238 Experiments on Diamagnetism. 



shown that a similar effect is produced in most bodies which 

 are attracted by the two magnetic poles ; and these constitute a 

 new species of diamagnetic bodies. We therefore distinguish 

 two classes, repelling and attracting diamagnetic bodies. 



A needle made of a body capable of being attracted by the 

 magnet, but of which the magnetism is not of the same nature 

 as that of iron or nickel, suspeuded between the two polar faces 

 of the electromagnet, takes as is known, the position called by 

 M. Faraday, axial ; but if made to rise above the upper edges, or 

 descend below the lower edges of the polar faces, it takes an equa- 

 torial position. 



The bodies in which I have already found these properties 

 are platinum, palladium, iridium, titanium, an alloy of 0*825 

 tin, 0*024 of bismuth, 0-108 of iron; brass, argentan, charcoal, 

 coke, (the pit-coal is believed to belong to repelling diamagnetic 

 bodies,) obsidian, native carbonate of iron, attracting glass, Prus- 

 sian blue, and the solutions of iron. In the greater number of these 

 bodies the magnetic poles which are obtained during the influ- 

 ence of the electro-magnet, are lost as soon as the influence ceases : 

 notwithstanding they betray themselves when the poles of the 

 electro-magnet are suddenly changed; for then many of these 

 bodies turn half a circle, as a magnetic needle would ; others do 

 not turn entirely, but oscillate enough to show their tendency to 

 change positions. But some attracting diamagnetic bodies, such 

 as a piece of iridium in my possession, charcoal or coke, retain 

 for a longer time the poles which they have acquired. The 

 experimental researches upon the phenomena of these bodies are 

 complicated by this duration of polarity, but they will probably 

 lead to the discovery of the relation which exists between magnet- 

 ism and diamagnetism. 



When a needle made of an attracting diamagnetic body is sus- 

 pended above the upper or below the lower edge of the polar- 

 piece, it takes a position parallel to this edge. In this parallel 

 position, which can as well be either perpendicular to the mag- 

 netic axis of the polar-piece, or parallel, or in any other position 

 conformable to the figure of the polar-piece, the disposition of the 

 magnetic forces in the needle is transversal, as in a repelling dia- 

 magnetic body, but with this difference, that the lower part has 

 a magnetism opposed to that of the polar-piece, and the upper 

 part to that of the same nature. 



I have not yet succeeded in putting iron itself into a diamag- 

 netic state. An iron wire of only one-tenth of a millimetre m 

 diameter, takes an axial direction as well above as between the 

 polar faces, and that with a force which seems nearly sufficient to 

 break a silk thread. To vary this experiment, I put into a quill 

 (which is repellant) a fragment of the same wire, that was only 

 two millimetres long; but this presented the same effects as 

 when the iron was alone. The same effect is obtained by repla- 



