4S0 ■WEBER OX THE NATURE OF DI AM AGNETISM. 



exerts upon other magnet-poles at a distance, and uhich have 

 no influence upon its diamagnetic condition. 



Now if a piece of bismuth is placed in the plane which is bi- 

 sected at right angles by a small magnet-needle suspended by a 

 silk thread and symmetrically magnetized, it is evident that the 

 poles of the small needle can have no influence, or at least no 

 perceptible influence, upon the diamagnetic state of the distant 

 piece of bismuth, according to Reich's experiment. In fact it 

 is easily seen that the needle experiences not the slightest deflec- 

 tion by the bismuth. 



But if we arrange a powerful horse-shoe magnet of iron, so 

 that the locality previously occupied by the bismuth is situated 

 in the free space between its two poles, and the magnet is at the 

 same time brought into such a position that its magnetic axis 

 prolonged bisects the needle, this powerful magnet will exert a 

 very great momentum of rotation upon the needle. But if this 

 rotatory action exerted by the horse-shoe magnet is compen- 

 sated by another equally powerful but opposite rotatory action 

 of a bar-magnet brought to bear upon the needle from the op- 

 posite side, we can cause the needle to re-assume its original posi- 

 tion and its original vibratory power (sensitiveness), so that with 

 respect to the needle it is just the same as if no magnet acted 

 upon it. 



Now if, after these preliminary arrangements, the same piece 

 of bismuth which previously had no action upon the needle is 

 brought to the same position as before, i. e. between the two 

 poles of the horse-shoe magnet, a very perceptible and measurable 

 effect is exhibited, viz. a deflection of the needle, owing to one 

 pole being repelled and the other attx'acted. 



If the poles of the magnets, the effects of which upon the 

 needle are compensated, be reversed, and the experiment re- 

 peated, it is found that the same piece of bismuth brought to 

 the same spot and in the very same position, now produces ex- 

 actly the opposite deflection. 



If, lastly, a piece of iron is substituted for the bism.uth, it is 

 found that the deflection produced by the latter is the opposite 

 of that produced by the former. 



These experiments may be variously modified, but In every 

 case the force of the bismuth must be observed upon other mag- 

 net-poles than that which determines the diamagnetic condition 

 of the bismuth ; they all confirm the assertion that bismuth 



