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magnetic bodies repelled by a magnet in virtue of any constant pro- 

 perty possessed by the mass ? Is the force in question a mere repul- 

 sion of ordinary matter, or is the repulsion exercised in virtue of a 

 state of magnetization into which the body is first thrown ? This 

 question is answered in a manner which admits of no doubt. 



It is proved that the repulsion of diamagnetic bodies increases in 

 a quicker ratio than the strength of the magnet which produces the 

 repulsion. Within wide limits, indeed, the repulsion, instead of 

 being simply proportional to the strength of the magnet, is propor- 

 tional to the square of the strength, which leads inevitably to the 

 conclusion that the body thus repelled contributes to the effect pro- 

 duced ; that its repulsion is due to an excited condition into which 

 it is thrown by the influencing magnet, the intensity of this excite- 

 ment varying within the limits already referred to, as the strength 

 of the magnet which produces it. This conclusion is further arrived 

 at by a close comparison of the repulsions of diamagnetic bodies 

 with the attraction of paramagnetic ones : both are found subservient 

 to one and the same law. 



It is next proved that the diamagnetic excitement produced by 

 one pole of a magnet is not the state which enables a pole of an op- 

 posite quality to repel the substance : that each pole induces a con- 

 dition peculiar to itself, or, in other words, that the excitement of 

 diamagnetic bodies in the magnetic field is of a dual character. 



These points being established, a searching comparison is insti- 

 tuted between the phenomena exhibited by paramagnetic and dia- 

 magnetic bodies in three distinct cases : first, when operated on 

 by the magnet alone ; secondly, when operated on by the current 

 alone ; and, thirdly, when operated on by the magnet and current 

 combined. A bar of iron was, in some of these cases, compared with 

 a bar of bismuth, but it was soon found necessary, in order to avoid 

 the proved errors of reasoning, to take strict account of the mole- 

 cular structure of the bismuth. A bar of this substance, cut in a 

 certain manner from the crystallized mass, exhibits between the 

 poles of a magnet precisely the same visible deportment as a bar of 

 iron, while it is well known that the normal deportment of bismuth 

 is opposed to that of iron. The author, in his examination of the 

 points before us, divided paramagnetic bars into two distinct classes, 

 and classified diamagnetic bars in the same manner; one class he 



