Royal Society. 75 



On the motion of Dr. Paris, seconded by Professor Baden Powell, 

 it was resolved unanimously : — 



That the best thanks of the Royal Society be, and they are hereby 

 given, to Dr. Roget for his continued and valuable services during 

 a period of twenty-one years, in the office of Secretary to the Society. 



Dec. 7. — " Experimental Researches in Electricity." By Michael 

 Faraday, Esq., F.R.S. Tvpenty- second Series. § 28. On the Cry- 

 stalline Polarity of Bismuth and other bodies, and on its relation to 

 the magnetic form of force. 



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 de- 

 termined to investigate the matter closely, 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 resuspending 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 resuspended 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- 

 crystallic 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, pole ; 

 its diamagnetlc 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 phenomena 

 remain, but the magnecrystallic results disappear, because of the 

 confused and opposing crystalline 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 magne- 

 crystallic axis being, as before, perpendicular to the chief plane of 

 cleavage, and the external form, in this respect, of no consequence. 



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

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

 iron, and with as much force, apparently, as if nothing intervened. 



The position of the crystal in the magnetic field is affected by the 

 approximation of extra magnets or of soft iron ; but the author does 

 not believe that this results from any attractive or repulsive force 

 exerted on the bismuth, but only from the disturbance of the lines of 

 force or resultants of magnetic action, by which they acquire as it 

 were new directions ; and, as the law of action which he gives, is, that 

 the line or axis of magnecrystallic force tends to place itself parallel, 



