite action proves, I think, that the current of 
electricity in the voltaic pile is sustained by chemical decompo- 
sition, or rather by chemical action, and not by contact only. 
But here, as elsewhere (857.), I beg to reserve my opinion 
as to the real action of contact, not having yet been able to 
make up my mind as to whether it is an exciting cause of the 
current, or merely necessary to allow of the conduction of elec- 
tricity, otherwise generated, from one metal to the other. 

873. But admitting that chemical action is the source of 
electribity,what an infinitely small fraction of that which is active 
do we obtain and employ in our voltaic batteries ! Zinc and 
platina wires, one eighteenth of an inch in diameter and about 
half an inch long, dipped into dilute * sulphuric acid, so weak 
th&t it is not sensibly sour to the tongue, or scarcely to our 
most delicate test papers, will evolve more electricity in one 
twentieth of a minute (860.) than any man would willingly allow 
to pass through his body at once. The chemical action of a 
grain of -water upon four grains of zinc can evolve electricity 



258 Definite electro-chemical action* [Series VII. 

equal in , quantity to that of a powerful thunder-storm (868. 
861 .) . Nor is it merely true that the quantity is active ; it can 
be directed and made to perform its full equivalent duty (867. 
&c.). Is there not, then,, great reason to hope and believe 
that, by a closer experimental investigation of the principles 
which govern the development and action of this subtile agent, 
we shall be able to increase the power of our batteries, or invent 
new instruments which shall a thousandfold surpass in energy 
those which we at present possess ? 

874. PI ere for a while I must leave the consideration of the 
definite chemical action of electricity . But before I dismiss 
this series of experimental Researches, I would call to mind 
that, in a former series, I showed the current of electricity was 
also definite in its magnetic action (216. 366. 367. 376. 377.) ,* 
and, though this result was not pursued to any extent, I have 
no doubt that the success which has attended the development 
of the chemical effects is not more than would accompany an 
investigation of the magnetic phenomena. 

Royal Institution , 

December 31 st, 1833. 



259 


EIGHTH SERIES. 

§ 14. On the Electricity of the Voltaic Pile ; its source , quan- 
tity y intensity, and general characters, i. On simple Vol- 
taic Circles . 1[ ii. On the intensity necessary for Electro- 

lyzation. IT iii. On associated Voltaic Circles, or the Vol- 
taic Battery . ^f iv. On the resistance of an Electrolyte to 
Electrolytic action. If v. General remarks on the active 
Voltaic Battery. 

Received April 7. — Read June 5, 

If i. On simple Voltaic Circles. 

875. The great question* of the source of electricity in the vol- 
taic pile has engaged the attention of sc> many eminent philoso- 
phers, that a man of liberal mind and able to appreciate their 
powers would probably conclude, although he might not have 
studied the question, that the truth was somewhere revealed. 
But if in pursuance of this impression he w ere induced to enter 
upon the work of collating results and conclusions, he would 
find such contradictory evidence, such equilibrium of opinion, 
such variation and combination of theory, as would leave him 
in complete doubt respecting what he should accept as the 
true interpretation of nature : he would be forced to take upon 
himself the labour of repeating and examining the facts, and 
then use his own judgement on them in preference to that of 
others. 

876. This state ot the subject must, to those who have made 
up their minds on the matter, be my apology for entering upon 
its investigation. The views 1 have taken of the definite action 
of electricity in decomposing bodies (783.), and the identity of 
the power so used with the power to be overcome (855 .), founded 
not on a mere opinion or general notion, but on facts which, 
being altogether pew, were to my mind precise and conclusive, 
gave me, as I conceived, the power of examining the question 
with advantaged not before possessed by any, and which might 
compensate, on my part, for the superior clearness and extent 

s 2 



260 


Electricity of the voltaic pile. [Series VIII. 

of intellect on theirs. Such are the considerations which have 
induced me to suppose I might help in deciding the question, 
and be able to render assistance in th^t great service of remov- 
ing doubtful knowledge . Such knowledge is the early morning 
light of every advancing science, and is essential to its develop- 
ment ; but the man who is engaged in dispelling that which 
is deceptive in it, anfl revealing more clearly that which 
is true, is as useful in his place, and as necessary to the general 
progress of the science, as he who first broke through the in- 
tellectual darkness, and opened a path into knowledge before 
unknown to man. 

877. The identity of the force constituting the voltaic current 
or electrolytic agent, with that which holds the elements of elec- 
trolytes together (855.), or in other words with chemical affinity, 
seemed to indicate that the electricity of the pile itself w r as 
merely a mode of exertion, or exhibition, or existence of true 
chemical action , or rather of its cause ; and I have consequently 
already said that I agree with those who believe that the supply 
of electricity is due to chemical powers (857.). 

878. But the great question of whether it is originally due 
to metallic contact or to chemical action, i. e . whether it is the 
first or the second which originates and determines the current, 
was to me still doubtful ; and the beautiful and simple experi- 
ment with amalgamated zinc ;and platina, which I have descri- 
bed minutely as to its results (863, &c.), did not decide the 
point ; for in that experiment the chemical action does not take 
place without the contact of the metals, and the metallic con- 
tact is inefficient without the chemical action. Hence either 
might be looked upon as the determining cause of the current, 

879. I thought it essential to decide thi& question by the 
simplest possible forms of apparatus and experiment, that no 
fallacy might be inadvertently admitted. The well known diffi- 
culty of effecting decomposition by a single pair of plates, ex- 
cept in the fluid exciting them into action (863.), seemed to 
throw insurmountable obstruction in the way of such experi- 
ments ; but I remembered the easy decomposabhity of the solu- 
tion of iodide of potassium (316.) and seeing no theoretical 
reason, if metallic contact was not essentialf why true electro- 
decomposition should not be obtained without it, even in a single 
circuit, I persevered and succeeded. 



April 1834.] obtained without contact of metals . 261 

880. A plate of zinc, about eight inches long and half an inch 
wide, was cleaned and bent in the middle to a right angle, fig. 
73 a. Plate VI. A plat^ of platina, about three inches long and 
half an inch wide, was fastened to a platina Avirc, and the latter 
bent as in the figure, b . These two pieces of metal were arranged 
together as delineated, but as yet without the vessel c, and 
its contents, which consisted of dilute sulphuric acid mingled 
with a little nitric acid. At x a piece of folded bibulous 
paper, moistened in a solution of iodide of potassium, was placed 
on the zinc, and was pressed upon by the end of the platina 
wire. When under these circumstances the plates were dipped 
into the acid of the vessel c } there was an immediate effect at 
x y the iodide being decomposed, and iodine appearing at the 
anode (663.), i. e . against the end of the platina wire. 

881. As long as the lower ends of the plates remained in the 
acid the electric current continued, and the decomposition pro- 
ceeded at x. On removing the end of the wire from place to 
place on the paper, the effect was evidently very powerful ; and 
on placing a piece of turmeric paper between the white paper 
and zinc, both papers being moistened with the solution of 
iodide of potassium, alkali was evolved at the cathode (663.) 
against the zinc, in proportion to the evolution of iodine at the 
anode . Hence the decomposition was perfectly polar, and dc- 
cidedly dependent upon a current of electricity passing from 
the zinc through the acid to the platina in the vessel c , and 
back from the platina through the solution to the zinc at the 
paper x . 

882. That the decomposition at x was a true electrolytic ac- 
tion, due to a current determined by the state of things in the 
vessel c, and not dependent upon any mere direct chemical ac- 
tion of the zinc and platina on the iodide, or even upon any 
current which the solution of iodide might by its action on 
those metals tend to form at x, was shown, in tho first place, 
by removing the vessel c and its acid from the plates, when all 
decomposition at x ceased, and in the next by connecting the 
metals, either in or 'out of the acid, together, when decompo- 
sition of the iodide at x occurred, but in a reverse order ; for 
now alkali appeared against the end of the platina wire, and 
the iodine passed to the zinc, the current being the contrary 
of what it was in the former instance, and produced directly by 



262 Decomposition by a pair of plates. [Series VIII, 

the difference of action of the solution in the paper on the two 
metals. The iodine of course combined with the zinc. 

883. When this experiment was m^de with pieces of zinc 
amalgamated over the whole surface (863.), the results were 
obtained with equal facility and in the same direction, even 
when only dilute sulphuric acid was contained in the vessel c 
(fig. 73.) . Whichsoever end of the zinc was immersed in the 
acid, still the effects were the same : so that if, for a moment, 
the mercury might be supposed to supply the metallic contact, 
the inversion of the amalgamated piece destroys that objec- 
tion. The use of unamalgamated zinc (880.) removes all pos- 
sibility of doubt*. 

884. When, in pursuance of other views (930.), the vessel c 
was made to contain a solution of ehustic potash in place of 
acid, still the same results occurred. Decomposition of the 
iodide was effected freely, though there was no metallic con- 
tact of dissimilar metals, and the current of electricity was in 
the same direction as when acid was used at the place of ex- 
citement. 

885. Even a solution of common salt in the glass c could 
produce all these effects. 

886. Having made a galvanometer with platina wires, and 
introduced it into the course of the current between the pla- 
tina plate and the place of decomposition x, it was affected, 
giving indications of currents in the same direction as those 
shown to exist by the chemical action. 

887. If we consider these results generally, they lead to very 
important conclusions. In the first place, they prove, in the 

* The fallowing is a more striking mode of making the above elementary 
experiment. Prepare a plate of zinc, ten or twelve inches long and two inches 
wide, and clean it thoroughly : provide also two discs of clean platina, about 
one inch and a half in diameter : — dip three or four folds of bibulous paper 
into a strong solution of iodide of potassium, place them on the clean zinc at 
one end of the plate, and put on them one of the platina discs : finally dip 
similar folds of paper or a piece of linen cloth into a mixture of equal parts 
nitric acid and water, and place it at the other end of the zinc plate with the 
second platina disc upon it. In this state of things no change at the solution 
of the iodide will be perceptible ; but if the two discs be connected by a platina 
(or any other) wire for a second or- two, and then that oyer the iodide be 
raised, it will be found that the whole of the surface beneath is deeply stained 
with evolved iodine. — Dec. 1838. 



April 1834.] Voltaic current without metallic contact . 263 

most decisive manner, that metallic contact is not necessary for 
the production of the voltaic current. In the next place, they 
show a most extraordinary mutual relation of the chemical affi- 
nities of the fluid which excites the current, and the fluid w hich 
is decomposed by it. 

8.88, For the purpose of simplifying the consideration, let us 
take the experiment with amalgamated zinc. The metal so 
prepared exhibits no effect until the current can pass : it at 
the same time introduces no new action, but merely removes an 
influence which is extraneous to those belonging either to* the 
production or the effect of the electric current under investiga- 
tion (1000.) ; an influence also which, when present, tends only 
to confuse the results. 

889. Let two plates, one of amalgamated zinc and the other 
of platina, be placed parallel to each other (fig. 74.), and intro- 
duce a drop of dilute sulphuric acid, y , between them at one 
end ; there will be no sensible chemical action at that spot un- 
less the two plates are connected somewhere else, as at P 
by a body capable of conducting electricity. If that body be 
a metal or certain forms of carbon, then the current passes, 
and, as it circulates through the fluid at y, decomposition 
ensues. 

890. Then remove the acid from y , and introduce a drop of 
the solution of iodide of potassium at x (fig. 75.). Exactly the 
same set of effects occur, except that when the metallic com- 
munication is made at P Z, the electric current is in the oppo- 
site direction to what it was before, as is indicated by the 
arrows, which show the courses of the currents (667.). 

891. Now both the solutions used are conductors, but the 
conduction in them is essentially connected with decomposition 
(858.) in a certain eonstant order, and therefore the appearance 
of the elements in certain places shows in what direction a cur- 
rent has passed when the solutions are thus employed. More- 
over, we find that when they are used at opposite ends of the 
plates, as in the last two experiments (889. 890.), metallic con- 
tact being allowed at the other extremities, the currents are in 
opposite directions. We have evidently, therefore, the power 
of Opposing the actions of the two fluids simultaneously to each 
other at the opposite ends of the plates, using each one as a 
conductor for the discharge of the current of electricity, which 



264 Use of metallic contact , [Series VIII. 

the other tends to generate ; in fact, substituting them for me- 
tallic contact, and combining both experiments into one (fig. 
76.). Under these circumstances, tlfere is an opposition of 
forces : the fluid, which brings into play the stronger set of 
chemical affinities for the zinc, (being the dilute acid,) over- 
comes the force of the other, and determines the formation and 
direction of the electric current ; not merely making that cur- 
rent pass through the weaker liquid, but actually reversing the 
tendency which the elements of the latter have in relation to 
the zinc and platina if not thus counteracted, and forcing them 
in the contrary direction to that they are inclined to follow, 
that its own current may have free course. If the dominant 
action at y be removed by making metallic contact there, then 
the liquid at x resumes its power; or if the metals be not 
brought into contact at y> but the affinities of the solution there 
weakened, whilst those active at x are strengthened, then the 
latter gains the ascendency, and the decompositions are pro- 
duced in a contrary order. 

892. Before drawing a final conclusion from this mutual de- 
pendence and state of the chemical affinities of two distant 
portions of acting fluids (916.), I will proceed to examine more 
minutely the various circumstances under which the re-action of 
the body suffering decomposition is rendered evident upon the 
action of the body, also undergoing decomposition, which pro- 
duces the voltaic current. 

893. The use of metallic contact in a single pair of plates, and 
the cause of its great superiority above contact made by other 
kinds of matter, become now very evident. When an amalga- 
mated zinc plate is dipped into dilute sulphuric acid, the force 
of chemital affinity exerted between the metal and the fluid is 
not sufficiently powerful to cause sensible action at the surfaces 
of contact, and occasion the decomposition of water by the oxi- 
dation of the metal, although it is sufficient to produce such a 
condition of the electricity (or the power upon which chemical 
affinity depends) as would produce a current if there were a 
path open for it (916. 956.) ; and that current would complete 
the conditions necessaiy, under the circumstances, for the de- 
composition of the water. 

894. Now the presence of a piece of platina touching both 
the zinc and the fluid to.be decomposed; opens the path re- 



April 1834.] Opposed distant chemical actions . 265 

quired for the electricity. Its direct communication with the 
zinc is effectual, far beyond any communication made between 
it and that metal, ( i . e. between the platina and zinc,) by means 
of decomposable conducting bodies, or, in other words, elec- 
trolytes , as in the experiment already described (891.) ; be- 
cause, when they are used, the chemical affinities between them 
and the zinc produce a contrary and opposing action to that 
which is influential in the dilute sulphuric acid ; or if that action 
be but small, still the affinity of their component parts for each 
other has to be overcome, for they cannot conduct without suf- 
fering decomposition ; and this decomposition is found experi- 
mentally to re-act back upon the forces which in the acid tend 
to produce the current (904. 910. &c.), and in numerous cases 
entirely to neutralize them. Where direct contact of the zinc 
and platina occurs, these obstructing forces are not brought 
into action, and therefore the production and the circulation of 
the electric current and the concomitant action of decomposi- 
tion are then highly favoured. 

895. It is evident, however, that one of these opposing 
actions may be dismissed, and yet an electrolyte be used for the 
purpose of completing the circuit between the zinc and platina 
immersed separately into the dilute acid ; for if, in fig. 73, the 
platina wire be retained in metallic contact with the zinc plate 
a, at x, and a division of the platina be made elsewhere, as at s , 
then the solution of iodide placed there, being in contact with 
platina at both surfaces, exerts no chemical affinities for that 
metal ; or if it does, they are equal on both sides. Its power, 
therefore, of fdrming a current in opposition to that depend- 
ent upon the action of the acid in the vessel c,,is removed, and 
only its resistance to decomposition remains as the obstacle 
to be overcome by the affinities exerted in the dilute sulphuric 
acid. 

896. This becomes the condition of a single pair of active 
plates where metallic contact is allowed. In such cases, only 
one set of opposing affinities are to he overcome by those 
which are dominant in the vessel c; whereas, when metallic 
contact is not allowed, two sets of opposing affinities must be 
conquered (894.). 

897. It has been considered a difficult, and by some an im- 
possible thing, to decompose bodies by the current 4rom a 



266 Electrolyzation by a pair of plates, [Series YIII. 

single pair of plates, even when it was so powerful as to heat 
bars of metal red hot, as in the case of Harems calorimeter, ar- 
ranged as a single voltaic circuit, or pf Wollaston^s powerful 
single pair of metals. This difficulty has arisen altogether from 
the antagonism of the chemical affinity engaged in producing 
the current with the chemical affinity to be overcome, and de- 
pends entirely upon the relative intensity ; for when the sum 
of forces in one has a certain degree of superiority over the 
sum of forces in the other, the former gain the ascendency, 
determine the current, and overcome the latter so as to make 
the substance exerting them yield up its elements in perfect ac- 
cordance, both as to direction and quantity, with the course of 
those which are exerting the most intense and dominant action. 

898. Water has generally been the 'substance, the decompo- 
sition of which has been sought for as a chemical test of the 
passage of an electric current. But I now began to perceive a 
reason for its failure, and for a fact which I had observed long 
before (315. 316.) with regard to the iodide of potassium, 
namely, that bodies would differ in facility of decomposition by 
a given electric current, according to the condition and inten- 
sity of their ordinary chemical affinities. This reason appeared 
in their re-action upon the affinities tending to cause the cur- 
rent ; and it appeared probable, that many substances might 
be found which could be decomposed by the current of a single 
pair of zinc and platina plates immersed in dilute sulphuric 
acid, although water resisted its action. I soon found this to 
be the case, and as the experiments offer new and beautiful 
proofs of the direct relation and opposition of the chemical af- 
finities concerned in producing and in resisting the stream of 
electricity, I shall briefly describe them. 

899. The arrangement of the apparatus was as in , fig. 77. 
The vessel v contained dilute sulphuric acid ; Z and P are the 
zinc and platina plates ; a , b y and c are platina wires ; the de- 
compositions were effected at x , and occasionally, indeed 
generally, a galvanometer was introduced into the circuit at g : 
its place onty'is here given, the circle at g having no reference 
to the size of the instrument. Various arrangements were 
made at a?, according to the kind of decomposition to be effected. 
If a drop of liquid was to be acted upon, the two ends were 
merely dipped into it ; if a solution contained in the pores of 



267 


April 1834.] Iodide of potassium : — chlorides , 

paper was to be decomposed, one of the extremities was con- 
nected with a platina plate supporting the paper, whilst the 
other extremity rested on the paper, p, fig. 84 : or sometimes, 
as with sulphate of soda, a plate of platina sustained two por- 
tions of paper, one of the ends of the wires resting upon each 
piece, c , fig. 86. The darts represent the direction of the elec- 
tric current (667.) . 

900. Sqjiution of iodide of potassium , in moistened paper, 
being placed at the interruption of the circuit at x, was readily 
decomposed. Iodine was evolved at the anode , and alkali at 
the cathode , of the decomposing body. 

901. Protochhride of tin, when fused and placed at x, was 
also readily decomposed, yielding perchloride of tin at the 
anode (779.), and tin at the cathode. 

902. Fused chloride of silver, placed at x, was also easily 
decomposed ; chlorine was evolved at the anode , and brilliant 
metallic silver, either in films upon the surface of the liquid, or 
in crystals beneath, evolved at the cathode. 

903. Water acidulated with sulphuric acid, solution of mu- 
riatic acid, solution of sulphate of soda, fused nitre, and the 
fused chloride and iodide of lead were not decomposed by this 
single pair of plates, excited only by dilute sulphuric acid. 

904. These experiments give abundant proofs that a single 
pair of plates can electrolyze bodies and separate their ele- 
ments. They also show in a beautiful manner the direct rela- 
tion and opposition of the chemical affinities concerned at the 
two points of action. In those cases where the sum of the op- 
posing affinities? at x, was sufficiently beneath the sum of the 
acting affinities in v decomposition took place; but in those 
cases where they rose higher, decomposition was effectually re- 
sisted and the current ceased to pass (891.). 

905. It is however, evident, that the sum of acting affinities 
in v may be increased by using other fluids than dilute sulphu- 
ric acid, in which latter case, as I believe, it is merely the af- 
finity of the ainc for the oxygen already combined with hydro- 
gen in the w&ter that is exerted in producing the electric current 
(919.) ; and when the affinities are so increased, the view I am 
supporting leads to the conclusion, that bodies which resisted 
in the preceding experiments would then be decomposed, be- 
cause 6f the increased difference between their affinities and 



268 


Intensity of one pair increased. [Series VIII, 

the acting affinities thus exalted. This expectation was fully 
confirmed in the following manner. 

906. A little nitric acid was added tp the liquid in the vessel 
v, so as to make a mixture which I shall call diluted nitro-sul- 
phuric acid. On repeating the experiments with this mixture, 
all the substances before decomposer! again gave way, and 
much more readily. But, besides that, many which before re- 
sisted electrolyzation now yielded up their elements. Thus, 
solution of sulphate of soda, acted upon in the interstices of lit- 
mus and turmeric paper, yielded acid at the anode and alkali 
at the cathode ; solution of muriatic acid tinged by indigo 
yielded chlorine at the anode and hydrogen at the cathode ; so- 
lution of nitrate of silver yielded silver at the cathode. Again, 
fused nitre and the fused iodide and chloride of lead were de- 
composable by the current of this single pair of plates, though 
they were not by the former (903.). 

907. A solution of acetate of lead was apparently not decom- 
posed by this pair, nor did water acidulated by sulphuric acid 
seem at first to give way (973.). 

908. The increase of intensity or power of the current pro- 
duced by a simple voltaic circle, with the increase of the force 
of the chemical action at the exciting place, is here sufficiently 
evident. But in order to place it in a clearer point of view, and 
to show that the decomposing effect was not at all dependent, 
in the latter cases, upon the mere capability of evolving more 
electricity, experiments were made in which the quantity 
evolved could be increased without variation in the intensity of 
the exciting cause. Thus the experiments in which dilute sul- 
phuric acid was used (899.) were repeated, using large plates 
of zinc aqd platina in the acid ; but still those bodies which re- 
sisted decomposition before, resisted it also under these new 
circumstances. Then again, where nit ro -sulphuric acid was 
used (906.), mere wires of platina and zinc were immersed in 
the exciting acid ; yet, notwithstanding this change, those 
bodies were now decomposed which resisted any current tending 
to be formed by the dilute sulphuric acid. For instance, mu- 
riatic acid could not be decomposed by a single pair of plates 
when immersed in dilute sulphuric acid ; nor did making the 
solution of sulphuric acid strong, nor enlarging the ’size of the 
zinc and platina plates immersed in it, increase the power ; but 



April 1834.] Distant chemical actions connected . 269 

if to a weak sulphuric acid a very little nitric acid was added, 
then the electricity evolved had power to decompose the mu- 
riatic acid, evolving chlorine at the anode and hydrogen at the 
cathode, even when mere wires of metals were used. This mode 
of increasing the intensity of the electric current, as it excludes 
the effect dependent upon many pairs of plates, or even the 
effect of making any one acid stronger or weaker, is at once re- 
ferable to the condition and force of the chemical affinities which 
are brougfft into action, and may, both in principle and practice, 
be considered as perfectly distinct from any other inode. 

909. The direct reference which is thus experimentally made 
in the simple voltaic circle of the intensity j of the electric cur- 
rent to the intensity of thfc chemical action going on at the place 
where the existence and direction of the current is determined, 
leads to the conclusion that by using selected bodies, as fused 
chlorides, salts, solutions of acids, &e., which may act upon 
the metals employed with different degrees of chemical force; 
and using also metals in association with platina, or with each 
other, which shall differ in the degree of chemical action ex- 
erted between them and the exciting fluid or electrolyte, we 
shall be able to obtain a series of comparatively constant effects 
due to electric currents of different intensities, which will serve 
to assist in the construction of a scale competent to supply the 
means of determining relative degrees of intensity w r ith accuracy 
in future researches *. 

910. I have already expressed the view which I take of the 
decomposition iti the experimental place, as being the direct 
consequence of the superior exertion at some other spot of the 
same kind of power as that to be overcome, and therefore as 
the result of an antagonism of forces of the same nature (891. 
904.) . Those at the place of decomposition have a re- action 
upon, and a power over, the exerting or determining set pro- 
portionate to what is needful to overcome their own power; 
and hence a curious result of resistance offered by decompo- 
sitions to " the original determining force, and consequently to 
the current. This is well shown in the eases where such bodies 

* In relation to this difference and its probable cause, see considerations on 
inductive polarization, 1354, &c. — Dec, 1838. 



270 Elementary voltaic forces. [Series VIII. 

as chloride of lead, iodide of lead, and water would not decom- 
pose with the current produced by a single pair of zinc and 
plRtina plates in sulphuric acid (903.), although they would with 
a current of higher intensity produced by stronger chemical 
powers. In such cases no sensible portion of the current 
passes (967.) ; the action is stopped; and I am now of opinion 
that in the case of the law of conduction which I described in 
the Fourth Series of these Researches (413.), the bodies which 
are electrolytes in the fluid state cease to be such ill the solid 
form, because the attractions of the particles by which they are 
retained in combination and in their relative position, are then 
too powerful for the electric current*. The particles retain 
their places ; and as decomposition is prevented, the transmis- 
sion of the electricity is prevented alstj ; and although a battery 
of many plates may be used, yet if it be of that perfect kind 
which allows of no extraneous or indirect action (1P00.), the 
whole of the affinities concerned in the activity of that battery 
are at the same time also suspended and counteracted. 

911. But referring to the resistance of each single case of 
decomposition, it would appear that as these differ in force ac- 
cording to the affinities by which the elements in the substance 
tend to retain their places, they also would supply cases con- 
stituting a series of degrees by which to measure the initial in- 
tensities of simple voltaic or other currents of electricity, and 
which, combined witlf the scale of intensities determined by 
different degrees of acting force (909.), would probably include 
a sufficient set of differences to meet almost every important 
case where a reference to intensity would be required. 

912, According to the experiments I have already had occa- 
sion to ipake, I And that the following bodies are electrolytic 
in the order in which I have placed them, those which are first 
being decomposed by the current of lowest intensity. These 
currents were always from a single pair of plates, and may be 
considered as elementary voltaic forces. 

Iodide of potassium (solution). 

Chloride of silver (fused) . 

Protochloride of tin (fused) . 

Chloride of lead (fused) . 

Iodide of lead (fused) . 

* Refer onwards to 1705. — Dec. 1838/ 



Apeil 1834.] Electrolytic intensity . 271 

Muriatic acid (solution). 

Water, acidulated with sulphuric acid. 

913. It is essential that, in all endeavours to obtain the rela- 
tive electrolytic intensity necessary for the decomposition of 
different bodies, attention should be paid to the nature of the 
electrodes and the other bodies present which may favour se- 
condary actions (986.) . If in electro-dccomposition one of the 
elements separated has an affinity for the electrode, or for 
bodies present in the surrounding fluid, then the affinity re- 
sisting decomposition is in part balanced by such power, and 
the true place of the^ electrolyte in a table of the above kind is 
not obtained : thus, chlorine combines with a positive platina 
electrode freely, but iodine scarcely at all, and therefore I be- 
lieve it is that the fused .chlorides stand flrst in the preceding 
Table. Again, if in the decomposition of water not merely 
sulphuric but also a little nitric acid be present, then the water 
is more freely decomposed, for the hydrogen at the cathode is 
not ultimately expelled, but finds oxygen in the nitric acid, with 
which it can combine to produce a secondary result ; the affi- 
nities opposing decomposition are in this way diminished, and 
the elements of the water can then be separated by a current 
of lower intensity. 

914. Advantage may be taken of this principle to interpolate 
more minute degrees into the scale of initial intensities already 
referred to (909. 911.) than is there spoken of; for by com- 
bining the force of a current constant in its intensity, with the 
use of electrodes consisting of matter, having more or less af- 
finity for the elements evolved from the decomposing electro- 
lyte, various intermediate degrees may be obtained. 

915. Returning to the consideration of the source of elec- 
tricity (878. &c.), there is another proof of tile most perfect 
kind that metallic contact has nothing to do with the production 
of electricity in the voltaic circuit, and further, that electricity 
is only another mode of the exertion of chemical forces. It is, 
the production of the electric spark before any contact of 
metals is made, and by the exertion of pure and unmixed chemi- 
cal forem* The experiment, which will be described further 
on (&!$.);, consists in obtaining the spark upon making contact 
between a plate of zinc and a plate of copper plunged into di- 



272 Electricity of the voltaic pile . [Series YIII. 

lute sulphuric acid. In order to make the arrangement as ele- 
mentary as possible, mercurial surfaces were dismissed, and the 
contact made by a copper wire connected with the copper plate, 
and then brought to touch a clean pa^t of the zinc plate. The 
electric Spark appeared, and it must of necessity have existed 
and passed before the zinc and the copper were in contact . 

916. In order to render more distinct the principles which I 
have been endeavouring to establish, I will restate tlfem in their 
simplest form, according to my present belief. The electricity 
of the voltaic pile (856. note) is not dependent either in its ori- 
gin or its continuance upon the contact of the metals with each 
other (880. 915.). It is entirely due to chemical action (8.82.), 
and is proportionate in its intensity to the intensity of the 
affinities concerned in its production (908.) ; and in its quantity 
to the quantity of matter which has been chemically active 
during its evolution (869.) . This definite production is again 
one of the strongest proofs that the electricity is of chemical 
origin. 

917. As volta-electro-generation is a case of mere chemical 
action, so volta-electro-decomposition is simply a case of the 
preponderance of one set of chemical affinities more powerful 
in their nature, over another set which are less powerful : and 
if the instance of two opposing sets of such forces (891.) be 
considered, and their mutual relation and dependence borne in 
mind, there appears no necessity for using, in respect to such 
cases, any other term than chemical affinity, (though that of 
electricity may be very convenient,) or siipposing any new agent 
to be concerned in producing the results ; for we may consider 
that the. powers at the two places of action are in direct com- 
munion and balanced against each other through the medium 
of the metals (891.), fig. 76, in a manner analogous to that in 
which mechanical forces are balanced against each other by the 
intervention of the lever (1031.). 

918. All the facts show us that that power commonly called 
chemical affinity, can be communicated to a distance through 
the metals and certain forms of carbon ; that the electric cur- 
rent is only another form of the forces of chemical Affinity ; that 
its power is in proportion to the chemical affinities produe|ng it ; 
that when it is deficient in force it may be helped by calling in 



April 1831-.] Chemical origin of the power of the pile. 273 

chemical aid, the want in the former being made up by an 
equivalent of the latter ; that, in other words, the forces termed 
chemical affinity and electricity are one and the same. 


919. When the circumstances connected with the production 
of electricity in the ordinary voltaic circuit are examined and 
compared, it appears that the source of that agent, always 
meaning Mie electricity which circulates and completes the cur- 
rent in the voltaic apparatus, and gives that apparatus power 
and character (947. 996.), exists in the chemical action which 
takes place directly between the metal and the body with which 
it combines, and not at all in the subsequent action of the sub- 
stance so produced with Jhe acid present *. Thus, when zinc, 
platina, and dilute sulphuric acid arc used, it is the union of 
the zinc with the oxygen of the water which determines the 
current; and though the acid is essential to the removal of the 
oxide so formed, in order that another portion of zinc may act 
on another portion of water, it docs not, by combination with 
that oxide, produce any sensible portion of the current of elec- 
tricity which circulates ; for the quantity of electricity is de- 
pendent upon the quantity of zinc oxidized, and in definite 
proportion to it : its intensity is in proportion to the intensity 
of the chemical affinity of the zinc for the oxygen under the 
circumstances, and is*scarccly, if* at all, affected by the use of 
either strong or weak acid (908.). 

920. Again, if zinc, platina, and muriatic acid are used, the 
electricity appear^ to be dependent upon the affinity of the zinc 
for the chlorine, and to be circulated in exact proportion to the 
number of particles of zinc and chlorine which unite, being in 
fact an equivalent to them. 

921. But in considering this oxidation, or other direct action 
upon the metal itself, as the cause and source of the electric 
current, it is of the utmost importance to observe that the oxy- 
gen or other body must be in a peculiar condition, namely, in 
the state q£ combination ; and not only so, but limited still fur- 
ther td such a state of combination and in such proportions as 
Will constitute an electrolyte (823.) . A pair of zinc and platina 
plates cannot be so arranged in oxygen gas as to produce a 

* Wollaston, Philosophical Transactions, 1801, p. 427. 



2 74 Necessity of an electrolyte in the pile . [Series VIII. 

current of electricity, or act as a voltaic circle, even though the 
temperature may be raised so high as to cause oxidation of the 
zinc, far more rapidly than if the pair^ of plates were plunged 
into dilute sulphuric acid ; for the oxygen is not part of an elec- 
trolyte, and cannot therefore conduct the forces onwards by 
decomposition, or even as metals do by itself. Or if its gaseous 
state embarrass the minds of some, then liquid chlorine may 
be taken. It does not excite a current of electricity through 
the two plates by combining with the zinc, for its particles can- 
not transfer the electricity active at the point of combination 
across to the platina. It is not a conductor of itself/ like the 
metals ; nor is it an electrolyte, so as to be capable of conduction 
during decomposition, and hence there is simple chemical action 
at the spot, and no electric current* 

922. It might at first be supposed that a conducting body, 
not electrolytic, 'might answer as the third substance between 
the zinc and the platina ; and it is true that we have some such 
capable of exerting chemical action upon the metals. They 
must, however, be chosen from the metals themselves, for there 
arc no bodies of this kind except those substances and char- 
coal. To decide the matter by experiment, I made the follow- 
ing arrangement. Melted tin was put into a glass tube bent 
into the form of the letter V, fig. 78, so as to fill the half of 
each limb, and two pieces of tjiick platina wire, p, w , inserted, 
so as to have their ends immersed some depth in the tin : the 
whole was then allowed to cool, and the ends p and w connected 
with a delicate galvanometer. The part of the tube at % was 
now reheated, whilst the portion y was retained cool. The 
galvanometer was immediately influenced by the thermo-electric 
current produced. The heat was steadily increased at sc y until 
at last the tin and platina combined there ; an effect which is 
known to take place with strong chemical action and high ig- 
nition ; but not the slightest additional effect occurred at the 
galvanometer. No other deflection than that due to the ther- 

* I do not mean to affirm that no traces of electricity ever appear in such 
cases. What I mean is, that no electricity is evolved in any way, due or 
related to the causes which excite voltaic electricity, or proportionate to them. 
That which does appear occasionally is the smallest possible fraction* of that 
which the acting matter could produce if arranged so as to act voltaicallv, 
probably not the one hundred thousandth, or even the millionth part, and is 
\ery probably altogether different in its source. 



April 1834.] Action of the electrolyte . 275 

mo-electric current was observable the whole time. Hence, 
though a conductor, and one capable of exerting chemical 
action on the tin, was uged, yet, not being an electrolyte , not 
the slightest effect of an electrical current could be observed 
(947.). 

923. From this it seems apparent that the peculiar character 
and condition of an electrolyte is essential in one part of the 
voltaic circuit ; and its nature being considered, good reasons 
appear wliy it and it alone should be effectual. An electro- 
lyte is always a compound body : it can conduct, but only 
whilst decomposing. Its conduction depends upon its decom- 
position and the transmission of its particles in directions paral- 
lel to the current ; and so intimate is this connexion, that if 
their transition be stopped, the current is stopped also ; if their 
course be changed, its course and direction changes with them; 
if they proceed in one direction, it has no power to proceed in 
any other than a direction invariably dependent on them. The 
particles of an electrolytic body are all so mutually connected, 
are in such relation with each other through their whole extent 
in the direction of the current, that if the last is not disposed 
of, the first is not at liberty to take up its place in the new 
combination which the powerful affinity of the most active metal 
tends to produce; and then the current itself is stopped; for 
the dependencies of the current, and the decomposition are so 
mutual, that whichsoever be originally determined, i. e. the 
motion of the particles or the motion of the current, the other 
is invariable in its concomitant production and its relation to it, 

921. Consider^ then, water as an electrolyte and also as an 
oxidizing body. The attraction of the zinc for the oxygen is 
greater, under the circumstances, than that of the oxygen for 
the hydrogen ; but in combining*with it, it tends to throw into 
circulation a current of electricity in a certain direction. This 
direction is consistent (as is found by innumerable experiments) 
with the transfer of the hydrogen from the zinc towards the 
platrna, and the transfer in the opposite direction of fresh oxy- 
gen from .the platina towards the zinc ; so that the current can 
pass in that one line, and, whilst it passes, can consist with 
and favour the renewal of the conditions upon the surface of 
the zinc,- which at first determined both the combination and 
circulation. Hence the continuance of the action there, and 

*2 



276 Electricity of the voltaic pile. [Series VIII. 

the continuation of the current. It therefore appears quite as 
essential that there should be an electrolyte in the circuit, in 
order that the action may be transferred forward, in a certain 
constant direction , as that there should be an oxidizing or other 
body capable of acting directly on the metal ; and it also ap- 
pears to be essential that these two should merge into one, or 
that the principle directly active on the mfetal by chemical action 
should be one of the ions of the electrolyte used. Whether the 
voltaic arrangement be excited by solution of acids, or alkalies, 
or sulphurets, or by fused substances (476.), this principal has 
always hitherto, as far as I am aware, been an anion (943.) ; 
and I anticipate, from a consideration of the principles of elec- 
tric action, that it must of necessity be one of that class of 
bodies. f 

925. If the action of the sulphuric acid used in the voltaic 
circuit be considered, it will be found incompetent to produce 
any sensible portion of the electricity of the current by its com- 
bination with the oxide formed, for this simple reason, it is de- 
ficient in a most essential condition : it forms no part of an 
electrolyte, nor is it in relation with any other body present in 
the solution which will permit of the mutual transfer of the 
particles and the consequent transfer of the electricity. It is 
true, that as the plane at which the acid is dissolving the oxide 
of zinc formed by the action o£the water, is in contact with the 
metal zinc, there seems no difficulty in considering how the 
oxide there could communicate an electrical state, proportionate 
to its own chemical action on the acid, to the metal, which is a 
conductor without decomposition. But on the side of the acid 
there is no substance to complete the circuit : the water, as 
water, casinot conduct it, or at least only so small a proportion 
that it is merely an incidental and almost inappreciable effect 
(970.) ; and it cannot conduct it as an electrolyte, because 
an electrolyte conducts in consequence of the mutnal relation 
and action of its particles j and neither of the elements of the 
water, nor even the water itself, as far as we can perceive, are 
ions with respect to the sulphuric acid (848.) 

926, This view of the secondary character of the sulphuric 

* It will be seen that I here agree with Sir Humphry Davy, who has ex- 
perimentally supported the opinion that acids and alkalies in combining do 
not produce any current of electricity. Philosophical Transactions, 1826, 
p. 398. 



April 1834.] Use of the exciting acid . 277 

acid as an agent in the production of the voltaic current, is 
further confirmed by the fact, that the current generated and 
transmitted is directly a^id exactly proportional to the quantity 
of water decomposed and the quantity of zinc oxidized (868. 
991.), and is the same as that required to decompose the same 
quantity of water. As, therefore, the decomposition of the 
water shows that the electricity has passed by its means, there 
remains qo other electricity to be accounted for or to be referred 
“to any action other than that of the zinc and the water on each 
other. 

927. The general Case (for it includes the former one* (921),) 
of acids and bases, may theoretically be stated in the following 
manner. Let a , fig. 79, be supposed to be a dry oxacid, and 
b a dry base, in contact ht e, and in electric communication at 
their extremities by plates of platina p p, and a platina wire w. 
If this acid and base were fluid, and combination took place at 
c } with an affinity ever so vigorous, and capable of originating 
an electric current, the current could not circulate in any im- 
portant degree; because, according to the experimental results, 
neither a nor b could conduct without being decomposed, for 
they are either electrolytes or else insulators, under all circum- 
stances, except to very feeble and unimportant currents (970. 
986.). Now the affinities at c are not such as tend to cause the 
elements either of a or b to separate, but only such as would 
make the two bodies combine together as a whole ; the point of 
action is, therefore, insulated, the action itself local (921. 917.), 
and no current can be formed. 

928. If the acid and base be dissolved in water, then it is 
possible that a small portion of the electricity due to chemical 
action may be conducted by the water without decomposition 
(966. 984.) ; but the quantity will be so small as to be utterly 
disproportionate to that due to the equivalents of chemical 
force; will be merely incidental ; and, as it docs not involve the 
essential principles of the voltaic pile, it forms no part of the 
phenomena at present under investigation * 

* It will I trust be fully understood, that in these investigations I am not 
professing to take an account of every small, incidental, or barely possible 
effect, dependent upon slight disturbances of the electric fluid during chemical 
action, but am seeking to distinguish and identify those actions on which the 
power of the voltaic battery essentially depends. 



278 


The pile excited by alkali . [Sebies VIII. 

929. If for the oxacid a hydracid be substituted (927.), — as 
one analagous to the muriatic, for instance, — then the state 
of things changes altogether, and a current due to the chemical 
action of the acid on the base is possible. But now both the 
bodies act as electrolytes, for it is only one principle of each 
which combine mutually, — as, for instance, the chlorine with 
the metal, — and the hydrogen of the acid* and the oxygen of the 
base are ready to traverse with the chlorine of the acyl and the 
metal of the base in conformity with the current and according 
to the general principles already so fully laid down. 

930. This view of the oxidation of the metal, or other direct 
chemical action upon it, being the sole cause of the production 
of the electric current in the ordinary Voltaic pile, is supported 
by the effects which take place when alkaline or sulphuretted 
solutions (931. 943.) are used for the electrolytic conductor 
instead of dilute sulphuric acid. It was in elucidation of this 
point that the experiments without metallic contact, and with 
solution of alkali as the exciting fluid, already referred to (884.), 
were made. 

931. Advantage was then taken of the more favourable con- 
dition offered, when metallic contact is allowed (895.), and the 
experiments upon the decomposition of bodies by a single pair 
of plates (899.) were repeated, •solution of caustic potassa being 
employed in the vessel v , fig. 77. in place of dilute sulphuric 
acid. All the effects occurred as before : the galvanometer was 
deflected ; the decompositions of the solutions of iodide of 
potassium, nitrate of silver, muriatic acid, and sulphate of soda 
ensued at x; and the places where the evolved principles ap- 
peared, as well^ as the deflection of the galvanometer, indicated 
a current in the same direction as when acid was in the vessel 
v \ i. e. from the zinc through the solution to the platina, and 
back by the galvanometer and substance sufferings decompo- 
sition to the zinc. 

932. The similarity in the action of either dilute sulphuric 
acid or potassa goes indeed far beyond this, even to the proof 
of identity in quantity as well as in direction of the electricity 
produced. If a plate of amalgamated zinc be put into a solu- 
tion of potassa, it is not sensibly acted upon *, but if touched 
in the solution by a plate of platina, hydrogen is evolved on the 



279 


Apjiil 1834.] Use of the exciting acid or alkali. 

surface of the latter metal, and the zinc is oxidized exactly as 
when immersed in dilute sulphuric acid (863.) . I accordingly 
repeated the experiment before described with weighed plates 
of zinc (864. &c.), using*however solution of potassa instead of 
dilute sulphuric acid. Although the time required was much 
longer than when acid was used, amounting to three hours for 
the oxidizement of 7*55 grains of zinc, still I found that the 
hydrogen evolved at the platina plate was the equivalent of the 
metal oxiSized at the surface of the zinc. Ilcncc the whole of 
the reasoning which was applicable in the former instance 
applies also here, the current being in the same directum, and 
its decomposing effect in the same degree, as if acid instead 
of alkali had been used (868.) . 

933. The proof, therefore, appears to me complete, that the 
combination of the acid with the oxide, in the former experi- 
ment, had nothing to do with the production of the electric 
current ; for the same current is here produced when the 
action of the acid is absent, and the reverse action of an 
alkali is present. I think it cannot be supposed for a moment, 
that the alkali acted chemically as an acid to the oxide formed ; 
on the contrary, our general chemh al knowledge leads to the 
conclusion, that the ordinary metallic oxides act rather as acids 
to the alkalies ; yet that kind of action would tend to give a re- 
verse current in the present easr;, if any were due to the union 
of the oxide of the exciting metal with the body which combines 
with it. But instead of any variation of this sort, the direction 
of the electricity was constant, and its quantity also directly 
proportional to the water decomposed, or the zinc oxidized. 
Thei’C are reasons for believing that acids and alkalies, when 
in contact with metals upon which they cannot act directly, still 
have a power of influencing' their attractions for oxygen (911.) ; 
but all the effects in these experiments prove, 1 think, that it 
is the oxidation of the metal necessarily dependent upon, and 
associated as it is with, the electrolyzation of the water (921. 
923.) tfrat produces the current; and that the acid or alkali 
merely act as solvents, and by removing the oxidized zinc, 
allow other portions to decompose fresh water, and so continue 
the evolution or determination of the current. 

934. The experiments were then varied by using solution of 
ammonia instead of solution of potassa ; and as it, when pure. 



280 Electricity of the voltaic pile. [Series VIlL 

is like water, a bad conductor (554.), it was occasionally im- 
proved in that power by adding sulphate of ammonia to it. 
But in all the cases the results were, the same as before ; de- 
compositions of the same kind were effected, and the electric 
current producing these was in the same direction as in the 
experiments just described. 

935. In order to put the equal and similar action of acid and 
alkali to stronger proof, arrangements were made as fig. 80. : 
the glass vessel A contained dilute sulphuric acid, the corre- 
sponding glass vessel B solution of potassa, P P was a plate of 
platina dipping into both solutions, and Z Z two plates of 
amalgamated zinc connected with a delicate galvanometer. 
When these were plunged at the same time into the two vessels, 
there was generally a first feeble effebt, and that in favour of 
the alkali, i. e . the electric current tended to pass through the 
vessels in the direction of the arrow, being the reverse di- 
rection of that which the acid in A would have produced alone ; 
but the effect instantly ceased, and the action of the plates in 
the vessels was so equal, that, being contrary because of the 
contrary position of the plates, no permanent current resulted. 

936. Occasionally a zinc*plate was substituted for the plate 
P P, and platina plates for the plates Z Z ; but this caused no 
difference in the results : nor did a further change of the mid- 
dle plate to copper produce any alteration. 

937. As the opposition of electric -motive pairs of plates pro- 
duces results other than those due to the mere difference of 
their independent actions (1011. 1045.), I devised another form 
of apparatus, in which the action of acid and alkali might be 
more directly compared. A cylindrical glass cup, about two 
inches deep within, an inch in internal diameter, and at least a 
quarter of an ffich in thickness, was cut down the middle into 
halves, fig. 81. A broad brass ring, larger in diam^fer than 
the cup, was supplied with a screw at one side ; so fllat when 
the two halves of the cup were within the ring, and the screw 
was made to press tightly against the glass, the cup held any 
fluid put into it. Bibulous paper of different degrees of per- 
meability was then cut into pieces of such a size a§ to be easily 
introduced between the loosened halves of the cup, and served 
when the latter were tightened again to form a porous division 
down the middle of the cup, sufficient to keep any two fluids 



281 


Ap&il 1834.] Exciting action of acid and alkali. 

on opposite sides of the paper from mingling, except very slowly, 
and yet allowing them to act freely as one electrolyte . The two 
spaces thus produced I w^ll call the cells A and B, fig. 82. This 
instrument I have found of most general application in the in- 
vestigation of the relation of fluids and metals amongst them- 
selves and to each other. By combining its use with that of 
the galvanometer, it is easy to ascertain the relation of one 
metal with two fluids, or of two metals with one fluid, or of two 
metals and two fluids upon each other. 

938. Dilute sulphuric acid, sp. gr. 125. was put into the cell 
A, and a strong solution of caustic potassa into the cell B ; 
they mingled slowly through the paper, and at last a thick crust 
of sulphate of potassa formed on the side of the paper next to 
the alkali. A plate of cleah platina was put into each cell and con- 
nected with a delicate galvanometer, but no electric current could 
be observed. Hence the contact of acid with one platina plate, 
and alkali with the other, was unable to produce a current ; 
nor was the combination of the acid with the alkali more 
effectual (925.). 

939. When one of the platina plates was removed and a zinc 
plate substituted, either amalgamated or not, a strong electric 
current was produced. But, whether the zinc were in the acid 
whilst the platina was in the alkali, or whether the reverse 
order were chosen, the electric current was always from the 
zinc through the electrolyte to the platina, and back through 
the galvanometer to the zinc, the current seeming to be strongest 
when the zinc was in the alkali and the platina in the acid. 

940. In these experiments, therefore, the acid seems to have 
no power over the alkali, but to be rather inferior to it in force. 
Hence there is no reason to suppose that the combination of 
the oxide formed with the acid around it has any direct -influ- 
ence in producing the electricity evolved, the whole of which 
appears to be due to the oxidation of the metal (919.). 

941. The alkali, in fact, is superior to the acid in bringing a 
metal into what is called the positive state ; for if plates of the 
same metal, as zinc, tin, lead, or copper, be used both in the 
acid or alkali, the electric current is from the alkali across the 
cell to the acid, and back through the galvanometer to the al- 
kali, as Sir Humphry Davy formerly stated*. This current is 

* Elements of Chemical Philosophy, p. 149 ; or Philosophical Transactions, 
1$26, p. 403. 



282 Exciting action of sulphuretted solutions . [Sebies VIII. 

so powerful, that if amalgamated zinc, or tin, or lead be used, 
the metal in the acid evolves hydrogen the moment it is placed 
in communication with that in the alkali, not from any direct 
action of the acid upon it, for if the contact be broken, the action 
ceases, but because it is powerfully negative with regard to the 
metal in the alkali. 

942. The superiority of alkali is further proved by this, that 
if zinc and tin be used, or tin and lead, whichsoever metal is 
put into the alkali becomes positive, that in the acid being 
negative. Whichsoever is in the alkali is oxidized, whilst that 
in the acid remains in the metallic state, as far as the electric 
current is concerned. 

943. When sulphuretted solutions are used (930.) in illus- 
tration of the assertion, that it is tlto chemical action of .the 
metal and one of the ions of the associated electrolyte that pro- 
duces all the electricity' of the voltaic circuit, the proofs are 
still the same. Thus, as Sir Humphry Davy* has shown, if 
iron and copper be plunged into dilute acid, the current is 
from the iron through the liquid to the copper ; in solution of 
potassa it is in the same direction, but in solution of sulphuret 
of potassa it is reversed. In the two first cases it is oxygen 
which combines with the iron, in the latter sulphur which com- 
bines with the copper, that produces the electric current ; but 
both of these arc ions , existing, as such in the electrolyte, which 
is at the same moment suffering decomposition ; and, what is 
more, both of these arc anions , for they leave the electrolytes 
at their anodes , and act just as chlorine, iodine, or any other 
anion would act which might have been previously chosen as 
that which should be used to throw the voltaic circle into ac- 
tivity. 

944. The following experiments complete the series of proofs 
of the origin of the electricity in the voltaic pile. A fluid 
amalgam of potassium, containing not more than a hundredth 
of that metal, was put into pure water, and connected through 
the galvanometer with a plate of platina in the same water. 
There was immediately an electric current from the amalgam 
through the electrolyte to the platina. This must have been 
due to the oxidation only of the metal, for there was neither 

* Elements of Chemical Philosophy, p. 148. 



April 1834.] Local and current chemical force, 283 

acid nor alkali to combine with, or in any way act on, the body 
produced. 

945. Again, a plate of clean lead and a plate of platina were 
put into pure water. There was immediately a powerful cur- 
rent produced from the lead through the fluid to the platina : 
it was even intense enough to decompose solution of the iodide 
of potassium when* introduced into the circuit in the form of 
apparatus already described (880.), fig. 73. Here no action of 
acid or alkali on the oxide formed from the lead could supply 
the electricity : it was due solely to the oxidation of the metal. 


946. There is no point in electrical science which seems to 
me of more importance than the state of the metals and the 
electrolytic conductor in a simple voltaic circuit before and at 
the moment when metallic contact is first completed. If (dearly 
understood, I feel no doubt it would supply us with a direct 
key to the laws under which the great variety of voltaic excite- 
ments, direct and incidental, occur, and open out new fields of 
research for our investigation*. 

947. Wc seem to have the power of deciding to a certain ex- 
tent in numerous cases of chemical affinity, (as of zinc with the 
oxygen of water, &c. &c.) which of two modes of action of the 
attractive power shall be exerted (990.). In the one mode wc 
can transfer the power onwards, and makes it produce elsewhere 
its equivalent of action (867. 917.) ; in the other it is not trans- 
ferred, but exerted wholly at the spot. The first is the ease 
of volt a- electric excitation, the other ordinary chemical affinity : 
but both are* chemical actions and due to one force or prin- 
ciple. 

948. The general circumstances of the former mode occur 
in all instances of voltaic currents, but may be considered as in 
their perfect condition, and then free from those of the second 
mode, in some only of the cases ; as in those of plates of zinc 
and platina in solution of potassa, or of amalgamated zinc and 
platina in dilute sulphuric acid. 

94$, 'Assuming it sufficiently proved, by the preceding ex- 
periments and considerations, that the electro -motive action de- 

* In connexion with this part of the subject refer now to Series XI. 1164, 
Series XII. 1343-^1358, and Series XIII. 1621 &c.— Dec. 1838. 



284 


Action of the elements of a pile. [SLeries YIII. 

pends, when zinc, platina, and dilute sulphuric acid are used, 
upon the mutual affinity of the metal zinc and the oxygen of 
the water (921. 924.), it would appear that the metal, when 
alone, ha§ not power enough, under the circumstances, to take 
the oxygen and expel the hydrogen from the water j for, in 
fact, no such action takes place. But it would also appear that 
it has power so far to act, by its attraction for .the oxygen of the 
particles in contact with it, as to place the similar forces already 
active between these and the other particles of oxygen and the 
particles of hydrogen in the water, in a peculiar state of tension 
or polarity, and probably also at the same time to throw those 
of its own particles which are in contact with the water into a 
similar but opposed state. Whilst this state is retained, no 
further change occtirs ; but when it fs relieved, by completion 
of the circuit, in which case the forces determined in opposite 
directions, with respect to the zinc and the electrolyte, are 
found exactly competent to neutralize each other, then a series 
of decompositions and recompositions takes place amongst the 
particles of oxygen and hydrogen constituting the water, be- 
tween the place of contact with the platina and the place where 
the zinc is active ; these intervening particles being evidently 
in close dependence upon and relation to each other. The 
zinc forms a direct compound with those particles of oxygen 
which were, previously, in divided relation to both it and the 
hydrogen : the oxide is removed by the acid, and a fresh sur- 
face of zinc is presented to the water, to renew and repeat the 
action. 

950. Practically, the state of tension is best relieved by dip- 
ping a metal which has less attraction for oxygen than the zinc, 
into the dilute acid, and making it also touch the zinc. The 
force of chemidal affinity, which has been influenced or polar- 
ized in the particles of the water by the dominant attraction of 
the zinc for the oxygen, is then transferred, in a most extraor- 
dinary manner, through the two metals, so as to re-enter upon 
the circuit in the electrolytic conductor, which, unlike the metals 
in that respect, cannot convey or transfer it without suffering 
decomposition ; or rather, probably, it is exactly balanced and 
neutralized by the force which at the same momenta completes 
the combination of the zinc with the oxygen of the water. The 
forces, in fact, of the two particles which are acting towards 



285 


April 1834.] Polarized light across the electrolyte. 

each other, and, which are therefore in opposite directions, are 
the origin of the two opposite forces, or directions of force, in 
the current. They are of necessity equivalent to each other. 
Being transferred forward in contrary directions, they produce 
what is called the voltaic current : and it seems to me impos- 
sible to resist the idea that it must be preceded by a state of ten- 
sion in the fluid, tyad between the fluid and the zinc ; the first 
consequence of the affinity of the zinc for the oxygen of the 
water. 

951. I have sought carefully for indications of a state of ten- 
sion in the electrolytic conductor ; and conceiving that it might 
produce something like structure, cither before or during its 
discharge, I endeavoured to make this evident by polarized 
light. A glass cell, seven inches long, one inch and a half 
wide, and six inches deep, had two sets of platina electrodes 
adapted to it, one set for the ends, and the other for the sides. 
Those for the sides were seven inches long by three inches 
high, and when in the cell were separated by a little frame of 
wood covered with calico ; so that when made active by con- 
nexion with a battery upon any solution in the cell, the bubbles 
of gas rising from them did not obscure the central parts of 
the liquid. 

952. A saturated solution of sulphate of soda was put into the 
cell, and the electrodes connected with a battery of 150 pairs 
of 4-inch plates : the current of electricity was conducted across 
the cell so freely, that the discharge was as good as if a wire 
had been used. A ray of polarised light was then transmitted 
through the solution, directly across the course of the electric 
current, and Examined by an analyzing plate ; but though it 
penetrated seven inches of solution thus subject to the action 
of the electricity, and though contact was sometimes made, 
sometimes broken, and occasionally reversed during the obser- 
vations, not the slightest trace of action on the ray could be per- 
ceived^. 

953.. The large electrodes were then removed, and others in- 
troduced which fitted the ends of the cell. In each a slit was 
cut, to allow the light to pass. The course of the polarized 
ray was now parallel to the current, or in the direction of its 
axis (517.) j but still no effect, under any circumstances of. con- 
tact or disunion/ could be perceived upon it. 



286 Polarized light across the electrolyte . . [Series YIII 

954. A strong solution of nitrate of lead was employed in- 
stead of the sulphate of soda, but no effects could be detected. 

955. Thinking it possible that the discharge of the electric 
forces by the successive decompositions and recompositions of 
the particles of the electrolyte might neutralize and therefore de- 
stroy any effect which the first state of tension could by possibility 
produce, I took a substance which, being an excellent electrolyte 
when fluid, was a perfect insulator when solid, namely, borate of 
lead, in the form of a glass plate, and connecting the sides and the 
edges of this mass with the metallic plates, sometimes in contact 
witli the poles of a voltaic battery, and sometimes even with 
the electric machine, for the advantage of the much higher in- 
tensity then obtained, I passed a polarized ray across it in 
various directions, as be tore, but could not obtain the slightest 
appearance of action upon the light. Hence I conclude, that 
notwithstanding the new and extraordinary state which must 
be assumed by an electrolyte, either during decomposition 
(when a most enormous quantity of electricity must be traversing 
it), or in the state of tension which is assumed as preceding de- 
composition, and which might be supposed to be retained in 
the solid form of the electrolyte, still it has no power of affect- 
ing a polarized ray of light ; for no kind of structure or tension 
can in this way be rendered evident. 

956. There is, however, one.beautiful experimental proof of 
a state of tension acquired by the metals and the electrolyte 
before the electric current is produced, and before contact of 
the different metals is made (915.) ; in fact, at that moment 
when chemical forces only are efficient as a cause of action. I 
took a voltaic apparatus, consisting of a single pair of large 
plates, namely, a cylinder of amalgamated zinc, and a double 
cylinder of copper. These were put into a jar containing dilute 
sulphuric acid*, and could at pleasure be placed in metallic 
communication by a copper wire adjusted so as to dip at tjie ex- 
tremities into two cups of mercury connected with the two 
plates. 

957. Being thus arranged, there was no chemical action 
whilst the plates were not connected. On making th? con- 

* When nitro-sulphuric acid is used, the spark is 'more powerful, but local 
chemical action can then commence, and proceed without requiring metallic 
contact. 



287 


April 1834.] Spark without metallic contact . 

nexion, a spark was obtained *, and thb solution was immediately 
decomposed. On breaking it, the usual spark was obtained, 
and the decomposition ceased. In this case it is evident that 
the first spark must have Occurred before metallic contact was 
made, for it passed through an interval of air ; and also that it 
must have tended to pass before the electrolytic action began ; 
for the latter could not take place until the current passed, and 
the current could not pass before the spark appeared. Hence 
I think the*re is sufficient proof, that as it is the zinc and water 
which by their mutual action produce the electricity of this 
apparatus, so these by their first contact with each oilier, were 
placed in a state of powerful tension (931.), which, though it 
could not produce the actual decomposition of the water, was 
able to make a spark of olcctricity pass between the zinc and a 
fit discharger as soon as the interval was rendered sufficiently 
small. The experiment demonstrates the direct production of 
the electric spark from pure chemical forces. 

958. There arc a few circumstances connected with the pro- 
duction of this spark by a single pair of plates, which should 
bo known, to ensure success to the experimentf. When the 
amalgamated surfaces of contact are cpiitc clean and dry, the 
spark, on making contact, is quite as brilliant as on breaking it, 
if not even more so. When a film of oxide or dirt was present 
at either mercurial surface, then the first spark was often feeble, 
and often failed, the breaking spark, however, continuing very 
constant and bright. When a little water was put over the 
mercury, the spark was greatly diminished in brilliancy, but 
very regular both on making and breaking contact. When the 
contact was thade between clean platina, the spark was also 
very small, but regular both ways. The true, electric, spark is, 
in fact, very small, and when surfaces of mercivry arc used, it 
is the combustion of the metal which produces the greater part 
of the light. The circumstances connected witli the burning 
of the mercury are most favourable on breaking contact ; for 

* It has been universally supposed that no spark is produced on making the 
contact between a single pair of plates. X was led to expect one from the con- 
siderations already advanced in this paper. The wire of communication should 
be short} for With a long wire, circumstances strongly affecting the spark are 
introduced, 

f Bee in relation to preciutious respecting a spark, 1074.— Dec, 1838. 



288 


Local chemical action . 


[Series VIII. 


the act of separation exposes clean surfaces of metal, whereas, 
on making contact a thin film of oxide, or soiling matter, often 
interferes. Hence the origin of the general opinion that it is 
only when the contact is .broken thatf the spark passes. 


959. With reference to the other set of cases, namely, those 
of local action (947.) in which chemical aifiwity being exerted 
causes no transference of the power to a distance where no 
electric current is produced, it is evident that forces of the 
most intense kind must be active, and in some way balanced in 
their activity, during such combinations ; these forces being 
directed so immediately and exclusively towards each other, 
that no signs of the powerful electric current they can produce 
become apparent, although the same r iinal state of things is ob- 
tained as if that current had passed. It was Berzelius, I believe, 
who considered the heat and light evolved in cases of combus- 
tion as the consequences of this mode of 'exertion of the elec- 
tric powers of the combining particles. But it will require a 
much more exact and extensive knowledge of the nature of 
electricity, and the manner in which it is associated with the 
atoms of matter, before we can understand accurately the action 
of this power in thus causing their union, or comprehend the 
nature of the great difference which it presents in the two 
modes of action just distinguished. We may imagine, but such 
imaginations must for the time be classed with the great mass 
of doubtful knowledge (876.) which we ought rather to strive to 
diminish than to increase ; for the very extensive contradictions 
of this knowledge by itself shows that but a small portion of it 
can ultimately prove true*. 

960. @f the two modes of action in which chemical affinity is 
exerted, it is important to remark, that that which produces 
the electric current is as definite as that which causes ordinary 
chemical combination ; so that in examining the production or 
evolution of electricity in cases of combination or decomposition, 
it will be necessary, not merely to observe certain defects de- 
pendent upon a current of electricity, but also their quantity ; 
and though it may often happen that the forces concerned in 
any particular case of chemical action may be partly exerted in 

* Refer to 1738, etc. Series XIV. — Dec, 1838. . 



Apftiii 1834.] Electro-chemical forces of matter. 289 

one mode and partly in the other, it is only those which are 
efficient in producing the current that have any relation to vol- 
taic action. Thus, in the combination of oxygen and hydrogen 
to produce water, electrfc powers to. a most enormous amount 
are for the time active (861. 873.) ; but any mode of examining 
the flame which they form during energetic combination, which 
has as yet been^ devised, has given but the feeblest traces. 
These therefore** may not, cannot, be taken as evidences of the 
nature of* the action ; but arc merely incidental results, incom- 
parably small in relation to the forces ‘concerned, and supplying 
no information of the way in which the particles are active on 
each other, or in which their forces arc fimilly arranged. 

961. That such eases of chemical action produce no current 
of electricity , is perfectly consistent with what wc know of the 
voltaic apparatus, in which it is essential that one of the com- 
bining elements shall form part of, or be in direct relation with, 
an electrolytic conductor (921. 923.). That such (‘uses produce 
no free electricity of tension, and that when they arc converted 
into cases of voltaic action they produce a current in which the 
opposite forces are so equal as to neutralize each other, prove the 
equality of the forces in the opposed acting particles of matter, 
and therefore the equality of electric power in those quantities 
of matter which are called electro-chemical equivalents (824.) . 
Hence another proof of the definite nature of electro-chemical 
action (783. &c.), and that chemical affinity and electricity are 
forms of the same power (917. &c.). 

962. The direct reference of the effects produced by the 
voltaic pile at the place of experimental decomposition to the 
chemical affinities active at the place of excitation (891. 917.), 
gives a very simple and natural view of the cause why flic bodies 
{or ions) evolved pass in certain directions; for it is only when 
they pass in those directions that their forces can consist with 
and compensate (in direction at least) the superior forces which 
are dominant at the place where the action of the whole is de- 
termined. If, for instance, in a yoltaic circuit, the activity of 
which is determined by the attraction of zinc for the oxygen of 
water* the zinc move from right to left, then any other cation 
included in the circuit, being part of an electrolyte, or forming 
part of it at the moment, will also move from right to left ; and 
as the oaygen of the water, by its natural affinity for the zinc,' 

v 



290 


Mutual relation of ions in the circuit . [Series VIII. 

moves from left to right, so any other body of the same class 
with it (i. e. any other anion), under its government for the time, 
will move from left to right. 

963. This I may illustrate by reference to fig. 83, the double 
circle of which may represent a complete voltaic circuit, the 
direction of its forces being determined by supposing for a 
moment the zinc b and the platina c as* representing plates of 
those metals acting upon water, d , e , and other^ substances, but 
having their energy exalted so as to effect several decomposi- 
tions by the use of a battery at &*(989.). This supposition 
may be allowed, because the action in the battery will only con- 
sist of repetitions of what would take place between b and c, if 
they really constituted but a single pair. The zinc b , and the 
oxygen d , by their mutual affinity, tend to unite ; but as the 
oxygen is already in association with the hydrogen e , and has 
its inherent chemical or electric powers neutralized for the time 
by those of the latter, the hydrogen e must leave the oxygen d , 
and advance in the direction of the arrow head, or else the 
zinc b cannot move in the same direction to unite to the oxygen 
d , nor the oxygen d move in the contrary direction to unite to 
the zinc b, the relation of the similar forces of b and e, in con- 
trary directions, to the opposite. forces of d being the preventive. 
As the hydrogen e advances, it, on coming against the platina 

c, f, which forms a part of the circuit, communicates its electric 
or chemical forces through it to the next electrolyte in the cir- 
cuit, fused chloride of lead, g , h , where the chlorine must move 
in conformity with the direction of the oxygen at d, for it has 
to compensate the forces disturbed in its part of the circuit by 
the superior influence of those between the oxygen and zinc at 

d, b, aided as they are by those of the battery a ; and for a si- 
milar reason the lead must move in the direction pointed out 
by the arrow head, that it may be in right relation to the first 
moving body of its own class, namely^ the zinc b. If copper 
intervene in the circuit from i to k, it acts as the platina did 
before ; and if another electrolyte, as the iodide of tin, occur 
at l f wi, then the iodine l } being an anion , must move in con- 
formity with the exciting anion , namely, the oxygen d, and the 
cation tin m move in correspondence with the other cations, b, e, 
and A, that the chemical forces may be in equilibrium as, to 
their direction and quantity throughout the circuit. 'Should it* 



291 


April 1834.] Transfer of anions and cations . 

so happen that the anions in their circulation can combine with 
the metals at the anodes of the respective electrolytes, as 
would be the case at the jplatina f and the copper k } then those 
bodies becoming parts of electrolytes, under the influence of 
the current, immediately travel ; but considering their relation 
to the zinc b , it is evidently impossible that they can travel in 
any other direc^ioii than what will accord with its course, and 
therefore ^an never tend to pass otherwise than from the anode 
and to the cathode, 

964. In such a circle as that delineated, therefore, all the 
known anions may be grouped within, and all the cations with- 
out. If any number of them enter as ions into the constitution 
of electrolytes , and, forming one circuit, are simultaneously 
subject to one common ‘current, the anions must move in ac- 
cordance with each other in one direction, and the cations in 
the other. Nay, more than that, equivalent portions of these 
bodies must so advance in opposite directions : for the advance 
of every 32*5 parts of the zinc b must be accompanied by a 
motion in the opposite direction of 8 parts of oxygen at d , of 
36 parts of chlorine at g, of 126 parts of iodine at / ; and in the 
same direction by electro-chemical equivalents of hydrogen, 
lead, copper and tin, at e , h, k , and m. 


965. If the present paper be accepted as a correct expres- 
sion of facts, it will still only prove a confirmation of certain 
general views put forth by Sir Humphry Davy in his Bakcrian 
Lecture for 1806*, and revised and re-stated by him in another 
Bakerian Lecture, on electrical and chemical changes, for the 
year 1826f . His general statement is, that 4t chemical and 
electrical attractions were produced by the same cause , acting 
in one case on particles , in the other on masses , of matter ; and 
that the same property , under different modifications , was the 
cause of all the phenomena exhibited by different voltaic com- 
binatums%ff This statement I believe to be true; but in ad- 
mitting and supporting it, I must guard myself from being 
supposed to assent to all that is associated with it in the two 
papers referred to, or as admitting the experiments which are 

# 5phiIosopliical Transactions, 1807 , t Ibid, 1826 , p. 383 . 

X Ibid. 4826, p. 889. 



292 


Electrolytic intensity [Skuies VIII. 

there quoted as decided proofs of the truth of the principle. 
Had I thought them so, there would have been no occasion for 
this investigation. It may be suppojed by some that I ought 
to go through these papers, distinguishing what I admit from 
what I reject, and giving good experimental or philosophical 
reasons for the judgment in both cases. But then I should 
be equally bound to review, for the same pHrj^ose, all that has 
been written both for and against the necessity of metallic con- 
tact, — for and against the origin of voltaic electricity in chemical 
action, — a duty which I may not undertake in the present paper*. 

If ii. On the Intensity necessary for Electrolyzation. 

966. It became requisite, for the comprehension of many of 
the conditions attending voltaic action, to determine positively, 
if possible, whether electrolytes could resist the action of 
an electric current when beneath a certain intensity ? whether 
the intensity at which the current ceased to act would be the 
same for all bodies ? and also whether the electrolytes thus re- 
sisting decomposition would conduct the electric current as a 
metal does, after they ceased to conduct as electrolytes, or 
would act as perfect insulators ? 

907. It was evident from the experiments described (904. 
906.) that different bodies were decomposed with very differ- 
ent facilities, and apparently that they required for their decom- 
position currents of different intensities, resisting some, but 
giving way to others. But it was needful, by very careful and 
express experiments, to determine whether a current could 
really pass through, and yet not decompose an electrolyte 
(910.). 

968. An arrangement (fig. 84.) was made, in which two glass 
vessels contained the same dilute sulphuric acid, sp. gr. 1*25. 
The plate z was amalgamated zinc, in connexion, by a platina 
wire a, with the platina plate e ; b was a platina wire connecting 

# I at one time intended to introduce here, in the form of a note, a table of 
reference to the papers of the different philosophers who have referred the 
origin of the electricity in the voltaic pile to contact, or to chemical action, 
or to both ; but on the publication of the first volume of M. Becquerel’a highly 
important and valuable Traits de 1’ElectricitS et du Magnetism, I thought it 
far better to refer to that work for these references, and the views held by the 
authors quoted. See pages 86, 91, 104, HO, 112, 117, 118, 120, 151, 152,224, 
227, 228, 232, 233, 252, 255, 267, 268, 290, &c.—July 3rd, 1834, 



April 1831.] determined for water . 293 

the two platina plates P ; c was a platina wire connected with 
the platina plate On the plate e was placed a piece of paper 
moistened in solution of iodide of potassium : the wire c was 
so curbed that its end could be made to rest at pleasure on this 
paper, and show, by the evolution of iodine there, whether a 
current was passing ; or, being placed in the dotted position, 
it* formed a direct “communication with the platina plate e, and 
the electricity could pass without causing decomposition. The 
object was to produce a current by the action of the acid on 
the amalgamated zinc in the first vessel A ; to pass it through 
the acid in the second vessel B by platina electrodes, that its 
power of decomposing water might, if existing, be observed ; 
and to verify the existence of the current at pleasure, by decom- 
position at e, without involving the continual obstruction to the 
current which would arise from making the decomposition there 
constant. The experiment, being arranged, was examined and 
the existence of a current ascertained by the decomposition at e ; 
the whole was then left with the end of the wire c resting on the 
plate e, so as to form a constant metallic communication there. 

969. After several hours, the end of the wire c was replaced 
on the test paper at e : decomposition occurred, and the proof 
of a passing current was therefore complete. The current was 
very feeble compared to what it had been at the beginning of the 
experiment, because of a peculiar state acquired by the metal 
surfaces in the second vessel, which caused them to oppose the 
passing current by a force which they possess under these cir- 
cumstances (1040.) , Still it was proved, by the decomposition, 
that this state of the plates in the second vessel was not able 
entirely to stop the current determined in the first, and that w as 
all that was needful to be ascertained in the present inquiry. 

970. This apparatus was examined from time to time, and 
an electric current always found circulating through it, until 
twelve days had elapsed, during which the water in the second 
vessel, had been constantly subject to its action. Notwith- 
standing this lengthened period, not the slightest appearance 
of a bubble upon either of the plates in that vessel occurred. 
From the results of the experiment, I conclude that a current 
had passed, but of so low an intensity as to fall beneath that 
degree'afc which the elements of water, unaided by any second- 
ary force resulting from the capability of combination with the 



294 Electrolytic intensity :—for water ; [Series VIII. 

matter of the electrodes, or of the liquid surrounding them, 
separated from each other. 

971. It may be supposed, that the ojygen and hydrogen had 
been evolved in such small quantities as to have entirely dis- 
solved in the water, and finally to have escaped at the surface, 
or to have reunited into water. That the hydrogen can be so 
dissolved was shown in the first vessel; fo^ after several days 
minute bubbles of gas gradually appeared upon a glass rod, 
inserted to retain the zinc and platina apart, and also upon the 
platina plate itself, and these were hydrogen. They resulted 
principally in this way : — notwithstanding the amalgamation of 
the zinc, the acid exerted a little direct action upon it, so that 
a small stream of hydrogen bubbles was continually rising from 
its surface ; a little of this hydrogen gradually dissolved in the 
dilute acid, and was in part set free against the surfaces of the 
rod and the plate, according to the well-known action of such 
solid bodies in solutions of gases (623. &c.). 

972. But if the gases had been evolved in the second vessel 
by the decomposition of water, and had tended to dissolve, 
still there would have been every reason to expect that a few 
bubbles should have appeared on the electrodes, especially on 
the negative one, if it were only because of its action as a 
nucleus on the solution supposed to be formed; but none 
appeared even after twelve day*. 

973. When a few drops only of nitric acid were added to 
the vessel A, fig. 84., then the results were altogether differ- 
ent. In less than five minutes bubbles of gas appeared on the 
plates P' and P" in the second vessel. To prove that this was 
the effect of the electric current (which by trial at e was found 
at the same timp to be passing,) the connexion at e was broken, 
the plates F P" cleared from bubbles and left in the acid of 
the vessel B, for fifteen minutes : during that time no bubbles 
appeared upon them ; but on restoring the communication at 
e, a minute did not elapse before gas appeared in bubbles upon 
the plates. The proof, therefore, is most full and complete, 
that the current excited by dilute sulphuric acid with a little 
nitric acid in vessel A, has intensity enough to overcome the 
chemical affinity exerted between the oxygen and hydrogen 
of the water in the vessel B, whilst that excited by dilute sul- 
phuric acid alone has not sufficient intensity, * 



April 1834.] for sulphate of soda . 295 

974. On using a strong solution of caustic potassa in the 
vessel A, to excite the current, it was found by the decom- 
posing effects at e, tha^ the current passed. But it had not 
intensity enough to decompose the water in the vessel B ; for 
though left for fourteen days, during the whole of which time 
the current was found to be passing, still not the slightest ap- 
pearance of g§$ appeared on the plates V' P", nor any other 
signs of t^e water having suffered decomposition. 

975. ^Sulphate of soda in solution was then experimented 
with, for the purpose of ascertaining with respect to it, whether 
a certain electrolytic intensity w r as also required for its decom- 
position in this state, in analogy with the result established 
with regard to water (974.). The apparatus was arranged as 
in fig. 85 ; P and Z are The platina and zinc plates dipping in- 
to a solution of common salt ; a and h arc platina plates con- 
nected by wires of platina (except in the galvanometer y) with 
P and Z ; c is a connecting wire of platina, the ends of which 
can be made to rest either on the plates a y h y or on the papers 
moistened in solutions which are placed upon them ; so that 
the passage of the current without decomposition, or with one 
or two decompositions, was under ready command, as far as 
arrangement was concerned. In order to change the anodes 
and cathodes at the places of decomposition, the form of appa- 
ratus, fig. 86, was occasionally adopted. Here only one platina 
plate, c, was used ; both pieees of paper on which decompo- 
sition was to be effected were placed upon it, the wires from P 
and Z resting npon these pieces of paper, or upon the plate c y 
according as the current with or without decomposition of the 
solutions was required. 

976. On placing solution of iodide of potassium in paper at 
one of the decomposing localities, and solution of sulphate of 
soda at the other, so that the electric current should pass 
through both at once, the solution of iodide *w as slowly decom- 
posed, yielding iodine at the anode and alkali at the cathode ; 
but the solution, of sulphate of soda exhibited no signs of de- 
composition, neither acid nor alkali being evolved from it. On 
placing the wires so4hat the iodide alone was subject to the 
action of the current (900.), it was quickly and powerfully de- 
composed ; but on arranging them so that the sulphate of soda 
alone was subject to action, it still refused to yield up its ele- 
ments* Finally, the apparatus was so arranged under a wet 



296 Electrolytic intensity : — chloride of lead ; [Series VIII. 

bell-glass, that it could be left for twelve hours, the current 
passing during the whole time through a solution of sulphate of 
soda, retained in its place by only tw? thicknesses of bibulous 
litmus and turmeric paper. At the end of that time it was as- 
certained by the decomposition of iodide of potassium at the 
second place of action, that the current, j^as passing and had 
passed for the twelve hours, and yet no trace of acid or alkali 
from the sulphate of soda appeared. 

9 77. From these experiments it may, I think, be concluded, 
that a solution of sulphate of soda can conduct a current of 
electricity, which is unable to decompose the neutral salt pre- 
sent ; that this salt in the state of solution, like water, requires 
a certain electrolytic intensity for its decomposition ; and that 
the necessary intensity is much higher for this substance than 
for the iodide of potassium in a similar state of solution. 

978. 1 then experimented on bodies rendered decomposable 
by fusion, and first on chloride of lead . The current was ex- 
cited by dilute sulphuric acid without any nitric acid between 
zinc and platina plates, fig. 87., and was then made to traverse 
a little chloride of lead fused upon glass at a , a paper moistened 
in solution of iodide of potassium at b y and a galvanometer at g , 
The metallic terminations at a and b were of platina. Being 
thus arranged, the decomposition at b and the deflection at g 
showed that an electric current was passing, but there was no 
appearance of decomposition at a y not even after a metallic 
communication at b was established. The experiment was re- 
peated several times, and I am led to conclude that in this ease 
the current has not intensity sufficient to cause the decompo- 
sition of the chloride of lead ; and further, that, like water 
(974.), fused chloride of lead can conduct an electric current 
having an intensity below that required to effect decompo- 
sition. 

979. Chloride of silver was then placed at a , fig. 87., instead 
of chloride of lead. There was a very ready decomposition of 
the solution of iodide of potassium at b y and when metallic con- 
tact was made there, very considerable deflection of the galva- 
nometer needle at g . Platina also appeared to be dissolved at 
the anode of the fused chloride at a, and there was every ap- 
pearance of a decomposition having been effected there. 

980. A further proof of decomposition was obtained i# the 
following manner. The platina wires in the fused chloride at 



297 


April 1834.] chloride of silver ; nitre . 

a were brought very near together (metallic contact having been 
established at b), and left so ; the deflection at the galvanome- 
ter indicated the passage of a current, feeble in its force, but 
constant. After a minute or two, however, the needle would 
suddenly be violently affected, and indicate a current as strong 
as if metallic contact had taken place at a . This I actually 
found to be thc^cas^'fbr the silver reduced by the action of the 
current crystallized in long delicate spieuhe, and these at last 
completed the metallic communication ; and at the same time 
that they transmitted a more powerful current than the fused 
chloride, they proved that electro- chemical decomposition of that 
chloride had been going on. lienee it appears, that the cur- 
rent excited by dilute sulphuric acid between zinc and platina, 
has an intensity above that required to electrolyze the fused 
chloride of silver when placed between platina electrodes, al- 
though it has not intensity enough to decompose chloride of 
lead under the same circumstances. 

981. A drop of water placed at a instead of the fused chlo- 
rides, showed as in the former case (970.), that it could conduct 
a current unable to decompose it, for decomposition of the so- 
lution of iodide at b occurred after some time. But its con- 
ducting power was much below that ol the fused chloride of 
lead (978.). 

982. Fused nitre at a conductpd much better than water: 1 
was unable to decide with certainty whether it w as electrolyzed, 
but I incline to think not, for there was no discoloration against 
the platina at the cathode , If sulpho-nitric acid had been used 
in the exciting vessel, both the nitre and the chloride of lead 
would have suffered decomposition like the water (900.) . 

983. The results thus obtained of conduction without decom- 
position, and the necessity of a certain electrolytic intensity for 
the separation of the ions ol different electrolytes, are imme- 
diately connected with the experiments and results given in 
§ 10. of the Fourth Series of these Researches (418. 423. 444. 
449,) . But it will require a more exact knowledge of the nature 
of intensity, both as regards the first origin of the electric cur- 
rent, and also the manner in which it may be reduced, or low- 
ered by the intervention of longer or shorter portions of bad 
conductors, whether decomposable or not, before their relation 
can be minutely and fully understood. 

984. In the case of water, the experiments I have as yet 



298 Direct conduction by water . [Series VIII. 

made, appear to show, that, when the electric current is re- 
duced in intensity below the point required for decomposition, 
then the degree of conduction is the same whether sulphuric 
acid, or any other of the many bodies which can affect its trans- 
ferring power as an electrolyte, are present or not. Or, in other 
words, that the necessary electrolytic intensity for water is the 
same whether it be pure, or rendered a better conductor by the 
addition of these substances ; and that for currents of less in- 
tensity than this, the water, whether pure or acidulated, has 
equal conducting power. An apparatus, fig. 84, was arranged 
with dilute sulphuric acid in the vessel A, and pure distilled 
water in the vessel B. By the decomposition at e, it appeared 
as if water was a better conductor than dilute sulphuric acid 
for a current of such low intensity as t6 cause no decomposition . 
I am inclined, however, to attribute this apparent superiority of 
water to variations in that peculiar condition of the platina elec- 
trodes which is referred to further on in this Series (1040.), 
and which is assumed, as far as I can judge, to a greater degree 
in dilute sulphuric acid than in pure water. The power there- 
fore, of acids, alkalies, salts, and other bodies in solution, to 
increase conducting power, appears to hold good only in those 
cases where the electrolyte subject to the current suffers de- 
composition, and loses all influence when the current transmitted 
has too low an intensity to affect chemical change. It is proba- 
ble that the ordinary conducting power of an electrolyte in the 
solid state (419.) is the same as that which it possesses in the 
fluid state for currents the tension of which is beneath the due 
electrolytic intensity. 

