104 JOULE'S LECTURE. 



Manchester, at St. Ann's Church Reading Room, " On 

 Matter, Living Force, and Heat," which lecture was pub- 

 lished in full in the Manchester Coicrier newspaper, May 5 

 and 12, 1 84/, and has already been quoted in Chapter I. 



In this lecture, Joule gave the first full and clear exposi- 

 tion of the universal conservation of that principle .now 

 called energy. He does not use the term energy ; nor, 

 having abandoned the term caloric, has he any name for 

 the principle ; but he, nevertheless, in very forcible language, 

 shews that he recognises the quantitative measures of the 

 principle in all the "mechanical, chemical or vital" sources 

 of heat as yet known ; and further recognises that all the 

 phenomena of the universe consist of the continual con- 

 version of the principle from one of its modes into another 

 without loss or increase. It is very evident throughout this 

 lecture that Joule had then no clear conception of the 

 agency in the conversion of energy, of what is now 

 expressed as concentration of energy, much less had he any 

 conception that the conversions of the energy, in which all 

 the phenomena of the universe consist, are effected largely 

 at the expense of this agent in accordance with Carnot's 

 theorem. But this ignorance — the ignorance of his time — 

 though it rendered the expression of his own clear con- 

 ception of the law of the conservation of energy difficult, 

 does not in any way invalidate the completeness and truth 

 of this exposition of the grandest generalization in the 

 whole of physical science. 



This exposition, besides being the first ever given, was 

 the only one Joule ever gave, except such as may be 

 gathered from the general tenour of his writings. That 

 he attached great importance to the lecture appears from 

 the following note by Mr. Benjamin Joule. — "James was 



