256 M. E. Edlund on the Heat disengaged 



duction, as much heat as the induced current produces in the 

 same time. But the heat which escapes is proportional to the 

 excess of temperature if the latter is inconsiderable. Hence the 

 heat developed in a given time by the induced current is pro- 

 portional to the excess of temperature. M. Edlund has shown 

 by previous experiments that the thermoelectric current, and 

 therefore the deviation which it produces in the galvanometer, 

 are proportional to the excess of temperature*, provided the 

 latter is small. It follows from this that the deflection of the 

 galvanometer is proportional to the heat disengaged in a given 

 time by the platinum wire. After having shown the truth of 

 this proposition by special experiments, and proved moreover by 

 other experiments that the indications of the dynamometer are 

 proportional to \fidt, the author made several experiments to 

 determine the heat disengaged by induced currents. The fol- 

 lowing are some of them : — 



In a first series of experiments the dynamometer was in con- 

 nexion with the internal coil ; the dynamometer was then re- 

 moved and replaced in the circuit by a platinum wire. After 

 having determined the development of heat in the platinum wire 

 by means of the thermoelectric pile and the galvanometer, seve- 

 ral observations were again made with the dynamometer. These 

 experiments were made with inducing currents of different inten- 

 sities. The following are the means of the results obtained : — 



Deflection of the 

 dynamometer. ^vanomet- 



Deflection of the 

 Ivanomet 

 for heat. 



y. x. 



98-8 113-3 



52-4 60-1 



73-75 82-8 



40-9 46-8 



18-3 20-3 



If we calculate the deflections (%) due to the thermoelectric 

 current, supposing them proportional to those of the dynamo- 

 meter (?/), according to the equation x = 1*142/, we get 



Calculated. 



Observed. 



Difference. 



#=112-6 



113-3 



-0-7 



84-1 



82-8 



+ 1-3 



59-7 



60-1 



-0-4 



466 



46-8 



-0-2 



209 



20-3 



* Vide supra. 



+ 0-6 