985. Currents of electricity, produced by less than eight or 
ten series /> f voltaic elements, can be reduced to that intensity 
at which water can conduct them without suffering decompo- 
sition, by causing them to pass through three or four vessels in 
which water shall be successively interposed between platina 
surfaces. The principles of interference upon which this effect 
depends, will be described hereafter (1009. 1018.), but the ef- 
fect may be useful in obtaining currents of standard intensity, 
and is probably applicable to batteries of any number of pairs 
of plates. 

986. As there appears every reason to expect th%t all 
electrolytes will be found subject to the law which requires an 
electric current of a certain intensity for their decomposition. 



April 1834.] Necessary electrolytic intensity. 299 

but that they will differ from each other in the degree of inten- 
sity required, it will be desirable hereafter to arrange them in 
a table, in the order of their electrolytic intensities. Investi- 
gations on this point imfst, however, be very much extended, 
and include many more bodies than have been here mentioned 
before such a table can be constructed. It will be especially 
needful in such experiments, to describe the nature of the elec- 
trodes used, or, if possible, to select such as, like platina or 
plumbago m certain cases, shall have no power of assisting the 
separation of the ions to be evolved (913.). 

987. Of the two modes in which bodies can transmit* the 
electric forces, namely, that which is so characteristically ex- 
hibited by the metals, and usually called conduction, and that in 
which it is accompanied* by decomposition, the first appears 
common to all bodies, although it occurs with almost infinite 
degrees of difference ; the second is at present distinctive of 
the electrolytes. It is, however, just possible that it may here- 
after be extended to the metals ; for their power of conducting 
without decomposition may, perhaps justly, be ascribed to their 
requiring a very high electrolytic intensity for their decompo- 
sition. 

987^. The establishment of the principle that a certain elec- 
trolytic intensity is necessary before decomposition can be ef- 
fected, is of great importance to all those considerations which 
arise regarding the probable effects of weak currents, such for in- 
stance as those produced by natural thermo-electricity, or natural 
voltaic arrangements in the earth. For to produce an effect of 
decomposition or of combination, a current must not only exist, 
but have a certain intensity before it can overcome the quiescent 
affinities opposed to it, otherwise it will be conducted, producing 
no permanent chemical effects. On the other hand, the prin- 
ciples are also now evident by which an opposing action can be 
so weakened by the juxtaposition of bodies not having quite 
affinity enough to cause direct action between them (913.), that 
a very weak current shall be able to raise the sum of actions 
sufficiently high, and cause chemical changes to occur. 

988. In concluding this division on the intensity necessary 
for electrolyzation , I cannot resist pointing out the following 
remarkable conclusion in relation to intensity generally. It 
would appear that when a voltaic current is produced, having 



300 Theory of the voltaic battery. [Series VIII. 

a certain intensity, dependent upon the strength of the 
chemical affinities by which that current is excited (916.), it 
can decompose a particular electrolyte without relation to the 
quantity of electricity passed, the intensity deciding whether 
the electrolyte shall give way or not. If that .conclusion be con- 
firmed, then we may arrange circumstances so that the same 
quantity of electricity may pass in the same time , in at the same 
surface , into the same decomposing body in the sanity state } and 
yet, differing in intensity, will decompose in one case and in the 
other not \ — for taking a source of too low an intensity to decom- 
pose, and ascertaining the quantity passed in a given time, it is 
easy to take another source having a sufficient intensity, and re- 
ducing the quantity of electricity from it by the intervention 
of bad conductors to the same prop6rtion as the former cur- 
rent, and then all the conditions will be fulfilled which are re- 
quired to produce the result described. 

% in. On associated Voltaic circles , or the Voltaic battery. 

989. Passing from the consideration of single circles (875. 
&c.) to their association in the voltaic battery, it is a very evi- 
dent consequence, that if matters arc so arranged that two sets 
of affinities, in place of being opposed to each other as in figg. 
73. 76. (880. 891.), are made to act in conformity, then, instead 
of either interfering with the gther, it will rather assist it. This 
is simply the case of two voltaic pairs of metals arranged so as 
to form one circuit. In such arrangements the activity of the 
whole is known to be increased, and when ten, or a hundred, 
or any larger number of such alterations are placed in con- 
formable association with each other, the power of the whole 
becomes proportionably exalted, and we obtain that magnificent 
instrument of philosophic research, the voltaic battery. 

990. But it is evident from the principles of definite action 
already laid down, that the quantity of electricity in the cur- 
rent cannot be increased with the increase of the quantity of 
metal oxidized and dissolved at each new place of chemical 
action. A single pair of zinc and platina plates throws as 
much electricity into the form of a current, by the oxidation 
of 32' 5 grains of the zinc (868.) as would be circulated by the 
same alteration of a thousand times that quantity, or nearly 
five pounds of metal oxidized at the surface of the zinc plates* 



301 


April 1834.] Current of a voltaic battery. 

of a thousand pairs placed in regular battery order. For it is 
evident, that the electricity which passes across the acid from 
the zinc to the platina in the first cell, and which has been 
associated with, or even* evolved by, the decomposition of a 
definite portion of water in that cell, cannot pass from the zinc 
to the platina across the acid in the second cell, without the 
decomposition of^the Same quantity of water there, and the 
oxidation of the same quantity of zinc by it (921. 919.). The 
same result recurs in every other cell ; the electro-chemical 
equivalent of water must be decomposed in each, before the 
current can pass through it ; for the quantity of electricity 
passed and the quantity of electrolyte decomposed, must be 
the equivalents of each other. The action in each cell, there- 
fore, .is not to increase the quantity set in motion in any one 
cell, but to aid in urging forward that quantity, the passing of 
which is consistent with the oxidation of its own zinc; and in 
this way it exalts that peculiar property of the current which 
we endeavour to express by the term intensity, without increa- 
sing the quantity beyond that which is proportionate to the 
quantity of zinc oxidized in any single cell of the series. 

991. To prove this, I arranged ten pairs of amalgamated 
zinc and platina plates with dilute sulphuric acid in the form 
of a battery. On completing the circuit, all the pairs acted 
and evolved gas at the surfaces of the platina. This was col- 
lected and found to be alike in quantity for each plate ; and 
the quantity of hydrogen evolved at any one platina plate was 
in the same proportion to the quantity of metal dissolved from 
any one zinc plate, as was given in the" experiment with a single 
pair (864. &c.). It was therefore certain, that, just as much 
electricity and no more had passed through the series of ten 
pair of plates as had passed through, or would have been put 
into motion by, any single pair, notwithstanding that ten times 
the quantity of zinc had been consumed. 

992. This truth has been proved also long ago in another 
way, by the action of the evolved current on a magnetic needle ; 
the deflecting power of one pair of plates in a battery being 
equal to the deflecting power of the whole, provided the wires 
used be sufficiently large to carry the current of the single pair 
freely ; but the cause of this equality of action could not be 



302 Current of a voltaic battery ; [Series VIII. 

understood whilst the definite action and evolution of elec- 
tricity (783. 869.) remained unknown. 

993. The superior decomposing power of a battery over a 
single pair of plates is rendered evident in two ways. Elec- 
trolytes held together by an affinity so strong as to resist the 
action of the current from a single pair, yield up their elements 
to the current excited by many pairs ; and that body which is 
decomposed by the action of one or of few pairs of metals, &c., 
is resolved into its ions the more readily as it is acted upon by 
electricity urged forward by many alternations. 

994. Both these effects are, I think, easily understood. 
Whatever intensity may be, (and that must of course depend 
upon the nature of electricity, whether it consist of a fluid or 
fluids, or of vibrations of an ether, or any other kind or con- 
dition of matter,) there seems to be no difficulty in compre- 
hending that the degree of intensity at which a current of 
electricity is evolved by a first voltaic element, shall be in- 
creased when that current is subjected to the action of a second 
voltaic element, acting in conformity and possessing equal 
powers with the first : and as the decompositions are merely 
opposed actions, but exactly of the same kind as those which 
generate the current (917.), it seems to be a natural conse- 
quence, that the affinity which can resist the force of a single 
decomposing action may be unable to oppose the energies of 
many decomposing actions, operating conjointly, as in the vol- 
taic battery. 

995. That a body which can give way to a current of feeble 
intensity, should give way more freely to one of stronger force, 
and yet involve no contradiction to the law of definite electro- 
lytic action, is perfectly consistent. All the facts and also the 
theory I have ventured to put forth, tend to show that the act 
of decomposition opposes a certain force to the passage of the 
electric current ; and, that this obstruction should be overcome 
more or less readily, in proportion to the greater or less inten- 
sity of the decomposing current, is in perfect consistency with 
all our notions of the electric agent. 

996. I have elsewhere (947.) distinguished the chemical 
action of zinc and dilute sulphuric acid into two portions ; that 
which, acting effectually on the zinc, evolves hydrogen at once 



303 


April 1834.] its intensity and quantity. 

upon its surface, and that which, producing an arrangement of 
the chemical forces throughout the electrolyte present, (in this 
case water,) tends to take oxygen from it, but cannot do so 
unless the electric current consequent thereon can have free 
passage, and the hydrogen be delivered elsewhere than against 
the zinc. The electric current depends altogether upon the 
seepnd of these ; but when the current can pass, by favouring 
the electrolytic action it tends to diminish the former and in- 
crease the latter portion. 

997. It is evident, therefore, that when ordinary zinc is used 
in a voltaic arrangement, there is an enormous waste of that 
power which it is the object to throw into the form of an elec- 
tric current ; a consequence which is put in its strongest point 
of view when it is considered that three ounces and a half 
of zinc, " properly oxydized, can circulate enough electricity 
to decompose nearly one ounce of water, and cause the 
evolution of about 2400 cubic inches of hydrogen gas. This 
loss of power not only takes place during the time the elec- 
trodes of the battery are in communication, being then pro- 
portionate to the quantity of hydrogen evolved against the 
surface of any one of the zinc plates, but includes also alt the 
chemical action which goes on when the extremities of the pile 
are not in communication. 

998. This loss is far greater with ordinary zinc than with the 
pure metal, as M. Dc la Rive has shown*. The cause is, 
that when ordinary zinc is acted upon by dilute sulphuric acid, 
portions of copper, lead, cadmium, or other metals which it 
may contain, are set free upon its surface ; and these, being in 
contact with the zinc, form .small but very active voltaic circles, 
which cause great destruction of the zinc and evolution of hy- 
drogen, apparently upon the zinc surface, but really upon the 
surface of these incidental metals. In the same proportion as 
they serve to discharge or convey the electricity back to the 
zinc, do they diminish its power of producing an electric cur- 
rent which shall extend to a greater distance across the acid, 
and be discharged only through the copper or platina plate 
which is associated with it for the purpose of forming a voltaic 
apparatus- 

* Quarterly Journal of Science, 1831, p. 388 ; or Bibliotheque Universelle, 
1830, p. 391, 



304 Amalgamated zinc in the battery. [Series VIII. 

999. All these evils are removed by the employment of an 
amalgam of zinc in the manner recommended by Mr. Kemp*, 
or the use of the amalgamated zinc plates of Mr. Sturgeon 
(863.), who has himself suggested a^d objected to their appli- 
cation in galvanic batteries ; for he says, Were it not on ac- 
count of the brittleness and other inconveniences occasioned by 
the incorporation of the mercury with the zinc, amalgamation 
of the zinc surfaces in galvanic batteries would become an im- 
portant improvement ; for the metal would last mtich longer, 
and remain bright for a considerable time, even for several 
successive hours; essential considerations in the employment 
of this apparatus.” f 

1000. Zinc so prepared, even though impure, does not sen- 
sibly decompose the water of dilute # sulphuric acid, but still 
has such affinity for the oxygen, that the moment a metal 
which, like copper or platina, has little or no affinity, touches 
it in the acid, action ensues, and a powerful and abundant elec- 
tric current is produced. It is probable that the mercury acts 
by bringing the surface, in consequence of its fluidity, into one 
uniform condition, and preventing those differences in charac- 
ter between one spot and another which are necessary for the 
formation of the minute voltaic circuits referred to (998.). If 
any difference does exist at the first moment, with regard to 
the proportion of zinc and mercury, at one spot on the surface , 
as compared with another, tlfat spot having the least mercury 
is first acted on, and, by solution of the zinc, is soon placed 
in the same condition as the other parts, and the whole plate 
rendered superficially uniform. One part cannot, therefore, 
act as a discharger to another ; and hence all the chemical 
power upon the water at its surface is in that equable condition 
(949.), which, ^though it tends to produce an electric current 
through the liquid to another plate of metal which can act as a 
discharger (950.), present no irregularities by which any one 
part, having w eaker affinities for oxygen, can act as a discharger 
to another. Two excellent and important consequences follow 

* Jameson’s Edinburgh Journal, October 1828. 

t Recent Experimental Researches, p. 42, &c, Mr. Sturgeon is of course 
unaware of the definite production of electricity by chemical action, and is in 
fact quoting the experiment as the strongest argument again&t the chemical 
theory of galvanism. ' ^ 



Afril 1834.] Amalgamated zinc battery. 305 

upon this state of the metal. The first is, that the full equi- 
valent of electricity is obtained for the oxidation of a certain 
quantity of zinc ; the second, that a battery constructed with 
the zinc so prepared, and* charged with dilute sulphuric acid, 
is active only whilst the electrodes are connected, and ceases 
to act or be acted upon by the acid the instant the communi- 
cation is broken. 

1001. I have had a small battery of ten pairs of plates thus 
constructed, and am convinced that arrangements of this kind 
will be very important, especially in the development and illus- 
tration of the philosophical principles of the instrument. The 
metals I have used arc amalgamated zinc and platina, con- 
nected together by being soldered to platina wires, the whole 
apparatus having the form of the couronne des tasses. The 
liquid used was dilute sulphuric acid of sp. gr. 1*25. No 
action took place upon the metals except when the electrodes 
M r cre in communication, and then the action upon the zinc was 
only in proportion to the decomposition in the experimental 
cell ; for when the current was retarded there, it was retarded 
also in the battery, and no waste of the powers of the metal 
was incurred. 

1002. In consequence of this circumstance, the acid in the 
cells remained active for a very much longer time than usual. 
In fact, time did not tend to lowci; it in aiiy sensible degree : 
for whilst the metal was preserved to be acted upon at the 
proper moment, the acid also was preserved almost at its first 
strength. Hence a constancy of action far beyond what can 
be obtained by the use of common zinc. 

1003. Another excellent consequence was the renewal, 
during the interval of rest, between two experiments of the 
first and most efficient state. When an amalgamated zinc and 
a platina plate, immersed in dilute sulphuric acid, are first 
connected, the current is very powerful, but instantly sinks 
very much in force, and in some cases actually falls to only an 
eighth or a tenth of that first produced (1036.) . This is due 
to the acid which is in contact with the zinc becoming neutral- 
ized by the oxide formed ; the continued quick oxidation of 
the metal being thus prevented. With ordinary zinc, the evolu- 
tion of gas at its surface tends to mingle all the liquid together, 
and thus bring fresh acid against the metal, by which the 



306 Amalgamated zinc battery. [Series VIH* 

oxide formed there can be removed. With the amalgamated 
zinc battery, at every cessation of the current, the saline solu- 
tion against the zinc is gradually diffused amongst the rest of 
the liquid ; and upon the renewal of contact at the electrodes, 
the zinc plates are found most favourably circumstanced for 
the production of a ready and powerful current. 

1001. It might at first be imagined that amalgamated 
zinc would be much inferior in force to common zinc, because 
of the lowering of its energy, which the mercury mi^ht be sup- 
posed to occasion over the whole of its surface ; but this is not 
the case. When the electric currents of two pairs of platina 
and zinc plates were opposed, the difference being that one of 
the zincs was amalgamated and the other not, the current 
from tire amalgamated zinc was most powerful, although no 
gas was evolved against it, and much was evolved at the sur- 
face of the unamalgamated metal. Again, as Davy has shown*, 
if amalgamated and unamalgamated zinc be put in contact, and 
dipped into dilute sulphuric acid, or other exciting fluids, the 
former is positive to the latter, /. e. the current passes from 
the amalgamated zinc, through the fluid, to the unprepared 
zinc. This lie accounts for by supposing that “ there is not 
any inherent and specific property in each metal which gives it 
the electrical character, but that it depends upon its peculiar 
state — on that form of aggregation which fits it for chemical 
change.” 

1005. The superiority of the amalgamated fcinc is not, how- 
ever, due to any such cause, but is a very simple consequence of 
the state of the fluid in contact with it ; for as the unprepared 
zin'c acts directly and alone upon the fluid, whilst that which is 
amalgamated does not, the former (by the oxide it produces) 
quickly neutralizes the acid in contact with its surface, so that 
the progress of oxidation is retarded, whilst at the surface of 
the amalgamated zinc, any oxide formed is instantly removed 
by the free acid present, and the clean metallic surface is always 
ready to act with full energy upon the water. Hence its supe- 
riority (1037.) . 

1006. The progress of improvement in the voltaic battery 
and its applications, is evidently in the contrary direction at 
present to what it was a few years ago ; for in place of increasing 

* Philosophical Transactions, 1826, p. 405. 



30 7 


April 1834.] Resistance to electrolysis . 

the number of plates, the strength of acid, and the extent alto- 
gether of the instrument, the change is rather towards its first 
state of simplicity, but with a far more intimate knowledge and 
application of the princi files which govern its force and action. 
Effects of decomposition can now be obtained with ten pairs of 
plates (417.), which required five hundred or a thousand pairs 
for their production in the first instance. The capability of 
decomposing fused chlorides, iodides, and other compounds, 
according to the law before established (380. &c.), and the op- 
portunity of collecting certain of the products, without any loss, 
by the use of apparatus of the nature of those already described 
(789. 814. &c.), render it probable that the voltaic battery may 
become a useful and even economical manufacturing instrument; 
for theory evidently indicates that an equivalent of a rare sub- 
stance may be obtained at the expense of three or four equiva- 
lents of a very common body, namely, zinc : and practice seems 
thus far to justify the expectation. In this point of view 1 
think it very likely that plates of platina or silver may be used 
instead of plates of copper with advantage, and that then the 
evil arising occasionally from solution of the copper, and its 
precipitation on the zinc, (by which the electro-motive power 
of the zinc is so much injured,) will be avoided (1017.). 

If iv. On the resistance of art Electrolyte to Electrolytic 
Action and on Interpositions. 

1007. I have already illustrated, in the simplest possible 
form of experiment (891. 910.), the resistance established at 
the place of decomposition to the force active at the exciting 
place. I purpose examining the effects of this resistance moi-c 
generally ; but it is rather with reference to their practical in- 
terference with the action and phenomena of the voltaic battery, 
than with any intention at this time to offer a strict and philo- 
sophical account of their nature. Their general and principal 
cause is the resistance of the chemical affinities to be overcome ; 
but there are numerous other circumstances which have a joint 
influence with these forces (1034. 1040. &c.), each of which 
would require a minute examination before a correct account 
of the whole could be given. 

1008. As it will be convenient to describe the experiments 

x 2 



308 Resistance to electrolysis. [Series VIII. 

in a form different to that in which they were made, both forms 
'shall first be explained. Plates of platina, copper, zinc, and 
other metals, about three quarters of an inch wide and three 
inches long, were associated together in pairs by means 
of platina wires to which they were soldered, fig. 88, the 
plates of one pair being either alike or different, as might 
be required. These were arranged in glasses, fig. 89, so as to 
form Volta’s crown of cups. The acid or fluid in the cups 
never covered th e whole of any plate ; and occasionally small 
glass rods were put into the cups, between the plates, to pre- 
vent their contact. Single plates were used to terminate 
the series and complete the connection with a galvanometer, 
or with a decomposing apparatus (899. 988. &c.), or both. 
Now if fig. 90 be examined and compared with fig. 91, the 
latter may be admitted as representing the former in its 
simplest condition ; for the cups i, ii, and iii of the former, 
with their contents, are represented by the cells i, ii, and iii, of 
the latter, and the metal plates Z and P of the former by the 
similar plates represented Z and P in the latter. The only 
difference, in fact, between the apparatus, fig. 90, and the 
trough represented fig. 91, is that twice the quantity of surface 
of contact between the metal and acid is allowed in the first to 
what would occur in the second. 

1009. When the extreme plates of the arrangement just de- 
scribed, fig. 90, are connected metallically through the galva- 
nometer g> then the whole represents a battery consisting of two 
pairs of zinc and platina plates urging a current forward, which 
has, however, to decompose water unassisted by any direct 
chemical affinity before it can be transmitted across the cell iii, 
and therefore before it can circulate. This decomposition of 
water, which is*opposed to the passage of the current, may, as 
a matter of convenience, be considered as taking place either 
against the surfaces of the two platina plates which’ constitute 
the electrodes in the cell iii, or against the two surfaces of that 
platina plate which separates the cells ii and iii, fig. 91, from 
each other. It is evident that if that plate were away, the bat- 
tery would consist of two pairs of plates and two cells, arranged 
in the most favourable position for the production of a current. 
The platina plate therefore, which being introduced as at 
has oxygen evolved at one surface and hydrogen at the other 



309 


April 1834,] Retarding effect of interposed plates. 

(that is, if the decomposing current passes), may be considered 
as the cause of any obstruction arising from the decomposition 
of water by the electrolytic action of the current ; and I have 
usually called it the interposed plate. 

1010. In order to simplify the conditions, dilute sulphuric 
acid was first used in all the cells, and platina for the interposed 
plates ; for then the initial intensity of the current which tends 
to be formed is constant, being due to the power which zinc 
has of decomposing water ; and the opposing force of decompo- 
sition is also constant, the elements of the water being unassisted 
in their separation at the interposed plates by any affinity or 
secondary action at the electrodes (744.), arising either from 
the nature of the plate itself or the surrounding fluid. 

1011. When only on^ voltaic pair of zinc and platina plates 
was used, the current of electricity was entirely stopped to all 
practical purposes by interposing one platina plate, fig. 92, i. e. 
by requiring of the current that it should decompose water, and 
evolve both its elements, before it should pass. This conse- 
quence is in perfect accordance with the views before given 
(910. 917. 973.). For as the whole result depends upon the 
opposition of forces at the places of electric excitement and 
electro-decomposition, and as water is the substance to be de- 
composed at both before the current can move, it is not to be 
expected that the zinc should liaye such powerful attraction for 
the oxygen, as not only to be able to take it from its associated 
hydrogen, but leave such a surplus of force as, passing to the 
second place of decomposition, should be there able to effect a 
second separation of the elements of water. Such an effect 
would require that the force of attraction between zinc and 
oxygen should under the circumstances be at least twice as 
great as the force of attraction between tne oxygen and 
hydrogen. 

1012. When two pairs of zinc and platina exciting plates 
were used, the current Was also practically stopped by one 
interposed platina plate, fig, 93. There was a very feeble effect 
of a current at first, but it ceased almost immediately. It will 
be referred to, with many other similar effects, hereafter 
(1017.). 

1013. Three pairs of zinc and platina plates, fig. 94, were able 



310 Resistance to electrolysis. [Series VIII. 

to produce a current which could pass an interposed platina 
plate, and effect the electrolyzation of water in cell iv. The 
current was evident, both by the . continued deflexion of the 
galvanometer, and the production of *bubbles of oxygen and 
hydrogen at the electrodes in cell iv. Hence the accumulated 
surplus force of three plates of zinc, which are active in decom- 
posing water, is more than equal, when added together, to the 
force with which oxygen and hydrogen are combined in water, 
and is sufficient to cause the separation of these elements from 
each other. 

1014. The three pairs of zinc and platina plates were now 
opposed by two intervening platina plates, fig. 95. In this case 
the current was stopped. 

1015. Four pairs of zinc and platina plates were also neutral- 
ized by two interposed platina plates, fig. 96. 

1016. Five pairs of zinc and platina, with two interposed 
platina plates, fig. 97, gave a feeble current; there was per- 
manent deflexion at the galvanometer, and decomposition in 
the cells vi and vii. But the current was very feeble ; very 
much less than when all the intermediate plates were removed 
and the two extreme ones only retained : for when they were 
placed six inches asunder in one cell, they gave a powerful cur- 
rent. Hence five exciting pairs, with two interposed obstructing 
plates, do not give a current at all comparable to that of a single 
unobstructed pair. 

1017. I have already said that a very feeble current passed 
when the scries included one interposed platina and two pairs 
of zinc and platina plates (1012.). A similarly feeble current 
passed in every case, and even when only one exciting pair and 
four intervening platina plates were used, fig. 98, a current 
passed which cofild be detected at x, both by chemical action 
on the solution of iodide of potassium, and by the galvano- 
meter. This current I believe to be due to electricity reduced 
in intensity below the point requisite for the decomposition of 
water (970. 984.) ; for water can conduct electricity of such 
low intensity by the same kind of power which it possesses in 
common with metals and charcoal, though it cannot conduct 
electricity of higher intensity without suffering decomposition, 
and then opposing a new force consequent thereon. With an 



April 1834.] Effects of interposed plates. 311 

electric current of, or under this intensity, it is probable that 
increasing the number of interposed pi at in a plates would not 
involve an increased difficulty of conduction. 

1018. In order to obtain* an idea of the additional interfering 
power of each added platina plate, six voltaic pairs and four 
intervening platinas were arranged as in fig. 99 ; a very feeble 
current then passed (985.1017.). When one of the platinas 
was removed so that three intervened, a current somewhat 
stronger passed. With two intervening platinas a still stronger 
current passed ; and with only one intervening platina a very 
fair current was obtained. But the effect of the successive 
plates, taken in the order of their interposition, was very differ- 
ent, as might be expected ; for the first retarded the current 
more powerfully than the » second, and the second more than 
the third. 

1019., In these experiments both amalgamated and unamal- 
gamated zinc were used, but the results generally were the 
same. 

1020. The effects of retardation just described were altered 
altogether when changes were made in the nature of the liquid 
used between the plates, either in what may bo calk'd the ex- 
citing or the retarding cells. Thus, retaining the exciting force 
the same, by still using pure dilute sulphuric acid for that pur- 
pose, if a little nitric acid were added to the liquid in the 
retarding cells, then the transmission of the current was very 
much facilitated. For instance, in the experiment with one 
pair of exciting plates and one intervening plate (1011.) fig. 92, 
when a few drops of nitric acid were added to the contents of 
cell ii, then the current of electricity passed with considerable 
strength (though it soon fell from other causes' (1030, 1040.),) 
and the same increased effect was produced l>y fhe nitric acid 
when many interposed plates were used. 

1021. This seems to be a consequence of the diminution of 
the, difficulty of decomposing water when its hydrogen, instead 
of being absolutely expelled, as in the former eases, is transferred 
to the oxygen of the nitric acid, producing a secondary result 
at the Cathode (752.) ; for in accordance with the chemical 
Views' of the electric current and its action already advanced 
(913.), the water* instead of opposing a resistance to decom- 
position equal to the full amount of the force of mutual at- 



312 Resistance to electrolysis. , [Series VIII. 

traction between its oxygen and hydrogen, has that force coun- 
teracted in part, and therefore diminished by the attraction of 
the hydrogen at the cathode for the oxygen of the nitric acid 
which surrounds it, and with which ft ultimately combines in- 
stead of being evolved in its free state. 

1022. When a little nitric acid was put into the exciting 
cells, then again the circumstances favouring the transmission 
of the current were strengthened, for the intensity of the cur- 
rent itself was increased by the addition (906.) . ^hen there- 
fore a little nitric acid was added to both the exciting and the 
retarding cells, the current of electricity passed with very con- 
siderable freedom. 

1023. When dilute muriatic acid was used, it produced and 
transmitted a current more easily than pure dilute sulphuric 
acid, but not so readily as dilute nitric acid. As muriatic acid 
appears to be decomposed more freely than water (765.), and as 
the affinity of zinc for chlorine is very powerful, it might be 
expected to produce a current more intense than that from the 
use of dilute sulphuric acid ; and also to transmit it more freely 
by undergoing decomposition at a lower intensity (912.) . 

1024. In relation to the effect of these interpositions, it is 
necessary to state that they do not appear to be at all dependent 
upon the size of the electrodes, or their distance from each 
other in the acid, except that when a current can pass , changes 
in these facilitate or retard its passage. For on repeating the 
experiment with one intervening and one pair j>f exciting plates 
(1011.), fig. 92, and in place of the interposed plate P using 
sometimes a mere wire, and sometimes very large plates (1008.), 
and also changing the terminal exciting plates Z and P, so that 
they wei£ sometimes wires only and af others of great size, 
still the results were the same as those already obtained. 

1025. In illustration of the effect of distance, an experiment 
like that described with two exciting pairs and one intervening 
plate (1012), fig. 93, was arranged so that the distance be- 
tween the plates in the third cell could be increased to six or 
eight inches, or diminished 4o the thickness of a piece of inter- 
vening bibulous paper. Still the result was the same in both 
cases, the effect not being sensibly greater, when the plates 
were merely separated by the paper, than when a great way 
apart; so that the principal opposition to .the current in this 



313 


April 1834.] Effects of interposed ptates. 

•case does not depend upon the quantity of intervening electro- 
lytic conductor, but on the relation of its elements to the inten- 
sity of the current , or to the chemical nature of the electrodes 
and the surrounding fluids. 

1026. When the acid was sulphuric acid, increasing its 
strength in any of the cells, caused no change in the effects ; 
it did not produce a more intense current in the exciting cells 
(908.), or cause the current produced to traverse the decom- 
posing cells more freely. But if to very weak sulphuric acid a 
few drops of nitric acid were added, then either one or other 
of those effects could be produced ; and, as might be expected 
in a case like this, where the exciting or conducting action 
bore a direct reference to the acid itself, increasing the strength 
of this (the nitric acid)/ also increased its powers. 

1027. The nature of the interposed plate was now varied to 
show its relation to the phenomena either of excitation or re- 
tardation, and amalgamated zinc was first substituted for pla- 
tina. On employing one voltaic pair and one interposed ziric 
plate, fig. 100, there was as powerful a current, apparently, as 
if the interposed zinc plate was away. Hydrogen was evolved 
against P in cell ii, and against the side of the second zinc in 
cell i ; but no gas appeared against the side of the zinc in cell 
ii, nor against the zinc in cell i. 

1028. On interposing two amalgamated zinc plates, fig. 10], 
instead of one, there was still a powerful current, but inter- 
ference had taken place. On using three intermediate zinc 
plates, fig. 102, there was still further retardation, though 
a good current of electricity passed. 

1029. Considering the retardation as due to the inaction of 
the amalgamated zinc upon the dilute acid, in consequence of 
the slight though general effect of diminished chemical power 
produced by the mercury on the surface, and viewing this in- 
action as the circumstance which rendered it necessary that 
each plate should have its tendency to decompose water as- 
sisted slightly by the electric current, it was expected that 
plates Of the metal in the unamalgamated state would probably 
not require such assistance, and would offer no sensible impe- 
diment to the passing of the current. This expectation was 
fully realized in the use of two and three interposed unamal- 
gamated plates. The electric current passed through them as 



314 


Resistance to eledtrolysis. [Series VIII, 

freely as if there had been no such plates in the way. They* 
offered no obstacle, because they could decompose water with- 
out the current ; and the latter had only to give direction to a 
part of the forces, which would have been active whether, it had 
passed or not. 

1030. Interposed plates of copper were then employed. 
These seemed at first to occasion no obstruction, but after a 
few minutes the current almost entirely ceased. This effect 
appears due to the surfaces taking up that peculiar condition 
(1040.) by which they tend to produce a reverse current ; for 
when one or more of the plates were turned round, which 
could easily be effected with the couronne des tasses form of 
experiment, fig. 90, then the current was powerfully renewed 
for a few moments, and then again cea«ed. Plates of platina 
and copper, arranged as a voltaic pile with dilute sulphuric 
acid, could not form a voltaic trough competent to act for more 
than a few minutes, because of this peculiar counteracting 
effect. 

1031. All these effects of retardation, exhibited by decom- 
position against surfaces for which the evolved elements have 
more or less affinity, or are altogether deficient in attraction, show 
generally, though beautifully, the chemical relations and source 
of the current, and also the balanced state of the affinities at 
the places of excitation and decomposition. In this way they 
add to the mass of evidence in favour of the identity of the 
two ; for they demonstrate, as it were, the antagonism of the 
chemical powers at the electromotive part with the chemical 
powers at the interposed parts ; they show that the first are 
producing electric effects, and the second opposing them ; they 
bring the two into direct relation ; they prove that either can 
determine the other, thus making w r hat appears to be cause 
and effect convertible, and thereby demonstrating that both 
chemical and electrical action are merely two exhibitions of one 
single agent or power (916. &c.). 

1032. It is quite evident, that as water and other electrolytes 
can conduct electricity without suffering decomposition (966.), 
when the electricity is of sufficiently low intensity, it may not 
be asserted as absolutely true in all cases, that_ whenever elec- 
tricity passes through an electrolyte, it produces a definite 
effect of decomposition. But the quantity, of electricity which 



315 


Aprii* 1834.], Remarks on the active battery . 

can pass in a given time through an electrolyte without causing 
decomposition, is so small as to bear no comparison to that re- 
quired in a case of very moderate decomposition, and with 
electricity above the intercity required for electrolyzation, I 
have found no sensible departure as yet from the law of de- 
finite ' electrolytic action developed in the preceding series of 
these Researches (783, &c.). 

1033. I qannot dismiss this division of the present Paper 
without making a reference to the important experiments of 
M. Aug. Dc la Rive on the effects of interposed plates*.. As 
I have had occasion to consider such plates merely as giving 
rise to new decompositions, and in that way only causing ob- 
struction to the passage of the electric current, I was freed 
from the necessity of considering the peculiar effects described 
by that philosopher. I was the more willing to avoid for the pre- 
sent touching upon these, as I must at the same time have en- 
tered into the views of Sir Humphry Davy upon the same sub- 
jeetf, and also those of MarianiniJ and Rittcr§, wliiMi are con- 
nected with it. 

If v. General Remarks on the active Voltaic Battery. 

1034. When the ordinary voltaic battery is brought into 
action, its very activity produces certain effects, which re-act 
upon it, and cause serious deterioration of its power. These 
render it an exceedingly inconstant instrument as to the quan- 
tity of effect which it is capable of producing. They are al- 
ready, in part, known and understood ; but as their importance, 
and that of certain other coincident results, will be more evi- 
dent by reference to the principles and experiments Already 
stated and described, I have thought it would be useful, in this 
investigation of the voltaic pile, to notice them briefly here. 

1035. When the battery is in action, it causes such sub- 
stances to be formed and arranged in contact with the plates as 
very much weaken its power, or even tend to produce a counter 
current. They are considered by Sir Humphry Davy as suf- 
ficient to account for the phenomena of Ritter's secondary 

* Annales de Chimie, tom. xxviii. p. 190 j and M£moires de G<5n&ve. 

+ Philosophical Transactions, 1826, p. 413. 

X Annales de Ohimie, tom. xxxiii. pp. 117, 119, &c. 

§ Journal de Physique, tom. Ivii. pp. 349, 350. 



316 Remarks on the active battery . [Series VIII. 

piles, and also for the effects observed by M. A' De la Rive 
with interposed platina plates*. 

1036. I have already referred to this consequence (1003.), 
as capable, in some cases, of lowering the force of the current 
to one eighth or gne tenth of uhat it was at the first moment, 
and have met with instances in which its interference was very 
great. In an experiment in which one voltaic pair and one in- 
terposed platina plate were used with dilute sulphuric acid in 
the cells fig. 103., the wires of communication were so ar- 
ranged, that the end of that marked 3 could be placed at plea- 
sure upon paper moistened in the solution of iodide of potas- 
sium at x , or directly upon the platina plate there. If, after an 
interval during which ttie circuit had not been complete, the 
wire 3 were placed upon the paper, there was evidence of a cur- 
rent, decomposition ensued, and the galvanometer was af- 
fected. If the wire 3 were made to touch the metal of p, a 
comparatively strong sudden current was produced, affect- 
ing the galvanometer, but lasting only for a moment; the 
effect at the galvanometer ceased, and if the wire 3 were 
placed on the paper at x, no signs of decomposition oc- 
curred. On raising the wire 3, and breaking the circuit al- 
together for a while, the apparatus resumed its first power, re- 
quiring, however, from five to ten minutes for this purpose ; 
and then, as before, on making contact between 3 and p } there 
was again a momentary current, and immediately all the effects 
apparently ceased. 

1037. This effect I was ultimately able to refer to the state 
of the film of fluid in contact with the zinc plate in cell i. 
The afid of that film is instantly neutralized by the oxide 
formed ; *the oxidation of the zinc cannot, of course, go on with 
the same facility as before ; and the chemical action being thus 
interrupted, the voltaic action diminishes with it. The time of 
the rest was required for the diffusion of the liquid, and its re- 
placement by other acid. From the serious influence of this 
cause in experiments with single pairs of plates of different 
metals, in which I was at one time engaged, and the extreme 
care required to avoid it, I cannot help feeling a strong sus- 
picion that it interferes more frequently and extensively than 

i 

* Philosophical Transactions, 1820, p. 418. • 



317 


Aran- 1834.] Remarks on the active battery . 

experimenters are aware of, and therefore direct their atten- 
tion to it. 

1038. In considering the effect in delicate experiments of 
this source of irregularity pf action in the voltaic apparatus, it 
must be remembered that it is only that very small portion of 
matter which is directly in contact with the oxidizable metal 
which has to be considered with reference to the change of its 
nature; and this portion is not very readily displaced from its 
position upbn the surface of the metal (582. 605.), especially if 
that metal be rough and irregular. In illustration of this effect, I 
will quote a remarkable experiment. A burnished platina plate 
(569.) was put into hot strong sulphuric acid for an instant only : 
it was then put into distilled water, -moved about in it, taken 
out, and wiped dry : it wa£ put into a second portion of distilled 
water, moved about in it, and again wiped ; it was put into a 
third portion of distilled water, in which it was moved about 
for nearly eight seconds ; it was then, without wiping, put into 
a fourth portion of distilled water, where it was allowed to re- 
main five minutes. The two latter portions of water were then 
tested for sulphuric acid ; the third gave no sensible appear- 
ance of that substance, but the fourth gave indications which 
were not merely evident, but abundant for the circumstances 
under which it had been introduced. The result sufficiently 
shows with what difficulty that portion of the substance which 
is in contact with the metal leaves ’it ; and as the contact of the 
fluid formed against the plate in the voltaic circuit must be as 
intimate and as perfect as possible, it is easy to see how quickly 
and greatly it must vary from the general fluid in the cells, and 
how influential in diminishing the force of the battery this 
effect must be. 

1039. In the ordinary voltaic pile, the influence of this effect 
will occur in all variety of degrees. The extremities of a trough 
of twenty pairs of plates of Wollaston’s construction were con- 
nected with the volta-electrometer, fig. 66. (711.), of the Seventh 
Series of these Researches, and after five minutes the number 
of bubbles of gas issuing from the extremity of the tube, in 
consequence of the decomposition of the water, noted. With- 
out moving the plates, the acid between the copper and zinc 
Was agitated by the introduction of a feather. The bubbles 
were immediately evolved more rapidly, above twice the num- 



318 Remarks on the active battery . [Series VIII. 

ber being produced in the same portion of time as before. In 
this instance it is very evident that agitation by a feather must 
have been a very imperfect mode of restoring the acid in the 
cells against the plates towards its iflrst equal condition ; and 
yet imperfect as the means were, they more than doubled the 
power of the battery. The first effect of a battery which is 
known to be so superior to the degree of action which the bat- 
tery can sustain, is almost entirely due to the favourable condi- 
tion of the acid in contact with the plates. 

1040. A second cause of diminution in the force of the vol- 
taic battery, consequent upon its own action, is that .extraordi- 
nary state of the surfaces of the metals (969.) which was first 
described, I believe, by Ritter*, to which" he refers the powers 
of his secondary piles, and which han been so well experiment- 
ed upon by Marianini, and also by A. Dc la Rive. If the ap- 
paratus, fig. 103. (1036.), be left in action for an hour or two, 
with the wire 3 in contact with the plate p, so as to allow a free 
passage for the current, then, though the contact be broken for 
ten or twelve minutes, still, upon its renewal, only a feeble cur- 
rent will pass, not at all equal in force to what might be ex- 
pected. Further, if P 1 and P 2 be connected by a metal wire, 
a powerful momentary current will pass from P 2 to P 1 through 
the acid, and therefore in the reverse direction to that produced 
by the action of the zinc in the arrangement; and after this has 
happened, the general current can pass through the whole of 
the system as at first, but by its passage again restores the 
plates P 2 and P 1 into the former opposing condition. This, 
generally, is the fact described by Ritter, Marianini, and De la 
Rive. It has great opposing influence on the action of a pile, 
especially if the latter consist of but a small number of alter- 
nations, and 1ms to pass its current through many interpositions. 
It varies with the solution in which the interposed plates are 
immersed, with the intensity of the current, the strength of the 
pile, the time of action, and especially with accidental dis- 
charges of the plates by inadvertent contacts or reversions of 
the plates during experiments, and must be carefully watched 
in every endeavour to trace the source, strength, and variations 
of the voltaic current. Its effect was avoided in the experi- 
ments already described (1036. &e.)', by making contact be- 
* Journal de Physique, Ivii T p. 849. 



319 


April 1834.] Exhausted charges in battery, 

tween the plates P 1 and V 2 before tlic effect dependent upon 
the state of the solution in contact with the zinc plate was ob- 
served, and by other precautions. 

104L When an appai^tus like fig. 98. (1017.) with several 
platina plates was used, being connected with a battery able to 
force a current through them, the power which they acquired, 
of producing a reverse current, was very considerable. 

1042. Weak and exhausted charges should never be used at 
the same ihme with strong and fresh ones in the different cells 
of a trough, or the different troughs of a battery : the fluid in 
all the cells should be alike, else the plates in the weaker cells, 
in place of assisting, retard the passage of the electricity gene- 
rated in, and transmitted across, the stronger cells. Each zinc 
plate so circumstanced h^s to be assisted in decomposing power 
before the whole current can pass between it and the liquid. 
So, that, if in a battery of fifty pairs of plates, ten of the cells 
contain a weaker charge than the others, it is as if ten decom- 
posing plates were opposed to the transit of the current of forty 
pairs of generating plates (1031.). lienee a serious loss of 
force, and hence the reason why, if the ten pairs of plates were 
removed, flic remaining forty pairs would be much more power- 
ful than the whole fifty. 

1043. Five similar troughs, of ten pairs of plates each, were 
prepared, four of them with a good uniform charge of acid, and 
the fifth with the partially neutralized acid of a used battery. 
Being arranged in right order, and connected with a volta-clec- 
trometer (711.), the wdiole fifty pairs of plates yielded 1*1 cubic 
inch of oxygen and hydrogen in one minute : but on moving one 
of the connecting wares so that only the four well-charged 
troughs should be included in the circuit, they produced with the 
same volta-electrometer 8*4 cubical inches of, gas in the same 
time. Nearly seven-eighths of the power of the four troughs 
had been lost, therefore, by their association with the fifth 
trough. 

1044. The same battery of fifty pairs of plates, after being 
thus used, Wap connected with the volta-electrometer (711.), so 
that by quickly shifting the wires of communication, the cur- 
rent of the whole of the battery, or of any portion of it, could 
be made to pass through the instrument for given portions of 
time in succession^,, JThe whole of the battery evolved 0*9 of a 



320 Remarks on the active battery . [Series VIII. 

cubic inch of oxygen and hydrogen in half a minute ; the forty 
plates evolved 4*6 cubic inches in the same time? the whole 
then evolved 1 cubic inch in the half minute ; the ten Weakly 
charged evolved 04 of a cubic inch a in the time given : and 
finally the whole evolved 115 cubic inch in the standard time* 
The order of the observations was that given ; the results suf- 
ficiently show the extremely injurious effect produced by the 
mixture of strong and weak charges in the same battery*. 

1045. In the same manner associations of strong and weak 
pairs of plates should be carefully avoided, A pair of copper 
and platina plates arranged in accordance with a pair of zinc 
and platina plates in dilute sulphuric acid, were found to stop 
the action of the latter, or even of two pairs of the latter, as 
effectually almost as an interposed plate of platina (1011.), or 
as if the copper itself had been platina. It, in fact, became an 
interposed decomposing plate, and therefore a retarding instead 
of an assisting pair. 

1046. The reversal , by accident or otherwise, of the plates 
in a battery has an exceedingly injurious effect. It is not 
merely the counteraction of the current which the reversed 
plates can produce, but their effect also in retarding even as 
indifferent plates, and requiring decomposition to be effected 
upon their surface, in accordance with the course of the cur- 
rent, before the latter can pass. They oppose the current, 
therefore, in the first place, as interposed platina plates would 
do (1011 — 1018.) ; and to this they add a force of opposition 
as counter- voltaic plates. I find that, in a series of four pairs 
of zinc and platina plates in dilute sulphuric acid, if one pair 
be reversed, it very nearly neutralizes the power of the whole. 

1047. There are many other causes of reaction, retardation, 
and irregularity jn the voltaic battery. Amongst them is the 
not unusual one of precipitation of copper upon the zinc in the 
cells, the injurious effect of which has before been adverted to 
(1006.). But their interest is not perhaps sufficient to justify 
any increase of the length of this paper, which is rather in- 

* The gradual increase in the action of the whole fifty pairs of plates was 
due to the elevation of temperature in the weakly charged trough by the pas- 
sage of the current, in consequence of which the exciting energies of the fluid 
within were increased. 



Apkil 1834.] Electro-chemical decomposition . 321 

tended to be an investigation of the theory of the voltaic pile 
than a particular account of its practical application *. 

Note . — Many of the vieirs and experiments in this Series of 
my Experimental Researches will be seen at once to be cor- 
rections and extensions of the theory of electro-chemical de- 
composition, given in the Fifth and Seventh Scries of these 
Researches^. The expressions I would, now alter are those 
which concern the independence of the evolved elements in rela- 
tion to the poles or electrodes, and the reference of their evolu- 
tion to powers entirely internal (524. 537. 6G1.). The present 
paper fully shows my present views ; and I would refer to para- 
graphs 891. 904. 910. 917. 918. 947. 963. 1007. 1031. &c., as 
stating what they are. I 4iope this note will be considered as 
sufficient in the way of correction at present ; for T would rather 
defer revising the whole theory of eleetro-ehemieal decomposi- 
tion until I can obtain clearer views of the way in which the 
power under consideration can appear at one time as associated 
with particles giving them their chemical attraction, and at 
another as free electricity (493. 957.). — M. F. 

Royal Institution , 

March 31s/, 1834. 

* For further practical results relating to these points of the philosophy of 
the voltaic battery, see Series X. § 17. 1136. — 1160. — Dec. 1838. 



322 


NINTH SERIES. 

§ 15. On the influence by induction of an Electric Current on 
itself: — and on the inductive action of Electric Currents 
generally . 

Received December 18, 1834, — Read January 29, 1835. 

1048. The following investigations relate to a very remarkable 
inductive action of electric currents, or of the different parts of 
the same current (74.), and indicates an immediate connexion 
between such inductive action and the direct transmission of 
electricity through conducting bodies, or even that exhibited 
in the form of a spark. 

1049. The inquiry arose out of a fact communicated to me 
by Mr. Jenkin, which is as follows. If an ordinary wire of 
short length be used as the medium of communication between 
the two plates of an electromotor consisting of a single pair of 
metals, no management will enable the experimenter to obtain 
an electric shock from this wire ; but if the wire which sur- 
rounds an electro-magnet be used, a shock is felt each time the 
contact with the electromotor is broken, provided the end$, of 
the wire be grasped one in each hand. 

1050. Another effect is observed at the same time, which 
has long been known to philosophers, namely, that a bright 
electric spark occurs at the place of disjunction. 

1051. A brief account of these results, with some of a cor- 
responding character which I had observed in using long wires, 
was published in the Philosophical Magazine for 1834* ; and 
I added to them some observations on their nature. Further 
investigations led me to perceive the inaccuracy of my first 
notions and ended in identifying these effects with the phe- 
nomena of induction which I had been fortunate enough to de- 
velop in the First Series of these Experimental Researches 
(1. — 59.) t* Notwithstanding this identity, the extension and 
the peculiarity of the views respecting electric currents which 

* VoL v. pp. 349, 444. f Philosophical. Transactions, 1832, p. 126. 



323 


Deo. 1834.] Action of a current on itself : 

the results supply, lead me to believe that they will be found 
worthy of the attention of the Royal Society. 

1052. The electromotor used consisted of a cylinder of zinc 
introduced between the i*vo parts of a double cylinder of cop- 
per, and preserved from metallic contact in the usual way by 
corks. The zincr cylinder was eight inches high and four inches 
in diameter. Both it and the copper cylinder were supplied 
with stiff yires, surmounted by cups containing mercury ; and 
it was at these cups that the contacts of wires, helices, or elec- 
tro-magnets, used to complete the circuit, were made or broken. 
These cups I will call G and E throughout the rest of this 
paper (1079.). 

1053. Certain helices were constructed, some of which it will 
be necessary to describe.* A pasteboard tube had four copper 
wires, one twenty-fourth of an inch in thickness, wound round 
it, each forming a helix in the same direction from end to end : 
the convolutions of each wire were separated by string, and the 
superposed helices prevented from touching by intervening 
calico. The lengths of the wires forming the helices were 48, 
49‘5, 48, and 45 feet. The first and third wires were united 
together so as to form one consistent helix of 96 feet in length ; 
and the second and fourth wires were similarly united to form 
a second helix, closely interwoven with the first, and 91*5 feet 
in length. These helices may be distinguished by the numbers 
i and ii. They were carefully examined by a powerful current 
of electricity and a galvanometer, and found to have no com- 
munication with each other. 

1054. Another helix was constructed upon a similar paste- 
board tube, two lengths of the same copper wire being used, 
each forty-six feet long. These were united into one Consistent 
helix of ninety-two feet, which therefore was hcarly equal in 
value to either of the former helices, hut was not in close in- 
ductive association with them. It may be distinguished by the 
number iii. 

*1065. fourth helix was constructed of very thick copper 
wire, being one fifth of an inch in diameter ; the length of wire 
used was seventy-nine feet, independent of the straight ter- 
minal portions. 

1056. The principal electro-magnet employed consisted of a 
cylindrical bar of soft iron twenty-five inches long, and one inch 

y2 



324 Self-inductive action of a current . [Series IX. 

and three quarters in diameter, bent into a ring, so that the 
ends nearly touched, and surrounded by three coils of thick 
copper wire, the similar ends of which were fastened together ; 
each of these terminations was soldered to a copper rod, 
serving as a conducting continuation of the wire. Hence . any 
electric current sent through the rods was divided in the helices 
surrounding the ring, into three parts, all of which, however, 
moved in the same direction. The three wires may therefore 
be considered as representing one wire, of thrice the thickness 
of the wire really used. 

1057. Other electro-magnets could be made at pleasure by 
introducing a soft iron rod into any of the helices described 
(1053, &c.). 

1058. The galvanometer which I had occasion to use was 
rough in its construction, having but one magnetic needle, and 
not at all delicate in its indications. 

1059. The effects to be considered depend on the conductor 
employed to complete the communication between the zinc and 
copper plates of the electromotor ; and I shall have to consider 
this conductor under four different forms : as the helix of an 
electro-magnet (1056.) ; as an ordinary helix (1053. &c.) ; as a 
long extended wire, having its course such that the parts can 
exert little or no mutual influence; and as a short wire. In all 
cases the conductor was of capper. 

1060. The peculiar effects are best shown by the electro- 
magnet (1056.) . When it was used to complete the communi- 
cation at the electromotor, there was no sensible spark on 
making contact, but on breaking contact there was a very large 
and bright spark, with considerable combustion of the mercury. 
Then, again, with respect to the shock ; if the hands were 
moistened in Shit and water, and good contact between them 
and the wires retained, no shock could be felt upon making 
contact at the electromotor, but a powerful one on breaking 
contact. 

1061. When the helix i or iii (1053. &c.) was used as the 
connecting conductor, there was also a good spark on breaking 
contact, but none (sensibly) on making contact. On trying to 
obtain the shock from these helices, I could not succeed at first. 
By joining the similar ends of i and ii so as to make the two 
helices equivalent to one helix, having wire of double thickness/ 



Dec. 1834.] Inductive action on breaking contact . 325 

I* could just obtain tho sensation. Using the helix of thick 
wire (1055.) the shock was distinctly obtained. On placing the 
tongue between two plates of silver connected by wires with the 
parts which the hands hud heretofore touched (10(3 1.), there 
was a powerful shock on breaking contact, but none on making 
contact. 

1062. The power of producing these phenomena exists there- 
fore in th^ simple helix, as in the electro-magnet, although by 
no means in the same high degree. 

1063. On putting a bar of soft iron into the helix, it became 
an electro-magnet (1057.), and its power was instantly and 
greatly raised. On putting a bar of copper into the helix, no 
change was produced, the action being that of the helix alone. 
The two helices i and ii, made into one helix of twofold length 
of wire, produced a greater effect than either i or ii alone. 

1064. On descending from the helix to the mere long wire , 
the following effects were obtained. A copper wire, 0*18 of an 
inch in diameter, and 132 feet in length, was laid out upon the 
floor of the laboratory, and used as the connecting conductor 
(1059.) ; it gave no sensible spark on making contact, but pro- 
duced a bright one on breaking contact, yet not so bright as 
that from the helix (1061.). On endeavouring to obtain the 
electric shock at the moment contact was broken, I could not 
succeed so as to make it pass thrpugh the hands ; but by using 
two silver plates fastened by small wires to the extremity of the 
principal wire used, and introducing the tongue between those 
plates, I succeeded in obtaining powerful shocks upon the tongue 
and gums, and could easily convulse a flounder, an eel, or a 
frog. None of these effects could be obtained directly from 
the electromotor, i. e. when the tongue, frog, or flsh was in a 
similar, and therefore comparative manner, interposed in the 
course of the communication between the zinc and copper 
plates, separated everywhere else by the acid used to excite 
the combination, or by air. The bright spark and the shock, 
produced only on breaking contact, are therefore effects of the 
same kind as those produced in a higher degree by the helix, 
and in a still higher degree by the electro-magnet. 

1065. In order to compare an extended wire with a helix, 
the helix i, containing ninety- six feet, and ninety-six feet of the 
same-sized wire lying on the floor of the laboratory, were used 



326 Inductive action on breaking contact . [Series IX. 

alternately as conductors : the former gave a much, brighter 
spark at the moment o£ disjunction than the latter. Again, 
twenty-eight feet of copper wire were made up into a helix, and 
being used gave a good spark on d&j unction at the electro- 
motor; being then suddenly pulled out and again employed, it 
gave a much smaller spark than before, although nothing but 
its spiral arrangement had been changed. 

1066. As the superiority of a helix over a wire isrimportant 
to the philosophy of the effect, I took particular pains to ascer- 
tain the fact with certainty. A wire of copper sixty-seven 
feet long was bent in the middle so as to form a double termi- 
nation which could be communicated with the electromotor ; 
one of the halves of this wire was made into a helix and the 
other remained in its extended condition. When these were 
used alternately as the connecting wire, the helix half gave by 
much the strongest spark. It even gave a stronger spark than 
when it and the extended wire were used conjointly as a double 
conductor. 

1067. When a short wire is used, all these effects disappear. 
If it be only two or three inches long, a spark can scarcely be 
perceived on breaking the junction. If it be ten or twelve 
inches long and moderately thick, a small spark may be more 
easily obtained. As the length is increased, the spark becomes 
proportionately brighter, until from extreme length the resist- 
ance offered by the metal as a conductor begins to interfere 
with the principal result. 

1068. The effect of elongation was well shown thus : 114 feet 
of copper wire, one eighteenth of an inch in diameter, were ex- 
tended on the floor and used as a conductor ; it remained cold, 
but gave a bright spark on breaking contact. Being crossed 
so that the two terminations were in contact near the extremities, 
it was again used as a conductor, only twelve inches now being 
included in the circuit : the wire became very hot from the 
greater quantity of electricity passing through it, and yet the 
spark on breaking contact was scarcely visible. The experiment 
was repeated with a wire one ninth of an inch in diameter and 
thirty-six feet long with the same results. 

1069. That the effects, and also the action, in all these forms 
of the experiment are identical, is evident from the manner 
in which the former can be gradually raised from fhat produced 



327 


Dec. 1834.] Affection of a current when stopped. 

by the shortest wire to that of the most powerful electro-mag- 
net : and this capability of examining what will happen by the 
most powerful apparatus, and then experimenting for the same 
results, or reasoning from them, with the weaker arrangements, 
is of great advantage in making out the true principles of the 
phenomena. 

1070. The action is evidently dependent upon the wire which 
serves as a conductor ; for it varies as that wire varies in its 
length or arrangement. The shortest wire may be considered 
as exhibiting the full effect of spark or shock which the electro- 
motor can produce by its own direct power ; all the additional 
force which the arrangements described can excite being due to 
some affection of the current, either permanent or momentary, 
in the wire itself. That it is a momentary effect, produced only 
at the instant of breaking contact, will be fully proved (1089. 
1100 .). 

1071. No change takes -place in the quantity or intensity of 
the current during the time the latter is continued , from the 
moment after contact is made, up to that previous to disunion, 
except what depends upon the increased obstruction offered to 
the passage of the electricity by a long wire as compared to a 
short wire. To ascertain this point with regard to quantity , 
the helix i (1053*) and the galvanometer (1058.) uere both made 
parts of the metallic circuit used \o connect the plates of a small 
electromotor, and the deflection at the galvanometer was ob- 
served ; then a soft iron core was put into the helix, and as 
soon as the momentary effect was over, and the needle had be- 
come stationary, it was again observed, and found to stand ex- 
actly at the same division as before. Thus the quantity pass- 
ing through the wire when the current was continued was the 
same either with or without the soft iron, although the peculiar 
effects occurring at the moment of disjunction were very dif- 
ferent in degree under such variation of circumstances. 

10 72. That the quality of intensity belonging to the constant 
current did not vary with the circumstances favouring the pe- 
culiar results under consideration, so as to yield an explanation 
of thosb results, was ascertained in the following manner. The 
current excited by an electromotor was passed through short 
wires, and its intensity tried by subjecting different substances 
to its electrolyzing power (912. 966. See .) ; it was then passed 



328 Affection of a current when stopped. [Series IX. 

through the wires of the powerful electro-magnet (1056.), ajrd 
again examined with respect to its intensity by the same means 
and found unchanged. Again, the constancy of the quantity 
passed in the above experiment (107\.) adds further proof that 
the intensity could not have varied ; for had it been increased 
upon the introduction of the soft iron, there is every reason to 
believe that the quantity passed in a given time would also have 
increased. 

1073. The fact is, that under many variations of the experi- 
ments, the permanent current loses in force as the effects upon 
breaking contact become exalted . This is abundantly evident 
in the comparative experiments with long and short wires (1068.); 
and is still more strikingly shown by the following variation. 
Solder an inch or two in length of fine platina wire (about one 
hundredth of an inch in diameter) on to one end of the long 
communicating wire, and also a similar length of the same pla- 
tina wire on to one end of the short communication ; then, in 
comparing the effects of these two communications, make and 
break contact between the platina terminations and the mer- 
cury of the cup G or E (1079.). When the short wire is used, 
the platina will be ignited by the constant current , because of 
the quantity of electricity, but the spark on breaking contact 
will be hardly visible ; on using the longer communicating wire, 
which by obstructing will diminish the current, the platina will 
remain cold whilst the current passes, but give a bright spark 
at the moment it ceases : thus the strange result is obtained 
of a diminished spark and shock from the strong current, and 
increased effects from the weak one. Hence the spark and 
shock at the moment of disjunction, although resulting from 
great intensity and quantity of the current at that moment , are 
no direct indicators or measurers of the intensity or quantity of 
the constant current previously passing, and by which they are 
ultimately produced. 

1074. It is highly important in using the spark as an indica- 
tion, by its relative brightness, of these effects, to bear in mind 
certain circumstances connected * with its production and ap- 
pearance (958.). An ordinary electric spark is understood to 
be the bright appearance of electricity passing suddenly 
through an interval of air, or other badly conducting matter. 



329 


Dec, 1834.] Nature of a spark : precautions , 

4 voltaic spark is sometimes of the same nature, but generally, 
is due to the ignition and even combustion of a minute portion 
of a good conductor ; and that is especially the case when the 
electromotor' consists of Jmt one or few pairs of plates. This 
can be very well observed if either or both of the metallic sur- 
faces intended to touch be solid and pointed. The moment 
they come in contact the current passes ; it heatfc ignites, and 
even burns the touching points, and the appearance is as if the 
spark passed on making contact, whereas it is only a ease of 
ignition by the current, contact being previously made; and is 
perfectly analogous to the ignition of a fine platina wire connect- 
ing the extremities of a voltaic battery. 

1075. When mercury constitutes one or both of the surfaces 
used, the brightness of*the spark is greatly increased. But 
as this effect is due to the action on, and probable combustion 
of, the metal, such sparks must only be compared with other 
sparks also taken from mercurial surfaces, and not with such 
as may be taken, for instance, between surfaces of platina or 
gold, for then the appearances are far less bright, though the 
same quantity of electricity be passed. It is not at all unlikely 
that the commonly occurring circumstance of combustion may 
affect even the duration of the light ; and that sparks taken 
between mercury, copper, or other combustible bodies, will 
continue for a period sensibly longer than those passing between 
platina or gold. 

1076. When the end of a short clean copper wire, attached 
to one plate of an electromotor, is brought down carefully upon 
a surface of mercury connected with the other plate, a spark, 
almost continuous, can be obtained. This I .refer to a succes- 
sion of effects of the following nature : first, contact, — then 
ignition of the touching points, — recession of the mercury from 
the mechanical results of the heat produced at the place of 
contact, and the electro-magnetic condition of the parts at the 
moment*, — breaking of the contact and the production of the 
peculiar intense effect dependent thereon, — renewal of the con- 
tact by the returning surface of the undulating mercury, — and 
then a repetition of the same series of effects, and that with 
such rapidity as to present the appearance of a continued dis- 


* Quarterly Journal of Science, vol. xii. p. 420. 



330 Induction of a current when stopped* [Series DC 

charge. If a long wire or an electro-magnet be used as the 
connecting conductor instead of a short wire, a similar appear- 
ance may be produced by tapping the vessel containing the 
mercury and making it vibrate ; but the sparks do not usually 
follow each other so rapidly as to produce an apparently con- 
tinuous spark, because of the time required, when the long wire 
or electro -mf^net is used, both for the full development of the 
current (1101. 1106.) and for its complete cessation. 

1077. Returning to the phenomena in question, the first 
thought that arises in the mind is, that the electricity circulates 
with something like momentum or inertia in the wire, and that 
thus a long wire produces effects at the instant the current is 
stopped, which a short wire cannot produce. Such an explana- 
tion is, however, at once set aside by the fact, that the same 
length of wire produces the effects in very different degrees, 
according as it is simply extended, or made into a helix, or 
forms the circuit of an electro -magnet (1069.). The experi- 
ments to be adduced (1089.) will still more strikingly show that 
the idea of momentum cannot apply. 

1078. The bright spark at the electromotor, and the shock 
in the arms, appeared evidently to be due to one current in the 
long wire, divided into two parts by the double channel afforded 
through the body and through the electromotor ; for that the 
spark was evolved at the place of disjunction with the electro- 
motor, not by any direct action of the latter, but by a force im- 
mediately exerted in the wire of communication, seemed to be 
without doubt (1070,). It followed, therefore, that by using a 
better conductor in place of the human body, the whole of this 
extra current might be made to pass at that place ; and thus 
be separated from that which the electromotor could produce 
by its immediate action, and its direction be examined apart 
from any interference of the original and originating current. 
This was found to be true ; for on connecting the ends of the 
principal wire together by a cross wire two or three feet in 
length, applied just where the hands had felt the $h<>ck, the 
whole of the extra current passed by the new channel, and then 
no better spark than one producible by a short wire was obtained 
on disjunction at the electromotor. 

1079. The current thus separated was examined by galva- 



331 


Dec. 1 - 834 .} Analysis of the effect . 

ntfmeters and decomposing apparatus introduced into the 
course of this wire. I will always speak of it as the current 
in the cross wire or wires,, so that no mistake, as to its place or 
origin, may occur. In tie wood -cut, Z 
and C represent the zinc and copper 
plates of the electromotor ; G and E the 
cups of mercury where contact is made 
or broken *(1052.) ; A and B the termi- x 
nations of D, the long wire, the helix, or 
the electro-magnet, used to complete the 
circuit ; N and P are the cross wires, . 
which can either he brought into contact j 
at x } or else have a galvanometer (1058.) 
or an electrolyzing apparatus (312. 310.) interposed there. 

The production of the shock from the current in the cross 
wire, whether D was a long extended wire, or a helix, or an 
electro-magnet, has been already described (100k 1001. 1000.). 

1080. The spark of the cross-wire current could be produced 
at x in the following manner : D was made an electro-magnet ; 
the metallic extremities at x were held close together, or rubbed 
lightly against each other, whilst contact was broken at G or k. 
When the communication was perfect at x } little or no spark 
appeared at G or E. When the condition of vicinity at x was 
favourable for the result required, a bright spark would pass 
there at the moment of disjunction, none occurring at G and 
E ; this spark was the luminous passage of the extra current 
through the cross-wires. When there was no contact or pas- 
sage of current at x, then the spark appeared at G or E, the 
extra current forcing its way through the electromotor itself. 
The same results were obtained by the use of the helix or the 
extended wire at D in place of the electro-magnet. 

1081 . On introducing a fine platina wire at x y and employing 
the electro-magnet at D, no visible effects occurred as long as 
contact was continued ; but on breaking contact at G or E, the 
fine wire was instantly ignited and fused. A longer or thicker 
wire eottld be so adjusted at x as to show ignition, without 
fusion, every time the contact was broken at G or E. 

1082. It is rather difficult to obtain this effect with helices 
or witfes^ and for very simple reasons : with the helices i, ii, or 
iiij, there was such retardation of the electric current, from the 




332 


Effects of the induced current. [Series IX. 

length of wire used, that a full inch o£ platina wire one fiftieth 
of an inch in diameter could be retained ignited at the cross- 
wires during the continuance of contact , by the portion of elec- 
tricity passing through it. Hence it w impossible to distinguish 
the particular effects at the moments of making or breaking 
contact from this constant effect. On using the thick wire helix 
(1055.), the same results ensued. 

1083. Proceeding upon the known fact that electric currents 
of great quantity but low intensity, though able to ignite thick 
wires, cannot produce that effect upon thin ones, I used a very 
fine platina wire at x, reducing its diameter until a spark ap- 
peared at G or E, when contact was broken there. A quarter 
of an inch of such wire might be introduced at x without being 
ignited by the continuance of contact at G or Ej but when 
contact was broken at either place, this wire became red hot ; 
proving, by this method, the production of the induced current 
at that moment. 

1084. Chemical decomposition was next effected by the cross- 
wire current, an electro-magnet being used at D, and a decom- 
posing apparatus, with solution of iodide of potassium in paper 
(1079.), employed at x. The conducting power of the connecting 
system A B D was sufficient to carry all the primary current, 
and consequently no chemical action took place at x during the 
continuance of contact at G «and E ; but when contact was 
broken, there was instantly decomposition at x. The iodine 
appeared against the wire N, and not against the wire P ; thus 
demonstrating that the current through the cross-wires, when 
contact was broken, w as in the reverse direction to that marked 
by the arrow, or that which the electromotor would have sent 
through iff. 

1085. In this* experiment a bright spark occurs at the place 
of disjunction, indicating that only a small part of the extra 
current passed the apparatus at x y because of the small conduct- 
ing power of the latter. 

1086. I found it difficult to obtain the chemical effects with 
the simple helices and wires, in consequence of the diminished 
inductive power of these arrangements, and because of the pas- 
sage of a strong constant current at x whenever a very active 
electromotor was used (1082.) . 

1087. The most instructive set of results was obtained, how- 



Dec. 1834.] Induction of a current. 333 

ever, when the galvanometer was introduced at x. Using an 
electro-magnet at D, and continuing contact, a current was then 
indicated by the deflection, proceeding from P to N, in the direc- 
tion of the arrow ; the cr<pss-wire serving to carry one part of 
the electricity excited by the electromotor, and that part of the 
arrangement marked A B D, the other and far greater part, as 
indicated by the arrows. The magnetic needle was then forced 
back, by pins applied upon opposite sides of its two extremities, 
to its natural position when uninfluenced by a current ; after 
which, contact being broken at G or E, it was deflected strongly 
in the opposite direction ; thus showing, in accordance with the 
chemical effects (1084,), that the extra current followed a 
course in the cross -wires contrary to that indicated by the arrow, 
i. e. contrary to the one produced by the direct action of the 
electromotor*. 

1088. With the helix only (10(31.), these effects could scarcely 
be observed, in consequence of the smaller inductive force of 
this arrangement, the opposed action from induction in the 
galvanometer wire itself, the mechanical condition and tension 
of the needle from the effect of blocking (1087.) whilst the cur- 
rent due to continuance of contact was passing round it ; and 
because of other causes. With the extended wire (1064.) all 
these circumstances had still greater influence, and therefore 
allowed less chance of success. 

1089. These experiments, establishing as they did, by the 
quantity, intensity, and even direction, a distinction between 
the primary or generating current and the extra current, led 
me to conclude that the latter was identical with the induced 
current described (6. 26. 74.) in the First Series of these Re- 
searches ; and this opinion I was soon able to bring to proof, 
and at the same times obtained not the partial (1078.) but 
entire separation of one current from the other. 

1090. The double helix. (1053.) was arranged so that it should 
form the connecting wire between the plates of the electromotor, 
ii being out of the current, and its ends unconnected. In this 
condition i acted very well, and gave a good spark at the time 

# It was ascertained experimentally, that if a strong current was passed 
through the galvanometer only, and the needle restrained in one direction as 
above in its natural position, when the current was stopped, no vibration of 
the needle in the opposite direction took place. 



834 Induction by a current . [Series IX. 

and place of disjunction. The opposite ends of ii were tl^en 
connected together so as to form an endless wire, i remaining 
unchanged ; but now no spark , or one scarcely sensible, could 
be obtained from the latter at the plaice of disjunction. Then, 
again, the ends of ii were held so nearly together that any cur- 
rent running round that helix should be rendered visible as a 
spark ; and in this manner a spark was obtained from ii when 
the junction of i with the electromotor was broken, ^in place of 
appearing at the disjointed extremity of i itself. 

1091. By introducing a galvanometer or a decomposing ap- 
paratus into the circuit formed by the helix ii, I could easily 
obtain the deflections and decomposition occasioned by the in- 
duced current due ‘to the breaking contact at helix i, or even to 
that occasioned by making contact of* that helix with the elec- 
tromotor ; the results in both cases indicating the contrary di- 
rections of the two induced currents thus produced (26.) . 

1092. All these effects, except those of decomposition, were 
reproduced by two extended long wires, not having the form of 
helices, but placed close to each other ; and thus it was proved 
that the extra current could be removed from the wire carrying 
the original current to a neighbouring wire, and was at the 
same time identified, in direction and every other respect, with 
the currents producible by induction (1089.), The case, there- 
fore, of the bright spark and shock on disjunction may now be 
stated thus : If a current be established in a w r ire, and another 
wire, forming a complete circuit, be placed parallel to the first, 
at the moment the current in the first is stopped it induces a 
current in the same direction in the second, the first exhibiting 
then but a feeble spark ; but if the second wire be away, dis- 
junction of the first wire induces a current in itself in the same 
direction, producing a strong spark. The strong spark in the 
single long wire or helix, at the moment of disjunction, is there- 
fore the equivalent of the current which would be produced in 
a neighbouring wire if such second current were permitted. 

1093. Viewing the phenomena as the results of the induction 
of electrical currents, many of the principles of action, in the 
former experiments, become far more evident and precise. Thus 
the different effects of short wires, long wires, helices, and elec- 
tro-magnets (1069.) may be comprehended. If the inductive 
action of a wire a foot long upon a collateral- wire also a foot in 



333 


Dec. 1834.] Effects of induction vanned. 

length, be observed, it will be found very small; but if tbc 
same current be sent through a wire fifty feet long, it will in- 
duce in a neighbouring wire of fifty feet a far more powerful 
current at the moment of making or breaking contact, each 
successive foot of wire adding to the sum of action ; and by pa- 
rity of reasoning, a similar effect should take place when the 
conducting wire is also that in which the induced current is 
formed (74.) : hence the reason why a long wire gives a brighter 
spark on breaking contact than a short one (1068.), although 
it carries much less electricity. 

1094. If the long wire be made into a helix, it will then be 
still more effective in producing sparks and shocks on breaking 
contact • for by the mutual inductive action of the convolutions 
each aids its neighbour, and will be aided in turn, and the sum 
of effect will be very greatly increased. 

1093. If an electro-magnet be employed, the effect will be 
still more highly exalted ; because the iron, magnetized by the 
power of the continuing current, will lose its magnetism at the 
moment the current ceases to pass, and in so doing will tend to 
produce an electric current in the wire around it (37. 38.), in 
conformity with that which the cessation of current in the helix 
itself also tends to produce. 

1096. By applying the laws of the induction of electric cur- 
rents formerly developed '(6. &c.) ^various new conditions of the 
experiments could be devised, which by their results should 
serve as tests of the accuracy of the view just given. Thus, if 
a long wire be doubled, so that the current in the two halves 
shall have opposite actions, it ought not to give a sensible spark 
at the moment of disjunction : and this proved to be the case, 
for a wire forty feet long, covered with silk, being doubled and 
tied closely together to within four inches of the extremities, when 
used in that state, gave scarcely a perceptible spark ; but being 
opened out and the parts separated, it gave a very good one. 
The two helices i and ii being joined at their similar ends, and 
then used at their other extremities to connect the plates of the 
electromotor, thus constituted one long helix, of which one half 
was opposed in direction to the other half : under these circum- 
stances it gave scarcely a sensible spark, even when the soft 
iron core was within, although containing nearly two hundred 



336 Induction of electricaL currents. [Series IX. 

feet of wire. When it was made into one consistent helix # of 
the same length of wire it gave a very bright spark. 

1097. Similar proofs can be drawn from the mutual inductive 
action of two separate currents (lllCf.) ; and it is important for 
the general principles that the consistent action of two such 
currents should be established. Thus, two currents going in 
the same direction should, if simultaneously stopped, aid each 
other by their relative influence ; or if proceeding in contrary 
directions should oppose each other under similar circum- 
stances. I endeavoured at first to obtain two currents from two 
different electromotors, and passing them through the helices i 
and ii, tried to effect the disjunctions mechanically at the same 
moment. But in this I could not succeed ; one was always 
separated before the other, and in that case produced little or 
no spark, its inductive power being employed in throwing a cur- 
rent round the remaining complete circuit (1090.) : the current 
which was stopped last always gave a bright spark. If it were ever 
to become needful to ascertain whether two junctions were accu- 
rately broken at the same moment, these sparks would afford a 
test for the purpose, having an infinitesimal degree of perfection. 

1098. I was able to prove the points by other expedients. 
Two short thick wires were selected to serve as terminations, 
.by which contact could be made or broken with the electro- 
motor. The compound helix, consisting of i and ii (1053.), was 
adjusted so that the extremities of the two helices could be 
placed in communication with the two terminal wires, in such a 
manner that the current moving through the thick wires should 
be divided into two equal portions in the two helices, these por- 
tions travelling, according to the mode of connexion, either in 
the same f direction or in contrary directions at pleasure. In 
this manner twq streams could be obtained, both of which could 
be stopped simultaneously, because the disjunction could be 
broken at G or F by removing a single wi^e. When the helices 
were in contrary directions, there was scarcely a sensible spark 
at the place of disjunction ; but when they were in accordance 
there was a very bright one. 

1099. The helix i was now used constantly, being sometimes 
associated, as above, with helix ii in an according direction, 
and sometimes with helix iii, which was placed at a little di- 



Dec. 1834.] Induction on commencing a current. 387 

ststfice. The association i and ii, which presented two currents 
able to affect each other by induction, because of their vicinity, 
gave a brighter spark than the association i and iii, where the 
two streams could not extort their mutual influence ; but the 
difference was not so great as I expected. 

• 1100. Thus all the phenomena tend to prove that the effects 
are due to an inductive action, occurring at tlie moment when 
the principal current is stopped. I at one time thought they 
were due to an action continued during the whole time of the 
current, and expected that a steel magnet would have an* influ- 
ence according to its position in the helix, comparable to that 
of a soft iron bar, in assisting the effect. This, however, is 
not the case ; for hard steel, or a magnet in the helix, is not 
so effectual as soft iron; nor does it make any difference how 
the magnet is placed in the helix, and for very simple reasons, 
namely, that the effect does not depend upon a permanent state 
of the core, but a change of state ; and that tin* magnet or hard 
steel cannot sink through such a difference of state as soft iron, 
at the moment contact ceases, and therefore cannot produce an 
equal effect in generating a current of electricity by induction 
(31.37.). 


1101. As an electric current acts by induction with equal 
energy at the moment of its commencement as at the moment of 
its cessation (10. 26.), but in a contrary direction, the reference 
of the effects under examination to an inductive action, would 
lead to the conclusion that corresponding effects of an opposite 
nature must occur in a long wire, a helix, or an clcetro-rnagnet, 
every time that contact is made with the electromotor. These 
effects will tend to establish a resistance for the first*, moment 
in the long conductor, producing a result equivalent to the re- 
verse of a shock or a spark. Now it is very difficult to devise 
means fit for the recognition of such negative results; but as 
it is probable that some positive effect is produced at the time, 
if we knew what to expect, I think the few facts bearing upon 
this subject with which I am acquainted are worth recording. 

1102. The electro-magnet was arranged with an electroly- 
zing apparatus at oc > as before described (1084.), except. that 
the intensity of the chemical action at the electromotor was in- 
creased until the electric current was just able to produce the 



338 Inductive action of an electric current . [Series IX. 

feeblest signs of decomposition whilst contact was continued at 
G and E (1079.) ; (the iodine of course appearing against the 
end of the cross wire P ;) the wire N was also separated from 
A at r, so that contact there could be made or broken at plea- 
sure. Under these circumstances the following set of actions 
was repeated several times : contact was broken at r, then 
broken at G, next made at r y and lastly renewed at G ; thus 
any current from N to P due to breaking of contact was avoid- 
ed, but any additional force to the current from P to N due to 
making contact could be observed. In this way it was found, 
that a much greater decomposing effect (causing the evolution 
of iodine against P) could be obtained by a few completions of 
contact than by the current which could pass in a much longer 
time if the contact was continued. This I attribute to the act 
of induction in the wire A B D at the moment of contact ren- 
dering that wire a worse conductor, or rather retarding the 
passage of the electricity through it for the instant, and so throw- 
ing a greater quantity of the electricity which the electromotor 
could produce, through the cross wire passage N P. The in- 
stant the induction ceased, A B I) resumed its full power of 
carrying a constant current of electricity, and could have it 
highly increased, as we know by the former experiments (1060.) 
by tne opposite inductive action brought into activity at the 
moment contact at Z or C w,as broken. 

1103. A galvanometer was then introduced at x , and the 
deflection of the needle noted whilst contact was continued at 
G and E ; the needle was then blocked as before in one direction 
(1087.), so that it should not return when the current ceased, 
but remain in the position in which the current could retain it. 
Contact lit G or E was broken, producing of course no visible 
effect ; it was Hhen renewed, and the needle was instantly de- 
flected, passing from the blocking pins to a position still further 
from its natural place than that which the constant current 
could give, and thus showing, by the temporary excess of cur- 
rent in this cross communication, the temporary retardation in 
the circuit ABB. 

1104. On adjusting a platina wire at % (1081.) so v that it 
should not be ignited by the current passing through itr whilst 
contact at G and E was continued, and yet become red hot by 
a current' somewhat more powerful, X was readily able to pro- 



Dec. 1834.] 


On producing the current . 


339 


dqce its ignition upon making contact , and again upon breaking 
contact . Thus the momentary retardation in A B D on making 
contact was again shown by this result, as well also as the op- 
posite result upon breaking contact. The two ignitions of the 
wire at % were of course produced by electric currents moving 
in opposite directions. 

1105. Using the helix only, I could not obtain distinct de- 
flections a£ x, due to the extra effect on making contact, for the 
reasons already mentioned (1088.) . By using a vei*y fine platina 
wire there (1083.), I did succeed in obtaining the igniting' effect 
for making contact in the same manner, though by no means to 
the same degree, as with the electro-magnet (1101<.). 

1106. We may also consider and estimate the effect on making 
contact , by transferring liie force of induction from the wire 
carrying the original current to a lateral wire, as in the eases 
described (1090.); and we then are sure, both by the chemical 
and galvanometrical results (1091 .), that the forces upon making 
and breaking contact, like action and reaction, arc equal in their 
strength but contrary in their direction. If, therefore, the effect 
on making contact resolves itself into a mere retardation of the 
current at the first moment of its existence, it must be, in its 
degree, equivalent to the high exaltation of that same current 
at the moment contact is broken. 

1107. Tims the case, under thg circumstances, is, that the 
intensity and quantity of electricity moving in a current are 
smaller when the current commences or is increased, and greater 
when it diminishes or ceases, than they would be if the induct- 
ive action occurring at these moments did not take place; or 
than they are in the original current wire if the inductive action 
be transferred from that wire to a collateral one (1090.). 

1108. From the facility of transference to neighbouring wires, 
and from the effects generally, the inductive forces appear to 
be lateral, i . e. exerted in a direction perpendicular to the 
direction of the originating and produced currents ; and they 
also appear to be accurately represented by the magnetic curves, 
and closely related to, if not identical with, magnetic forces. 

1109. There can be no doubt that the current in one part of 
a wire can act by induction upon other parts of the same ■ wire 
^hieh are lateral to the first, i, e. in the same vertical section 
(74.), or in parts which are more or less oblique to it 

z 2 



340 Inductive action of an electric current. [Series IX. 

(1112.), just as it can act in producing a current in a neigh- 
bouring wire or in a neighbouring coil qf the same wire. It is 
this which gives the appearance of the current acting upon 
itself; but all the experiments and* all analogy tend to show 
that the elements (if I may so say) of the currents do not act 
upon themselves, and so cause the effect in question, but pro- 
duce it by exciting currents in conducting matter which is lateral 
to them. 

1110. It is possible that some of the expressions I have used 
may seem to imply, that the inductive action is essentially the 
action of one current upon another, or of one clement of a cur- 
rent upon another element of the same current. To avoid any 
such conclusion I must explain more distinctly my meaning. If 
an endless wire be taken, we have the means of generating a 
current in it which shall run round the circuit without adding 
any electricity to what was previously in the wire. As far as 
we can judge, the electricity which appears as a current is the 
same as that which before was quiescent in the wire ; and though 
we cannot as yet point out the essential condition of difference 
of the electricity at such times, we can easily recognise the two 
states. Now when a current acts by induction upon conducting 
matter lateral to it, it probably acts upon the electricity in that 
conducting matter whether it be in the form of a current or 
quiescent , in the one case increasing or diminishing the current 
according to its direction, in the other producing a current, and 
the amount of the inductive action is probably the same in both 
cases. Hcncc, to say that the action of induction depended 
upon the mutual relation of two or more currents, would, ac- 
cording to the restricted sense in which the term current is 
understood at present (283. 517. 667.), be an error. 

