RESISTANCES. 



749 



The numbers of the first column, omitting the factor io 3 , repre- 

 sent the specific resistances estimated, in microhms. The same 

 numbers represent in ohms the resistance of a wire 100 metres in 

 length, having a section of a square millimetre. 



Influence of Temperature. 



The change of resistance and of alloys with the temperature 

 may in general (998) be expressed by the formula 



For mercury in glass, up to 100, the values of the coefficients 

 a and /? are 



0-000,864,9 0*000,001,12* 



0-000,857,7 0*000,000,897! 



For other conductors the results vary with different specimens, 

 arising no doubt from traces of impurities or changes of physical 



* MASCART, DE NERVILLE, and BENO!T, Ann. de Chim. et de Phys. [6], 

 Vol. vi., p. 77. 1884. 



t R. LENZ and N. RESTZOFF. Etudes Ehctrometrologiques, Vol. n. 1884. 



