MOTIVE POWER OF HEAT. 133 



searching investigation before they ought to be 

 admitted, as they usually have been, by almost 

 every one who has been engaged on the subject, 

 whether in combining the results of experimental 

 research, or in general theoretical investigations. 



8. The extremely important discoveries recently 

 made by Mr. Joule of Manchester, that heat is 

 evolved in every part of a closed electric conductor, 

 moving in the neighborhood of a magnet,* and 



* The evolution of heat in a fixed conductor, through 

 which a galvanic current is sent from any source whatever, 

 has long been known to the scientific world ; but it was 

 pointed out by Mr. Joule that we cannot infer from any 

 previously-published experimental researches, the actual 

 generation of heat when the current originates in electro- 

 magnetic induction; since the question occurs, is the lieat 

 which is evolved in one part of the closed conductor merely 

 transferred from tJiose parts which are subject to the inducing 

 influence ? Mr. Joule, after a most careful experimental 

 investigation with reference to this question, finds that it 

 must be answered in the negative. (See a paper "On the 

 Calorific Effects of Magneto-Electricity, and on the Me- 

 chanical Value of Heat; by J. P. Joule, Esq." Read be- 

 fore the British Association at Cork in 1843, and subse- 

 quently communicated by the Author to the Philosophical 

 Magazine, vol. xxiii., pp. 263, 347, 435.) 



Before we can finally conclude that heat is absolutely 

 generated in such operations, it would be necessary to 

 prove that the inducing magnet does not become lower in 