1111. Several of the effects, as, for instances, those with 
helices (1066.), with according or counter currents (1097. 1098.), 
and those on the production of lateral currents (1090.), ap- 
peared to indicate that a current could produce an effect of in- 
duction in a neighbouring wire more readily than in its own 
carrying wire, in which case it might be expected that some 
variation of result would be produced if a bundle of wires were 
used as a conductor instead of a single wire. In consequence 
the following experiments were made. A copper wire one 
twenty-third of an inch in diameter was cut into lengths of five 



341 


Dec. 1834 .] Induction of a continuous current. 

feet each, and six of these being laid side by side in one bundle, 
had their opposite extremities soldered to two terminal pieces 
of copper. This arrangement could be used as a discharging 
wire, but the general current could be divided into six parallel 
streams, which might be brought close together, or, by the 
separation of the wires, be taken more or less out of each other's 
influence. A somewhat brighter spark was, 1 think, obtained 
on breaking contact when the six wires were close together than 
when held asunder. 

1112. Another bundle, containing twenty of these wires, was 
eighteen feet long ; the terminal pieces were one-fifth of an inch 
in diameter, and each six inches long. This was compared 
with nineteen feet in length of copper w ire one-fifth of an inch 
in diameter. The bundle gave a smaller spark on breaking 
contact than the latter, even when its strands were held together 
by string ; when they were separated, it gave a still smaller 
spark. Upon the whole, however, the diminution of effect was 
not such as I expected ; and I doubt whether the results can 
be considered as any proof of the truth of the supposition which 
gave rise to them. 

1113. The inductive force by which two elements of one cur- 
rent (1109. 1110.) act upon each other, appears to diminish as 
the line joining them becomes oblique to the direction of the 
current, and to vanish entirely whan it is parallel. 1 am led by 
some results to suspect that it then e\en passes into the repul- 
sive force noticed by Ampere * ; which is the cause of the ele- 
vations in mercury described by Sir Humphry Davyt, and 
which again is probably directly connected w r ith the quality of 
intensity. 

1114. Notwithstanding that the effects appear only at the 
making and breaking of contact, (the current remaining unaf- 
fected, seemingly, in the interval,) I cannot resist the impression 
that there is some connected and correspondent effect produced 
by this lateral action of the elements of the electric stream 
during the time of its continuance (60. 242.). An action of 
this kind, in fact, is evident in the magnetic relations of the parts 
of the current. But admitting (as we may do for the moment) 
the magnetic forces to constitute the power which produces 'such 
striking and different results at the commencement and termi- 

, * Recueil d’Obeert&tione Electro-Dynamiques, p. 285. 

- f Philosophical Transactions, 1823, p. 1 55. 



34 2 Continuous current ; — its inductive action . [Series IX. 

nation of a current, still there appears to be a link in the ch&in 
of effects, a wheel in the physical mechanism of the action, as 
yet unrecognised. If we endeavour to consider electricity and 
magnetism as the results of two forces of a physical agent, or a 
peculiar condition of matter, exerted in determinate directions 
perpendicular to each other, then, it appears to me, that we 
must consider these two states or forces as convertible into each 
other in a greater or smaller degree ; i. e. that an eldtncnt of an 
electric current has not a determinate electric force and a de- 
terminate magnetic force constantly existing in the same ratio, 
but that the two forces are, to a certain degree, convertible by 
a process or change of condition at present unknown to* us. 
How else can a current of a given^ intensity and quantity be 
able, by its direct action, to sustain a state which, when allowed 
to react, (at the cessation of the original current,) shall produce 
a second current, having an intensity and quantity far greater 
than the generating one ? This cannot result from a direct re- 
action of the electric force ; and if it result from a change of 
electrical into magnetic force, and a reconversion back again, it 
will show that they differ in something more than mere direction, 
as regards that agent in the conducting wire which constitutes 
their immediate cause. 

1115. With reference to the appearance, at different times, 
of the contrary effects produced by the making and breaking 
contact, and their separation by an intermediate and indifferent 
state, this separation is probably more apparent than real. If 
the conduction of electricity be effected by vibrations (283.), or 
by any other mode in which opposite forces are successively 
and rapidly excited and neutralized, then we might expect a 
peculiar and contrary development of force at the commence- 
ment and termination of the periods during which the conducting 
action should last (somewhat in analogy with the colours 
produced at the outside of an imperfectly developed solar 
spectrum) : and the intermediate actions, although not sensible 
in the same way, may be very important and, for instance, 
perhaps constitute the very essence of conductibility. It is 
by views and reasons such as these, which seem to me con- 
nected with the fundamental laws and facts of electrical science, 
that I have been induced to enter, more minutely than I Other- 
wise should have done, into the experimental examination of 



343 


Dec. 1834.] Inductive action of a current . 

J.116. Before concluding, I may briefly remark, that on 
using a voltaic battery of fifty pairs of plates instead of a single 
pair (1052.), the effects were exactly of the same kind. The 
spark on making contact, £or the reasons before given, was very 
small (1101. 1107.) ; that on breaking contact, very excellent 
and brilliant. The continuous discharge did not seem altered 
in character, whether a short wire or the powerful clcctro-mag- 
net were u^ed as a connecting discharger. 

1117. The effects produced at the commencement and end 
of a current, (which are separated by an interval of time' when 
that current is supplied from a voltaic apparatus,) must occur 
at the same moment when a common electric discharge is passed 
through a long wire. Whether, if happening accurately at the 
same moment, they worfld entirely neutralize each other, or 
whether they would not still give some definite peculiarity to 
the discharge, is a matter remaining to be examined; but it is 
very probable that the peculiar character and pungency of sparks 
drawn from a long wire depend in part upon the increased in- 
tensity given at the termination of the discharge by the inductive 
action then occurring. 

1118. In the wire of the helix of magneto-electric machines, 
(as, for instance, in Mr. Saxton's beautiful arrangement,) an 
important influence of these principles of action is evidently 
shown. From the construction gf the apparatus the current is 
permitted to move in a complete metallic circuit of great length 
during the first instants of its formation : it gradually rises in 
strength, and, is / then suddenly stopped by the breaking of the 
metallic circuit ; and thus great intensity is given by induction 
to the electricity, which at that moment passes (1001. 1060.). 
This intensity is not only shown by the brilliancy of * the spark 
and the strength of the shock, but also by the necessity which 
has been experienced of well insulating the convolutions of the 
helix, in which the current is formed ; and it gives to the cur- 
rent a force at these moments very far above that which the 
apparatus could produce if the principle which forms the sub- 
ject of this paper were not called into play. 

Royal Institution, 

December %th } 1834. 



344 


TENTH SERIES. 

§ 16. On an improved form of the Voltaic Battery. § 17. Some 
practical results respecting the construction and pise of the 
Voltaic Battery. 

Received June 16, — Read June 18, 1835. 

1119. I have lately liad occasion to examine the voltaic trough 
practically, with a view to improvements in its construction and 
use ; and though I do not pretend /hat the results have any- 
thing like the importance which attaches to the discovery of a 
new law or principle, I still think they are valuable, and may 
therefore, if briefly told, and in connexion with former papers, 
be worthy the approbation of the Royal Society. 

§ 16. On an improved form of the Voltaic Battery . 

1120. In a simple voltaic circuit (and the same is true of the 
battery) the chemical forces which, during their activity, give 
power to the instrument, are generally divided into two portions ; 
one of these is exerted locally, whilst the other is transferred 
round the circle (947. 996.) ; the latter constitutes the electric 
current of the instrument, whilst the former is altogether lost 

.or wasted. The ratio of these two portions of power may be 
varied to a great extent by the influence of circumstances : thus, 
in a battery not closed, all the action is local ; in one of the 
ordinary construction, much is in circulation when the extremi- 
ties are in communication ; and in the perfect one, which I have 
described (1010), all the chemical power circulates and becomes 
electricity. By referring to the quantity of zino dissolved from 
the plates (865. 1126.), and the quantity of decomposition ef- 
fected in the volta-electrometer (711. 1126.) or elsewhere, the 
proportions of the local and transferred actions under any par- 
ticular circumstances can be ascertained, and the efficacy of the 
voltaic arrangement, or the waste of chemical power at its zinc 
plates, be accurately determined. 

1121. If a voltaic battery were constructed of zinc and pla- 



345 


Junk 1835.] Hare's voltaic battery. 

tina, the latter metal surrounding the former, as in the double 
copper arrangement, and the whole being excited by dilute sul- 
phuric acid, then no insulating divisions of glass, porcelain, or 
air would be required between the contiguous platina surfaces ; 
and, provided these did not touch metallically, the same acid 
which, being between the zinc and platina, would excite the 
battery into powerful action, would, between the two surfaces 
of platina* produce no discharge of the electricity, nor cause 
any diminution of the power of the trough. This is a necessary 
consequence of the resistance to the passage of the current 
which I have shown occurs at the place of decomposition (1007. 
1011.) ; for that resistance is fully able to stop the current, and 
therefore acts as insulation to the electricity of the contiguous 
plates, inasmuch as the •current which tends to pass between 
them never has a higher intensity than that due to the action 
of a single pair. 

1122. If the metal surrounding the zinc be copper (1015.) 
and if the acid be nitro-sulphurie acid (1020.), then a slight dis- 
charge between the two contiguous coppers does take place 
pi’ovided there be no other channel open by which the forces 
may circulate ; but when such a channel is permitted, the re- 
turn or back discharge of which I speak is exceedingly di- 
minished, in accordance with the principles laid down in the 
Eighth Series of these Researches . 

1123. Guided by these principles I was led to the construc- 
tion of a voltaic trough, in which the coppers, passing round 
both surfaces of the zincs, as in Wollaston’s construction, should 
not be separated from each other except by an intervening 
thickness of paper, or in some other way, so as to prevent me- 
tallic contact, and should thus constitute an instrument compact, 
powerful, economical, and easy of use. On examining, however, 
what had been done before, I found that the new trough was 
in all essential respects the same as that invented and described 
by Dr. Hare, Professor in the University of Pennsylvania, to 
whom I have great pleasure in referring it. 

1124. Dr. Hare has fully described his trough*. In it the 

* Philosophical Magazine, 1824, vol. lxiii. p. 241 ; or Silliman’s Journal, 
vol vii* See also a previous paper by Dr. Hare, Annals of Philosophy, 1821, 
voL i. p. 329, in which he Speaks of the non-necessity of insulation between 
the coppers. 



346 


New voltaic battery . 


[Series X. 


contiguous copper plates are separated by thin veneers of wood, 
and the acid is poured on to, or off, the plates by a quarter re- 
volution of an axis, to which both the trough containing the 
plates, and another trough to collect and hold the liquid, are 
fixed. This arrangement I have found the most convenient of 
any, and have therefore adopted it. My zinc plates were cut 
from rolled metal, and when soldered to the copper plates had 
the form delineated, fig. 1. These were then bent oiser a gauge 

Fig. 1. 

into the form fig. 2, and when packed in the wooden box con- 
structed to receive them, were arranged as in fig. 3*, little plugs 

Fig- 2. Fig. 3. 

ifn 

w 

of cork being used to keep the zinc plates from touching the 
copper plates, and a single or double thickness of cartridge 
paper being interposed between the contiguous surfaces of cop- 
per to prevent them from coming in contact. Such was the 
facility afforded by this arrangement, that a trough of forty 
pairs of plates could be unpacked in five minutes, and repacked 
again in half an hour ; and the whole series was not more than 
fifteen inches inolength. 

1125. This trough, of forty pairs of plates three inches square, 
was compared, as to the ignition of a platina wire, the discharge 
between points of charcoal, the shock on the human frame, &c., 
with forty pairs of four-inch plates having double coppers, and 
used in porcelain troughs divided into insulating cells, the 
strength of the acid employed to excite both being the same. 
In all these effects the former appeared quite equal to the latter. 

* The papers between the coppers are, for the sake of distinctness, unfitted 
in the figure. 





June 1835.] 


New voltaic battery. 


347 


On comparing a second trough of the new construction, con- 
taining twenty pairs of four-inch plates, with twenty pairs of 
four-inch plates in porcelain troughs, excited by acid of the 
same strength, the new titough appeared to surpass the old one 
in producing these effects, especially in the ignition of wire. 

1126. In these experiments the new trough diminished in its 
energy much more rapidly than the one on the old construction, 
and this tras a necessary consequence of the smaller quantity 
of acid used to excite it, which in the case of the forty pairs of 
new construction was only one-seventh part of that used for the 
forty pairs in the porcelain troughs. To compare, therefore, 
both forms of the voltaic trbugh in their decomposing powers, 
and to obtain accurate data as to their relative values, experi- 
ments of the following kind were made. The troughs were 
charged with a known quantity of acid of a known strength ; 
the electric current was passed through a volta-clcct rometer 
(711.) having electrodes 4 inches long and 2'3 inches in width, 
so as to oppose as little obstruction as possible to the current ; 
the gases evolved were collected and measured, and gave the 
quantity of water decomposed. Then the whole of the charge 
used was mixed together, and a known part of it analysed, by 
being precipitated and boiled with excess of carbonate of soda, 
and the precipitate well washed, dried, ignited, and weighed. 
In this way the quantity of metsfl oxidized and dissolved by the 
acid was ascertained ; and the part removed from eaeli zinc 
plate, or from all the plates, could be estimated and compared 
with the water decomposed in the volta-clect rometer. To bring 
these to one standard of comparison, 1 have reduced the results 
so as to express the loss at the plates in equivalents of zinc for 
the equivalent of water decomposed at the vqlta-elcctrometcr : 
I have taken the equivalent number of water as 9, and of zinc 
as 32*5, and have considered 100 cubic inches of the mixed 
oxygen and hydrogen, as they were collected over a pneumatic 
trough, to result from the decomjwsition of 12' 68 grains of 
water. 

1127* The acids used in these experiments were three, — 
sulphuric, nitric, and muriatic. The sulphuric acid was strong 
oil of vitriol ; one cubical inch of it was equivalent to 486 grains 
of marble. The nitric acid was very nearly pure ; one cubical 
inch dissolved 150 grains of marble. The muriatic acid was 



848 


New voltaic battery ; — its powers ; [Series X. 


also nearly pure, and one cubical inch dissolved 108 grains of 
marble. These were always mixed with water by volumes, the 
standard of volume being a cubical inch. 

1128. An acid was prepared cons^ting of 200 parts water, 
4^ parts sulphuric acid, and 4 parts nitric acid ; and with this 
both my trough containing forty pairs of three -inch plates, and 
four porcelain troughs, arranged in succession, each containing 
ten pairs of plates with double coppers four inches square, were 
charged. These two batteries were then used in succession, 
and the action of each was allowed to continue for twenty or 
thirty minutes, until the charge was nearly exhausted, the con- 
nexion with the volta-electrometer being carefully preserved 
during the whole time, and the acid in the troughs occasion- 
ally mixed together. In this way the* former trough acted so 
well, that for each equivalent of water decomposed in the volta- 
electrometer only from 2 to 2*5 equivalents of zinc were dissol- 
ved from each plate. In four experiments the average was 
2*21 equivalents for each plate, or 88*4 for the whole battery. 
In the experiments with the porcelain troughs, the equivalents 
of consumption at each plate were 3*54, or 141*6 for the whole 
battery. In a perfect voltaic battery of forty pairs of plates 
(991. 1001.) the consumption would have been one equivalent 
for each zinc plate, or forty for the whole. 

1129. Similar experiments were made with two voltaic bat- 
teries, one containing twenty pairs of four-inch plates, arranged 
as I have described (1124.), and the other twenty pairs of four- 
inch plates in porcelain troughs. The average of five experi- 
ments with the former was a consumption of 3*7 equivalents of 
zinc from each plate, or 74 from the whole; the average of 
three experiments with the latter was 5*5 equivalents from each 
plate, or 110 froifi the whole : to obtain this conclusion, two ex- 
periments were struck out, which were much against the porce- 
lain troughs, and in which some unknown deteriorating influ- 
ence was supposed to be accidentally active. In all the ex- 
periments, care was taken not to compare new and old plates 
together, as that would have introduced serious errors into the 
conclusions (1146.). 

1130. When ten pairs of the new arrangement were used, 
the consumption of zinc at each plate was 6*76 equivalents, or 
67 ' 6 for the whole. With ten pairs of the common construction. 



June 1835.] 


its advantages. 


349 


in & porcelain trough, the zinc oxidized was, upon an average, 
15*5 equivalents each plate, or 155 for the entire trough. 

1131. No doubt, therefore, can remain of the equality or even 
the great superiority of thus form of voltaic battery over the best 
previously in use, namely, that with double coppers, in which 
the cells are insulated. The insulation of the coppers may 
therefore be dispensed with ; and it is that circumstance which 
principally permits of such other alterations in the construction 
of the trough as gives it its practical advantages. 

1132. The advantages of this form of trough are very nu- 
merous and great, i. It is exceedingly compact, for 100 pairs 
-Of plates need not occupy a trough of more than three feet in 
length, ii. By Dr. Hare's plan of making the trough turn 
upon copper pivots which* rest upon copper bearings, the latter 
afford fixed terminations ; and these I have found it very con- 
venient to connect with two cups of mercury, fastened in the 
front of the stand of the instrument. These fixed terminations 
give the great advantage of arranging an apparatus to be used 
in connexion with the battery before the latter is put into 
action, iii. The trough is put into readiness for use in an in- 
stant, a single jug of dilute acid being sufficient for the charge 
of 100 pairs of four-inch plates, iv. On making the trough 
pass through a quarter of a revolution, it becomes active, and 
the great advantage is obtained of procuring for the experiment 
the effect of the first contact of the zinc and acid, which is 
twice or sometimes even thrice that which the battery can pro- 
duce a minute or two after (1036. 1150.). v. When the expe- 
riment is completed, the acid can be at once poured from be- 
tween the plates, so that the battery is never left to waste du- 
ring an unconnected state of its extremities ; the acid is not 
unnecessarily exhausted ; the zinc is not uselessly consumed ; 
and, besides avoiding these evils, the charge is mixed and ren- 
dered uniform, which produces a great and good result (1039.) ; 
and, upon proceeding to a second experiment, the important 
effect of first contact is again obtained, vi. The saving of zinc 
is very great. It is not merely that, whilst in action, the zinc 
performs more voltaic duty (1128. 1129.), but all the de- 
struction which takes place with the ordinary forms of battery 
between the experiments is prevented. This saving is of such 
extent, that I estimate the zinc in the new form of battery to 



350 


New voltaic battery. 


[Series X. 


be thrice as effective as that in the ordinary form. vii. The 
importance of this saving of metal is not merely that the value 
of the zinc is saved, but that the battery is much lighter and 
more manageable ; and also that the surfaces of the zinc and 
copper plates may be brought much nearer to each other when 
the battery is constructed, and remain so until it is worn out : 
the latter is a very important advantage (1148.). viii. Again, 
as, in consequence of the saving, thinner plates will perform 
the duty of thick ones, rolled zinc may be used ; and I have 
found rolled zinc superior to cast zinc in action ; a superiority 
which I incline to attribute to its greater purity (1144.). ix. 
Another advantage is obtained in the economy of the acic 1 
used, which is proportionate to the diminution of the zinc dis- 
solved. x. The acid also is more easily exhausted, and is in such 
small quantity that there is never any occasion to return an old 
charge into use. The acid of old charges whilst out of use, 
often dissolves portions of copper from the black flocculi usually 
mingled with it, which are derived from the zinc ; now any 
portion of copper in solution in the charge does great harm, 
because, by the local action of the acid and zinc, it tends to 
precipitate upon the latter, and diminish its voltaic efficacy 
(1145.). xi. By using a due mixture of nitric and sulphuric 
acid for the charge (1139.), no gas is evolved from the troughs ; 
so that a battery of several hundred pairs of plates may, with- 
out inconvenience, be close to the experimenter, xii. If, during 
a scries of experiments, the acid becomes exhausted, it can be 
withdrawn, and replaced by other acid with the utmost facility; 
and after the experiments arc concluded, the great advantage 
of easily washing the plates is at command. And it appears to 
me, that in place of making, under different circumstances, 
mutual sacrifice? of comfort, power, and economy, to obtain a 
desired end, all are at once obtained by Dr. Hare's form of 
trough. 

1133. But there are some disadvantages which I have not 
yet had time to overcome, though I trust they will finally be 
conquered. One is the extreme difficulty of making a wooden 
trough constantly water-tight under the alternations of wet and 
dry to which the voltaic instrument is subject. To remedy this 
evil, Mr. Newman is now engaged in obtaining porcelain 
troughs. The other disadvantage is a precipitation of copper 



351 


June 1835.] New voltaic battery. 

oi\ the zinc plates. It appears to me to depend mainly on the 
circumstance that the papers between the coppers retain acid 
when the trough is emptied ; and that this acid slowly acting 
on the copper, forms a salt, which gradually mingles with the 
next charge, and is reduced on the zinc plate by the local action 
(1120.) : the power of the whole battery is then reduced. I 
expect that by using slips of glass or wood to separate the cop- 
pers at th^ir edges, their contact can be sufficiently prevented, 
and the space between them be left so open that the acid of a 
charge can be poured and washed out, and so be removed from 
every, part of the trough when the experiments in which the 
dsrtfer is used are completed. 

1131. The actual superiority of the troughs which I have 
constructed on this plan, >1 believe to depend, first and princi- 
pally, on the closer approximation of the zinc and copper sur- 
faces ; — in my troughs they are only one-tenth of an inch apart 
(1148.) ; — and, next, on the superior quality of the rolled zinc 
above the cast zinc used in the construction of the ordinary 
2>ile. It cannot be that insulation between the contiguous cop- 
pers is a disadvantage, but I do not find that it is any advan- 
tage ; for when, with both the forty pairs of three-inch plates 
and the twenty pairs of four-inch plates, I used papers well 
soaked in wax*, these being so large that when folded at the 
edges they wrapped over each other, so as to make cells as in- 
sulating as those of the porcelain troughs, still no sensible ad- 
vantage in the chemical action was obtained. 

1135. As, upon principle, there must be a discharge of part 
of the electricity from the edges of the zinc and copper plates 
at the sides of the trough, I should prefer, and intend having, 
troughs constructed with a plate or plates of crown glass at the 
sides of the trough : the bottom will need none, though to 
glaze that and the ends would be no disadvantage. The plates 
need not be fastened in, but only set in their places ; nor need 
they be in large single pieces. 

§ 17. Some practical results respecting the construction and 
use of the Voltaic Battery (1034. See.). 

1136. The electro-chemical philosopher is well acquainted 

* A single paper thus prepared could insulate the electricity of a trough of 
forty pairs of plates. 



352 Battery acid ; — its nature. [Series X. 

with some practical results obtained from the voltaic battery by 
MM. Gay-Lussac and Thenard, and given in the first forty-five 
pages of their ‘ Recherches Physico-Chimiques\ Although 
the following results are generally of the same nature, yet the 
advancement made in this branch of science of late years, the 
knowledge of the definite action of electricity, and the more ac- 
curate and philosophical mode of estimating the results by the 
equivalents of zinc consumed, will be their sufficient justifi- 
cation. 

1137. Nature and strength of the acid . — My battery of forty 
pairs of three-inch plates was charged with acid consisting of 200 
parts water and 9 oil of vitriol. Each plate lost, in the average 
of the experiments, 4*66 equivalents of zinc for the equivalent 
of water decomposed in the volt a- electrometer, or the whole 
battery 186*4 equivalents of zinc. Being charged with a, 
mixture of 200 water and 16 of the muriatic acid, each plate 
lost 3*8, equivalents of zinc for the water decomposed, or the 
whole battery 152 equivalents of zinc. Being charged with a 
mixture of 200 water and 8 nitric acid, each plate lost 1*85, 
equivalents of zinc for one equivalent of water decomposed, or 
the whole battery 74*16 equivalents of zinc. The sulphuric 
and muriatic acids evolved much hydrogen at the plates in the 
trough ; the nitric acid no gas whatever. The relative strengths 
of the original acids have already been given (1127.) ; but a dif- 
ference in that respect makes no important difference in the 
results when thus expressed by equivalents (1140.). 

1138. Thus nitric acid proves to be the best for this purpose ; 
its superiority appears to depend upon its favouring the electro- 
lyzation of the liquid in the cells of the trough upon the prin- 
ciples already explained (905. 973. 1022.), and consequently 
favouring the transmission of the electricity, and therefore the 
production of transferable power (1120.). 

1139. The addition of nitric acid might, consequently, be ex- 
pected to improve sulphuric and muriatic acids. Accordingly, 
when the same trough was charged with a mixture of 200 water, 
9 oil of vitriol, and 4 nitric acid, the consumption of zinc was 
at each plate 2*786, and for the whole battery 111*5, equiva- 
lents. When the charge was 200 water, 9 oil of vitriol, and 
8 nitric acid, the loss per plate was 2*26, or for the whole bat- 
tery 90*4, equivalents. When the trough was charged with a 



353 


June 1835.} Strength of the battery acid. 

mixture of 200 water, 16 muriatic acid, and 6 nitric acid, the 
loss per plate was 2*11, or for the whole battery 81*4, equiva- 
lents. Similar results were obtained with my battery of twenty 
pairs of four-inch plates (1129.). Hence it is evident that the 
nitric acid was of great service when mingled with the sulphuric 
acid ; and the charge generally used after this time for ordinary 
experiments consisted of 200 water, 4 J oil of vitriol, and 4 nitric 
acid. 

1140. It is not to be supposed that the different strengths of 
the acids produced the differences above; for within certain 
limii^ I found the electrolytic effects to be nearly as the strengths 

tlie acids, so as to leave the expression of force, when given 
in equivalents, almost constant. Thus^ when the trough was 
charged with a mixture of 200 water and 8 nitric acid, each 
plate lost 1*854 equivalent of zinc. When the charge was 200 
water and 16 nitric acid, the loss per plate was 1*82 equivalent. 
When it was 200 water and 32 nitric acid, the loss was 21 
equivalents. The differences here arc not greater than happen 
from unavoidable irregularities, depending on other causes than 
the strength of acid. 

1141. Again, when a charge consisting of 200 water, 1 b oil 
of vitriol, and 4 nitric acid was used, each zinc plate lost 2*16 
equivalents ; when the charge with the same battery was 200 
water, 9 oil of vitriol, and 8 nitric acid, each zinc plate lost 2' 26 
equivalents. 

1142. I need hardly say that no copper is dissolved during 
the regular action of the voltaic trough. I have found that 
much ammonia is formed in the cells when nitric acid, either 
pure or mixed 'with sulphuric acid is used. It is produced iri 
part as a secondary result at the cathodes (663.) of the' different 
portions of fluid constituting the necessary electrolyte, in the 
cells, 

1143. Uniformity of the charge . — This is a most important 
point, as I have already shown experimentally (1042. &c.). 
Hence one great advantage of Dr. Hare's mechanical arrange- 
ment of his trough. 

1144. Purity of the zinc . — If pure zinc could be obtained, it 
would be very advantageous in the construction of the voltaic 
apparatus (998.) . Most zincs, when put into dilute sulphuric 
acid, leave more or less of an insoluble matter upon the sur- 

2a 



354 Practical results with the voltaic battery . [Series X. 

face in the form of a crust, which contains various metals* as 
copper, lead, zinc, iron, cadmium, &c., in the metallic state. 
Such particles, by discharging part of the transferable power, 
render it, as to the whole battery, local ; and so diminish the 
effect. As an indication connected with the more or less per- 
fect action of the battery, I may mention that no gas ought to 
rise from the zinc plates. The more gas which is generated 
upon these surfaces, the greater is the local action acid the less 
the transferable force. The investing crust is also inconvenient, 
by preventing the displacement and renewal of the charge upon 
the surface of the zinc. Such zinc as, dissolving in the' clean- 
est manner in a dilute acid, dissolves also the slowest, is tlT& 
best ; zinc which contains much copper should especially bo 
avoided. I have generally found rolled Liege or Mosselmaids 
zinc the purest ; and to the circumstance of having used such 
zinc in its construction attribute in part the advantage of the 
new battery (1134.). 

1145. Foulness of the zinc plates , — After use, the plates of a 
battery should be cleaned from the metallic powder upon their 
surfaces, especially if they are employed to obtain the laws of 
action of the battery itself. This precaution was always at- 
tended to with the porcelain trough batteries in the experiments 
described (1125,, &c.). If a few foul plates are mingled with 
many clean ones, they make the action in the different cells ir- 
regular, and the transferable power is accordingly diminished, 
whilst the local and wasted power is increased. No old charge 
containing copper should be used to excite a battery. 

114G. New and old plates . — I have found voltaic batteries far 
more powerful when the plates were new than when they have 
been used two or three times ; so that a new and an used battery 
cannot be compared together, or even a battery with itself on the 
first and after times of use. My trough of twenty pairs of four- 
inch plates, charged with acid consisting of 200 water, 4^ oil of 
vitriol, and 4 nitric acid, lost, upon the first time of being used, 
2*32 equivalents per plate. When used after the fourth time with 
the same charge, the loss was from 3*26 to 4*47 equivalents per 
plate ; the average being 3*7 equivalents. The first time the 
forty pair of plates (1124.) were used, the loss at each plate w as 
only 1*65 equivalent; but afterwards it beeamfe2T6, 2*17, 2*52. 
The first time twenty pair of four-inch plates in porcelain troughs 



355 


June 1835.] Vicinity of the copper and zinc. 

were used, they lost, per plate, ouly 3*7 equivalents ; but after 
that, the loss was 5*25, 5*36, 5*9 equivalents. Yet in all these 
cases the zincs had been well cleaned from adhering copper, &c., 
before each trial of pow r e*. 

1147. With the rolled zinc the fall in force soon appeared to 
become constant, i. e. to proceed no further. But with the cast 
zinc plates belonging to the porcelain troughs, it appeared to 
continue, tmtil at last, with the same charge, each plate lost 
above twice as much zinc for a given amount of action us at first. 
These troughs were, however, so irregular that I could not 
always determine the circumstances affecting the amount of 
electrolytic action. 

1148. Vicinity of the copper and zinc . — The importance of 
this point in the construction of voltaic arrangements, and the 
greater power, as to immediate action, which is obtained when 
the zinc and copper surfaces are near to each other than when 
removed further apart, are well known. 1 find that the power 
is not only greater on the instant, but also that the sum of 
transferable pow er, in relation to the whole sum of chemical 
action at the plates, is much increased. The cause of this gain 
is very evident. Whatever tends to retard the circulation of 
the transferable force, ( i . e. the electricity,) diminishes the pro- 
portion of such force, and increases the proportion of that which 
is local (996. 1120.). Now the Ifquid in the cells possesses this 
retarding power, and therefore acts injuriously, in greater or 
less proportion, acceding to the quantity of it between the zinc 
and copper plates, i. e. according to the distances between their 
surfaces. A trough, therefore, in which the plates arc only 
half the distance asunder at which they are placed in another, 
w ill produce more transferable, and less local, force than the 
latter ; and thus, because the electrolyte in the cells can trans- 
mit the current more readily, both the intensity and quantity 
of electricity is increased for a given consumption of zinc. To 
this circumstance mainly I attribute the superiority of the trough 
I have described (1134.). 

1149. The superiority of double coppers over single plates 
also depends in part upon diminishing the resistance offered by 
the electrolyte between the metals. For, in fact, with double 
copperfc the sectional area of the interposed acid becomes nearly 
double that with single coppers, and therefore it more freely 

2 a 2 



356 Practical results with the voltaic battery . [Series X. 

transfers the electricity. Double coppers are, however, effective, 
mainly because they virtually double the acting surface of the 
zinc, or nearly so ; for in a trough with single copper plates 
and the usual construction of cells, tlmt surface of zinc which 
is not opposed to a copper surface is thrown almost entirely out 
of voltaic action, yet the acid continues to act upon it and the 
metal is dissolved, producing very little more than local effect 
(9 47. 996.) . But when by doubling the copper, thdt metal is 
opposed to the second surface of the zinc plate, then a great 
part of the action upon the latter is converted into' transferable 
force, and thus the power of the trough as to quantity of ^ec- 
tricity is highly exalted. 

1 1 50. First immersion of the plates r. — The great effect pro- 
duced at the first immersion of the plates, (apart from their 
being new or used (1146.),) I have attributed elsewhere to the 
unchanged condition of the acid in contact with the zinc plate 
(1003. 1037.) : as the acid becomes neutralized, its exciting 
j)Ower is proportionality diminished. Hare's form of trough 
secures much advantage of this kind, by mingling the liquid, 
and bringing what may be considered as a fresh surface of acid 
against the plates every time it is used immediately after a rest. 

1151. Number of plates*. — The most advantageous number 
of plates in a battery used for chemical decomposition, depends 
almost entirely upon the resistance to be overcome at the place 
of action ; but whatever that resistance may be, there is a cer- 
tain number which is more economical than either a greater or 
a less. Ten pairs of four-inch plates in a porcelain trough of 
the ordinary construction, acting in the volta-electrometer 
(1126.) upon dilute sulphuric acid of spec. grav. 1*314, gave an 
average consumption of 15*4 equivalents per plate, or 154 equi- 
valents on the whole. Twenty pairs of the same plates, with 
the same acid, gave only a consumption of 5*5 per plate, or 110 
equivalents upon the whole. When forty pairs of the same 
plates were used, the consumption was 3*54 equivalents per 
plate, or 141*6 upon the whole battery. Thus the consump- 
tion of zinc arranged as twenty plates was more advantageous 
than if arranged either as ten or as forty. 

.1152. Again, ten pairs of my four-inch plates (1129.) lost 
6*76 each, or the whole ten 67*6 equivalents of zinc, in effect- 

* Gay-Lussac and Tlidnard, Itecherclies PhyBico-Chirniques, tom. 1. p* 29. 



357 


June 1835.] Number and size of the plates . 

ing decomposition ; whilst twenty pairs of the same plates, ex- 
cited by the same acid, lost 3*7 equivalents each, or on the 
whole 74 equivalents. In other comparative experiments of 
numbers, ten pairs of tli^ three- inch plates (1125.), lost 3*723, 
or 37'25 equivalents upon the whole; whilst twenty pairs lost 
2 ' 53 each, or 506 in all ; and fovty pairs lost on an average 
2*21, or 88*1 altogether. In both those cases, therefore, in- 
crease of numbers had not been advantageous as to the effec- 
tive production of transferable chemical power from the whole 
quantity of chemical force active at the surfaces of excitation 
(11 23.) . 

1153. But if I had used a weaker acid or a worse conductor 
in the volta-electrometer, then the number of plates which would 
produce the most ad van fageous effect would have risen; or if 
I had used a better conductor than that really employed in the 
volta-clectrometcr, X might have reduced the number even to 
one ; as, for instance, when a thick wire is used to complete the 
circuit (865. &c,). And the cause of these variations is very 
evident, when it is considered that each sueeessi\e plate in the 
voltaic apparatus does not add anything to the quantity of trans- 
ferable power or electricity which the first plate can put into 
motion, provided a good conductor be present, but tends only 
to exalt the intensity of that quantity, so as to make it more 
able to overcome the obstructioiuof bad conductors (1)1) k 1158). 

1154. Large or small plates — The advantageous use of 
large or small plates for electrolyzations will evidently depend 
upon the facility with which the transferable power or electri- 
city can pass. If in a particular case the most effectual number 
of plates is known (1151.), then the addition of more zinc would 
be most advantageously made in increasing the size of the plates, 
and not their number. At the same time, largo increase in the 
size of the plates would raise in a small degree the most favour- 
able number. 

1155. Large and small plates should not be used together in 
the same battery : the small ones occasion a loss of the power 
of the large ones, unless they be excited by an acid proportion- 
ably more powerful ; for with a certain acid they cannot transmit 
the same portion of electricity in a given time which the sam 
acid can evolve by action on the larger plates. 

* Gay-Lussac and Th^nard, Recherches Physico-Chimiquea, tom, i. p. 29. 



358 


. Practical results with the battery. [Series X. 

1156. Simultaneous decompositions . — When the number -of 
plates in a battery much surpasses the most favourable pro- 
portion (1151 — 1153.), two or more decompositions may be 
effected simultaneously with advantage* Thus my forty pairs of 
plates (1121.) produced in one volta-electrometer 22*8 cubic 
inches of gas. Being recharged exactly in the same manner, 
they produced in each of two volta-eleetromcters 21 cubical 
inches. In the first experiment the whole consumption of zinc 
was 88*4 equivalents, and in the second only 48*28 equivalents, 
for the whole of the water decomposed in both volta- electro- 
meters. 

1157. But when the twenty pairs of four-inch plates (1129.) 
were tried in a similar manner, the results were in the opposite 
direction. With one volta-electrometer 52 cubic inches of gas 
were obtained ; with two, only 14*6 cubic inches from each. 
The quantity of charge was not the same in both cases, though 
it was of the same strength ; but on rendering the results com- 
parative by reducing them to equivalents (1126.), it was found 
that the consumption of metal in the first case was 74, and in 
the second case 97, equivalents for the whole of the water de- 
composed. These results of course depend upon the same 
circumstances of retardation, &c., which have been referred to 
in speaking of the proper number of plates (1151.). 

1158. That the transferring , or, as it is usually called, con- 
ducting , power of an electrolyte which is to be decomposed, or 
other interposed body, should be rendered as good as pos- 
sible *, is very evident (1020. 1120.). With a perfectly good 
conductor and a good battery, nearly all the electricity is passed, 
i. e. nearly all the chemical power becomes transferable, even 
with a single pair of plates (867.). With an interposed non- 
conductor, none* of the chemical power becomes transferable. 
With an imperfect conductor more or less of the chemical 
power becomes transferable as the circumstances favouring the 
transfer of forces across the imperfect conductor are exalted or 
diminished : these circumstances arc, actual increase or im- 
provement of the conducting power, enlargement of the elec- 
trodes, approximation of the electrodes, and increasedf intensity 
of the passing current. 

* Gay-Lussac and Thdnard, Recherches Physico-Cbimiques, tom. i. pp. 13> 
15, 22. 



351) 


June 1835.] Conducting power of the fluid. 

J159. The introduction of common spring water in place of 
one of the volt a- electrometers used with twenty pairs of four- 
inch plates (1150.) caused such obstruction as not to allow one 
fifteenth of the transferable force to pass which would have 
circulated without it. Thus fourteen fifteenths of the available 
force of the battery were destroyed, being converted into local 
force, (which was rendered evident by the evolution of gas from 
the zincs,^ and yet the platina electrodes in the water were 
three inches long, nearly an inch wide, and not a quarter of an 
inch apart. 

1160. These points, i. e. the increase of conducting power, 
the enlargement of the electrodes, and their approximation, 
should be especially attended to in volta-eleelromcters. The 
principles upon which their utility depend are so evident that 
there can be no occasion for further development of them 
here. 

Royal Institution , 

October 11 th, 1831. 



360 


ELEVENTH SEMES.' 

§ 18. On Induction. If i. Induction an action of contiguous 
particles. ii. Absolute charge of matter, iii. Electro- 
meter and inductive apparatus employed. If iv. Induction in 
curved lines. 1 v. Specific inductive capacity. If vi. General 
results as to induction . 

Received November 30, — Read December 21, 1837. 

T i. Induction an action of contiguous particles. 

1101. The science of electricity is in that state in which every 
part of it requires experimental investigation ; not merely for 
the discovery of new effects, but what is just now of far more 
importance, the development of the means by which the old 
effects arc produced, and the consequent more accurate deter- 
mination of the first principles of action of the most extraordi- 
nary and universal power in nature : — and to those philosophers 
who pursue the inquiry zealously yet cautiously, combining ex- 
periment with analogy, suspicious of their preconceived notions, 
paying more respect to a fact £han a theory, not too hasty to 
generalize, and above all things, willing at every step to cross- 
examine their own opinions, both by reasoning and experiment, 
no branch of knowledge can afford so fine and ready a field for 
discovery as this. Such is most abundantly shown to be the 
case by the progress which electricity has made an the last 
thirty years : Chemistry and Magnetism have successively ac- 
knowledged its over -ruling influence ; and it is probable that 
every effect depending upon the powers of inorganic matter, 
and perhaps most of those related to vegetable and animal life, 
will ultimately be found subordinate to it. 

1162. Amongst the actions of different kinds into which elec- 
tricity has conventionally been subdivided, there is, I think, 
none which excels, or even equals in importance that called 
Induction. It is of the most general influence in electrical phe- 
nomena, appearing to be concerned in every one of them, and 
has in Reality the character of a first, essential, and fundamental 



361 


Not. 1837.] Nature of electrical induction. 

principle. Its comprehension is so important, that I think we 
cannot proceed much further in the investigation of the laws of 
electricity without a more thorough understanding of its na- 
ture ; how otherwise can^we hope to comprehend the harmony 
and even unity of action which doubtless governs electrical ex- 
citement by friction, by chemical means, by heat, by magnetic 
influence, by evaporation, and even by the living being ? 

1163. Li the long-continued course of experimental inquiry 
in which I have been engaged, this general result lias pressed 
upon me constantly, namely, the necessity of admitting two 
forces, or two forms or directions of a force (516. 5 17.)/ com- 
bined with the impossibility of separating these two forces (or 
electricities) from each other, either in the phenomena of sta- 
tical electricity or thosi? of the current. In association with 
this, the impossibility under any circumstances, as yet, of ab- 
solutely charging matter of any kind with one or the other elec- 
tricity only, dwelt on my mind, and made me wish and search 
for a clearer view than any that 1 was acquainted with, of the 
way iu which electrical powers and the particles of matter are 
related; especially in inductive actions, upon which almost all 
others appeared to rest. 

1161*. When 1 discovered the general fact that electrolytes 
refused to yield their elements to a current when in the solid 
state, though they gave them forth freely if in the liquid con- 
dition (380. 391. 402.), I thought I saw an opening to the elu- 
cidation of inducthe action, and the possible subjugation of 
many dissimilar phenomena to one law. For let the electrolyte 
be water, a plate of ice being coated with platina foil on its two 
surfaces, and these coatings connected with any continued 
source of the two electrical powers, the ice wall charge like a 
Leyden arrangement, presenting a ease of common induction, 
but no current will pass. If the ice be liquefied, the induction 
will fall to a certain degree, because a current can now pass ; 
but its parsing is dependent upon a peculiar molecular arrange- 
ment of the particles consistent with the transfer of the elements 
of the electrolyte in opposite directions, the degree of discharge 
and the quantity of elements evolved being exactly proportioned 
to each other (377. 783.). Whether the charging of the me- 
tallic coating be effected by a powerful electrical machine, a 
strong and large voltaic battery, or a single pair of plates, makes 



362 


On static electrical induction , [Series XI* 

no difference in the principle, but only in the degree of action 
(360.). Common induction takes place in each fcasc if the elec- 
trolyte be solid, or if fluid, chemical action and decomposition 
ensue, provided opposing actions do npt interfere ; and it is of 
high importance occasionally thus to compare effects in their 
extreme degrees, for the purpose of enabling us to comprehend 
the nature of an action in its weak state, which may be only 
sufficiently evident to us in its stronger condition (V51.). As, 
therefore, in the electrolytic action, induction appeared to be the 
first step, and decomposition the second (the power of separa- 
ting these steps from each other by giving the solid or fluid con- 
dition to the electrolyte being in our hands) ; as the induction 
was the same in its nature as that through air, glass, wax, &e. 
produced by any of the ordinary rncaiis ; and as the whole ef- 
fect in the electrolyte appeared to be an action of the particles 
thrown into a peculiar or polarized state, I was led to suspect 
that common induction itself was in all cases an action of con- 
tiguous particles*, and that electrical action at a distance ( i . e. 
ordinary inductive action) never occurred except through the 
influence of the intervening matter. 

1165. The respect which I entertain towards the names of 
Epinus, Cavendish, Poisson, and other most eminent men, all 
of whose theories I believe consider induction as an action at a 
distance and in straight lines, long indisposed me to the view I 
have just stated ; and though I always watched for oppor- 
tunities to prove the opposite opinion, and made such experi- 
ments occasionally as seemed to bear directly on the point, as, 
for instance, the examination of electrolytes, solid and fluid, 
whilst under induction by polarized light (951. 955.), it is only 
of late, aifd by degrees, that the extreme generality of the sub- 
ject has urged nffe still further to extend my experiments and 
publish my view. At present I believe ordinary induction in 
all cases to be an action of contiguous particles consisting in a 
species of polarity, instead of being an action of either particles 
or masses at sensible distances ; and if this be true, the di- 

* The word contiguous is perhaps not the best that might have been used 
here and elsewhere ; for as particles do not touch each other it is not strictly 
correct. I was induced to employ it, because in its common acceptation it 
enabled me to state the theory plainly and with facility. By contiguous par- 
ticles I mean those which are next. — Dec . 1838. 



Nov. 1837.] Induction an action of contiguous particles . 363 

stinction and establishment of such a truth must be of the 
greatest consequence to our further progress in the investiga- 
tion of the nature of electric forces. The linked condition of 
electrical induction with chemical decomposition; of voltaic ex- 
citement with chemical action ; the transfer of elements in an 
electrolyte ; the original cause of excitement in all cases ; the 
nature and relation of conduction and insulation ; of the direct 
and lateral or transverse action constituting electricity and 
magnetism; with many other things more or less incomprehen- 
sible at present, would all be affected by it, and perhaps re- 
ceive a full explication in their reduction under one general 
law. 

1166. I searched for an unexceptionable test of my view, 
not merely in the accordance of known facts with it, but in the 
consequences which would flow from it if true ; especially in 
those which would not be consistent with the theory of action 
at a distance. Such a consequence seemed to me to present 
itself in the direction in w hich inductive action could he exerted. 
If in straight lines only, though not perhaps decisive, it would 
he against my view ; but if in curved lines also, that would be 
a natural result of the action of contiguous particles, but, as T 
think, utterly incompatible with action at a distance, as as- 
sumed by the received theories, which, according to every fact 
and analogy we arc acquainted with, is always in straight lines. 

1167. Again, if induction be an action of contiguous parti- 
cles, and also the first step in the process of electrolyzation 
(1164. 949.), there seemed reason to expect some particular 
relation of it to the different kinds of matter through wdiich it 
would be exerted, or something equivalent to a specific electric 
induction for different bodies, which, if it existed, * .rould un- 
equivocally prove the dependence of induction' on the particles ; 
and though this, in the theory of Poisson and others, has 
never been supposed to be the case, I was soon led to doubt 
the received opinion, and have taken great pains in subjecting 
this point to close experimental examination. 

1168. Another ever-present question on ray mind has been, 
whether electricity has an actual and independent existence as 
a fluid or fluids, or was a mere power of matter, like what we 
conceive of the attraction of gravitation. If determined either 
way it, would be an enormous advance in our knowledge; and as 



364 Absolute charge of matter. [Series XI, 

having the most direct and influential bearing on my notion^, I 
have always sought for experiments which would in any way 
tend to elucidate that great inquiry. It was in attempts to 
prove the existence of electricity separate from matter, by 
giving an independent charge of either positive or negative 
power only, to some one substance, and the utter failure of all 
such attempts, whatever substance was used or whatever means 
of exciting or evolving electricity were employed^ that first 
drove me to look upon induction as an action of the particles 
of matter, each having both forces developed in it in exactly 
equal amount. It is this circumstance, in connection with 
others, which makes me desirous of placing the remarks on 
absolute charge first, in the order of proof and argument, which 
I am about to adduce in favour of my view, that electric in- 
duction an action of the contiguous particles of the insulating 
medium or dielectric * . 

*f| ii. On the absolute charge of matter . 

1169. Can matter, either conducting or non-conducting, be 
charged with one electric force independently of the other, in 
any degree, either in a sensible or latent state ? 

1170. The beautiful experiments of Coulomb upon the 
equality of action of conductors, whatever their substance, and 
the residence of all the electricity upon their surfaces f, are 
sufficient, if properly viewed, to prove that conductors cannot 
be bodily charged ; and as yet no means of communicating elec- 
tricity to a conductor so as to place its particles in relation to 
one electricity, and not at the same time to the other in exactly 
equal amount, has been discovered. 

1171. JVith regard to electrics or non-conductors, the con- 
clusion does nok at first seem so clear. They may easily be 
electrified bodily, either by communication (1247.) or excite- 
ment ; but being so charged, every case in succession, when 
examined, came out to be a case of induction, and not of abso- 
lute charge. Thus, glass within conductors could easily have 
parts not in contact with the conductor brought into an excited 
state ; but it was always found that a portion of the inner sur- 

* I use the word dielectric to express that substance through or across 
which the electric forces are acting. — Dec . 1838. 

t M^moires de 1’ Academic, 1786, pp. 67. 69. 72 ; 1787, p. 452* 



365 


Nov. 1837.] Charge of oil of turpentine and air. 

face of the conductor was in an opposite and equivalent state, 
or that another part of the glass itself was in an equally oppo- 
site state, an inductive charge and not an absolute charge 
having been acquired. 

1172. Well-purified oil of turpentine, which I find to be an 
excellent liquid insulator for most purposes, was put into a me- 
tallic vessel, and, being insulated, an endeavour was made to 
charge its particles, sometimes by contact of the metal with the 
electrical machine, and at others by a wire dipping into the 
fluid within ; but whatever the mode of communication, no 
electricity of one kind only was retained by the arrangement, 
except what appeared on the exterior surface of the metal, that 
portion being present there only by an inductive action through 
the air to the surrounding conductors. When the oil of turpen- 
tine was confined in glass vessels, there were at first some ap- 
pearances as if the fluid did receive an absolute charge of elec- 
tricity from the charging wire, but those were quickly reduced to 
cases of common induction jointly through the fluid, the glass, 
and the surrounding air. 

1173. I carried these experiments on w'ith air to a very 
groat extent. I had a chamber built, being a cube of twelve 
feet. A slight cubical wooden frame was constructed, and 
copper wire passed along and across it in various directions, so 
as to make the sides a large net-work, and then all was covered 
in with paper, placed in close connexion w ith the wires, and 
supplied in every direction with bands of tin foil, that the whole 
might be brought into good metallic communication, and ren- 
dered a free conductor in every part. This chamber was in- 
sulated in the lecture-room of the Royal Institution ; a glass 
tube about six feet in length was passed through its side, 
leaving about four feet within and two feet oiv the outside, and 
through this a wire passed from the large electrical machine 
(290.) to the air within. By working the machine, the air in 
this chamber could be brought into what is considered a highly 
electrified state (being, in fact, the same state as that of the air 
of a room in which a powerful machine is in operation), and at 
the same time the outside of the insulated cube was everywhere 
strongly charged. But putting the chamber in communication 
with the perfect discharging train described in a former series 
(292.), and working the machine so as to bring the air within 



366 Absolute charge of matter . [Sekies XI. 

to its utmost degree of charge if I quickly cut off the connexion 
with the machine, and at the same moment or instantly after 
insulated the cube, the air within had not the least power to 
communicate a further charge to it. If any portion of the air 
was electrified, as glass or other insulators may be charged 
(1171.), it was accompanied by a corresponding opposite action 
within the cube, the whole effect being merely a case of induc- 
tion. Every attempt to charge air bodily and independently 
with the least portion of cither electricity failed. 

1174. 1 put a delicate gold-leaf electrometer within the cube, 
and then charged the whole by an outside communication, very 
strongly, for some time together; but neither during the charge 
or after the discharge did the electrometer or air within show 
the least signs of electricity. I charged and discharged the 
whole arrangement in various ways, but in no case could I obtain 
the least indication of an absolute charge; or of one by in- 
duction in which the electricity of one kind had the smallest 
superiority in quantity over the other. I went into the cube 
and lived in it, and using lighted candles, electrometers, and 
all other tests of electrical states, I could not find the least in- 
fluence upon them, or indication of anything particular given by 
them, though all the time the outside of the cube was power- 
fully charged, and large sparks and brushes were darting off 
from every part of its outer .surface. The conclusion I have 
come to is, that non-conductors, as well as conductors, have 
never yet had an absolute and independent charge of one elec- 
tricity communicated to them, and that to all appearance such 
a state of matter is impossible. 

1175. .There is another view of this question which maybe 
taken under th<? supposition of the existence of an electric 
fluid or fluids. It may be impossible to have one fluid or state 
in a free condition without its producing by induction the 
other, and yet possible to have cases in which an isolated portion 
of matter in one condition being uncharged, shall, by a change 
of state, evolve one electricity or the other : and though such 
evolved electricity might immediately induce the opposite state 
in its neighbourhood, yet the mere evolution of one electricity 
without the other in the first instance , would be a very import- 
ant fact in the theories which assume- a fluid or fluids; these 



Nov. 1837.] Charge is induction . 3G7 

theories as I understand them assigning not the slightest rea- 
son why such an effect should not occur. 

1176. But on searching for such cases I cannot find one. 
Evolution by friction, as is well known, gives both powers in 
equal proportion. So does evolution by chemical action, not- 
withstanding the great diversity of bodies which may be em- 
ployed, and the enormous quantity of electricity which can in 
this manner be evolved (371. 376. 861. 868. 9oi.). The more 
promising cases of change of state, whether by evaporation, 
fusion, or the reverse processes, still give both forms of the 
power in equal proportion ; and the cases of splitting of -mica 
and other crystals, the breaking of sulphur, &c., arc subject to 
the same laAv of limitation. 

1177. As far as experiment has proceeded, it appears, there- 
fore, impossible cither to evolve or make dh appear one electric 
force without equal and corresponding change in the other. It 
is also equally impossible experimentally to charge a portion 
of matter with one electric force independently of the other. 
Charge always implies induction, for it can in no instance be 
effected without ; and also the presence of the two forms of 
power, equally at the moment of the development and after- 
wards. There is no absolute charge of matter with one fluid ; 
no latency of a single electricity. This though a negative re- 
sult is an exceedingly important pne, being probably the con- 
sequence of a natural impossibility, which will become clear to 
us when w r c understand the true condition and theory of the 
electric power. 

1178. The preceding considerations already point to the fol- 
lowing conclusions : bodies cannot be charged absolutely, but 
only relatively, and by a principle which is the same with that 
of induction. All charge is sustained by induction. All phe- 
nomena of intensity include the principle of induction. All ex- 
citation is dependent on or directly related to induction. All 
currents involve previous intensity and therefore previous in- 
duction. Induction appears to be the essential function both 
in the first development and the consequent phenomena of 
electricity; 

If iiL Electrometer and inductive apparatus employed. 

1179. Leaving for a time the further consideration of the 



368 Coulomb’s electrometer. [Series XI. 

preceding facts until they can be collated with other results 
bearing directly on the great question of the nature of induc- 
tion, I will now describe the apparatus I have had occasion to 
use ; and in proportion to the importance of the principles 
sought to be established is the necessity of doing this so clearly, 
as to leave no doubt of the results behind. 

1180. Electrometer . The measuring instrument I have em- 
ployed has been the torsion balance electrometer of,. Coulomb, 
constructed, generally, according to his directions*, but with 
certain variations and additions, which I will briefly describe. 
The lower part was a glass cylinder eight inches in height and 
eight inches in diameter ; the tube for the torsion thread was 
seventeen inches in length. The torsion thread itself was not 
of metal, but glass, according to the excellent suggestion of the 
late Dr. Ritchie +. It was twenty inches in length, and of such 
tenuity that when the shell-lac lever and attached ball, &c. 
were connected with it, they made about ten vibrations in a 
minute. It would bear torsion through four revolutions or 
1440°, and yet, when released, return accurately to its position ; 
probably it would have borne considerably more than this with- 
out injury. The repelled ball was of pith, gilt, and was 03 of 
an inch in diameter. The horizontal stem or lever supporting 
it was of shell-lac, according to Coulomb's direction, the arm 
carrying the ball being 2*4 inches long, and the other only 1*2 
inches : to this was attached the vane, also described by Cou- 
lomb, which I found to answer admirably its purpose of quickly 
destroying vibrations. That the inductive action within the 
electrometer might be uniform in all positions of the repelled 
ball and in all states of the apparatus, two bands of tin foil, 
about an inch wide each, were attached to the inner surface of 
the glass cylinder, going entirely round it, at the distance of 
0*4 of an inch from each other, and at such a height that the 
intermediate clear surface was in the same horizontal plane with 
the lever and ball. These bands were connected with each 
other and with the earth, and, being perfect conductors, always 
exerted a uniform influence on the electrified balls within, which 
the glass surface, from its irregularity of condition at different 
times, I found, did not. For the purpose of keeping “the air 

* Mdmoires dc TAcad&nie, 1785, p. 670. 

f Philosophical Transactions, 1830. 



Coulomb’s electrometer . 


369 


Nov. 1837.] 

within the electrometer in a constant state as to dryness, a glass 
dish, of such size as to enter easily within the cylinder, had a 
layer of fused potash placed within it, and this being covered 
with a disc of fine wire-gauze to render its inductive action uni- 
form at all parts, was placed* within the instrument at the bottom 
and left there. 

1181. The moveable ball used to take and measure the por- 
tion of electricity under examination, and which may be called 
the repelling , or the carrier, ball, was of soft alder wood, well 
and smoothly gilt. It was attached to a fine shell -lac stem, and 
introduced through a hole into the electrometer according to 
Coulomb's method : the stem was fixed at its upper end in a 
block or vice, supported on three short feet; and on the surface 
of the glass cover above wxs a plate of lead with stops on it, 
so that when the carrier ball was adjusted in its right posi- 
tion, with the vice above bearing at the same time against these 
stops, it was perfectly easy to bring away the carrier-ball and 
restore it to its place again very accurately, without any loss of 
time, 

1182. It is quite necessary to attend to certain precautions 
respecting these balls. If of pith alone they are bad ; for when 
very dry, that substance is so imperfect a conductor that it 
neither receives nor gives a charge freely, and so, after contact 
with a charged conductor, it is liable to be in an uncertain con- 
dition. Again, it is difficult to turn pith so smooth as to lea\e 
the ball, even when gilt, so free from irregularities of form, 
as to retain its charge undiminished for a considerablejongth 
of time. When, therefore, the balls are finally prepared atul 
gilt they should' be examined ; and being electrified, unless 
they can hold their charge with very little diminution for a con- 
siderable time, and yet be discharged instantly and perfectly 
by the touch of an uninsulated conductor, they should be dis- 
missed, 

1183. It is, perhaps, unnecessary to refer to the graduation 
of the instrument, further than to explain how the observations 
were made. On a circle or ring of paper on the outside of the 
glass cylinder, fixed so as to cover the internal lower ring of 
tinfoil, were marked four points corresponding to angles of 
90° ; fotir other points exactly corresponding to these points 
being marked on the upper ring of tinfoil within. By these 

2 B 



370 


Coulomb’s electrometer . 


[Series XI. 


and the adjusting screws on which the whole instrument stands, 
the glass torsion thread could be brought accurately into the 
centre of the instrument and o£ the graduations on it. From 
one of the four points on the exterior of the cylinder a gradua- 
tion of 90° was set off, and a corresponding graduation was 
placed upon the upper tinfoil on the opposite side of the cy- 
linder within ; and a dot being marked on that point of the 
surface of the repelled ball nearest to the side of Jhe electro- 
meter, it was easy, by observing the line which this dot made 
with the lines of the two graduations just referred to, to ascer- 
tain accurately the position of the ball. The upper end of the 
glass thread was attached, as in Coulomb’s original electrometer, 
to an index, which had its appropriate graduated circle, upon 
which the degree of torsion was ultimately to be read off. 

1181. After the levelling of the instrument and adjustment 
of the glass thread, the blocks which determine the place of 
the carrier ball are to be regulated (1181.) so that when the 
carrier arrangement is placed against them, the centre of the 
ball may be in the radius of the instrument corresponding to 0° 
on the lower graduation or that on the side of the electrometer, 
and at the same level and distance from the centre as the repelled 
ball on the suspended torsion lever. Then the torsion index 
is to be turned until the ball connected with it (the repelled ball) 
is accurately at 30°, and finally the graduated arc belonging 
to the torsion index is to be adjusted so as to bring 0° upon it 
to the index. This state of the instrument was adopted as that 
which gave the most direct expression of the experimental re- 
sults, and in the form having fewest variable errors ; the angular 
distance of 30° being always retained as the standard distance 
to which the balls were in every case to be brought, and the 
whole of the torsion being read off at once on the graduated 
circle above. Under these circumstances the distance of the 
balls from each other was not merely the same in degree, but 
their position in the instrument, and in relation to every part of 
it, was actually the same every time that a measurement was 
made ; so that all irregularities arising from slight difference of 
form and action in the instrument and the bodies around were 
avoided. The only difference which could occur in the position 
of anything within, consisted in the deflection of the torsion 
thread from a vertical position, more or less, according to the 



Nov. 1837.] Inductive apparatus, 371 

force of repulsion of the balls ; but this was so slight as to cause 
no interfering difference in the symmetry of form within the in- 
strument, and gave no error in the amount of torsion force in- 
dicated on the graduation above. 

1185. Although the c<Snstant angular distance of 30° be- 
tween the centres of the balls was adopted, and found abun- 
dantly sensible, for all ordinary purposes, yet the facility of 
rendering the instrument far more sensible by diminishing this 
distance was at perfect command ; the results at different dis- 
tances being very easily compared with each other either by 
experiment, or, as they are inversely as the squares of the dis- 
tances, by calculation. 

1186. The Coulomb balance electrometer requires expe- 
rience to be understood ; .but I think it a very valuable instru- 
ment in the hands of those who will take pains by practice and 
attention to learn the precautions needful in its use. Its 
insulating condition varies with circumstances, and should be 
examined before it is employed in experiments. In an ordinary 
and fair condition, when the balls were so electrified as to give 
a repulsive torsion force of 400° at the standard distance of 30°, 
it took nearly four hours to sink to 50° at the same distance; 
the average loss from 400° to 300° being at the rate of 2°’ 7 per 
minute, from 300° to 200° of 1°*7 per minute, from 200° to 100° 
of 1°3 per minute, and from 100° to 50° of 0°*8 7 per minute. 
As a complete measurement by flic instrument may be made in 
much less than a minute, the amount of loss in that time is but 
small, and can easily be taken into account. 

1187. The inductive apparatus , — My object was to examine 
inductive action carefully when taking place through, different 
media, for which purpose it was necessary, to subject these 
media to it in exactly similar circumstances, and in such quanti- 
ties as should suffice to eliminate any variations they might pre- 
sent. The requisites of the apparatus to be constructed were, 
therefore, that the inducing surfaces of the conductors should 
have a constant form and state, and be at a constant distance from 
each other ; and that either solids, fluids, or gases might be 
placed and retained between these surfaces with readiness and 
certainty, and for any length of time. 

1188. The apparatus used may be described in general terms 

2 b 2 



372 Inductive apparatus described . [Sekies XI. 

as consisting of two metallic spheres of unequal diameter, 
placed, the smaller within the larger, and concentric with it; 
the interval between the two being the space through which 
the induction was to take place. A section of it is given (Plate 
VII. fig. 104.) on a scale of one ha\f : a, a are the two halves 
of a brass sphere, with an air-tight joint at b, like that of the 
Magdeburg hemispheres, made perfectly flush and smooth in- 
side so as to present no, irregularity ; c is a connecting piece 
by which the apparatus is joined to a good stop-cock d } which 
is itself attached either to the metallic foot e y or to an air pump. 
The aperture within the hemisphere at / is very small ; g is a 
brass collar fitted to the upper hemisphere, through which the 
shell-lac support of the inner ball and its stem passes ; h is the 
inner ball, also of brass ; it screws oi* to a brass stem i, termi- 
nated above by a brass ball B ; /, / is a mass of shell-lac, 
moulded carefully on to i y and serving both to suppoit and in- 
sulate it and its balls h , B. The shell-lac stem / is fitted into 
the socket g , by a little ordinary resinous cement, more fusible 
than shell-lac, applied at m m in such a way as to give sufficient 
strength and render the apparatus air-tight there, yet leave as 
much as possible of the lower part of the shell-lac stem un- 
touched, as an insulation between the ball h and the surround- 
ing sphere a , a . The ball h has a small aperture at n , so that 
when the apparatus is exhausted of one gas and filled with 
another, the ball h may itself also be exhausted and filled, that 
no variation of the gas in the interval o may occur during the 
course of an experiment. 

1189. It will be unnecessary to give the dimensions of all the 
parts, since the drawing is to a scale of one half : the inner 
ball has a diameter of 2’33 inches, and the surrounding sphere 
an internal diameter of 3*57 inches. Hence the width of the 
intervening space, through which the induction is to take place, 
is O' 62 of an inch ; and the extent of this place or plate, L e . 
the surface of a medium sphere, may be taken as twenty-seven 
square inches, a quantity considered as sufficiently large for the 
comparison of different substances. Great care was taken in 
finishing well the inducing surfaces of the ball k and sphere a, 
a ; and no varnish or lacquer was applied to them, or to any 
part of the metal of the apparatus. 

1190. The attachment and adjustment of the shell -lac stew 



373 


Nov. 1837.] Inductive apparatus : — precautions. 

waa a matter requiring considerable care, especially as, in con- 
sequence o f its cracking, it had frequently to be renewed. The 
best lac was chosen and applied to the wire i, so as to be in 
good contact with it everywhere, and in perfect continuity 
throughout its own mass. It was not smaller than is given by 
scale in the drawing, for when less it frequently cracked within 
a few hours after it was cold. I think tliat very slow cooling or 
annealing improved its quality in this, respect. The collar g 
was made as thin as could be, that the lac might bo as wide 
there as possible. In order that at every re-attachment of the 
stem to the upper hemisphere the ball h might have the same 
relative position, a gauge p (fig. 105.) was made of wood, and 
this being applied to the ball and hemisphere whilst the cement 
at m was still soft, the bearings of the ball at q and the he- 
misphere at r r , were forced home, and the whole left until cold. 
Thus all difficulty in the adjustment of the ball in the sphere 
was avoided. 

1191. I had occasion at first to attach the stem to the socket 
by other means, as a band of paper or a plugging of white silk 
thread; but these were very inferior to the cement, interfering 
much with the insulating power of the apparatus. 

1192. The retentive power of this apparatus was, when in 
good condition, better than that of the electrometer (118(5.) 

e. the proportion of loss of power was less. Thus when the 
apparatus was electrified, and also the balls in the electrometer, 
to such a degree, that after the inner ball had been in contact 
with the top k of the ball of the apparatus, it caused a repulsion 
indicated by 6,00° of torsion force, then in hilling from 000° 
to 400° the average loss was 8°*6 per minute; from 1*00° to 300° 
the average loss was 2°*6 per minute ; from 300° to 206° it was 
1°*7 per minute; from 200° to 170° it was 1° p^r minute. This 
was after the apparatus had been charged for a short time ; at 
the first instant of charging there is an apparent loss of elec- 
tricity, which can only be comprehended hereafter (1207. 
1250,), 

119^When the apparatus loses its insulating power sud- 
denly, it m almost always from a crack near to or within the 
brass socket These cracks are usually transverse to the stem. 
If they occur at the part attached by common cement to the 
socket, the air cannot enter, and thus constituting vacua, they 



374 Inductive apparatus described. [Series XI. 

conduct away the electricity and lower the charge, as fast* al- 
most as if a piece of metal had been introduced there. Occa- 
sionally stems in this state, being taken out and .cleared from 
the common cement, may by the ^careful application of the 
heat of a spirit-lamp, be so far softened and melted as to 
restore the perfect continuity of the parts ; but if that does not 
succeed in replacing things in a good condition, the remedy is a 
new shell-lac stem. 

1191. The apparatus when in order could easily be exhausted 
of air and filled with any given gas ; but when that gas was 
acid or alkaline, it could not properly be removed by the air- 
pump, and yet required to be perfectly cleared away. In such 
cases the apparatus was opened and emptied of gas ; and with 
respect to the inner ball A, it was washed out two or three times 
with distilled water introduced at the screw-hole, and then being 
heated above 212°, air was blown through to render the interior 
perfectly dry. 

1195. The inductive apparatus described is evidently a 
Leyden phial, with the advantage, however, of having the di- 
electric or insulating medium changed at pleasure. The balls 
h and R, with the connecting- wire i , constitute the charged 
conductor, upon the surface of which all the electric force is 
resident by virtue of induction (1178.). Now though the 
largest portion of this induction is between the ball h and the 
surrounding sphere a a } yet the wire i and the ball B deter- 
mine a part of the induction from their surfaces towards the 
external surrounding conductors. Still, as all things in that 
respect remain the same, whilst the medium within at o o, may 
be varied, any changes exhibited by the whole apparatus will in 
such cases depend upon the variations made in the interior ; 
and these were 4he changes I was in search of, the negation or 
establishment of such differences being the great object of my 
inquiry. I considered that these differences, if they existed, 
would be most distinctly set forth by having two apparatus of 
the kind described, precisely similar in every respect ; and 
then, different insulating media being within, to charge one 
and measure it, and after dividing the charge with the other, 
to observe what the ultimate conditions of both were. If insu- 
lating media really had any specific differences iff favouring or 
opposing inductive action through them, such' differences, I 



Nov. 1837.] Inductive apparatus used . 375 

conceived, could not fail of being developed by such a pro- 
cess. 

1196. I will wind up this description of the apparatus, and 
explain the precautions necessary to their use, by describing 
the form and order of tlfe experiments made to prove their 
equality when both contained common air. In order to faci- 
litate reference I will distinguish the two by the terms App. i. 
and App. ^i. 

1197. The electrometer is first to be adjusted and examined 
(1181.), and the app. i. and ii. are to be perfectly discharged. 
A Leyden phial is to be charged to such a degree that it 
would give a spark of about onc-sixtecnth or one-twentieth of 
an inch in length between two balls of half an inch diameter ; 
and the carrier ball of the electrometer being charged by this 
phial, is to be introduced into the electrometer, and the lever 
ball brought by the motion of the torsion index against it ; the 
charge is thus divided between the balls, and repulsion ensues. 
It is useful then to bring the repelled ball to the standard dis- 
tance of 30° by the motion of the torsion index, and observe 
the force in degrees required for this purpose ; this force will 
in future experiments be called repulsion of the balls . 

1198. One of the inductive apparatus, as, for instance, app. 
i., is now to be charged from the Leyden phial, the latter being 
in the state it was in when used to charge the balls ; the car- 
rier ball is to be brought into contact with the top of its upper 
ball ( h , fig. 104.), then introduced into the electrometer, and 
the repulsive force (at the distance of 30°) measured. Again, 
the carrier should be applied to the app. i. and the measurement 
repeated ; the apparatus i. and ii. are then to be joined, so as 
to divide the charge, and afterwards the force of each mea- 
sured by the carrier ball, applied as before, and the results 
carefully noted. After this both i. and ii are to be discharged ; 
then app. ii. charged, measured, divided with app. i., and the 
force of each again measured and noted. If in each case the 
half charges of app. i. and ii. are equal, and are together equal 
to the who)e charge before division, then it may he considered 
as proved that the two apparatus are precisely equal in power, 
and fit to be used in cases of comparison between different in- 
sulating media Or dielectrics* 

1199* But the pre cautions necessary to obtain accurate re- 



376 Inductive apparatus : — precautions . [Series XI. 

suits are numerous. The apparatus i. and ii. must always be 
placed on a thoroughly uninsulating medium. A mahogany ta- 
ble, for instance, is far from satisfactory in this respect, and 
therefore a sheet of tinfoil, connected with an extensive dis- 
charging train (292.), is what I have used. They must be so 
placed also as not to be too near each other, and yet equally 
exposed to the inductive influence of surrounding objects ; and 
these objects, again, should not be disturbed in their position 
during an experiment, or else variations of induction upon the 
external ball 11 of the apparatus may occur, and so errors be 
introduced into the results. The carrier ball, when receiving 
its portion of electricity from the apparatus, should always be 
applied at the same part of the ball, as, for instance, the sum- 
mit k , and always in the same way variable induction from 
the vicinity of the head, hands, &c. being avoided, and the ball 
after contact being withdrawn upwards in a regular and con- 
stant manner. 

1200. As the stem had occasionally to be changed (1190.), 
and the change might occasion slight variations in the position 
of the ball within, 1 made such a variation purposely, to the 
amount of an eighth of an inch (which is far more than ever 
could occur in practice), but did not find that it sensibly altered 
the relation of the apparatus, or its inductive condition as a 
whole . Another trial of the apparatus was made as to the ef- 
fect of dampness in the air, on*e being filled with vei^y dry air, 
and the other with air from over water. Though this produced 
no change in the result, except an occasional tendency to more 
rapid dissipation, yet the precaution was always taken when 
working with gases (1290.) to dry them perfectly. 

1201. It is essential that the interior of the apparatus should 
be perfectly free from dust or small loose particles , for these 
very rapidly lower* the charge and interfere on occasions when 
their presence and action would hardly be expected. To breathe 
on the interior of the apparatus and wipe it out quietly with a 
clean silk handkerchief, is an effectual way of removing them ; 
but then the intrusion of other particles should be carefully 
guarded against, and a dusty atmosphere should fo* this and 
several other reasons be avoided- 

1202. The shell -lac stem requires occasionally to be well 
wiped, to remove, in the first instance, the film of Wax and ad- 



377 


Nov. 1837.] Dust removed ; — stem discharged. 

hering matter which is upon it ; and afterwards to displace dirt 
and dust which will gradually attach ‘to it in the course of ex- 
periments. I have found much to depend upon this precaution, 
and a silk handkerchief is the best wiper. 

1203. But wiping and sdme other circumstances tend to gi\e 
a charge to the surface of the shell-lac stem. This should be 
removed, for, if allowed to remain, it very seriously affects the 
degree of charge given to the carrier ball by the apparatus 
(1232.). This condition of the stem is best obser\ed by dis- 
charging the apparatus, applying the carrier ball to the stem, 
touching it with the finger, insulating and removing it, and ex- 
amining whether it lias received any charge (by induction) from 
the stern; if it lias, the stem itself is in a charged state. The 
best method of removing* the charge I have found to he, to 
cover the finger with a single fold of a silk handkerchief, and 
breathing on the stem, to wipe it immediately after with the 
finger; the ball B and its connected wire, &e. being at the same 
time uninsulated : the wiping place of the silk must not he 
changed ; it then becomes sufficiently damp not to excite the 
stem, and is yet dry enough to leave it in a clean and excellent 
insulating condition. If the air be dusty, it xv ill be found that 
a single charge of the apparatus w ill bring on an electric state 
of the outside of the stem, in consequence of the carrying power 
of the particles of dust ; whereas in the morning, and in a room 
which has been left quiet, several experiments can be made in 
succession without the stem assuming the least degree of charge. 

1204. Experiments should not be made by candle or lamp 
light except with much care, for flames have great and yet un- 
steady powers of affecting and dissipating electrical charges. 

1205. As a final observation on the state of .the apparatus, 
they should retain their charges well and uniformly, and alike 
for both, and at the same time allow of a perfect and instanta- 
neous discharge, giving afterwards no charge to the carrier 
ball, whatever part of the ball B it may be applied to (1218.). 

1206* With respect to the balance electrometer, all the pre- 
cautions that need be mentioned, are, that the carrier ball is to 
be during the first part of an experiment in its elec- 

trified states the logs of electricity which would follow upon its 
disohe^gfe Mhf avoided; and that in introducing it into .the 
ele^t remoter through the hole in the glass plate above, care 



378 Inductive apparatus used, [Series XI. 


should be taken that it do not touch, or even come near to,, the 
edge of the glass. 

1207. When the whole charge in one apparatus is divided 
between the two, the gradual fall, apparently from dissipation, 
in the apparatus which has received the half charge is greater 
than in the one originally charged. This is due to a peculiar 
effect to be described hereafter (1250. 1251.), the interfering 
influence of which may be avoided to a great extept by going 
through the steps of the process regularly and quickly ; there- 
fore, after the original charge has been measured, in app. i. for 
instance, i. and ii. are to be symmetrically joined by their balls 
B, the carrier touching one of these balls at the same time ; it 
is first to be removed, and then the apparatus separated from 
each other ; app. ii. is next quickly to be measured by the car- 
rier, then app. i . ; lastly, ii. is to be discharged, and the dis- 
charged carrier applied to it to ascertain whether any residual 
effect is present (1205.), and app. i. being discharged is also to 
be examined in the same manner and for the same purpose. 

1208. The following is an example of the division of a charge 
by the two apparatus, air being the dielectric inbothof them. The 
observations are set down one under the other in the order in 
which they were taken, the left hand numbers representing the 
observations made on app. i., and the right hand numbers those 
on app. ii. App. i. is that which was originally charged, and 
after two measurements, the charge was divided with app. ii. 


App. i. 


254° 

250 


App. ii. 

Balls 160° 

, . . . 0 ° 


divided and instantly taken 
.... 122 
124 .... 

1 .... after being discharged 

. . . . 2 after being discharged. 


1209. Without endeavouring to allow for the lose which must 
have been gradually going on during the time of the experiment, 
let us observe the results of the numbers as they stand. As 1° 
remained in app. i. in an undischargeable state, 249° may be 



Nov. 1837.] 


379 


Division of a charge. 

taken as the utmost amount of the transferable or divisible 
charge, the half of which is 121<°*5. As app. ii. was free of 
charge in the first instance, and immediately after the division 
was found with 122°, this^amount at least may betaken as what 
it had received. On the other hand 121° minus 1°, or 123°, 
may be taken as the half of the transferable charge retained by 
app. i. Now these do not differ much from each other, or from 
124°'5, thfc half of the full amount of transferable charge ; and 
when the gradual loss of charge evident in the difference be- 
tween 254° and 250° of app. i. is also taken into account, there 
is every reason to admit the result as showing an equal division 
of charge, unattended by any disappearance of power except 
that due to dissipation. 

1210. I will give another result, in which app. ii. was first 
charged, and where the residual action of that apparatus w as 
greater than in the former ease. 

App. i. App. ii. 

Balls 150° 

.... 152° 

. . . . 118 

divided and instantly taken 
70° ... . 

.... 78 

. . . . 5 .immediately after discharge. 

0 immediately after discharge. 

1211. The transferable charge being 148° — 5°, its half is 
71°*5, which is not far removed from 70°, the half c harge of i. ; 
or from 73°,. the half charge of ii. : these half charges again 
making up the sum of 143°, or just the amount of the whole 
transferable charge. Considering the errors of experiment, 
therefore, these results may again be received as showing that 
the apparatus were equal in inductive capacity, or in their 
powers of receiving charges. 

1212. The experiments were repeated with charges of nega- 
tive electricity with the same general results. 

1213. That I might be sure of the sensibility and action of 
the apparatus, I made such a change in one as ought upon 
principle to increase its inductive force, i . e. I put a metallic 
lining into 1 the lower hemisphere of app. i., so as to diminish 
the thickness of the intervening air in that part, from 0 62 to 



380 Induction in curved lines. [Series XI. 

0‘435 of an inch : this lining was carefully shaped and rounded 
so that it should not present a sadden projection within at its 
edge, but a gradual transition from the reduced interval in the 
lower part of the sphere to the largely one in the upper. 

1214. This change immediately caused app. i. to produce 
effects indicating that it had a greater aptness or capacity for 
induction than app. ii. Thus, when a transferable charge in 
app. ii. of 469° was divided with app. i., the former retained a 
charge of 225°, whilst the latter showed one of 22 7°, i. e. the 
former had lost 244° in communicating 227° to the latter : on 
the other hand, when app. i. had a transferable charge in it of 
381° divided by contact with app. ii., it lost 181° only, whilst it 
gave to app. ii. as many as 194 : — the sum of the divided forces 
being in the first instance less , and in the second instance 
greater than the original undivided charge. These results are 
the more striking, as only one half of the interior of app. i. was 
modified, and they show that the instruments are capable of 
bringing out differences in inductive force from amongst the 
errors of experiment, when these differences are much less than 
that produced by the alteration made in the present instance. 

If iv. Induction in curved lines. 

1215. Amongst those results deduced from the molecular 
view of induction (1166.), whjch, being of a peculiar nature, 
are the best tests of the truth or error of the theory, the ex- 
pected action in curved lines is, I think, the most important at 
present ; for, if shown to take place in an unexceptionable man- 
ner, I do not see how the old theory of action at a distance and 
in straight lines can stand, or how the conclusion that ordinary 
induction's an action of contiguous particles can be resisted. 

1216. There are*, many forms of old experiments which might 
be quoted as favourable to, and consistent with the view I have 
adopted. Such arc most cases of electro-chemical decomposition, 
electrical brushes, auras, sparks, &c. ; but as these might be 
considered equivocal evidence, inasmuch as they include a cur- 
rent and discharge, (though they have long been to njp indi- 
cations of prior molecular action (1230.) ) I end^vourm to de- 
vise such experiments for first proofs as should^ not include 
transfer, but relate altogether to. the pure Simple inductive ac- 
tion of statical electricity. 



Induction in curved tines. 


Nov. 1837.] 


381 


1217. It was also of importance to make these experiments 
in the simplest possible manner, using not more than one in- 
sulating medium or dielectric at a time, lest differences of slow 
conduction should produce effects which might erroneously be 
supposed to result from induction in curved lines. It will be 
unnecessary to describe the steps of the investigation minutely ; 
I will at once proceed to the simplest mode of proving the facts, 
first in air and then in other insulating media. 

1218. A cylinder of solid shell-lac, 09 of an inch in diameter 
and seven inches in length, was fixed upright in a wooden foot 
(fig. (106.) : it was made concave or cupped at its upper extre- 
mity so that a brass ball or other small arrangement could stand 
upon it. The upper half of the stem having been excited nrt/a- 
tively by friction with wapn flannel, a brass ball, B, 1 inch in 
diameter, was placed on the top, and then the whole arrange- 
ment examined by the carrier ball and Coulomb's electrometer 
(1180. &c.). For this purpose the balls of the electrometer 
were charged positively to about 360°, and then the carrier 
being applied to various parts of the ball B, the tuo were un- 
insulated whilst in contact or in position, then insulated*, se- 
parated, and the charge of the carrier examined as to its nature 
and force. Its electricity was always positive, and its force at 
the different positions «, b> c y d } &c. (figs. 106. and 107.) ob- 
served in succession, was as follows : 

at a . . above 1000° 

b it was . . . 1 19 

c 270 

d 512 

b 130 

1219. To comprehend the full force of these result®, it must 
first be understood, that all the charges of the ball B and the 
carrier are charges by induction, from the action of the excited 
surface of the shell-lac cylinder; for whatever electricity the 
ball B received by communication from the shell-lac, either in 
the first instance or afterwards, was rcitiovcd by the uninsula- 

* It can hardly be necessary for me to say here, that whatever general Htuto 
the carrier bait acquired in any place where it was uninsulated and then insu- 
lated, it retained on removal from that place, notwithstanding that it might 
|HU» through Other places that would have given to it, if uninsulated, a different 
condition. 



382 Induction in curved lines, [Series XI. 

ting contacts, only that due to induction remaining; and this 
is shown by the charges taken from the ball in this its uninsu- 
lated state being always positive, or of the contrary character 
to the electricity of the shell-lac. In the next place, the charges 
at a, c, and d were of such a nature *as might be expected from 
an inductive action in straight lines, but that obtained at b is 
not so : it is clearly a charge by induction, but induction in d 
curved line ; for the carrier ball whilst applied to b } and after 
its removal to a distance of six inches or more from B, could 
not, in consequence of the size of B, be connected by a straight 
line with any part of the excited and inducing shell-lac. 

1220. To suppose that the upper part of the uninsulated ball 
B, should in some way be retained in an electrified state by that 
portion of the surface of the ball whicji is in sight of the shell-lac, 
would be in opposition to what we know already of the subject. 
Electricity is retained upon the surface of conductors only by 
induction (1178.) ; and though some persons may not be pre- 
pared as yet to admit this with respect to insulated conductors, 
all will as regards uninsulated conductors like the ball B ; and 
to decide the matter wc have only to place the carrier ball at e 
(fig. 107.), so that it shall not come in contact with B, uninsu- 
late it by a metallic rod descending perpendicularly, insulate it, 
remove it, and examine its state ; it will be found charged with 
the same kind of electricity as, and even to a higher degree 
(1224.) than, if it had been in contact with the summit of B. 

