STOP Early Journal Content on JSTOR, Free to Anyone in the World This article is one of nearly 500,000 scholarly works digitized and made freely available to everyone in the world by JSTOR. Known as the Early Journal Content, this set of works include research articles, news, letters, and other writings published in more than 200 of the oldest leading academic journals. The works date from the mid-seventeenth to the early twentieth centuries. We encourage people to read and share the Early Journal Content openly and to tell others that this resource exists. People may post this content online or redistribute in any way for non-commercial purposes. Read more about Early Journal Content at http://about.jstor.org/participate-jstor/individuals/early- journal-content . JSTOR is a digital library of academic journals, books, and primary source objects. JSTOR helps people discover, use, and build upon a wide range of content through a powerful research and teaching platform, and preserves this content for future generations. JSTOR is part of ITHAKA, a not-for-profit organization that also includes Ithaka S+R and Portico. For more information about JSTOR, please contact support@jstor.org. 523 November 15, 1855. Colonel SABINE, R.A., Treasurer and V.P., in the Chair. William John Hamilton, Esq., was admitted into the Society. In accordance with the Statutes, notice was given of the ensuing Anniversary Meeting for the election of Council and Officers. The Chairman stated that Edward Blackett Beaumont, Esq., who at the late Anniversary Meeting ceased to be a Fellow of the Society in consequence of the non-payment of his subscription, had applied to the Council to be reinstated, alleging that he " had inadvertently omitted to pay his subscription at the proper period." Notice was therefore given that the question of Mr. Beaumont's re-admission would be put to the ballot at the ensuing Meeting of the Society. A paper was in part read, entitled, — " Experimental Re- searches in Electricity. Thirtieth Series." By Michael Earaday, Esq., D.C.L., F.R.S. &c. Received October 24, 1855. November 22, 1855. Sir BENJAMIN BRODIE, Bart., V.P., in the Chair. George Fergusson Wilson, Esq., was admitted into the Society. In accordance with the notice, given at the last Meeting of the Society, the question of Mr. Beaumont's re-admission into the Society was put to the ballot. VOL. VII. 3 A 524 The ballot having been taken, Mr. Beaumont was declared to be re-admitted. In accordance with the Statutes, notice was given of the ensuing Anniversary Meeting; and the following names of noblemen and gentlemen proposed as Officers and Council for the ensuing year were read : — President. — The Lord Wrottesley, M.A. Treasurer. — Colonel Edward Sabine, R.A. f William Sharpey, M.D. Secretaries. — < „ _ , . , ._ , ■ I George Gabriel Stokes, Esq., M.A. Foreign Secretary. — Rear- Admiral W. H. Smyth. Other Members of the Council. — The Duke of Argyll ; Neil Arnott, M.D. ; Rear-Admiral F. W. Beechey ; Sir Benjamin Brodie, Bart. ; William Benjamin Carpenter, M.D. ; Arthur Cayley, Esq. ; Rev. James Challis, M.A. ; Charles Darwin, Esq., M.A. ; Sir Philip de M. Grey Egerton, Bart. ; William Fair- bairn, Esq. ; John Miers, Esq. ; William Allen Miller, M.D. ; William Hallows Miller, Esq., M.A. ; James Paget, Esq. ; John Stenhouse, LL.D. ; Rev. Robert Walker. I.The reading of Dr. Faraday's paper, "Experimental Researches in Electricity — Thirtieth Series/' was resumed and con- cluded. The following is an abstract : — * § 38. Constancy of differential magnecrystallic force in different media. — That a magnecrystal formed into a sphere (or some equiva- lent shape, so that mere length should have no influence) sets with the same force in the magnetic field, whatever the magnetic nature of the medium around it, has been shown generally, and for a few cases, on former occasions. The author was under the necessity of verifying and enlarging the old results ; and upon employing the following magnecrystals, namely bismuth, tourmaline, carbonate of * Series XXIX. is published in the Phil. Trans, for 1852, p. 137. 525 iron, red ferroprussiate of potassa, and also compressed bismuth, sur- rounded in succession by the following media, — phosphorus, alcohol, oil, camphine, water, air, and saturated solution of protosulphate of iron, he found the result to be the same as before. The mode of estimating the set was as follows : — The selected crystal being sus- pended in the magnetic field by a torsion-wire, right-handed force was then slowly applied by the revolutions of the torsion-head above, until the crystal being gradually carried round, attained that position at which any additional torsion-force would cause it to advance sud- denly and considerably ; this position was called the upsetting point ; then left-handed torsion was put on until the like point was attained in the opposite side : the amount of the revolution of the torsion-index from one upsetting point to the other, minus the angle