506 Prof. E. Edlund on the Thermal Phenomena of the 



consequently led to the result that these electromotive forces 

 consume heat to form the current ; they are therefore in this 

 respect similar to the thermoelectric forces, which likewise 

 form currents by the consumption of heat. In the same 

 manner do those induced electromotive forces behave which 

 arise through the diminution of the intensity of the inducing 

 current. It is demonstrated by experiments that through in- 

 duction of this sort a loss of heat is produced in the path of 

 the inducing current, which is just equal to the heat-genera- 

 tion produced by the induced current in its path *. If, on 

 the other hand, the induction takes place while the inducing 

 current of constant intensity is brought nearer to or removed 

 further from it, the mechanical work employed for diminish- 

 ing or increasing the distance is consumed in the formation 

 of the current. Finally, as to the electromotive force met 

 with in the electrical discharge spark, in it a portion of the 

 vis viva which is contained in the shock of the discharge, and 

 which is proportional to the mass moved multiplied by the 

 square of the velocity, is transferred to a greater mass possess- 

 ing less velocity f . 



In a previous memoir, I have shown that the laws of gal- 

 vanic induction can be theoretically deduced if we start from 

 the principle that electromotive force consumes heat for the 

 formation of currents J. This principle has proved correct 

 also in the case of the current performing external work. 



§ ii. 



8. From what has been brought forward in the preceding 

 section it follows that it cannot be shown, without arbitrary 

 assumptions, that the heat which the chemical processes 

 develop in a hydroelectric pile gives a measure for the elec- 

 tromotive force. In my opinion, therefore, there is no warrant 

 for the assertion that the chemical and electromotive forces 

 stand in immediate connexion with each other ; while, on the 

 contrary, the results obtained by experiment can very easily 

 be explained if it be admitted that the electromotive force of 

 the pile uses up heat for the production of the current. The 

 only objection of any consequence that was formerly urged 

 against the validity of the contact theory consisted in this — 

 that it could not be shown what the galvanic current was 

 formed from ; for of course it could not be generated out of 

 nothing. This objection, however, lost its force as soon as it 

 could be shown that the current is formed at the expense of 

 heat. This must nevertheless not be interpreted as signifying 



* Posg. Ann. vol. cxxiii. p. 193. t Ibid. vol. cxxxix. p. 355. 



% Ibid. vol. clvii. p. 102. 