1221. To suppose, again, that induction acts in some way 
through or across the metal of the ball, is negatived by the 
simplest considerations ; but a fact in proof will be better. If 
instead of the ball B a small disc of metal be used, the carrier 
may be charged at, or above the middle of its upper surface : 
but if the plate be enlarged to about 1^ or 2 inches in diameter, 
C (fig. 108,), then no charge will be given to the carrier at/, 
though when applied nearer to the edge at g , or even above the 
middle at h, a charge will be obtained ; and this is true though 
the plate may be a mere thin film of gold-leaf. Hence it is clear 
that the induction is not through the metal, but through the 
surrounding air or dielectric , and that in curved lines. 

1222. I had another arrangement, in which a wire passing 
downwards through the middle of the shell-lac cylinder to the 
earth, was connected with the ball B (fig. 109.) as to keep 



Nov. 1837.] Lateral tension of lines of induction . 


383 


it in a constantly uninsulated state. This was a very conveni- 
ent form of apparatus, and the results with it were the same as 
those just described. 

1223. In another case the ball B was supported by a shell- 
lac stem, independently of the excited cylinder of shell-lac, and 
at half an inch distance from it ; but the effects were the same. 
Then the brass ball of a charged Leyden jar was used in place 
of the excited shell-lac to produce induction ; but this caused 
no alteration of the phenomena. Both positive and negative 
inducing charges were tried with the same general results. Fi- 
nally, the arrangement was inverted in the air for the purpose 
of removing every possible objection to the conclusions, but 
they came out exactly the same. 

1224. Some results obtained with a brass hemisphere instead 
of the ball B were exceedingly interesting. It was 1*36 of an 
inch in diameter, (fig. 110.), and being placed on the top of the 
excited shcll-lac cylinder, the carrier ball was applied, as in 
the former experiments (1218.), at the respective positions de- 
lineated in the figure. At i the force was 1 12°, at k 108°, at l 
65°, at m 35° ; the inductive force gradually diminishing, as 
might have been expected, to this point. But on raising the 
carrier to the position n , the charge increased to 87°; and on 
raising it .still higher to o , the charge still further increased to 
105° : at a higher point still, p , the charge taken was smaller in 
amount, being 98°, and continued to diminish for more elevated 
positions. Here the induction fairly turned a corner. Nothing, 
in fact, can better show both the curved lines or courses of the 
inductive action, disturbed as they are from their rectilineal 
form by the shape, position, and condition of the metallic he- 
misphere ; and also a lateral tension , so to speak, of these lines 
on one another : — all depending, as I conceive, on induction 
being an action of the contiguous particles of the dielectric, 
■which being thrown into a state of polarity and tension, arc in 
mutual relation by their forces in all directions. 

1225. As another proof that the whole of these actions were 
inductive I may state a result which was exactly what might be 
expected, namely, that if uninsulated conducting matter was 
brought round and near to the excited shell -lac stem, then the 
inductive force w as directed towards it, and could not be found 
on the top of the hemisphere. Removing this matter the lines 



384 Curved induction across air , solids , fyc. [Series XI. 

of force resumed their former direction. The experiment af- 
fords proofs of the lateral tension of these lines, and supplies a 
warning to remove such matter in repeating the above investi- 
gation. 

1226. After these results on curved inductive action in air I 
extended the experiments to other gases, using first carbonic acid 
and then hydrogen : the phenomena were precisely those already 
described. In these experiments I found that if the gases were 
confined in vessels they required to be very large, for whether 
of glass or earthenware, the conducting power of such materials 
is so great that the induction of the excited shell-lac cylinder 
towards them is as much as if they were metal ; and if the ves- 
sels be small, so great a portion of the inductive force is deter- 
mined towards them that the lateral, tension or mutual repul- 
sion of the lines of force before spoken of (1224.), by which their 
inflexion is caused, is so much relieved in other directions, that 
no inductive charge will be given to the carrier ball in the posi- 
tions k y /, m, n , o,p, (fig. 110.). A very good mode of making 
the experiment is to let large currents of the gases ascend or 
descend through the air, and carry on the experiments in these 
currents. 

1227. These experiments were then varied by the substitution 
of a liquid dielectric, namely, oil of turpentine , in place of air 
and gases. A dish of thin glass well covered with a film of shell- 
lac, (1272.) which was found ‘by trial to insulate well, had some 
highly rectified oil of turpentine put into it to the depth of half 
an inch, and being then placed upon the top of the brass hemi- 
sphere (fig. 1 10.), observations were made with the carrier ball as 
before (1221.) . The results were the same, and the circumstance 
of some qf the positions being within the fluid and some without, 
made no sensible ^difference. 

1228. Lastly, 1 used a few solid dielectrics for the same pur- 
pose, and with the same results. These were shell-lac, sulphur, 
fused and cast borate of lead, flint glass well covered with a 
film of lac, and spermaceti. The following was the form of ex- 
periment with sulphur, and all were of the same kind. A square 
plate of the substance, two inches in extent and 06 of an inch 
in thickness, was cast with a small hole or depression in the 
middle of one surface to receive the carrier ball. This was 
placed upon the surface of the metal hemisphere (fig. 112.). 



385 


Nov. 1837.] Static induction in curved tines . 

arranged on the excited lac as in former cases, and observations 
wert) made at n, o, p, and q. Great care was required in these 
experiments to free the sulphur or other solid substance from 
any charge it might previously have received. This was done 
by breathing and wiping (1203.), and the substance being found 
free from all electrical excitement, was then used in the expe- 
riment ; after which it was removed and again examined, to 
ascertain that it had received no charge, but had acted really as 
a dielectric.* With all these precautions the results were the 
same: and it is thus very satisfactory to obtain the curved in- 
ductive action through solid bodies , as any possible effect from 
the translation of charged particles in fluids or gases, which 
some persons might imagine to be the' case, is hero entirely 
negatived. 

1229. In these experiments with solid dielectrics, the degree 
of charge assumed by the carrier ball at the situations >t, o, p 
(fig. 112.), was decidedly greater than that given to the ball at 
-the same places when air only intervened between it and the 
metal hemisphere. This effect is consistent with what will 
hereafter be found to be the respect ive relations of those bodies, 
as to their power of facilitating induction through them (1209. 
1273. 1277.). 

1230. 1 might quote many other forms of experiment, some 
old and some new, in which induction in curved or contorted 
line's take place, but think it numVessary after the preceding 
results ; I shall therefore mention but two. If a conductor A, 
(fig. 111.) be electrified* and an uninsulated metallic hall 15, or 
even a plate, provided the edges be not too thin, be* held before 
it, a small electrometer at cor at d, uninsulated, will give signs 
of electricity, opposite in its nature to that of A, and therefore 
caused by induction, although the influencing and influenced 
bodies cannot be joined by a right line passing through the 
air. Or if, the electrometers being removed, a point be fixed 
at the back of the ball in its uninsulated state as at C, this 
point will become luminous and discharge the conductor A. 
The latter experiment is described by Nicholson*, who, how- 
ever, reasons erroneously upon it. As to its introduction bore, 
though it is a case of discharge, the discharge is preceded by 
induction, and that induction must be in curved lines. 

* Encyclopaedia Britannica, vol. vi. p. 504. 

2 C 



386 Lines of inductive force. [Series XI. 

1231. As argument against the received theory of induction 
and in favour of that which I have ventured to put forth, I 'can- 
not see how the preceding results can be avoided. The effects 
are clearly inductive effects produced by electricity, not in cur- 
rents but in its statical state, and this induction is exerted in 
lines of force which, though in many experiments they may be 
straight, are here curved more or less according to circum- 
stances. I use the term line of inductive force merely as a 
temporary conventional mode of expressing the direction of the 
power in cases of induction ; and in the experiments with the 
hemisphere (1224.), it is curious to see how, when certain lines 
have terminated on the under surface and edge of the metaL 
those which were before lateral to them expand and open out 
from each other , some bending ropnd and terminating their 
action on the upper surface of the hemisphere, and others meet- 
ing, as it were, above in their progress outwards, uniting their 
forces to give an increased charge to the carrier ball, at an 
increased distance from the source of power, and influencing 
each other so as to cause a second flexure in the contrary direc- 
tion from the first one. All this appears to me to prove that 
the whole action is one of contiguous particles, related to each 
other, not merely in the lines which they may be conceived to 
form through the dielectric, between the inductric and the 
inducteous surfaces (1483.), but in other lateral directions also. 
It is this which gives an effect equivalent to a lateral repulsion 
or expansion in the lines of force I have spoken of, and enables 
induction to turn a corner (1301.). Th& power, instead of being 
like that of gravity, which causes particles to act on each other 
through straight lines, whatever other particles may be between 
them, more analogous to that of a series of magnetic needles, 
or to the condition of the particles considered as forming the 
whole of a straight or a curved magnet. So that in whatever 
way I view it, and with great suspicion of the influence of 
favourite notions over myself, I cannot perceive how the 
ordinary theory applied to explain induction can be a correct 
representation of that great natural principle of electrical action. 

1232. I have had occasion in describing the precautions 
necessary in the use of the inductive apparatus, to refer to one 
founded on induction in curved lines (1203.) ; and after the ex- 
periments already described, it will easily be seen how great an 



387 


Nov. 1837.] Slow conduction by shell-lac . 

influence the shell-lac stem may exert upon tlie charge of the 
carrier ball when applied to the apparatus (1218.), unless that 
precaution be attended to. 

1233. I think it expedient, next in the course of these expe- 
rimental researches, to describe some effects due to conduction , 
obtained with such bodies as glass, lac, sulphur, &c., which had 
not been anticipated. Being understood, they will make us 
acquainted .with certain precautions necessary in investigating 
the great question of specific inductive capacity. 

1231. One of the inductive apparatus already described 
(1187, &c.) had a hemispherical cup of shell-lac introduced, 
which being in the interval between the inner ball and the 
lower hemisphere, nearly occupied the space there ; conse- 
quently when the apparatus was charged, the lac was the di- 
electric or insulating medium through which the induction took 
place in that part. When this apparatus was first charged 
with electricity (1198.) up to a certain intensity, as 400°, mea- 
sured by the Covlomb*s electrometer (1180.), it sank much 
faster from that degree than if it had been previously charged 
to a higher point, and had gradually fallen to 100° ; or than it 
would do if the charge were, by a second application, raised up 
again to 400°; all other things remaining the same. Again, if 
after having been charged for some time, as fifteen or twenty 
minutes, it was suddenly and perfectly discharged, even the 
stem having all electricity removed from it (1203.), then the 
apparatus being left to itself, would gradually recover a charge, 
which in nine or ten nAiutes would rise up to 50° or 60°, and 
in one instance to 80°. 

1235. The electricity, which in these eases returned from an 
apparently latent to a sensible state, was always of the same 
kind as that which had been given by the charge. The return 
took place at both the inducing surfaces ; for if after the per- 
fect discharge of the apparatus the whole was insulated, as the 
inner ball resumed a positive state the outer sphere acquired a 
negative condition. 

1236. This effect was at once distinguished from that pro- 
duced by the excited stem acting in curved lines of induction" 
(1203. 1232.), by the circumstance that all the returned electri- 
city could be perfectly and instantly discharged. It appeared 
to depend upon the shell-lac within, and to be, in some way, 

2 c 2 



388 Disappearance and reproduction of charge ; [Series XI. 

due to electricity evolved from it in consequence of a previous 
condition into which it had been brought by the charge of the 
metallic coatings or balls. 

1237. To examine this state more accurately, the apparatus, 
with the hemispherical cup of shell^lac in it, was charged for 
about forty-five minutes to above 600° with positive electricity 
at the balls h and B. (fig. 101.) above and within. It was then 
discharged, opened, the shell-lac taken out, and its state exa- 
mined ; this was done by bringing the carrier ball near the 
shell-lac, uninsulating it, insulating it, and then observing what 
charge it had acquired. As it would be a charge by induction, 
the state of the ball would indicate the opposite state of elec- 
tricity in that surface of the shell-lac which had produced it. 
At first the lac appeared quite free from any charge ; but gra- 
dually its two surfaces assumed opposite states of electricity, 
the concave surface, which had been next the inner and posi- 
tive ball, assuming a positive state, and the convex surface, 
which had been in contact with the negative coating, acquiring 
a negative state ; these states gradually increased in intensity 
for some time. 

1238. As the return action was evidently greatest instantly 
after the discharge, I again put the apparatus together, and 
charged it for fifteen minutes as before, the inner ball posi- 
tively. I then discharged jit, instantly removing the upper 
hemisphere with the interior ball, and, leaving the shell-lac cup 
in the lower uninsulated hemisphere, examined its inner sur- 
face by the carrier ball as before (123 7.f. In this way I found 
the surface of the shell-lac actually negative , or in the reverse 
state to the ball which had been in it ; this state quickly disap- 
peared, end was succeeded by a positive condition, gradually 
increasing in intensity for some time, in the same manner as 
before. The first negative condition # of the surface opposite 
the positive charging ball is a natural consequence of the state 
of things, the charging ball being in contact with the shell-lac 
only in a few points. It does not interfere with the general 
result and peculiar state now under consideration, except that 
it assists in illustrating in a very marked manner the ultimate 
assumption by tlie surfaces of the shell-lac of an electrified 
condition, similar to that of the metallic surfaces opposed to 
or against them. 



380 


Nov. 1837.] with y lass , spermaceti , sulphur. 

1239. Glass was then examined with respect to its power of 
assuming this peculiar state. I had a thick flint-glass hemi- 
spherical cup formed, which would fit easily into the space o of 
the lower hemisphere (1188. 1180.) ; it had been heated and 
varnished with a solution of shell-lac in alcohol, for the purpose 
of destroying the conducting power of the vitreous surface 
(1254.). Being then well warmed and experimented with, I 
found it could also assume the same state , but not apparently 
to the same degree, the return action amounting in different 
cases to quantities from 6° to 18°. 

1240. Spermaceti experimented with in the same manner 
gave striking results. When the original charge had been sus- 
tained for fifteen or twenty minutes at about 50(4, the return 
charge was equal to 95° or 100°, and was about fourteen minute's 
arriving at the maximum effect. A charge continued for not 
more than two or three seconds was here succeeded by a re- 
turn charge of 50° or (10°. The observations formerly made 
(1234.) held good with this substance. Spermaceti, though it 
will insulate a low charge for some time, is a better conductor 
than slioll-lac, glass, and sulphur; and this conducting power 
is connected with the readiness with which it exhibits tin* par- 
ticular effect under consideration. 

1211. Sulphur . — I was anxious to obtain the amount of effect 
with this substance, first, because it is an excellent insulator, 
and in that respect would illustrate the reflation of the effect to 
the degree of conducting power possessed by the dielectric 
(1247.) ; and in the nc^ place, that 1 might obtain that body 
giving the smallest degree of the effect now under consideration, 
for the investigation of the question of specific inductive capa- 
city (1277.). 

1212. With a good hemispherical cup of sulphur cast solid 
and sound, I obtained the return charge, but only to an amount 
of 17° or 18°. Thus glass and sulphur, which are bodily very 
bad conductors of electricity, and indeed almost perfect insu- 
lators, gave very little of this return charge. 

1243. I tried the same experiment having air only in the in- 
ductive apparatus. After a continued high charge for some 
time I could obtain a little effect of return action, but it was 
ultimately traced t6 the shell- lac of the stem. 

1244. I sought to produce something like this state w ith one 



390 


Slow conduction by good insulators . [Series XI. 

electric power and without induction ; for upon the theory of 
an' electric fluid or fluids, that did not seem impossible, and then 
I should have obtained an absolute charge (1169. 1177.), or 
something equivalent to it. In this I could not succeed. I ex- 
cited the outside of a cylinder of shell-lac very highly for some 
time, and then quickly discharging it (1203.), waited and watched 
whether any return charge would appear, but such was not the 
case. This is another fact in favour of the inseparability of the 
two electric forces (1177,), and another argument for the view 
that induction and its concomitant phenomena depend upon a 
polarity of the particles of matter. 

1245. Although inclined at first to refer these effects to a 
peculiar masked condition of a certain portion of the forces, 

I think I have since correctly traced' them to known principles 
of electrical action. The effects appear to be due to an actual 
penetration of the charge to some distance within the electric, 
at each of its two surfaces, by what we call conduction ; so that,, 
to use the ordinary phrase, the electric forces sustaining the 
induction arc not upon the metallic surfaces only, but upon and 
within the dielectric also, extending to a greater or smaller 
depth from the metal linings. Let c (fig. 113.) be the section 
of a plate of any dielectric, a and b being the metallic coatings ; 
let b be uninsulated, and a be charged positively ; after ten or 
fifteen minutes, if a and b be discharged, insulated, and imme- 
diately examined, no electricity will appear in them ; but in a 
short time, upon a second examination, they will appear charged 
in the same way, though not to the same degree, as they were at 
first. Now suppose that a portion of the positive force has, under 
the coercing influence of all the forces concerned, penetrated the 
dielectric and taken up its place at the line a corresponding 
portion of the negative force having also assumed its position 
at the line n \ that in fact the electric at these two parts has 
become charged positive and negative ; then it is clear that the 
induction of these two forces will be much greater one towards 
the other, and less in an external direction, now that they are 
at the small distance np from each other, than when they Vere 
at the larger interval a b. Then let a and b be discharged ; 
the discharge destroys or neutralizes all external induction, and 
the coatings are therefore found by the carrier ball unelectrified 
but it also removes almost the whole of the forces by which the 



Nov. 1837.] Conductive properties of lac, sulphur, fyc. 391 

electric charge was driven into the dielectric, and though pro- 
bably a part of that charge goes forward in its passage and ter- 
minates in what we call discharge, the greater portion returns 
on its course to the surfaces of c, and consequently to the con- 
ductors a and b, and constitutes the recharge observed. 

1216. The following is the experiment on which I rest for 
the truth of this view. Two plates of spermaceti, d and / (fig. 
114.), were put together to form the dielectric, a and b being 
the metallic coatings of this compound plate, as before. The 
system was charged, then discharged, insulated, examined, and 
found to give no indications of electricity to the carrier ball. 
The plates d and / were then separated from each other, and 
instantly a with d was found in a positive state, and b with / in 
a negative state, nearly all the electricity being in the linings a 
and b. Hence it is clear that, of the forces sought for, the 
positive was in one half of the compound plate and the negative 
in the other half; for when removed bodily with tint plates 
from each other's inductive influence, they appeared in separate 
places, and resumed of necessity their power of acting by in- 
duction on tlie electricity of surrounding bodies. Had the 
effect depended upon a peculiar relation of the contiguous par- 
ticles of matter only, then each half plate, d and /, should have 
shown positive force on one surface and negative on the other. 

1247. Thus it would appear tjiat the best solid insulators, 
such as shell-lac, glass and sulphur, have conductive properties 
to such an extent, that electricity can penetrate them bodily, 
though always subject to the overruling condition of induction 
(1178.). As to the depth to which the forces penetrate in this 
form of charge of the particles, theoretically, it should be 
throughout the mass, for what the charge of the metrJ does for 
the portion of dielectric next to it, should* he done by the 
charged dielectric for the portion next beyond it again ; but 
probably in the best insulators the sensible charge is to a very 
small depth, only in the dielectric, for otherwise more would 
disappear in the first instance whilst the original charge is sus- 
tained, less time would be required for the assumption of the 
particular state, and more electricity would re-appear as return 
chaise. 

. 124$. The condition of time required for this penetration of 
the charge is important, both as respects the general relation 



392 Residual charge .* — precautions. [Series XI. 

of the cases to conduction, and also the removal of an objection 
that might otherwise properly be raised to certain results re- 
specting specific inductive capacities, hereafter to be given 
(12G9. 1277.). 

1249. It is the assumption for a time of this charged state of 
the glass between the coatings in the Leyden jar, which gives 
origin to a well-known phenomenon, usually referred to the 
diffusion of electricity over the uncoatcd portion of the glass, 
namely, the residual charge . The extent of charge which can 
spontaneously be recovered by a large battery, after perfect 
uninsulation of both surfaces, is very considerable, and by far 
the largest portion of this is due to the return of electricity in 
the manner described. A plate of shell-lac six inches square, 
and half an inch thick, or a similar plate of spermaceti an inch 
thick, being coated on the sides with tinfoil as a Leyden ar- 
rangement, will show this effect exceedingly well. 


1250. The peculiar condition of dielectrics which has now 
been described, is evidently capable of producing an effect in- 
terfering with the results and conclusions drawn from the use 
of the two inductive apparatus, when shell-lac, glass, &c. is used 
in one or both of them (1192. 1207.); for upon dividing the 
charge in such cases according to the method described (1198. 
1207.), it is evident that the apparatus just receiving its half 
charge must fall faster in its tension than the other. For sup- 
pose app. i. first charged, and app. ii. used to divide with it ; 
though both-may actually lose alike, yet app. i., which has been 
diminished one half, will be sustained by a certain degree of 
return action or charge (1234.), whilst app. ii. will sink the more 
rapidly from the poraing on of the particular state. I have 
endeavoured to avoid this interference by performing the whole 
process of comparison as quickly as possible, and taking the 
force of app. ii. immediately after the division, before any sen- 
sible diminution of the tension arising from the assumption of 
^the peculiar state could be produced ; and I have assumed that 
as about three minutes pass between the first charge of app. i. 
and the division, and three minutes between the division and 
discharge, when the force of the non-transferable electricity is 
measured, the contrary tendencies for those periods would keep 



Nov. 1837.] Specific inductive capacity. 393 

th^t apparatus in a moderately steady and uniform condition 
for the latter portion of time . 

1251. The particular action described occurs in the shell-lac 
of the stems, as well as in the dielectric used within the appa- 
ratus. It therefore constitutes a cause by which the outside of 
the stems may in some opei'ations become charged with elec- 
tricity, independent of the action of dust or carrying particles 
(1203.). 


If v. On specific induction y or specific inductive capacity . 

1252. I now proceed to examine the great question of speci- 
fic inductive capacitj r , /. e. whether different dielectric bodies 
actually do possess any influence over the degree of induction 
which takes place through them. If any such difference should 
exist, it appeared to me not only of high importance in the 
further comprehension of the laws and results of induction, but 
an additional and very powerful argument for the theory l have 
ventured to put forth, that the whole depends upon a molecular 
action, in contradistinction to one at sensible distances. 

The question may be stated thus : suppose A an electrified 
plate of metal suspended in the air, and !» and C two exactly 
similar plates, placed parallel to and on each side of A at espial 
distances and uninsulated; A wilt then induce equally towards 
B and C. If in this position of the plates some other dielectric 
than air, as shell-lac, be introduced between A and O, will tbc 
induction between them remain the same? Will the relation 
of C and B to A be unaltered, notwithstanding the difference 
of the dielectrics interposed between them ? * - 

1253* As far as I recollect, it is assumed that no change will 
occur under such variation of circumstances, 6 and that the re- 
lations of B and C to A depend entirely upon their distance. 
I only remember one experimental illustration of the question, 
and that is by Coulomb f, in which he shows that a wire sur- 
rounded by shcll-lac took exactly the same quantity of elec- 
tricity from a charged body as the same wire in air. The ex- 

* Refer for the practical illustration of this statement to the supplementary 
note commencing 1307, &c. — Dec, 1858. 
t M&uoires de l’Academie, 1787, pp. 452, 453. 



394 Choice of good insulators. [Series XI. 

periment offered to me no proof of the truth of the supposition : 
for it is not the mere films of dielectric substances surrounding 
the charged body which have to be examined and compared, 
but the whole mass between that body and the surrounding con- 
ductors at which the induction terminates. Charge depends 
upon induction (1171. 1178.) ; and if induction is related to 
the particles of the surrounding dielectric, then it is related to 
all the particles of that dielectric inclosed by the surrounding 
conductors, and not merely to the few situated next to the 
charged body. Whether the difference I sought for existed 
or not, I soon found reason to doubt the conclusion that might 
be drawn from Coulomb^ result ; and therefore had the appa- 
ratus made, which, witli its use, has been already described 
(1187, &c.), and which appears to m» well suited for the inves- 
tigation of the question. 

1251. Glass, and many bodies which might at first be con- 
sidered as very fit to test the principle, proved exceedingly un- 
fit for that purpose. Glass, principally in consequence of the 
alkali it contains, however well warmed and dried it may be, 
has a certain degree of conducting power upon its surface, de- 
pendent upon the moisture of the atmosphere, which renders 
it unfit for a test experiment. Resin, wax, naphtha, oil of tur- 
pentine, and many other substances were in turn rejected, be- 
cause of a slight degree of conducting power possessed by them ; 
and ultimately shell-lac and sulphur were chosen, after many 
experiments, as the dielectrics best fitted for the investigation. 
No difficulty can arise in perceiving how the possession of a 
feeble degree of conducting power tends to make a body pro- 
duce effects, which would seem to indicate that it had a greater 
capability of allowing induction through it than another body 
perfect in its insulation. This source of error has been that 
which I have found most difficult to obviate in the proving ex- 
periments. 


1255. Induction through shell-lac . — -As a preparatory ex- 
periment, I first ascertained generally that when a part of the 
surface of a thick plate of shell-lac was excited or charged, 
there was no sensible difference in the character of the induc- 
tion sustained by that charged part, whether exerted through 



395 


Nov. 1837.] Induction through shell-lac examined . 

the air in the one direction, or through the shell -lac of the plate 
in the other ; provided the second surface of the plate hnd not, 
by contact wifh conductors, the action of dust, or any other 
means, become charged (1203.). Its solid condition enabled it 
to retain the excited particles in a permanent position, but that 
appeared to be all; for these particles acted just as freely 
through the shell-lac on one side as through the air on the 
other. The same general experiment was made by attaching 
a disc of tinfoil to one side of the shcll-lac plate, and electri- 
fying it, and the results were the same. Scarcely any other 
solid substance than shcll-lac and sulphur, and no liquid sub- 
stance that I have tried will bear this examination. (Hass in 
its ordinary state utterly fails ; yet it was essentially necessary 
to obtain this prior degree of perfection in the dielectric used, 
before any further progress could be made in the principal 
investigation. 

1256. Shell-lac and air were compared in the first place. 
For this purpose a thick hemispherical cup of shell-lac was in- 
troduced into the lower hemisphere of one of the inductive 
apparatus (1187, &c.), so as nearly to fill the lower half of the 
space o , o (fig. 104.) between it and the inner ball ; and then 
charges were divided in the manner already described (1198, 
1207.), each apparatus being used in turn to receive the first 
charge before its division by the.othor. As the apparatus were 
known to have equal inductive power when air was in both 
(1209. 1211.), any differences resulting from the introduction of 
the shell-lac would show a peculiar action in it, and if unequi- 
vocally referable to a specific inductive influence, would estab- 
lish the point sought to be sustained. 1 have already referred 
to the precautions necessary in making the experiments (1199. 
&c.) ; and with respect to the error which might be introduced 
by the assumption of the peculiar state, it was guarded against, 
as far as possible, in the first place, by operating quickly (1248) ; 
and, afterwards, by using that dielectric as glass or sulphur, 
which assumed the peculiar state most slowly, and in the least 
degree (1239. 1241.). 

1257. The shell-lac hemisphere was put intoapp. i., and app. 
ii. left filled with air. The results of an experiment in which 
the charge through air was divided and reduced by the shell- 
lac app. were as follows : 



396 


Specific inductive capacity . 


App. i. Lac. App. ii. Air. 

Balls 255°. 

0 ° . . . . 

.... 304° 


[Series XI. 


.... 297 
Charge divided. 

113 .... 

.... 121 

0 after being discharged. 

. . . . 7 after being discharged. 


1258. Here 297°, minus 7°, or 290°, may be taken as the 
divisible charge of app. ii. (the 7° being fixed stem action (1203. 
1232.)), of which 145° is the half. The lac. app. i. gave 113° as 
the power or tension it had acquired after division ; and the 
air app. ii. gave 121°, minus 7°, or 114°, as the force it pos- 
sessed from what it retained of the divisible charge of 290°. 
These two numbers should evidently be alike, and they are 
very nearly so, indeed far within the errors of experiment and 
observation. . But these numbers differ very much from 145°, 
or the force which the half charge would have had if app. i. 
had contained air instead of shell -lac ; and it appears that whilst 
in the division the induction through the air has lost 176° of 
force, that through the lac has only gained 113°. 

1259. If this difference be assumed as depending entirely on 
the greater facility possessed by shell-lac of allowing or causing 
inductive action through its substance than that possessed by 
air, then this capacity for electric induction would be inversely 
as the respective loss and gain indicated above ; and assuming 
the capacity of the air apparatus as 1, that of the shell-lac ap- 
paratus would be or 1*55. 

1260. This extraordinary difference was so unexpected in 
its amount, as to excite the greatest suspicion of the general 
accuracy of: the experiment, though the perfect discharge of 
app. i. after the division, showed that the 113° had been taken 
and given up readily. It was evident that, if it really existed, 
it ought to produce corresponding effects in the reverse order ; 
and that when induction through shell-lac was converted into 
induction through air, the force or tension of the whole ought 
to be increased. The app. i. was therefore charged in the first 



397 


Nov. 1837.] Experiments with shell-lac. 

place, and its force divided with app. ii. The following were 
the results : 

pp. i. Lac. App- h. Air. 

.... 0° 

215° . . . . * 

204 . ^ 

Charge divided. 

.... 118 
118 ... . 

0 after being discharged. 

0 after being discharged. 

1261. Here 204° must be the utmost of the divisible charge. 
The app. i. and app. ii. present 1 18° as their respective forces ; 
both now much above the half of the first force, or 102°, whereas 
in the former case they were below it. The lac app. i. has lost 
only 80°, yet it has gi\cn to the air app. ii. 1 18°, so that the lac 
still appears mueh to surpass the air, the capacity of the lac 
app. i. to the air app. ii. being as 137 to 1. 

1262. The difference of 1*55 and 1’37 as the expression of 
the capacity for the induction of shell-lae seems considerable, 
but is in reality very admissible under the circumstances, for 
both are in error in contrary directions. Thus in the last ex- 
periment the charge fell from 215° to 201° by the joint effects 
of dissipation and absorption (1*192. 1250.), during the time 
which elapsed in the electrometer operations, between the ap- 
plications of the carrier ball required to give those two results. 
Nearly an equal time must have elapsed between the applica- 
tion of the carrier which gave the 204-° result, and the division 
of the charge between the two apparatus ; and as the fall in 
force progressively decreases in amount (1192.), if in this ease 
it be taken at 6° only, it will reduce the whole transferable 
charge at the time of division to 198° instead of 201° ; this 
diminishes the loss of the shell-lae charge to 80° instead of 86° ; 
and then the expression of specific capacity for it is increased, 
and, instead of 137, is 1*47 times that of air. 

1263. Applying the same correction to the former experiment 
in which air was first charged, the result is of the contrary kind. 
No shell-lac hemisphere was then in the apparatus, and there- 
fore the loss would be principally from dissipation, and not 



398 Specific inductive capacity. [Series XI. 


from absorption : hence it would be nearer to the degree of foss 
shown by the numbers 304° and 29 7°, and being assumed as 
6° would reduce the divisible charge to 284°. In that case the air 
would have lost 170°, and communicated only 113° to the shell- 
lac ; arid the relative specific capacity of the latter would ap- 
pear to be 1*50, which is very little indeed removed from 1*47, 
the expression given by the second experiment when corrected 
in the same way. 

1264. The shell-lac was then removed from app. i. and put 
into app. ii. and the experiments of division again made. I give 
the results, because I think the importance of the point justifies 
and even requires them. 


App. i. Air. App. ii* Lac. 

Balls 200°. 
.... 0 ° 
286° .... 

283 ... . 

Charge divided. 
.... 110 


109 


. . . . 0*25 after discharge. 

Trace .... after discharge. 

Here app. i. retained 109°, having lost 174° in communi- 
cating 110° to app. ii. ; and the capacity of the air app. is to the 
lac app., therefore, as 1 to 1*58. If the divided charge be cor- 
rected for an assumed loss of only 3°, being the amount of pre- 
vious loss in the same time, it will make the capacity of the 
shell-lac app. 1*55 only, 

1265. Then app. ii. was charged, and the charge divided 
thus : * 


App. i. x\ir, App. ii. Lac. 

0 ° . . . . 

.... 256° 

.... 251 

Charge divided. 

146 ... . 

.... 149 

a little .... after discharge. 

. . . * a little after discharge. 



399 


Nov. 1837.] Examination of shell-lac. 

Here app. i. acquired a charge of 146°, while app.ii, lost only 
102° in communicating that amount of force ; the capacities 
being, therefore, to each other as 1 to 1*43. If the whole trans- 
ferable charge be corrected for a loss of 4° previous to division, 
it gives the expression of J*49 for the capacity of the shell-lac 
apparatus. 

•1266. These four expressions of T47, T50, 1*55, and 119 
for the power of the shell-lac apparatus, through the different 
variations of the experiment, arc very near to each other ; the 
average is close upon 1*5, which may hereafter be used as the 
expression of the result. It is a very important result j and, 
showingfor this particular piece of shell-lac a decided superior- 
ity over air in allowing or causing the act of induction, it proved 
the growing necessity of a more close and rigid examination of 
the whole question. 

1267. The shell-lac was of the best quality, and had been 
carefully selected and cleaned ; but as the action of any con- 
ducting particles in it would tend, virtually, to diminish the 
quantity or thickness of the dielectric used, and produce effects 
as if the two inducing surfaces of the conductors in that ap- 
paratus were nearer together than in the one with air only, [ 
prepared another shell- lac hemisphere, of which the material 
had been dissolved in strong spirit of wine, the solution filtered, 
and then carefully evaporated. This is not an easy operation, 
for it is difficult to drive off the last portions of alcohol without 
injuring the lac by the heat applied; and unless they be dissi- 
pated, the substance left conducts too well to be used in these 
experiments. I prepared two hemispheres this way, one of 
them unexceptionable ; and with it I repeated the former ex- 
periments with all precautions. The results were exactly of 
the same kind ; the following expressions for the capacity of 
the shell-lac apparatus, whether it were app. i. or ii., being 
given directly by the experiments, 110, T50, 1*52, 1*51 ; the 
average of these and several others being very nearly 1*5. 

1268. As a final check upon the general conclusion, I then 
actually brought the surfaces of the air apparatus, correspond- 
ing to the place of the shell-lac in its apparatus, nearer together, 
by putting a metallic lining into the lower hemisphere of the one 
not containing the lac (1213.). The distance of the metal sur- 



400 Specific inductive capacity of lac . [Series XI. 

face from the carrier ball was in this way diminished from 0‘62 
of an inch to 0*435 of an inch, whilst the interval occupied 1, by 
the lac in the other apparatus remained 0*62 of an inch as 
before. Notwithstanding this change, the lac apparatus showed 
its former superiority ; and whether jt or the air apparatus was 
charged first, the capacity of the lac apparatus to the air ap- 
paratus was by the experimental results as 1*45 to 1. 

1269. From all the experiments I have made, and their con- 
stant results, I cannot resist the conclusion that shell-lac docs 
exhibit a case of specific inductive capacity . I have tried to 
check the trials in every way, and if not remove, at least estimate, 
every source of error. That the final result is not due to com- 
mon conduction is shown by the capability of the apparatus to 
retain the communicated charge ; that it is not due to the con- 
ductive power of inclosed small particles, by which they could 
acquire a polarized condition as conductors, is shown by the 
effects of the shell -lac purified by alcohol ; and, that it is not 
due to any influence of the charged state, formerly described 
(1250.), first absorbing and then evolving electricity, is indica- 
ted by the instantaneous assumption and discharge of those 
portions of the power which are concerned in the phenomena, 
that instantaneous effect occurring in these cases, as in all others 
of ordinary induction by charged conductors. The latter ar- 
gument is the more striking in the case where the air apparatus 
is employed to divide the charge with the lac apparatus, for it 
obtains its portion of electricity in an instant , and yet is charged 
far above the mean . 

1270. Admitting for the present the general fact sought to 
be proved; then 1*5, though it expresses the capacity of the 
apparatus containing the hemisphere of shell-lac, by no means 
expresses # the relation of lac to air. The lac only occupies one 
half of the space o* o, of the apparatus containing it, through 
which the induction is sustained ; the rest is filled with air, as 
in the other apparatus ; and if the effect of the two upper 
halves of the globes be abstracted, then the comparison of the 
shell-lac powers in the lower half of the one, with the power of 
the air in the lower half of the other, will be as 2 : 1; and even 
this must be less than the truth, for the induction of the upper 
part of the apparatus, i. e. of the wire and ball B. (fig. 104.) to 



401 


Nov. 1837.] Specific inductive capacity of glass. 

external objects, must be tbe same in both, and considerably 
diminish the difference dependent upon, and really producible 
by, the influence of the shell-lac within. 

1271. Glass . — I next worked with glass at the dielectric. 
It involved the possibility of conduction on its surface, but it 
excluded the idea of conducting particles within its substance 
(1207.) other than those of its own mass. Besides this it does 
not assume the charged state (1239.) so readily, or to such an 
extent as shell-lac. 

1272. A thin hemispherical cup of glass being made hot was 
covered with a coat of shcll-lae dissolved in alcohol, and after 
being dried for many hours in a hot place, was put into the 
apparatus and experimented with. It exhibited effects so 
slight, that, though they were in the direction indicating a 
superiority of glass over air, they were allowed to pass as pos- 
sible errors of experiment ; and the glass was considered as 
producing no sensible effect. 

1273. 1 then procured a thick hemispherical (lint glass cup 
resembling that of shcll-lae (1239.), but not filling up the space 
o, o, so well. Its average thickness was 0 1- of an inch, there 
being an additional thickness of air, averaging 0 22 of an inch 
to make up the whole space of 0*02 of an inch between the 
inductive metallic surfaces. It. was covered with a film 
of shell-lac as the former was, (1272.) and being made very 
warm, w^as introduced into the apparatus, also warmed, and 
experiments made with it as in the former instances (1257. &e.). 
The general rcstdts were the same as with shell -lac, i. c. glass 
surpassed air in its power of favouring induction through it. 
The two best results as respected the state of the apparatus 
for retention of charge, &e., gave, when the air apparatus was 
charged first 1*336, and when the glass apparatus was charged 
first 1;45, as the specific inductive capacity for glass, both being 
without correction. The average of nine results, four with 
the glass apparatus first charged, and five with the air appa- 
ratus first charged, gave 1*38 as the power of the glass appa- 
ratus ; 1*22 and 1*46 being the minimum and maximum num- 
bers with all the errors of experiment upon them. In all, the 
experiments the* glass apparatus took up its inductive charge 
instantly* and lost it as readily (1269.) ; and during the short 

2 n 



403 Specific inductive capacity . [Series XI. 

time of each experiment, acquired the peculiar state in a small 
tlegree only, so that the influence of this state, and also of 
conduction upon the results, must have been small. 

1274. Allowing specific inductive capacity to be proved and 
active in this case, and 1*38 as the expression for the glass 
apparatus, then the specific inductive capacity of flint glass 
will be above 1*76, not forgetting that this expression is for a 
piece of glass of such thickness as to occupy not quite two- 
thirds of the space through which the induction is sustained 

(1273. 1253.). 

1275. Sulphur . — The same hemisphere of this substance was 
used in app. ii. as was formerly referred to (1242.) . The experi- 
ments were well made, i. e. the sulphur itself was free from charge 
both before and after each experiment, and no action from the 
stem appeared (1203. 1232.), so that no correction was required 
on that account. The following are the results when the air- 
apparatus was first charged and divided : 

App. i. Air. App. ii. Sulphur. 

Balls 280°. 


0° . . 

0° 

438 . . 

• 

431 . . 

fl 

Charge 

divided. 

, . 

. 162 

164 . . 

. 160 

162 . . 

. 0 after discharge. 

0 ' . . 

. after discharge. 


Here app. i. retained 164°, having lost 270° in communicating 
162° to app. ii., and the capacity of the air apparatus is to that 
of the sulphur apparatus as 1 to 1*66. 

1276. Then the sulphur apparatus was charged first, thus : 

.... 0 ° 


0 C 


395 

388 



403 


Nov. 1,837.] Inductive capacity of sulphur . 

Charge divided, 

237 .... 

.... 238 

0 . after discharge. 

. . . .• 0 after discharge. 

Here app. ii. retained 238°, and gave up 150° in communi- 
cating a charge of 237° to app. i., and the capacity of the air 
apparatus is to that of the sulphur apparatus as 1 to 1-38. Those 
results are very near to each other, and we may take the moan 
1*02 as representing the specific inductive capacity of the sul- 
phur apparatus : in which case the specific inductive capacity 
of sulphur itself as compared to air = 1 (1270.) will be about 
or above 2 24. 

1277. This result with sulphur I consider as one of the most 
unexceptionable. The substance when fused was perfectly 
clear, pellucid, and free from particles of dirt (1207.), so that 
no interference of small conducting bodies confused the result. 
The substance when solid is an excellent insulator, and by 
experiment was found to take up, with great slowness, that 
state (1211. 1212.) which alone seemed likely to disturb tin; 
conclusion. The experiments themselves, also, were free from 
any need of correction. Yet notwithstanding these circum- 
stances, so favourable to the exclusion of error, the result is a 
higher specific inductive capacity for sulphur than for any other 
body as yet tried ; and though this may in part ho due to the 
sulphur being in a better shape, i. e. filling up more completely 
the space o, o, (fig. 101.) than the cups of slicli-lae and glass, 
still I feel satisfied that the experiments altogether fully prove 
the existence of a difference between dielectrics as to their power 
of favouring an inductive action through them; which, differ- 
ence may, for the present, be expressed by the term specific 
inductive capacity , 

1278. Having thus established the point in the most favour- 
able cases that I could anticipate, I proceeded to examine other 
bodies amongst solids, liquids, and gases. These results I shall 
give with all convenient brevity. 

1279. Spermaceti. — A good hemisphere of spermaceti being 
tried as to conducting power whilst its two surfaces were still 
in contact with the tinfoil moulds used in forming it, was 

2 n 2 



404 Specific inductive capacity . [Series XI. 

found to conduct sensibly even whilst warm. On removing it 
from the moulds and using it in one of the apparatus, it gave 
results indicating a specific inductive capacity between V3 and 
1*6 for the apparatus containing it. But as the only mode of 
operation was to charge the air app^atus, and then after a quick 
contact with the spermaceti apparatus, ascertain what was left 
in the former (1281.), no great confidence can be placed in the 
results. They are not in opposition to the general conclusion, 
but cannot be brought forward as argument in favour of it. 

1280. I endeavoured to find some liquids which would insu- 
late well, and could be obtained in sufficient quantity for these 
experiments. Oil of turpentine, native naphtha rectified, and 
the condensed oil gas fluid, appeared by common experiments 
to promise best as to insulation. Being left in contact with 
fused carbonate of potassa, chloride of lime, and quick lime 
for some days and then filtered, they were found much 
injured in insulating power ; but after distillation acquired 
their best state, though even then they proved to be conductors 
when extensive metallic contact was made with them. 

1281. Oil of turpentine rectified. — I filled the lower half of 
app. i. with the fluid : and as it would not hold a charge suffi- 
ciently to enable me first to measure and then divide it, I 
charged app. ii. containing air, and dividing its charge with 
app. i. by a quick contact, measured that remaining in app. ii. : 
for, theoretically, if a quick contact would divide up to equal 
tension between the two apparatus, yet without sensible loss 
from the conducting power of app. i. ; and app. ii. were left 
charged to a degree of tension above half the original charge, 
it would indicate that oil of turpentine had less specific induc- 
tive capacity thau air ; or, if left charged below that mean state 
of tension, it would imply that the fluid had the greater induc- 
tive capacity. In an experiment of this kind, app. ii. gave as 
its charge 390° before division with app. i., and 175 after- 
wards, which is less than the half of 890°. Again, being at 
175° before division, it was 79° after, which i's also less than 
half the divided charge. Being at 79°, it was a third time 
divided, and then fell to 36°, less than the half of 79°. Such 
are the best results I could obtain ; they are not inconsistent 
with the belief that oil of turpentine has a greater specific 



Air, rare and dense. 


405 


Nov. 1837.] 

capacity than air, but they do not prove the fact, since the dis- 
appearance of more than half the charge may be due to the 
conducting power merely of the fluid. 

3282. Naphtha . — This liquid gave results similar in their 
nature and direction to those with oil of turpentine. 


1283. A most interesting class of substances, in relation to 
specific inductive capacity, now came under review, namely, 
the gases or aeriform bodies. These are so peculiarly consti- 
tuted, and are bound together by so many striking physical 
and chemical relations, that I expected some remarkable results 
from them : air in various states was selected for the first expe- 
riments. 

1281. Air , rare and dense . — Some experiments of division 
(1208.) seemed to show that dense and rare air were alike in the 
property under examination. A. simple and better process 
was to attach one of the apparatus to an air pump, to charge 
it, and then examine the tension of the charge when the air 
within was more or less rarefied. Under these circumstances 
it was found, that commencing with a certain charge, that 
charge did not change in its tension or force as the air was rare- 
fied, until the rarefaction was such that discharge across the 
space o, o (fig. 101.) occurred. This discharge was proportionate 
to the rarefaction ; but having taken place, and lowered the 
tension to a certain degree, that degree was not at all affected 
by restoring the pressure and density of the air to their first 
quantities. 


* inches of mercury. 

Thus at a pressure of 30 the charge was . 

Again 3Q the charge was . 

Again 30 the charge was . . 

Reduced to .... 14 the charge was . 

Raised again to . . 30 the charge was . 

Being now reduced to 3*4 the charge fell to. 
Raised again to . . 30 the charge was still 


88 ° 

88 

87 

87 

8G 

81 

81 


1285. The charges were low in these experiments, first that 
they might not pass off at low pressure, and next that little 
loss by dissipation might occur. I now reduced them still 
lower, that X might rarefy further, and for this purpose in the 



406 Specific inductive capacity. [Series XI. 

following experiment used a measuring interval in the electro- 
meter of only 15° (1185.). The pressure of air within the appa- 
ratus being reduced to 1*9 inches of mercury, the charge was 
found to be 29°; then letting in air till the pressure was 30 inches, 
the charge was still 29°. 

1286. These experiments were repeated with pure oxygen 
with the same consequences. 

1287. This result of no variation in the electric tension being 
produced by variation in the density or pressure of the air agrees 
perfectly with those obtained by Mr. Harris*, and described in 
his beautiful and important investigations contained in the Phi- 
losophical Transactions ; namely that induction is the same in 
rare and dense air, and that the divergence of an electrometer 
under such variations of the air continues the same, provided 
no electricity pass away from it. The effect is one entirely in- 
dependent of that power which dense air has of causing a higher 
charge to be retained upon the surface of conductors in it than 
can be retained by the same conductors in rare air; a point I 
propose considering hereafter. 

1288. I then compared hot and cold air together, by raising 
the temperature of one of the inductive apparatus as high as 
it could be without injury, and then dividing charges between 
it and the other apparatus containing cold air. The tempera- 
tures were about 50° and 200°. Still the power or capacity 
appeared to be unchanged ; and when I endeavoured to vary the 
experiment, by charging a cold apparatus and then warming it 
by a spirit lamp, I could obtain no proof that the inductive 
capacity underwent any alteration. 

1289. I compared damp and dry air together, but could find 
no difference in the results. 

1290. Gases . — A very long series of experiments was then 
undertaken for the purpose of comparing different gases one 
with another. They were all found to insulate well, except such 
as acted on the shell-lac off the supporting stem ; these were 
chlorine, ammonia, and muriatic acid. They Were all dried by 
appropriate means before being introduced into the apparatus. 
It would have been sufficient to have compared each with air ; 
but, in consequence of the striking result which came out, 

* Philosophical Transactions, 1834, pp.-223, 224, 237, 244. 



Gases ; — all alike . 


Nov. 1837.] 


407 


namely, that all had the same power of or caj)acity for, sustain, 
ing induction through them, (which perhaps might have been 
expected after it was found that no variation of density or pres, 
sure produced any effect,) I was induced to compare them, 
experimentally, two and fr^o in various ways, that no difference 
might escape me, and that the sameness of result might stand 
in full opposition to the contrast of property, composition, and 
condition which the gases themselves presented. 

1291. The experiments were made upon the following pairs of 
gases. 


1. Nitrogen and . 


Oxygen, 

2. Oxygen . 


Air. 

3. Hydrogen . , 


Air. 

4. Muriatic acid gas 


Air. 

5. Oxygen . . . 


Hydrogen. 

6. Oxygen . . . 


Carbonic acid. 

7. Oxygen . 


Olcliant gas. 

8. Oxygen . . . 

• 

Nitrons gas. 

9. Oxygen . . . 


Sulphurous acid. 

10. Oxygen . . . 


Ammonia. 

11. Hydrogen . . 


Carbonic acid. 

12. Hydrogen . . 


Olefiant gas. 

13. Hydrogen . . 


Sulphurous acid. 

14. Hydrogen 

• * 

Fluo-silicie acid. 

15. Hydrogen . . 


Ammonia. 

16. Hydrogen 


Arsenin ret ted hydrogen. 

17. Hydrogen . . 


Sulphuretted hydrogen. 

18/ Nitrogen . . . 


Olefiant gas. 

19. Nitrogen . . . 


Nitrous gas. 

20. Nitrogen . . . 


Nitrous oxide. 

21. Nitrogen . • . 


Ammonia. 

22. Carbonic oxide . 


Carbonic acid. 

23. Carbonic oxide . 


Olefiant gas. 

2 k Nitrous oxide . 


Nitrous gas. 

25. Ammonia. . . 


Sulphurous acid. 


1292. Notwithstanding the striking contrasts of all kinds 
which these gases present of property, of density, whether 
simple or compound, anions or cathions (665.), of high or low 
pressure (1284. 1286.) r hot or cold (1288.), not the least differ- 



408 Inductive capacity of gases alike . [Series XI. 

ence in their capacity to favour or admit electrical induction 
through them could be perceived. Considering the point esta- 
blished, that in all these gases induction takes place by an ac- 
tion of contiguous particles, this is the more important, and adds 
one to the many striking relations yhich hold between bodies 
having the gaseous condition and form. Another equally im- 
portant electrical relation, which will be examined in the next 
paper*, is that which the different gases have to each other at 
the same pressure of causing the retention of the same or differ- 
ent degrees of charge upon conductors in them. These two 
results appear to bear importantly upon the subject of electro- 
chemical excitation and decomposition ; for as all these pheno- 
mena, different as they seem to be, must depend upon the elec- 
trical forces of the particles of matter, the very distance at 
which they seem to stand from each other will do much, if pro- 
perly considered, to illustrate the principle by which they are 
held in one common bond, and subject, as they must be, to one 
common law. 

1293. It is just possible that the gases may differ from each 
other in their specific inductive capacity, and yet by quantities 
so small as not to be distinguished in the apparatus I have 
used. It must be remembered, however, that in the gaseous ex- 
periments the gases occupy all the space o , o, (fig. 101.) between 
the inner and the outer ball, except the small portion filled by 
the stem ; and the results, therefore, are twice as delicate as 
those with solid dielectrics. 

1294. The insulation was good in all the experiments re- 
corded, except Nos. 10, 15, 21, and 25, being those in which 
ammonia was compared with other gases. When shell -lac is 
put into ammoniacal gas its surface gradually acquires conduct- 
ing powt^r, and in this way the lac part of the stem within was 
so altered, that the ammonia apparatus could not retain a charge 
with sufficient steadiness to allow of division. In these expe- 
riments, therefore, the other apparatus was charged ; its charge 
measured and divided with the ammonia apparatus by a quick 
contact, and what remained untaken away by the division again 
measured (1281.). It was so nearly one half of the original 
charge, as to authorize, with this reservation, the insertion of 

* See in relation to this point 1382, &e,— Dec. 1888. 



Nov. 1837.] General view of induction . 409 

ammoniacal gas amongst the other gases, as having equal power 
with them. 

% vi. General results as to induction . 

1295. Thus induction appears to be essentially an action of 
contiguous particles, through the intermediation of which the 
electric force, originating or appearing at a certain place, is 
propagated to or sustained at a distance, appearing there as a 
force of the same kind exactly equal in amount, but opposite in 
its direction and tendencies (1101.). Induction requires no 
sensible thickness in the conductors which may be used to limit 
its extent ; an uninsulated leaf of gold may be made very highly 
positive on one surface, and as highly negative on the other, 
without the least interference of the two states whilst the in- 
ductions continue. Nor is it affected by the nature of the 
limiting conductors, provided time be allowed, in the ease of 
those which conduct slowly, for them to assume their final state 
(H70.). ' 

1296. But with regard to the dielectrics or insulating media, 
matters are very different (1167.). Their thickness lias an im- 
mediate and important influence on the degree of induction. 
As to their quality, though all gases and vapours arc alike, 
whatever their state ; yet amongst solid bodies, and between 
them and gases, there are differences which prove the exist- 
ence of specific inductive capacitkfs, these differences being in 
some cases very great. 

1297. The direct inductive force, which may he conceived to 
be exerted in lines between the two limiting and charged con- 
ducting surfaces, is accompanied by a lateral or transverse force 
equivalent to a dilatation or repulsion of these representative 
lines (1224.) j or the attractive force which exists amongst the 
particles of the dielectric in the direction of the induction is ac- 
companied by a repulsive or a diverging force in the trans- 
verse direction (1304.). 

1298. Induction appears to consist in a certain polarized state 
of the particles, into which they are thrown by the electrified 
body sustaining the action, the particles assuming positive and 
negative points Or parts, which are symmetrically arranged with 
respect to each other and the inducting surfaces or particles*. 

# The theory of induction which I am stating does not pretend to decide 



410 General view of induction . [Series XI, 

The state must be a forced one, for it is originated and sus- 
tained only by force, and sinks to the normal or quiescent state 
when that force is removed. It can be continued only in insu- 
lators by the same portion of electricity, because they only can 
retain this state of the particles (1304.). 

1299. The principle of induction is of the utmost generality 
in electric action. It constitutes charge in every ordinary case, 
and probably in every case ; it appears to be the cause of all 
excitement, and to precede every current. The degree to 
which the particles are affected in this their forced state, be- 
fore discharge of one kind or another supervenes, appears to 
constitute what we call intensity . 

1300. When a Leyden jar is charged, the particles of the 
glass are forced into this polarized ^nd constrained condition 
by the electricity of the charging apparatus. Discharge is the 
return of these particles to their natural state from their state 
of tension, whenever the two electric forces arc allowed to be 
disposed of in some other direction. 

1301. All charge of conductors is on their surface, because 
being essentially inductive, it is there only that the medium 
capable of sustaining the necessary inductive state begins. If 
the conductors arc hollow and contain air or any other dielec- 
tric, still no charge can appear upon that internal surface, be- 
cause the dielectric there cannot assume the polarized state 
throughout, in consequence of the opposing actions in different 
directions. 

1302. The known influence of form is perfectly consistent 
with the corpuscular view of induction set forth. An electri- 
fied cylinder is more affected by the influence of the surround- 
ing conductors (which complete the condition of eharge) at the 
ends than at the middle, because the ends are exposed to a 
greater sum of inductive forces than the middle y and a point 
is brought to a higher condition than a ball, because by rela- 
tion to the conductors around, more inductive force terminates 
on its surface than on an equal surface of the ball with which 
it is compared. Here, too, especially, ean be perceived the in- 
fluence of the lateral or transverse force* (1297^ which, 

whether electricity be a fluid or fluids, or a mere pow§r ^fe^pditioa of recog- 
nized matter. That is a question' which I may consider in the 

next or following series of these researches, s 



Ill 


Nov. 1837.] General view of induction* 

a power of the nature of or equivalent to repulsion, causes such 
a disposition of the lines of inductive force in their course across 
the dielectric, that they must accumulate upon the point, the 
end of the cylinder, or any projecting part. 

1303. The influence of distance is also in harmony with the 
same view. There is perhaps no distance so great that induc- 
tion cannot take place through it* ; hut with the same con- 
straining force (1298.) it takes place the more easily, according 
as the extent of dielectric through which it is exerted is less- 
ened. And as it is assumed by the theory that the particles of 
the dielectric, though tending to remain in a normal state, arc 
thrown into a forced condition during the induction ; so it 
would seem to follow that the fewer there are of these inter- 
vening particles opposing their tendency to the assumption of 
the new state, the greater degree of change will they suffer, 
i. e. the higher will be the condition they assume, and the 
larger the amount of inductive action exerted through them. 

1304. I have used the phrases tines of inductive force and 
curved lines of force (1231. 1297. 1298. 1302.) in a general 
sense only, just as we speak of the lines of magnet ie force. 
The lines arc imaginary, and the force' in any part of them is 
of course the resultant of compound forces, every molecule be- 
ing related to every other molecule in all directions by the 
tension and reaction of those which arc contiguous. The 
transverse force is merely this relation considered in a direction 
oblique to the lines of inductive force, and at present 1 mum 
no more than that by the phrase. With respect to the term 
polarity also, I mean at present only a disposition of force by 
which the same molecule acquires opposite powers on di Horen t 
parts. The particular way in which this disposition is made 
will eome into consideration hereafter, and probably varies in 
different bodies, and so produces variety of electrical re- 
lationf , All I am anxious about at present is, that a more par- 
ticular meaning should not be attached to the expressions used 

♦ I have traced it experimentally from a ball placed in the middle of tlm 
large cube formerly described (1173.) to the sides of the cube six feet distant, 
add also from the earn? ball placed in the middle of our large lecture- room to 
the walls bf the room at twenty-six feet distance, the charge sustained upon 
the ball in these cases being solely due to induction through these distances, 

,t See now im, tkc.—Dcc. W 



412 General view of induction . [Series XI. 

than I contemplate. Further inquiry, I trust, will enable us 
by degrees to restrict the sense more and more, and so render 
the explanation of electrical phenomena day by day more and 
more definite. 

1305. As a test of the probable accuracy of my views, I have 
throughout this experimental examination compared them with 
the conclusions drawn by M. Poisson from his beautiful mathe- 
matical inquiries*. I am quite unfit to form a judgment of 
these admirable papers ; but as far as I can perceive, the 
theory I have set fortli and the results I have obtained are not 
in opposition to such of those conclusions as represent the 
final disposition and state of the forces in the limited number 
of cases he has considered. His theory assumes a very diff- 
erent mode of action in induction to that which I have ven- 
tured to support, and would probably find its mathematical 
test in the endeavour to apply it to cases of induction in curved 
lines. To my feeling it is insufficient in accounting for the re- 
tention of electricity upon the surface of conductors by the 
pressure of the air, an effect which I hope to show is simple 
and consistent according to the present viewf ; and it docs 
not touch voltaic electricity, or in any way associate it and 
what is called ordinary electricity under one common prin- 
ciple, 

I have also looked with some anxiety to the results which 
that indefatigable philosopher Harris has obtained in his in- 
vestigation of the laws of induction^, knowing that they were 
experimental, and having a full conviction of their exactness ; 
but I am happy in perceiving no collision at present between 
them and the views I have taken. 

1306. Finally, I beg to say that I put forth my particular 
view with doubt and fear, lest it should not bear the test of 
general examination, for unless true it will only embarrass the 
progress of electrical science. It has long been on my mind, 
but I hesitated to publish it until the increasing persuasion of 
its accordance with all known facts, and the manner in which 
it linked together effects apparently very different in kind, 

* M&noires de l’lnstitut, 1811, tom. xii. the first page 1, and the “second 
paging 163. 

t Refer to 1377, 1378, 1379, 1398.— Dec. 1838. 

% Philosophical Transactions, 1834, p. 213. , 



March 1838.] Differential inductometer * 413 

urged me to write the present paper. I as yet see no incon- 
sistency between it and nature, but, on the contrary, think I 
perceive much new light throw n by it on her operations ; and 
my next papers will be devoted to a review of the phenomena 
of conduction, electrolyzation, current, magnetism, retention, 
discharge, and some other points, with an application of the 
theory to these effects, and an examination of it by them. 

Royal Institution , 

November 16, 1837. 


Supplementary Note to Experimental Researches in Electricity. 

Eleventh Series . 

Received March 20, 

1307. I have recently put into an experimental form that 
general statement of the question of specific inductive capacity 
which is given at No. 1262 of Series XL, and the result is such 
as to lead me to hope the Council of tin* lloyal Society will au- 
thorize its addition to the paper in the form of a supplementary 
note. Three circular brass plates, about five inches m di- 
ameter, were mounted side by side upon insulating pillars ; the 
middle one. A, was a fixture, but ‘the outer plates 33 and C wore 
moveable on slides, so that all three could be brought with 
their sides almost into contact, or separated to any required di- 
stance. Two gold leaves were suspended in a glass jar from 
insulated wires ; one of the outer plates 31 was connected with 
one of the gold leaves, and the other outer plate with the other 
leaf. The outer plates R and C were adjusted at the distance 
of an inch and a quarter from the middle plate A, and the 
gold leaves were fixed at two inches apart ; A was then slightly 
charged with electricity, and the plates 33 and C, with their 
gold leaves, thrown out of insulation at the same time, and then 
left insulated. In this state of things A was charged positive 
induetrically, and B and C negative induct eously ; the same 
dielectric, air, being in the two intervals, and the gold leaves 
hanging, of course, parallel to each other in a relatively un- 
eleetrified state* 



414 Specific inductive capacity. [Series XI. 

1308. A plate of shell -lac three quarters of an inch in thick- 
ness, and four inches square, suspended by clean white silk 
thread, was very carefully deprived of all charge (1203.) (so 
that it produced no effect on the gold leaves if A were un- 
charged) and then introduced between plates A and B ; the 
electric relation of the three plates was immediately altered, 
and the gold leaves attracted each other. On removing the 
shell-lac this attraction ceased ; on introducing it between A 
and C it was renewed ; on removing it the attraction again 
ceased ; and the shell -lac when examined by a delicate Coulomb 
electrometer was still without charge. 

1309. As A was positive, B and C were of course negative ; 
but as the specific inductive capacity of shell-lac is about twice 
that of air (1270.), it was expected that when the lac was in- 
troduced between A and B, A would induce more towards B 
than towards C ; that therefore B would become more negative 
than before towards A, and, consequently, because of its insu- 
lated condition, be positive externally, as at its back or at the 
gold leaves ; whilst C would be less negative towards A, and 
therefore negative outwards or at the gold leaves. This was 
found to be the case ; for on whichever side of A the shell-lac 
was introduced the external plate at that side was positive, and 
the external plate on the other side negative towards each 
other, and also to uninsulated external bodies. 

1310. On employing a plate of sulphur instead of shell-lac, 
the same results were obtained ; consistent with the conclusions 
drawn regarding the high specific inductive capacity of that 
body already given (1270.). 

1311. These effects of specific inductive capacity can be 
exalted in various ways, and it is this capability which makes 
the great value of the apparatus. Thus I introduced the shell- 
lac between A and* B, and then for a moment connected B and 
C, uninsulated them, and finally left them in the insulated state ; 
the gold leaves were of course hanging parallel to each other. 
On removing the shell-lac the gold leaves attracted each other ; - 
on introducing the shell-lac between A and C this attraction 
was increased , (as had been anticipated from theory,) and the 
leaves came together, though not more than four inches Jbng, 
and hanging threo inches apart. 

1312. By simply bringing the gold leaves other 



March 1838. J Differential inductometer . 415 

I was able to show the difference of specific inductive capacity 
when only thin plates of shell-lac were used, the rest of the 
dielectric space being filled with air. By bringing B and C 
nearer to A another great increase of sensibility was made. 
By enlarging the size of # the plates still further power was 
gained. By diminishing the extent of the wires, &e. connected 
with the gold leaves, another improvement resulted. So that 
in fact the gold leaves became, in this manner, as delicate a 
test of specific inductive action as they are, in Bennetts and 
Singer's electrometers, of ordinary electrical charge. 

1313. It is evident that by making the three plates the sides 
of cells, with proper precautions as regards insulation, &i\, 
this apparatus may he used in tlie examination, of gases, with 
far more effect than the jfbnncr apparatus (1187. 1290.), alul 
may, perhaps, bring out differences which have as yet escaped 
me (1292. 1293.). 

1314. It is also evident that two metal plates are quite suffi- 
cient to form the instrument ; the state of the single indueteous 
plate when the dielectric is changed, being examined either by 
bringing a body excited in a known manner towards its gold 
leaves, or, what I think will be better, employing a carrier ball 
in place of the leaf, and examining that ball by the Coulomb 
electrometer (1180.). The inductive and indueteous surfaces 
may even be balls ; the hitter being itself the* carrier ball of the 
Coulomb's electrometer (1181. 1229.). 

1315. To increase the effect, a small condenser may be used 
with great advantage. Thus if, when two indueteous plates 
are tised, a little condenser were put in the place of the gold 
leaves, I have no doubt the three principal plates might he re- 
duced to an inch or even half an inch in diameter. Kvcu the 
gold leaves act to each other for the time as the plates of a con- 
denser. If only two plates were used, by the proper applica- 
tion of the condenser the same reduction might take place. 
This expectation is fully justified by an effect already observed 
and described ( 1 229.) . 

1316. In that case the application of the instrument to very 
■extensive research is evident. Comparatively small masses of 
dielectrics could be examined, as diamonds and crystals. An 
expectation, that the specific inductive capacity of crystals will 
vary in different directions, according as the lines of inductive 



416 Differential inductometer. [Series XI. 

force (1304.) are parallel to, or in other positions in relation to 
the axes of the crystals, can be tested* : I purpose that these 
and many other thoughts which arise respecting specific in- 
ductive action^ and the polarity of the particles of dielectric 
matter, shall he put to the proof a>% soon as I can find time. 

1317'. Hoping that this apparatus will form an instrument of 
considerable use, I beg to propose for it (at the suggestion of 
a friend) the name of Differential Inductometer . 

Royal Institution, 

March 29, 1838. 

* liefer for this investigation to 1089 — 1698. — Dec. 1838.' 



417 


TWELFTH SERIES. 

§ 18. On Induction (continued ) . vii. Conduction , or conduct- 

ive discharge. If viii. Electrolytic discharge. If ix. Dis- 
ruptive discharge — Insulation — Spark — Brush — Difference of 
discharge at the positive and negative surfaces of con- 
ductors. 

Received January 11, — Read February 8, 18;K 

1318. I proceed now, according to my promise, to examine, 
by the great facts of electrical science, that theory of induc- 
tion which I have ventured to put forth (1105. 1,295. &e.). 
The principle of induction is so universal that it pervades all 
eleetrical phenomena; but the general ease which 1 purpose at 
present to go into consists of insulation traced into and termi- 
nating with discharge, with the accompanying effects. This 
ease includes the various modes of discharge, and also the 
condition and characters of a current ; the elements of mag- 
netic action being amongst the latter. I shall necessarily ha\c 
occasion to speak theoretically, and even hypothetically ; and 
though these papers profess to be, experimental researches, l 
hope that, considering the facts and investigations contained 
in the last scries in support of tin' particular view advanced, L 
shall not be Considered as taking too much liberty on tins pre- 
sent occasion, or as departing too far from the character which 
they ought to have, especially as I shall use every opportunity 
which presents itself of returning to that strong test of truth, 
experiment. 

1319. Induction has as yet been considered in these papers 
only in cases of insulation ; opposed to insulation is discharge . 
The action 'or effect which may be expressed by the general 
term discharge , may take place, as far as we are aware at pre- 
sent, in several modes. Thus, that which is called simply 
conduction involves no chemical action, and apparently no 
displacement of the particles concerned. A second mode may 

2 E 



418 Induction and conduction . [Series XIL 

be called electrolytic discharge ; in it chemical action does 
occur, and particles must, to a certain degree, be displaced. 
A third mode, namely, that by sparks or brushes, may, be- 
cause of its violent displacement of the particles of the 
dielectric in its course, be called the disruptive discharge ; 
and a fourth may, perhaps, be conveniently distinguished for a 
time by the words convection , or carrying discharge , being 
that in which discharge is effected either by the carrying 
power of solid particles, or those of gases and liquids. Here- 
after, perhaps, all these modes may appear as the result of 
one common principle, but at present they require to be con- 
sidered apart ; and I will now speak of the first mode, for 
amongst all the forms of discharge that which wc express by 
the term conduction appears the most simple and the most 
directly in contrast with insulation. 

If vii. Conduction , or conductive discharge . 

1320. Though assumed to be essentially different, yet nei- 
ther Cavendish nor Poisson attempt to explain by, or even 
state in, their theories, what the essential difference between 
insulation and conduction is. Nor have I anything, perhaps, 
to offer in this respect, except that, according to my view of in- 
duction, insulation and conduction depend upon the same mole- 
cular action of the dielectrics concerned ; are only extreme de- 
grees of one common condition or effect ; and in any sufficient 
mathematical theory of electricity mu„st be takej^ as cases of 
the same kind. Hence the importance of the endeavour to 
show the connection between them under my theory of the 
electrical relations of contiguous particles. 

1321. Though the action of the insulating dielectric in the 
charged Leyden jar, and that of the wire in discharging it, 
may seem very different, they may be associated by numerous 
intermediate links, which carry us on from one to the other, 
leaving, I think, no necessary connection un supplied. We 
may observe some of these in succession for information re- 
specting the whole case. 

1322. Spermaceti has been examined and found to be a di- 
electric, through which induction can take place (1240. 1246.), 



Jan. 1838.] All bodies are conductors. 419 

its specific inductive capacity being about or above 1*8 (1279.), 
ancf the inductive action has been considered in it, as in all 
other substances, an action of contiguous particles. 

1323, But spermaceti is also a conductor , though in so low 
a degree that we can trace the process of conduction, as it 
were, step by step through the mass (1247.) ; and even when 
the electric force has travelled through it to a certain dis- 
tance, we can, by removing the coereitive (which is at the same 
time the inductive) force, cause it to return upon its path and 
reappear in its first place (1245. 1246.). Here induction ap- 
pears to be a necessary .preliminary to conduction. It of itself 
brings the contiguous particles of the dielectric into a certain 
condition, which, if retained by them, constitutes insulation , 
but if lowered by the communication of power from one parti- 
cle to another', constitutes conduction . 

1324. If glass or shell-lac be the substances under consi- 
deration, the same capabilities of suffering cither induction 
or conduction through them appear (1233. 1239. 1247.), but 
not in the same degree. The conduction almost disappears 
(1239. 1242.) ; the induction therefore is sustained, i. e. the 
polarized state into which the inductive force has brought the 
contiguous particles is retained, there being little discharge 
action between them, and therefore the insulation continues. 
But, what discharge there is, appears to be consequent upon 
that condition of the particles into which the induction throws 
them ; and thus it is that ordinary insulation and conduction 
are closely tjftsociatcd together or rather are extreme cases of 
one common condition. 

1325* In ice or water we have a better conductor than sper- 
maceti, and the phenomena of induction and insulation there- 
fore rapidly disappear, because conduction quickly follows upon 
the assumption of the inductive state. But let a plate of cold 
ice have metallic coatings on its sides, and connect one of these 
with a good electrical machine in work, and the other with the 
groOnd, and it then becomes easy to observe the phenomena of 
induction through the ice, by the electrical tension which can 
be obtained and continued on both the coatings (419. 426.). 
Por although that portion of power which at one moment gave 
the inductive condition to the particles is at the next lowered 
by the consequent discharge due to the conductive act, it is 

2 e 2 



420 Insulation and conduction alike . [Series XII. 

succeeded by another portion of force from the machine to 
restore the inductive state. If the ice be converted into water 
the same succession of actions can be just as easily proved, 
provided the water be distilled, and (if the machine be not 
powerful enough) a voltaic battery fee employed. 

1326. All these considerations impress my -mind strongly 
with the conviction, that insulation and ordinary conduction 
cannot be properly separated when we are examining into 
their nature ; that is, into the general law or laws under 
which their phenomena are produced. They appear to me to 
consist in an action of contiguous particles dependent on the 
forces developed in electrical excitement; these forces bring 
the particles into a state of tension or polarity, which con- 
stitutes both induction and insulation ; and being in this state, 
the continuous particles have a power or capability of commu- 
nicating their forces one to the other, by which they are 
lowered, and discharge occurs. Every body appears to dis- 
charge (444. 987.) ; but the possession of this capability in a 
greater or smaller degree in different bodies, makes them 
better or worse conductors, worse or better insulators; and 
both induction and conduction appear to be the same in their 
principle and action (1320.), except that in the latter an effect 
common to both is raised to the highest degree, whereas 
in the former it occurs in the best cases, in only an almost 
insensible quantity. 

1327. That in our attempts to penetrate into the nature of 
electrical action, and to deduce laws more gener# than those 
we are at present acquainted with, we should endeavour to 
bring apparently opposite effects to stand side by side in har- 
monious arrangement, is an opinion of long standing, and 
sanctioned by tbe ablest philosophers. I hope, therefore, I 
may be excused the attempt to look at the highest cases 
of conduction as analogous to, or even the same in kind with, 
those of induction and insulation. 

1328. If we consider the slight penetration of sulphur 
(1241. 1242.) or shell-lac (1234.) by electricity, or the feebler 
insulation sustained by spermaceti (1279. 1240.), as essential 
consequences and indications of their conducting power, then 
may we look on the resistance of metallic wires to the passage 
of electricity through them as insulating power. Of the 



421 


Jan. 1838.] Insulating power of the metals. 

nurr^rous well-known cases fitted to show this resistance in 
what are called the perfect conductors, the experiments of 
Professor Wheatstone best serve my present purpose, since 
they were carried to such an extent as to show that time 
entered as an element into ♦lie conditions of conduction* even 
in metals. When discharge was made through a copper wire 
2640 feet in length, and ^th of an inch in diameter, so that 
the luminous sparks at each end of the wire, and at the middle, 
could be observed in the same place, the latter was found to 
be sensibly behind the two former in time, they being by the 
conditions of the experiment simultaneous, lienee a proof of 
retardation; and what reason can be given why this retardation 
should not be of the same kind as that in spermaceti, or in 
lac, or sulphur? But as,* in them, retardation is insulation, 
and insulation is induction, why should we refuse the same 
relation to the same exhibitions of force in the metals ? 

1329. We learn from the experiment, that if time be 
allowed the retardation is gradually overcome ; and the same 
thing obtains for the spermaceti, the lac, and glass (1218.) ; 
give hut time in proportion to the retardation, and the latter is 
at last vanquished. But if that be the ease, and all the results 
are alike in kind, the only difference being in the length of 
time, why should wc refuse to metals the previous inductive 
action, which is admitted to occur in the other bodies? The 
diminution of time is no negation of the action ; nor is the 
lower degree of tension requisite to cause the forces to traverse 
the metal, a^compared to that necessary in the oases of water, 
spermaceti, or lac. These differences would only point to the 
conclusion, that in metals the particles under induction can 
transfer t ; heir forces when at a lower degree of tension or 
polarity, and with greater facility than in the instances of the 
other bodies. 

1330. Let us look at Mr. Wheatstone’s beautiful experi- 
ment in another point of view. If, leaving the arrangement at 
the middle and two ends of the long copper wire unaltered, 
we remove the two intervening portions and replace them by 
wires of iroO or platina? we shall have a much greater retarda- 
tion of the middle spark than before. If, removing the iron, 


Philosophical Transactions, 18X4, p. 583. 



422 


Conduction dependent on induction. [Series XII. 


we were to substitute for it only five or six feet of water jn a 
cylinder of the same diameter as the metal, we should have 
still greater retardation. If from water we passed to sperma- 
ceti, either directly or by gradual steps through other bodies, 
(even though we might vastly enlarge the bulk, for the pur- 
pose of evading the occurrence of a spark elsewhere (1331.) 
than at the three proper intervals,) we should have still 
greater retardation, until at last we might arrive, by degrees 
so small as to be inseparable from each other, at actual and 
permanent insulation. What, then, is to separate the prin- 
ciple of these two extremes, perfect conduction and perfect 
insulation, from each other ; since the moment we leave in the 
smallest degree perfection at either extremity, we involve the 
element of perfection at the opposit® end ? Especially top, as 
we have not in nature the case of perfection either at one 
extremity or the other, either of insulation or conduction. 

1331. Again, to return to this beautiful experiment in the 
various forms which may be given to it : the forces are not all 
in the wire (after they have left the Leyden jar) during the whole 
time (1328.) occupied by the discharge; they are disposed in 
part through the surrounding dielectric under the well-known 
form of induction ; and if that dielectric be air, induction takes 
place from the wire through the air to surrounding conductors, 
until the ends of the wire are electrically related through its 
length, and discharge has occurred, l. e. for the time during 
which the middle spark is retarded beyond the others. This 
is well shown by the old experiment, in which a^ong wire is 
so bent that two parts (Plate VIII. fig. 115.) a. b. near its ex- 
tremities shall approach within a short distance, as a quarter of 
an inch, of each other in the air. If the discharge of a Leyden 
jar, charged to a sufficient degree, be sent through such a wire, 
by far the largest portion of the electricity will pass as a spark 
across the air at the interval, and not by the metal. Does not 
the middle part of the wire, therefore, act here as an insulating 
medium, though it be of metal ? and is not the spark through 
the air an indication of the tension (simultaneous with induction) 
of the electricity in the ends of this single wire ? Why should 
not the wire and the air both be regarded as dielectrics ; and the 
action at itswoamen cement, and whilst there is tension, as an in- 
ductive action T If it acts through the contorted lines of the wire. 



Jan, 1838,] Insulating powers of bodies compared . 423 

so it also does in curved and contorted lines through air (1219. 
1251. 1231.) , and other insulating dielectrics (1228.) ; and we 
can apparently go so far in the analogy, whilst limiting the case 
to the inductive action only, as to show that amongst insulating 
dielectrics some lead away^thc lines of force from others (1229.), 
as the wire will do from worse conductors, though in it the 
principal effect is no doubt due to the ready discharge between 
the particles whilst in a low state of tension. The retardation 
is for the time insulation ; and it seems to me we may just as 
fairly compare the air at the interval a , b. (fig. 115.) and the 
wire in the circuit, as two bodies of the same kind and acting 
upon the same principles, as far as the first inductive pheno- 
mena are concerned, notwithstanding the different forms of dis- 
charge which ultimately follow*, as wc may compare, according 
to Coulomb's investigations f, different lengths of different in- 
sulating bodies required to produce the same amount of in- 
sulating effect. 

1332. This comparison is still more striking when we take 
into consideration the experiment of Mr. Harris, in which he 
stretched a fine wire across a glass globe, the air within being 
rarefied J. On sending a charge through the joint arrangement 
of metal and rare air, as much, if not more, electricity passed 
by the latter as by the former. In the air, rarefied as it was, 
there can be no doubt the discharge was preceded by induction 
(1281.) ; and to my mind all tht) circumstances indicate that 
the same was the case with the metal ; that, in fact, both sub- 
stances arc* dielectrics, exhibiting the same effects in conse- 
quence of the action of the same causes, the only variation 
being one of degree in the different substances employed. 

1333. Judging on tliese principles, velocity of discharge 
through the same wire may be varied greatly by attending to 
the circumstances which cause variations of ‘discharge through 
spermaceti or sulphur. Thus, for instance, it must vary with 
the tension or intensity of the first urging force (1231*. 1240.), 
which tension is charge and induction. So if the two ends of 
the wire, in Professor Wheatstone's experiment, were immedi- 
ately connected with two large insulated metallic surfaces ex- 

* These will he examined hereafter (1348, &e.). 

t M<5moires de l’Acad&nie, 1785, p. 012. or Eney. Britann. First. Supp. 
vol. i. p. OH. 

f Philosophical Transactions, 1834, p. 24 2, 



424 Conducting powers of bodies compared. [Series XII, 

posed to the air, so that the primary act of induction, after 
making the contact for discharge, might be in part remoVed 
from the internal portion of the wire at the first instant, and 
disposed for the moment on its surface jointly with the air and 
surrounding conductors, then I venture to anticipate that the 
middle spark would be more retarded than before ; and if these 
two plates were the inner and outer coating of a large jar or a 
Leyden battery, then the retardation of that spark would be 
still greater. 

1334. Cavendish was perhaps the first to show distinctly that 
discharge was not always by one channel*, but, if several are 
present, by many at once. We may make these different chan- 
nels of different bodies, and by proportioning their thicknesses 
and lengths, may include such substances as air, lac, spermaceti, 
water, protoxide of iron, iron and silver, and by one discharge 
make each convey its proportion of the electric force. Perhaps 
the air ought to be excepted, as its discharge by conduction is 
questionable at present (1336.) \ but the others may all be limited 
in their mode of discharge to pure conduction. Yet several of 
them suffer previous induction, precisely like the induction 
through the air, it being a necessary preliminary to their dis- 
charging action. How can we therefore separate any one of 
these bodies from the others, as to the principles and mode of 
insulating and conducting, except by mere degree ? All seem 
to me to be dielectrics acting alike, and under the same common 
laws. 

1335. I might draw another argument in favour of the gene- 
ral sameness, in nature and action, of good and bad conductors 
(and all the bodies I refer to are conductors more or less), from 
the perfect equipoise in action of very different bodies when 
opposed*to each other in magneto-electric inductive action, as 
formerly described* (213.), but am anxious to be as brief as is 
consistent with the clear examination o£ the probable truth of 
my views. 

1336. With regard to the possession by the gases of any * 
conducting power of the simple kind now under consideration, 
the question is a very difficult one to determine at present. 
Experiments seem to indicate that they do insulate certain low 
degrees of tension perfectly, and that the effects which may 
have appeared to be occasioned by conduction have been the 

* Philosophical Transactions, 1776, p. 197. 



Jan. 1838.] Dependence of conduction on induction. 425 

result of the carrying power of the charged particles, either of 
the air or of dust, in it. It is equally certain, however, that with 
higher degrees of tension or charge the particles discharge to 
one another, and that is conduction. If the gases possess the 
power of insulating a eertawi low degree of tension continuously 
and perfectly, such a result may be due to their peculiar phy- 
sical state, and the condition of separation under which their par- 
ticles arc placed. But in that, or in any ease, we must not forget 
the fine experiments of Oagniard dc la Tour*, in which he has 
shown that liquids and their vapours can be made to pass gra- 
dually into each other, to the entire removal of any marked dis- 
tinction of the two states. Thus, hot dry steam and ebhl water 
pass by insensible gradations into each other ; yet the one is 
amongst the gases as an insulator, and the other a comparatively 
good conductor. As to conducting power, therefore, the trans- 
ition from metals even up to gases is gradual ; substances make 
but one series in this respect, and the various cases must 
come under one condition and law (141.). The specific differ- 
ences of bodies as to conducting power only scr\cs to strengthen 
the general argument, that conduction, like insulation, is arc- 
suit of induction, and is an action of contiguous particles. 

1337. I might go on now to consider induction and its con- 
comitant, conduction, through mixed dielectrics, as, for instance, 
when a charged body, instead of acting across air to a distant 
uninsulated conductor, acts jointly through it and an interposed 
insulated conductor. In such a case, the air and the conduct- 
ing body arc tlie mixed dielectrics; and the latter assumes a 
polarized condition as a mass, like that which my theory as- 
sumes each particle of the air to possess at the same time 
(1679.) . But I fear to be tedious in the present condition of the 
subject, and hasten to the consideration of other matter. 

1338. To sum up, in some degree, what lias been said, 1 look 
upon the first effect of an excited body upon neighbouring mat- 
ters to be the production of a. polarized state of their particles, 
which constitutes induction ; and this arises from its action 
upon the particles in immediate contact with it, which again act 
upon those contiguous to them, and thus the forces are trans- 
ferred. to a distance. If the induction remain undiminished, 
then perfect insulation is the consequence ; and the higher the 

* Annales de Chimie, xxi. pp. 127, 178 ; or Quarterly Journal of Science, 
xv. 145. 



