780 



December 7, 1848, 

 The EARL OF ROSSE, President, in the Chair. 



The Rev. James Challis, George Bishop, Esq., Captain Clerk, R.A. 

 were admitted into the Society. 



The Marquis of Northampton gave notice that His Grace the 

 Archbishop of Canterbury would be proposed at the next Meeting 

 for election and for immediate ballot, to which, as a Spiritual Peer of 

 the Realm, His Grace is entitled. 



Dr. Faraday then delivered the Bakerian Lecture, illustrative of his 

 paper, entitled " Experimental Researches in Electricity. Twenty- 

 second Series. § 28. On the Crystalline Polarity of Bismuth and 

 other bodies, and on its relation to the magnetic form of force." 



In this paper the author states that in preparing small cylinders of 

 bismuth by casting them in glass tubes, he had often been embarrassed 

 by the anomalous magnetic results which they gave, and that having 

 determined to investigate the matter closeh'-, it ended in a reference of 

 the effects to the crystalline condition of the bismuth, which may be 

 thus briefly stated. If bismuth be crystallized in the ordinary way, 

 and then a crystal, or a group of symmetric crystals, be selected and 

 suspended in the magnetic field between horizontal poles, it im- 

 mediately either points in a given direction, or vibrates about a given 

 position, as a small magnetic needle would do, and if disturbed from 

 this position it returns to it. On re-suspending the crystal so that 

 the horizontal line which is transverse to the magnetic axis shall be- 

 come the vertical line, the crystal then points with its maximum 

 degree of force. If it be again re-suspended so that the line parallel 

 to the magnetic axis be rendered vertical, the crystal loses all direc- 

 tive force. This line of direction, therefore, which tends to place 

 itself parallel to the magnetic axis, the author calls the Magne- 

 crysiallic axis of the crystal. It is perpendicular, or nearly so, to the 

 brightest and most perfect of the four cleavage planes of the crystal. 

 It is the same for all crystals of bismuth. Whether this magne- 

 crystallic axis is parallel or transverse to the magnetic axis, the bis- 

 muth is in both cases repelled from a single, or the stronger of two 

 poles ; its diamagnetic relations being in no way affected. If the 

 crystal be broken up, or if it be fused and resolidified, and the metal 

 then subjected to the action of the magnet, the diamagnetic pheno- 

 mena remain, but the magnecrystallic results disappear, because of 

 the confused and opposing cr5'stalline condition of the various parts. 

 If an ingot of bismuth be broken up and fragmentary plates selected 

 which are crystallized uniformly throughout, these also point ; the 

 magnecrystallic axis being, as before, pei-pendicular to the chief 

 plane of cleavage, and the external form, in this respect, of no con- 

 sequence. 



The effect takes place when the crystal is surrounded by masses of 

 bismuth, or when it is immersed in water, or in a solution of 

 sulphate of iron, and with as much force, apparently, as if nothing 

 intervened. 



