
in Alloys of Bismuth and Tin. oel 
Experiments with this alloy show that the temperature 
changes considerably with the direction of the current, being 
from 1 to 2 degrees higher when the current flows up the 
temperature-gradient than when it flows down the gradient. 
The Thomson effect is hence large and negative. 
For any value of the current there are thus two values of 
@ and d@/dz at each point of either rod, those shown in the 
tables being the mean of the four at the points to which the 
junctions are attached. ) 
In this way the values of the specific heat of electricity 
calculated from the expression on p. 566 are shown -below:— 
dé 
0. da’ o. 
436 ‘475 —11,700 ergs per C.G.S. absolute unit current per 1° C. 
BY her “AT 12,800 aS oe 0 
59°8 ‘61 12,700 33 3 ” 
62:1. -56 13,100 x " 0 
69°3 52 13,800 o os 29 
744 -66 14,300 ” 2 ” 
14 60 14,800 sc ” 39 
It should be explained that the wide differences in the 
values of d@/dz in the above table are due to the fact that 
two different temperature-gradients were used in these ex- 
periments: in the one case the cold bath was filled with 
melting ice as described above, whilst in the second case a 
stream of cold water was caused to flow through this. 
Owing to the inconstancy of the temperature of the water, 
this latter method was abandoned in later experiments. 
The relation between o and @ is represented graphically 
in fig. 2. 
Fig. 2. 

40 50 60 70 a 
From this it appears that the values of o increase much 
more rapidly than the absolute temperature; in fact, a 
straight line drawn through the points as in the figure cuts 
the axis of temperatures at —60° CO. 