426 


Effect of heat on conduction . [Series XII. 

polarized condition which the particles can acquire or maintain, 
the higher is the intensity which may be given to the acting 
forces. If, on the contrary, the contiguous particles, upon ac- 
quiring the polarized state, have the powerto communicate their 
forces, then conduction occurs, and the tension is lowered, con- 
duction being a distinct act of discharge between neighbouring 
particles. The lower the state of tension at which this discharge 
between the particles of a body takes place, the better con- 
ductor is that body. In this view, insulators may be said to be 
bodies whose particles can retain the polarized state ; whilst 
conductors are those whose particles cannot be permanently 
polarized. If I be right in my view of induction, then I con- 
sider the reduction of these two effects (which have been so long 
held distinct) to an action of contiguous particles obedient to 
one common law, as a very important result ; and, on the other 
hand, the identity of character which the two acquire when 
viewed by the theory (1326.), is additional presumptive proof 
in favour of the correctness of the latter. 

1339. That heat has great influence over simple conduction 
is well known (445.), its effect being, in some cases, almost an 
entire change of the characters of the body (432. 1340.) . Har- 
ris has, however, shown that it in no respect affects gaseous 
bodies, or at least air* ; and Davy has taught us that, as a class, 
metals have their conducting power diminished by itt- 

1340. I formerly described a substance, sulphuret of silver, 
whose conducting power was increased by heat (433. 437. 438.) ; 
and 1 have since then met with another as strongly affected in 
the same way : this is fluoride of lead. When a piece of that 
substance, which had been fused and cooled, was introduced 
into the’ circuit of a voltaic battery, it stopped the current. 
Being heated, it Acquired conducting powers before it was 
visibly red hot in daylight; and even sparks could be taken 
against it whilst still solid. The current alone then raised its 
temperature (as in the case of sulphuret of silver) until it fused, 
after which it seemed to conduct as well as the metallic vessel 
containing it ; for whether the wire used to complete the circuit 
touched the fused fluoride only, or was in contact with the 
platina on which it was supported, no sensible difference in the 

* Philosophical Transactions, 1834, p. 230. f Ibid. 1821, p. 431. 



427 


Jan. 1838.] Induction and electrolytic discharge. 

forpe of the current was observed. During all the time there 
was scarcely a trace of decomposing action on the fluoride, and 
what did occur, seemed referable to the air and moisture of the 
atmosphere, and not to electrolytic action. 

1341. I have now very little doubt that periodide of mercury 
(114. 418. 691.) is a case of the same kind, and also corrosive 
sublimate (692.). I am also inclined to think, since making the 
above experiments, that the anomalous action of the protoxide 
of antimony, formerly observed and described (693. 801.), may 
be referred in part to the same eausc. 

1342. I have no intention at present of goiug into the par- 
ticular relation of heat and electricity, but we may hope here- 
after to discover by experiment the law which probably holds 
together all the above effects with those of the evolution and 
the disappearance of heat by the current, and the striking and 
beautiful results of thermo-electricity, in one common bond. 

II viii. Electrolytic discharge. 

1313. I have already expressed in a former paper (1101.), 
the view by which I hope to associate ordinary induction and 
electrolyzation. Under that view, the discharge of electric 
forces by electrolyzation is rather an effect snperadded, in a 
certain class of bodies, to those already described as constitu- 
ting induction and insulation, than one independent of and di- 
stinct from these phenomena. 

1311. Electrolytes, as respects their insulating and conduct- 
ing forces, belong to the general category of bodies (1320. 
1334.) ; and if they are in the solid state (as nearly all can as- 
sume that state), they retain their place, presenting then no 
new phenomenon (426. &c.) ; or if one occur, being in so small 
a proportion as to be almost unimportant. When liquefied, 
they also belong to the same list whilst the electric intensity is 
below a certain degree; but at a given intensity (910. 912. 
1007.), fixed for each, and very low in all known cases, they 
play a new part, causing discharge in proportion (783.) to the 
development of certain chemical effects of combination and de- 
composition ; and at this point, move out from the general class 
of insulators and conductors, to form a distinct one by them- 
selves. The former phenomena have been considered (1320. 
1338.) ; it is the latter which have now to be revised, and used 
as a test of the proposed theory of induction. 



428 Induction and electrolytic discharge. [Series XII. 

1345. The theory assumes, that the particles of the dielec- 
tric (now an electrolyte) are in the first instance brought, by 
ordinary inductive action, into a polarized state, and raised to 
a certain degree of tension or intensity before discharge com- 
mences ; the inductive state being, hi fact, a necessary preli- 
minary to discharge. By taking advantage of those circum- 
stances which bear upon the point, it is not difficult to increase 
the tension indicative of this state of induction, and so make 
the state itself more evident. Thus, if distilled water be em- 
ployed, and a long narrow portion of it placed between the 
electrodes of a powerful voltaic battery, we have at once indi- 
cations of the intensity which can be sustained at these elec- 
trodes by the inductive action through the water as a dielec- 
tric, for sparks may be obtained, gold leaves diverged, and 
Leyden bottles charged at their wires. The water is in the 
condition of the spermaceti (1322. 1323.), a bad conductor and 
a bad insulator ; but what it does insulate is by virtue of in- 
ductive action, and that induction is the preparation for and 
precursor of discharge (1338.). 

1346. The induction and tension which appear at the limits 
of the portion of water in the direction of the current, are only 
the sums of the induction and tension of the contiguous particles 
between those limits ; and the limitation of the inductive ten- 
sion, to a certain degree shows (time entering in each case as 
an important element of the result), that wdien the particles 
have acquired a certain relative state, discharge , or a transfer 
of forces equivalent to ordinary conduction, takes place. 

1347. In the inductive condition assumed by water before 
discharge comes on, the particles polarized are the particles of 
the water y that being the dielectric used* ; but the discharge 
between particle apd particle is not, as before, a mere inter- 
change of their powers or forces at the polar parts, but an 
actual separation of them into their two elementary particles, 
the oxygen travelling in one direction, and carrying with it its 
amount of the force it had acquired during the polarization, 
and the hydrogen doing the same thing in the other direction, 
until they each meet the next approaching particle, which is in 
-the same electrical state with that they have left, and by associa- 
tion of their forces with it> produce w r hat constitutes discharge. 

* See 1609—1 7 08. — Dec. 1838. 



Jan. 1838.] Action of the contiguous particles. 429 

This part of the action tray be regarded as a carrying one 
(1319. 1572. 1622.), performed by the constituent particles of 
the dielectric. The latter is always a compound body (664. 
823.) ; and by those who have considered the subject and are 
acquainted with the philosophical view of transfer which was 
first put forth by Grotthuss*, its particles may easily be com- 
pared to a series of metallic conductors under inductive action, 
which, whilst in that state, are divisible into these elementary 
moveable halves. 

1348. Electrolytic discharge depends, of necessity, upon the 
non-conduction of the dielectric as a whole, and there arc two 
steps or acts in the process: first a polarization of the mole- 
cules of the .substance, and then a lowering of the forces by the 
separation, advance in opposite directions, and recombination 
of the elements of the molecules, these being, as it were, the 
halves of the originally polarized conductors or particles. 

1349. These views of the decomposition of electrolytes and 
the consequent effect of discharge, which, as to the particular 
case, are the same with those of Grotthuss (181.) and llavy 
(182.), though they differ from those of Biot (187.), l)e la 
Hive (490.), and others, seem to me to be fully in accordance 
not merely W’ith the theory I have given of induction generally 
(1165.), hut with all the known facts of common induction, 
conduction, and electrolytic discharge; and in that respect help 
to confirm in my mind the truth -of the theory set forth. The 
new mode of discharge which electrolyzation presents must 
surely he an evidence of the action of contiguous particles ; and 
as this appears to depend directly upon a previous inductive 
state, which is the same with common induction, it greatly 
strengthens the argument which refers induction in all cases to 
an action of contiguous particles also (1295, &c.). 

1350. As an illustration of the condition hf the polarized par- 
ticles in a dielectric under induction, I may describe an experi- 
ment. Put into a glass vessel some clear rectified oil of tur- 
pentine, and introduce two wires passing through glass tubes 
where they coincide with the surface of the fluid, and termi- 
nating either in balls or points. Cut some very clean dry white 
silk into small particles, and put these also into the liquid : 


Annales de Chimie, lviii. 60. and lxiii. 20. 



480 Induction and electrolytic discharge . [Series XII. 

then electrify one of the wires by an ordinary machine and dis- 
charge by the other. The silk will immediately gather from all 
parts of the liquid, and form a band of particles reaching from 
wire to wire, and if touched by a glass rod will show consider- 
able tenacity ; yet the moment the ^upply of electricity ceases, 
the band will fall away and disappear by the dispersion of its 
parts. The conduction by the silk is in this case very small ; 
and after the best examination I could give to the effects, the 
impression on my mind is, that the adhesion of the whole is 
due to the polarity which each filament acquires, exactly as the 
particles of iron between the poles of a horse-shoe magnet are 
held together in one mass by a similar disposition of forces. 
The particles of silk therefore represent to me the condition of 
the molecules of the dielectric itself, which I assume to be 
polar, just as that of the silk is. In all cases of conductive dis- 
charge the contiguous polarized particles of the body arc able 
to effect a neutralization of their forces with greater or less 
facility, as the silk docs also in a very slight degree. Further 
wc are not able to carry the parallel, except in imagination ; 
but if wc could divide each particle of silk into two halves, and 
let each half travel until it met and united with the next half 
in an opposite state, it would then exert its carrying power 
(1347.), and so far represent electrolytic discharge. 

1351. Admitting that electrolytic discharge is a consequence 
of previous induction, then how evidently do its numerous 
cases point to induction in curved lines (521. 1216.), and to 
the divergence or lateral action of the lines of inductive force 
(1231.), and so strengthen that part of the general argument 
in the former paper ! If two balls of platina, forming the 
electrodes of a voltaic battery, are put into a large vessel 
of dilute sulphuric acid, the whole of the surfaces arfe covered 
with the respective* gases in beautifully regulated proportions, 
and the mind has no difficulty in conceiving the direction 
of the curved lines of discharge, and even the intCns^y of 
force of the different lines, by the quantity of gas evolved upon 
the different parts of the surface. From this condition of the 
lines of inductive force arise the general effects of diffusion ; 
the appearance of the anions or cathions round the edges 
and on the further side of the electrodes when in the form of 
plates ; and the maimer in which the current or discharge will 



Jan. 1838.] Variations of electrolytic discharge . 431 

follow all the forms of the electrolyte, however contorted. 
Hence, also, the effects which Nobili has so well examined 
and described* in his papei's on the distribution of currents 
in conducting masses. All these effects indicate the curved 
direction of the currents qr discharges which occur in and 
through the dielectrics, and these arc in every case preceded 
by equivalent inductive actions of the contiguous particles, 

1352. Hence also the advantage, when the exciting forces 
are weak or require assistance, of enlarging the mass of the 
electrolyte ; of increasing the size of the electrodes ; of making 
the coppers surround the zincs : — all is in harmony with the 
view of induction which I am endeavouring to examine ; I do 
not perceive as yet one fact against it, 

1353. There are many points of electrolytic discharge 
which ultimately will require to be very closely considered, 
though I can hut slightly touch upon them. It is not that, as 
far as I have investigated them, they present any contradiction 
to the view taken (for I have carefully, though unsuccessfully, 
sought for such cases,) but simply want or time as yet to pursue 
the inquiry, which prevents me from entering upon them hero. 

135 t. One point is, that different electrolytes or dielectrics 
require different initial intensities for their decomposition 
(912.). This may depend upon the degree of polarization 
which the particles require before electrolytic discharge com- 
mences. It is in direct relation to the chemical affinity of the 
substances concerned; and will probably be found to have a 
relation or analogy to the specific inductive capacity of dif- 
ferent bodies (1252. 129G.). It thus promises to assist in 
causing the great truths of those extensive sciences, which arc 
occupied in considering the forces of the particles of matter, 
to fall into much closer order and arrangement than they 
have heretofore presented. 

1355. Another point is the facilitation of electrolytic con- 
ducting power or discharge hy the addition of substances 
to the dielectric employed. This effect is strikingly shown 
where water is the body whose qualities are improved, but, as 
yet, no general law governing all the phenomena has been 


Biblioth&que Universelle, 1835, lix. 203. 410. 



432 Conducting power of electrolytes assisted. [Series XII. 

detected. Thus some acids, as the sulphuric, phosphoric, 
oxalic, and nitric, increase the power of water enormously ; 
whilst others, as the tartaric and citric acids, give but little 
power ; and others, again, as the acetic and boracic acids, do 
not produce a change sensible to tjie voltameter (739.) . Am- 
monia produces no effect, but its carbonate does. The caustic 
alkalies and their carbonates produce a fair effect. Sulphate 
of soda, nitre (753.), and many soluble salts produce much effect. 
Percy anide of mercury and corrosive sublimate produce no effect; 
nor does iodine, gum, or sugar, the test being a voltameter. 
In many cases the added substance is acted on either directly 
or indirectly, and then the phenomena are more complicated ; 
such substances arc muriatic acid (758.), the soluble proto- 
chlorides (766.), and iodides (769.), nitric acid (752.), &c. In 
other cases the substance added is not, when alone, subject to 
or a conductor of the powers of the voltaic battery, and yet 
both gives and receives power when associated with water. 
M. de la Rive has pointed this result out in sulphurous acid*, 
iodine and brominef ; the chloride of arsenic produces the 
same effect. A far more striking case, however, is presented 
by that very influential body sulphuric acid (681.) : and pro- 
bably phosphoric acid also is in the same peculiar relation. 

1356. It would seem in the cases of those bodies which 
suffer no change themselves, as sulphuric acid (and perhaps in 
all), that they affect water in its conducting power only as an 
electrolyte ; for whether little or much improved, the decom- 
position is proportionate to the quantity of electricity passing 
(727. 730.), and the transfer is therefore due to electrolytic 
discharge. This is in accordance with the fact already 
stated as regards water (984.), that the, conducting power is 
not imj^roved for electricity of force below the electrolytic 
intensity of the substance acting as the dielectric ; but both 
facts (and some others) are against the opinion which I for- 
merly gave, that the power of salts, &e. might depend upon 
their assumption of the liquid state by solution in the water 

* Quarterly Journal, xxvii. 407. or Biblioth&que Universelle, xl. 205. 
Kemp says sulphurous acid is a very good conductor, Quarterly Journal, 1831, 
p. 613. 

f Quarterly Journal, xxiv. 465. or Annales de Chimie, xxxv. 161. 



433 


Jan. 1838.] Insulation :-~-disruptive discharge. 

employed (410.). It occurs to me that the effect may perhaps 
be related to, and have its explanation in differences of specific 
inductive capacities. 

1357. I have described in the last paper, cases, ■where shell-lac 
was rendered a conductor Ijy absorption of ammonia (1291.). 
The same effect happens with muriatic acid ; yet both these sub- 
stances, when gaseous, are non-conductors ; and the ammonia, 
also when in strong solution (718.). Mr. Harris has men- 
tioned instances* in which the conducting power of metals 
is seriously altered by a very little alloy. These may have no 
relation to the former eases, but nevertheless should not be 
overlooked in the general investigation which the whole question 
requires. 

1358. Nothing is perhaps more striking in that class of 
dielectrics which we call electrolytes, than the extraordinary 
and almost complete suspension of their peculiar mode of 
effecting discharge when they are rendered solid (380. &c.) , 
even though the intensity of the induction acting through 
them may be increased a hundredfold or more (US).). It not 
only establishes a very general relation between the physical 
properties of these bodies and electricity acting bv induction 
through them, but draws both their physical and chemical 
relations so near together, as to make us hope we shall shortly 
arrive at the full comprehension of the influence they mutually 
possess over each other. 

1] ix. Disruptive discharge and insulation. 

1359. The next form of discharge has been distinguished by 
the adjective disruptive (1319.), as it in every ease displaces more 
or less the particles amongst and across which it suddenly 
breaks. I include under it, discharges in the form of sparks, 
brushes, and glow (1 105.), but exclude the eases of currents of 
air, fluids, &c., which, though frequently accompanying the 
former, are essentially distinct in their nature. 

1360. The conditions requisite for the prcxl action of an 
electric spark in its simplest form arc well known. An insu- 
lating dielectric must be interposed between two conducting 
surfaces in opposite states of electricity, and then if the 

* Philosophical Transactions, 1827, p. 22. 

2 F 



434 


Insulation, 


[Series XII. 

actions be continually increased in strength, or otherwise 
favoured, cither by exalting the electric state of the two con- 
ductors, or bringing them nearer to each other, or diminishing 
the density of the dielectric, a spark at last appears, and the 
two forces are for the time annihilated, for discharge lias 
occurred. 

1361. The conductors (which may be considered as the 
termini of the inductive action) are in ordinary cases most 
generally metals, whilst the dielectrics usually employed arc 
common air and glass. In my view of induction, however, 
every dielectric becomes of importance, for as the results arc 
considered essentially dependent on these bodies, it was to be 
expected that differences of action never before suspected 
would be evident upon close examination, and so at once give 
fresh confirmation of the theory, and open new doors of dis- 
covery into the extensive and varied fields of our science. This 
hope was especially entertained with respect to the gases, be- 
cause of their high degree of insulation, their uniformity in 
physical condition, and great difference in chemical proper- 
ties. 

1362. All the effects prior to the discharge are inductive; 
and the degree of tension which it is necessary to attain before 
the spark passes is therefore, in the examination I am now 
making of the new view of induction, a very important point. 
It is the limit of the influence which the dielectric exerts in 
resisting discharge; it is a measure, consequently, of the 
conservative power of the dielectric, which in its turn may he 
considered as becoming a measure, and therefore a representa- 
tive of the intensity of the electric forces in activity. 

1363. Many philosophers have examined the circumstances 
of this limiting action in air, but, as far as I know, none have 
come near Mr. Harris as to the accuracy with, and the ex- 
tent to, which he has carried on his investigations*. Some 
of his results I must very briefly notice, premising that. they 
are all obtained with the use of air as the dielectric between 
the conducting surfaces, 

1364. First as to the distance between the two balls used, 
or in other words, the thickness of the dielectric across which 

* Philosophical Transactions^ 1834, p. 225. 



435 


Jan. 1838.] Insulation in air : — Harris’s results. 

the induction was sustained. The quantity of electricity, 
measured by a unit jar, or otherwise on the same principle with 
the unit jar, in the charged or inductive ball, necessary to pro- 
duce spark discharge, was found to vary exactly with the dis- 
tance between the balls, or between the discharging points, and 
that under very varied and exact forms of experiment *. 

1365. Then with respect to variation in the pressure or density 
of the air. The quantities of electricity required to produce 
discharge across a constant interval varied exactly with variations 
of the density ; the quantity of electricity and density of the 
air being in the same simple ratio. Or, if the quantity was 
retained the same, whilst the interval and density of the air 
were varied, then these were found in the inverse simple ratio of 
each other, the same quantity passing across twice the distance 
with air rarefied to one half *}*• 

1366. It must be remembered that these effects take place 
without any variation of the inductive force by condensation or 
rarefaction of the air. That force remains the same in air j;, 
and in all gasses (1281. 1292.), whatever their rarefaction may 
be. 

1367. Variations of the temperature of the air produced no 
variation of the quantity of electricity required to cause dis- 
charge across a given interval §. 

Such are the general results, which I have occasion for at 
present, obtained by Mr. Harris, aftd they appear to me to be 
unexceptionable. 

1368. In the theory of induction founded upon a molecular 
action of the dielectric, we have to look to the state of that 
body principally for the cause and determination of the above 
effects. Whilst the induction continues, it is assumed that the 
particles of the dielectric are in a certain polarized stafe, the 
tension of this state rising higher in each particle as the induc- 
tion is raised to a higher degree, either by approximation of 
the inducing surfaces, variation of form, increase of the ori- 
ginal force, or other means ; until at last, the tension of the 
particles having reached the utmost' degree which they can sus- 


* Philosophical Transactions, 1834, p. 225. 
t Ibid. pp. 237, 244. 


f Ibid. p. 229. 
§ Ibid. p. 230. 



430 Insulation in air : — tension. [Series XII. 

tain without subversion of the whole arrangement, discharge 
immediately after takes place. 

1369. The theory does not assume, however, that all the par- 
ticles of the dielectric subject to the inductive action are affected 
to the same amount, or acquire the same tension. What has 
been called the lateral action of the lines of inductive force 
(1231. 1297.), and the diverging and occasionally curved form 
of these lines is against such a notion. The idea is, that any 
section taken through the dielectric across the lines of inductive 
force, and including all of them , would be equal, in the sum of 
the forces, to the sum of the forces in any other section ; and 
that, therefore, the whole amount of tension for each such section 
would be the same. 

1370. Discharge probably occurs^ not when all the particles 
have attained to a certain degree of tension, but when that 
particle which is most affected has been exalted to the subvert- 
ing or turning point (1410.). For though all the particles in 
the line of induction resist charge, and are associated in their 
actions so as to give a sum of resisting force, yet when any one 
is brought up to the overturning point, all must give way in 
the case of a spark between ball and ball. The breaking down 
of that one must of necessity cause the whole barrier to be over- 
turned, for it was at its utmost degree of resistance when it pos- 
sessed the aiding power of that one particle, in addition to the 
power of the rest, and the power of that one is now lost. Hence 
tension or intensity* may, according to the theory, be considered 
as represented by the particular condition of the particles, or 
the amount in them of forced variation from their normal state 
(1298. 1368.). 

1371. The whole effect produced by a charged conductor 
on a ‘distant conductor, insulated or not, is by my theory 
assumed to be dhe to an action propagated from particle to 
particle of the intervening and insulating dielectric, all the par- 
ticles being considered as thrown for the time into a forced con- 
dition, from which they endeavoured to return* to their normal 
or natural state. The theory, therefore, seems to supply ai} easy 

* See Harris on proposed particular meaning of these terms, Philosophical 
Transactions, 1834, p. 222 . 



437 


Jan. 1838.] Effects of distance — size— form. 

explanation of the influence of distance in affecting induction 
(1303. 1364.). As the distance is diminished induction increases; 
for there are then fewer particles in the line of inductive force to 
oppose their united resistance to the assumption of the forced or 
polarized state, and vice versd* Again, as the distance diminishes, 
discharge across happens with a lower charge of electricity ; 
for. if, as in Harris's experiments (1361.), the interval be di- 
minished to one half, then half the electricity required to dis- 
charge across the first interval is sufficient to strike across the 
second ; and it is evident, also, that at that time there arc only 
half the number of interposed molecules uniting their forces to 
resist the discharge. 

1372. The effect of enlarging the conducting surfaces which 
are opposed to each other in the act of induction, is, if the 
electricity be limited in its supply, to lower the intensity of ac- 
tion ; and this follows as a very natural consequence from the 
increased area of the dielectric across which the induction is 
effected. For by diffusing the inductive action, which at first 
was exerted through one square inch of sectional area of the 
dielectric, over two or three square inches of such area, twice 
or three times the number of molecules of the dielectric are 
brought into the polarized condition, and employed in sustaining 
the inductive action, and consequently the tension belonging to 
the smaller number on which the limited force was originally 
accumulated, must fall in a proportionate degree. 

1373. For the same reason diminishing these opposing sur- 
faces must increase the intensity, and the effect will increase 
until the surfaces become points. But in this case, the tension 
of the particles of the dielectric next the points is higher than 
that of particles midway, because of the lateral action and con- 
sequent bulging, as it were, of the lines of inductive force at 
the middle distance (1369.). 

1374. The more exalted effects of induction on a point p , or 
any small Surface, as the rounded end of a rod, when it is 
opposed to a large surface, as that of a ball or plate, rather than 
to another point or end, the distance being in both cases the 
same, fall into harmonious relation with my theory (1302.). For 
in the latter case, the small surface p is affected only by those 
particles which are brought into the inductive condition by the 



438 Insulation in air ; — rarefaction. {Series XII. 

equally small surface of the opposed conductor, whereas ^vhen 
that is a ball or plate the lines of inductive force from the 
latter, are concentrated, as it were, upon the end p . Now 
though the molecules of the dielectrics against the large surface 
may have a much lower state of tension than those against the 
corresponding smaller surface, yet they are also far more nu- 
merous, and, as the lines of inductive force converge towards 
a point, arc able to communicate to the particles contained in 
any cross section (1369.) nearer the small surface an amount of 
tension equal to their own, and consequently much higher for 
each individual particle ; so that at the surface of the smaller 
conductor, the tension of a particle rises much, and if that con- 
ductor were to terminate in a point, the tension would rise to 
an infinite degree, except that it is limited, as before (1368.), 
by discharge. The nature of the discharge from small sur- 
faces and points under induction will be resumed hereafter 
(1425. &c.) . 

1375. Rarefaction of the air does not alter the intensity of 
inductive action (1281. 1287.) ; nor is there any reason, as far 
as I can perceive, why it should. If the quantity of electricity 
and the distance remain the same, and the air be rarefied one 
half, then, though one half of the particles of the dielectric are 
removed, the other half assume a double degree of tension in 
their polarity, and therefor^ the inductive forces are balanced, 
and the result remains unaltered as long as the induction and 
insulation arc sustained. But the case of discharge is very dif- 
ferent ; for as there are only half the number of dielectric par- 
ticles in the rarefied atmosphere, so these are brought up to 
the discharging intensity by half the former quantity of electri- 
city ^discharge, therefore, ensues, and such a consequence of 
the theory is in, perfect accordance with Mr. Harris's results 
(1365.). 

1376. The increase of electricity required to cause discharge 
over the same distance, when the pressure of the air or its 
density is increased, flows in a similar manner, and on the same 
principle (1375.), from the molecular theory. 

1377. Here I think my view of induction has a decided ad- 
vantage over others, especially over that which refers the re- 
tention of electricity on the surface of conductors in air to the 



Jan. 1838 .] 


Pressure of the air . 


439 


pressure of the atmosphere (1305.). The latter is the view 
which, being adopted by Poisson and Biot*, is also, I believe, 
that generally received ; and it associates two such dissimilar 
things, as the ponderous air and the subtile and even hypothe- 
tical fluid or fluids of electricity, by gross mechanical relations ; 
by the bonds of mere static pressure. My theory, on the con- 
trary, sets out at once by connecting the electric forces with the 
particles of matter ; it derives all its proofs, and even its origin 
in the first instance, from experiment ; and then, without any 
further assumption, seems to offer at once a full explanation of 
these and many other singular, peculiar, and, I think, hereto- 
fore unconnected effects. 

1378. An important assisting experimental argument may 
here be adduced, derived from the difference of specific induc- 
tive capacity of different dielectrics (1209. 1274. 1278.). Con- 
sider an insulated sphere electrified positively and placed in 
the centre of another and larger sphere uninsulated, a uniform 
dielectric, as air, intervening. The case is really that of my 
apparatus (1187.), and also, in effect, that of any ball electri- 
fied in a room and removed to some distance from irregularly- 
formed conductors. Whilst things remain in this state the 
electricity is distributed (so to speak) uniformly over the surface 
of the electrified sphere. But introduce such a dielectric as 
sulphur or lac, into the space between the two conductors on 
one side only, or opposite one part of the inner sphere, and 
immediately the electricity on the latter is diffused unequally 
(1229. 1270. 1309.), although the form of the conducting sur- 
faces, their distances, and the pressure of the atmosphere re- 
main perfectly unchanged. 

1379. Fusinieri took a different view from that of Poisson, 
Biot, and others, of the reason why rarefaction of ait caused 
easy diffusion of electricity. He considered the effect as due 
to the removal of the obstacle which the air presented to the 
expansion of the substances from which the electricity passedf. 
But plktina balls show the phenomena in vacuo as well as vola- 
tile metals and other substances; besides which, when the 

* Encyclopedia Britannica, Supplement, vol. iv. Article Electricity, pp. 70, 
81, &c. 

t Bibl. Univ. 1831, xlviii. 875. 



440 Insulation in different gases. [Series XII. 

rarefaction is very considerable, tbe electricity passes with 
scarcely any resistance, and the production of no sensible h&at ; 
so that I think Eusinieri's view of the matter is likely to gain 
but few assents. 

1380. I have no need to remark upon the discharging or 
collecting power of flame or hot air. I believe, with Harris, 
that the mere heat does nothing (1367.), the rarefaction only 
being influential. The effect of rarefaction has been already 
considered generally (1375.) ; and that caused by the heat of 
a burning light, with the pointed form of the wick, and the 
carrying power of the carbonaceous particles which for the time 
are associated with it, are fully sufficient to account for all the 
effects. 

1381. We have now arrived at the important question, how 
will the inductive tension requisite for insulation and disruptive 
discharge be sustained in gases, which, having the same phy- 
sical state and also the same pressure and the same tempera- 
ture as airy differ from it in specific gravity, in chemical quali- 
ties, and it may be in peculiar relations, which not being as yet 
recognized arc purely electrical (1361.) ? 

1382. Into this question I can enter now only as far as is 
essential for the present argument, namely, that insulation and 
inductive tension do not depend merely upon the charged con- 
ductors employed, but also, r and essentially, upon the inter- 
posed dielectric, in cousequence of the molecular action of its 
particles (1292.) . 

1383. A glass vessel a (fig. 127.)* was ground at the top 
and bottom so as to be closed by two ground brass plates, b 
and c ; b carried a stuffing box, with a sliding rod d terminated 
by a brass ball s below and a ring above. The lower plate 
was connected with a foot, stop-cock, and socket, e , / and g; 
and. also with a brass ball /, "which by means of a stem attached 
to it and entering the socket g , could be fixed at various 
heights. Ihe metallic parts of this apparatus were not var- 
nished, but the glass was well covered with a coat of shell-lac 
previously dissolved in alcohol. On exhausting the vessel at 
the air-pump it could be filled with any other gas than air, and, 

* The drawing is to a scale of J. 



Jan. 1838.] 


Apparatus used , 


441 


in such cases, the gas so passed in was dried whilst entering 
by {used chloride of calcium. 

1384. The other part of the apparatus consisted of two in- 
sulating pillars, h and i , to which were fixed two brass balls, 
and through these passed t\jo sliding rods, k and m, terminated 
at each end by brass balls ; n is the end of an insulated con- 
ductor, which could be rendered either positive or negative 
from an electrical machine ; o and p arc wires connecting it 
with the two parts previously described, and q is a wire which, 
connecting the two opposite sides of the collateral arrange- 
ments, also communicates with a good discharging train r (392.). 

1385. It is evident that the discharge from the machine elec- 
tricity may pass either between s and /, or S and L. The re- 
gulation adopted in the fir^t experiments was to keep s and l 
with their distance unchanged , but to introduce first one gas 
and then another into the vessel a , and then balance the dis- 
charge at the one place against that at the other; for by making 
the interval at u sufficiently small, all the discharge would pass 
there, or making it sufficiently large it would all occur at the 
interval v in the receiver. On principle it seemed evident, that 
in this way the varying interval u might be taken as a measure, 
or rather indication of the resistance to discharge through the 
gas at the constant interval v. The following are the constant 
dimensions. 

Ball s \ 0*93 of an inch. 

Ball S 0*96 of an inch. 

Ball l 2*02 of an inch. 

Ball L 1*95 of an inch. 

Interval v 0*62 of an inch. 

1386. On proceeding to experiment it was found that when 
air or any gas was in the receiver a , the interval u was not a 
fixed one ; it might be altered through a certain range of dis- 
tance, and yet sparks pass either there or at v in the receiver. 
The extremes Were therefore noted, i. e. the greatest distance 
short of that at which the discharge always took place at v in 
the gas, and the least distance short of that at which it always 
took place "at u in the air. Thus, with air in the receiver, the 
extremes at u were 0*56 and 0*79 of <an inch, the range of 0*23 
between these distances including intervals at which sparks 
passed occasionally either at one place or the other. 



442 


Insulation in different gases . [Series XII. 

1387. The small balls s and S could be rendered either po- 
sitive or negative from the machine, and as gases were expected 
and were found to differ from each other in relation to this 
change (1399.), the results obtained under these differences of 
charge were also noted. 

1388. The following is a Table of results ; the gas named is 
that in the vessel a. The smallest, greatest, and mean inter- 
val at u in air is expressed in parts of an inch, the interval v 
being constantly 062 of an inch. 



Smallest. Greatest. 

Mean. 

c Air, s and S, pos. 

060 

0*79 

0695 

(. Air, s and S, neg. . . . 

0*59 

068 

0*635 

f Oxygen, s and S, pos. . . 

041 

0*60 

0*505 

(.Oxygen, s and 8, neg. . . 

r 0*50 

0*52 

0*510 

C Nitrogen, s and S, pos. . 

0*55 

0*68 

0615 

1 Nitrogen, s and S, neg. . 

0*59 

0*70 

0*645 

f Hydrogen, 5 and S, pos. . 

0*30 

0*44 

0*370 

h Hydrogen, s and S, neg. . 

0*25 

0*30 

0275 

f Carbonic acid, s and S, pos. 

0*56 

072 

0*610 

(. Carbonic acid, s and S, neg. 

0*58 

0*60 

0590 

f Olefiant gas, s and S, pos. 

0*64 

0*86 

0*750 

L Olefiant gas, s and S, neg. 

069 

0*77 

0*730 

f Coal gas, s and S, pos. 

0*37 

061 

0*490 

(, Coal gas, s and S, neg. 

0*47 

0*58 

0*525 

f Muriatic acid gas, s and S, pos 

0*89 

1*32 

1*105 

1 Muriatic acid gas, s and S, neg 

067 

0*75 

0*720 

1389. The above results were all obtained 

at one time. On 

other occasions other experiments 

were made, which 

gave ge- 

nerally the same results as to order, though not as to numbers. 

Thus 




Hydrogen, s and S, pos. . . . 

0*23 

057 

0*400 

Carbonic acid, 5 and S, pos. 

051 

1*05 

0*780 

Olefiant gas, s and S, pos. 

0*66 

1*27 

0*965 


I did not notice the difference of the barometer on the days of 
experiment*. 


* Similar experiments in different gases are described at 1507. 1508.— Bee. 
1838. 



443 


Jan. 1838.] Variations of the insulating distance. 

.1390. One would have expected only two distances, one for 
each interval, for which the discharge might happen either at 
one or the other ; and that the least alteration of either would 
immediately cause one to predominate constantly over the other. 
But that under common circumstances is not the ease. With 
air in the receiver, the variation amounted to 0*2 of an inch 
nearly on the smaller interval of (Hi, and with muriatic acid 
gas, the variation was above 0*4 on the smaller interval of 0*9. 
Why is it that when a tixed interval (the one in the receiver) 
will pass a spark that cannot go across 0*6 of air at one time, 
it will immediately after, and apparently under exactly similar 
circumstances, not pass a spark that can go across 0*8 of air? 

1391. It is probable that part of this variation will be traced 
to particles of dust in tl** air drawn into and about the circuit 
(15(38.). I believe also that part depends upon a variable 
charged condition of the surface of the glass vessel a. That 
the whole of the effect is not traceable to the influence of cir- 
cumstances in the vessel «, may be deduced from the fact, that 
when sparks occur between balls in free air they frequently are 
not straight, and often pass otherwise than by the shortest di- 
stance. These variations in air itself, and at different parts of 
the very same balls, shows the presence and influence of circum- 
stances* which are calculated to produce effects of the kind 
now under consideration. 

1392. When a spark had passed at either interval, then, ge- 
nerally, more tended to appear at the same interval, as if a 
preparation had been made for the passing of the latter sparks. 
So also on continuing to work the machine quickly the sparks 
generally followed at the same place. This effect is probably 
due in part to the warmth of the air heated by the preceding 
spark, in part to dust, and 1 suspect in part to something un- 
perceived as yet in the circumstances of discharge. 

1393. A very remarkable difference, which is constant in its 
direction, occurs when the electricity communicated to the halls 
s and S is changed from positive to negative, or in the contrary 
direction. It is that the range of variation is always greater 
when the small balls are positive than when they are negative. 
This is exhibited in the following Table, drawn from the 
former experiments. 



444 Insulation in different gases. [Series XII. 



Pos. 

N eg. 

In Air the range was 

. . 019 

009 

Oxygen. . . . 

. . 0Y9 

0*02 

Nitrogen . 

. . 013 

0*11 

Hydrogen . 

. . c 0*14 

0*05 

Carbonic acid. 

. . 0-16 

002 

Olefiant gas . 

. . 0*22 

0*08 

Coal gas . 

. . 0*24 

0*12 

Muriatic acid. 

. . 0*43 

0*08 


I have no doubt these numbers require considerable correction, 
but the general result is striking, and the differences in several 
cases very great. 

1394. Though, in consequence of the variation of the 
striking distance (138(b), the interval in air fails to be a measure, 
as yet, of the insulating or resisting power of the gas in the 
vessel, yet wc may for present purposes take the mean interval 
as representing in some degree that power. On examining 
these mean intervals as they are given in the third column 
(1388.), it will be very evident, that gases, when employed as 
dielectrics, have peculiar electrical relations to insulation, and 
therefore to induction, very distinct from such as might be sup- 
posed to depend upon their mere physical qualities of specific 
gravity or pressure. 

1395. First, it is clear that at the same pressure they are not 
alike, the difference being as great as 37 and 110. When the 
small balls arc charged positively, and with the same surfaces 
and the same pressure, muriatic acid gas has three times the in- 
sulating or restraining power (1362.) of hydrogen gas, and 
nearly twice that of oxygen, nitrogen, or air. 

1396. Yet it is evident that the difference is not due to spe- 
cific gravity, for though hydrogen is the lowest, and therefore 
lower than oxygen, oxygen is much beneath nitrogen, or than 
olefiant gas ; and carbonic acid gas, though considerably hea- 
vier than olefiant gas or muriatic acid gas, is lower than either. 
Oxygen as a heavy, and olefiant as a light gas, are in strong 
contrast with each other ; and if we may reason of olefiant gas 
from Harris's results with air (1365.), then it might be rarefied 
to two-thirds its usual density, or to a specific gravity of 9*3 
(hydrogen being 1), and having neither the same density nor 



445 


Jan. 1838.] Specific differences of the gases. 

pressure as oxygen, would have equal insulating powers with it, 
or "equal tendency to resist discharge. 

1397. Experiments have already been described (1291. 1292.) 
which show that the gases arc sensibly alike in their inductive 
capacity. This result is not in contradiction with the existence 
of great differences in their restraining power. The same point 
has been observed already in regard to dense and rare air 
(1375.). 

1398. Hence arises a new argument proving that it cannot be 
mere pressure of the atmosphere which prevents or governs 
discharge (1377. 1378.), but a specific electric quality or rela- 
tion of the gaseous medium. Hence also additional argument 
for the theory of molecular inductive action. 


1399. Other specific differences amongst the gases may be 
drawn from the preceding series of experiments, rough and 
hasty as they are. Thus the positive and negative series of 
mean intervals do not give the same differences. It has been 
already noticed that the negative numbers are lower than the 
positive (1393.), but, besides that, the order of the positive and 
negative results is not the same. Thus, on comparing the mean 
numbers (which represent for the present insulating tension,) 
it appears that in air, hydrogen, carbonic acid, olefiant gas and 
muriatic acid, the tension rose higher when the smaller ball was 
made positive than when rendered negative, whilst in oxygen, 
nitrogen, and coal gas, the reverse was the case. Now though 
the numbers cannot be trusted as exact, and though air, oxygen, 
and nitrogen should probably be on the same side, yet some of 
the results, as; for instance, those with muriatic acid, fully show 
a peculiar relation and difference amongst gases in this respect. 
This was further proved by making the interval in air O' 8 of an 
inch whilst muriatic acid gas was in the vessel a ; for on char- 
ging the small balls s and S positively, all the discharge took 
place through the air ; but on charging them negatively, all the 
discharge took place through the muriatic acid gas. 

1400. So also, when the conductor n was connected only with 
the muriatic acid gas apparatus^ it was found that the discharge 
■was more facile when the small ball s was negative than when 
positive ; for in the latter case, much of the electricity passed 



446 


Insulation in liquids and sdftds. [Sebies XII. 

off as brusli discharge through the air from the connecting wire 
p ; but in the former case it all seemed to gb through the ifiu- 
riatic acid. 

1401. The consideration, however, of positive and negative 
discharge across air and other gases will be resumed in the fur- 
ther part of this, or in the next paper (1465. 1525.). 

1402. Here for the present I must leave this part of the sub- 
ject, which had for its object only to observe how far gases 
agreed or differed as to their power of retaining a charge on 
bodies acting by induction through them. All the results con- 
spire to show that Induction is an action of contiguous mole- 
cules (1295. &c.) ; but besides confirming this, the first prin- 
ciple placed for proof in the present inquiry, they greatly assist 
in developing the specific properties of each gaseous dielectric, 
at the same time showing that further and extensive experi- 
mental investigation is necessary, and holding out the promise 
of new discovery as the reward of the labour required. 

1403. When we pass from the consideration of dielectrics 
like the gases to that of bodies having the liquid and solid con- 
dition, then our reasonings in the present state of the subject 
assume much more of the character of mere supposition. Still 
I do not perceive anything adverse to the theory, in the pheno- 
mena which such bodies present. If we take three insulating 
dielectrics, as air, oil of turpentine and shell-lac, and use the 
same balls or conductors at the same intervals in these three 
substances, increasing the intensity of the induction until dis- 
charge take place, we shall find that it must be raised much 
higher in the fluid than for the gas, and higher still in the solid 
than for the fluid. Nor is this inconsistent with the theoiy ; 
for with the liquid^ though its molecules are free to move almost 
as easily as those of the gas, there are many more particles in- 
troduced into the given interval ; and such is also the case when 
the solid body is employed. Besides that with the solid, the 
cohesive force of the body used will produce some effect; for 
though the production of the polarized states in the particle of 
a solid may not be obstructed, but, on the contrary, may in some 
cases be even favoured (1164. 1344.) by its solidity or other 
circumstances, yet solidity may well exert an influence on the 



447 


Jan. 1838.] Disruptive discharge : — electric spark. 

point of, final subversion, (just as it prevents discharge in an 
electrolyte,) and so enable inductive intensity to rise to a much 
higher degree. 

1404. In the cases of solids and liquids too, bodies may, and 
most probably do, possess specific differences as to their ability 
of assuming the polarized state, and also as to the extent to 
which that polarity must rise before discharge occurs. An 
analogous difference exists in the specific inductive capacities 
already pointed out in a few substances (1278.) in the last paper. 
Such a difference might even account for the various degrees 
of insulating and conducting power possessed by different 
bodies, and, if it should be found to exist, would add further 
strength to the argument in favour of the molecular theory of 
inductive action. 

1405. Having considered those various eases of sustained 
insulation in non-conducting dielectrics up to the highest point 
which they can attain, we find that they terminate at last in 
disruptive discharge ; the peculiar condition of the molecules 
of the dielectric which was necessary to the continuous induc- 
tion, being equally essential to the occurrence of that effect 
which closes all the phenomena. This discharge is not only in 
its appearance and condition different to the former modes by 
which the lowering of the powers was effected (1320. 1343.), 
but, whilst really the same in principle, varies much from itself 
in certain characters, and thus presents us with the forms of 
sparkj brtish , and glow (1359.). I will first consider the spark , 
limiting it for the present to the ease of discharge between two 
oppositely electrified conducting surfaces. 

The electric spark or flash. 

1406. The spark is consequent upon a discharge or lowering 
of the polarized inductive state of many dielectric particles, by 
a particular action of a few of the particles occupying a very 
small and limited space ; all the previously polarized particles 
returning to their first or normal condition in the inverse order 
in which they left it, and uniting their powers meanwhile to 
produce, .or rather to continue, (1417. — 1436.) the discharge 
effect in the" place where the subversion of force first occurred. 



448 Path of the electric spark. [Series XII. 

My impression is, that the few particles situated where dis- 
charge occurs are not merely pushed apart, but assume a pecu- 
liar state, a highly exalted condition for the time, i. e. have thrown 
upon them all the surrounding forces in succession, and rising 
up to a proportionate intensity of condition, perhaps equal to 
that of chemically combining atoms, discharge the powers, 
possibly in the same manner as they do theirs, by some opera- 
tion at present unknown to us ; and so the end of the whole. 
The ultimate effect is exactly as if a metallic wire had been put 
into the place of the discharging particles ; and it does not 
seem impossible that the principles of action in both cases, may, 
hereafter, prove to be the same. 

1407. The path of the spark, or of the discharge, depends on 
the degree of tension acquired by the particles in the line of 
discharge, circumstances, which in every common case are 
very evident and by the theory easy to understand, rendering 
it higher in them than in their neighbours, and, by exhalting 
them first to the requisite condition, causing them to determine 
the course of the discharge. Hence the selection of the path, 
and the solution of the wonder which Harris has so well de- 
scribed* as existing under the old theory. All is prepared 
amongst the molecules beforehand, by the prior induction, for 
the path either of the electric spark or of lightning itself. 

1408. The same difficulty is expressed as a principle by 
Nobili for voltaic electricity^, almost in Mr. Harris's words, 
namely f , “ electricity directs itself towards the point where it 
can most easily discharge itself," and the results of this as a 
principle he has well wrought out for the case of voltaic cur- 
rents. But the solution of the difficulty, or the proximate 
cause of the effects, is the same; induction brings the particles 
up to or towards a certain degree of tension (1370.) ; and by 
those which first attain it, is the discharge first and most effi- 
ciently performed. 

1409. The moment of discharge is probably determined by 
that molecule of the dielectric which, frpm the circumstances 
has its tension most quickly raised up to the maximutn inten- 
sity. In all cases where the discharge passes from conductor 
to conductor this molecule must be on the surface of one of 

* Nautical Magazine, 1834, p. 229. 

t Biblioth&que Univeraelle, 1835, lix. 275. 



449 


Jan. 1838.] Spark : — its occurrence determined . 

them; but when it passes between a conductor and a non- 
coif ductor, it is, perhaps, not always so (1153.). When this 
particle has acquired its maximum tension, then the whole bar- 
rier of resistance is broken down in the line or lines of induc- 
tive action originating at it, and disruptive discharge occurs 
(1370.) : and such an inference, drawn as it is from the theory, 
seems to me in accordance with Mr. Harris's facts and conclu- 
sions respecting the resistance of the atmosphere, namely, that 
it is not really greater at any one discharging distance than 
another*. 

1410. It seems probable, that the tension of a particle of the 
same dielectric, as air, which is requisite to produce discharge, 
is a constant quantity , whatever the shape of the part of the 
conductor with which it is in contact, whether ball or point; 
whatever the thickness or depth of dielectric throughout which 
induction is exerted ; perhaps, even, whatever the state, as to 
rarefaction or condensation of the dielectric ; and whatever the 
nature of the conductor, good or bad, with which the particle 
is for the moment associated. In saying so much, 1 do not 
mean to exclude small differences which may bo caused by the 
reaction of neighbouring particles on the deciding particle, and 
indeed, it is evident that the intensity required in a particle must 
be related to the condition of those which arc contiguous. But 
if the expectation should be found to approximate to truth, wliat 
a generality of character it present's ! and, in the definiteness of 
the power possessed by a particular molecule, may w 7 e not hope to 
find an immediate relation to the force which, being electrical, 
is equally definite and constitutes chemical affinity ? 

1411. Theoretically it would seem that, at the moment of 
discharge by the spark in one line of inductive force, n<?t merely 
would all the other lines throw their forces into this one 
(1406.), hut the lateral effect, equivalent to a^rcpulsion of these 
lines (1224. 1297.) would be relieved and, perhaps, followed 
by a contrary action, amounting to a collapse or attraction of 
these parts. Having long sought for some transverse force in 
statical electricity, which should he the equivalent to magnetism 
or the transverse force of current electricity, and conceiving 
that it might he connected with the transverse action of the 
lines of inductive force already described (1297.), I was desi- 

* Philosophical Transactions, 1834, pp. 227, 229. 

2 G 



450 


Sparks : — their mutual affections . [Series XII. 

rous, by various experiments, of bringing out the effect o£ such 
a force, and making it tell upon the phenomena of electro-mag- 
netism and magneto-electricity*. 

1412. Amongst other results, I expected and sought for the 
mutual affection, or even the lateral coalition of two similar 
sparks, if they could be obtained simultaneously side by side, 
and sufficiently near to each other. For this purpose, two simi- 
lar Leyden jars were supplied with rods of copper projecting 
from their balls in a horizontal direction, the rods being about 
0*2 of an inch thick, and rounded at the ends. The jars were 
placed upon a sheet of tinfoil, and so adjusted that their rods, 
a and h , were near together, in the position represented in plan 
at fig. 11C ; c and d were two brass balls connected by a brass 
rod and insulated : e was also a brass ball connected, by a wire, 
with the ground and with the tinfoil upon which the- Leyden 
jars were placed. By laying an insulated metal rod across from 
a to b y charging the jars, and removing the rod, both the jars 
could be brought up to the same intensity of charge (1370.). 
Then, making the ball e approach the ball d y at the moment 
the spark passed there, two sparks passed between the rods n , 
o, and the ball c ; and as far as the eye could judge, or the con- 
ditions determine, they were simultaneous. 

1413. Under these circumstances two modes of discharge 
took place ; either each end had its own particular spark to the 
ball, or else one end only was associated by a spark with the 
ball, but was at the same time related to the other end by a 
spark between the two. 

1414. When the ball c was about an inch in diameter, the 
ends n and o, about half an inch from it, and about 0‘4 of an 
inch from each other, the two sparks to the ball could be ob- 
tained* When, for the purpose of bringing the sparks nearer 
together, the ends, n and a, were brought closer to each other, 
then, unless very carefully adjusted, only one end had a spark 
with the ball, the other having a spark to it; and the least 
variation of position would cause either n or o to be the end which, 
giving the direct spark to the ball, was also the one through, or 
by means of which, the other discharged its electricity. 

1415. On making the ball c smaller, I found that then it was 
* Seefmther investigations of this subject, 1668 — 1660 , 1700 — 1706 .— 



Jan. 1838.] The spark facilitates disruptive discharge . 451 

needful to make the interval between the ends n and o larger 
in proportion to the distance between them and the ball c . On 
making c larger, I found I could diminish the interval, and so 
bring the two simultaneous separate sparks closer together, 
until, at last, the distance between them was not more at the 
widest part than 0*6 of their whole length. 

1416. Numerous sparks were then passed and carefully ob- 
served. They were very rarely straight, but either curved or 
bent irregularly. In the average of cases they were, 1 think, 
decidedly convex towards each other ; perhaps two-thirds pre- 
sented more or less of this effect, the rest bulging more or less 
outwards. I was never able, however, to obtain sparks which, 
separately leaving the ends of the wires n and o , conjoined into 
one spark before they reached or communicated with the ball 
c. At present, therefore, though I think T saw a tendency in 
the sparks to unite, I cannot assert it as a fact. 

1417. But there is one very interesting effect here, analogous 
to, and it may be in part the same w r ith, that 1 was searching 
for : I mean the increased facility of discharge where the spark 
passes. For instance, in the cases where one end, as ?i, 
discharged the electricity of both ends to the ball c, fig. 116, 
the electricity of the other end o, had to pass through an in- 
terval of air 1*5 times as great as that which it might have 
taken, by its direct passage between the end and the bail itself. 
In such cases, the eye could not distinguish, even by the use 
of Wheatstone's means*, that the spark from the end w, which 
contained both portions of electricity, was a double spark. It 
could not have consisted of two sparks taking separate courses, 
for such an effect would have been visible to the eye; but it is 
just possible, that the spark of the first end a and its jar, pass- 
ing at the smallest interval of time before that of the other o, 
had heated and expanded the air in its course, and made it so 
much more favourable to discharge, that the electricity of the 
end o preferred leaping across to it and taking a very circuitous 
route, rather than the more direct one to the ball. It must, 
however, be remarked, in answer to this supposition, that the 
one spark between d and e would, by its influence, tend to pro- 
duce simultaneous discharges at n and o, and certainly did so, 

* Philosophical Transactions, 1834, pp. 584, 585. 

2 q 2 



452 Sparks in different gases. [Series XII. 

when no preponderance was given to one wire over the other, 
as to the previous inductive effect (1414.). 

1418. The fact, however, is, that the disruptive discharge is 
favourable to itself. It is at the outset a case of tottering equili- 
brium : and if time be an element in discharge, in however 
minute a proportion (1436.), then the commencement of the act 
at any point favours its continuance and increase there, and 
portions of power will be discharged by a course which they 
would not otherwise have taken. 

1419. The mere heating and expansion of the air itself by the 
first portion of electricity which passes, must have a great influ- 
ence in producing this result. 

1420. As to the result itself, we sec its effect in every 
electric spark ; for it is not the whole quantity which passes 
that determines the discharge, but merely that small portion of 
force which brings the deciding molecule (1370.) up to its 
maximum tension; then, when its forces are subverted and dis- 
charge begins, all the rest passes by the same course, from the 
influence of the favouring circumstances just referred to; and 
whether it be the electricity on a square inch, or a thousand 
square inches of charged glass, the discharge is complete. 
Hereafter we shall find the influence of this effect in the for- 
mation of brushes (1435.) ; and it is not impossible that we may 
trace it producing the jagged spark and the forked lightning. 


1421. The characters of the electric spark in different gases 
vary, and the variation may be due simply to the effect of the 
heat evolved at the moment. But it may also be due to that 
specific relation of the particles and the • electric forces which I 
have assumed as the basis of a theory of induction ; the facts 
do not oppose such a view ; and in that view, the variation 
strengthens the argument for molecular action, as it would 
seem to show the influence of the latter in every part of the 
electrical effect (1423. 1454.). 

1422. The appearances of the sparks in different gases have 
often been observed and recorded*, but I think it not out of 

* See Van Marum’a description of the Teylerian machine, vol. i. p. 112., 
and vol. ii. p. 196.; also Ency. Britan., vol. vi,, Article Electricity, pp. 505, 507. 



Their characters . 


453 


Jan. 1838.] 

placQ to notice briefly the following results : they were obtained 
with balls of brass, (platina surfaces would have been better,) 
and at common pressures. In air, the sparks have that in- 
tense light and bluish colour which are so well known, and 
often have faint or dark parte in their course, when the quan- 
tity of electricity passing is not great. In nitrogen, they arc 
very beautiful, having the same general appearance as in air, 
but have decidedly more colour of a bluish or purple charac- 
ter, and I thought were remarkably sonorous. In oxygen, the 
sparks were whiter than in air or nitrogen, and I think not so 
brilliant. In hydrogen, they had a very fine crimson colour, 
not due to its rarity, for the character passed away as the 
atmosphere was rarefied (1159.)*. Very little sound was pro- 
duced in this gas ; but that is a consequence of its physical 
condition f. In carbonic acid gas, the colour was similar to 
that of the spark in air, but with a little green in it : the 
sparks were remarkably irregular in form, more so than in 
common air : they could also, under similar circumstances as 
to size of ball. See., be obtained much longer than in air, the 
gas showing a singular readiness to cause the discharge in the 
form of a spark. In muriatic acid gas , the spark was nearly 
white : it was always bright throughout, never presenting 
those dark parts which happen in air, nitrogen, and some 
other gases. The gas was dry, and during the whole experi- 
ment the surface of the glass globe w'ithin remained quite dry 
and bright. In coal gas , the spark was sometimes green, 
sometimes red, and occasionally one part was green and an- 
other red : black parts also occur very suddenly in the line of 
the spark, i. e. "they are not connected by any dull part with 
bright portions, but the two seem to join directly one with the 
other. 

1423. These varieties of character impress my mind with a 
feeling, that they are due to a direct relation of the electric 
powers to the particles of the dielectric through which the 
discharge occurs, and are not the , mere results of a casual 
ignition or a secondary kind of action of the electricity, upon 

* Von Alarum says they are about four times as large in hydrogen as in air; 
vol. i. p. 122. 

f Leslie. Cambridge Phil. Transactions, 267. 



454 Electrical brush ; — its appearance . [Series XII, 

the particles which it finds in its course and thrusts aside \n its 
passage (1454.). 

1424. The spark may be obtained in media which are far 
denser than air, as in oil of turpentine, olive oil, resin, glass, 
&c. : it may also be obtained in# bodies which being denser 
likewise approximate to the condition of conductors, as sper- 
maceti, water, &c. But in these cases, nothing occurs which, 
as far as I can perceive, is at all hostile to the general views I 
have endeavoured to advocate. 

The electrical brush. 

1425. The brush is the next form of disruptive discharge 
which I shall consider. There are, many ways of obtaining it, 
or rather of exalting its characters ; and all these ways illustrate 
the principles upon which it is produced. If an insulated con- 
ductor, connected with the positive conductor of an electrical 
machine, have a metal rod O' 3 of an inch in diameter projecting 
from it outwards from the machine, and terminating by a rounded 
end or a small ball, it will generally give good brushes ; or, if 
the machine be not in good action, then many ways of assisting 
the formation of the brush can be resorted to ; thus, the hand 
or any large conducting surface may be approached towards the 
termination to increase inductive force (1374.) : or the termi- 
nation may be smaller arid of badly conducting matter, as 
wood : or sparks may be taken between the prime conductor 
of the machine and the secondary conductor to which the ter- 
mination giving brushes belongs ; or, which gives to the brushes 
exceedingly fine characters and great magnitude, the air around 
the termination may be rarefied more or less, either by heat or 
the air pump ; the former favourable circumstances being also 
continued. 

142G. The brush when obtained by a powerful machine on 
a ball about 07 of an inch in diameter, at the end of a long 
brass rod attached to the positive prime conductor* had the 
general appearance as to form represented in fig, 117. : a short 
conical bright part or root appeared at the middle part of the 
ball projecting directly from it, which, at a little distance from 
the hall, broke out suddenly into a wide, brush of pale ramifi- 



Jan. 1838.] Not continuous ; — analysed . 455 

cations having a quivering motion, and being accompanied at 
the same time with a low dull chattering sound. 

1427. At first the brush seems continuous, but Professor 
Wheatstone has shown that the whole phenomenon consists of 
successive intermittent discharges*. If the eye be passed 
rapidly, not by a motion of the head, but of the eyeball itself, 
across the direction of the brush, by first looking steadfastly 
about 10° or 15° above, and then instantly as much below it, 
the general brush will be resolved into a number of individual 
brushes, standing in a row upon the line which the eye passed 
over ; each elementary brush being the result of a single dis- 
charge, and the space between them representing both the 
time during which the eye was passing over that space, and 
that which elapsed betweep one discharge and another. 

1428. The single brushes could easily be separated to eight 
or ten times their own width, but were not at the same time 
extended, i. e. they did not become more indefinite in shape, 
but, on the contrary, less so, each being more distinct in form, 
ramification, and character, because of its separation from the 
others, in its effects upon the eye. Mach, therefore, was in- 
stantaneous in its existence (1136.). Each had the conical root 
complete (1426.). 

1429. On using a smaller ball, the general brush was smaller, 
and the sound, though weaker, more continuous. On resolving 
the brush-into its elementary parts, as before, these were found 
to occur at much shorter intervals of time than in the former 
case, but still the discharge was intermitting. 

1430. Employing a wire with a round end, the brush was still 
smaller, but, as before, separable into successive discharges. The 
sound, though feebler, was higher in pitch, being a distinct 
musical note. 

1431. The sound is, in fact, due to the recurrence of the noise 
of each separate discharge, and these, happening at intervals 
nearly equal under ordinary circumstances, cause a definite note 
to "be heard, which, rising in pitch with the increased rapidity 
and regularity of the intermitting discharges, gives a ready and 
accurate measure of the intervals, and so may he used in any 
case when the discharge is heard, even though the appearances 

a philosophical Transactions, 1834, p, 586. 



456, Brush ; — its sound — its nature [Series XII, 

may not be seen, to determine the element of time. So when, 
by bringing the hand towards a projecting rod or ball, the pitch 
of the tone produced by a brushy discharge increases, the effect 
informs us that we have increased the induction (1374.), and by 
that means increased the rapidity of the alternations of charge 
and discharge. 

1432. By using wires with finer terminations, smaller 
brushes were obtained, until they could hardly be distinguished 
as brushes ; but as long as sound was heard, the discharge 
could be ascertained by the eye to be intermitting ; and when 
the sound ceased, the light became continuous as a glow (1359. 
1405. 1526 — 1543.). 

1433. To those not accustomed to use the eye in the manner 
I have described, or, in cases where the recurrence is too .quick 
for any unassisted eye, the beautiful revolving mirror of Pro- 
fessor Wheatstone* will be useful for such developments of 
condition as those mentioned above. Another excellent process 
is to produce the brush or other luminous phenomenon on the 
end of a rod held in the hand opposite to a charged positive or 
negative conductor, and then move the rod rapidly from side to 
side whilst the eye remains still. The successive discharges 
occur of course in different places, and the state of things before, 
at, and after a single coruscation or brush can be exceedingly 
well separated. 

1434. The hmsh is in ^reality a discharge between a 
bad or a non-conductor and either a conductor or another 
non-conductor. Under common circumstances, the brush is 
a discharge between a conductor and air, and I conceive it to 
take place in something like the following manner. When the 
end of an electrified rod projects into the middle of a room, 
induction takes place between it and the walls of the room, 
across the dielectric, air ; and the lines of inductive force 
accumulate upon the end in greater quantity than elsrewliere, 
or the particles of air at the end of the rod are more highly 
polarized than those at any other part of the rod, for the rea- 
sons already given (1374.). The particles of air situated 
in sections across these lines of force are least polarized in the 
sections towards the walls, and most polarized in those nearer 

* Philosophical Transactions, 1834, pp. 584, 585. 



457 


Jan. 1838.] is a discharge to air . 

to the end of the wires (1360.) : thus, it may well happen, that 
a psfrticle at the end of the wire is at a tension that will imme- 
diately terminate in discharge, whilst in those even only a few 
inches off, the tension is still beneath that point, llut sup- 
pose the rod to he charged positively, a particle of air A, fig. 
118. next it, being polarize?!, and having of course its nega- 
tive force directed towards the rod and its positn e force o\it- 
wards ; the instant that discharge takes place between the 
positive force of the particle of the rod opposite the air and 
the negative force of the particle of air towards the rod, the 
whole particle of air becomes positively electrified ; and when, 
the next instant, the discharged part of the rod resumes its 
positive state by conduction from the surface of metal behind, 
it not only acts on the particles beyond A, by throwing A into 
a polarized state again, but A itself, because of its charged 
state, exerts a distinct inductive act towards these further par- 
ticles, and the tension is consequently so much exalted between 
A and B, that discharge takes place there also, as well as again 
between the metal and A. 

1435. In addition to this effect, it has been shown, that, the 
act of discharge having once commenced, the whole operation, 
like a case of unstable equilibrium, is hastened to a conclu- 
sion (1370. 1418.), the rest of the act being facilitated in its 
occurrence, and other electricity than that which caused the 
first necessary tension hurrying tc* the spot. When, therefore, 
disruptive discharge has once commenced at the root of a brush, 
the electric force w r hich has been accumulating in the conductor 
attached to the rod, finds a more ready discharge there than 
elsewhere, and will at once follow the course marked out as 
it were for it, thus leaving the conductor in a partially dis- 
charged state, and the air about the end of the wire in a charged 
condition ; and the time necessary for restoring the full charge 
of the conductor, and the dispersion of the charged air in a 
greater or smaller degree, by the joint forces of repulsion from 
the conductor and attraction towards the walls of the room, to 
which its inductive action is directed, is just that time which 
forms the interval between brush and brush (1420. 1427. 1431. 
1447.) * 

1436, The words of this description are long, but there is 
nothing in the act or the forces on which it depends to prevent 



458 Progress of brush discharge . [Series XII. 

the discharge being instantaneous , as far as we can estimate 
and measure it. The consideration of time is, however, import- 
ant in several points of view (1418.), and in reference to dis- 
ruptive discharge, it seemed from theory far more probable 
that it might be detected in a brush than in a spark ; for in a 
brush, the particles in the line through which the discharge 
passes are in very different states as to intensity, and the dis- 
charge is already complete in its act at the root of the brush, 
before the particles at the extremity of the ramifications have 
yet attained their maximum intensity. 

1437. I consider brush discharge as, probably a successive 
effect in this way. Discharge begins at the root (1426. 1553.), 
and, extending itself in succession to all parts of the single 
brush, continues to go on at the roof and the previously formed 
parts until the whole brush is complete ; then, by the fall in 
intensity and power at the conductor, it ceases at once in all 
parts, to be renewed, when that power has risen again to a suf- 
ficient degree. But in a spark , the particles in the line of dis- 
charge being, from the circumstances, nearly alike in their in- 
tensity of polarization, suffer discharge so nearly at the same 
moment as to make the time quite insensible to us. 

3438. Mr. Wheatstone has already made experiments which 
fully illustrate this point. He found that the brush generally 
had a sensible duration, but that with its highest capabilities 
he could not detect any sucH effect in the spark *. I repeated 
his experiment on the brush, though with more imperfect means, 
to ascertain whether I could distinguish a longer duration in 
the stem or root of the brush than in the extremities, and the 
appearances were such as to make me think an effect of this 
kind was produced. 

1439. That the discharge breaks into several ramifications, 
and by them passes through portions of air alike, or nearly 
alike, as to polarization and the degree of tension the particles 
there have acquired, is a very natural result of the previous 
state of things, and rather to be expected than that the dis- 
charge should continue to' go straight out into space in a single 
line amongst * those particles which, being at a distance from 
the end o£ the rod, are in a lower state of tension than those 
which are near : and whilst we cannot but conclude, that those 
* Philosophical Transactions, 1836, pp. 586, 590, 



Jan. 1B38.] • Circumstances- of brush discharge. 459 

parts where the branches of a single brush appear, are more 
favourably circumstanced for discharge than the darker parts 
between the ramifications, we may also conclude, that in those 
parts where the light of concomitant discharge is equal, there 
the circumstances are nearly equal also. The singlo successive 
brushes are by no means of the same particular shape even 
when they are observed without displacement of the rod or 
surrounding objects (1427. 1433.), and the successive discharges 
may be considered as taking place into the mass of air around, 
through different roads at each brush, according as minute cir- 
cumstances, such as dust, &c. (1391. 1392.) may have favoured 
the course by one set of particles rather than another. 

1440. Brush discharge does not essentially require any cur- 
rent of the medium in wjiieh the brush appears : the current 
almost always occurs, but is a consequence of the brush, and 
will be considered hereafter (1562. — 1610.). On holding a 
blunt point positively charged towards uninsulated water, a 
star or glow appeared on the point, a current of air passed 
from it, and the surface of the water was depressed ; but on 
bringing the point .so near that sonorous brushes passed, then 
the current of air instantly ceased, and the surface of the water 
became level. 

1441. The discharge by a brush is not to all the particles of 
air that are near the electrified conductor from which the brush 
issues -j only those parts where the ramifications pass are elec- 
trified : the air in the central dark parts between them receives 
no charge, and, in fact, at the time of discharge, has its electric 
and inductive tension considerably lowered. Bor consider fig. 
128, to represent a single positive brush ; — the induction be- 
fore the discharge is from the end of the i*od outwards, in di- 
verging lines towards the distant conductors, as the walls of 
the room, &c., and a particle at a has polarity of a certain de- 
gree of tension, and tends with a certain force to become 
charged ; but at the moment of discharge, the air in the rami- 
fications b and d, acquiring also a positive state, opposes its in- 
fluence to that of the positive conductor on a, and the tension 
of the particle at a is therefore diminished rather than in- 
creased. The charged particles at b and d are now inductive 
bodies, but their" lines of inductive action are still outwards to- 
wards. the walls of the room ; the direction of the polarity and 



460, Charged air : — light of the brush . [Series XII. 

the tendency o£ other particles to charge from these, being go- 
verned by, or in conformity with, these lines of force. 

1442. The particles that are charged are probably very 

highly charged, but the medium being a non-conductor, they 
cannot communicate that state to their neighbours. They tra- 
vel, therefore, under the influence of^ the repulsive and attract- 
ive forces, from the charged conductor towards the nearest un- 
insulated conductor, or the nearest body in a different state to 
themselves, just as charged particles of dust would travel, and 
are then discharged ; each particle acting, in its course, as a 
centre of inductive force upon any bodies near which it may 
come. The travelling of these charged particles when they 
are numerous, causes wind and currents, but these will come 
into consideration under carrying discharge (1319. 1562. 

&c.) . 

1443. When air is said to be electrified, and it frequently as- 
sumes this state near electrical machines, it consists, according 
to my view, of a mixture Of electrified and uneleetrificd parti- 
cles, the latter being in very large proportion to the former. 
When we gather electricity from air, by a flame or by wires, it 
is either by the actual discharge of these particles, or by effects 
dependent on tlicir inductive action, a case of either kind being 
produccablc at pleasure. That the law of equality between 
the two forces or forms of force in inductive action is as strictly 
preserved in these as in other «cases, is fully shown by the fact, 
formerly stated (1173. 1174.), that, however strongly air in a 
vessel might be charged positively, there was an exactly equal 
amount of negative force on the inner surface of the vessel itself, 
for no residual portion of either the one or the other electricity 
could be obtained. 

14 14. *1 have nowhere said, nor does it follow, that the air is 
charged only where the luminous brush appears. The char- 
ging may extend beyond those parts which are visible, L e. 
particles to the right or left of the lines of light may receive 
electricity, the parts which are luminous being so only because 
much electricity is passing by them to other parts (1437.) ; 
just as in a spark discharge the light is greater as more electri- 
city passes, though it has no necessary relation to the quantity 
required to commence discharge (1370. 1420.). Hence the 
form we see in a brush may by no means represent the whole 



461 


Jan. 1838.] Brush in gases : — general nature . 

quantity of air electrified ; for an invisible portion, clothing 
the* visible form to a certain depth, may, at the same time, re- 
ceive its charge (1552.) . 

1445. Several effects which I have met with in muriatic acid 
gas tend to make me believe, that that gaseous body allows of 
a dark discharge. At tin? same time, it is quite clear from 
theory, that in some gases, the reverse of this may occur, i. e. 
that the charging of the air may not extend even so far as the 
light. We do not know as yet enough of the electric light to 
be able to state on what it depends, and it is very possible that, 
when electricity bursts forth into air, all the particles of which 
are in state of tension, light may be evolved by such as, being 
very near to, are not of, those which actually receive a charge 
at the time. 

1446. The further a bfush extends in a gas, the further no 
doubt is the charge or discharge carried forward ; but this may 
vary between different gases, and vet the intensity required for 
the first moment of discharge not vary in the same, but in some 
other proportion. Thus with respect to nitrogen and muriatic 
acid gases, the former, as far as my experiments have proceeded, 
produces far finer and larger brushes than the latter (1 158. 
1462.), but the intensity required to commence discharge is 
much higher for the muriatic acid than the nitrogen (J3D5.). 
Here again, therefore, as in many other qualities, specific dif- 
ferences arc presented by different gaseous dielectrics, and so 
prove the special relation of the latter to the act and the phe- 
nomena of induction. 

1447. To sum up these considerations respecting the cha- 
racter and condition of the brush, 1 may state that it is a spark 
to air ; a diffusion of electric force to matter, not by conduction, 
but disruptive discharge ; a dilute spark whi6h, passing to very 
badly conducting matter, frequently discharges but a small por- 
tion of the power stored up in the conductor ; for as the air 
charged reacts on the conductor, whilst the conductor, by loss 
of electricity, sinks in its force (1435.), the discharge quickly 
ceases, until by the dispersion of the charged air and the re- 
newal of the excited conditions of the conductor, circumstances 
have risen up to their first effective condition, again to cause 
discharge, and again to fall and rise. 

1448. The brush and spark gradually pass into one another. 



462 


Relation of brush and spark ;—form . [Series XII. 

Making a small ball positive by a good electrical machine with 
a large prime conductor, and approaching a large uninsulated 
discharging ball towards it, very beautiful variations from the 
spark to the brush may be obtained. The drawings df long and 
powerful sparks, given by Van Marum*, Harris +, and others, 
also indicate the same phenomena. * As far as I have observed, 
whenever the spark has been brushy in air of common press- 
ures, the whole of the electricity has not been discharged, but 
only portions of it, more or less according to circumstances ; 
whereas, whenever the effect has been a distinct spark through- 
out the whole of its course, the discharge has been perfect, 
provided no interruption had been made to it elsewhere, in the 
discharging circuit, than where the spark occurred. 

1419. When an electrical brush from an inch to six inches 
in length or more is issuing into free 'air, it has the form given, 
fig. 117. But if the hand, a ball, or any knobbed conductor be 
brought near, the extremities of the coruscations turn towards 
it and each other, and the whole assumes various forms accord- 
ing to circumstances, as in figs. 119, 120, and 121. The influ- 
ence of the circumstances in each case is easily traced, and I 
might describe it here, but that I should be ashamed to occupy 
the time of the Society in things so evident. But how beauti- 
fully does the curvature of the ramifications illustrate the cur- 
ved form of the lines of inductive force existing previous to the 
discharge ! for the former are consequences of the latter, and 
take their course, in each discharge, where the previous in- 
ductive tension had been raised to the proper degree. They 
represent these curves just as well as iron filings represent mag- 
netic curves, the visible effects in both cases being the conse- 
quences of the action of the forces in the places where the ef- 
fects appear. The phenomena, therefore, constitute additional 
and powerful testimony (1216. 1230.) to that already given in 
favour both of induction through dielectrics in curved lines 
(1231.), and of the lateral relation of these lines, by an effect 
equivalent to a repulsion producing divergence, or, as in the 
cases figured, the bulging form. 

1450. In reference to the theory of molecular inductive ac- 

* Description of the Teylerian machine, vol i. pp. 28, 32, ; vol. ii. p. 22 6, 
&c, ' 

t Philosophical Transactions, 1834, p. 243. 



463 


Jan. 1838.] Brush in rarefied air , fyc. 

tion, I may also add, the proof deducible from the long brushy 
ramifying spark which may be obtained between a small ball 
on the positive conductor of an electrical machine, and a 
larger one at a distance (1448. 1504.). What a fine illustration 
that spark affords of the previous condition of all the particles 
of the dielectric between the surfaces of discharge, and how 
unlike the appearances are to any which would be deduced 
from the theory which assumes inductive action to be action at 
a distance, in straight lines only ; and charge, as being electri- 
city retained upon the surface of conductors by the mere press- 
ure of the atmosphere ! 

1451. When the brush is obtained in rarefied air, the ap- 
pearances vary greatly, according to circumstances, and are 
exceedingly beautiful. Sotnetimes a brush may be formed of 
only six or seven branches, these being broad and highly lumi- 
nous, of a purple colour, and in some parts an inch or more 
apart: — by a spark discharge at the prime conductor (1155.) 
single brushes may be obtained at pleasure. Discharge in the 
form of a brush is favoured by rarefaction of the air, in the 
same manner and for the same reason as discharge in the form 
of a spark (1375.) ; hut in every case there is previous induc- 
tion and charge through the dielectric, and polarity of its par- 
ticles (1437.), the induction being, as in any other instance, 
alternately raised by the machine and lowered by the discharge. 
In certain experiments the rarefaction was increased to the ut- 
most degree, and the opposed conducting surfaces brought as 
near together as possible without producing glow (1529.) : the 
brushes then contracted in their lateral dimensions, and recur- 
red so rapidly as to form an apparently continuous arc of light 
from metal to metal. Still the discharge could he observed to 
intermit (1427.), so that even undep these high conditions, in- 
duction preceded each single brush, and the tense polarized 
condition of the contiguous particles was a necessary preparation 
for the discharge itself. 

1452. The brush form of disruptive discharge may bp ob- 
tained not only in air and gases, but also in much denser me- 
dia, I procured it in oil of turpentine from the end of a wire 
going through a glass tube into the fluid contained in a metal 
vessel* The brush was small and very difficult to obtain ; the 



464 Brush : — concurring ramifications. [Series XII. 

ramifications were simple, and stretched out from each other , 
diverging very much. The light was exceedingly feeble, a per- 
fectly dark room being required for its observation. When a 
few solid particles, as of dust or silk, were in the liquid, the 
brush was produced with much greater facility. 

1453. The running together or Coalescence of different lines 
of discharge (1412.) is very beautifully shown in the brush in 
air. This point may present a little difficulty to those who arc 
not accustomed to see in every discharge an equal exertion of 
power in opposite directions, a positive brush being considered 
by such (perhaps in consequence of the common phrase direc- 
tion of a current ) as indicating a breaking forth in different di- 
rections of the original force, rather than a tendency to conver- 
gence and union in one line of passage. But the ordinary case 
of the brush may be compared, for fts illustration, with that in 
which, by holding the knuckle opposite to highly excited glass, 
a discharge occurs, the ramifications of a brush then leading 
from the glass and converging into a spark on the knuckle. 
Though a difficult experiment to make, it is possible to obtain 
discharge between highly excited shell-lac and the excited glass 
of a machine : when the discharge passes, it is, from the nature 
of the charged bodies, brush at each end and spark in the mid- 
dle, beautifully illustrating that tendency of discharge to facili- 
tate like action, which I have described in a former page (1418.) . 

1154. The brush has specific characters in different gases, 
indicating a relation to the particles of these bodies even in a 
stronger degree than the spark (1422. 1423.). This effect is 
in strong contrast with the non-variation caused by the use of 
different substances as conductors from which the brushes are 
to originate. Thus, using such bodies as wood, card, charcoal, 
nitre, citric acid, oxalic acid, oxide of lead, chloride of lead, 
carbonate of potassa, potassa fusa, strong solution of potash, 
oil of vitriol, sulphur, sulphuret of antimony, and haematite, no 
variation in the character of the brushes was obtained, except 
that (dependent upon their effect as better or worse conduc- 
tors) of causing discharge with more or less readiness and 
quickness from the machine *. 

* Exception must, of course, he made of those cases where the root of the 
brush, becoming a spark, causes a little diffusion or even decomposition of the 
matter there, and so gains more or lees of a particular colour at that part. 



465 


Jan. 1838.] Brush ; — in rare air — in gases . 

1455. The following are a few of the effects I observed in 
different gases at the positively charged surfaces, and with at- 
mospheres varying in their pressure. The general effect of rare- 
faction was the same for all the gases : at first, sparks passed ; 
these gradually were converted into brushes, which became 
larger and more distinct in their ramifications, until, upon fur- 
ther rarefaction, the latter began to collapse and draw in upon 
each other, till they formed a stream across from conductor to 
conductor : then a few lateral streams shot out towards the 
glass of the vessel from the conductors ; these became thick 
and soft in appearance, and were succeeded by the full con- 
stant glow which covered the discharging wire. The pheno- 
mena varied with the size of the vessel (11*77.), the degree of 
rarefaction, and the discharge of electricity from the machine. 
When the latter was in successive sparks, they were most beau- 
tiful, the effect of a spark from a small machine being equal to, 
and often surpassing, that produced by the constant discharge 
of a far more' powerful one. 

1456. Air . — Fine positive brushes arc easily obtained in air 
at common pressures, and possess the well-known purplish 
light. When the air is rarefied, the ramifications are very long, 
filling the globe (1477.); the light is greatly increased, and is 
of a beautiful purple colour, with ail occasional rose tint in it. 

1457. Oxygen. — At common pressures, the brush is very 
close and compressed, and of a dull whitish colour. In rare- 
fied oxygen, the form and appearance are better, the colour 
somewhat purplish, but all the characters very poor compared 
to those in air. 

1458. Nitrogen gives brushes with great facility at the positive 
surface, far beyond any other gas I have tried : they are almost 
always fine in form, light, and colour, and in rarefied nitrogen 
are magnificent. They surpass the discharges in any other gas 
as to the quantity of light evolved. 

1459. Hydrogen, at common pressures, gave a better brush 
than oxygen, but did not equal nitrogen ; the colour was green- 
ish gray. In rarefied hydrogen, the ramifications were very 
fine in form and distinctness, but pale in colour, with a soft and 
vejvety appearance, and not at all equal to those in nitrogen. 
In the rarest state of the gas, the colour of the light was a pale 
gray green. 



466 


Brush in different gases . 


[Series XII. 


1460. Coal gas . — The brushes were rather difficult to pro- 
duce, the contrast with nitrogen being great in this respect. 
They were short and strong, generally of a greenish colour, 
and possessing much of the spark character : for, occurring on 
both the positive and negative terminations, often when there 
was a dark interval of some length between the two brushes, 
still the quick, sharp sound of the spark was produced, .as if 
the discharge had been sudden through this gas, and partaking, 
in that respect, of the character of a, spark. In rare coal gas, 
the brush forms were better, but the light very poor and the 
colour gray. 

1461. Carbonic acid gas produces a very poor brush at 
common pressures, as regards either size, light, or colour ; and 
this is probably connected with the pendency which this gas has 
to discharge the electricity as a spark (1422.) . In rarefied car- 
bonic acid, the brush is better in form, but weak as to light, being 
of a dull greenish or purplish hue, varying with the pressure and 
other circumstances. 

1462. Muriatic acicl gas . — It is very difficult to obtain the 
brush in this gas at common pressures. On gradually increasing 
the distance of the rounded ends, the sparks suddenly ceased 
when the interval was about an inch, and the discharge, which 
was still through the gas in the globe, was silent and dark. 
Occasionally a very short brush could for a few moments be 
obtained, but it quickly disappeared. Even when the inter- 
mitting spark current (1455.) from the machine was used, still 
I could only with difficulty obtain a brush, and that very short, 
though I used rods with rounded terminations (about 0 2 5 of an 
inch in diameter) which had before given them most freely in 
air and nitrogen. During the time of this difficulty with the 
muriatic gas, magnificent brushes were passing off from different 
parts of the machine into the surrounding air. On rarefying 
the gas, the formation of the brush was facilitated, but it was 
generally of a low squat form, very poor in light, and very 
similar on both the positive and negative surfaces; On rare- 
fying the gas still more, a few large ramifications were obtained 
of a pale bluish colour, utterly unlike those in nitrogen. 


1463. In all the gases, the different forms of disruptive dis- 



Jan. 1838.] Variation of its characters ; lightning. 467 

charge may be linked , together and gradually traced from one 
extreme to the other, i . e . from the spark to the glow (1405. 
1 526.), or, it may be, to a still further condition to be called dark 
discharge (1544 — 1560.) ; but it is nevertheless very surprising 
to see what a specific character each keeps whilst under the pre- 
dominance of the general hiw. Thus, in muriatic acid, the 
brush is very difficult to obtain, and there comes in its place 
almost a dark discharge, partaking of the readiness of the spark 
action. Moreover* in muriatic acid, I have never observed the 
spark with any dark interval in it. In nitrogen, the spark 
readily changes its character into that of brush. In carbonic 
acid gas, there seems to be a facility to occasion spark discharge, 
whilst yet that gas is unlike nitrogen in the facility of the latter 
to form brushes, and unlike muriatic acid in its own facility to 
continue the spark. These differences add further force, first 
to the observations already made respecting the spark in various 
gases (1422. 1423.), and then, to the proofs dcdueiblc from it, 
of the relation of the electrical forces to the particles of 
matter. 

1464. The peculiar characters of nitrogen in relation to the 
electric discharge (1422. 1458.) must, evidently, have an im- 
portant influence over the form and even the occurrence of 
lightning. Being that gas which most readily produces corus- 
cations, and, by them, extends discharge to a greater distance 
than any other gas tried, it is also *that which constitutes four- 
fifths of our atmosphere ; and as in atmospheric electrical phe- 
nomena, one, and sometimes both the inductive forces are re- 
sident on ' the particles of the air, which, though probably 
affected as to conducting power by the aqueous particles in it, 
cannot he considered as a good conductor; so the peculiar power 
possessed by nitrogen, to originate and effect discharge fin the 
form >of a brush or of ramifications, has, prdoably, an import- 
ant relation to its electrical service in nature, as it most seriously 
affects the character and condition of the discharge when made. 
The whole subject of discharge from and through gases is of 
great interest, and, if only in reference to atmospheric electricity, 
deserves extensive and close experimental investigation. 


