477 



Article XIII. 



On the Excitation and Action of Diamagnetism according to the 

 Laws of Induced Currents, By Prof. W. Weber*. 



[From Poggendorff's Annalen, Jan. 7, 1848.] 



The repulsion of bismuth by a magnet, first observed by Brug- 

 mans in 1778} bad remained almost unknown until Faraday dis- 

 covered it anew and examined it more carefully, and thus laid the 

 foundation for the new doctrine of diamagnetism, the further 

 development of which has become an important physical pro- 

 blem. To solve this question little can be expected from the 

 more delicate processes of measurement, owing to the feebleness 

 of the diamagnetic forces of bodies, even when very powerful 

 electro-magnets act upon them, and it is therefore the more to 

 be expected that we shall become acquainted with the nature of 

 diamagnetism from the various modifications of its effects, the 

 discovery of which is possible even in the case of the most feeble 

 forces. The object of the following experiments is to establish 

 with greater certainty and precision, from some peculiar modi- 

 fications of the diamagnetic effects, a hypothesis already ad- 

 vanced by Faraday to explain the diamagnetic phaenomena, and 

 then to deduce this hypothesis required for the explanation of 

 diamagnetic phaenomena from known laws. 



Diamagnetic bismuth repels both the north and south pole of 

 a magnet, and is repelled by them. This indifferent repulsion 

 of opposite poles might appear of little importance if the origin 

 of the magnetic force were to be sought for in the unvarying 

 metallic particles of the bismuth itself; for we are accustomed to 

 assume generally of the ponderable bodies that they oppose 

 without distinction equal resistance to the movements both of 

 the two opposite magnetic as well as of the two electric fluids. 

 But the action at a distance might appear more surprising than 

 this indifierent effect, were we to admit that the diamagnetic 

 force has its origin in the unvarying metallic particles of the 

 bismuth itself, because it would be the first case in which the 

 action of a ponderable upon an imponderable body at a distance 

 had been observed. It appears therefore above all things im- 

 • Translated by W. Francis, Ph.D., F.L.S. 



