746 PLiJCKER ON THE DETERMINATION OF THE 



§ 4. On the Comparison of the Intensities of magnetic attraction 

 and diamagnetic repulsion. 



49. In my memoir on the relation of magnetism to diamag- 

 netisra, I have shown, that when magnetic and diamagnetic sub- 

 stances are mixed, and hence magnetic and diamagnetic forces 

 exist togethei', the former forces decrease less in proportion to 

 the increase of the distance than the latter; hence that the same 

 body may at one time react like a magnetic, at another like a 

 diamagnetic body. It thus follows that it is impossible to ex- 

 press generally by numbers the relative intensities of magnetic 

 and diamagnetic forces ; for how could this be possible when the 

 same body, according to its distance, is at one time attracted, at 

 another repelled by the electro-magnet, so that in the case of 

 the same body the active force may not only diminish, but also 

 change its sign ? In a later memoir upon diamagnetic polarity, 

 I have shown that in the phaenomena above mentioned the 

 distance comes into consideration, not as such, but merely in- 

 asmuch as the force of the electro-magnet diminishes with the 

 distance from the poles ; that, at least, the same body may be 

 diamagnetically repelled by a powerful electro-magnet and at- 

 tracted under the same conditions by a weaker one ; that when 

 the force of the electro-magnet increases, the diamagnetism in- 

 creases in a greater proportion than the magnetism. The law 

 deduced in the former memoir hence holds good, merely ac- 

 quiring a different theoretical interpretation and becoming ex- 

 tended. But now, according to my view, the expression by abso- 

 lute numbers of the quotients of the magnetic atti'action of one 

 body and the diamagnetic I'epulsion of another, must not be 

 attempted ; this quotient is a function of the strength of the 

 electro-magnet. 



I shall next desci-ibe a series of observations, which at first 

 sight appear very surprising, but on further consideration are 

 a necessary consequence of the laws detailed in the previous 

 paragraph. 



50. In the determination of the intensity of the diamagnetic 

 repulsion of phosphorus, as described above, the watch-glass 

 filled with this substance was suspended from one end of the 

 beam, and balanced so as to be kept oscillating close above the 

 two halves of the keeper. On exciting the magnetism by ten 

 Grove's cells, it was attracted, and a weight of about 0"25 grm. 