2 u2 



468 


Positive and negative discharge . [Series XII. 


Difference of discharge at the positive and negative conducting 

surfaces . 

1465. I have avoided speaking of this well-known pheno- 
menon more than was quite necessary, that I might bring to- 
gether here what I have to say on the subject. When the 
brush discharge is observed in air at the positive and negative 
surfaces, there is a very remarkable difference, the true and full 
comprehension of which would, no doubt, be of the utmost im- 
portance to the physics of electricity; it would throw great light 
on our present subject, i. e. the molecular action of dielectrics 
under induction, and its consequences ; and seems very open to, 
and accessible by, experimental inquiry. 

1466. The difference in questiop used to be expressed in 
former times by saying, that a point charged positively gave 
brushes into the air, whilst the same point charged negatively 
gave a star. This is true only of bad conductors, or of metallic 
conductors charged intermittingly, or otherwise controlled by 
collateral induction. If metallic points project freely into tlic 
air, the positive and negative light upon them differ very little 
in appearance, and the difference can be observed only upon 
close examination. 

1467. The effect varies exceedingly under different circum- 
stances, but, as we must set out from some position, may per- 
haps be stated thus : if a metallic wire with a rounded termi- 
nation in free air be used to produce the brushy discharge, then 
the brushes obtained when the wire is charged negatively are 
very poor and small, by comparison with those produced when 
the charge is positive. Or if a large metal ball connected with 
the electrical machine be charged positively , and a fine unin- 
sulated point be gradually brought towards it, a star appears 
on the point when at a considerable distance, which, though it 
becomes brighter, does not change its form of a star until it is 
close up to the ball : whereas, if the ball be charged negatively, 
the point at a considerable distance has a star on it ap before ; 
but when brought nearer, (in my case to the distance of 1£ 
inch,) a brush formed on it, extending to the negative ball ; 
and when still nearer, (at £ of an inch distance,) the brush 
ceased, and bright sparks passed. These variations, I believe. 



469 


Jan. 1838.] Characters of the negative brush. 

include the whole series of differences, and they seem to show 
at once, that the negative surface tends to retain its discharging 
character unchanged, whilst the positive surface, under similar 
circumstances, permits of great variation. 

1468. There are several points in the character of the nega- 
tive discharge to air which it is irnpbrtant to observe. A metal 
rod, 0*3 of an inch in diameter, with a rounded end projecting 
into the air, was charged negatively, and gave a short noisy 
brush (fig. 122.). It was ascertained both by sight (1 127. 1 133.) 
and sound (1431.), that the successive discharges were very 
rapid in their recurrence, being seven or eight times more nume- 
rous in the same period than those produced when the rod was 
charged positively to an equal degree. When the rod was posi- 
tive, it was easy, by workiiig the machine a little quicker, to 
replace the brush by a glow (1105. 1103.), but when it was 
negative no efforts could produce this change. Even by bring- 
ing the hand opposite the wire, the only effect was to increase 
the number of brush discharges in a given period, raising at the 
same time the sound to a higher pitch. 

1469. A point opposite the negative brush exhibited a star, 
and as it was approximated caused the size and sound of the 
negative brush to diminish, and at last, to cease, leaving the 
negative end silent and dark, yet effective as to discharge. 

1170. When the round end of a, smaller wire (fig. 123.) was 
advanced towards the negative brush, it (becoming positive by 
induction) exhibited the quiet glow at 8 inches distance, the 
negative brush continuing. When nearer, the pitch of the 
sound of the negative brush rose, indicating quicker intermit- 
tences (1431.) ; still nearer the positive end threw off ramifi- 
cations and distinct brushes ; at the same time the negative 
brush contracted in its lateral directions and collected together, 
giving a peculiar narrow longish brush, in shape like a hair pen- 
cil, the two brushes existing at once, but very different in their 
form and appearance, and especially in the more rapid recur- 
rence of the negative discharges than of the positive. On using 
a smaller positive wire for the same experiment, the glow first 
appeared on it, and then the brush, the negative brush being 
affected at the same time ; and the two at one distance became 
exceedingly alike in appearance, and the sounds* I thought, were 
i& unison ; at all events they were in harmony, so that the inter- 



470 


Positive and negative brushes . [Series XII. 

missions of discharge were either isochronous, or a simple ratio 
existed between the intervals. With a higher action of the 
machine, the wires being retained unaltered, the negative sur- 
face became dark and silent, and a glow appeared on the posi- 
tive one. A still higher action changed the latter into a spark. 
Finer positive wires gave other variations of these effects, the 
description of which I must not allow myself to go into here. 

1471. A thinner rod was now connected with the negative 
conductor in place of the larger one (1468.), its termination 
being gradually diminished to a blunt point, as in fig. 124 ; and 
it was beautiful to observe that, notwithstanding the variation 
of the brush, the same general order of effects was produced. 
The end gave a small sonorous negative brush, which the 
approach of the hand or a large conducting surface did not alter, 
until it was so near as to produce a spark. A fine point oppo- 
site to it was luminous at a distance ; being nearer it did not 
destroy the light and sound of the negative brush, but only 
tended to have a brush produced on itself, which, at a still 
less distance, passed into a spark joining the two surfaces. 

1472. When the distinct negative and positive brushes are 
produced simultaneously in relation to each other in air, the 
former almost always has a contracted form, as in fig. 125., 
very much indeed resembling the figure which the positive 
brush itself has when influenced by the lateral vicinity of posi- 
tive parts acting by induction. Thus a brush issuing from a 
point in the re-entering angle of a positive conductor has the 
same compressed form (fig. 126.). 

1473. The character of the negative brush is not affected by 
the chemical nature of the substances of the conductors (1454). 
but oidy by their possession of the conducting power in a greater 
or smaller degree: 

1474. Rarefaction of common air about a negative ball or 
blunt point facilitated the development of the negative brush, 
the effect being, I think, greater than on a positive brush, 
though great on both. Extensive ramifications could be ob- 
tained from a ball or end electrified Negatively to the plate of 
the air-pump on which the jar containing it stood. 

1475. A very important variation of the relative forms and 
conditions of the positive and negative "brush takes place on 
varying the dielectric in which they are produced. The differ- 



471 


Jan. 1838.] compared in different gases. 

ence is so very great that it points to a specific relation of this 
form of discharge to the particular gas in which it takes place, 
and opposes the idea that gases are but obstructions to the 
discharge, acting one like another and merely in proportion to 
their pressure (1377.) . 

1476. In air, the superiority of the positive brush is well 
known (1467. 1472.). In nitrogen, it is as great or even greater 
than in air (1458.). In hydrogen, the positive brush loses a part 
of its superiority, not being so good as in nitrogen or air; 
whilst the negative brush does not seem injured (1159.). In 
oxygen , the positive brush is compressed and poor (1157) ; 
whilst the negative did not become less : the two were so alike 
that the eye frequently could not tell one from the other, and 
this similarity continued wtycn the oxygen was gradually rare- 
fied. In coal gas , the brushes arc difficult of production as 
compared to nitrogen (1160.), and the positive not much supe- 
rior to the negative in its character, either at common or low 
pressures. In carbonic acid gas , this approximation of cha- 
racter also occurred. In muriatic acid gas, the positive brush 
was very little hotter than the negative, and both difficult to 
produce (1462.) as compared with the facility in nitrogen or air. 

1177. These experiments were made with rods of brass about 
a quarter of an inch thick having rounded ends, these being 
opposed in a glass globe 7 inches in diameter, containing Ihe gas 
to be experimented with. The electric machine was used to com- 
municate directly, sometimes the positive, and sometimes the 
negative, state, to the rod in connection with it. 

1478. Thus we see that, notwithstanding there is a general 
difference in favour of the superiority of the positive brush 
over the negative, that difference is at its maximum in nitrogen 
and air; whilst in carbonic acid, muriatic acid, coal gas, and 
Oxygen, it diminishes, and at last almost disappears, So that 
in this particular effect, as in all others yet examined, the evi- 
dence is in favour of that view which refers the results to a di- 
rect relation of the electric forces with the molecules of the 
matter concerned in the action (1421. 1423. 1463.). Even 
when special phenomena arise under the operation of the ge- 
neral law, the theory adopted seems fully competent to meet 
the case. 

1479. Before I proceed further in tracing the probable 



4 72 # Positive and negative brushes . [Series XII 

cause of the difference between the positive and negative brush 
discharge, I wish to know the results of a few experiments which 
are in course of preparation : and thinking this Series of Re- 
searches long enough, I shall here close it with the expectation 
of being able in a few weeks to renew the inquiry, and entirely 
redeem my pledge (1306.), 

Royal Institution , 

December 2‘drd, 1837. 



473 


THIRTEENTH SERIES. 

§ 18. On Induction (continued) . *[} ix. Disruptive discharge 

(continued) — Peculiarities of positive and negative discharge 
either as spark or brush — Glow discharge — Dark discharge . 
If x. Convection , or carrying discharge . If xi. Relation of 
a vacuum to electrical phenomena, § 19, Nature of the 
electrical current . 

Received February 22, — Read March 15, 18,38. 

If ix. Disruptive discharge ( continued ). 

1480. Let us now direct our attention to the general differ- 
ence of the positive and negative disruptive discharge, with 
the object of tracing, as far as possible, the cause of that dif- 
ference, and whether it depends ou the charged conductors 
principally, or on the interposed dielectric ; and as it appears 
to be great in air and nitrogen (1 17(h), let us observe the phe- 
nomena in air first. 

1481. The general ease is best understood by a reference to 
surfaces of considerable size rather than to points, which in- 
volve (as a secondary effect) the formation of currents (1502.). 
My investigation, therefore, was carried on with balls and ter- 
minations of different diameters, and the following are some of 
the principal results. 

1482. If two balls of very different dimensions, as for 
instance one half an inch, and the other three inches, in dia- 
meter, be arranged at the ends of rods so that either can be 
electrified by a machine and made to discharge by sparks to 
the other, which is at the same time uninsulated ; then, as is 
well known, far longer sparks are obtained when the small 
ball is positive and the large ball negative, than when the 
small ball is negative and the large ball positive. In the former 
case, the sparks are 10 or 12 inches in length; in the latter, 
an inch or an inch and a half only. 

1483. But previous to the description of further experi- 



474 Nomenclature. [Series XIII, 

ments, I will mention two words, for which with many others I 
am indebted to a friend, and which I think it would be expe- 
dient to introduce and use. It is important in ordinary induc- 
tive action, to distinguish at which charged surface the induc- 
tion originates and is sustained : i. e. if two or more metallic 
balls, or other masses of matter, are in inductive relation, to 
express which are charged originally, and which are brought 
by them into the opposite electrical condition. I propose to 
call those bodies which are originally charged, inductric 
bodies ; and those which assume the opposite state, in conse- 
quence of the induction, induct eous bodies. This distinction 
is not needful because there is any difference between the 
sums of the inductric and the inducteous forces ; but princi- 
pally because, when a ball A is induptric, it not merely brings 
a ball B, which is opposite to it, into an inducteous state, but 
also many other surrounding conductors, though some of 
them may be a considerable distance off, and the consequence 
is, that the balls do not bear the same precise relation to each 
other when, first one, and then the other, is made the induc- 
tric ball; though, in each case, the same ball be made to as- 
sume the same state. 

1484. Another liberty which 1 may also occasionally take in 
language I will explain and limit. It is that of calling a parti- 
cular spark or brush, positive or negative , according as it may 
be considered as originating at a positive or a negative sur- 
face. We speak of the brush as positive or negative when it 
shoots out from surfaces previously in those states ; and the 
experiments of Mr. Wheatstone go to prove that it really 
begins at the charged surface, and from thence extends into 
the air (1437. 1438.) or other dielectric. According to my 
view, sparks also originate or are determined at one particular 
spot (1370.), namely, that where the tension first rises up to 
the maximum degree; and when this can be determined, as 
in the simultaneous use of large and small balls, in which case 
the discharge begins or is determined by the latter, I would 
oall that discharge which passes at once , a positive spark, if it 
was at the positive surface that the maximum intensity was 
first obtained ; or a negative spark, if that necessary intensity 
was first obtained at the negative surface. 



Feb. 1838.] ^ Positive and negative discharge compared. 475 

J.485. An apparatus was arranged, as in fig. 129 (Plate 
VIII.) : A and B, were brass balls of very different diameters 
attached to metal rods, moving through sockets on insulating 
pillars, so that the distance between the balls could be varied 
at pleasure. The large b^Ll A, 2 inches in diameter, was con- 
nected with an insulated brass conductor, m hich could be ren- 
dered positive or negative directly from a cylinder machine : 
the small ball B, 0 25 of an inch in diameter, was connected 
with a discharging train (292.) and perfectly uninsulated. The 
brass rods sustaining the balls were 0*2 of an inch in. thick- 
ness. 

1486. When the large ball was positive and induetrie (1 183.), 
negative sparks occurred until the interval was 0*19 of an 
inch; then mixed brush # and spark between that and 0*51; 
and from 0*52 and upwards, negative brush alone. When the 
large ball was made negative and induetrie, then positive spark 
alone occurred until the interval was as great as 1*15 inches; 
spark and brush from that up to 1*55; and to have the posi- 
tive brush alone, it required an interval of at least 1*65 
inches. 

1487. The balls A and B were now changed for each other. 
Then making the small ball B induetrie positively, the positive 
sparks alone continued only up to 0*67 ; spark and brush 
occurred from 0*68 up to 0'72; and positive brush alone from 
0*74 and upwards. Rendering the small ball B induetrie and 
negative, negative sparks alone occurred up to 0* 10 ; then 
spark and brush at 0*42; whilst from 0*11 and upwards the 
noisy negative brush alone took place. 

1488. We thus find a great difference as the balls are ren- 
dered induetrie or inductcous; the small ball rendered posi- 
tive inducteously giving a spark nearly twice as long as that 
produced when it was charged positive inductrically, and a 
corresponding difference, though not, under the circumstances, 
to the same extent, was manifest, when it was rendered nega- 
tive .* 

1489. Other results are, that the small ball rendered posi- 
tive gives a mpeh longer spark than when it is rendered nega- 
tive, and that the small ball rendered negative gives a brush 

* For similar experiments on different gases, see 1518. — Dec. 1838. 



476 Positive and negative discharges . [Series XIII. 

more readily than when positive, in relation to the effect pro- 
duced by increasing the distance between the two balls. 

1490. When the interval was below 0 4 of an inch, so that 
the small ball should give sparks, whether positive or nega- 
tive, I could not observe that theye was any constant differ- 
ence, either in their ready occurrence or the number which 
passed in a given time. But when the interval was such that 
the small ball when negative gave a brush, then the discharges 
from it, as separate negative brushes, were far more numerous 
than the corresponding discharges from it when rendered 
positive, whether those positive discharges were as sparks or 
brushes. 

1491. It is, therefore, evident that, when a ball is dischar- 
ging electricity in the form of brushes, the brushes are far more 
numerous, and each contains or carries off far less electric 
force when the electricity so discharged is negative, than when 
it is positive/ 

1492. In all such experiments as those described, the point 
of change from spark to brush is very much governed by the 
working state of the electrical machine and the size of the con- 
ductor connected with the discharging ball. If the machine 
be in strong action and the conductor large, so that much 
power is accumulated quickly for each discharge, then the in- 
terval is greater at w hich the sparks are replaced by brushes ; 
but the general effect is the same.* 

1493. These results, though indicative of very striking and 
peculiar relations of the electric force or forces, do not show 
the relative degrees of charge which the small ball acquires 
before discharge occurs, i. e. they do not tell whether it acquires 
a higher condition in the negative, or in the positive state, im- 
mediately preceding that discharge. To illustrate this import- 
ant point I arranged two places of discharge as represented, 
fig. 130. A and D are brass balls 2 inches in diameter, B and C 
are smaller brass balls 0 25 of an inch in diameter ; the forks 
L and R supporting them were of brass wire 0*2 of an inch in 
diameter : the space between the large and small ball on the 
same fork was 5 inches, that the two places of discharge n and 
o might he sufficiently removed from each other's influence. 

* For similar experiments in different gases, see 1610 — 1617, — Pec . 1838. 



Feb. 1838.] Their relative facility in air. 4<T¥ 

The fork L was connected with a projecting cylindrical con- 
ductor, which could he rendered positive or negative at plea- 
sure, by an electrical machine, and the fork H was attached to 
another conductor, but thrown into an uninsulated state by 
connection with a discharging train (292.). The two intervals 
or places of discharge n and o could be varied at pleasure, 
their extent being measured by the occasional introduction of 
a diagonal scale. It is evident, that, as the balls A and B 
connected with the same conductor are always charged at 
once, and that discharge may take place to either of the balls 
connected with the discharging train, the intervals of discharge 
n and o may be properly compared to each other, as respects 
the influence of large and small balls when charged positively 
and negatively in air. 

1494. When the intervals n and o were each made = 0*9 of 
an inch, and the balls A and B inductive positively , the dis- 
charge was all at n from the small bail of the conductor to the 
large ball pf the discharging train, and mostly by positive 
brush, though once by a spark. When the balls A and B 
were made inductric negatively , the discharge was still from 
the same small ball, at n, by a constant negative brush. 

1495. I diminished the intervals n and o to 0 f> of an inch. 
When A and B were inductric positively , all the discharge 
was at n as a positive brush : when A and B were inductric 
negatively , still all the discharge was at n , as a negative brush. 

1496. The facility of discharge at the positive and negative 
small balls, therefore, did not appear to be very different. If 
a difference had existed, there were always two small balls, one 
in each state, that the discharge might happen at that most 
favourable to the effect. The only difference was, that one 
was in the inductric, and the other in the inducteoixs state, 
but whichsoever happened for the time to be in that state, 
whether positive or negative, had the advantage. 

1497. To counteract this interfering influence, I made the 
interval n =« 0*79 and interval o = 0*58 of an inch. Then, 
when the balls A and B were inductric positive, the discharge 
was about equal at both intervals. When, on the other hand, 
the balls A and B were inductric negative, there was discharge, 
still at both, but most at n, as if the small ball negative could 
discharge a little easier than the same ball positive . 



478 Positive and negat[ve discharges. [Series XIII. 

1498. The small balls and terminations used in these and 
similar experiments may very correctly be compared, in their 
action, to the same balls and ends when electrified in free air 
at a much greater distance from conductors, than they were in 
those cases from each other. In the first place, the discharge, 
oven when as a spark, is, according to my view, determined, 
and, so to speak, begins at a spot on the surface of the small 
ball (1374.), occurring when the intensity there has risen up 
to a certain maximum degree (1370.) ; this determination of 
discharge at a particular spot first, being easily traced from 
the spark into the brush, by increasing the distance, so as, at 
last, even to render the time evident which is necessary for 
the production of the effect (1436. 1438.). In the next place, 
the large balls which I have used might be replaced by larger 
balls at a still greater distance, and so, by successive degrees, 
may be considered as passing into the sides of the rooms ; 
these being under general circumstances the inducteous bodies, 
whilst the small ball rendered either positive or negative is the 
indue trie body. 

1499. But, as has long been recognised, the small ball is 
only a blunt end, and, electrically speaking, a point only a 
small ball ; so that when a point or blunt end is throwing out 
its brushes into the air, it is acting exactly as the small balls 
have acted in the experiments already described, and by virtue 
of the same properties and relations. 

1500. It may very properly be said with respect to the ex- 
periments, that the large negative ball is as essential to the 
discharge as the small positive ball, and also that the large ne- 
gative ball shows as much superiority over the large positive 
ball (which is inefficient in causing a spark from its opposed 
small negative ball) as the small positive ball does over the 
small negative ball ; and probably when we understand the real 
cause of the difference, and refer it rather to the condition of 
the particles of the dielectric than to the sizes of the conduct- 
ing balls, we may find much importance in such an observation. 
But for the present, and whilst engaged in investigating the 
point, we may admit, what is the fact, that the forces are of 
higher intensity at the surfaces of the smaller balls than at 
those of the larger (1372. 1374.) ; that the former, therefore, 
determine the discharge, by first rising up to that exalted con- 



479 


Feb. 1838.] Their relation to the interposed particles . 

dition which is necessary for it ; and that, whether brought to 
th& condition by induction towards the walls of a room or the 
large balls I have used, these may fairly be compared one with 
the other in their influence and actions. 

3501. The conclusions I arrive at are : first, that when two 
equal small conducting surfaces equally placed in air arc elec- 
trified, one positively and the other negatively, that which is 
negative can discharge to the air at a tension a little lower than 
that required for the positive ball : second, that when dis- 
charge does take place, much more passes at each time from 
the positive than from the negative surface (1491.). The last 
conclusion is very abundantly proved by the optical analysis of 
the positive and negative brushes already described (1408.), 
the latter set of discharges being found to recur five or vsix 
times oftener than the former*. 

1502. If, now, a small ball be made to give brushes or 
brushy sparks by a powerful machine, we can, in some mea- 
sure, understand and relate the difference perceived when it is 
rendered positive or negative. It is known to give when posi- 
tive a much larger and more powerful spark than when nega- 
tive, and with greater facility (1 182.) ; in fact, the spark, 
although it takes away so much more electricity at once, com- 
mences at a tension higher only in a small degree, if at all. On 
the other hand, if rendered negative, though discharge may 
commence at a lower degree, it continues but for a very short 
period, very little electricity passing away each time. These 
circumstances are directly related ; for tiie extent to which the 
positive spark can reach, and the size and extent of the posi- 
tive brush, are consequences of the capability which exists of 
much electricity passing off at one discharge from the positive 
surface (1468. 1501.). 

1503. But to refer these effects only to fhe form and size of 
the conductor, would, according to my notion of induction, he 
a very imperfect mode of viewing the whole question (1523. 
1600.). I apprehend that the effects are due altogether to the 
mode in which the particles of the Interposed dielectric polar- 
ize, anil have already given some experimental indications of 

* A very excellent mode of examining the relation of small positive and 
negative surfaces would be by the use of drops of gum water, solutions, or 
-other liquids. See onwards (1581. 1593.). 



480 Positive and negative discharge . [Series XIII. 

the differences presented by different electrics in this respect 
(1475. 1476.). The modes of polarization, as I shall have 'oc- 
casion hereafter to show, may be very diverse in different di- 
electrics. With respect to common air, what seems to be the 
consequence of a superiority in the positive force at the sur- 
face of the small ball, may be due to the more exalted condi- 
tion of the negative polarity of the particles of air, or of the 
nitrogen in it (the negative part being, perhaps, more com- 
pressed, whilst the. positive part is more diffuse, or vice versd 
(1687. &c.)) ; for such a condition could determine certain 
effects at the positive ball which would not take place to the 
same degree at the negative ball, just as well as if the positive 
ball had possessed some special and independent power of its 
own. 

1504. The opinion, that the effects are more likely to be de- 
pendent upon the dielectric than the ball, is supported by the 
character of the two discharges. If a small positive ball be 
throwing off brushes with ramifications ten inches long, how 
can the ball affect that part of a ramification which is five 
inches from it? Yet the portion beyond that place has the 
same character as that preceding it, and no doubt has that 
character impressed by the same general principle and law. 
Looking upon the action of the contiguous particles of a dielec- 
tric as fully proved, I see, in such a ramification, a propaga- 
tion of discharge from parti de to particle, each doing for the 
one next it what was done for it by the preceding particle, and 
what was done for the first particle by the charged metal 
against which it was situated. 

1505. With respect to the general condition and relations of 
the positive and negative brushes in dense or rare air, or in 
other -media and gases, if they are produced at different times 
and places, they ard of course independent of each other. But 
when they are produced from opposed ends or balls at the 
same time, in the same vessel of gas (1470. 1477.), they are 
frequently related ; and circumstances may be so arranged that 
they shall be isochronous, occurring in equal numbers in equal 
times ; or shall occur in multiples, i. e. with two or three ne- 
gatives to one positive ; or shall alternate, or be quite irregular. 
All these variations I have witnessed ; and when it is considered 
that the air in the vessel, and also the glass of the vessel, can 



Feb. 1838.] Positive <5f negative d scharge in different gases. 481 

take a momentary charge, it is easy to comprehend their ge~ 
neral nature and cause. 

1500. Similar experiments to those in air (1 185. 1493.) were 
made in different gases, the results of which I will describe as 
briefly as possible. The Apparatus is represented fig. 131., 
consisting of a bell-glass eleven inches in diameter at the widest 
part, and ten and a half inches high up to the' bottom of the 
neck. The balls arc lettered, as in fig. 130., and are in the 
same relation to each other ; but A and 11 were on separate 
sliding wires, which, however, were generally joined by a cross 
wire, w } above, and that connected with the brass conductor, 
which received its positive or negative charge from the ma- 
chine. The rods of* A and 11 were graduated at the part 
moving through the stuffing-box, so that the application of a 
diagonal scale applied there, told what nas the distance be- 
tween these halls and those beneath them. As to the position 
of the balls in the jar, and their relation to each other, C and 
D were three and a quarter inches apart, their height above 
the pump plate five inches, and the distance between any of 
the balls and the glass of the jar one inch and three quarters 
at least, and generally more. The balls A and l) were two 
inches in diameter, as before (1 193.) ; the balls II and C only 
0T5 of an inch in diameter. 

Another apparatus uas occasionally used in connection with 
that just described, being an open discharger (fig. 132.), by 
which a comparison of the discharge in air and that in gases 
could be obtained. The balls E and F, each 0*0 of an inch in 
diameter, were connected with sliding rods and other balls, and 
were insulated. When used for comparison, the brass con- 
ductor was associated at the same time with the bulls A and 
B of figure 131 and ball E of this apparatus (fig. 132) ; whilst 
the balls C, D and F were connected with the discharging train. 

1507. I will first tabulate the results as to the restraining 
power of the gases over discharge. The balls A and C (fig. 
131.) were thrown out of action by distance, and the effects 
at B and D, or the interval n in the gas, compared with those 
at the interval p in* the air, between E and F (fig. 132.). The 
Table sufficiently explains itself. It will bo understood that 
all discharge was in the air, when the interval there was less 

2 i 



482 Positive and negative discharge in gases . [Series XIII. 

than that expressed in the first or third columns of figures^; 
and all the discharge in the gas, when the interval in air was 
greater than that in the second or fourth column of figures. 
At intermediate distances the discharge was occasionally at 
both places, i . e. sometimes in the air, sometimes in the gas. 



Interval p in parts of an inch. j 

Constant interval n between 
B and D s 1 inch. 

When the small ball B was in- 
ductric and positive the discharge 
was all 

at p in at n in the 

air before. gas after. 

When the small ball B was in- 
ductric and negative the discharge 
was all 

at p in at n in the 

air before. gas after. 

In Air . . . 

In Nitrogen 

In Oxygen 

In Hydrogen 

In Coal gaa 

In Carbonic acid .... 

<?40 050 

0*30 0G5 

0-33 0*52 

0*20 0-40 

0*20 0*00 

004 1*30 

0*28 5*33 

0*31 0*40 

0*27 0*30 

0*22 0*24 

0*20 0*27 

0*30 0*45 


1508. These results are the same generally, as far as they 
go, as those of the like nature in the last series (1388.), and 
confirm the conclusion that different gases restrain discharge 
in very different proportions. They are probably not so good 
as the former ones, for the glass jar not being varnished, acted 
irregularly, sometimes taking a certain degree of charge as a 
non-conductor, and at other times acting as a conductor in the 
conveyance and derangement of that charge. Another cause 
of difference in the ratios is, no doubt, the relative sizes of the 
discharge balls in air; in the former case they were of very 
different size, here they were alike. 

1509. In future experiments intended to have the character 
of accuracy, the influence of these circumstances ought to be 
ascertained, and, above all things, the gases themselves ought 
to ber contained in vessels of metal, and not of glass, 

1510. The next set of results are those obtained when the 
intervals n and o (fig. 131.) were made equal to each other, and 
relate to the greater facility of discharge at the small ball, when 
rendered positive or negative (1493,). 

1511. In air, with the intervals = 04 of an inch, A and B 
being inductric and positive, discharge was nearly equal at n 
and o ; when A and B were inductric and negative, the dis- 
charge was mostly at n by negative brush. When the intervals 




483 


Feb. 1838.] Results in diff rent gases . 

were — 0*8 of an inch, with A and B inductric positively, all 
discharge was at n by positive brush ; with A and B inductric 
negatively, all the discharge was at n by a negative brush. It 
is doubtful, therefore, from these results, whether the negative 
ball has any greater facility than the positive. 

1512. Nitrogen . — Intervals n and o = 0*4 of an inch : A, B 
inductric positive, discharge at both intervals, most at w, by 
positive sparks ; A, B inductric negative, discharge ctpial at n 
and o. The intervals made = O' 8 of an inch : A, B inductric 
positive, discharge all at n by positive brush; A, 15 inductric 
negative, discharge most at o by positive brush. In this gas, 
therefore, though the difference is not decisive, it would seem 
that the positive small ball caused the most ready discharge. 

1513. Oxygen. — Intervals, n and o — 0*4 of an inch: A, B 
inductric positive, discharge nearly equal ; inductric negative, 
discharge mostly at n by negative brush. Math' the intervals 
== 0*8 of an inch: A, B inductric positive, discharge both at n 
and o ; inductric negative, discharge all at o by negative brush. 
So here the negative small ball seems to give the most ready 
discharge. 

1514. Hydrogen . — Intervals wand o — 01 of an inch : A, B 
inductric positive, discharge nearly equal : inductric negative, 
discharge mostly at o. Intervals = 0 8 of an inch : A and B 
inductric positive, discharge mostly at n } as positive brush ; 
inductric negative, discharge mostly at o, as positive brush. 
Here the positive discharge seems most facile. 

1515. Coal gas. — n and o = 0*1 of an inch : A, B inductric 
positive, discharge nearly all at o by negative spark : A, B in- 
ductric negative, discharge nearly all at n by negative spark. 
Intervals = 0*8 of an inch, and A, B inductric positive, dis- 
charge mostly at o by negative brush : A, B inductric nega- 
tive, discharge all at n by negative brush. Here the negative 
discharge most facile. 

1516. Carbonic acid gas. — n and o = 0*4 of an inch : A, B 

inductric positive, discharge nearly all at o, or negative : A, B 
inductric negative, discharge nearly all at n , or negative. In- 
tervals = 0*8 of an inch: A, B inductric positive, discharge 
mostly at o, or negative : A, B inductric negative, discharge 
all at n , or negative. In this case the negative had a decided 
advantage in facility of discharge. , 

1517. Thus, if we may trust this form of experiment, the 



484 Positive and negative\discharge in gases. [Series XIII. 

negative small ball has a decided advantage' in facilitating dis- 
ruptive discharge over the positive small ball in some gases, 
as in carbonic acid gas and coal gas, (1399.), whilst in others 
that conclusion seems more doubtful; and in others, again, 
there seems a probability that tlie positive small ball may be 
superior. All these results were obtained at very nearly the 
same pressure of the atmosphere. 

1518. I made some experiments in these gases whilst in the 
air jar (fig. 131.), as to the change from spark to brush, analo- 
gous to those in the open air already described (1486. 1487.). 
I will give, in a Table, the results as to when brush began to 
appear mingled with the spark ; but the after results were so 
varied, and the nature of the discharge in different gases so 
different, that to insert the results obtained without further in- 
vestigation, would be of little use. At intervals less than those 
expressed the discharge was always by spark. 


1 

Discharge between balls B and D. 

Discharge between balls A and C. 

Small ball B 
inductrie pos. 

Small ballB 
induetriu net). 

Large ball A 
inductrie pott. 

Large ball A 
induelrio net/. 

Air 

0 '55 

0-30 

0-70 

020 

043 

0-82 

o <5 o oo c 

0'40 

0 -02 

0- 45 

0*30 

1- 00 

0*7o 

041 

0*^2 

044 

/ above T80; had 
X not space. 

Nitrogen .... 
Oxygen .... 
Hydrogen . . 
Coal gas .... 

Carbonic acid 


1519. It is to be understood that sparks occurred at much 
higher intervals than these ; the table only expresses that di- 
stance beneath which all discharge was as spark. Some curious 
relations of the different gases to discharge are already dis- 
cernible, but it would be useless to consider them until illus- 
trated by further experiments. 

1520. I ought not to omit noticing here, that Professor Belli 
of Milan has published a very valuable set of experiments on 
the relative dissipation of positive and negative electricity in the 
air* ; he finds the latter far more ready, in this respect, than 
the former. 

* Bibliotheque Universelle, 1836, September, p. 1 52. 




485 


3?eb. 1838.] Positive and nega ive dispersion. 

1521. I made some experiments of a similar kind, but with 
sustained high charges ; the results were less striking than those 
of Signore Belli, and I did not consider them as satisfactory. 
I may be allowed to mention, in connexion with the subject, an 
interfering effect which embarrassed me for a long time. When 
I threw positive electricity from a given point into the air, a 
certain intensity was indicated by an electrometer on the con- 
ductor connected with the point, but as the operation continued 
this intensity rose several degrees ; then making t lie conductor 
negative with the same point attached to it, and all other things 
remaining the same, a certain degree of tension was observed 
in the first instance, which also gradually rose as the operation 
proceeded. Returning the conductor to the positive state, the 
tension was at first low, bufr rose as before ; and so also when 
again made negative. 

J522. This result appeared to indicate that the point which 
had been giving off one electricity, was, by that, more fitted for 
a short time to give off the other. But oil closer examination T 
found the whole depended upon the inductive reaction of that 
air, which being charged by the point, and gradually increasing 
in quantity before it, as the positive or negative issue was con- 
tinued, diverted and removed a part of the inductive aetiou of 
the surrounding wall, and thus apparently affected the powers 
of the point, whilst really it was Jhe dielectric itself that was 
causing the change of tension. 

1523. The results connected with the different conditions of 
positive and negative discharge will have a far greater influence 
011 the philosophy of electrical science than we at present ima- 
gine, especially if, as 1 believe, they depend on the peculiarity 
and degree of polarized condition which the molecules of the 

„ dielectrics concerned acquire (1503. 1000.) Thus, for instance, 
the relation of our atmosphere and the earth within it, to the 
occurrence of spark or brush, must be especial and not acci- 
dental (1404.). It would not else consist with other meteoro- 
logical phenomena, also of course dependent on the special pro- 
perties of the air, and which being themselves in harmony the 
most perfect with the functions of animal and vegetable life, 
arc yet restricted in their actions, not by loose regulations, but 
by laws the most precise. 

1524. Even in the passage through air of the voltaic current 



486 


Disruptive discharge — glow . [Series XIII. 

we sec the peculiarities of positive and negative discharge at 
the two charcoal points ; and if these discharges are made to 
take place simultaneously to mercury, the distinction is still 
more remarkable, both as to the sound and the quantity of va- 
pour produced. 

1525. It seems very possible that, the remarkable difference 
recently observed and described by my friend Professor Daniell*, 
namely, that when a zinc and a copper ball, the same in size, 
were placed respectively in copper and zinc spheres, also the 
same in size, and excited by electrolytes or dielectrics of the 
same strength and nature, the zinc ball far surpassed the zinc 
sphere in action, may also be connected with these phenomena ; 
for it is not difficult to conceive how the polarity of the particles 
shall be affected by the circumstjfnce of the positive surface, 
namely the zinc, being the larger or the smaller of the two in- 
closing the electrolyte. It is even possible, that with different 
electrolytes or dielectrics the ratio may be considerably varied, 
or in some cases even inverted. 

Glow discharge. 

1526. That form of disruptive discharge which appears as a 
glow (1359. 1405.), is very peculiar and beautiful : it seems to 
depend on a quick and almost continuous charging of the air 
close to, and in contact with, the conductor. 

1527. Diminution of the charging surface will produce it. 
Thus, when a rod 03 of an inch in diameter, with a rounded 
termination, was rendered positive in free air, it gave fine brushes 
from the extremity, but occasionally these disappeared, and a 
quiet.phospliorescent continuous glow took their place, cover- 
ing the whole of the end of the wire, and extending a very small 
distance from the metal into the air. With a rod 0'2 of an inch 
in diameter the glow was more readily produced. With still 
smaller rods, and also with blunt conical points, it occurred still 
more readily ; and with a fine point I could not obtain the brush 
in free air, -but only this glow. The positive glow and the 
positive star are, in fact, the same. 

1528. Increase of power in the machine tends to produce the 
glow ; for rounded terminations which will give only brushes 

* Philosophical Transactions, 1838, p. 47. 



487 


Feb. 1838.] In rarefied air— ^negative glow. 

whqn the machine is in weak action, ‘will readily give the glow 
when it is in good order. 

1529. Rarefaction of the air wonderfully favours the glow 
phenomena. A brass ball, two and a half inches in diameter, 
being made positively indqctric in an air-pump receiver, be- 
came covered with glow over an area of two inches in diameter, 
when the pressure was reduced to 4*4 inches of mercury. By 
a little adjustment the ball could be covered all over with this 
light. Using a brass ball 1*25 inches in diameter, and making 
it inducteously positive by an induct ric negative point, the phe- 
nomena, at high degrees of rarefaction, were exceedingly beau- 
tiful. The glow came over the positive ball, and gradually in- 
creased in brightness, until it was at last very luminous ; and 
it also stood up like a low £amc, half an inch or more in height. 
On touching the sides of the glass jar this lambent flame was 
affected, assumed a ring form, like a crown on the top of the 
ball, appeared flexible, and revolved with a comparatively slow 
motion, i. e. about four or five times in a second. This ring- 
shape and revolution are beautifully connected with the me- 
chanical currents (1570.) taking place within the receiver. 
These glows in rarefied air are often highly exalted in beauty 
by a spark discharge at the conductor (1551. Note.). 

1530. To obtain a negative glow in air at common pressures 
is difficult. I did not procure it on the rod 0*3 of an inch in 
diameter by my machine, nor on much smaller rods ; and it is 
questionable as yet, whether, even on fine pohits, what is (‘ailed 
the negative star is a very reduced and minute, but still inter- 
mitting brush/ or a glow similar to that obtained on a positive 
point. 

1531. In rarefied air the negative glow can easily be obtained. 
If the rounded ends of two metal rods, aboi.it 0*2 of an inch in 
diameter, are introduced into a globe or jar (the air within being 
rarefied), and being opposite to each other, arc about four 
inches apart, the glow can be obtained on both rods, covering 
not only the ends, but an inch or two of the part behind. On 
using balls in the air-pump jar, and adjusting the distance and 
exhaustion, the negative ball could be covered with glow, 
whether it were the inductric or the inducteous surface. 

1532. When rods are used it is necessary to be aware that, 
if placed concentrically in the jar or globe, the light on one rod 



4S8 


Glow — its variation |? — continuous : [Series XIII* 

is often reflected by the sides of the vessel on to the other rod, 
and makes it apparently luminous, when really it is not so. This 
effect may he detected by shifting the eye at the time of obser- 
vation, or avoided by using blackened rods. 

1533. It is curious to observe the relation of glow , brush , and 
spark to cacli other, as produced by positive or negative sur- 
faces ; thus, beginning with spark discharge, it passes into 
brush much sooner when the surface at which the discharge 
commences (1.181.) is negative, than it does when positive ; but 
proceeding onwards in the order of change, we find that the 
positive brush passes into glow long before the negative brush 
does. So that, though each presents the three conditions in 
the same general order, the series are not precisely the same. 
It is probable that, when these points are minutely examined, 
as they must be shortly, we shall find that each different gas or 
dielectric presents its own peculiar results, dependent upon the 
mode in which its particles assume polar electric condition. 

1531. The glow occurs in all gases in which I have looked 
for it. These are air, nitrogen, oxygen, hydrogen, coal gas, 
carbonic acid, muriatic acid, sulphurous acid and ammonia. I 
thought also that I obtained it in oil of turpentine, but if so it 
was very dull and small. 

1535. The glow is always accompanied by a wind proceed- 
ing either directly out from the glowing part, or directly to- 
wards it ; the former being the most general case. This takes 
place even when the glow occurs upon a ball of considerable 
size : and if matters be so arranged that the ready and regular 
access of air to a part exhibiting the glow be interfered with or 
prevented, the glow then disappears. 

1530. I have never been able to analyse or separate the glow 
into visible elemcnjtary intermitting discharges (14 27. 1433.) , 
nor to obtain the other evidence of intermitting action, namely 
an audible sound (1431.). The want of success, as respects 
trials made by ocular means, may depend upon the large size 
of the glow preventing the separation of the visible images : 
and, indeed, if it does intermit, it is not likely that all parts in- 
termit at once with a simultaneous regularity. 

1537. All the effects tend to show, that glow is due to a con- 
tinuous charge or discharge of air ; in the former case being 
accompanied by a current from, and in the latter by one to, the 



Feb. 1838.] 


its nature — transitions. 


489 


place of the glow. As the surrounding air comes up to the 
charged conductor, on attaining that spot at which the tension 
of the particles is raised to the sufficient degree (1370. 1410.), 
it becomes charged, and then moves off, by the joint action of 
the forces to which it is subject ; and, at the same time that it 
makes way for other particles to come and be charged in turn, 
actually helps to form that current by which they are brought 
into the necessary position. Thus, through the regularity of 
the forces, a constant and quiet result is produced ; and that 
result is, the charging of successive portions of air, the produc- 
tion of a current, and of a continuous glow. 

1538. 1 have frequently been able to make the termination 
of a rod, which, when left to itself, would produce a brush, 
produce in preference a §low, simply by aiding the formation 
of a current of air at its extremity ; and, on the other hand, it 
is not at all difficult to convert the glow into brushes, by affect- 
ing the current of air (157 I. 1579.) or the inductive action near it. 

1539. The transition from glow, on the one hand, to brush 
and spark, on the other, and, therefore, their connexion, may 
be established in various ways. Those circumstances which 
tend to facilitate the charge* of the air by the excited conductor, 
and also those which tend to keep the tension at the same de- 
gree notwithstanding the discharge, assist in producing the glow ; 
whereas those which tend to resist the charge of the* air or 
other dielectric, and those which favour the accumulation of 
electric force prior to discharge, which, sinking hv that act, has 
to be exalted before the tension can again acquire the requisite 
degree, favour intermitting discharge, and, therefore, the pro- 
duction of brush or spark. Thus, rarefaction of the air, the 
removal of large conducting surfaces from the neighbourhood 
of the glowing termination, the presentation of a sharp point 
towards it, help to sustain or produce the glow : hut the' con- 
densation of the air, the presentation of the hand or other large 
surface, the gradual approximation of a discharging ball, tend 
to convert the glow into brush or even spark. All these cir- 
cumstances may be traced and reduced, in a manner easily com- 
prehensible, to their relative power of assisting to produce, 
either a continuous discharge to the air, which gives the glow ; 
or an interrupted one, which produces the brush, and, in a more 
exalted condition, the spark. 



490 Glow — dar) j| discharge. [Series XIII. 

1540. The rounded end of a brass rod, 0*3 of an inch in dia- 
meter, was covered with a positive glow by the working o^ an 
electrical machine : on stopping the machine, so that the charge 
of the connected conductor should fall, the glow changed for a 
moment into brushes just before the discharge ceased alto- 
gether, illustrating the necessity for a certain high continuous 
charge, for a certain sized termination. Working the machine 
so that the intensity should be just low enough to give continual 
brushes from the end in free air, the approach of a fine point 
changed these brushes into a glow.- Working the machine so 
that the termination presented a continual glow in free air, the 
gradual approach of the hand caused the glow to contract at 
the very end of the wire, then to throw out a luminous point, 
which, becoming a foot stalk (1426J finally produced brushes 
with large ramifications. All these results are in accordance 
with what is stated above (1539.). 

1541. Greasing the end of a rounded wire will immediately 
make it produce brushes instead of glow. A ball having a blunt 
point which can be made to project more or less beyond its sur- 
face, at pleasure, can be made to produce every gradation from 
glow, through brush, to spark. 

1542. It is also very interesting and instructive to trace the 
transition from spark to glow, through the intermediate con- 
dition of stream, between ends in a vessel containing air more 
or less rarefied ; but I fear to ’be prolix. 

1543. All the effects show, that the glow is in its nature ex- 
actly the same as the luminous part of a brush or ramification, 
namely a charging of air ; the only difference being, that the 
glow has a continuous appearance from the constant renewal 
of the same action in the same place, whereas the ramification 
is due tft a momentary, independent and intermitting action of 
the same kind. 


Bark discharge . 

1544. I will now notice a very remarkable circumstance in 
the luminous discharge accompanied by negative glow, which 
may, perhaps, be correctly traced hereafter into discharges of 
much higher intensity. Two brass rods, 0*3 of an inch in dia- 
meter, entering a glass globe on opposite sides, had their ends 



491 


Feb. 1838.] Dark discharge in air . 

brought into contact, and the air about them very much rare- 
fied. _ A discharge of electricity from the machine was then 
made through them, and whilst that was continued the ends 
were separated from each other. At the moment of separation 
a continuous glow came over the end of the negative rod, the 
positive termination remaining quite dark. As the distance 
was increased, a purple stream or haze appeared on the end ofc 1 
the positive rod, and proceeded directly outwards towards the 
negative rod ; elongating as the interval w T as enlarged, but 
never joining the negative glow, there being alwaj's a short 
dark space between. This space, of about j\ ; th or ./ (7 th' of an 
inch, was apparently invariable in its extent and its position, 
relative to the negative rod ; nor did the negative glow vary. 
Whether the negative eyd were inductric or inductcous, the 
same effect was produced. It was strange to see the positive 
purple haze diminish or lengthen as the ends were* separated, 
and yet this dark space and the negative glow remain unaltered 

(fig. *133.). 

1545. Two balls were then used in a large air pump receiver, 
and the air rarefied. The usual transitions in the character of 
the discharge took place ; but whenever the luminous stream, 
which appears after the spark and the brush have ceased, was 
itself changed into glow at the halls, the dark space occurred, 
and that whether the one or the other ball was made induetric, 
or positive, or negative. 

1516. Sometimes when the negative ball was large, t lie ma- 
chine in powerful action, and the rarefaction high, the ball 
would be covered over half its surface with glow, and then, 
upon a hasty observation, w ould seem to exhibit no dark space : 
but this was a deception, arising from the overlapping of the 
convex termination of the negative glow and the concave ter- 
mination of the positive stream. More careful observation and 
experiment have convinced me, that when the negative glow 
occurs, it never visibly touches the luminous part of the posi- 
tive discharge, but that the dark space is alw ays there. 

1547. This singular separation of the positive and negative 
discharge, as far as Concerns their luminous character, under 
circumstances which one would have thought very favourable 
to their coalescence, is probably connected with their differ- 
ences when in the form of brush, and is perhaps even de- 



492 Dark disruptive discharge . [Series XIII. 

pendent on the same cause. Further, there is every likelihood 
that the dark parts which occur in feeble sparks are also con- 
nected with these phenomena*. To understand them would 
be very important, for it is quite clear that in many of the ex- 
periments, indeed in all that I have quoted, discharge is taking 
place across the dark part of the dfelcctric to an extent quite 
equal to what occurs in the luminous part. This difference in 
the result would seem to imply a distinction in the modes by 
which the two electric forces are brought into equilibrium in 
the respective parts ; and looking upon all the phenomena as 
giving additional proofs, that it is to the condition of the par- 
ticles of the dielectric wc must refer for the principles of induc- 
tion and discharge, so it would be of great importance if 'we 
could know accurately in what the difference of action in the 
dark and the luminous parts consisted. 

1518. The dark discharge through air (1552.), which in the 
ease mentioned is very evident (1514.), leads to the inquiry, 
whether the particles of air are generally capable of effecting 
discharge from one to another without becoming luminous ; and 
the inquiry is important, because it is connected with that de- 
gree of tension which is necessary to originate discharge (1368. 
1370.). Discharge between air and conductors without lumi- 
nous appearances are very common; and non-luminous dis- 
charges by carrying currents of air and other fluids (1562. 1595.) 
are also common enough : but *111080 are not cases in point, for 
they are not discharges between insulating particles. 

1519. An arrangement was made for discharge between two 
balls (1185.) (fig. 129.) but, in place of connecting the inducteous 
ball directly with the discharging train, it was put in commu- 
nication with the inside coating of a Leyden jar, and the dis- 
charging* train with the outside coating. Then working the 
machine, it was found that whenever sonorous and luminous 
discharge occurred at the balls A B, the jar became charged; 
but that when these did not occur, the jar acquired no charge : 
and such was the case when -small rounded terminations were 
used in place of the balls, and also in whatever manner they 
were arranged. Under these circumstances, therefore, dis- 
charge even between the air and conductors was always lumi- 
nous. 

* See Professor Johnson’s experiments. Silliman’s Journal, xxv. p. 67. 



493 


Feb. 1838.] in ah' — rarefied . 

1550. But in other cases, the phenomena are .such as to make 
"it almost certain, that (lark discharge can take place across air. 
If the rounded end of a metal rod, 0T5 of an inch in diameter, 
be made to give a good negative brush, the approach of a smaller 
end or a blunt point opposite to it will, at a certain distance, 
cause a diminution of the brush, and a glow will appear on the 
positive inducteous wire, accompanied by a current of air pass- 
ing from it. Now , as the air is being charged both at the po- 
sitive and negative surfaces, it seems a reasonable conclusion, 
that the charged portions meet somewhere in the interval, and 
there discharge to each other, without producing any Luminous 
phenomena. It is possible, however, that the air electrified 
positively at the glowing end may travel on towards the negative 
surface, and actually fornj that atmosphere into which the visi- 
ble negative brushes dart, in which case dark discharge need 
not, of necessity, Occur. But I incline to the former opinion, 
and think, that the diminution in size of the negative brush, as 
the positive glow comes on to the end of the opposed win 4 , is 
in favour of that view. 

1551. Using rarefied air as the dielectric, it is very easy to 
obtain luminous phenomena as brushes, or glow, upon both con- 
ducting balls or terminations, whilst the interval is dark, and 
that, when the action is so momentary that 1 think we cannot 
consider currents as effecting discharge across the dark part. 
Thus if two balls, about an indh in diameter, and 4 or more 
inches apart, have the air rarefied about them, and are then in- 
terposed in the course of discharge, an interrupted or spark 
current being produced at the machine*, each termination may 
be made to show luminous phenomena, whilst more or less of 
the interval is quite dark. The discharge will pass as suddenly 
as a retarded spark (295. 334.), i. e. in an interval of time almost 
inappreciably small, and in such a case, I think it must' have 
passed across the dark part as true disruptive discharge, and 
not by convection. 

1552. Hence I conclude that dark disruptive discharge may 
occur (1547. 1550.) ; and also, that, in the luminous brush, the 

* By spark current I mean one passing in a series of spark between tlie 
conductor of the machine and the apparatus : hy a continuous current one 
that passes through metallic conductors, and in that respect without inter- 
ruption at the same place. 



494 Dark discharge in' muriatic acid , [Series XIII. 

visible ramifications may not show the full extent of the dis- 
ruptive discharge (1444. 1452.), but that each may have a dark 
outside, enveloping, as it were, every part through which the 
discharge extends. It is probable, even, that there are such 
things as . dark discharges analogous in form to the brush and 
the spark, but not luminous in any jlart (1445.). 

1553. The occurrence of dark discharge in any case shows 
at how low a tension disruptive discharge may occur (1548.), 
and indicates that the light of the ultimate brush or spark is in 
no relation to the intensity required (1368. 1370.). So to speak, 
the discharge begins in darkness, and the light is a mere con- 
sequence of the quantity which, after discharge has commenced, 
flows to that spot and there finds its most facile passage (1418. 
1435.) , As an illustration of the growth generally of discharge, 
I may remark that, in the experiments on the transition in 
oxygen of the discharge from spark to brush (1518.), every 
spark was immediately preceded by a short brush. 

1554. The phenomena relative to dark discharge in other 
gases, though differing in certain characters from those in air, 
confirm the conclusions drawn above. The two rounded ter- 
minations (1544.) (fig. 133.), were placed in muriatic acid gas 
(1415. 1463.) at the pressure of 6*5 inches of mercury, and a 
continuous machine current of electricity sent through the ap- 
paratus : bright sparks occurred until the interval was about 
or above an inch, when they* were replaced by squat brushy 
intermitting glows Upon both terminations, with a dark part 
between. When the current at the machine was in spark, then 
each spark caused a discharge across the muriatic acid gas, 
which, with a certain interval, was bright ; with a larger in- 
terval, was straight across and flamy, like a very exhausted and 
sudden, *but not a dense sharp spark ; and with a still larger 
interval, produced a # feeble brush on the inductile positive end, 
and a glow on the inducteous negative end, the dark part being 
between (1544.) ; and at such times, the spark at the con- 
ductor, instead of being sudden and sonorous, was dull and 
quiet (334.). 

1555. On introducing more muriatic acid gas, until the press- 
ure was 20' 9 7 inches, the same terminations gave bright sparks 
within at small distances ; but when they were about an inch 
or more apart, the discharge was generally with very small 



495 


Feb. 1838.] in coal-gas — hydrogen — nitrogen. 

brushes and glow, and frequently with no light at all, though 
oldfctricity had passed through the gas. Whenever the bright 
spark did pass through the muriatic acid gas at this pressure, 
it was bright throughout, presenting no dark or dull space. 

1556. In coal gas } at common pressures, when the distance 
was about an inch, the discharge was accompanied by short 
brushes on the ends, and a dark interval ot‘ half an inch or 
more between them, notwithstanding the discharge had the 
sharp quick sound of a dull spark, and could not have de- 
pended in the dark part on convection (1562.). 

1557. This gas presents several curious points in relation to 
the bright and dark parts of spark discharge. When bright 
sparks passed between the rod ends 0*3 of an inch in diameter 
(1511.), very sudden dark parts would occur next to the bright- 
est portions of the spark.' Again, with these ends and also 
with balls (14*22.), the bright sparks would bo sometimes red, 
sometimes green, and occasionally green and ml in different 
parts of the same spark. Again, in the experiments described 
(1518.), at certain intervals a very peculiar pale, dull, yet sud- 
den discharge would pass, which, though apparently weak, 
w*as very direct in its course, and accompanied by a sharp 
snapping noise, as if quick in its occurrence. 

1558. Hydrogen frequently gave peculiar sparks, one part 
being bright red, whilst the other was a dull pale gray, or else 
the whole spark was dull and pcouliar. 

1559. Nitrogen presented a very remarkable discharge, be- 
tween two halls of the respective diameters of 0*15 and 2 inches 
(1506. 1518.),, the smaller one being rendered negative either 
directly or inducteously. The peculiar discharge occurs at in- 
tervals between 0*42 and 0*68, and even at 1*4 inches when the 
large ball was inductric positively; it consisted of little 
brushy part on the small negative hall, thbn a dark space*, and 
lastly a dull straight line on the large positive ball (fig. 134.). 
The position of the dark space was very constant, and is pro- 
bably in direct relation to the dark space described when ne- 
gative glow was produced (1544.). When by any circumstance 
a bright spark was determined, the contrast with the peculiar 
spark described was very striking; for it always had a faint 
purple part, but the place of this part was constantly near the 
positive ball. 



496 Relation of conduction disruptive discharge. [Series XIII. 

1560. Thus dark discharge appears to be decidedly esta- 
blished. But its establishment is accompanied by proofs fhat 
it occurs in different decrees and modes in different gases. 
Hence then another specific action, added to the many (1296. 
1398. 1399. 1423. 1454. 1503.) by which the electrical relations 
of insulating dielectrics are distinguished and established, and 
another argument in favour of that molecular theory of induc- 
tion, which is at present under examination *. 


1561. What I have had to say regarding disruptive dis- 
charge has extended to some length, but I hope will be ex- 
cused in consequence of the importance of the subject. Before 
concluding my remarks, I will again intimate in the form of a 
query, whether we have not reason to consider the tension or 
retention and after discharge in air or other insulating dielec- 
trics, as the same thing with retardation and discharge in a 
metal wire, differing only, but almost infinitely, in degree (1334. 
1336.). In other words, can we not, by a gradual chain of as- 
sociation, carry up discharge from its occurrence in air, through 
spermaceti and water, to solutions, and then on to chlorides, 
oxides and metals, without any essential change in its character ; 
and, at the same time, connecting the insensible conduction of 
air, through muriatic acid gas and the dark discharge, with the 
better conduction of spermaoeti, water, and the all but perfect 
conduction of the metals, associate the phenomena at both ex- 
tremes? and may it not be, that the retardation and ignition 
of a wire are effects exactly correspondent in their nature to 
the retention of charge and spark in air ? If so, here again the 
two extremes in property amongst dielectrics will be found to 
be in intimate relation, the whole difference probably depending 
upon the mode arrtl degree in which their particles polarize 
under the influence of inductive actions (1338. 1603. 1610.). 

If x. Convection , or carrying discharge . 

1562. The last kind of discharge which I have to consider is 
that effected by the motion of charged particles from place to 

* I cannot resist referring here by a note to Biot’s philosophical view of 
the nature of the light of the electric discharge, Annales de Chimie, lki. p. 321. 



497 


Feb. 1838.] Convection or carrying discharge. 

c 

place. It is apparently very different in its nature to any of 
the’former modes of discharge (1319.), but, as the result is the 
same, may be of great importance i# illustrating, not merely 
the nature of discharge itself, but also of what we call the electric 
current. It often, as before observed, in cases of brush and 
glow (1440. 1535.), joins its effect to that of disruptive dis- 
charge, to complete the act of neutralization amongst the elec- 
tric forces. 

1563. The particles which being charged, then travel, may 
be either of insulating or conducting matter, large or small. 
The consideration in the first place of a large particle of con- 
ducting matter may perhaps help our conceptions. 

1564. A copper boiler 3 feet in diameter was insulated and 
electrified, but so feebly, that dissipation by brushes or dis- 
ruptive discharge did not occur at its edges or projecting parts 
in a sensible degree. A brass ball, 2 inches in diameter, sus- 
pended by a clean white silk thread, was brought towards it, 
and it was found that, if the ball was held for a second or two 
near any part of the charged surface of the boiler, at such dis- 
tance (two inches more or less) as not to receive any direct 
charge from it, it became itself charged, although insulated the 
whole time ; and its electricity was the reverse of that of the 
boiler. 

1565. This effect was the strongest opposite the edges and 
projecting parts of the boiler, and weaker opposite the sides, 
or those extended portions of the surface which, according to 
Coulomb’s results, have the weakest charge. It was very 
strong opposite a rod projecting a little way from the boiler. 
It occurred when the copper was charged negatively as well as 
positively : it was produced also with small balls down to 0 ‘2 
of an inch and less in diameter, and also with smaller charged 
conductors than the copper. It is, indeed, hardly possible' in 
some cases to carry an insulated ball within an inch or two 
of a charged plane or convex surface without its receiving a 
charge of the contrary kind to that of the surface. 

1566. This effect is one of induction between the bodies, 
not of communication. The ball, when related to the positive 
charged surface by the intervening dielectric, has its opposite 
sides brought into contrary states, that side towards the boiler 
being negative and the outer side positive. More inductric 

2 & 



498 Charging of particles in air . [Series XIII. 

action is directed towards it than would have passed across the 
same place if the hall had not been there, for several reasons ; 
amongst others, because^ being a conductor, the resistance of 
the particles of the dielectric, which otherwise would have been 
there,. is removed (1298.) ; and also, because the reacting posi- 
tive surface of the ball being pr ejected further out from the 
boiler than when there is no introduction of conducting matter, 
is more free therefore to act through the rest of the dielectric 
towards surrounding conductors, and so favours the exaltation 
of that inductric polarity which is directed in its course. It is, 
as to the exaltation of force upon its outer surface beyond that 
upon the inductric surface of the boiler, as if the latter were 
itself protuberant in that direction. Thus it acquires a state 
like, but higher than, that of the surface of the boiler which 
causes it ; and sufficiently exalted to discharge at its positive 
surface to the air, or to affect small particles, as it is itself 
affected by the boiler, and they flying to it, take a charge and 
pass off ; and so the ball, as a whole, is brought into the con- 
trary inducteous state. The consequence is, that, if free to 
move, its tendency, under the influence of all the forces, to ap- 
proach the boiler is increased, whilst it at the same time be- 
comes more and more exalted in its condition, both of polarity 
and charge, until at a certain distance, discharge takes place, it 
acquires the same state as the boiler, is repelled, and passing 
to that conductor most favourably circumstanced to discharge 
it, there resumes its first indifferent condition. 

1567. It seems to me, that the manner in which inductric 
bodies affect uncharged floating or moveable conductors near 
them, is very frequently of this nature, and generally so when 
it ends in a carrying operation (1562. 1602.). The manner in 
which, whilst the dominant inductric body cannot give off its 
electricity to the air, the inducteous body can effect the discharge 
of the same kind of force, is curious, and, in the case of elongated 
or irregularly shaped conductors, such as filaments or particles 
of dust, the effect will often be very ready, and the consequent 
attraction immediate. 

1568. The effect described is also probably influential in 
causing those variations in spark discharge referred to in the 
last series (1386. 1390. 1391.) : for if a particle of dust were 
drawn towards the axis of induction between the balls, it would 



Feb. 1838.] Charging of dust — of fluid particles. 499 

tend, whilst at some distance from that axis, to commence dis- 
charge at itself, in the manner described (1566.), and that com- 
mencement might so far facilitate thf act (1417. 1420.) as to 
make the complete discharge, as spark, pass through the par- 
ticle, though it might not be the shortest course from ball to 
ball. So also, with equal 13alls at equal distances, as in the 
experiments of comparison already described (1193. 1506.), a 
particle being between one pair of balls would cause discharge 
there in preference \ or even if a particle were between each, 
difference of size or shape would give one for the time a pre- 
dominance over the other. 

1569. The power of particles of dust to carry off electricity in 
cases of high tension is well know n, and 1 have already men- 
tioned some instances of the kind in the use of the inductive 

» 

apparatus (1201.). The general operation is very well shown 
by large light objects, as the toy called the electrical spider ; 
or, if smaller ones are wanted for philosophical investigation, by 
the smoke of a glowing green w ax taper, which, presenting a suc- 
cessive stream of such particles, makes their course visible. 

1570. On using oil of turpentine as the dielectric, the action 
and course of small conducting carrying particles in it can be 
well observed. A few short pieces of thread will supply the 
place of carriers, and their progressive action is exceedingly in- 
teresting. 

1571. A very striking effect w r as* produced on oil of turpen- 
tine, which, whether it w r as due to the carrying power of the 
particles in it, or to any other action of them, is perhaps as yet 
doubtful. A portion of that fluid in a glass vessel had a large 
uninsulated silver dish at the bottom, and an electrified metal 
rod with a round termination dipping into it at the top. The 
insulation was very good, and the attraction and other pheno- 
mena striking. The rod end, w ith a drop of gum water at- 
tached to it, was then electrified in the fluid ; the gum water 
soon spun off in fine threads, and w as quickly dissipated through 
tile oil of turpentine. By the time that four drops had in this 
way been commingled with a pint of the dielectric, the latter 
had lost by far the greatest portion of its insulating power ; no 
sparks could be obtained in the fluid ; and all the phenomena 
dependent upon insulation had sunk to a low degree. The 
fluid was very slightly turbid. TJpon being filtered through 

2 K 2 



500 


Convection — effect of points. [Series XIII. 


paper only, it resumed its first clearness, and now insulated as 
well as before. The water, therefore, was merely diffused 
through the oil of turpentine, not combined with or dissolved 
in it : but whether the minute particles acted as carriers, or 
whether they were not rather gathered together in the line of 
highest inductive tension (1350.), •hnd there, being drawn into 
elongated forms by the electric forces, combined their effects 
to produce a band of matter having considerable conducting 
power, as compared with the oil of turpentine; is as ; ques- 
tionable. 

, 1572. The analogy between the action of solid conducting 
carrying particles and that of the charged particles of fluid in- 
sulating substances, acting as dielectrics, is very evident and 
simple ; but in the latter case the result is, necessarily, currents 
in the mobile media. Particles are brought by inductric action 
into a polar state ; and the latter, after rising to a certain ten- 
sion (1370.), is followed by the communication of a part of the 
force originally on the conductor ; the particles consequently 
become charged, and then, under the joint influence of the re- 
pellant and attractive forces, are urged towards a discharging 
place, or to that spot where these inductric forces are most easily 
compensated by the contrary inducteous forces. 


1573. Why a point should be so exceedingly favourable to 
the production of currents in a fluid insulating dielectric, as air, 
is very evident. It is at the extremity of the point that the in- 
tensity necessary to charge the air is first acquired (1374.) ; it 
is from thence that the charged particle recedes ; and the me- 
chanical force which it impresses on the air to. form a current 
is in every way favoured by the shape and position of the rod, 
of which the poii^t forms the termination. At the same time, 
the point, having become the origin of an active mechanical 
force, does, by the very act of causing that force, namely, by 
discharge, prevent any other part of the rod from acquiring the 
same necessary condition, and so preserves and sustains its own 
predominance, 

1574. The very varied and beautiful phenomena produced 
by sheltering or enclosing the point, illustrate the production 
of the current exceedingly well, and justify the same conclu- 



501 


Feb. 1838,] Currents in fluids. 

sions ; it being remembered that in such cases the effect upon 
th® discharge is of two kinds. For the current may be inter- 
fered with by stopping the access of fresh uncharged air, or re- 
tarding the removal of that which has been charged, as when 
a point is electrified in a tube of insulating matter closed atone 
extremity; or the electric condition of the point itself may be 
altered by the relation of other parts in its neighbourhood, 
also rendered electric, as when the point is in a metal tube, 
by the metal itself, or when it is in the glass tube, by a simi- 
lar action of the charged parts of the glass, or even by the 
surrounding air which has been charged, and which cannot 
escape. 

1 575. Whenever (t is intended to observe such inductive 
phenomena in a fluid dielectric as have a direct relation to, and 
dependence upon, the fluidity of the medium, such, for instance, 
as discharge from points, or attractions and repulsions, &o., 
then the mass of the fluid should be great, and in such pro- 
portion to the distance between the inductrie and inductcous 
surfaces as to include all the lines of inductive force (1309.) 
between them; otherwise, the effects of currents, attraction, 
&c., which are the resultants of all these forces, cannot be ob- 
tained. The phenomena which occur in the open air, or in 
the middle of a globe filled with oil of turpentine, will not take 
place in the same media if confined in tubes of glass, shell-lac, 
sulphur, or other such substances, though they be excellent 
insulating dielectrics ; nor can they be expected ; for in such 
cases, the polar forces, instead of being all dispersed amongst 
fluid particles, which tend to move under their influence, are 
now associated in many parts with particles that, notwithstand- 
ing their tendency to motion, are constrained by their solidity 
to remain quiescent. 

1576. The varied circumstances under which, with conductors 
differently formed and constituted, currents can occur, all illus- 
trate the same simplicity of production. A ball , if the intensity 
be raised sufficiently on its surface, and that intensity be greatest 
on a part consistent with the production of a current of air up 
to and off from it, will produce the effect like a point (1537.) ; 
such is the case whenever the glow occurs upon a ball, the 
current being essential to that phenomenon. If as large a sphere 
as can well be employed with the production of glow be used. 



502 


Convection — currents in air [Series XIII. 

the glow will appear at the place where the current leaves the 
ball, and that will be the part directly opposite to the connection 
of the ball and rod which supports it; but by increasing the 
tension elsewhere, so as to raise it above the tension upon that 
spot, which can easily be effected inductively, then the place of 
the glow and the direction of the Current will also change, and 
pass to that spot which for the time is most favourable for their 
production (1591.). 

1577. For instance, approaching the hand towards the ball 
will tend to cause brush (1539.), but by increasing the supply 
of electricity the condition of glow may be preserved ; then on 
moving the hand about from side to side the position of the glow 
will very evidently move with it. 

1578. A point brought towards a glowing ball would at twelve 
or fourteen inches distance make the glow break into brush, but 
when still nearer glow was reproduced, probably dependent upon 
the discharge of wind or air passing from the point to the ball, 
and this glow was very obedient to the motion of the point, 
following it in every direction. 

1579. Even a current of wind could affect the place of tlio 
glow ; for a varnished glass tube being directed sideways to- 
wards the ball, air was sometimes blown through it at the ball, 
and sometimes not. In the former case, the place of the glow 
was changed a little, as if it were blown away by the current, 
and this is just the result which might have been anticipated. 
All these effects illustrate beautifully the general causes and 
relations, both of the glow and the current of air accompanying 
it (1571.) 

1580. Flame facilitates the production of a current in the 
dielectric surrounding it. Thus, if a ball which would not occa- 
sion a current in the air have a flame, whether large or small, 
formed on its surface, the current is produced with the greatest 
ease j but not the least difficulty can occur in comprehending the 
effective action of %e flame in this case, if its relation, as part 
of the surrounding dielectric, to the electrified ball, be but for a 
moment considered (1375. 1380.). 

1581. Conducting fluid terminations, instead of rigid points, 
/illustrate in a very beautiful fanner the forinatipu of the cur- 
rents, with their effects and influence in exalting the conditions 



503 


Ebb. 1838.] from terminations of mercury } watery fyc. 

under which they were commenced. Let the rounded end o£ 
a»bt*ass rod, 0*3 of an inch or thereabouts in diameter, point 
downwards in free air ; let it be amalgamated, and have a drop 
of mercury suspended from it ; and then let it be powerfully 
electrized. The mercury will present the phenomenon of glow ; 
a current of air will rush along the rod, and set off from the 
mercury directly downwards ; and the form of the metallic drop 
will be slightly effected, the convexity at a small part near the 
middle and lower part becoming greater, whilst it diminishes all 
round at places a little removed from this spot. The change is 
from the form of a (fig. 135.) to that of b y and is due almost, if 
not entirely, to the mechanical force of the current of air sweep- 
ing over its surface. 

1582. As a comparative observation, let it be noticed, that a 
ball gradually brought towards it converts the glow into brushes, 
and ultimately sparks pass from the most projecting part of the 
mercury. A point does the same, but at much smaller distances. 

1583. Take next a drop of strong solution of muriate of lime ; 
being electrified, a part will probably be dissipated, but a consi- 
derable portion, if the electricity be not too powerful, will re- 
main, forming a conical drop (fig. 130.), accompanied by a strung 
current. If glow be produced, the drop will be smooth on the 
surface. If a short low brush is formed, a minute tremulous 
motion of the liquid will be visible ; but both effects coincide 
with the principal one to be observed, namely, the regular and 
successive charge of air, the formation of a wind or current, 
and the form given by that current to the fluid drop. If a dis- 
charge ball be gradually brought toward the cone, sparks will 
at last pass, and these will be from the apex of the cone to the 
approached ball, indicating a considerable degree of cond acting 
power in this fluid. 

1584. With a drop of water, the effects were of the same 
kind, and were best obtained when a portion of gum >vater or 
of syrup hung from a ball (fig. 137.) When the machine was 
worked slowly, a fine large quiet conical drop, with concave 
lateral outline, and a small rounded end, was produced, on which 
the glow appeared, whilst a steady wind issued, in a direction 
from the point of the cone, of sufficient force to depress the 

urface of uninlulated water held opposite to the termination. 
When the machine was worked more rapidly some of the water 



504 


Convection — at fluid terminations [Series XIII. 

was driven off ; the smaller pointed portion left was roughish 
on the surface, and the sound of successive brush dischai%ra 
was heard. With still more electricity, more water was dis- 
persed; that which remained was elongated and contracted, 
with an alternating motion ; a stronger brush discharge was 
heard, and the vibrations of the wa^er and the successive dis- 
charges of the individual brushes were simultaneous. When 
water from beneath was brought towards the drop, it did not 
indicate the same regular strong contracted current of air as 
before; and when the distance was such that sparks passed, 
the water beneath was attracted rather than driven away, and 
the current of air ceased . 

1585. When the discharging ball was brought near the drop 
in its first quiet glowing state (1582.), it converted that glow 
into brushes, and caused the vibrating motion of the drop. 
When still nearer, sparks passed, but they were always from 
the metal of the rod, over the surface of the water, to the point, 
and then across the air to the ball. This is a natural conse- 
quence of the deficient conducting power of the fluid (1584. 
1585.). 

1586. W r hy the drop vibrated, changing its form between the 
periods of discharging brushes, so as to be more or less acute 
at particular instants, to be most acute when the brush issued 
forth, and to be isochronous in its action, and how the quiet 
glowing liquid drop, on assuming the conical form, facilitated, 
as it were, the first action, are points, as to theory, so evident, 
that I will not stop to speak of them. The principal thing to 
observe at present is, the formation of the carrying current of 
air, and the manner in which it exhibits its existence and in- 
fluence by giving form to the drop. 

1587. That the drop, when of water, or a better conductor 
than water, is formed into a cone principally by the current of 
air, is shown amongst other ways (1594.) thus. A sharp point 
being held opposite the conical drop, the latter soon lost its 
pointed form ; was retracted and became round ; the current 
of air from it ceased, and was replaced by one from the point 
beneath, which, if the latter were held near enough to the drop, 
actually blew it aside, and rendered it concave in form. 

1588. It is hardly necessary to say what happened with stil 
worse conductors than water, as oil, or oil of turpentine ; the 



505 


Feb. 1838.] in rarefied air . 

fluid itself was then spun out into threads and carried off, not 
<*nTy because the air rushing over its surface, helped to sweep 
it away, but also because its insulating particles assumed the 
same charged state as the particles of air, and, not being able 
to discharge to them in a much greater degree than the air 
particles themselves could* do, were carried off by the same 
causes which urged these in their course. A similar effect 
with melted sealing-wax on a metal-point forms an old and 
well-known experiment. 

1589. A drop of gum water in the exhausted receiver of the 
air-pump was not sensibly affected in its form when electrified. 
When air was let in, it began to show change of shape when 
the pressure was ten inches of mercury. At the pressure of 
fourteen or fifteen inches the change was more sensible*, and as 
the air increased in density the effects increased, until they were 
the same as those in the open atmosphere. The diminished 
effect in the rare air I refer to the relative diminished energy 
of its current ; that diminution depending, in the first place, on 
the lower electric condition of the electrified ball in the rarefied 
medium, and in the next, on the attenuated condition of the 
dielectric, the cohesive force of water in relation to rarefied air 
being something like that of mercury to dense air (1581.), whilst 
that of water in dense air may be compared to that of mercury 
in oil of turpentine (1597.). 

1590. When a ball is covered >yith a thick conducting fluid, 
as treacle or syrup, it is easy by inductive action to determine 
the wind from almost any part of it (1577.); the experiment, 
which before was of rather difficult performance, being ren- 
dered facile in consequence of the fluid enabling that part, 
which at first was feeble in its action, to rise into an exalted 
condition by assuming a pointed form. 

1591. To produce the current, the electric intensity must 
rise and continue at one spot , namely, at the origin of the cur- 
rent, higher than elsewhere, and then, air having a uniform and 
ready access, the current is produced. If no current be allowed 
(1574.), then discharge may take place by brush or spark. 
But whether it be by brush or spark, or wind, it seems very 
probable that the initial intensity or tension at which a particle 
of a given gaseous dielectric charges, or commences discharge. 



506 Nature of the convective current . [Series XIII. 

is, under the conditions before expressed, always the same 

(1410.). 

1592. It is not supposed that all the air which enters into 
motion is electrified ; on the contrary, much that is not charged 
is carried on into the stream. The part which is really charged 
may be but a small proportion of that which is ultimately set 
in motion (1442.). 

1593. When a drop of gum water (1584.) is made negative , 
it presents a larger cone than when made positive ; less of the 
fluid is thrown off, and yet, when a ball is approached, sparks 
can hardly be obtained, so pointed is the cone, and so free the 
discharge. A point held opposite to it did not cause the re- 
traction of the cone to such an extent as when it w r as positive. 
All the effects are so different from those presented by the 
positive cone, that I have no doubt such drops would present a 
very instructive method of investigating the difference of posi- 
tive and negative discharge in air and other dielectrics (1480. 
1501.). 

1594. That I may not be misunderstood (1587.), I must ob- 
serve here that I do not consider the cones produced as the 
result only of the current of air or other insulating dielectric 
over their surface. When the drop is of badly conducting 
matter, a part of the effect is due to the electrified state of the 
particles, and this part constitutes almost the whole when the 
matter is melted sealing-wax, oil of turpentine, and similar in- 
sulating bodies (1588.). But even when the drop is of good 
conducting matter, as water, solutions, or mercury, though the 
effect above spoken of will then be insensible (1607.), still it is 
not the mere current of air or other dielectric which produces 
all the change of form ; for a part is due to those attractive 
forces by which the charged drop, if free to move, would travel 
along the line of strongest induction, and not being free to 
move, has its form elongated until the sum of the different 
forces tending to produce this form is balanced by the cohesive 
attraction of the fluid. The effect of the attractive forces are 
well shown when treacle, gum water, or syrup is used ; for the 
long threads which spin out, at the same time that they form 
the axes of the currents of air, which may still be considered 
as determined at their points, are like flexible conductors, and 



Feb. 1838.] Currents in oil of turpentine . 507 

show by their directions in what way the attractive forces draw 
4liem. 

1595. When the phenomena of currents are observed in 
dense insulating dielectrics, they present us with extraordinary 
degrees of mechanical force. Thus, if a pint of well-rectified 
and filtered (1571.) oil of •turpentine, be put into a glass vessel, 
and two wires be dipped into it in different places, one leading 
to the electrical machine, and the other to the discharging train, 
on working the machine the fluid will be thrown into violent 
motion throughout its whole mass, whilst at the same time it 
will rise two, three, or four inches up the machine wire, and 
dart off in jets from it into the air. 

1596. If very clean uninsulated mercury be at the bottom of 
the fluid, and the wire from the machine be terminated either 
by a ball or a point, and also pass through a glass tube extend- 
ing both above and below the surface of the oil of turpentine, 
the currents can be better observed, and will be seen to rush 
down the wire, proceeding directly from it towards the mer- 
cury, and there, diverging in all directions, will ripple its sur- 
face strongly, and mounting up at the sides of the vessel, will 
return to re-enter upon their course. 

1597. A drop of mercury being suspended from an amalga- 
mated brass ball, preserved its form alhiost unchanged in air 
(1581.) ; but when immersed in the oil of turpentine it became 
very pointed, and even particles of the metal could be spun out 
and carried off by the currents of the dielectric. The form of 
the liquid metal was just like that of the syrup in air (1584.) 
the point of.the cone being quite as fine, though not so long. 
By bringing a sharp uninsulated point towards it, it could also 
be effected in the same manner as the syrup drop in air (1587.), 
though not so readily, because of the density and limited quan- 
tity of the dielectric. 

1598. If the mercury at the bottom of the fluid be connected 
with the electrical machine, whilst a rod is held in the hand 
terminating in a ball three quarters of an inch, less or more, in 
diameter, and the ball be dipped into the electrified fluid, very 
striking appearances ensue. When the ball is raised again so 
as to be at a level nearly out of the fluid, large portions of the 
latter will seem to cling to it (fig. 138.). If it be raised higher, 
a column of the oil of turpentine will still eonqect it with that 



508 Direction of convective currents. [Series XIII. 

in the basin below (fig. 139.) . If the machine be excited into 
more powerful action, this will become more bulky, and msiy< 
then also be raised higher, assuming the form (fig. 140) ; and 
all the time that these effects continue, currents and counter- 
currents, sometimes running very close together, may be ob- 
served in the raised column of fluid. <■ 

1599. It is very difficult to decide by sight the direction of 
the currents in such experiments as these. If particles of silk 
are introduced they cling about the conductors; but using 
drops of water and mercury the course of the fluid dielectric 
seems well indicated. Thus, if a drop of water be placed at 
the end of a rod (1571.) over the uninsulated mercury, it is soon 
swept away in particles streaming downwards towards the mer- 
cury. If another drop be placed on the mercury beneath the 
end of the rod, it is quickly dispersed in all directions in the 
form of streaming particles, the attractive forces drawing it into 
elongated portions, and the currents carrying them away. If 
a drop of mercury be hung from a ball used to raise a column 
of the fluid (1598.), then the shape of the drop seems to show 
currents travelling in the fluid in the direction indicated by the 
arrows (fig. 141.). 

1600. A very remarkable effect is produced on these pheno- 

mena, connected with -positive and negative charge and dis- 
charge, namely, that a ball charged positively raises a much 
higher and larger column of the oil of turpentine than when 
charged negatively. There can be no doubt that this is con- 
nected with the difference of positive and negative action al- 
ready spoken of (1480. 1525.), and tends much to strengthen 
the idea that such difference is referable to the particles of the 
dielectric rather than to the charged conductors, and is de- 
pendent upon the mode in which these particles polarize 
(1503. 1523.). 

1601. Whenever currents travel in insulating dielectrics they 
really effect discharge ; and it is important to observe, though 
a very natural result, that it is indifferent which way the cur- 
rent or particles travel, as with reversed direction their state 
is reversed. The change is easily made, either in air or oil of 
turpentine, between two opposed rods, for an insulated ball 
being placed in connexion with either rod and brought near its 



Convective currents in metals . 


509 


Feb. 1838.] 

extremity, will cause the current to set towards it from the op- 
posite end. 

1602. The two currents often occur at once, as when both 
terminations present brushes, and frequently when they exhi- 
bit the glow (1531.). In such cases, the charged particles, or 
many of them, meet and mutually discharge each other (1548, 
1612.). If a smoking wax taper be held at the end of an insu- 
lating rod towards a charged prime conductor, it will very often 
happen that two currents will form, and be rendered visible by 
its vapour, one passing as a fine filament of smoky particles 
directly to the charged conductor, and the other passing as 
directly from the same taper wick outwards, and from the con- 
ductor; the principles of inductric action and charge, which 
were referred to in considering the relation of a carrier ball and 
a conductor (1566.), being* here also called into play. 

1603. The general analogy and, I think I may say, identity 
of action found to exist as to iusulation and conduction (1338. 
1561.) when bodies, the best and the worst in the classes of 
insulators or conductors, were compared, led me to believe that 
the phenomena of convection in badly conducting media were 
not without their parallel amongst the best conductors, such 
even as the metals. Upon consideration, the cones produced 
by Davy* in fluid metals, as mercury and tin, seemed to be 
cases in point, and probably also # the elongation of the metallic 
medium through which a current of electricity was passing, de- 
scribed by Ampfcre (1113.) f ; for it is not difficult to conceive, that 
the diminution of convective effect, consequent upon the high 
conducting power of the metallic media used in these experi- 
ments, might be fully compensated for by the enormous quantity 
of electricity passing. In fact it is impossible not to expect 
some effect, whether sensible or not, of the kind in question, 
when such a current is passing through a fluid offering a sen- 
sible resistance to the passage of the electricity, and, thereby 
giving proof of a certain degree of insulating power (1328.). 

1604. I endeavoured to connect the convective currents in 
air, oil of turpentine, See. and those in metals, by intermediate 
cases, but found this not easy to do. On taking bodies, for in* 

* Philosophical Transactions, 1823, p. 155. 

t Biblioth&que Universedle, xxi. 47. 



510 Convection in conductors and insulators. [Series XIII. 

stance, which, like water, acids/solutions, fused salts or chlo- 
rides, &c., have intermediate conducting powers, the minuto 
quantity of electricity which the common machine can supply 
(371. 861.) is exhausted instantly, so that the cause of the phe- 
nomenon is kept either very low in intensity, or the instant of 
time during which the effect lasts is* so small, that one cannot 
hope to observe the result sought for. If a voltaic battery be 
used, these bodies are all electrolytes, and the evolution of gas, 
or the production of other changes, interferes and prevents 
observation of the effect required. 

