106 Prof. E. EdluncPs Investigation of the Electric Light. 



than when it is loaded. Hence the intensity of the induction- 

 current must be greater in the former case than in the latter 

 case, though the entire quantity in circulation is the same in both 

 cases. But since the quantity of heat developed is proportional 

 to the square of the intensity of the current, it may be readily 

 shown that the quantity of heat excited by the induction-currents 

 in the electromagnet and its keeper is greater if the keeper is free 

 and therefore moves quicker, than if it performs mechanical 

 work and its keeper therefore moves more slowly. A similar 

 behaviour is met with in the induction-currents which in both 

 cases are formed in the path of the voltaic current. The inter- 

 vention of induction-currents is in this case so necessary for re- 

 moving the discrepancy in question, that, if it had not been pre- 

 viously known, its existence might probably have been guessed 

 from similar considerations. 



2. Voltaic induction and the absorption of heat in chemical 

 decomposition have long been known; and in the preceding we 

 have endeavoured to show how intimately these phenomena are 

 connected with an accurate conception of force and of work. We 

 will now pass over to a case in which the means have not hitherto 

 been known which nature uses to remove the discrepancy between 

 the demonstrated principle that the development of heat by a vol- 

 taic current depends upon the electromotive force and the re- 

 sistance, and the axiomatic truth that if a force simultaneously 

 brings about two actions, the sum of their quantitative values 

 must be as great as the quantitative value of either of them if 

 this alone is produced. 



Such a case is the electric light which is formed when electri- 

 tricity passes through a gas from one solid conductor to another 

 with development of heat and light. It is a well-known fact 

 that in this luminous arc material particles are detached by 

 the current from one pole and transferred to the other. The 

 positive pole more especially suffers this disintegration, while 

 the negative is less exposed to it. But besides this purely me- 

 chanical work thus performed by the current, chemical decom- 

 position may occur in the arc through the direct cooperation 

 of the current. If the formation of new chemical compounds 

 is to take place there, this cannot be regarded as a direct and 

 exclusive action of the current, but has at any rate partially 

 its cause outside and independently of it. As regards the 

 chemical decompositions, the mechanical work which the current 

 requires for their production has its mechanical thermal equiva- 

 lent in the absorption of heat which thereby ensues. With the 

 purely mechanical disintegration of the poles the case is quite 

 different. No absorption of heat is connected with disintegra- 

 tion, but, on the contrary, a considerable production of heat. 



