MAGNETIC PEEMEABILITY OF NICKEL AND COBALT 



67 



rise of temperature from 15 C. to 222 C., while that of nickel de- 

 creases 22-7 per cent. 



The experiments which 1 have made with cobalt do not seem to be 

 so satisfactory as those made with nickel and iron. There are some 

 things about them which I cannot yet explain; but as they are the only 

 exact experiments yet made on cobalt, they must possess at least a 

 transient value. The difficulties of getting a good cobalt-curve are. 

 manifold, and are due to the following properties (1) its small permea- 

 bility, (2) its sensitiveness to temperature, and (3) its property of having 

 its permeability increased by rise of temperature at all magnetizing- 

 powers within the limits of experiment. The following are the results 



with No. I : 



TABLE IV. 



CAST COBALT, NORMAL, AT 5 C. 

 Experiments made November 27, 1873. 



c* +190* + 120 



... -|i ain *y 



46 



TABLE V. 



CAST COBALT, MAGNETIC, AT 5 C. 

 Experiments made November 28, 1873. 