1605. There arc, nevertheless, some experiments which il- 
lustrate the connection. Two platina wires, forming the elec- 
trodes of a powerful voltaic battery, were placed side by side, 
^iear each other, in distilled water, hermetically sealed up in a 
strong glass tube, some minute vegetable fibres being present 
in the water. When, from the evolution of gas and the conse- 
quent increased pressure, the bubbles formed on the electrodes 
were so small as to produce but feebly ascending currents, then 
it could be observed that the filaments present were attracted 
and repelled between the two wires, as they wonld have been 
between two oppositely charged surfaces in air or oil of turpen- 
tine, moving so quickly as to displace and disturb the bubbles 
and the currents which* these tended to form. Now I think it 
cannot be doubted, that under similar circumstances, and with 
an abundant supply of electricity, of sufficient tension also, 
convective currents might have been formed; the attractions 
and repulsions of the filaments were, in fact, the elements of 
such currents (1572.), and therefore water, though almost infi- 
nitely above air or oil of turpentine as a conductor, is a medium 
in which similar currents can take place. 

1606., I had an apparatus made (fig. 142.) in which a is a 
plate of shell -lac, b affine platina wire passing through it, and 
having only the section of the wire exposed above ; c a ring of 
bibiilous paper resting on the shell-lac, and d distilled water 
retained by the paper in its place, and just sufficient in quantity 
to cover the end of the wire b ; another wire, e , touched a piece 
of tinfoil lying in the water, and was also connected with a dis- 
charging train ; in this way it was easy, by rendering b either 
positive or negative, to send a current of electricity by its ex- 
tremity into the fluid, and so away by the wire e. 



Feb. 1838.] Convective currents in water. 511 

1607. On connecting b with the conductor of a powerful 
<ilc*;trical machine, not the least disturbance of the level of the 
fluid over the end of the wire during the working of the 
machine could be observed ; but at the same time there was not 
the smallest indication of electrical charge about the conductor 
or of the machine, so complete was the discharge. I conclude 
that the quantity of electricity passed in a given time had been 
too small, when compared with the conducting power of the 
fluid to produce the desired effect. 

1608. I then charged a large Leyden battery (291.), and 
discharged it through the wire b> interposing, however, a w r ct 
thread, two feet long, to prevent a spark in the water, and to 
reduce what would else have been a sudden violent discharge 
into one of more moderate character, enduring for a sensible 
length of time (33 L). I iTow did obtain a very brief elevation 
of the water over the end of the wire ; and though a few 
minute bubbles of gas were at the same time formed there, so as 
to prevent me from asserting that the effect was unequivocally 
the same as that obtained by Davy in the metals, yet, according 
to my best judgement, it was partly, and I believe principally, 
of that nature. 

1609. I employed a voltaic battery of 100 pair of four-inch 
plates for experiments of a similar nature with electrolytes. In 
these cases the shell-lac was cupped, and the wire h 0 2 of an 
inch in diameter. Sometimes I. used a positive amalgamated 
zinc wire in contact with dilute sulphuric acid; at others, a 
negative copper wire in a solution of sulphate of copper; but, 
because of the evolution of gas, the precipitation of copper, 
&c., I was not able to obtain decided results. It is but right to 
mention, that when I made use of mercury,' endeavouring to 
repeat Davy's experiment, the battery of 100 pair was not 
sufficient to produce the elevations*. 

1610. The latter experiments (1609.) may therefore be con- 
sidered as failing to give the hoped-for proof, but I have much 
confidence in the former (1605. 1608.), and in the consider- 
ations (1603.) connected with them. If I have rightly viewed 

* In the experiments at the Royal Institution, 8ir II. Davy used, I think, 
500 or 600 pairs of plates. Those at the London Institution were made with 
the apparatus of Mr. Pepvs (consisting of an enormous single pair of plates) 
described in the Philosophical Transactions for 1823, p. 187. 



512 Conduction and insulation. [Sekies XIII. 

them, and we may be allowed (o compare the currents at points 
and surfaces in such extremely different bodies as air and the 
metals, and admit that they are effects of the same kind, differ- 
ing only in degree and in proportion to the insulating or con- 
ducting power of the dielectric used, what great additional ar- 
gument we obtain in favour of thrft theory, which in the phe- 
nomena of insulation and conduction also, as in these, would 
link the same apparently dissimilar substances together (1336. 
1561.); and how completely the general view, which refers all 
the phenomena to the direct action of the molecules of matter, 
seems to embrace the various isolated phenomena as they suc- 
cessively come under consideration ! 


1611. The connection of this convective or carrying effect, 
which depends upon a certain degree of insulation, with con- 
duction ; i . e. the occurrence of both in so many of the sub- 
stances referred to, as, for instance, the metals, water, air, &c., 
would lead to many very curious theoretical generalizations, 
which I must not indulge in here. One point, however, I shall 
venture to refer to. Conduction appears to be essentially an 
action of contiguous particles, and the considerations just 
stated, together with .others formerly expressed (1326. 1336, 
&c.), lead to the conclusion, that all bodies conduct, and by 
the same process, air as well^ as metals ; the only difference 
being in the necessary degree of force or tension between the 
particles which must exist before the act of conduction or trans- 
fer from one particle to another can take place. 

1612. The question then arises, what is this limiting condi- 
tion which separates, as it were, conduction and insulation from 
each other ? Does it consist in a difference between the two 
contiguous particle^, or the contiguous poles of these particles, 
in the nature and amount of positive and negative force, no 
communication or discharge occurring unless that difference 
jrises up to a certain degree, variable for different bodies, but 
always the same for the same body ? Or is it true that, how- 
ever small the difference between two such particles, if time be 
allowed, equalization of force will take place, even with the 
particles of such bodies as air, sulphur, or lac ? In the first case, 
insulating power in any particular body would be proportionate 



513 


Feb. 1838.1 Electrical conditions of a vacuum . 

to the degree of the assumed necessary difference of force ; in 
the second, to the time required to equalize equal degrees of 
difference in different bodies. With regard to airs, one is 
almost led to expect a permanent difference of force ; but in all 
other bodies, time seems to be quite sufficient to ensure, ulti- 
mately, complete condueticfti. The difference in the modes by 
which insulation may be sustained, or conduction effected, is 
not a mere fanciful point, but one ol‘ great importance, as being 
essentially connected with the molecular theory of induction, 
and the manner in which the particles of bodies assume and re- 
tain their polarized state. 


xi. Relation of a vacuum to electrical phenomena. 

1G13. It would seem strange, if a theory which refers all the 
phenomena of insulation and conduction, i. t\ all electrical phe- 
nomena, to the action of contiguous particles, were to omit to 
notice the assumed possible case of a vacuum. Admitting that 
a vacuum can be produced, it would be a very curious matter 
indeed to know what its relation to electrical phenomena would 
be; and as shell-lac and metal arc directly opposed to each 
other, whether a vacuum would be opposed to them both, and 
allow neither of induction or conduction across it. Mr,' Mor- 
gan* has said that a vacuum does not conduct. Sir 11. Davy 
concluded from his investigations* that as perfect a vacuum 
as could be madef did conduct, but does not consider the pre- 
pared spaces which he used as absolute vacua. In such ex- 
periments I think I have observed the luminous discharge to 
be principally on the inner surface of the glass; and it docs 
not appear at all unlikely, that, if the vacuum refused to con- 
duct, still the surface of glass next it might carry on that 
action. 

1614. At one time, when I thought inductive force was ex- 
erted in right lines, I hoped to illustrate this important ques- 
tion by making experiments on induction with metallic mirrors 
(used only as conducting vessels) exposed towards a very clear 
sky at night time, and of such concavity that nothing but the 
firmament could be visible from the lowest part of the conqave 

* Philosophical Transactions, 1786, p. 272. t Ibid, 1822, p. 64. 

2 L 



514 Electrical conditions of a vacuum. [Series XIII. 

n, fig. 143. Such mirrors, wiien electrified, as by connexion 
with a Leyden jar, and examined by a carrier ball, readily gave 
electricity at the lowest part of their concavity if in a room ; but 
I was in hopes of finding that, circumstanced as before stated, 
they would give little or none at the same spot, if the atmo- 
sphere above really terminated in a Vacuum. I was disappointed 
in the conclusion, for I obtained as much electricity there as 
before ; but on discovering the action of induction in curved 
lines (1231.), found a full and satisfactory explanation of the 
result. 

1615. My theory, as far as I have ventured it, does not pre- 
tend to decide upon the consequences of a vacuum. It is not 
at present limited sufficiently, or rendered precise enough, 
either by experiments relating to spaces void of matter, or those 
of other kinds, to indicate what would happen in the vacuum 
case. I have only as yet endeavoured to establish, what all the 
facts seem to prove, that when electrical phenomena, as those 
of induction, conduction, insulation, and discharge occur, they 
depend on, and are produced by the action of contiguous par- 
ticles of matter, the next existing particle being considered os 
the contiguous one ; and I have further assumed, that these 
particles are polarized ; that each exhibits the two forces, or 
the force in two directions (1295. 1298.) ; and that they act at 
a distance, only by acting on the contiguous and intermediate 
particles. 

1616. But assuming that a perfect vacuum were to intervene 
in the course of the lines of inductive action (1304), it does not 
follow from this theory, that the particles on opposite sides of 
such a vacuum could not act on each other. Suppose it pos- 
sible for a positively electrified particle to be in the centre of a 
vacuum an inch in diameter, nothing in my present view s forbids 
that the particle should act at the distance of half an inch on 
all the particles forming the inner superfices of the bounding 
sphere, and with a force consistent with the well known law of 
the squares of the distance. But suppose the sphere of an inch 
were full of insulating matter, the electrified particle would not 
then, according to my notion, act directly on the distant par- 
ticles, but on those in immediate association with it, employing 
all its power in polarizing them ; producing in them negative 
force equal in amount to its own positive force and directed to- 



515 


Feb. 1838.] Nature of the electric current . 

wards the latter, and positive force of equal amount directed 
owtVards and acting in the same manner upon the layer of par- 
ticles next in succession. So that ultimately, those particles in 
the surface of a sphere of half an inch radius, which were acted 
on directly when that sphere was a vacuum, will now be acted 
on indirectly as respects thfc central particle or source of ac- 
tion, i. e, they will be polarized in the same way, and with the 
same amount of force. 

§ 10. Nature of the electric current . 

1617. The word current is so expressive in common language, 
that when applied in the consideration of electrical phenomena 
we can hardly divest it sufficiently of its meaning, or prevent 
our minds from being prejudiced by it (28.3. 511.). I shall use 
it in its common electrical sense, namely, to express generally 
a certain condition and relation, of electrical forces supposed to 
be in progression. 

1618. A current is produced both by excitement and dis- 
charge ; and whatsoever the variation of the two general causes 
may he, the effect remains the same. Thus excitement may 
occur in many ways, as by friction, chemical action, influence of 
heat, change of condition, induction, &c.,j and discharge has 
the forms of conduction, electrolyzation, disruptive discharge, 
and convection ; yet the current connected with these actions, 
when it occurs, appears in all cases to bo the same. This con- 
stancy in the character of the current, notwithstanding the par- 
ticular and great variations which may be made in the mode of 
its occurrence,' is exceedingly striking and important ; and its 
investigation and development promise to supply the most open 
and advantageous road to a true and intimate understanding of 
the nature of electrical forces. 

1619. As yet the phenomena of the current have presented 
nothing in opposition to the view I have taken of the nature of 
induction as aijt action of contiguous particles. I have endea- 
voured to divest myself of prejudices and to look for contra- 
dictions, but I have not perceived any in conductive, electrolytic, 
convective, or disruptive discharge. 


2 l 2 



516 Current : — its electrolytic condition. [Series XIII. 

I 

1620. Looking at the current as a cause, it exerts very ex- 
traordinary and diverse powers, not only in its course and ’or 
the bodies in which it exists, but collaterally* as in inductive 
or magnetic phenomena. 

1621. Electrolytic action. — One of its direct actions is the 
exertion of pure chemical force, this being a result which has 
now been examined to a considerable extent. The effect is 
found to be constant and definite for the quantity of electric 
force discharged (783, &e.) ; and beyond that, the intensity 
required is in relation to the intensity of the affinity or forces 
to be overcome (904. 906. 911.). The current and its conse- 
quences are here proportionate ; the one may be employed to 
represent the other ; no part of the effect of either is .lost or 
gained ; so that the case is a strict one, and yet it is the very case 
which most strikingly illustrates the doctrine that induction is 
an action of contiguous particles (1164. 1343.). 

1622. The process of electrolytic discharge appears to me 
to be in close analogy, and perhaps in its nature identical with 
another process of discharge, which at first seems very differ- 
ent from it, I mean convection (1347. 1572.), In the latter 
case the particles may travel for yards across a chamber ; they 
may produce strong winds in the air, so as to move machinery ; 
and in fluids, as oil of turpentine, may even shake the hand, 
and carry heavy metallic bodies about*; and yet I do not see 
that the force, either in kind* or action, is at all different to that 
by which a particle of hydrogen leaves one particle of oxygen to 
go to another, or by which a particle of oxygen travels in the 
contrary direction. 

1623. Travelling particles of the air can effect chemical 
changes just as well as the contact of a fixed platina electrode, 
or that of a combining electrode, or the ions of a decomposing 
electrolyte (453. 471.) ; and in the experiment formerly de- 
scribed, where eight places of decomposition were rendered 
active by one current (469.), and where charged particles of air 
in motion were the only electrical means of connecting these 

* If a metallic vessel three or four inches deep, containing oil of turpentine, 
be insulated and electrified, and a rod with a ball (an inch or more in diameter) 
at the end have the ball immersed in the fluid whilst the end is held in the 
hand, the mechanical force generated when the ball is moved to and from the 
sides of the vessel will soon be evident to the experimenter. 



Feb. 1838.] Electrolytic and convective discharge . 517 

payts of the current, it seems to me that the action of the par- 
ticles of the' electrolyte and of the air were essentially the same. 
A particle of air was rendered positive ; it travelled in a certain 
determinate direction, and coming to an electrolyte, com- 
municated its powers; an equal amount of positive force was 
accordingly acquired by another particle (the hydrogen), and 
the latter, so charged, travelled as the former did, and in the 
same direction, until it came to another particle, and transfer- 
red its power and motion, making that other particle active. 
Now, though the particle of air travelled over a visible and 
occasionally a large space, whilst the particle of the electrolyte 
moved over an exceedingly small one; though the air particle 
might be oxygen, nitrogen, or hydrogen, receiving its charge 
from force of high intensify, whilst the electrolytic particle 1 of 
hydrogen had a natural aptness to receive the positive condition 
with extreme facility; though the air particle might be (‘barged 
with very little electricity at a very high intensity by one pro- 
cess, whilst the hydrogen particle might he charged with much 
electricity at a very low intensity by another process ; these are 
not differences of kind, as relates to the linal discharging ac- 
tion of these particles, but only of degree; not essential dillcr- 
enees which make things unlike, hut such differences as give to 
things, similar in their nature, that great ‘variety which tits them 
for their office in the system of the universe. 

lt>24. So when a particle of ail* or of (lust in it, electrified at a 
negative point, moves on through the influence of the inductive 
forces (1572.) to the next positive surface, and after discharge 
passes away, it seems to me to represent exactly that particle of 
oxygen which, having been rendered negative in the electrolyte, 
is urged by the same disposition of inductive forces, and going to 
the positive platina electrode, is there discharged, and then passes 
away, as the air or dust did before it. 

1G25. Heat is another direct effect of the current upon sub- 
stances in which it occurs, and it becomes a very important 
question, as to the relation of the electric and heating forces, 
whether the latter is always definite in amount *. There are 
many cases, even amongst bodies which conduct without change, 
that at present are irreconcileable with the assumption that it 

* See Be la Rive’s Researches, Bib. Universelle, 1829. xl. p, 40. 



518 Current : — constant and indivisible. [Series XIII, 

is * ; but there are also many which indicate that, when proper 
limitations are applied, the heat produced is definite* Harris 
has shown this for a given length of current in a metallic wire, 
using common electricity f ; and De la Rive has proved the same 
point for voltaic electricity by his beautiful application of 
Breguet's thermometer 

1626. When the production of heat is observed in electro- 
lytes under decomposition, the results are still more compli- 
cated. But important steps have been taken in the investiga- 
tion of this branch of the subject by De la Rive § and others ; 
and it is more than probable that, when the right limitations 
are applied, constant and definite results will here also be 
obtained. 

1627. It is a most important part of the character of the cur- 
rent, and essentially connected with its very nature, that it is 
always the same. The two forces are everywhere in it. There 
is never one current of force or one fluid only. Any one part 
of the current may, as respects the presence of the two forces 
there, be considered as precisely the same with any other part ; 
and the numerous experiments which imply their possible sepa- 
ration, as well as the .theoretical expressions which, being used 
daily, assume it, are, I think in contradiction with facts (511, 
&c.). It appears to me to be as impossible to assume a current 
of positive or a current of negative force alone, or of the two at 
once with any predominance of one over the other, as it is to give 
an absolute charge to matter (516. 1169. 1177.). 

1628. The establishment of this truth, if, as I think, it be a 
truth, or on the other hand the disproof of it, is of the greatest 
consequence. If, as a first principle, we can establish, that the 
centres of the two^forces, or elements of force, never can be 
separated to any sensible distance, or at all events not further 
than the space between two contiguous particles (1615.), or if 
w*e can establish the contrary conclusion, how much more clear 

* Amongst others, Davy, Philosophical Transactions, 1821, p. 438. Pel- 
letier’s important results, Annales de Chimie, 1834, lvi. p. 371, and Becquerel’s 
non-heating current, Bib. Universelle, 1835, lx. 218. 

t Philosophical Transactions, 1824, pp. 225. '228. 

% Annales de Chimie, 1836, lxii. 177. 

§ Bib. Universelle, 1829, xl. 49 j and Ritchie, Phil. Trans. 1832, p. 290. 



Fjsb. 1838.] Uniform as to heat produced . 519 

is our view of what lies before ils, and how much less embar- 
rassed the ground over which we have to pass in attaining to 
it, than if we remain halting between two opinions 1 And if, 
with that feeling, we rigidly test every experiment which bears 
upon the point, as far as our prejudices will let us (1 161.), in- 
stead of permitting them tfith a theoretical expression to pass 
too easily away, are we not much more likely to attaiu the real 
truth, and from that proceed with safety to what is at present 
unknown ? 

1629. I say these things, not, I hope, to advance a particular 
view, but to draw the strict attention of those who are able to 
investigate and judge of the matter, to what must he a turning 
point in the theory of electricity; to a separation of two roads, 
one only of which can be right ; and 1 hope 1 may he allowed 
to go a little further into t*he facts which have driven me to the 
view I have just given. 

1630. When a wire in the voltaic circuit is heated, the tem- 
perature frequently rises first, or most at one end If this 
effect were due to any relation of positive or negative as respects 
the current, it would be exceedingly important. 1 therefore 
examined several such eases; but when, keeping the contacts 
of the wire and its position to neighbouring things unchanged, 
I altered the direction of the current, i found that the effect 
remained unaltered, showing that it depended, not upon the 
direction of the current, but on s>ther circumstances. So there 
is here no evidence of a difference between one part of the cir- 
cuit and another, 

1631. The same point, i. e. uniformity in every part, may be 
illustrated by what may be considered as the inexhaustible nature 
of the current when producing particular effects ; for these effects 
depend upon transfer only, and do not consume the power. Thus 
a current which will heat one inch of plutina wire will heat a 
hundred inches (853. note). If a current be sustained in a 
constant state, it will decompose the fluid in one voltameter only, 
or in twenty others if they be placed in the circuit, in each to 
an amount equal to that in the single one. 

1632. * Again, in cases of disruptive discharge, as in the spark, 
there is frequently a dark part (1422.) which, by Professor 
Johnson, has been called the neutral point*; and this has given 

* Silliman’s Journal, 1834, xxv. p. 57. 



520 Current : — constant and indivisible. [Series XIII. 

rise to the use of expressions implying that there are two elec- 
tricities existing separately, which, passing to that spot, therb 
combine and neutralize each other*. But if such expressions 
are understood as correctly indicating that positive electricity 
alone is moving between the positive ball and that spot, and 
negative electricity only between th6 negative ball and that spot, 
then what strange conditions these parts must be in ; condi- 
tions, which to my mind are every way unlike those which really 
occur ! In such a case, one part of a current would consist of 
positive electricity only, and that moving in one direction; an- 
other part would consist of negative electricity only, and that 
moving in the other direction ; and a third part would consist 
of an accumulation of the two electricities, not moving in either 
direction, but mixing up together, and being in a relation to 
each other utterly unlike any relation which could be supposed 
to exist in the two former portions of the discharge. This does 
not seem to me to be natural. In a current, whatever form the 
discharge may take, or whatever part of the circuit or current 
is referred to, as much positive force as is there exerted in one 
direction, so much negative force is there exerted in the other. 
If it were not so we should have bodies electrified not merely 
positive and negative, bur on occasions in a most extraordinary 
manner, one being charged with five, ten, or twenty times as 
much of both positive and negative electricity in equal quanti- 
ties as another. At present,* however, there is no known fact 
indicating such states. 

1633. Even in cases of convection, or carrying discharge, the 
statement that the current is everywhere the same must in effect 
be true (1627.) ; for how, otherwise could the results formerly 
described occur ? When currents of air constituted the mode of 
discharge between the portions of paper moistened with iodide 
of potassium or sulphate of soda (4-65. 469.), decomposition 
occurred ; and I have since ascertained that, whether a current 
of positive air issued from a spot, or one of negative air passed 
towards it, the effect of the evolution of iodine or of acid was 
the same, whilst the reversed currents produced alkali. So 
also in the magnetic experiments (307.) whether the discharge 
was effected by the introduction of a wire, or the occurrence of 
a spark, or the passage of convective currents either one way 
* Thomson on Heat and Electricity, p. 471. 



521 


Feb. 1838.] Sectiom of the current : — unipolarity . 

or the other, (depending on the electrified state of the particles) 
Xhe result was the same, being in all cases dependent upon the 
perfect current. 

1634. Hence, the section of a current compared with other 
sections of the same current must be a constant quantity, if the 
actions exerted be of the Vame kind ; or if of different kinds, 
then the forms under which the effects are produced are equi- 
valent to each other, and experimentally convertible at pleasure. 
It is in sections, therefore, we must look for identity of electri- 
cal force, even to the sections of sparks and carrying actions, 
as well as those of wires and electrolytes. 

1635. In illustration of the utility and importance of esta- 
blishing that which may be the true principle, 1 will refer to a 
few cases. The doctrine of unipolarity, u< formerly stated, and 
I think generally understood*, is evidently inconsistent with my 
view of a current (1627.) ; and the later singular phenomena of 
poles and flames described by Krnmn and others f partake of 
the same inconsistency of character. If a unipolar body could 
exist, i. e. one that could conduct the one electricity and not the 
other, what very new characters we should have a right to ex- 
pect in the currents of single electricities passing through them, 
and how greatly ought they to differ, not only from the common 
current fvhieh is supposed to have both* electricities travelling 
in opposite directions in equal amount at the same time, but 
also from each other ! The fatets, which are excellent, have, 
however, gradually been fnore correctly explained by Beeque- 
rclj, Andiews§, and others ; and I understand that Professor 
Ohms || has perfected the work, in his close examination of all 

* Erman, Annales de Chimie, 1807, lxi. p. 115. Davy's Elements, p. 168. 
Biot, Ency. Brit. Supp. iv. p. 444. Becquerel, Traite, i. p. 107. Do la Hive, 
Bib. Umv. 1837. vii. 302. 

t Erman, Annales de Chimie, 1824, xxv. 278. 'Becquerel, Ibid, xxxvi. p. 
329. 

t Becquerel, Annales de Chimie, 1831, xlvi. p. 283. 

§ Andrews, Philosophical Magazine, 1830, ix. 182. 

)) Schweigger’s Jahrbuch der Chimie, &c. 1830. Heft 8. Not understand- 
ing German, it is with extreme regret I confess I have not access, and cannot 
do justice,* to the many most valuable papers in experimental electricity pub- 
lished in that language. I take this opportunity also of stating another cir- 
cumstance which occasions me great trouble, and, as I find by experience, may 
make me seemingly regardless of the labours of others: — it is a gradual loss 
of memory for some years past j and now, often when I read a memoir, I re- 



522 Current i — constant and indivisible. [Series XIII. 

the phenomena ; and after showing that similar phenomena can 
take place with good conductors, proves that with soap, &c! 
many of the effects are the mere consequences of the bodies 
evolved by electrolytic action. 

1686. I conclude, therefore, that the facts upon which the 
doctrine of unipolarity was founded are not adverse to that 
unity and indivisibility of character which I have stated the 
current to possess, any more than the phenomena of the pile 
itself, (which might well bear comparison with those of unipolar 
bodies,) are opposed to it. Probably the effects which have 
been called effects of unipolarity, and the peculiar differences 
of the positive and negative surface when discharging into air, 
gases, or other dielectrics (1480. 1525.) which have been already 
referred to, may have considerable relation to each other*. 

1637. M. de la Rive has recently described a peculiar and 
remarkable effect of heat on a current when passing between 
electrodes and a fluid f* It is, that if platina electrodes dip 
into acidulated water, no change is produced in the passing 
current by making the positive electrode hotter or colder; 
whereas making the negative electrode hotter increased the de- 
flexion of a galvanometer affected by the current, from 12° to 
30° and even 45°, whilst making it colder diminished the cur- 
rent in the same high proportions. 

1638. That one electrode should have this striking’ relation 
to heat whilst the other remained absolutely without, seem to 
me as incompatible with what I conceived to be the character 
of a current as unipolarity (1627. 1635.), and it was therefore 
with some anxiety that I repeated the experiment. The elec- 
trodes which I used were platina ; the electrolyte, water con- 
taining* about one sixth of sulphuric acid by weight: the voltaic 
battery consisted of two pairs of amalgamated zinc and platina 
plates in dilute sulphuric acid, and the galvanometer in the cir- 
cuit was one with two needles, and gave when the arrangement 
was complete a deflexion of 10° or 12°. 

member that I have seen it before, and would have rejoiced if at the right 
time I could have recollected and referred to it in the progress of my own 
papers. — AT. F. 

* See also Hare in Silliman’s Journal, 1833, xxiv. 246. 

t Biblioth&pie Universelle, 1837, vii. 388. 



523 


Feb. 1838.] Effects of heat — balls of fire. 

J639. Under these circumstances heating either electrode 
increased the current ; heating both produced still more effect. 
When both were heated, if either were cooled, the effect on 
the current fell in proportion. The proportion of effect due 
t6 heating this or that electrode varied, but on the whole heat- 
ing the negative seemed to favour the passage of the current 
somewhat more than heating the positive. Whether the appli- 
cation of heat were by a flame applied underneath, or one di- 
rected by a blowpipe from above, or by a hot iron or coal, the 
effect was the same. 

1640. Having thus removed the difficulty out of the way of 
my views regarding a current, I did not pursue this curious ex- 
periment further. It is probable, that the difference between 
my results and those of "JI. de la Rive may depend upon the 
relative values of the currents used ; for 1 employed only a 
weak one resulting from two pairs of plates two inches long and 
half an inch wide, whilst M. de la Rive used four pairs of plates 
of sixteen square inches in surface. 


1611. Electric discharges in the atmosphere in the form of 
halls of fire have occasionally been described. Such phenomena 
appear to me to be incompatible with all* that we know of elec- 
tricity and its modes of discharge. As time is an element in 
the effect (1418. 1436.) it is passible perhaps that an electric 
discharge might really pass as a ball from place to place ; but 
as every tiling shows that its velocity must he almost infinite, 
and the time of its duration exceedingly small, it is impossible 
that the eye should perceive it as anything else than a line of 
light. That phenomena of balls of fire may appear in the at- 
mosphere, I do not mean to deny ; but that they have anything 
to do with the discharge of ordinary electricity, or are at all re- 
lated to lightning or atmospheric electricity, is much more than 
doubtful. 

1642. All these considerations, and many others, help to 
confirm »the conclusion, drawn over and over again, that the 
current is an indivisible thing ; an axis of power, in every part 
of which both electric forces are present in equal amount* (517. 

* I am glad U> refer here to the results obtained by Mr. Christie with mag- 



524 


Current , its relation to convection . [Series XIII. 

1627.). With conduction anci electrolyzation, and even dis- 
charge by spark, such a view will harmonize without hurting 
any of our preconceived notions ; but as relates to convec- 
tion, a more startling result appears, which must therefore be 
considered. 

1643. If two balls A and B be electrified in opposite states 
and held within each other's influence, the moment they move 
towards each other, a current, or those effects which are un- 
derstood by the word current, will be produced. Whether A 
move towards B, or B move in the opposite direction towards 
A, a current, and in both cases having the same directi on } will 
result. If A and B move from each other, then a current in 
the opposite direction, or equivalent effects, will be produced. 

1614. Or, as charge exists only b<y induction (1178. 1299.), 
and a body when electrified is necessarily in relation to other 
bodies in the opposite state; so, if a ball be electrified posi- 
tively in the middle of a room and be then moved in any direc- 
tion, effects will be produced, as if a current in the same direc- 
tion (to use the conventional mode of expression) had existed : 
or, if the ball be negatively electrified, and then moved, effects 
as if a current in a direction contrary to that of the motion 
had been formed, will be produced. 

1645. I am saying of a single particle or of two what I have 
before said, in effect, of many (1633.) . If the former account of 
currents be true, then that jrftst stated must be a necessary re- 
sult. And, though the statement niliy seem startling at first, it 
is to be considered that, according to my theory of induction, 
the charged conductor or particle is related to the distant con- 
ductor in the opposite state, or that which terminates the ex- 
tent of the induction, by all the intermediate particles (1165. 
‘1295.)/ these becoming polarized exactly as the particles of a 
solid electrolyte do -when interposed between the two electrodes. 
Hence the conclusion regarding the unity and identity of the 
current in the case of convection, jointly with the former cases, 
is not so strange as it might at first appear. 

1646. There is a very remarkable phenomenon oi* effect of 
the electrolytic discharge, first pointed out, I believe, by Mr. 

neto-electricity, Philosophical Transactions, 1833, p. 113. note. As regards 
the current in a wire, they confirm everything that I am contending for. 



525 


Feb. 1838.] Porrett's effects of the cument. 

Porrett, of the accumulation of *fluid under decomposing action 
m'the current on one side of an interposed diaphragm*. It is 
a mechanical result ; and as the liquid passes from the positive 
towards the negative electrode in all the known cases, it 
seems to establish a relation to the polar condition of the di- 
electric in which the current exists (1161. 1525.). It has not 
as yet been sufficiently investigated by experiment ; for De la 
Rive says +, it requires that the water should be a bad con- 
ductor, as, for instance, distilled water, the effect not happen- 
ing with strong solutions ; whereas, Dutroehct says $ the con- 
trary is the case, and that, the effect is not directly due to the 
electric current. 

1617. Bccquerel, in his Traite dc PKlcetricite, has brought 
together the considerations which arise for and against the 
opinion, that the effect generally is an electric effect §. Though 
1 have no decisive fact to quote at present, 1 cannot refrain 
from venturing an opinion, that the effect is analogous both to 
combination and convection (1(523.), being a case of carrying 
due to the relation of the diaphragm and the fluid in contact 
with it, through which the electric discharge is jointly effected; 
and further, that the peculiar relation of positive and negative 
small and large surfaces already referred to (1 182. 1503, 1525.), 
may be the direct cause of the 1 fluid and* the diaphragm travel- 
ling in contrary but determinate directions. A very valuable 
experiment has been made by ,\1- llecqucrel with particles of 
clay ||, which will probablw bear importantly on this point. 


1618. As long as the terms current and electro-dynamic are 
used to express those relations of the electric forces in which 
progression of either fluids or effects are supposed to occur 
(283.), so Jong will the idea of velocity be associated with them ; 
and this will, perhaps, be more especially the case if the hypo- 
thesis of a fluid or fluids be adopted. 

1619. Hence has arisen the desire of estimating this velocity 
either directly or by some effect dependent on it ; and amongst 

* Annals of Philosophy, 1816, via. p. 75. 

t Annates de Chimie, 1835, xxviii. p. 196. 

% Annales de Chimie, 1832, xlix. p. 423. 

§ VoL iv. pp. 192, 197. 

11 Traitd de l’Electricit^, i. p. 285. 



265 


Velocity of the electric current . [Series XIII. 

the endeavours to do this corifectly, may be mentioned espe- 
cially those of Dr. Watson* in 1748, and of Professor Wheat-* 
stone f in 1834 ; the electricity in the early trials being supposed 
to travel from end to end of the arrangement, but in the later 
investigations a distinction occasionally appearing to be made 
between the transmission of the effect and of the supposed 
fluid by the motion of whose particles that effect is produced. 

1650. Electrolytic action has a remarkable bearing upon this 
question of the velocity of the current, especially as connected 
with the theory of an electric fluid or fluids. In it there is an 
evident transfer of power with the transfer of each particle of 
the anion or cathion present, to the next particles of the cathion 
or anion ; and as the amount of power is definite, we have in 
this way a means of localizing as it were the force, identifying 
it by the particle and dealing it out in successive portions, 
which leads, I think, to very striking results. 

1651. Suppose, for instance, that water is undergoing de- 
composition by the powers of a voltaic battery. Each particle 
of hydrogen as it moves one way, or of oxygen as it moves in 
the other direction, will transfer a certain amount of electrical 
force associated with it in the form of chemical affinity (822. 
852. 918.) onwards through a distance, which is equal to that 
through which the particle itself has moved. This transfer will 
be accompanied by a corresponding movement in the electrical 
forces throughout every part of*the circuit formed (1627. 1634.), 
and its effects may be estimated, as, *for instance, by the heat- 
ing of a wire (853.) at any particular section of the current how- 
ever distant. If the water be a cube of an inch in the side, the 
electrodes touching, each by a surface of one square inch, and 
being an inch apart, then, by the time that a tenth of it, or 25* 
£5 grains, is decomposed, the particles of oxygen and hydrogen 
throughout the mass Inay be considered as having moved rela- 
tively to each other in opposite directions, to the amount of the 
tenth of an inch ; i. e . that two particles at first in combination 
will after the motion be the tenth of an inch apart. Other mo- 
tions which occur in the fluid will not at all interfere with this 
result ; for they have no power of accelerating or retarding the 
electric discharge, and possess in fact no relation to it. 


Philosophical Transactions, 1748. 


t Ibid. 1834, p. 583. 



Feb. 1838 .] Current , its transverse forces. 52 7 

1652. The quantity of electricity in 25*25 grains of water is, 
according to an estimate of the force which I formerly made 
(861.), equal to above 24 millions of charges of a large Leyden 
battery ; or it would have kept any length of a platina wire 
of an inch in diameter red hot for an hour and a half (853.). 
This result, though given only as an approximation, I have seen 
no reason as yet to alter, and it is confirmed generally by the 
experiments and results of M. Pottiliet*. According to Mr. 
Wheatstone^s experiments, the influence or effects of the cur- 
rent would appear at a distance of 576,000 miles in a second f. 
We have, therefore, in this view of the matter, on the one hand, 
an enormous quantity of power equal to a most destructive 
thunder storm appearing instantly at the distance of 576,000 
miles from its source, and on the other, a quiet effect, in pro- 
ducing which the power had taken an hour and a half to travel 
through the tenth of an inch : yet these arc the equivalents to 
each other, being effects observed at the sections of one and 
the same current (1634.). 


1653. It is time that I should call attention to the lateral or 
transverse forces of the current . The great things which have 
been achieved by Oersted, Arago, Ampere, Davy, lie la ltive, 
and others, and the high degree of simplification which has 
been introduced into their arrangement by the theory of Am- 
pere, have not only done their full service in advancing most 
rapidly this branch of knowledge, but have secured to it such 
attention that there is no necessity for urging on its pursuit, i 
refer of course to magnetic action and its relations ; but though 
this is the only recognised lateral action of the current, there is 
great reason for believing that others exist and would by their 
discovery reward a close search for them (051.). 

1654. The magnetic or transverse action of the current 
seems to be in a most extraordinary degree independent of 
those variations or modes of action which it presents directly 
in its course ; it consequently is of the more value to us, as it 
gives us^ higher relation of the power than any that might 
have varied with each mode of discharge. This discharge, 

* Becquerel, Traits de fElectricit^, v. p. 278. 
f Philosophical Transactions, 1884, 589. 



528 Current , its transverse force ; magnetism . [Series XIII. 

whether it be by conduction through a wire with infinite ve- 
locity (1652.), or by electrolyzation with its corresponding dnd 
exceeding slow motion (1651.), or by spark, and probably even 
by convection, produces a transverse magnetic action always 
the same in kind and direction. 

1655. It has been shown by several experimenters, that whilst 
the discharge is of the same kind the amount of lateral or mag- 
netic force is very constant (216. 366. 367. 368. 376.). But 
when we wish to compare discharge of different kinds, for the 
important purpose of ascertaining whether the same amount of 
current will in its different forms produce the same amount of 
transverse action, we find the data very imperfect. Davy no- 
ticed, that when the electric current was passing through an 
aqueous solution it affected a magnetic needle*, and Dr. Ritchie 
says, that the current in the electrolyte is as magnetic as that 
in a metallic wiref, and has caused water to revolve round a 
magnet as a wire carrying the current would revolve. 

1656. Disruptive discharge produces its magnetic effects : a 
strong spark, passed transversely to a steel needle, will mag- 
netise it as well as if the electricity of the spark were conducted 
by a metallic wire occupying the line of discharge ; and Sir H. 
Davy has shown that the discharge of a voltaic battery in vacuo 
is affected and has motion given to it by approximated mag- 
nets J. 

1657. Thus the three vei^y different modes of discharge, 
namely, conduction, electrolyzation^ and disruptive discharge, 
agree in producing the important transverse phenomenon of 
magnetism. Whether convection or carrying discharge will 
produce the same phenomenon has not been determined, and 
the few experiments I have as yet had time to make do not en- 
able me to answer in the affirmative. 

1658. Having arrived at this point in the consideration of the 
current and in the endeavour to apply its phenomena as tests 
of the truth or fallacy of the theory of induction which I have 
ventured to set forth, I am now very much tempted to indulge 
in a few speculations respecting its lateral action and its possi- 

* Philosophical Transactions, 1821, p. 426. f Ibid. 1882, p. 294. 

% Philosophical Transactions, 1821, p. 427. 



Feb. 1838.] 


Current; its transverse forces. 529 

ble^connexion with the transvcrsfe condition of the lines of or- 
dinary induction (1165. 1304.)*. I have long sought and still 
seek for an effect or condition which shall be to statical elec- 
tricity what magnetic force is to current electricity (1411.) ; for 
as the lines of discharge arc associated with a certain trans- 
verse effect, so it appeared *to me impossible but that the lines 
of tension or of inductive action, which of necessity precede 
that discharge, should also have their correspondent transverse 
condition or effect (951.). 

1659. According to the beautiful theory of Amperes the 
transverse force of a current may be represented by its attrac- 
tion for a similar current and its repulsion of a contrary current. 
May not then the equivalent transverse force of static electricity 
be represented by that lateral tension or repulsion which the 
lines of inductive action appear to possess (1304.) ? Then again, 
when current or discharge occurs between two bodies, previ- 
ously under indue trical relations to each other, the lines of in- 
ductive force will weaken and fade away, and, as their lateral 
repulsive tension diminishes, will contract and ultimately dis- 
appear in the line of discharge. May not this be an effect 
identical with the attractions of similar currents? /. e. may not 
the passage of static electricity into current electricity, and that 
of the lateral tension of the lines of inductive force into the la- 
teral attraction of lines of similar discharge, have the same re- 
lation and dependences, and run parallel to each other? 

1660. The phenomena of. induction amongst currents which 

I had the good fortune to discover some years ago (6. See. 1018.) 
may perchance here form a connecting link in the series of ef- 
fects. When a current is first formed, it tends to produce a 
current in the contrary direction in all the matter around it ; 
and if that matter have conducting properties and be fitly cir- 
cumstanced, such a current is produced. On the contrary, 
when the original current is stopped, one in the same direction 
tends to form* all around it, and, in conducting matter properly 
arranged, will be excited. J 

1661. Now though we perceive the effects only in that por- 
tion of master which, being in the neighbourhood, has conduct- 
ing properties, yet hypothetically it is probable, that the non- 
conducting matter has also its relations to, and is affected by, 

* Refer for farther investigation a to 1709. — 173<J. — Dec. 1838 
2 M 



530 Current ; its direct and lateral action. [Series XIII. 

the disturbing cau.se, though we have not yet discovered them. 
Again and again the relation of conductors and non-conductofs 
has been shown tp be one not of opposition in kind, but only 
of degree (1334. 1603.) ; and therefore, for this, as well as for 
other reasons, it is probable, that what will affect a conductor 
will affect an insulator also ; producing perhaps what may de- 
serve the term of the electrotonic state (60. 242. 1114.). 

1662. It is the feeling of the necessity of some lateral con- 
nexion between the lines of electric force (1114.) ; of some link 
in the chain of effects as yet unrecognised, that urges me to the 
expression of these speculations. The same feeling has led 
me to make many experiments on the introduction of insulating 
dielectrics having different inductive capacities (1270. 1277.) 
between magnetic poles and wires carrying currents, so as to 
pass across the lines of magnetic force. 1 have employed such 
bodies both at rest and in motion, without, as yet, being able 
to detect any influence produced by them ; but I do by no means 
consider the experiments as sufficiently delicate, and intend, 
very shortly, to render them more decisive*. 

1663. I think the hypothetical question may at present be 
put thus: can such considerations as those already generally 
expressed (1658.) account for the transverse effects of electrical 
currents ? arc two such currents in relation to each other merely 
by the inductive condition of the particles of matter between 
them, or arc they in relation by some higher quality and con- 
dition (1654.), which, acting at a* distance and not by the in- 
termediate particles, has, like the force of gravity, no relation 
to them ? 

1664. If the latter be the case, then, when electricity is act- 
ing upoii and in matter, its direct and its transverse action are 
essentially different in their nature ; for the former, if I am cor- 
rect, will depend ilpon the contiguous particles, and the latter 
will not. As I have said before, this may be so, and I incline 
to that view at present ; but I am desirous of suggesting con- 
siderations why it may not, that the question may be thoroughly 
sifted. 

1665. The transverse power has a character of pblarity im- 
pressed upon it. In the simplest forms it appears as attraction 


* See onwards 1711. — 1726.— ’Dec. 1838. 



Feb. 1838.] Polar forces act by contiguous particles . 531 

or repulsion, according as the •currents are in the same or dif- 
ferent directions : in the current and the magnet it takes up the 
condition of tangenital forces ; and in magnets and their par- 
ticles produces poles. Since the experiments have been made 
which have persuaded me that the polar forces of electricity, 
as. in induction and electrolytic action (1298. 1313.), show ef- 
fects at a distance only by means of the polarized contiguous 
and intervening particles, I have been led to expect that all 
polar forces act in the same general manner ; and the other 
kinds of phenomena which one can bring to bear upon the- sub- 
ject seem fitted to strengthen that expectation. Thus in cry- 
stallizations the effect is transmitted from particle to particle; 
and in this manner, in acetic acid or freezing water a crystal a 
few inches or even a eonpje of feet in length will form in loss 
than a second, but progressively mid by a transmission of power 
from particle to particle. And, as far as 1 remember, no ease of 
polar action, or partaking of polar action, except the one under 
discussion, can be found which does not act by contiguous par- 
ticles*. It is apparently of the nature of polar forces that such 
should bo the ease, for the one force cither finds or dev (‘lopes 
the contrary force near to it, and has, therefore, no occasion 
to sock for it at a distance. 

1060. But leaving these hypothetical notions respecting the 
nature of the lateral action out of sight, and returning to the 
direct effects, I think that the phenomena examined and reason- 
ing employed in this and tlTe two preceding papers tend to con- 
firm the view first taken (1101.), namely, that ordinary induc- 
tive action and the effects dependent upon it are due to an action 
of the contiguous particles of the dielectric interposed between 
the charged surfaces or parts which constitute, as it were, the 
terminations of the effect. The great point of distinction and 
power (if it have any) in the theory is, the making the dielectric 
of essential and specific importance, instead of leaving it as it 
were a mere accidental circumstance or the simple representative 
of space, having no more influence over the phenomena than the 
space occupied by it. I have still certain other results and 
views respecting the nature of the electrical forces and exci- 

* I mean by contiguous particles those which are next to each other, not 
that there is no space between them. See (1010.). 

2 m 2 



532 


Induction . 


[Series XIII. 


tation, which are connected with the present theory ; and, un- 
less upon further consideration they sink in my estimation", I 
shall very shortly put them into form as another series of these 
electrical researches. 

Royal Institution , 

February 14th , 1838. 



533 


FOURTEENTH SERIES. 

§ 20. Nature of the electric force or forces . § 21. Relation 

of the electric and magnetic forces . § 22. Note on electri- 

cal excitation . 

Received Juno 21, 1838. — Read June 21, 1838. 

§ 20. Nature of the electric force or forces. 

1667. The theory of induction set forth and illustrated in the 
three preceding series of experimental researches dot's not as- 
sume anything new as to the nature of the electric force or 
forces, but only as to their distribution. The effects may de- 
pend upon the association of one electric lhiidwith the particles 
of matter, as in the theory of Franklin, Epinus, Cavendish, and 
Mossotti; or they may depend upon the association of two 
electric fluids, as in the theory of Dufay and Poisson ; or they 
may not depend upon anything which can properly be. called 
the electric fluid, but on vibrations or other affections of the 
matter in which they appear. .The theory is unaffected by 
such differences in the mode of viewing the nature of the forces ; 
and though it professes to perform the important office of sta- 
ting how the powers arc arranged (at least in inductive plumo* 
mena), it does not, as far as 1 can yet perceive, supply a single 
experiment which can bo considered as a distinguishing test of 
the truth of any one of these various views. 

1668. But, to ascertain how the forces are arranged, to trace 
them in their various relations to the particles of matter, to de- 
termine their general laws, and also the specific differences 
which occur under these laws, is as important as, if not more 
so than, to know whether the forces reside in a fluid or not ; 
and with? the hope of assisting in this research, I shall offer 
some further developments, theoretical and experimental, of 
the conditions under which I suppose the particles of matter 
are placed when exhibiting inductive phenomena. 



534 


Theory of static induction . [Series XIV. 


1669. The theory assumes tfoat all the particleSj whether of 
insulating or conducting matter , are as wholes conductors. 

1670. That not being polar in their normal state, they can 
become so by the influence of neighbouring charged particles, 
the polar state being developed at the instant, exactly as in an 
insulated conducting mass consisting of many particles. 

1671. That the particles when polarized are in a forced state, 
and tend to return to their normal or natural condition. 

1672. That being as wholes conductors, they can readily be 
charged, either bodily or polarly. 

1673. That particles which^eing contiguous* are also in the 
line of inductive action can communicate or transfer their polar 
forces one to another more or less readily. 

1674. That those doing so less readily requii'e the polar 
forces to be raised to a higher degree before this transference 
or communication takes place. 

1675. That the ready communication of forces between con- 
tiguous particles constitutes conduction , and the difficult com- 
munication insulation ; conductors and insulator's being bodies 
whose particles naturally possess the property of communica- 
ting their respective forces easily or with difficulty ; having these 
differences just as they have differences of any other natural 
property. 

1676. That ordinary induction is the effect resulting from 
the action of matter charged, with excited or free electricity 
upon insulating matter, tending to produce in it an equal amount 
of the contrary state. 

1677. That it can do this only by polarizing the particles 
contiguous to it, which perform the same office to the next, and 
these again to those beyond ; and that thus the action is pro- 
pagated from the excited body to the next conducting mass, and 
there renders the contrary force evident in consequence of the 
effect of communication which supervenes in the conducting mass 
upon the polarization of the particles of that body (1675.). 

1678. That therefore induction can only take place through 
or across insulators ; that induction is insulation, it being the 
necessary consequence of the state of the particles and the mode 
in which the influence of electrical forces is transferred or trans- 
mitted through or across such insulating media. 

* See note to 1164. — Dec. 1838. 



535 


June 1838.] Action of the contiguous particles . 

1679. The particles of an insulating dielectric whilst under 
induction may he compared to a series of small magnetic needles, 
or more correctly still to a series of small insulated conductors. 
If the space round a charged globe were filled with a mixture 
of an insulating dielectric, as oil of turpentine or air, and small 
globular conductors, as sliqf, the latter being at a little distance 
from each other so as to be insulated, then those would in their 
condition and action exactly resemble what I consider to be the 
condition and action of the particles of the insulating dielectric 
itself (1337.). If the globe were charged, these little conductors 
would all be polar; if the globe were discharged, they would all 
return to their normal state, to be polarized again upon the re- 
charging of the globe. The state developed by induction through 
such particles on a mass of conducting matter at a distance 
would be of the contrary kind, and exactly equal in amount to 
the force in the inductrie globe. There' would be a late ml dif- 
fusion of force (1221. 1297.), because each polarized sphere 
would be in an active or tense relation to all those conti- 
guous to it, just as one magnet can affect two or more magnetic 
needles near it, and these again a still greater number beyond 
them, lienee would result the production of curved lines of 
inductive force if the indurteous body in such a mixed dielec- 
tric were an uninsulated metallic ball (1219. &e.) or other pro- 
perly shaped mass. Such curved lines arc the consequences of 
the two electric forces arranged as 1 have assumed them to be : 
and, that the inductive force can be directed in such euned 
lilies is the strongest proof of the presence of the two powers 
and the polar condition of the dielectric particles. 

1680. I think it is evident, that in the ease stated, action at a 
distance can only result through an action of tin* contiguous 
conducting particles. There is no reason why the inductive 
body should polarize or affect distant conductors anil leave 
those near it, namely the particles of the dielectric, unaffected : 
and everything in the form of fact and experiment with con- 
ducting masses or particles of a sensible size contradicts such a 
supposition. 

1681. JV striking character of the electric power is that it is 
limited and exclusive, and that the two forces being always pre- 
sent are exactly equal in amount. The forces are related in 
one of two ways, either as in the natural normal condition of an 



536 Exclusive static induction . [Series XIY. 

uncharged insulated conductor*; or as in the charged state, 
the latter being a case of induction. # « 

1682. Cases of induction are easily arranged so that the two 
forces being limited in their direction shall present no pheno- 
mena or indications external to the apparatus employed. Thus, 
if a Leyden jar, having its external coating a little higher than 
the internal, be charged and then its charging ball and rod re- 
moved, such jar will present no electrical appearances so long 
as its outside is uninsulated. The two forces which may be 
said to be in the coatings, or in the particles of the dielectric 
contiguous to them, are entirely engaged to each other by in- 
duction through the glass; and a carrier ball (1181.) applied 
either to the inside or outside of the jar will show no signs of 
electricity. But if the jar be insulated, and the charging ball 
and rod, in an uncharged state ahd suspended by an insu- 
lating thread of white^silk, be restored to their place, then the 
part projecting above the jar will give electrical indications and 
charge the carrier, and at the same time the outside coating of 
the jar will be found in the opposite state and inductric towards 
external surrounding objects. 

1683. These are simple consequences of the theory. Whilst 
the charge of the inner coating could induce only through the 
glass towards the outer coating, and the latter contained no 
more of the contrary force than was equivalent to it, no induc- 
tion external to the jar could, be perceived ; but when the in- 
ner coating was extended by the rod and ball so that it could 
induce through the air towards external objects, then the ten- 
sion of the polarized glass molecules would, by their tendency 
to return to the normal state, fall a little, and a portion of the 
charge passing to the surface of this new part of the inner 
conductor, would produce inductive action through the air 
towards distant objects, whilst at the same time a part of the 
force in the outer coating previously directed inwards would 
now be at liberty, and indeed be constrained to induct outwards 
through the air, producing in that outer coating what is some- 
times called, though I think very improperly, free charge. If 
a small Leyden jar be converted into that form of apparatus 
usually known by the name of the electric well, it will illustrate 
this action very completely. 

1684. The terms free charge and dissimulated electricity 
convey therefore erroneous notions if they are meant to imply 



June 1838.] Induction; — polarity of the particles, 537 

any difference as to the mode lor kind of action. The charge 
•upon an insulated conductor in the middle of a room is in the 
same relation to the walls of that room as the charge upon the 
inner coating of a Leyden jar is to the outer coating of the 
same jar. The one is not more free or more dissimulated than 
the other; and when sometimes we make electricity appear 
where it was not evident before, as upon the outside of a charged 
jar, when, after insulating it, we touch the inner coating, it is 
only .because we divert more or less of the inductive force from 
one direction into another; for not the slighest change is in 
such circumstances impressed upon the character or action of 
the force. 

1685. Having given this general theoretical view, I will now 
notice particular points relating to the nature of the assumed 
electric polarity of the insulating dielectric particles. 

1686. The polar state may be considered in common induc- 
tion as a forced state, the particles tending to return to their 
normal condition. It may probably be raised to a very high 
degree by approximation of the induetric and induetcous bodies 
or by other circumstances ; and the phenomena of electrolyza- 
tion (861. 1652. 1706.) seem to imply tlmt the quantity of 
power which can thus be accumulated .on a single particle is 
enormous. Hereafter we may be able to compare corpuscular 
forces, as those of gravity, cohesion, electricity, and chemical 
affinity, and in some way op other from their effects deduce their 
relative equivalents ; at present we arc not able to do so, but 
there seems no reason to doubt that their electrical, which arc 
at the same time their chemical forces (891. 918.), will be by 
far the most energetic. 

1687. I do not consider the powers when developed^ by the 
polarization as limited to two distinct points or spots on the 
surface of each particle to be considered as the poles of an axis, 
but as resident on large portions of that surface, as they are 
upon the surface of a conductor of sensible size when it is 
thrown into a polar state. But it is very probable, notwith- 
standing;, that the particles of different bodies may present spe- 
cific differences in this respect, the powers not being equally 
diffused though equal in quantity ; other circumstances also, as 
form and quality, giving to each a peculiar polar relation. It is 
perhaps to the existence of some such differences as these that 



538 Particles polarized in all directions. [Series XIV. 

we may attribute the specific actions of the different dielectrics 
in relation to discharge (1394. 1508.) . Thus with respect to ox^-« 
gen and nitrogen singular contrasts were presented when spark 
and brush discharge were made to take place in these gases, as 
may be seen by reference to the Table in paragraph 1518 of the 
Thirteenth Series ; for with nitrogen, ?vhen the small negative or 
the large positive ball was rendered inductric, the effects corre- 
sponded with those which in oxygen were produced when the 
small positive or the large negative ball was rendered inductric. 

1688. In such solid bodies as glass, lac, sulphur, &c., the 
particles appear to be able to become polarized in all directions, 
for a mass when experimented upon so as to ascertain its induc- 
tive capacity in three or more directions (1690.), gives no indi- 
cation of a difference. Now as the particles are fixed in the 
mass, and as the direction of the induction through them must 
change with its change relative to the mass, the constant effect 
indicates that they can be polarized electrically in any direction. 
This accords with the view already taken of each particle as a 
whole being a conductor (1669.), and, as an experimental fact, 
helps to confirm that view. 

1689. But though particles may thus be polarized in any di- 
rection under the influence of powers which are probably of 
extreme energy (1686.), it docs not follow that each particle 
may not* tend to polarize to a greater degree, or with more fa- 
cility, in one direction than another ; or that different kinds 
may not have specific differences in tjhis respect, as they have 
differences of conducting and other powers (1296. 1326. 1395.). 

I sought with great anxiety for a relation of this nature ; and 
selecting crystalline bodies as those in which all the particles 
are symmetrically placed, and therefore best fitted to indicate 
any result which might depend upon variation of the direction 
of the forces to the direction of the particles in which they 
were developed, experimented very carefully with them. I was 
the more strongly stimulated to this inquiry by the beautiful 
electrical condition of the crystalline bodies tourmaline and 
boracite, and hoped also to discover a relation between electric 
polarity and that of crystallization, or even of cohesion itself 
(1316.) . My experiments have not established any connexion 
of the kind sought for. But as I think it of equal importance 
to show either that there is or is not such a relation, I shall 
briefly describe the results. 



539 


J unb 1838.] Induction through crystalline bodies. 

1690. The form of experiment was as follows. A brass ball 
0*73 of an inch in diameter, fixed at the end of a horizontal 
brass rod, and that at the end of a brass cylinder, was by 
means of the latter connected with a large Leyden battery 
(291.) by perfect metallic communications, the object being to 
keep that ball, by its connexion with the charged battery in an 
electrified state, very nearly uniform, for half an hour at a time. 
This was the inductric ball. The iudueteous ball was the car- 
rier of the torsion electrometer (1229. 1311.) ; and the dielec- 
tric between them w r as a cube cut from a crystal, so that two 
of its faces should be perpendicular to the optical axis, whilst 
the other four were parallel to it. A small projecting piece of 
shcll-lac was fixed on the inductric ball at that part opposite 
to the attachment of the brass rod, for the purpose of prevent- 
ing actual contact l>ctwocft the ball and the crystal cube. A 
coat of shcll-lac was also attached to that side of the carrier 
ball which was to be towards the cube, being also that side 



which was furthest from the repelled ball in the electrometer 
when placed in its position in that instrument. The cube was 
covered with a thin coat of shell-lac dissolved in alcohol, to 
prevent the deposition of damp upon its surface from the air. 
It was supported upon a small table of shell-lac fixed on the 
top of a%tem of the same substance, the latter being of suffi- 
cient strength to sustain the cube, and yet flexible enough 
from its length to act as a spring, and allow the cube to bear, 
“when in its place, against the shell-lac on the inductric ball. 



540 Induction through rock crystal . [Series XIV. 

1691. Thus it was easy to bring the inducteous ball always 
to the same distance from the inductrie ball, and to uninsulated 
and insulate it again in its place ; and then, after measuring the 
force in the electrometer (1181.), to return it to its place opposite 
to the inductrie ball for a second observation. Or it was easy 
by revolving the stand which supposed the cube to bring four 
of its faces in succession towards the inductrie ball, and so ob- 
serve the force when the lines of inductive action (1304.) coin- 
cided with, or were transverse to, the direction of the optical 
axis of the crystal. Generally from twenty to twenty-eight ob- 
servations were made in succession upon the four vertical faces 
of a cube, and then an average expression of the inductive force 
was obtained, and compared with similar averages obtained at 
other times, every precaution being taken to secure accurate 
results. 

1692. The first cube used was of rock crystal ; it was 07 
of an inch in the side. It presented a remarkable and constant 
difference, the average of not less than 197 observations, giving 
100 for the specific indnetive capacity in the direction coincid- 
ing with the optical axis of the cube, whilst 93*59 and 93*31 
were the expressions for the two transverse directions. 

1693. But with a second cube of rock crystal corresponding 
results .were not obtained. It was 0*77 of an inch in the side. 
The average of many experiments gave 100 for the specific in- 
ductive capacity coinciding wth the direction of the optical 
axis, and 98*6 and 99*92 for the two* other directions. 

1694. Lord Ashley, whom I have found ever ready to ad- 
vance the cause of science, obtained for me the loan of three 
globes of rock crystal belonging to Her Grace the Duchess of 
Sutherland for the purposes of this investigation. Two had 
such fissures as to render them unfit for the experiments 
(1193. 1698.). The *third, which was very superior, gave me 
no indications of any difference in the inductive force for dif- 
ferent directions. 

1695. I then used cubes of Iceland spar. One 0*5 of an 
inch in diameter gave 100 for the axial direction, and 98*66 and 
95*74 for the two cross directions. The other, 0*8 of** an inch 
in the side, gave 100 for the axial direction, whilst 101*73 and 
101*86 were the numbers for the cross direction. 

1696. Besides these differences there were others, which I 
do not think it needful to state, since the main point is not con- 



541 


June 1838. J Induction through Iceland spar, 

firmed. For though the experiments with the first cube raised 
great expectation, they have not been generalized by those 
which followed. I have no doubt of the results as to that 
cube, but they cannot as yet be referred to crystallization. 
There are in the cube some faintly coloured layers parallel to 
the optical axis, and the matter which colours them may have 
an influence ; but then the layers are also nearly parallel to a 
cross direction, and if at all influential should show some effect 
in that direction also, which they did not. 

1697. In some of the experiments one half or one part of a 
cube showed a superiority to another part, and this I could 
not trace to any charge the different parts had received. It 
was found that the varnishing of the cubes prevented anv com- 
munication of charge to them, except (in a few experiments) a 
small degree of the negative state, or that which was contrary 
to the state of the induct ric ball (1564. 1566.). 

1(598. I think it right to say that, as far as I could perceive, 
the insulating character of the cubes used was perfect, or at 
least so nearly perfect, as to bear a comparison with shell-lac, 
glass, &c. (1255.). As to the cause of the differences, other than 
regular crystalline structure, there may be several. Thus minute 
fissures in the crystal insensible to the eye may be so disposed 
as to produce a sensible electrical difference (1193.). Or the 
crystallization may be irregular; or the substance may not be 
quite pure; and if we consider how minute a quantity of 
■matter will alter greatly t^c conducting power of water, it will 
seem not unlikely that a little extraneous matter diffused 
through the whole or part of a cube, may produce effects suffi- 
cient to account for all the irregularities of action that have 
been observed. 

1699. An important inquiry regarding the electricahpolality 
of the particles of an insulating dielectric, is, whether it be the 
molecules of the particular substance acted on, or the compo- 
nent or ultimate particles, which thus act the part of insulated 
conducting polarizing portions (1669.). 

1700. The conclusion I have arrived at is, that it is the 
molecules oT the substance which polarize as wholes (1347.) ; 
and that however complicated the composition of a body may 
be, all those particles or atoms which are held together by 
chemical affinity to form one molecule of the resulting body. 



542 Molecules are polarized, not the elements. [Series XIV. 

act as one conducting mass or<particle when inductive pheno- 
mena and polarization are produced in the substance of which 
it is a part. 

1701. This conclusion is founded on several considerations. 
Thus if we observe the insulating and conducting power of 
elements when they are used as dielectrics, we find some, as 
sulphur, phosphorus, chlorine, iodine, &c., whose particles in- 
sulate, and therefore polarize in a high degree ; whereas others, 
as the metals, give scarcely any indication of possessing a sensi- 
ble proportion of this power (1328.), their particles freely con- 
ducting one to another. Yet when these enter into combina- 
tion they form substances having no direct relation apparently, 
in this respect, to their elements; for water, sulphuric acid, 
and such compounds formed of insulating elements, conduct by 
comparison freely; whilst oxide of 'lead, flint glass, borate of 
lead, and other metallic compounds containing very high pro- 
portions of conducting matter, insulate excellently well. Taking 
oxide of lead therefore as the illustration, I conceive that it is 
not the particles of oxygen and lead which polarize separately 
under the act of induction, but the molecules of oxide of lead 
wdiich exhibit this effect, all the elements of one particle of the 
resulting body, being held together as parts of one conducting 
individual by the bonds of chemical affinity ; which is but an- 
other term for electrical force (918.). 

1702. In bodies which are electrolytes we have still further 
reason for believing in such a state of things. Thus when 
water, chloride of tin, iodide of lead. See. in the solid state are 
between the electrodes of the voltaic battery, their particles 
polarize as those of any other insulating dielectric do (1104.) ; 
but when the liquid state is conferred on these substances, the 
polarized particles divide, the two halves, each in a highly 
charged state, travelling onwards until they meet other parti- 
cles in an opposite and equally charged state, with which they 
combine, to the neutralization of their chemical, i. e. their 
electrical forces, and the reproduction of compound particles, 
which can again polarize as wholes^ and again divide to repeat 
the same series of actions (1347.) . 

1703. But though electrolytic particles polarize as wholes, 
it would appear very evident that in them it is not a matter of 
entire indifference how the particle polarizes (1689.), since, 
when free to move (380, &c.) the polarities are ultimately dis- 



JcrtfE 1838.] 


Mode of polarization. 


513 


tpbuted in reference to the elehients ; and sums of force equiva- 
lent to the polarities, and very definite in kind and amount, 
separate, as it were, from each other, and travel onwards with 
the elementary particles. And though I do not pretend to 
know what an atom is, or how it is associated or endowed with 
electrical force, or how this force is arranged in the cases of 
combination and decomposition, yet the strong belief I have in 
the electrical polarity of particles when under inductive action, 
and the bearing of such an opinion on the general effects of 
induction, whether ordinary or electrolytic, will be my excuse, 
I trust, for a few hypothetical considerations. 

1701. In electrolyzation it appears that the polarized parti- 
cles would (because of the gradual change which has been in- 
duced upon the chemical, i. v. the electrical forces of their 
elements (018.)) rather divide than discharge to each other 
without division (1318.) ; for if their division, i.c. their decom- 
position and recombination, bo prevented by giving them the 
solid state, then they will insulate electricity perhaps a hun- 
dredfold more intense than that necessary for their electroly- 
zation (110, &e.). Hence the tension necessary for direct con- 
duction in such bodies appears to he much higher than that 
for decomposition ( 110. 1 .10 1. 1 .3 1 1 .) . 

1705. The remarkable stoppage of ‘electrolytic conduction 
by solidification (380. 1358.), is quite consistent with these 
views of the dependence of that "process on the polarity winch 
is common to all insulating unit tor when under induction, 
though attended by such peculiar electro-chemical results in 
the case of electrolytes. Thus it may bo expected that the first 
effect of induction is so to polarize and arrange the particles of 
w ater that the positive or hydrogen pole of each shall be from 
the positive electrode and towards the negative elect rod#, whilst 
the negative or oxygen pole of each shall be in the contrary 
direction ; and thus when the oxygen and hydrogen of a par- 
ticle of water have separated, passing to and combining w r ith 
other hydrogen and oxygen particles, unless these new particles 
of water could turn round they could not take up that position 
necessafy for their successful electrolytic polarization. Now 
solidification, by fixing the water particles and preventing them 
from assuming that essential preliminary position, prevents also 
their electrolysis (413.) ; and so the transfer of forces in that 
manner being prevented (1347. 1703.), the substance acts as an 



644 Polarization, fyc. of an electrolyte . [Series XIV. 

ordinary insulating dielectric (f<j>r it is evident by former ex- 
periments (419. 1704.) that the insulating tension is higher, 
than the electrolytic tension), induction through it rises to a 
higher degree, and the polar condition of the molecules as 
wholes, though greatly exalted, is still securely maintained. 

1706. When decomposition happens in a fluid electrolyte, I 
do not suppose that all the molecules in the same sectional 
plane (1634.) part with and transfer their electrified particles 
or elements at once. Probably the discharge force for that 
plane is summed up on one or a few particles, which decompo- 
sing, travelling and recombining, restore the balance of forces, 
much as in the case of spark disruptive discharge (1406.) ; for 
as those molecules resulting from particles which have just 
transferred power must by their position (1705.) be le.ss favour- 
ably circumstanced than others, so there must be some which 
are most favourably disposed, and these, by giving way first, 
will for the time lower the tension and produce discharge. 

1707. In former investigations of the action of electricity 
(821, &c.) it was shown, from many satisfactory cases, that the 
quantity of electric power transferred onwards was in propor- 
tion to and was definite for a given quantity of matter moving 
as anion or catliion onwards in the electrolytic line of action ; 
and there was strong Reason to believe that each of the par- 
ticles of matter then dealt with, had associated with it a definite 
amount of electrical force, constituting its force of chemical 
affinity, the chemical equivalents and„the electro -chemical equi- 
valents being the same (836.). It was also found with few, and 
I may now perhaps say with no exceptions (1341.), that only 
those compounds containing elements in single proportions 
could exhibit the characters and phenomena of electrolytes 
(6870 ; oxides, chlorides, and other bodies containing more 
than one proportion of the electro negative clement refusing to 
decompose under the influence of the electric current. 

1708. Probable reasons for these conditions and limitations 
arise out of the molecular theory of induction. Thus when a 
liquid dielectric, as chloride of tin, consists of molecules, each 
composed of a single particle of each of the elements,* then as 
these can convey equivalent opposite forces by their separation 
in opposite directions, both decomposition and transfer can re- 
sult. But when the molecules, as in the bichloride of tin, con- 
sist of one particle or atom of one element, and two of the other. 



545 


June 1838.] Electric and magnetic forces. 

then the simplicity with widely the particles may be supposed 
lo be arranged and to act, is destroyed. And, though it may be 
conceived that when the molecules of bichloride of tin arc po- 
larized as ‘wholes by the induction across them, the positive 
polar force might accumulate on the one particle of tin whilst 
the negative polar force accumulated on the two particles of 
chlorine associated with it, and that these might respectively 
travel right and left to unite with other two of chlorine and one 
of tin, in analogy with what happens in cases of compounds 
consisting of single proportions, yet this is not altogether so 
evident or probable. For when a particle of tin combines with 
two of chlorine, it is difficult to conceive that there should not 
he some relation of the three in the resulting molecule antilo- 
gous to fixed position, the one particle of metal being perhaps 
symmetrically placed in rotation to the two of chlorine: and, it 
is not difficult to conceive of such particles that they could not 
assume that position dependent both on their polarity and the 
relation of their elements, which appears to bo the first step in 
the process of electrolyzation (1315. 1705.), 

§.21. Relation of the electric and magnetic forces. 

1701). T have already ventured a few speculations respecting 
the probable relation of magnetism, as the transverse force of 
the current, to the divergent or transverse force of the lines of 
inductive action belonging to static electricity (1058, &e.). 

1710. In the further consideration of this subject it ap- 
peared to me to he of the utmost importance to ascertain, if' pos- 
sible, whether this lateral action which we call magnetism, or 
sometimes 'the induction of electrical currents (20. 1018, &c.), 
is extended to a distance hy the action of the intermediate par- 
tides in analogy with the induction of static electricity, or the 
various effects, such as conduction, discharge, &c., which are 
dependent on that induction ; or, whether its influence at a dis- 
tance is altogether independent of such intermediate particles 
( 1002 .). 

1711. I arranged two magneto-electric helices with iron cores 
end to efld, but with an interval of an inch and three quarters 
between them, in which interval was placed the end or pole of 
a bar magnet. It is evident, that on moving the magnetic pole 
from one core towards the other, a current would tend to form 

2 n 



546 Magnetic induction through shell-lac, [Sekies XI Y. 

in both helices, in the one because of the lowering, and in the 
other because of the strengthening of the magnetism induced 
in the respective soft iron cores. The helices were connected 
together, and also with a galvanometer, so that these two cur- 
rents should coincide in direction, and tend by their joint force 
to deflect the needle of the instrument. The whole arrange- 
ment was so effective and delicate, that moving the magqjytic 
pole about the eighth of an inch to and fro two or three times, 
in periods equal to those required for the vibrations of the gal- 
vanometer needle, was sufficient to cause considerable vibra- 
tion in the latter ; thus showing readily the consequence of 
strengthening the influence of the magnet on the one core and 
helix, and diminishing it on the other. 

1712. Then without disturbing the distances of the magnet 
and cores, plates of substances were interposed. Thus calling 
the two cores A and B, a plate of shell -lac was introduced be- 
tween the magnetic pole and A for the time occupied by the 
needle in swinging one way ; then it was withdrawn for the time 
occupied in the return swing; introduced again for another equal 
portion of time ; withdrawn for another portion, and so on eight 
or nine times; but not the least effect was observed on the needle. 
In other cases the plate was alternated, i. e. it was introduced 
between the magnet Slid A for one period of time* withdrawn 
and introduced between the magnet and 13 for the second period, 
withdrawn and restored to ite first place for the third period, 
and so on, but with no effect on the" needle. 

1713. In these experiments shell-lac in plates 09 of an inch 
in thickness, sulphur in a plate 0*9 of an inch in thickness, and 
copper in a plate 07 of an inch in thickness were used without 
any effect. And I conclude that bodies, contrasted by the ex- 
ttfeme&of conducting and insulating power, and opposed to each 
other as strongly as Inetals, air, and sulphur, show no difference 
with respect to magnetic forces when placed in their lines of 
action, at least under the circumstances described. 

1714. With a plate of iron, or even a small piece of that 
metal, as the head of a nail, a very different effect was produced, 
for then the galvanometer immediately showed its sensibility, 
and tlie perfection of the general arrangement. 

171*5. I arranged matters so that a plate of copper 0*2 of an 
inch in thickness, and ten inches in diameter, should have the 
part near the edge interposed between the magnet, and the core. 



June 1838.] through copper , sulphur, $c. 547 

in which situation it was first* rotated rapidly, and then held 
•quiescent alternately., for periods according with that required 
for the swinging of the needle ; hut not the least effect upon 
the galvanometer was produced. 

1716. A plate of shell-lao 0*6 of an inch in thickness was ap- 
plied in the same mannci* hut whether rotating or not it pro- 
duced no effect. 

1717. Occasionally the plane of rotaton was directly across 
the magnetic curve: at other times it was made as oblique as 
possible ; the direction of the rotation being also changed in 
different experiments, but not the least effect was produced. 

1718. I now' removed the helices with their soft iron cores, 
and replaced them by two Jfat bolins wound upon eardboaid, 
each containing forty-two feet of silkul copper wire, and hav- 
ing no associated iron. Otherwise the arrangement was as 
before, and exceedingly sensible' ; for a \ery slight motion of 
the magnet between the helices produced an abundant vibration 
of the galvanometer needle. 

1719. The introduction of plates of shell-lac, sulphur, or copper 
into the intervals between the magnet and these helices (1713.), 
produced not the least effort, w hot hi r the former wore quies- 
cent or in rapid revolution (1715.), So here no evidence of 
the influence of the intermediate pavtiMes could he obtained 
(1710.). 

1720. The magnet was then removed and replaced by a fiat 
helix, corresponding to tlie* two former, the three being paral- 
lel to each other. The middle helix was so arranged that a 
voltaic current could he sent through it at pleasure. The for- 
mer galvanometer was removed, and one with a double coil em- 
ployed, one of the lateral heliet s being connected w ith one coil, 
and the other helix with the other coil, in such manner that 
when a voltaic current was sent through' the middle helix its 
inductive action (26.) on the lateral helices should cause cur- 
rents in them, having contrary directions in the coils of the 
galvanometer. By a little adjustment of the distances these in- 
duced currents were rendered exactly equal, and the galvano- 
meter n^dle remained stationary notwithstanding their frequent 
production in the instrument. I will call the middle coil C, 
and the external coils A and B. 

1721. A plate of copper 0*7 of an inch thick and six inches 
square, was placed betw een coils C and their respective di- 

2 n 2 



548 Induction of currents across dielectrics, [Sekies XIV. 

stances remaining unchanged; and then a voltaic current from 
twenty pairs of 4-inch plates was sent through the coil C, and* 
intermitted, in periods fitted to produce an effect on the gal- 
vanometer (1712.), if any difference had been produced in the 
effect of C on A and 13. But notwithstanding the presence of air 
in one interval and copper in the other, the inductive effect was 
exactly alike on the two coils, and as if air had occupied both 
intervals. So that notwithstanding the facility with which any 
induced currents might form in the thick copper plate, the coil 
outside of it was just as much affected by the central helix C 
as if no such conductor as the copper had been there (65.). 

1722. Then, for the copper plate was substituted one of sul- 
phur 0*9 of an inch thick ; still the results were exactly the 
same, i. e. there was no action at the galvanometer. 

1723. Thus it appears that when a voltaic current in one 
wire is exerting its inductive action to produce a contrary or a 
similar current in a neighbouring wire, according as the pri- 
mary current is commencing or ceasing, it makes not the least 
difference whether the intervening space is occupied by such 
insulating bodies as air, sulphur, and shell-lac, or such conduct- 
ing bodies as copper, and the other non-magnetic metals. 

1724. A correspondent effect was obtained with the like 
forces *when resident a magnet thus. A single flat helix 
(1718.) was connected with a galvanometer, and a magnetic pole 
placed near to it ; then by mewing the magnet to and from tin' 
helix, or the helix to and from the magnet, currents were pro- 
duced indicated by the galvanometer. 

1725. The thick copper plate (1721.) was afterwards inter- 
posed between the magnetic pole and the helix ; nevertheless 
on moving these two and fro, effects, exactly the same in direc- 
tion aipi amount, were obtained as if the copper had not been 
there. So also on introducing a plate of sulphur into the in- 
terval, not the least influence on the currents produced by mo- 
tion of the magnet or coils could be obtained. 

1726. These results, with many others which I have not 
thought it needful to describe, would lead to the conclusion 
that (judging by the amount of effect produced at a« distance 
by forces transverse to the electric current, i. e, magnetic 
forces), the intervening matter, and therefore the intervening 
particles, have nothing to do with the phenomena ; or in other 
words, that though the inductive force of static electricity 



June 1838.] Relation of magnetic induction to dielectrics . 519 

ip transmitted to a distance by the action of the intermediate 
particles (1161. 1666.), the transverse inductive force of cur- 
rents, which can also act at a distance, is not transmitted by 
the intermediate particles in a similar way. 

1727. It is however very evident that such a conclusion can- 

not be considered as proved. Thus when the metal copper 
is between the pole and the helix (1715. 1719. 1725.) or be- 
tween the two helices (1721.) we know that its particles are af- 
fected, and can by proper arrangements make their peculiar 
state for the time \ery evident by the production of cither 
electrical or maguetioal effects. It seems impossible to con- 
sider this effect on the particles of the intervening matter as 
independent of that produced by the induetrie coil or magnet 
C, on the indueteous eoil^or core A (1715. 1721.) ; for since the 
inductoous body is equally affected by the induetrie body whe- 
ther these intervening and affected particles of copper are pre- 
sent or not (J723. 1725.), such a supposition would imply that 
the particles so affected had no reaction back on the original 
induetrie forces. The more reasonable conclusion, as it ap- 
pears to me, is, to consider these' affected particles as efficient 
in continuing tin* action onwards from the induetrie to the in- 
ductcous body, and by this very communication producing the 
effect of no loss of induced power sit the latter. * 

1728. But then it may be asked what is the relation of the 
particles of insulating bodies, sfleh as air, sulphur, or lac, when 
they intervene in the line* of magnetic action ? The answer to 
this is at present merely conjectural. I have long thought 
there must be a particular condition of such bodies correspond- 
ing to the state which causes currents in metals and other con- 
ductors (26. 53, 191. 201. 213.); and considering that the 
bodies are insulators one would expect that state to he oife of 
tension. I have by rotating non-conducting bodies near mag- 
netic poles and poles near them, and also by causing powerful 
electric currents to be suddenly formed and to cease around 
and about insulators in various directions, endeavoured to make 
some such state sensible, but have not succeeded. Neverthe- 
less, as*any such state must be of exceedingly low intensity, be- 
cause of the feeble intensity of the currents which are used to 
induce it, it may well be that the state may exist, and may be 
discoverable by* some more expert experimentalist, though I 
have not been able to make it sensible. ' 



550 Magnetic induction and contiguous particles . [Series X1Y. 

1729. It appears to me possible, therefore, and even proba- 
ble, that magnetic action may be communicated to a distance 0 
by the action of the intervening particles, in a manner having 
a relation to the way in which the inductive forces of static 
electricity are transferred to a distance (1677.) ; the intervening 
particles assuming for the time more*or less of a peculiar con- 
dition, which (though with a very imperfect idea) I have several 
times expressed by the term electro-tonic state (60. 242. 1111. 
1661.). I hope it will not be understood that I hold the settled 
opinion that such is the case. I would rather in fact have 
proved the contrary, namely, that magnetic forces are quite in- 
dependent of the matter intervening between the induetric and 
the inducteous bodies ; but I cannot get over the difficulty 
presented by such substances as copper, silver, lead, gold, 
carbon, and even aqueous solutions (201. 213.), which though 
they are known to assume a peculiar state whilst intervening 
between the bodies acting and acted upon (1727.), no more in- 
terfere with the final result than those which have as yet had 
no peculiarity of condition discovered in them. 

1730. A remark important to the whole of this investigation 
ought to be made here. Although I think the galvanometer 
used as I have described it (1711. 1720.) is quite sufficient to 
prove that the final amount of action on each of the two coils 
or the two cores A and B (1713. 1719.) is equal, yet there is 
an effect. which may be consequent on the difference of action 
of two interposed bodies which it w’Duld not show. As time 
enters as an element into these actions* (125.), it is very pos- 
sible that the induced actions on the helices or cores A, B, 
though they rise to the same degree when air and copper, or 
air and lac are contrasted as intervening substances, do not do 
so ki tl^e same time ; and yet, because of the length of time 
occupied by a vibratioii of the needle, this difference may not 
be visible, both effects rising to their maximum in periods so 
short as to make no sensible portion of that required for a vi- 
bration of the needle, and so exert no visible influence upon it. 

• 

1731. If the lateral or transverse force of electrical currents, 
or what appears to be the same thing, magnetic power, could 
be proved to be influential at a distance independently of the 

* See Annales cLe Chemie, 1833, tom. li. pp. 422, 428. 



June 1838.] Magnetic and electric forces distinguished. 55 L 

intervening contiguous particles, then, as it appears to me, a 
real distinction, of a high and imp >rtaut kind, would be esta- 
blished between the natures of these two forces (105 1. 1 00 l.) . 
I do not mean that the powers are independent of each other 
and might be rendered separatively active, on the contrary they 
are probably essentially associated (10 3 k), but it by no means 
follows that they are of the same nature. In common statical 
induction, in conduction, and in electrolyzation, the forces at 
the opposite extremities of the particles which coincide with 
the lines of action, and have commonly been distinguished by 
the term electric, arc polar, and in the cases of contiguous par- 
ticles act only to insensible distance's; whilst those which are 
transverse to the direction of these lines, and are called mag- 
netic, are circumferential, act at a distance, and if not through 
the mediation of the intervening particles, have their relations 
to ordinary matter entirely unlike those of the electrical forces 
with which they are associated. 

1732. To decide this question of* the identity or distinction 
of the two kinds of power, and establish their true relation, 
would be exceedingly important. The q notion seems fully 
within the reach of experiment, and oilers a high reward to him 
who will attempt its settlement. 

1733. I have already expressed a lmpc of finding qn effect 
or condition which shall be to statical electricity what magnetic 
force is to current electricity (l,05tt.). If Leonid have proved 
to my own satisfaction fl*tt magnetic forces extended their in- 
fluence to a distance by the conjoined action of the intervening 
particles in a manner analogous to that of electrical forces, then 
I should have thought that the lateral tension of the lines of 
inductive action (1059.), or that state* so often hinted at as the 
electro- tonic state (1001. 1002.), was this related condition of 
statical electricity. 

1734. It may he said that the state of no lateral action is to 
static or inductive force the equivalent of magnetism to current 
force; but that can only he upon the view that electric and 
magnetic action are in their nature essentially different (1604.). 
If thef are the same power, the whole difference in the results 
being the consequence of the difference of direction , then the 
normal or undeveloped state of electric force will correspond 
with the state of no lateral action of the magnetic state of the 
force ; the electric current will correspond with the lateral ef- 



552 Magnetic and electric forces compared. [Series XIV. 

fects commonly called magnetism : but the state of static in- 
duction which is between the normal condition and the current" 
will still require a corresponding lateral condition in the mag- 
netic series, presenting its own peculiar phenomena ; for it can 
hardly be supposed that the normal electric, and the inductive 
or polarized electric condition, can both have the same lateral 
relation. If magnetism be a separate and a higher relation of 
the powers developed, then perhaps the argument which presses 
for this third condition of that force would not be so strong. 

