CARNOT'S THEORY. 9 1 



the fire must therefore be equal to the heat given out to the 

 condenser was erroneous. In the proof given by Carnot of 

 his theory this deduction enters needlessly, but in illus- 

 trating the application of his theory to the steam engine 

 he has explicitly accepted it, though not without protest. 



Joule, reading Carnot — twice interpreted — seizes on the 

 error of Carnot's illustration as evidence of the existence 

 of views amongst philosophers which are inconsistent with 

 the discoveries which he has made, and as serving to point 

 the importance of the applications of these discoveries. 

 This is only natural, and there is not a word in what Joule 

 says which is not now accepted as strictly true. But what 

 is remarkable is that Joule should have entirely ignored the 

 truth and force of Carnot's theorem, and failed to observe 

 that his own discovery cleared up the only thing obscure in 

 Carnot's, and rendered this as intelligible as it was sound. 

 Had Joule done this — had he observed that the theorem of 

 Carnot was based solely on the indestructibility of caloric 

 in its then accepted sense, as including latent as well as 

 free heat, and that according to his (Joule's) own explicit 

 statements, mechanical power had been previously included 

 in latent heat as in the case of steam, in which the latent 

 heat, as then understood, included the .power spent in over- 

 coming the pressure of the atmosphere — he would have 

 seen that the performance of " work " was essentially a 

 transmission of caloric in the accepted use of the term ; 

 and that so far from refuting the hypothesis as to the 

 indestructibility and uncreatability of caloric he had fully 

 established this hypothesis and given it a rational explana- 

 tion. The term ' caloric ' would not then have been 

 discredited, and would still be used in place of ' energy,' to 

 which place it had not only the right given by 



