348 M. P. Riess on the Generation of Heat bij Electricity. 



Cuthbertson found that the length of wire melted by an electrical 

 battery varied nearly with the square of its charge ; " and at the 

 same time he refers to the researches of Riess on the calorific 

 effects of frictional electricity, acknowledging their priority to 

 his own researches on the heat generated by continuous electric 

 currents. 



I remain, Gentlemen, 



Yours very faithfully, 



William Thomson. 



LIV. On the Generation of Heat by Electricity. By P. Riess. 

 To the Editors of the Philosophical Magazine and Journal. 

 Gentlemex, 



MR. WILLIAM THOMSON has stated, in the Philoso- 

 phical Magazine for March 1854, p. 193, that the quan- 

 tity of heat generated by the discharge of a Leyden jar is pro- 

 portional to the square of the quantity of electricity, which was 

 first proved in 1840 by IMr. Joule, in opposition to the results 

 derived pre-\dously from the experiments of Sir W. Snow Harris. 

 This statement is in all respects incorrect. ]\Ir. Joule never 

 proved the law above stated ; but in a remark attached to his 

 investigation on the heat of the voltaic current he gave utterance 

 to the presumption, that under the necessary limitations the heat 

 generated is proportional to the square of the charge of a given 

 battery. (Phil. Mag. Oct. 1841, p. 265.) When this vague con- 

 jecture was first hazarded, a memoir of mine had been published 

 for four years in whicia the conclusions of Harris were refuted 

 and the law of the square of the current was proved (Pogg. Ann. 

 JNIarch 1837, p. 341) ; and in two extensive inquiries I had 

 already given the complete formula for the heat generated by the 

 battery discharge, after having discovered the remarkable rela- 

 tion subsisting between the quantity of heat generated in a wire 

 and the resistance of the said wire. 



Such reclamations, which cannot be more painful to those 

 who cause them than to those who find themselves compelled to 

 make them, might be avoided if the reasonable demand were 

 everywhere recognized, that an assertion of such a general cha- 

 racter as that ventured by Mr. Thomson ought to be the conse- 

 quence of a careful examination, not only of what has been done 

 at home, but also of what has been published in other countries 

 on the subject in question. 



P. Riess. 



Berlin, April LS, 1854. 