1735. I cannot conclude these general remarks upon the re- 
lation of the electric and magnetic forces without expressing 
my surprise at the results obtained with the copper plate (1721. 
1725.). The experiments with the flat helices represent one 
of the simplest eases of the induction of electrical currents 
(1720.) ; the effect, as is well known,*' consisting in the produc- 
tion of a momentary current in a wire at the instant when a 
current in the contrary direction begins to pass through a 
neighbouring parallel wire, and the production of an equally 
brief current in the reverse direction when the determining 
current is stopped (26.). Such being the ease, it seems very 
extraordinary that this induced current which takes place in 
the helix A when there is only air between A and C (1720.) 
should be equally strong when that air is replaced by an enor- 
mous mass of that excellently conducting metal copper (17.21.). 
It might have been supposed that this mass would have allowed 
of the formation and discharge of almost any quantity of cur- 
rents in it, which the helix C was competent to induce, and so 
in some degree have diminished if not altogether prevented 
the effect in A : instead of which, though we can hardly doubt 
that an infinity of currents are formed at the moment in the 
copper plate, still not the smallest diminution ov alteration of 
the effect in A appears* (65.). Almost the only way of recon- 
ciling this effect with generally received notions is, as it appears 
to me, to admit that magnetic action is communicated by the 
action of the intervening particles (1729. 1733.). 

1736. This condition of things, which is very remarkable, 
accords perfectly with the effects observed in solid * helices 
where wires are coiled over wires to the amount of five or six 
or more layers in succession, -no diminution of effect on the 
outer ones being occasioned by those within. 



J un’e 1838,] 


Electrical excitation. 


553 


§ 22. Note on electrical excitation. 

1737. That the different inodes in which electrical excite- 
ment takes place will some day or other be reduced under one 
common law can hardly be doubted, though tor the present we 
are bound to admit distinctions. It will be a great point gained 
when these distinctions arc, not removed, hut understood. 

1738. The strict relation of the electrical and chemical 
powers renders the chemical mode of excitement t he most in- 
structive of all, and the ease of two isolated combining parti- 
cles is probably the simplest that we possess. Here however 
the action is local, and we still want such a test of electricity as 
shall apply to it, to cases of current electricity, and also to those 
of static induction. Whenever by virtue of the previously 
combined condition of sonfe of the acting particles (023.) we arc 
enabled, as in the voltaic pile*, to expand or convert the local 
action into a current, then chemical action can be traced through 
its variations to the production of alt the phenomena of tension 
and the stalic state, these being in every respect the same as 
if the electric forces producing them had been dev (doped by 
friction. 

1739. It was Berzelius,! believe, who tirst spoke of thehiptness 
of certain particles to assume opposite* states when in |ircsenee 
of each other (959.). Hypothetically we may suppose these 
states to increase in intensity Ijy increased approximation, or 
by heat, &c. until at a curtain point combination, occurs, ac- 
companied by such an arrangement of the forces of the two 
particles between themselves as is equivalent to a discharge, 
producing" at the same time a particle which is throughout a 
conductor (1700.). 

1710. This aptness to assume an excited electrical state 
(which is probably polar in those forming non-conducting mat- 
ter) appears to be a primary fact, and to partake of the nature 
of induction (1162.), for the particles do not seem capable of 
retaining their particular state independently of each other 
(1177.) or of matter in the opposite state. What appears to be 
definite about the particles of matter is their assumption of a 
particular state, as the positive or negative, in relation to each 
other, and not of either one or other indifferently; and also 
the acquirement of force up to a certain amount. 

1741. It is easily conceivable that the same force which causes 



554 Electrical excitation : chemical. [Series XIV. 

local action between two free particles shall produce current 
force if one of the particles is previously in combination, forrtl-, 
ing part of an electrolyte (923. 1738.). Thus a particle of zinc, 
and one of oxygen, when in presence of each other, exert their 
inductive forces (1740.), and these at last rise up to the point 
of. combination. If the oxygen bc # previously in union with 
hydrogen, it is held so combined by an analogous exertion and 
arrangement of the forces ; and as the forces of the oxygen 
and hydrogen are for the time of combination mutually engaged 
and related, so when the superior relation of the forces between 
the oxygen and zinc come into play, the induction of the former 
or oxygen towards the metal cannot be brought on and in- 
creased without a corresponding deficiency in its induction to- 
wards the hydrogen with which it is in combination (for the 
amount of force in a particle is considered as definite), and the 
latter therefore has its force turned towards the oxygen of the 
next particle of water ; thus the effect may be considered as 
extended to sensible distances, and thrown into the condition 
of static induction, which being discharged and then removed 
by the action of other particles produces currents. 

. 1742. In the common voltaic battery, the current is occasion- 
ed by the tendency of the zinc to take the oxygen of the wa- 
ter from the hydrogen^ the effective action being at the place 
where t‘ he oxygen leaves the previously existing electrolyte. 
But Schoenbcin has arranged a battery in which the effective 
action is at the other extremity of tlijs essential part of the ar- 
rangement, namely, where oxygen goes to the electrolyte*. 
The first may be considered as a case where the current is put 
into motion by the abstraction of oxygen from hydrogen, the 
latter by that of hydrogen from oxygen. The direction of the 
electric current is in both cases the same, when referred to the 
direction in which the^ elementary particles of the electrolyte 
are moving (923. 962.), and both are equally in accordance 
with the hypothetical view of the inductive action of the parti- 
cles just described (1740.). 

1743. In such a view of voltaic excitement, the action of the 
particles may be divided into two parts, that which* occurs 
whilst the force in a particle of oxygen is rising towards a par- 

* Philosophical Magazine, 1838, xii. 22o, 316. See also De la Rive’s results 
with peroxide of manganese. Annales de Chimie, 1836, lxi. p. 40. — Dec, 
1838, 



555 


June 1833.] Electrical excitation : friction . 

tide of zinc acting on it, and failing towards the particle of hy- 
drogen with which it is associated (this beiug the progressive 
period of the inductive action), and that which occurs when 
the change of association takes place, and the particle of oxy- 
gen leaves the hydrogen and combines with the zinc. The 
former appears to be tha^ which produces the current, or if 
there be no current, produces the state of tension at the ter- 
mination of the battery ; whilst the latter, by terminating for 
the time the influence of the particles which have been active, 
allows of others coining into play, and so the efleet of current 
is continued. 

1744. it seems highly probable, that excitement by friction 
may very frequently be of the same character. Wollaston en- 
deavoured to refer such excitement to chemical action*; but 
if by chemical action ultiifuite union of the acting particles is 
intended, then there are plenty of Cases which arc opposed to 
such a view. Davy mentions some such, and tor my own part 
1 feel no difficulty in admitting other means of electrical excite- 
ment than chemical action, especially if by chemical action is 
meant a final combination of the particles. 

17 15. Davy refers experimentally to the opposite states 
which two particles having opposite chemical relations can as- 
sume when they are brought into the, close vicinity of each 
other, but not allowed to combine t* This, 1 think, is the first 
part of the action already described (17 13.) ; but in my opinion it 
cannot give rise to a continuous current unless combination 
take place, so as to allow other particles to act successively in 
the same manner, and not even then unless one set of the par- 
ticles be present as an element of an electrolyte (923. 903.) ; 
i. e. mere quiescent contact alone without chemical action does 
not in such eases produce a current . 

1746. Still it seems very possible that such a relation may 
produce a high charge, and thus give rise to excitement by 
friction. When two bodies arc rubbed together to produce 
electricity in the usual way, one at least must be an insulator. 
During the act of rubbing, tlic particles of opposite kinds must 
be broftght more or less closely together, the few which are 
most favourably circumstanced being in such close contact as 
to be short only of that which is consequent upon chemical 
combination. At such moments they may acquire by their 
* Philosophical Transactions, 1801, p. 427. . t Ibid. 1807, p. 34. 



556 Electrical excitation . [Series XIV. 

mutual induction (1710.) and partial discharge to each other, 
very exalted opposite states, and when, the moment after, the}! 
are by the progress of the rub removed from each other’s 
vicinity, they will retain this state if both bodies be insulators, 
and exhibit them upon their complete separation. 

1747. All the circumstances attending friction seem to me to 
favour such a view. The irregularities of form and pressure 
will cause that the particles of the two rubbing surfaces will be 
at very variable distances, only a few at once being in that very 
close relation which is probably necessary for the development 
of the forces ; further, those which are nearest at one time will 
be further removed at another, and others will become the 
nearest, and so by continuing the friction many will in succes- 
sion be excited. Finally, the lateral direction of the separation 
in rubbing seems to me the best fitted to bring many pairs of 
particles, first of all into that close vicinity necessary for their 
assuming the opposite states by relation to each other, and 
then to remove them from each other’s influence whilst they 
retain that state. 

1748. It would be easy, on the same view, to explain hypo- 
thetically, how, if one of the rubbing bodies be a conductor, as 
the amalgam of an electrical machine, the state of the other 
when it comes from under the friction is (as a mass) exalted ; 
but it would be folly to go far into such speculation before that 
already advanced has been confirmed or corrected by fit expe- 
rimental evidence. I do not wislv it to be supposed that 1 
think all excitement by friction is of this kind ; on the contrary, 
certain experiments lead me to believe, that in many eases, and 
perhaps in all, effects of a thermo-electric nature conduce to 
the ultimate effect ; and there are very probably other causes 
of electric disturbance influential at the same time, which we 
have not as yet distinguished. 

Royal Institution , 

June 1838. 


THE ENT), 



INDEX. 


N.B. A dash rule represent s the italics immediately preceding it. The references 
are sometimes to the individual paragraph, and sometimes to that in conjunction with 
those which follow. 


Absolute charge of matter, 1109. 

quantity of electricity in matter, 852, 

801,873. ' ‘ • 

Acetate of pot assn, its electrolysis, 749. 
Acetates, their electrolysis, 774. 

Acetic acid, its electrolysis, 773, 

Add, nitric, formed in air Ip a spark, 324. 

, or alkali, alike in exciting the pile, 

932. 

- , transference of, 525. 

(nr halfcry, its nature and strength, 

1128, 1137. 

1 nitric, the best, 1138. 

1 cdlVet of different strengths, 

1139. 

in voltaic pile, does not evolve the 

electricity, 925, 933. 

- , its use, 925. 

Acids and bases, their relation in the vol- 
taic pile, 927, 933. * 

Active lottery, general remarks on, 1034, 

1 130. 

Adhesion of fluids to metals, .1038. 
Advantages of a new voltaic battery. 1132. 
Affinities, chemical , opposed voltaically, 
891,904,910. 

— — , their relation in the active pile, 949. 
Air, its attraction by surfaces, 022. 

— , charge of, 1173. 

, , by brush, 1434, 1441. 

, ( by glow, 1537, 1543. 

. convective currents in, 1572, 1570, 

1581. 

, dark discharge in, 1548. 

— - — , disruptive discharge in, 1359, 1400, j 
1425, 1520. I 

, induction in, 1208, 1215, 1284,1302. j 

, its insulating and conducting power, ■ 

441, 1332, 1330, 1302. j 

, its rarefaction facilitates discharge, ; 

1375. j 

* , electrified, 1443. ' 


Air, electro-chemical decompositions in, 
454. 1023. 

, hot, discharges Voltaic buttery. 271, 
271 

, poles of, 455. 401. 559. 

, positive and negative brush in, 1407, 
1472, 1470. 

1 , glow in, 1520, 1530. 

, • *q>ark in, I 1*5, 

! , rarefied, brush in, 1451, I 150. 

. retention of electricity on eonduc- 
tors by, 1377, J39X. 

1 , specific ind active < opacity »/’ 1281. 

| , . not, \aried by temperature ot* 

pressure, 1287, 1288. 

A l loti ha^sf rung exciting powftr in voltaic 
pile, 884, 931, 941. 

, t rnnsferenee of, 525. 

•Ainahptnta/fd zinc, its condition, 1000. 

! , how prepared, 803. 

i , its isluuhlc use, 803, 999. 

| - , battery, .1001. 

| Am, no, tin, nature, of its elect roly. sis, 748. 

- , 1 -olut ion of, a bail conductor, 554,748, 

Ampere’s inductive results, 78, 255, 379 
! not'-. 

Anions defined. 005, <824. 

- , table ol, 847. 

— re la I ed t h rough the ent ir<? cireu it, 963. 

, - , their action in t,l»o voltaic pile, 924. 

| — , their direction of transfer, 962. 

; Anode defined, 663. 

Antimony, its relation to magneto-electric 
induction, 139. 

, chlorine of, not an electrolyte, 690, 

796. 

, oxide of, how affected by the electric 

current, 801. 

, supposed new protoxide, 693. 

sulphuret, 094. 

Animal electricity . its general characters 
considered, 351. 



658 


INDEX. 


Animal electricity is identical with other 
electricities, 351, 360. 

, its chemical force, 355. 

, enormous amount, 359. 

, evolution of heat, 353. 

, magnetic force, 354. 

• , physiological effects, 357. 

, spark, 358. 

~ — , tension, 352. 

Apparatus, inductive, 1187- See Induc- 
tive apparatus. 

Arago's magnetic phenomena, their nature, 
fel, 120. 

, reason why no effect if no motion, 126. 

, direction of motion accounted for, 121. 

due to induced electric currents, 1 19, 

248. 

like electro-magnetic rotations in 

principle, 121. 

not due to direct induction of mag- 
netism, 128, 138, 215, 243, 248. 

obtained with electro-magnets, 129. 

produced by conductorsonly,130,215. 

, time an element in, 124. 

, Babbage and llersehel’s results ex- 
plained, 127. 

Arago’s experiment, Sturgeon’s form of, 

249. 

Associated voltaic circles, 989. 

Atmospheric balls of tiro, 1641. 

electricity, its chemical action, 336. 

Atomic number judged of from electro- 
chemical equivalent, 851. 

Atoms of matter, 869, 1703. 

, tlieiq electric power, 856,«860. 

Attraction of particles, its influence in 
Dobereiner’s phenomena, 619. 
Attractions, electric, their force, 1622 note* 

, chemic , produce current force, 852, 

918, 947, 996, 1741. 

local force, 852, 921, 947, 959, 

1739. 

, hygrometric, 621. 

Aurora borealis referred to magneto-elec- 
tric induction, 192. 

Axis of power, the electric current an, 
517, 1627, 1642. 

Balls of fire, atmospheric, 1641?* 

Barlow’s revolving globe, magnetic effects 
explained, 137, 160. 

Barry, decomposed bodies by atmospheric 
electricity, 338. 

Bas^s and acids, their relation in the pile, 
927. 

Battery, Leyden, that generally used, 291. 
Battemj, voltaic , its nature, 856, 989. 

, origin of its power, 878, 916. 

, net in contact, 887, 915. 

, chemical, 879, 916, 919, 1741. 

— } oxidation of the zinc, 91 9, 944. 


^1 12*0 ' V ° ltaic ' * ts c * rcu l at * n f? force, 858, 

, its local force, 1120. 

, quantity of electricity circulating, 

, intensity of electricity circulating 

990, 993. b ’ 

, intensity of its current, 909, 994. 

a, increased, 905, 989. 

, its diminution in power, 1 035. 

from adhesion of fluid, 1003. 

1036. 

, — peculiar state of metal 

1040. 

exhaustion of cl targe 

1042. 

irregularity of plates, 

1045, 1146. 

, use of metallic contact in, 893, 896. 
, electrolytes essential to it, 921. 

, why, 858, 923. 

, state of metal and electrolyte before 
contact, 946. 

, conspiring action of associated aili- 
nities, 989, 

, purity of its zinc, 1144. 

use of amalgamated zinc in, 999. 

, plates, their number, 1151. 

, size, 1154. 

, vicinity. 1148, 

, immersion, 1 150. 

relative age, 1146. 

, — — foulness. 1145. 

, excited hy acid, 880, 926, 1137. 

, alkali, 931, 934, 941. 

, sulphuretted solutions, 943. 

, the acid, its use, 925. 

, acid for, 1128, 1137. 

j. nitric acid best for, 1137. 

, construction of, 989, 1001, 1121. 

— — , with numerous alternations, 989. 

, Hare’s, 1123. 

, general remarks on, 1034, 1136. 

, simultaneous decompositions with, 

1156. 

■ , practical results with, 1136. 

, improved , 1001, 1Q06, 1120. 

} its construction, 1124. 

, , power, 1125, 1128. 

, , advantages, 1132. 

. , disadvantages, 1132. 

Batteries, voltaic, compared, 1126. 
Becquerel, his important secondary re- 
sults, 745, 781. 

Berzelius, his view of combustion, 870, 959. 
Biot’s theory of electro-chemical decom- 
position, 486.. 

Bismuth, its relation to magneto-electric 
induction, 139. 

Bodies classed in relation to the electric 
current, 823. 



INDEX, 


551) 


Bodies classed in relation to magnetism, Cathode described, 663, 824. 

2£>5. • Cations, or eathions, described, <>C»o, 824. 

— electrolyzable, 824. , table of, 847. 

Bonijol decomposed substances by atmo- , direction of their transfer, 002. 

spheric electricity, 3.%. , ore in relation through the entire 

Boracic acid a bad conductor, 408. circuit, 003. 


Brush, electric, 1425. 

, produced, 1425. 

, not affecttd by nature of conduc- 
tors, 14f>4, 1473. 

is affected by the dielectrics, 1455, 
1403, 1475, 

, not dependent on current of air, 

1440. 

, proves molecular action of dielec- 
tric, 1440, 1450. 

, its analysis, 1427, 1433. 

.nature, 113*4, .1441, 1447- 

, form, 1428, 1440, 3451. 

, ramifications , 1430. 

- — — . their coalescence, 1453. 

, sound, 1420, 1431. * 

~~ , requisite intensity for, 1440. 

, has sensible duration, 1437. 

, is intermitting, 1427. 1431, 1451. 

, light of, 1444, 1445, 1451. 

, - , in different gases, 1440, 1454. 

- , dark M 444. 1552. 

, passes into spark, 1448. 

, spark and glow relation of, .1533, 
1530, 1542. 

— , in gases, 1454, 1403, 1470. 

, oxygen, 1457, 1470. 

, nitrogen, 1458, 1470. 

, hydrogen, 1450, 1470. 

‘oal -gas, 1400, 1470. 

, carbonic acid gas, 1401, 1470. 

, muriatic acid gas, 1402, 1470. 

rare air, 1451, 1455, 1474. 

, oil of turpentine, 1452." 
positive, 1455, J407, 1184. 

, neguiiri , 1408, 1472, 1484. 

, , of rapid recurrence, 1408, 

1491. 

, positive and negative in different 

gases, 1455, 1475, 1500. 

Capacity, specific inductive , 1252. 

. See Specific induethe capacity. 

Carbonic acid gas facilitates formation of 
spark, 1463. 

, brush in, 1401, 1470. 

, glow in, 1534. 

, spark in, 1422, 1403. 

, positive and negative brush in, 1470. 

, •discharge in, 1510. 

, non-interference of, 045, 052. 
Carbouig oxide gas, interference of, 645, 
052. 

Carrying discharge, 1562. 

. ike Discharge convective. 


Characters of electricity, table of. 300. 

— — the electric current, constant, 1018, 
10)27. 

voltaic electricity, 208. 

- ordinary electricity, 284. 

magneto-electricity, 343. 

bermo-olectricity, 349. 

— r- animal electricity, 351. 

Charge, Jne, 1084. 

* is always induction, 1171, 1177, 

1300. 1682. 

— • - on surface of conductors : why, 1301. 

, infiaeacc of form on. 1302. 

, distance on, 1303. 

— lo!-s of, by connection, 1509, 

— - , renaned from good insulators, 1203, 

— of mat ter absolute. 1 109. 

— of air, 1173. 

— b v brush, 1434, 1 1 11. 

— by glow. 1520, 1537, 1543. 

— of particles m air, 1504- 

— of oil of 1 urpeni ine, 1172, 
ofimluct iu i npparnt us div ided, 1208. 

— , residual, of a Leulen jar, 1249. 

chemical, for hatting, good, 1 137. 

weak and exhausted, 1042, 

1143. 

Clnmieuf action, the, exciting the pile is 
oxidat ivii. 921 . 

— su per induced hy metals, 504. 

, plat iua, 504, til 7, 030. 

t tested by iodide of potassium, 315. 

Chemical actions, distant, opposed to each 
other. 891, 910. 1007. 

Uiemical ajfinity indue need by mechanical 
forces, 050. 

j transferable through metals, 918, 

! statical or local, 852, 921, 947, 959. 

! current, 852, 918, 947, 990. 

' Chemical di con position hy voltaic elect ri- 
| city, 278' 450, 001. 

! common electricity, 30U, 455. 

} mugbclo-clectricity, 340. 

I - thermo-electricity, 349. 

animal electricity, 355. 

. See Dee< an posit ion elect ro-chernioal. 

Chemical and electrical forces identical, 
877, 918, 947, 900, 905, 1031. 

Chloride of antimony not an electrolyte, 
690. 

| — - — lead, its electrolysis, 794, 815. 

, electrolytic intensity for, 978. 

- silver, its electrolysis, 541, 813, 902. 

, electrolytic intensity for, 979. 

- tin, its electrolysis, 789, 819. 



660 INDEX. 


Chlorides in solution, their electrolysis, 766, 

fusion, their electrolysis, 789, 813. 

Circle of anions and cathions, 903. 

Circles , simple voltaic, 875. 

, associated voltaic, 989. 

Circuit, voltaic, relation of bodies in, 962. 
Classification of bodies in relation to mag- 
netism, 255. 

the electric current, 823, 847. 

Cleanliness of metals and ol her solids, 033. 
Clean plat inn, its characters, 033, 717. 

• its power of effecting combination, 

590, 005, 017, 032. 

— . See Plates of platina. 

Coal gas, brush in, 1400. 

, dark discharge in, 1550. 

, positive and negative brush in, 1470. 

positive and negative discharge in, 
1515. 

, spark in, 1422. 

Goliad on on magnetic force of common 
electricity, 28V). 

Collectors, magneto-electric, 86. 
Combination effected by metals, 504, 008. 

solids, 504, til 8. 

poles of platina, 500. 

platina , 504, 508, 571, 590, 630. 

j as plates, 509. 

, as sponge, 009, 030. 

— — - — — , cause of, 590, 010, 625, 656. 

, how, 630. 

, interferences with, 638,652,655. 

- retarded by olefiant gas, 040. 

carbonic oxide, 045, 052. 

- c an lphurot of cadbon, 050. 

ether, 651. 

other substances, 649, 053, 

054. 

Compn rison of volt a ic bat lories,! 1 20, 1140. 
Conditions , general, of voltaic decomposi- 
tion, 009. 

, new, of electro-chemical decompo- 
sition. 453. 

Conducting power measured by a magnet, 
210. 

of solid electrolytes, 419. 

of water, constant, 984. 

Conductions 418, 1320. 

— — , its nature, 1320, 1326, 1011. 
of two kinds, 987. 

, preceded by induction, 1329, 1332, 

1338. 

• and insulation, cases of the same 

. kind, 1320, 1326, 1336, 1338, 1561. 

, its relation to the intensity of the 

current conducted, 419. 

— — common to all bodies, 444, 449. 

by a vacuum, 1613. 

by lac, 1234, 1324. 

by sulphur, 1241, 1328. 

by glass, 1239, 1324. 


Conduction by spermaceti, 1240, 1323. 

by gases, 1336. 

slow, 1233, 1245, 1328. 

■ affected by temperature, 445, 1339. 
by metals diminished by heat, 45 
445. 

increased by heat, 432, 441, 445. 
of electricity and heat, relation of, 

4tf>. 

, simple, can occur in electrolytes, 967 
983. 

j with very' feeble currents, 970. 

— —by electrolytes without decompi.si- 
lion, 968, 1017, 1032. 

- and decomposition associated m 
electrolytes, 413, 676, 854. 

facilitated in electrolytes, 1355. 

by water bad, 1 159. 

I improved bv dissolved both 

' 984, 1355. 

I — , elect roly tie, stopped, 380, 1 358, 1705. 

J 1 of currents stopped by ice, .“* 81 . 

- conferred by liquefaction, .‘194, 410. 

taken away by to! id if cat ion, 394, 1703. 

, why, 910, 1705. 

, new law of 3i<0, 394. 410. 

, , supposed exception to, 691, 

1340. 

, general results ns to, 443. 

Conductive discharge, 1320. 

Conductors , electrolytic, 474. 

i , magneto-electric, 8(5. 

j , their nature does not nfieet the elec- 

I trie brush, 1454. 

I , size of, affelts discharge, 1372. 

j , form of, a fleet sdiseharge, 1374.1425. 

1 distribution of electricity on, i 36*. 

, , ajjtetcd by form. 1374. 

, distance. 1364, 1371. 

— ~ f -, , — - — air pressure, 1375. 

, , irregulur with equal pressure, 

1378. 

Constancy of the electric current, 1618. 
Constitution of electrolytes as to propor- 
tions, 679, 697, 830, 1768. 

liquidity, 394, 823. 

Contact of metals not necessary for elect ro- 
lization, 879. 

, its use in the voltaic battery, 893. 

not necessary for spark, 915, 956. 
Contiguous particles, their relation to in- 
duction, 1165, 1679. 

- active in electrolysis, 1349, 1703. 
Convection, 1562, 1642. 

or convective discharge. See Dis- 
charge convective. * 

Copper, iron, and sulphur circle, 943. 
Coruscations of lightning, 1464. 
Coulomb’s electrometer, 1180. 

, precautions in its use, 1182, 1180, 

1206. 



INDEX. 


561 


Crystals, induction through, 1689. 

Cube, large, electrified, 1173. 

^ilbesof crystals, induction through, 1692, 


Current chemical affinity, 852, 918, 94-7, 
996. 

Current, voltaic, without metallic contact, 
879, 887. 

Current, electric , 1617. 

defined, 282, 511. * 

, nature of, fill, 667, 1617, 1627. 

, variously produced, 1618. 
produced by chemical action, 879, 
916, 1741. 

- animals, 351. 

friction, 301, 307, 311. 

, heat, 349. 

, — — discharge of static electricity, 

296, 307, 3(53. 

, induction Ay other currents, 6, 

1089. 


, — magnets. 36, 88, 344. 

, evolved in the moving earth, i^l. 

, in the earth, 187. 

, natural standard of direction, 666. 

— , none of one oleetriritv, 1627, 1632, 
1635. 


— , two forces everywhere in it, 3627, 
1632, 1635, 1642. 

, one, and indivisible, 1627. 

-. an axis of power, 517, 1642. 

, constant in ils characters, 1618, 

1627. 

, inexhaustibility of, 1631. 

, its velocity in conduction, 1648. 

, — ~ electrolyzation, 1651. 

regulated by a fine wire, 853 We. 

, affected by heat, 1637. 

stopped by solidification, 381, 

, its section, 498, 504, 1634. 

— — , presents a constant force, 1634. 

, produces chemical phenomena, 1621. 

1 .. _. heat, 1625. 

, its heating power uniform, 1630. 

, produces magnetism, 1653. 

, Forrett’s effects produced by, 1646. 

, induction oj, 1, 6, 232, 241, 1101, 
1048. 

, , on itself, 1048. 

See Induction of electric cur- 


rent. 

its inductive force lateral, 1108. 

, induced in different metals, 193, 

213,201,211. 

, its transverse effects , 1053. 

, constant, 1655. 

> its transverse forces, 1658. 

— — , are in relation to contiguous 

particles, 1664. 

their polarity of character. 

1665. 


Current and magnet, their relation re- 
membered, 38, note. 

Currents in air by convection, 1572, 1581. 

metals by convection, 1603. 

oil of turpentine by convection, 1595, 

1598. 

Curved Hues, induction in, 1215. 

Curves, magnetic, their relation to dy- 
namic induction, 217, 232. 

Daniell on the size of the voltaic metals, 

i i 

I Dark discharge, 1444, 1514. 

See discharge, dark. 

Dates' of some facts and publications, 139, 
note after. 

Davy's theory of elect ro-ehenjieal docont- 
| position, 482. 500. 

I — . electro-chemical views, 965. 

- mercurial cones, convective phono- 

; menu, It 103. 

j Devo/nyosiny force alike in every section of 
| the current, 501, 505. 

I - . variation of, on each particle, 503, 

l h com position and conduction associated 
in electrolytes, 113, 834. 
i , primary and secondary results of, 

; 742, 777. 

; hy co/nnioH electricity , 309, 454. 

• ------ . precautions, 322. 

: Decomposition, electro-chemical , 450,069. 

; - , nomenclature of, 061. 

j - -, new terms relating to, 062. 

, its distinguishing character, 309. 

, hy common electricity, 309, 454, 

, by it single pair of plfttof, 802, 897, 
904, '931. 

- , hy the electric current, 1621. 

- , without metallic contact, 880, 882. 

- , its cause, 891, 904, 91t). 

, , not due to direct attraction or re- 

i pulsion of poles, 493, 497, 530, 542, 540. 

, dependent on previous induction, 

13-15. 

the electric current, 493, 510, 

524, 854. 

t intensit y of current, 905. 

1 chemical affinity of particles, 

5J9, 525, 549. 

, resistance to, 891, 910, 1007. 

, intensity requisite for, 900, 1354. 

, stopped by solidification, 380, 1358, 

1705. 

( retarded by interpositions, 1007. 

, assisted by dissolved bodies, 1355. 

, division of the electrolyte, 1347, 

1623, 1704. 

, transference, 519, 525, 5*38, 550, 

1347, 1706. 

, why elements appear at the poles, 

535. 



562 


INDEX. 


Decomposition, electro-chemical , uncom- 
bined bodies do not travel , 544, 546. 

, circular series of effects, 502, 962. 

, simultaneous, 1150. 

, definite, 329, 372, 377, 504, 704, 714, 

722, 726, 732, 764, 783, 807, 821, 960. 

> independent of variations of 

electrodes, 714, 722, 807, 832. 

necessary intensity of current, 911, 

966, 1345, 1354. 

, influence of water in, 472. 

, in air, 454, 461, 469. 

■ , some general conditions of, 669. 

, new conditions of, 453. 

, primary results, 742. 

, secondary results, 702, 742, 748, 777. 

, of acetates, 774. 

, acetic acid, 773. 

, ammonia, 748. 

— — , chloride of antimony, 690, 796. 

f lead, 794, 815. 

f silver, 541, 813, 979. 

, chlorides in solution, 766. 

, fusion 789, 813. 

, fused electrolytes, 789. 

; , hydriodio acid and iodides, 767, 787. 

, hydrocyanic acid and cyanides, 771. 

, hydrofluoric acid and fluorides, 770. 

, iodide of lead, 802, 818. 

( potassium, 805. 

- — , muriatic acid, 758, 786. 

, nitre, 753. 

, nitric acid, 752. 

, oxide of antimony, 801. 

f dead, 797. 

protochloride of tin, 789, 819. 

protiodide of tin, 804. 

— — , sugar, gum, &c., 776. 

, of sulphate of magnesia, 495. 

, sulphuric dcid, 757. 

", sulphurous acid, 755. 

, tartaric acid, 775. 

, water, 704, 785, 807. 

, theory of 477, 1345. 

, , by A. de la Kive, 489, 507, 

514, 543. 

, — . Biot, 486. 

, Davy, 482, 500. 1 

: Grotthuss, 481, 493, 515. 

, , Hachette, 491, 513. 

, Biffault and Chompr6, 485, 

507, 612. 

— author’s theory, 518, 524, 1345, 1623, 
1703, 1706. 

Definite decomposing action of electricity, 

329, 872, 377, 504, 704, 788, 821. 

— — magnetic action of electricity, 216, 
362, 367, 377. 

-r electro-chemical action , 822, 869, 960. 

- — , — — , general principles of, 822, 862. 
— — — , in chloride o/lead, 815. 


Definite electro-chemical action in chloride 
of silver, 813. 

, in hydriodic acid, 767, 787? 

, iodide of lead, 802, 818. 

, muriatic acid, 758. 786. 

protochloride of tin, 819. 

, water, 732, 785, 807. 

Degree in measuring electricity, proposal 
for * 736. 

Dc la Rive on heat at the electrodes, 1037. 
, his theory of electro-chemical de- 
composition, 489, 507, 514, 543. 
Dielectrics, what, 1168. 

, their importance in electrical jk- 

tions, 1660. T 

, their relation to static induction , 1 290. 

, their condition under induction, 

1369, 1679. 

, their nature, affects the brush, 1455. 

, their specific electric actions, 1296, 

1398, 1423, 1454, 1503, 1.560. 

Difference of positive and negative dis- 
charge, 1465, 1480, 1485. 

Differential inductometer, 1307. 

Direction of ions in the circuit, 962. 

■ the electric current, 003. 

the magnclo-olectrie current, 114, 

no. 

the induced volta-electric current, 
19,26,1091. 

Disruptive discharge, 1359,1405. See Dia- . 
charge, disruptive. 

Discharge, electric, as balls of fire, It >41. 

, of Leyden jar, 1300. 

, of voltaic battery try hot air, 271, 274. 

-points, 272. 

, velocity of, in metal, varied, 1333. 

, varieties of, 1319. 

, brush, 1425. See Brush. 

carrying, 1562. See Discharge, con- 
vective. 

, conductive, 1320. See Conduction. 

, dark, 1444, 1544. 

, disruptive, 1359, 1405. 

, electrolytic, 1343, 1622, 1704. 

, glow, 1526. See Glow. 

, positive and negative, 1465. 

, spark, 1406. See Spark, electric. 

Discharge, convective, 1442, 1562, 1601, 
1623, 1633, 1642. 

, in insulating media, 1562, 1572. 

, in good conductors, 1603. 

, U'itn fin id terminations in air, 1581, 

1589. 

• liquids, 1597. 

■, from a nail, 1576, 1590, 

, influence of points in, 1573. 

, affected by mechanical causes, 1579. 

, — — flame, 1580. 

, with glow, 1576. 

, charge of a particle in air, 1564. 



INDEX. 


563 


Discharge, convective \ in oil of turpentine, 
1570. • 

-• — charge of air by, 1442, 1592. 

, currents produced in air, 1572. 1581, 

1591. 

in. oil of turpentine, 1595, 1598. 

, direction of the currents, 1599, 1045. 

, Porrett’s effects, 1548. 

, positive and negative, 1593, 1800, 

1643. 

Discharge, convective, related to electro- 
lytic discharge, 1622, 1633. 

Discharge , dark, 1444, 1544, 1560. 
with negative glow, ] 544. 

, between positive and negative glow, 
1547. 

, in air, 1548. 

, muriatic acid gas, 1554. 

, coal gas, 1556. 

, hydrogen, 1558. 

, nitrogen, 1559. 

Discharge, disruptive, 1405. 

, preceded by induction, 1362. 

, determined bv one particle. 1370, j 
1409. 

, necessary intensity, 1409, 1553. j 

", dctenmmngiutensitycon.stant,l410. ! 

— — f related to particular dielectric, 1503. j 

, facilitates like action, 1417. 1435, j 

1453, 1553. 

, its time, 1418, 1436, 1498, 1611. 

, varied hu form of conductors, 1302, 

1372, 1374.' 

— , change in the dielectric, 1395. 

1422, 1454. 

■ rarefaction of air, 1365, 1375, 

1451. 

temperature, 1367, 1380. 

distance of conductors, 1303, 

1304, 1371. 

size of conductors, 1372, 

, in liquids and solids, 1403. 

, in different gases, 1381, 1388, 1421. 
not alfke, 1395. 

f } specific differences, 1399, 1422, 

' 1087 - 

, positive and negative , 1393, 1399, 

1465, 1524. 

, distinctions, 1467, 1475, 1482. 

, differences, 1485, 1501. 

, , relative facility, 1496, 1520. 

, dependent on the dielectric, 

1503. 

, , in different gases, 1506, 1510, 

1518, 1687. 

, , 8f voltaic current, 1524. 

, brush, 1425. 

collateral, 1412. 

, dark, 1444, 1544, 1560. 

, glow, 1526. 

■, spark, 1406, 


Discharge, theory of, 1368, 1406, 1434. 
Discharge, electrolytic, 1164, 1343, 1621. 
1703, 1700. 

, previous induction, 1345, 1351. 

, necessary intensity, 912, 966, 1346, 

1354. 

, division of the electrolyte, 1347, 

1704. 

, stopped by solidifying the electro- 
lyte, .380, 1358, 1705. 

— , facilitated by added bodies, 

1355. 

, in curved lines, 521, 1216, 1351. 
proves act ion of contiguous jmr tides, 

positive and negative, 1525. 

, velocity of electric current in, 1650. 

— — , related to convective discharge, 1622. 
- — , theory of, 1344, 1622, 1704. 
Discharging train generally used, 292, 
Disruptive discharge, 1405. Set * Discharge, 
disruptive. 

Dissimulated electricity. 1684. 

Distance . its influence, in induction, 1303, 
136 U 371. 

— over disruptive discharge, 1.364, 1371. 
Distant chemical actions, ot unoeted and 
opposed, 891, 909. 

Distinction of magnetic and magnetoodee- 
Iric action, J38, 215, 243, 253. 

Division of a. charge by inductive appa- 
ratus, 1208. 

Ddbcrciner on combination effected by 
platina, 609, 010. 

Dulong a:*d Thenard on combination by 
platina ami solids, 609, 611. 

Dust, charge of its particles, 1507. 

# 

Earth, natural magneto-electric induction 
in, 181, 199,192. 

Elasticity 0 / gases, 626, 

gaseous particles, 658. 

Electric brush, 1425. See. Brush, electric. 

condition of particles of matter, 802, 

1669. 

- conduction, 1320. See Conduction. 

current defined, 283, 51 1. 

# nature of, 511, 1617, 1627. 

. free. Current, electric. 

— — , induction of, 6, 232, 241, 1048, 

1101. Induction of electric current. 

, induction of, on itself, 1048. 

r discharge, 1319* See Discharge. 

force, nature of, 1667. See Forces. 

induction, 1162. See Induction. 

inductive capacity, 1252. See Spe- 
cific inductive capacity. 

polarity, 1685, See Polarity, electric. 

spark, 1406. See Spark, electric. 

and magnetic forces, their relation, 

118, 1411, 1653, 1668, 1709, 1731. 

2 o 2 



664 


INDEX. 


Electric*, charge of, 1171, 1247. 

Electrical excitation, 1737* Excitation. 

machine generally used, 290. 

battery generally used, 291. 

and chemical forces identical, 877, 

917, 947, 960, 965, 1031. 

Electricities, their identity, however ex- 
cited, 265, 360. 

, one or two, 516, 1667. 

, two, 1 163. 

-, their independent existence, 

1168. 

, their inseparability, 1168, 1177, 

1244. 

, — , never separated in the current, 

1628. 

Electricity , quantity of, in matter, 852,801. 

, its distribution on conductors, 1368. 

1 influenced by form, 1302, 1374 

distance, 1303, 1364, 1371. 

, air’s pressure, 1375. 

, relation of a vacuum to, 1613. 

, dissimulated, 1684. 

, common and voltaic, measured, 361, 

860. 

, its definite decomposing action, 329, 

377, 783, 1621, 

1 heating action, 1625. 

, magnetic action, 216, 366. 

, animal, its characters, 351. 

, magneto-, its characters, 343. 

, ordinary, its characters, 284. 

, thermo-, its characters, 349. 

, voltaic, its characters, 268. 

Electricity from magnetism, 27, 36, 57, 83, 
185, 140. 

, on magnetisation of soft iron by cur- 
rents, 27, ‘34, 57, 113. 

magnets, 36, 44. 

, employing permanent magnets, 39, 

84, 112. 

■ terrestrial magnetic force, 140, 
150, 101. 

moving conductors, 55, 83, 132, 
109,149,161,171. 

• , essential condition, 217. 

byjrevolving plate, 83, 149, 240. 

% constant source of electricity, 

8,9, 90, 164. * 

1 jaw of evolution, 1 14. 

t direction of the current evolved, 

91,99,110,116,117. 

, course of the currents in the 

plate, 123, 150. 

by a revolving globe, 137, 160. 

by plates, 94, 101. 

by a wire, 49, 05, 109, 112, 137. 

, conductors and magnet may move 

together, 218. 

, current produced in a single wire, 

49,65,170. 


Electricity from magnetism a ready source 
' of electricity, 46, note . 

, — — momentary, 28, 30, 47. 

, permanent, 89, 154. 

» deflects galvanometer, 30, 39.46, 

, makes magnets, 34. 

, shock of, 56. 

> spark of, 32. 

f traverses 'fluids, 23, 33. 

, current produced, its direction, 30, 
38, 41, 52, 53, 54, 78, 91, 99, 114, 142, 
166, 220, 222. 

, effect of approximation and reces- 

cion, 18, 39, 50. 

, the essential condition, 217. 

, general expression of the effects, 256. 

- from magnets alone, 220. 

Electricity of the voltaic pile, 875. 

its source, 875. 

not metallic* contact, 887, 915. 
, is in chemical action, 879, 916, 

919, 1738, 1741. 

Electro-chemical decomposition , 450, 661. 

, nomenclature, 661. 

general conditions of, 669. 

, new conditions of, 453. 

, influence of water in, 472. 

, primary and secondary results, 742. 

, definite, 732, 783. 

, theory of, 477. 

. See also Decomposition, electro- 
chemical. 

Electro-chemical equivalents , 824, 833, 835, 
855. 

, table of, 847. 

liow ascertained, 837. 

always consistent, 835. 

sain e as ch era ieal e q ui va Ion t s, 836, 839. 

able to determine atomic number, 861 . 

ElecVro-chem i cal exei tation, 878, 919, 1738. 
Electrode defined, 662. 

Electrodes affected by beat, 1637. 

", varied in size, 714, 722. 

t nature, 807. 

. See Poles. 

Electrolysis, resistance to, 1007. 
Electrolyte defined, 664. 

exciting, solution of acid, 881, 925. 

alkali, 931, 941. • 

exciting , water, 944, 945. 

sulphuretted solution, 943. 

Electrolytes, their necessary constitution, 
669, 823, 829, 858, 921, 1347, 1708. 

consist of single proportionals of ele- 
ment*, 679, 697, 830, 1707. 

essential to voltaic pile, 021. 

w hy, 858, 923. 

conduct and decompose simulta- 
neously, 413. 

can conduct feeble currents without 

decomposition, 967. 



INDEX. 


565 


Electrolytes, as ordinary conductors, 970,. ; 

# <983, 1344. j 

, solid, their insulating and conduct- j 

mg power, 419. 

— real conductive power not affected 
by dissolved matters, 1356, 

, needful conducting power, 1158. 

are good conductors when fluid, 394, 

823. » 

non-cortd actors when solid, 381, 394. 

, why, 910, 1705. 

, the exception, 1032. 

, their particles polarize as wholes, 

1700. 

, polarized light sent across, 951. 

, relation of their moving elements to 

the passing current, 923, 1704. 

their resistance to decomposition, 
891,1007,1705. 

- and metal, their states in the voltaic 
pile, 940. 

, salts considered as, 098. * 

, acids not of tins class, 081. 
Electrolytic action of the current, 478, 
518, 1020. 

conductors. 474. 

— discharge, 1343. See Discharge, elec- 
trolytic. 

• induction, 1104, 1343. 

intensity, ‘,111, 9(U>, 983. 

varies for different bodies, 912, 

980, 1354. 

of chloride of lead, 978. 

chloride of wilier, 979. 

sulphate of soda, 975. 

water, 908, 981. 

its natural relation, 987 J. 

Electrolyzation, 450,001, 1 104, 13 17, J704. 

See Decomposition electro-chemical. 

defined, 004. 

facilitated, 394, 417, 549, 1355. 

in a single circuit, 803, 879. 

, intensity npcdful for, 919, 906. 

of chloride of silver, 541, 979. 

sulphate of magnesia, 495. 

and conduction associated, 413, 070. 
Electro-magnet, inductive effects in, 1060. 
Electro-magnetic induction definite, 216, 
366. 

Electrometer , Coulomb's , described, 1 180. 

* , how used, 1183, 

Electro-tonic state, 00, 231, 242, 1114, 
1661, 1729. 

* considered common to all metals, 66. 

conductors, 76. 

■ is a stftte of tension, 71. 

— is dependent on particles, 73. 
Elementary bodies probably ions, 849. 
Elements evolved by force of the current, 
493, 5&, 524. 

at the poles, why, 535. 


Elements determined to either pole, 652, 
681,757. 

, transference of, 454, 533. 

, if not combined, do not travel, 544, 

546. 

Equivalents, electro-chemical, 824X13,855. 

. chemical ami electro-chemical, the 

same, 836. 839. 

Ether, interference of, 651. 

Evolution of electricity, 1 162, 1737. 

of one electric force impossible, 1175. 

of elements tit the poles, why, 535. 

Excitation, electrical, 1 737. 

by chemical action, 878, 916, 1739. 

by friction, 1744. 

Exclusive induction, 1681. 

El a mo favours convective discharge, 1580. 
Elowing water, electric currents in. IVH). 
j Fluid terminations for convection, 1581. 

I Fluids, their adhesion to metals, 10,38. 

' Eluoride of lead, hot, conducts well, 1340. 
Force, chemical, local, 947, 969, 1739. 

circulating, 917, 947, 996, 1 120. 
Force, cWtno, nature of, 1163, J607. 

, imhutiio, of currents, its nature, 

60, 1113, 1735. 

Forces, electric, two, 1163. 

, inseparable, 1163, 1177, 1244, 1627. 

j — and chemical, arc t he same, 877, 916. 

j - and mat pu.de, relation of, 141 1, 1663, 

! 1658, 17<»9. 

, aro they essentially different? 
1663,1731. 

Forces, ettciliiu/, of voltaic apjfura/us, 887, 

916. 

. exalted, 905, 994, 1138, 1148. 

* Forces, polar, 1665. 

— <>J the turrt at, <h reel, 1620. 

— — , lateral or transverse, 1633, 
170S>. 

Fonn, its influence on induction,!. ‘102,1374. 

discharge, 1372, 1374. 

Fox, hw terrestrial electric currents, 187. 
Friction electricity, its characters, 284. 

, excitement by, 1744. 

Fusion, conduction consequent upon, 394, 
402. • 

Fusmieri, on combination effected by pla- 
tina, 613, 

Galvanometer, affected by common elec- 
tricity, 289, 366. 

, a correct measure of electricity, 367, 

note. 

Gases , their elasticity, 626, 657. 

, conducting power, 1336. 

, insulating power, 1381 , 1507. 

t not alike, 1395, 1608. 

, specific inductive capacity, 1283, 

1290, 



566 


INDEX. 


Gases, specific inductive capacity alike in 
all, 1292. 

, specific influence on brush and 

spark, 1463, 1687. 

Gases, discharge, disruptive, through, 138 1 . 

, brush in, 1464. 

, spark in, 1421. 

positive and negative brushes in, 1475. 

their differences, 1476. 

, positive and negative discharge in, 

1393,1506,1687. 

, solubility of, in cases of electrolyza- 
tion, 7l7, 728. 

from water, spontaneous recombina- 

nation of, 566. 

, mixtures of, affected bv platina 

plates, 571. 

, mixed, relation of their particles, 625. 

General principles of definite electrolytic 
action, 822. 

remarks on voltaic batteries, 1034, 
1136. 

- results as to conduction, 443. 

- induction, 1295. 

Glass, its conducting power, 1239. 

, its specific inductive capacity, 1271. 

, its attraction for air, G22. 

, water, 1254. 

Globe, revolving, of Barlow , effects ex- 
plained, 137, 160. 

is magnetic, 164. 

Glow, 1405, 1526. 

, produced, 3527. 

, positive, 1527. 

, negative, 1530. * 

, favoured by rarefaction of air, 1529. 

, is a continuous charge of air, 1526, 

1537, 1543. 

, occurs in all gases, 1534. 

- — — accompanied by a wind, 1535. 

, its nature, 1543. 

, discharge, 1526. 

, brush and spark relation of, 1533, 

1538, 1539. 1541 

Grotthuss’ theory of electro-chemical de- 
composition, 481, 499, 515. 

Growths'/ d brush, 1437. 

spark, 1553. 

Haohette’s view of electro-chemical de- 
composition, 491. 

Hare’s voltaic trough, 1123, 1132. 

Harris on induction in air, 1363. 

Heat affects the two electrodes, 1637. 

increases the conducting power of 

some bodies, 432, 438, 1340. 

— , its conduction related to that of elec- 

tricity, 416. 

' , as a result of the electric current, 

853, note, 1625, 1630. 

evolved by animal electricity, 353. 


Heat evolved by common electricity, 287. 

— magneto-electricity, 344. 

thermo-electricity, 349. 

voltaic electricity, 276. 

nelix, inductive effects in, 1061, 1094. 
Hydriodic acid, its electrolyses, 767, 787. 
Hydrocyanic acid, its electrolyses, 771,788. 
Hydrofluoric acid, notelectrolysable, 770. 
Hydwgen, brush in, 1459. 

, positive and negative brush in, 1476. 

, discharge in, 1514. 

Hydrogen and oxayen combined by platina 
plates, 570, 605. 

spongy platina, 609. 

Ice, its conducting power, 419. 

a non-conductor of voltaic current", 

381. 

Iceland crystal, induction across, 1695. 
Identity of electricities, 265, 360, 

of chemical and electrical forces, 877, 

9WT, 947, 961, 1031. 

Ignition of wire by electric current, 853, 
note, 1630. 

Improved -voltaic battery, 1006, 1120. 
Increase of cells in voltaic battery, effect 
of, 990. 

Inducteous surfaces, 1483. 

Induction apparatus , 1187. 

, fixing the stem, 11 IX), 1193. 12(H). 

, precautions, 1194, 1199, 1213, 1232, 

1250. 

, removal of charge, 1203. 

, retention of charge, 1205, 1207. 

, a charge divided, 1208. 

, peculiar effects with, 1233. 

Induction, static, 1161. 

-, an action of contiguous particles 

1J65, 1231, 1253, 1295, 1450, 1668, 1679. 

, consists in a polarity of particles, 

1298, 1670, 1679. 

, continues only in insulators, 1298, 

1324, 1338. 

, intensity of, sustained, 1362. 

, influenced by the form of conductors. 
1302. 

- distance of conductors, 1303. 
, relation of the bounding sur- 
faces, 1483. 

, charge, a case of, 1171, 1177, 1300. 

, exclusive action, 1681. 

, towards space, 1614. 

, across a vacuum, 1614. 

through air, 1217, 1284. 

different gases, 1381, 1395. 

— crystals, 1689. f 

— lac, 1228, 1255, 1308. 

metals, 1329, 1332. 

all bodies, 1331, 1334. 

- — , its relation to other electrical actions, 
1165,1178. 



INDEX. 


Induction , static, its relation to insulation. 

# *1324, 1302, 1368, 1678. 

, conduction, 1320. 

, discharge, 1319, 1323, 1362. 

, electrolyzation, 1104, 1343. 

, intensity, 1178, 1302. 

, excitation, 1178, 1740. 

., disruptive discharge, 1302. 

, charge, 1177, 1299. * 

an essential general electric function, 

1178, 1299. 

, general results as to, 1295. 

theory of, 1165, 12 31, 1295. 1667, 
1009. 

■ in curved lines, 1100, 1215, 1079. 

■ , through air, 1218, 1449. 

, _ — _ other gases. 1220. 

■ lac. 1228. 

— sulphur, 1228. 

oil of turpentine, 1227. 

Induction, specific, J 107, 1252, 1307. 

. the problem stated, 1252. * 

solved, 1307. 

of air, 1284. 

, im uriablo, .1287, 1288. 

, of gases, 1283, 1290. 

, — — alike in all, 1292. 

, of shelMae, 1250, 1209. 

, glass, 1271. 

, sulphur, 1275. 

, spermaceti, 1279. 

•, certain. fluid insulators, 1280. 
Induction of electric currents, 0, 34. 232, 
241, 1048, 1089, 1101, 1000, 1718. 

, on causing the principal current, 10, 

238,1101. ; 

— . on slopping the principal current, 
10, 17, 238, 1087, 1 100. 

by approximation, 18. 231. 

— by increasing distance, 19, 237. 
effective through conductors, 17 J 9, 

1721, 1735. 

insulators, 1719, 1722, 1735. 

in different metals, 193, 202, 21 i, 

2i3. 

— in the moving earth, 181. 

- in flowing water, 190. 

in revolving plates, 85, 240. 

, the induced current , its direction, 20, 
232 

, duration, 19, 47, 89. 

— — , , traverses fluids, 20, 23. 

, — — , its intehsity in different con- 
ductors, 183, 193, 20i, 211, 213. 

— 1 not obtained by Leyden dis- 

charge, 24. 

* , Ampere’s results, 78, 255, 379, note. 

Induction of a current on itself, 1048, 1 109. 

• , apparatus used, 1062. 

*— — in a long wire, 1064, 1Q68, 1092,1 1 18. 
— — , f doubled wire, 1090. 


567 

Induction of a current on itself, in a helix, 
1053, 1061. 

in doubled helices, 101)0. 

in an electro magnet, 1056, 1000. 

, wire and helix compared, 1065. 

, short wire, effects with, 1007. 

- — , action momentary, 1070, 1091, 1100. 

, causes no permanent change iu the 

current, 1071. 

- not due to momentum, 1077, 

— , induced current separated, 1078, 
1089. 

, effect at breaking contact , 1 000, 108 1 , 

1084, 1087. 

, making contact, 1101, 1100. 

* effets produced, shock, 1000, 1001, 

1079. 

, -- spark, 1060, 1004, 1080. 

, chemical decomposition, 1084. 

, , ignition of win', 1081, 1 104. 

j , cause is in i he conductor, 1059, 1070. 

I , general prmciplvsof the action, 1093, 

I J, ° 7 -. 

, direction of the forces lateral, 1108. 
Induction . magnetic, 255, 1058, 1710, 

. b> intermediate particles, 1003,17 10, 
1729,1735. 

, through ijuiescent bodies, 1712,1719, 

1720, 1735. 

j , moving bodies, 1715,1710,1719. 

j and magneto-electric, distinguished, 

; 138, 2J5, 243, 253. 

Induction, magneto-electric, 27, 58, 8J, 
HO, 193, 1709, See Amro’s magnetic 
phenomena. 

, rmtgnolcef ric, 58. 

- - - , electrolytic, 1104, 1345, 1702, 1740. 

, volfa-electric, 20. 

Inductive capacity, specific, 1107, 1252. 
Induct ice force of currents lateral. 20, 1 108. 

- , its nature, 1113, 1000, 1003, 1709. 

Inductive force, lines of, 1231. 1297, 1304. 

, often curved, 1219, 1224, 1230. 

f exhibited by the brush, 1449. 

their lateral relation, 1231, 1297 > 
1304. 

, their relation to ratign’Ktwjm, 1411. 

1 668, 709. 

Induotomeler, differential, 1307, 1317. 
Induclric surfaces, 1483. 

Inexhaustible nature of the electric cur- 
rent, 1031. 

Inseparability of the two electric forces, 
1103, 11774244, 1028. 

Insulating power of different gases, 1388, 
1395, 1607. 

Insulation , 1320, 1359, 1301. 

, its nature, 1321. 

— — is sustained induction, 1324, 

, degree of induction sustained, 1362. 

dependent on the dielectrics, 1368. 



568 


INDEX. 


Insulation dependent on the distance in air, 
1303, 1334? 1371. 

density of air, 1365, 1375. 

' — induction, 1368. 

form of conductors, 1302, 1374. 

, as affected by temperature of air, 

1367, 1380. 

in different gases, 1381, 1388. 

differs, 1395. 

in liquids and solids, 1403. 

in metals, 1328, 1331, 1332. 

— — ■ and conduction not essentially dif- 
ferent, 1320, 1326, 1336, 1338, 1561. 

, its relation to induction, 1324, 1362, 

1368,1678. 

Insulators , liquid, good, 1172. 

, solid, good, 1254. 

, the best conduct, 1233, 1241, 1245, 

1247, 1254. 

tested as to conduction, 1255. 

and conductors, relation of, 1328, 

1334, 1338. 

Intensity , its influence in conduction, 419. 

, inductive, how represented, 1370. 

, relative, of magneto-electric cur- 
rents, 183, 193, 211, 213. 

of disrupti \ e discharge constant, 1410. 

, electrolytic, 912, 966, 983, 1354. 

necessary for electrolyzation, 91 1,966. 

of the current of single circles, 904. 

increased, 906. 

of electricity in the voltaic battery, 

990, 993. 

of voltaic current increased, 906, 990. 

Interference with combining power of pla- 
tina, 638, 655. 

by olefiant gas, 640. 

carbonic oxide, 645. 

sulphuret of carbon, 650. 

other, 651. 

Interpositions, their retarding effects, 1018. 
Iodides in solution, their electrolysis, 769. 

fusion, their electrolysis, 802, 813. 

Iodide of lead, electrolysed, 802, 818. 

of potassium, test of chemical action, 

316. 

Ions , what, 666, 824, 833, 834, 849. 

— — not transferable alone, 542, ,547, 826. 

, table of, 847. . 

Iron, both magnetic and magneto-electric 
at once, 138,264. 

» copper and sulphur circles, 943. 

Jenkin, his shook by one pair of plates, 1049, 

Kemp, his amalgam of zinc, 999. 

Knight, Dr. Go win, his magnet, 44. 

Lac, charge removed from, 1203. 

, induction through, 1255. 

— — , specific inductive capacity of. 1256, 
1269. 


, Lac, effects of its conducting power, 1234. 

, its relation to conduction and inSiir 

lation, 1324. * 

Lateral direction of induotive forces of 
currents, 26, 1 108. 

forces of the current, 1653, 1709. 

Law of conduction, new , 380, 394, 410. 

magneto-electric induction, 114. 

H-olla-electric induction, 20. 

Lead, chloride of, electrolysed, 794, 815. 

■, fluoride of, conducts well when 

heated, 1340. 

, iodide of, electrolysed, 802, 818. 

, oxide of, electrolysed, 797. 

Leyden jar, condition of its charge, 1682. 

, its charge, nature of, 1300. 

, its discharge, 1300. 

, its residual charge, 1249. 

Light, polarized, passed across electrolytes, 
951 

, electric , 1405, 1445, 1500, note . 

- ,* , spark, 1400, 1553. 

. f , brush, 1425, 1444, 1445. 

a 1 glow, 1526. 

Lightning, 1420, 1464, 1641. 

Lines of inductive force, 1231, 1304. 

often curved, 1219, 1224, 1230, 

, as shown by the brush, 1449. 

, their lateral relation, 1231, 1297, 

1304. 

— , their relation to magnetism, 1411, 
1658, 1709. 

Liquefaction, conduction consequent upon, 
380, 394, 410. 

Liquid bodies which are non-conductors, 
405. 

Local chemical affinity, 947, 959, 961, 1739, 

Machine, electric, evolution of electricity 
by, 1748. 

, magneto-electric, 135, 154, 158, 1118. 

Magnelectric induction, 58. 

, collectors or. conductors, 80. 

Magnesia , sulphate, decomposed against 
water, 494, 533. 

, transference of, 495. 

Magnet, a measure of conducting power, 
216. 

and current., their relation remem- 
bered, 38, 'note. 

— plate revolved together, 218. 

cylinder revolved together, 219. 

- — — revolved alone, 220, 223. 

and moving conductors, their general 

relation, 256. 

made by induced current, 13, 14. 

, electricity from, 36, 220, 223. 

Magnetic bodies, but few, 255. 

, curves, their induotive relation, 217, 

232. 

effects of voltaic electricity, 277. 



INDEX. 


669 


Magnetic effects of common electricity, 
£88, 367. * 

• raagneto-electrioity, 27,83,345. 

thermo-electricity, 349. 

animal electricity, 334. 

and electrical forces, their relation, 

118, 1411, 1653, 1658, 1709. 1731. 

forces active through intermediate j 

particles, 1663, 1710, 1729, 1735./ 

forces of the current, 1653 

very constant, 1054. 

deflection by common electricity, 289, 

296. 

phenomena of Arngo explained, 81. 

induction. See Induction, magnetic. 

induction through quiescent bodies, 

1712, 1719, 1720, 1735. 

moving bodies, 1715, 1719. 

and magneto-electric action distin- 
guished, 138, 215, 243, 253. 

Magnetism , electricity evolved by, 27. 

— its relation to the lines of inductive 
force, 1411, 1658, 1709. 

... bodies classed in relntion to, 255. 

Magneto-electric currents, their intensity, 
1*83,193,211,213. 

— , their direction, 114, 116. 

transverso fluids, 33. 

momentary, 30. 

permanent, 89. 

in all conductors, 193, 213. 

Magneto-electric induction, 27, 58. 

1 terrestrial, 140, 181. 

1 law of, 1 14. 

, See Arngo’s magnetic phenomena. 

Magneto-electric machines, 135, 154, 158. 
— 1 inductive effects in their wires, 1118. 
Magneto-electricity, its general characters 
considered, 343, Ac. 

identical with other electricities, 360. 

, its tension, 343. 

, evolution of heat, 314. 

, magnetic force, 345. 

, chemical force, 346. 

, spark, 348, ^ 

, physiological effects, 347. 

. See Induction, magnetic. 

Matter , atoms of, 869, 1703. 

, now condition of, 60, 231; 242, 11 14. 


1661, 1729. 
— , quantity 


of electricity in, 852, 861, 


873, 1652. 

, absolute charge of, 1169. 

Measures of electricity , galvanometer, 367, 


rlvlo. 

, voltifcmeter, 704, 730, 739, 

metal precipitated, 740, 842. 

Measure of specific inductive capacity, 
1307,1690. , , . , 

Measurement of common and voltaic elec- 
tricities, 361, 860, 1652. 


Measurement of electricity , degree, 730,738. 

— — by voltameter, 704, 736, 739. 

by galvanometer, 367, note. 

by metal precipitated, 740, 842. 

Mechanical forces affect chemical affinity, 
656. 

Mercurial terminations for convection, 
1581. 

Mercury , poriodide of. an exception to the 
law of conduction ? 691, 1341. 

, perch loride of, 692, 1341. 

Metallic contact not necessary for electro- 
lyzation, 879. 

: not essential to the voltaic current, 

879, 887, 915. 

its use in fhe pilo, 893. 896. 

Metallic poles, 557. 

Metal and electrolyte, (heir state, 946, 
Metals, adhc.-iou of fluids to, 1038. 

, their /mrer of inducing combina tion, 

564, 608. * 

, interfered with, 638, 

- , static induction in, 1329, 1332. 

- , different, currents induced in, 193, 

211. 

, generally secondary results of elec- 
trolysis., 746. 

— transfer chemical force, 918. 

- , transference of, 539, 545. 

insulate in a certain degree, 1328. 

, eonveetivo currents in, 1603. 

, but few magnetic, 255. 

Model of relation of magnetism and elec- 
trieity, 1 16. 

Molecular inductive action, M64, 1669. 
Motion csBontinl to mngneto-oleetrio in- 
duction, 39, 217, 256. 

across magnetic curves, 217. 

of conductor and magnet , relative , 

114. 

- not necessary, 218. 

Moving magnet i» electric, 220. 

Muriatic acid gas, its high insulating 

power, 1395. 

, brush in, 1462. 

, dark discharge in, 3554. 

, glow in, 1534. 

, positive and negative bflfsb in, 1476. 

, spark in, 1422, 1463. 

lias no dark interval, 1463, 

1565. 

Muriatic acid decomposed by common 
electricity, 314. 

, its electrolysis, (primary), 758, 786. 

Nascent state, its relation to combination, 
658,717. 

Natural standard of direction for current, 
663. 

— - relation of electrolytic intensity, 987$. 
Nature of the electric current, 1617. 



570 


JNDEX. 


Nature of the electric force or forces, 1667. 
Negative current, none, 1627, 1632. 

discharge, 1465, 1484. 

as spark, 1467, 1482. 

, as brush, 1466, 1502. 

spark or brush, 1484, 1502. 

and positive discharge , 1465, 1482, 

1525. 

in different gases, 1393. 

New electrical condition of matter, 60, 231 , 
242,1114,1661,1729. 

law of conduction, 380, 394, 410. 

Nitric acid formed by spark in air, 324. 

favours excitation of current, 906, 

1138. 

transmission of current, 1020. 

is best for excitation of battery, 1137- 

, nature of its electrolysis, 752. 

Nitrogen determined to either pole, 554, 
74$, 752. 

— — a secondary result of electrolysis, 746, 
748. 

, brush in, 1458. 

, dark disclmrgo in, 1559. 

, glow in, 1534. 

, spark in, 1422, 1463. 

, positive and negative brush in, 1476. 

, discharge in, 1512. 

, its influence on lightning, 1464. 

Nomenclature, 662, 1483. 

Nonoonducrtion by solid electrolytes, 381, 
1.358, 1705. 

Note on electrical excitation, 1737. 

Nuclei, their action, G23, 657. 

• • 

Olefiant gas, interference of, 640, 652. 
Ordinary electricity , its tension, 285. 

evolution of heat, 287. * 

magnetic force, 288, 362. 

chemical force , 309, 454. 

precautions, 322. 

spark, 333. 

physiological effect, 332. 

general characters considered, 284. 

■ , identity with other electricities, 

360. 

Origin of J;he force of the voltaio pile, 878, 

. 916,919. 

Oxidation the origin of the electrio ourrent, 
in the voltaio pile, 919, 930, 

Oxide of lead electrolysed, 797» 

Oxygen , brush in, 1457. 

, positive and negative brush in, 1476. 

, discharge in, 1513. 

— — solubility of, in cases of electrolyza- 
tion, 717, 728. 

, spark in, 1422. 

and hydrogen combined by platina 

plates, 570, 606, 630. 

*— spong y platina, 609, 636. 

* — — other metals, 008. 


Particles, their nascent state, 658. 

in air, how charged, 1564. * 

, neighbouring, their relation to eaefi 

other, 619, 624, 657. 

, contiguous, active in induction, 11 65, 

1677. 

of a dielectric, their inductive condi- 
tion, 1369, 1410, 1669. 

^polarity of, when under induction 

1298, 1676. 

, how polarised., 1669, 1679. 

, , in any direction, 1689. 

, , as wholes or elements, 1699. 

, , in electrolytes, 1702. 

, crystalline, 1689. 

, contiguous, active in electrolysis 

1349. 1702. 

their action in electrolyzation, 520. 

1343. 1703. 

, -local chemical action, 901, 

1739. 

- relation to electric action, 73. 

, - electric action, 1609, 1079, 

1740. 

Path of the electric spark, 1407. 
Phosphoric acid not an electrolyte, 682. 
Physiological effects of voltaic electricity, 
279. 

common electricity, 332. 

magneto-electricity, 56, 347. 

thermo-electricity, 349, 

animal electricity, 357. 

Pile , voltaic, electricity of, 875. 

. See Battery, voltaic. 

Plates of platina effect combination, 568, 
571, 590, 630. 

prepared by electricity, 570, 585, 588, 

friction, 591. 

r - heat, 595. 

chemical cleansing, 599, 605. 

, clean, their general properties, 033, 

717. 

, their power preserved, 576. 

, in water, 580. 

, their power diminished by action, 

581. 

, exposure to air, 636. 

, their power affected by washing in 

water, 582. 

-, heat, 584, 597. 

— — presence of certain gases, 638, 

655. 

, their power, cause of, 590, 616, 630. 

theory of their action , Dobereiner’s, 
610. 

, Dulong and Then&ird’s, 611. 

— , , Fusinieri’s, 613. 

, author’s, 619, 626, 630, 656. 

Plates of voltaic battery fqul, 114$. 

, new and old, 1146. 

vicinity of, 1148. 



INDEX. 


571 


Plates of voltaic battery , immersion of, # 
. 1003, 1150. 

— — , number of, 089, 1151. 

, large or small, 1154. 

Platina , clean, its characters, 6.^3, 717. 

— — attracts matter from the air, 634. 

, spongy, its state, 637. 

clean, its power of effecting combi- 
nation t 564, 590, 605, 617, 030/ * 

* interfered with, 638. 

, its action retarded by olefiant gas, 

640,052. 

( , carbonic oxide, 645, 652. 

See Combination, Plates of platina, 
and Interference. 

— — poles, recombination effected by, 567, 
588. 

Plumbago poles for chlorides, 794. 
Poisson's theory of electric induct ion, 1305. 
Points, favour convective discharge. 1573, 

, 'fluid for convection, 158J. 

Jbdar forces, their character. 1605.* 

decomposition by common electri- 
city. 312, 321, 469. 

Polarity , meaning intended, 1304, 1685. 

particles under induction, 1298, 

1676. 

, electric , 1670, 1685. 

1 „ its direction. 1688, 1703. 

, its variat ion. It >87. 

( , its degree, 16S6. 

, , in crystals, It >89. 

? , in molecules or atoms, 1699. 

/ , in electrolytes, 1702. 

Polarized light across electrolytes. 951 . 
Poles, electric , their nature, 461 , 498, 556, 
662. 

appearance of evolved bodies at, ac- 
counted for, 335. 

one element to eil her? 552, 681 , 75/ . 
of air, 455, 461, 559. 

, of water, 494, 558. 

, of metal, *557. 

of platina, recombination effected 

by, 567, 588. 

of plumbago, 794. 

Poles, magnetic, distinguished, 44, note. 
Porrett/s peculiar effects, 1646. 

Positive current none, It >27, 1632. 

discharge, 1465, 1480. 

, as spark, 1467, 1482. 

, as brush, 1467, 1476. 

spark or brush, 1484, 1502. 

and negative, convective discharge, 
1600. 

. disruptive discharge , 1465,1482, 

1485,1525. 

in different gases, 1393. 

m — voltaic discharge, 1524. 

. — electrolytic discharge, 1525. 

Potassa, acetate, nature of its electrolysis, 

7#9. 


| Potassium, iodide of, electrolysed, 805. 
Power of voltaic batteries estimated, 1126. 
Powers, their state of tension in the pile, 
949. 

Practical results with the voltaic battery, 
1136. 

Pressure of air retains electricity, ex- 
plained, 1377, 1398. 

Primary elect roly tieal results, 742. 
Principles, general, of definite electrolytic 
net ion, 822. 

Pruportionnls in electrolytes, single, 679, 
697. 

j Quantity of electricity in matter, 852, 801, 
873, 1652. 

voltaic battery, 990. 

Rarefaction of air facilitates discharge, 
why, 1375. 

I Recombination, spontaneous, of gases 
j from water, 566. 

j Relation, by measure, of electricities, 361. 
of magnets and moving conductors, 
256. 

of magnetic induction to intervening 

bodies, 1002, 1728, 

of a current and magnet, to remem- 
ber, 38, note. 

— of electric mid magnetic forces, 118, 
1411. 1053, 1658, 1709, 1731. 

- of conductors and insulators, 1321, 

1320, 1334. 1338. 

of conduction and induction, 1320, 

1337.* 

j of huhiction ««/?disrupti vo discharge, 

! 1302 

| electrolyzation, 1104, 1343. 

— excitation, 1178, 1740, 

| — charge, 1171, 1 177, 1300. 

of insulation and induction, 1324, 

1 1302, 1368, 1678. 

1 , lateral, of lines of inductive force, 

. 1231, 1297, 1304. 

! of a vacuum to electricity, 1613. 

of spark, brush, and glow, 1533, 

1539, 1542. ^ 

o£ gases to positive andjnegative dis- 
charge, 1510. 

of neighbouring particles to each 

other, 619, 624. 

— — . of elements in decomposing electro- 
lytes, 923, 1702. 

exciting electrolytes, 921. 

of acids and bases voltaically, 927, 

933- 

Remarks on the active battery, 1034, 1136. 
Residual charge of a Leyden jar, 1249. 
Resistance to electrolysis, 891, 904, 911. 
1007. 

of an electrolyte to decomposition, 
1007. 



572 


INDEX. 


Results of electrolysis, primary or second- 
ary, 742,777. 

— J“«^ ract * ca *’ voltaic battery, 

, general, as to induction, J 295, 1069, 

Retention of electricity by pressure of the 
atmosphere explained, 1877, 1398. 
Revolving plate. See Arago's phenomena. 

globe , Barlow's , effect explained, 137, 

160, 109. 

, magnetic, 164. 

, direction of currents in, 161, 

166. 

RifFault’s and Chompr^’s theory of electro- 
chemical decomposition, 485, 507, 512. 
Rock crystal, induction across, 1092. 
Room, insulated and electrified, 1173. 
Rotation of the earth a cause of magneto- 
electric induction, 181. 

Salts considered as electrolytes, 098. 

Scale of electrolytio intensities, 912. 
Secondary electrolytical results , 702, 742, 
748,777. 

become measures of the electric cur- 
rent, 843. 

Sections of the current , 498, 1034. 

decomposing force alike in all, 501, 

1621. 

Sections of lines of inductive action , 1309. 

, amount of force constant, 1369. 

Shock, Btrong, with one voltaic pair, 1049. 
Silver, chforide of, its electrolyzation, 541, 
813, 902. 

, electi^lytic intensity for, 9JT9. 

Silver, sulphurot of, hot, conducts well, 
433. 

Simple voltaic circles, 875. 

, decomposition effected by, 897, 904, 

931. 

Single and many pairs of plates, relation 
of, 990, 

Single voltaic circuits, 876. 

without metallio contact., 879. 

with metallic contact, 893. 

their force exalted, 900. 

give strong shocks, 1049. 

a bright spark, 1050. t 

Solid electrolytes are non-conductors , 394, 
402, 1358. 

, why, 910, 1705. 

Solids, their power of inducing combina- 
tion, 564, 018. 

interfered with, 038. 

Solubility of gases in cases of electrolyza- 
tion, 717, 728. 

Source of electricity in the voltaic pile, 875. 

■ - is chemical action, 879, 916, 919, 1741 . 

Spark, 1800, 1406. 

Spark, electric y its conditions, 1360, 1406, 

166 a 

path, 1407. 


f Spark, electric, its light, 1553. 

insensible duration or time, 14381 f 

accompanying dark parts, 1547,1032. 

determination, 1370, 1409. 

is affected by the dielectrics, 1395, 

1421. * 

size of conductor, 1372. 

r form of conductor, 1302, 1374. 

-Rarefaction of air, 1375. 

, atmospheric or Lightning, 1404,1041. 

, negative, 1393, 1467,1482, 1484,1502. 

, positive, 1393,1448,1407,1482,1484, 

1502. 


, ragged, 1420, 1448. 

, when not straight, why, 1568. 

, variation in its length, 1381. 

, tendency to its repetition, 1392. 

, facilitates discharge, 1417, 1553. 

, passes into brush, 1448. 

, preceded by induction, L302. 

, forms nitric acid in air, 324. 

,«in gases, 1388, 1421. 

, in air, 1422. 

, in nitrogen, 1422, 1463. 

, in oxygen, 1422. 

, in hydrogen, 1422. 

, in carbonic acid, 1422, 1403. 

, in muriatic acid gas, 1422, 1403. 

, in coal-gas, 1422. 

, in liquids, 1424. 

, precautions, 958, 1074. 

, voltaic, without metallic contact, 

915, 950. 

from single voltaic pair. 1050.** 

-* — from common and \oltaie electricity 
assimilated, 334. 

, first mugneto-deetric, 82. 

• of voltaic electricity, 280. 

pf common electricity, 3, ‘13. 

of magneto-clectrieity, 348. 

of thermo-electricity, 349. 

of animal electricity, 358. 

, brush and glow related, 1533, 1539, 

1542. 

Sparks, their expected coalition, 1412. 
Specific induction. See Induction, specific. 
1252. 

Specific inductive capacity, 1252. 

, apparatus for, 1187. 

of lac, 1256, 1270, 1308. 

of sulphur, 1275, 1310. 

of air, 1284. 

of gases, 1283, 1290. 

of glass, 1271. 

Spermaceti, its conducting power, 1240, 
1323. 4 

, its relation to conduction and insu- 
lation, 1322. 

Standard of direction in the current, 663. 
State, electrotonic, 60, 231, 242, 1114, 
1661, 1729. 

Static induction. See Induction, static. 



INDEX. 


573 


Sturgeon, his form of AragoY experiment, 

^ 49. 

-• , use of amalgamated zinc by, 853, 

999. 

Sulphate of soda decomposed by common 
electricity, 317. 

, electrolytic intensity for, 975, 

Sulphur determined to either pole, 552, 
081, 757. S 

, its conducting power, 1241, 1245. 

; , its specific inductive capacity, 1275. 

, copper and iron, circle, 913. 

Sulphuret of carbon, interference of, 050. 

— silver, hot, conducts well, 433. 

Sulphuretted solution excites the pile, 943. 
Sulphuric acid , conduction by, 4(49, 081. 

, magneto-electric induction on, 200, 

213. 

in voltaic pile, its use, 925. 

not an electrolyte, 081. 

, its transference, 523. 

— — , its decomposition, 081, 757. , 
Sulphurous aeiu, its decomposition, 755. 
Su minor// q/’eonditions of conduction, 443. 
molecular inductive theory, 1009. 


Table of discharge in gases, 1388. 
electric effects, 300. 


electro-chemical equivalents. 847. 

— - electrolytes affected by fusion, 402. 
insulation in gases. 1388. 

- — ions, anions, and cathions, 817. 
Tartaric acid, nature of its electrolysis, 775. 
Tension, inductive, how represented, 1370. 
of voltaic electricity, 208. 

- of common electricity, 285. 

of thermo-electricity, 349. 

- --- of magneto-electricity, 343. 

of animal electricity, 352, 

of zinc and electrolyte in the vbltaic 

pile, 949. 

Terrestrial electric currents, 187. 
Terrestrial magneto-electric induction, 140. 

cause of atorors* borealis, 192. 

, electric, currents produced by, 141, 

, 150. 


, in helices alone, 148. 

, , with iron, 141, 140, 

1 f with a magnet, 147. 

, a single wire, 170. 

, a revolving plate, 149. 

, a revolving ball, 100. 

, the earth, 173. 

Teat between magnetic and magneto-elec- 
tric action, 215, 243. 

Theory o/^ombination of gases by dean 
platina, 019, 026, 030, 056. 

electro-chemical decomposition, 477, 

661, 1623, 1704. 

tb# voltaic apparatus, 875, 1741. 

— — static induction, 1165, 1231, 1295, 
1666, 1667. 


°/disruptive discharge, 1368, 1406, 

Arago’s phenomena, 120. 

Thermo-electricity, its general characters, 
349. 

— - identical with other electricities, 360. 

, its evolution of heat, 349. 

, magnetic force, 349. 

physiological effects, 319. 

, spark, 349. 

Time, 59, 08, 124. 1248, 1328, 1340, 1 118, 
1431, 1430, 1498, 1012, 1041 1730. 

Tin, iodide of, electrolyzed, 801. 

■•, protochloride, electrolysis of, defi- 
nite. 789, 819. 

Torpedo, nature of its electric discharge, 
359. 

, its enormous amount of electric 

force, 359. 

Transfer of elements and the current, their 
relation, 923, 902. 

Transference is simultaneous in opposite 
directions. 512, 828. 

, unemubined bodies do not travel, 

544, 540. 820. 

of elements, 454. 507, 539. 550, 820. 

across great interval*, 455,408. 

, its nature, 519, 525, 5,‘i8, 549. 

- of chemical force, 918, 

Transverse forces of l hecummt. 1053, 1709. 
Travelling of charged particles, 1503. 
Trough, voltaic. See Battery, voltaic. 
Turpi ntinc, oil of a good fluid insulator, 
1,172. 

- , itajnsulating power destroyed, 1571. 

, charged, 1 172. 

, brush in, 1452. 

, electric motion* in, 1588, 1595, 

• , convective currents in, 1595, 1598. 

Uni polarity, 1635. 

Vacuum, its relation to electricity, 1613. 
Vaporization, 057. 

Velocity of conduction in metals varied, 
13.‘13. 

[ the electric discharge, 1041, 1049. 

conductive and electrolytic discharge, 

differlftico of, 1650. 

Vicinity of plates in voltaic battery, 1148. 
Volta-electric induction, 20. 
Voltaslectromefer, 704* 736. 

, fluid decomposed in it, water, 700, 

728, 732. 

, forms of, 707, 734. 

tested for variation of electrodes, 7 14, 

722. 

fluid within, 727. 

intensity, 723. 

, strength of acid used in, 728, 733. 

, its indications by oxygen and hydro- 
gen, 736. 



574 


INDEX. 


Volta-electrometer, its indications by hy- 
drogen, 734. 

} oxygen, 735. 

, how used, 737. 

Voltameter, 704. 

Voltaic battery , its nature, 875, 989. 

, remarks on, 1034, 1130. 

improved, 1001, 1119. 

— — , practical results with, 1136. 

. See Battery, voltaic. 

Voltaic circles , simple, 875. 

, decomposition by, 897. 

Voltaic circles associated, or battery, 989. 
Voltaic circuit , relation of bodies in, 962, 

, defined, 282, 611. 

, origin of, 916, 1741. 

, its direction, 663, 925. 

, intensity increased, 905, 990. 

, produced by oxidation of zinc, 919, 

930. 

not due to combination of oxide and 

acid, 925, 933. 

, its relation to the combining oxygen, 

921,962. 

, combining sulphur, 943. 

, the transferred elements, 923, 

902. 

, relation of bodies in, 962. 

Voltaic current, 1617. -See Current, eloctric. 
Voltaic discharge, positive and negative, 
1524. 

Voltaic decomposition, 450, 660. See De- 
composition, electro- chemical. 

Voltaio electricity , identical with electri- 
city, otherwise evolved, 268, 3jp0. 

, discharged by points, 272. 

_ hot air, 271, 274. 

, its tension, 268, 275. 

-, evolution of heat by, 276. 

, its magnetic forco, 277. 

, its chemical forco, 278. 

, its spark, 280. 

, its physiological effects, 279. 

, its general characters considered, 

268. 

Voltaic pile distinguished, 856, note . 

, electricity of 875. 

, depd&ds on chemical action, 872. 

, relation of acid and bases in' the, 927. 

. See Battery, voltaic. 

Voltaic spark without contact, 915, 956. 
, precaution s5 8, 1074. 


THE 


Voltaic trough, 989. See Battery, voltaic. 

Water, flowing, electric currents in, life# 

, retardation of current by, 1159. 

, its direct conducting power, 1017, 

1159, 1355. 

, constant, 984. 

, electro-chemical decomposition 

a^inst, 494, 532. 

, poles of, 494, 533, 558. 

, its influence in electro-chemical de- 
composition, 472. 

— , is the great electrolyte, 924. 

, the exciting clectrolgte when pure, 

944. 

, acidulated, 880, 926, 1137. 

, alkalized, 931, 934, 941. 

, electrolytic intensity for, 908, 981, 

1017- 

electrolyzed in a single circuit, 862. 

- — -, its electrolysis definite, 732, 785,807. 

^decomposition of by fine wires, 327. 

, cpiantity of electricity in its ele- 
ments, 853, 861. 

, determined to cither pole, 553. 

Wheatstone' s analysis of the electric brudi, 
1427. 

measurement of conductive velocity 

in metals, 1328. 

Wire , ignition of, by the electric currtnf, 
853, note, 1631. 

is uniform throughout, 1630. 

Wire a regulator of the electric current. 
853, note. 

, velocity of conduetion in, varied, 

1333. 

single, a current induced in, 170. 

, long, inductive effects in. 1064, 11)8. 

Wollaston on decomposition by common 
electricity, 309. 

decomposition of water by points, 327. 

Zinc, amalgamated, its condition, 863, 1000. 

, used in pile, 999. 

, how amalgamated, 863. 

of troughs, its purity, 1144. 

, its relation to the electrolyte, 949. 

— , its oxidation is the source of power 

in the pile, 919. 

plates of troughs , foul, 1145. 

, new and old, 1146. 

, waste of, in voltaic batteries, 997. 


END. 


PRINTED BY TAYLOR AND FRANCIS, BED LION COURT, FLEET STREET.