between the upsetting points, was considered as the measure of the set of the crystal under the constant magnetic force employed. As the setting force of a crystal remained constant for any sur- rounding medium, it was evidently possible to select a crystal and a medium such, that in one position the crystal would be attracted, and in another, at right angles to the first, be repelled in the same medium. This case was realized with the paramagnetic red ferroprussiate of potassa and a solution of sulphate of iron, and also with the diamagnetic crystal carbonate of lime and diluted alcohol. A crystal was sought for amongst the ferrocarbonates of lime having this relation to the assumed natural zero presented by a vacuum or carbonic acid ; but this case was not realized. § 39. Action of heat on magnecrystals. — When magnecrystals, subjected to the same constant magnetic force, were raised or lowered to different temperatures, it was found that the setting force was affected ; and at all temperatures from 0° F. upwards the force diminished as the temperature became higher. Thus the torsion- force of a crystal of bismuth at 92° being 175, was at 279° dimi- nished to 82 ; that of a tourmaline, by passing from the tem- perature of 79° to 289°, was so far diminished ; that the power at the lower temperature was nearly double that at the higher. A like result occurred with carbonate of iron, and also with com- pressed bismuth. In all these cases the bodies resumed their first full power on returning to lower temperatures, nor was there any appearance of magnetic charge in any part of the range of observa- 3a2 526 tions. Between 32° and 300° the force of bismuth appeared to alter by regular equal degrees ; but with tourmaline and carbonate of iron the change was greatest for an equal number of degrees at the lower temperatures. At a full red heat, however, both tourmaline and calcareous spar retained a portion of their magnecrystallic force or condition, and so did carbonate of iron up to that temperature at which it was decomposed. It is known that pure calcareous spar points with its optic axis equatorially, but that calcareous spar containing a trace of iron points with its optic axis axially. Calcareous spar retains its mag- netic characters at very high temperatures, but carbonate of iron and oxide of iron lose almost the whole of their magnetic force at a dull red heat. It was therefore expected that a ferrocarbonate of lime crystal might become absolutely reversed in condition by change of temperature, and this was found to be the case : at low temperatures the optic axis pointed axially, and at high temperatures equatorially ; and that through any number of changes, as the temperature of the crystal was alternately lowered and raised. § 40. Effect of heat upon the absolute magnetic force of bodies. — Results were sought for, by which the magnetic force of bodies, already examined in the condition of magnecrystals, might be com- pared with the whole paramagnetic or diamagnetic force of the same bodies taken in the granular or amorphous state ; but they were not satisfactory. The carbonate of iron gave the most distinct results ; and in its case the change of power by change of temperature was not the same for the two conditions. An examination of the three metals, iron, nickel, and cobalt, at temperatures between 0° and 300° F., gave a very interesting result, which the author is not aware has as yet been noticed. As the temperature rises, the force of the nickel diminishes, the force of the iron remains constant, the force of the cobalt increases ; these facts suggest that there is a temperature at which the magnetic force is a maximum, and above or below which it diminishes. The order with the three bodies accords perfectly with that in which they lose the chief amount of their magnetic power, for much loss occurs with nickel at the tem- perature of boiling oil, with iron at a dull red heat, and with cobalt at a temperature 1 near that of melting copper. 527 The following communication was also read : — II. " Discussion of the observed Deviations of the Compass in several Ships, Wood-built and Iron-built; with General Tables for facilitating the examination of Compass-devia- tions." By G. B. Airy, Esq., F.R.S., Astronomer Royal. Received September 14, 1855. [A paper by the author, with the above title, was read on the 21st of June, 1855 ; it was subsequently withdrawn for the intro- duction of certain alterations, and, so altered, constitutes the present communication. An abstract is given under the above date, p. 491.] November- 30, 1855. Anniversary. A Report of this Meeting will appear in a subse- quent Number. December 6, 1855. Sir BENJAMIN BHOD1E, Bart., V.P., in the Chair. The Chairman announced that the President had appointed the following gentlemen Vice-Presidents : — Colonel Edward Sabine, R.A. Rear-Admiral Beechey. Sir Benjamin Brodie, Bart. Charles Darwin, Esq: Sir Philip de M. G. Egerton, Bart. William Allen Miller, M.D.