ON THE PHYSICAL VIEW OF NATL'RE. 



l:i3 



foundations on which the theory of heat rests retiuire 

 careful examination.^ Further thought evidently led 

 him to douht the correctness of tlie second assumption. 

 It is the first point to which Thomson, more than 

 twenty years after, directs his attention. He conceives 

 the idea of measuring temperature hy such a scale that 

 for an equal drop in the scale — i.e., Ijy letting down heat 

 by an equal number of degrees on the new scale — equal 

 amounts of work shall be done.^ The speculations of 8adi 

 Carnot remained unnoticed for a long time. Ten years 21. 

 later Clapeyron reverted to the subject, and itut the f.'rapiiicai 



■■^ *' . . method. 



reflections of Carnot into graphical form and into mathe- 

 matical language. He introduced the conception, based 

 on Carnot's theory, of the ratio of heat transferred from 

 a higher to a lower level of temperature to the maxi- 

 mum of work obtainable, — a quantity independent of 

 the substance employed, — and he called this fixed ratio 



Carnot's function. It was 



motrice est . . . due . . . uon h 

 uue consommation rdelle du cal- 

 orique, uiais a son transport d'un 

 corps chaud h un corps froid, c'est- 

 ii-dire iV son retablissement d'equi- 

 libre " (ibid., p. 6). 



^ " Au reste, pour le dire en 

 passant, les principaux fondenients 

 sur lesquelles repose la thot)rie de 

 la chaleur auraient besoin de I'ex- 

 anieu le j)lus attentif. Plusieurs 

 faits d'exporieuce paraissent ii peu 

 pr6s inexplicables dans I'dtat actuel 

 de cette th^orie" (ibid., p. 20, 

 note). " La loi fondamentale que 

 nous avions en vue . . . est assise 

 sur la thc'orie de la chaleur telle 

 (ju'on la conc;oit aujourd'hui, et il 

 faut I'avouer, cette base ne nous 

 parait pas d'uue solidite indbran- 

 lable" (p. 50). As stated above 

 (p. 118, note), Carnot emancipated 



through his paper that 



himself from the conventional or 

 material view of the nature of 

 heat. See the appendix to the 

 edition of 1878. 



- See 'Cambridge Piiilosophical 

 Society Proceedings,' June 1848 ; 

 reprinted in Thomson's (Lord Kel- 

 vin's) ' Matli. and Phvs. Papers,' 

 vol. i. p. 100. 



^ Beiioit I'ierre Emile Clai>eyron 

 was an engineer. In 1834 he puV)- 

 lished, in tlie fourteenth cahier of 

 the 'Journal de I'Ecole Poly tech- 

 nique,' his " Mcmoire sur la Puis- 

 sance motrice de la Chaleur." It 

 was througli a translation of tliis 

 paper in 'Taylor's ScientiKc Mem- 

 oirs' that Thomson lieard about 

 Carnot's earlier work, and tlirough 

 a translation in Poggendorf's 'An- 

 nalen' (1843) that Helmlioltz be- 

 came acquainted witli the subject. 



