THE WORK OF SADI CARNOT. 7 



porting framework of that latest of the sciences. 

 As stated by Tait, in his history of Thermody- 

 namics, the " two grand things" which Carnot ori- 

 ginated and introduced were his idea of a "cycle" 

 and the notion of its " reversibility," when perfect. 

 " Without this work of Carnot, the modern theory 

 of energy, and especially that branch of it which 

 is at present by far the most important in prac- 

 tice, the dynamical theory of heat, could not have 

 attained its now enormous development." These 

 conceptions, original with our author, have been, 

 in the hands of his successors, Clausius and other 

 Continental writers, particularly, most fruitful of 

 interesting and important results ; and Clapeyron's 

 happy thought of so employing the Watt diagram 

 of energy as to render them easy of comprehen- 

 sion has proved a valuable aid in this direction. 



The exact experimental data needed for numer- 

 ical computations in application of Carnot's prin- 

 ciples were inaccessible at the date of his writing; 

 they were supplied, later, by Mayer, by Cold ing, 

 by Joule, and by later investigators. Even the 

 idea of equivalence, according to Hypolyte Car- 

 not, was not originally familiar to the author of 

 this remarkable work; but was gradually developed 

 and defined as he progressed with his philosophy. 

 It is sufficiently distinctly enunciated in his later 



