1890 - 91 .] Prof. C. G. Knott on Electric Resistance of Cobalt. 309 
sistance begins to increase rapidly with rise of temperature. This 
critical temperature is about the stage 1*5, which corresponds ap- 
proximately to 350° C. The phenomenon may be broadly stated 
in these terms. Between temperatures 400° C. and 700° C. the 
resistance of a cobalt strip increases on the average at a rate 
nearly twice as great as the average rate of increase between 0° 
and 300° C. 
2 o 
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