154 BOVE ON THE ELECTRICITY OF INDUCTION. 



On the contrary, the following exhibited no action : — 



Mercury, bismuth, antimony, sulphuret of antimony, lead, 

 tin, zinc, cadmium, pure silver, pure regulus of arsenic, 

 an alloy of 4 antimony with 1 iron, and an alloy of copper 

 and nickel. 



An attraction between copper and the astatic needles has often 

 been observed in the constructing of multipliers. Thus several 

 years ago Professor Nervander of Helsingfors found during his 

 sojourn in Berlin, amongst a great number of kinds of copper 

 which he tested, only one rod of Japan copper belonging to me 

 which did not attract the delicate needle of his multiplier. 

 Again, Faraday* has found that cobalt and chromium, which 

 have always been considered magnetic, are not magnetic when 

 perfectly free from iron. As a high temperature weakens so 

 materially the magnetic intensity of iron and nickel, it is pos- 

 sible that at a low temperature metals may be magnetic which 

 are not so at common temperatures. But the following metals, 

 tested by a very delicate double needle at temperatures of 60° to 

 70° F., were found to be unmagnetic : — 



Arsenic, antimony, bismuth, cadmium, cobalt, chromium, 

 copper, gold, lead, mercury, palladium, silver, tin and zinc. 



Nevertheless, Pouillet maintains t, in the last edition of his 

 work upon physics, — 



(1.) That cobalt remains constantly magnetic, even at the 

 most intense red heat ; 



(2.) That chromium loses its magnetism somewhat under a 

 dai'k red heat ; 



(3.) That manganese is magnetic at a temperature of 20° to 

 25° C. 



Lastly, M. PoggendorffJ has recently made use of the phae- 

 nomenon of deviation in a twofold direction, first discovered by 

 him with Saxton's machine, for the purpose of showing the mag- 

 netizability of the metals, which up to this time have not been 

 considered possessed of magnetic properties. But nickel, iron 

 and steel are the only ones which gave positive results ; even 

 German silver was not magnetic. 



64. In the iburth section (53) we have seen that the magnetic 

 polarity excited in iron by the discharge of an electric battery 



* London and Edinb. Phil. Mag. viii. p. 177. 

 •f- Elemens de Physique, 3rd edit. i. p. 381. 

 + Poggendoiff's Annalen, xlv. p. 371. 



