in Alloys of Bismuth and Tin. 



185 



attached at intervals along each rod, one junction of each being 

 fastened to the rod, from which it was separated by a strip of 

 mica, the other being outside the covering of cotton-wool so that 

 it could be immersed in a bath of water. 



Each couple was then joined up in turn with the galvanometer 

 and the water heated until there was no current in the circuit 

 when this was completed. 



The temperature of the bath then indicated the temperature 

 of the rod at the point observed, and thus the temperature and 

 temperature gradient at any point could be found. 



Experiments with Bismuth. 



The specific heat of electricity in this metal has been previously 

 measured by Batelli*, who also found that the value is proportional 

 to the absolute temperature. 



Mean diameter of rods = 5'7 mm. 



Mean resistance of rods = 0-000050 ohms per mm. 

 Some observations taken are shown in Tables I and II, in 

 which H is the time at which the observation was made, y x the 

 value of the compensating current when the current flows in one 

 direction through the rods, 72 the corresponding value when the 

 current in the rods is reversed, and 8 the change in the com- 

 pensating current due to the reversal of the current in the rods. 



Table I. 



Thomson effect. 

 G = 3 amperes. 



6 = 30° C. 

 d6 



dx 



0-525. 



Mean value for 8 : - 376 

 Correction + -003 



0-379 



* loc. cit. 



