34 Mr. Donovan on Galvanometric Deflections. 



ADDENDUM. 



It is proper to mention that the metals employed in the foregoing experiments 

 were all in their commercial state, it appearing probable that the small quantity 

 of foreign matter present in any one of them mnst be exceedingly small. In 

 one case, however, I find that I was mistaken : the purity of the metal, which 

 I designated " nickel," was rendered doubtful by some observations which I 

 subsequently made. At my request it was examined by Professor Apjohn, 

 who found that it consisted of nickel, much arsenic, some cobalt, and a little 

 sulphur. The compound nature of this substance does not, however, invalidate 

 the evidence of the experiments in which it was used. 



