70 THE POSTSCRIPT, AUGUST, 1843. 



ment was justified ; for the time, however, it is clear that the 

 essential distinction between these two heats escaped his 

 notice, and allowed him to overstep the real significance of 

 his results. 



It may seem unnecessary to call such pointed attention 

 to misconceptions that were subsequently corrected by Joule 

 himself ; but in their influence on Joule's subsequent career 

 they were not unimportant, as they tended for the time to 

 render his results apparently inconsistent with observations 

 and laws as to the performance of work by means of heat, 

 which were then exciting an increasing interest, and so led 

 some of those best able to judge to reject Joule's results at 

 first sight, without ascertaining their real significance. 



Although Joule adhered to his practical conclusion as to 

 the possibility of the conversion of heat into work, for five 

 or six years, its dazzling effect in obscuring the philosophical 

 significance of his results was only momentary. Having 

 written his paper, he seems at once to have perceived the 

 bearing of his discoveries on phenomena, which had not 

 hitherto .attracted his attention. It is at least remarkable 

 that throughout his papers so far he has not made any 

 reference to the heat produced by friction, although he 

 frequently mentions that part or the whole power developed 

 in his engines was expended in overcoming friction. The 

 papers themselves would bear the interpretation that he had 

 not hitherto realized that there was any other agency but that 

 of electricity, by which heat and work were convertible ;. 

 a view which is to a great extent borne out by the remark- 

 able manner in which he commences a most remarkable 

 postscript, which contains a clear and somewhat full state- 

 ment of his views at the time, showing, in somewhat crude 

 language, that he had already, in August, realized the law now 



