1863.] 475 



power more than, say, 10 to 20 per cent. According to our experi- 

 ments, the percentage decrement in the conducting power of an 

 impure metal between and 100 varies in the same ratio as the 

 conducting power of the impure metal at 100, compared with that 

 of the pure metal at 100. 



Thus, from specimens Nos. 5, 6, 7, 9, 13, and 15, the conducting 

 power of pure iron was found to be at 0= 16' 725. 



In conclusion, we give the values found for specimens of cobalt 

 and nickel wire lent to us by Professor Wohler. They were as 



follows : 



Cobalt wire. 



corresponding to a percentage decrement of 23' 692 per cent. 



Nickel wire. 



\=12-222-0-040787 + 0-000 7088* 2 , 

 corresponding to a percentage decrement of 2 7' 5 73 per cent. 

 Although these metals were said to be chemically pure, the results 

 obtained seem to indicate that they are not so, having probably taken 

 up some impurities in the process of fusion. 



The following Table of the conducting powers of pure metals 

 shows the place which the metals treated of in this paper take in the 



series. 



Conducting power at 0. 



Silver (hard drawn) ............ lOO'OO 



Copper (hard drawn) .......... 99*95 



Gold (hard drawn) ............ 77'96 



Zinc ........................ 29-02 



Cadmium .................... 23'72 



Cobalt* .................... 17-22 



Iron * (hard drawn) .......... 16*81 



Nickel* .................. .*. 13-11 



Tin ........................ 12-36 



Thallium .................... 9'16 



Lead ...................... 8'32 



Arsenic ............. ....... 4*76 



Antimony .................. 4*62 



Bismuth .................... 1*245 



* Probable value for the pure metal deduced from the observations with the 

 impure one. 



