MOTIVE POWER OF HEAT. 45 



temperature is more or less elevated, to another in 

 which it is lower. What happens in fact in a 

 steam-engine actually in motion? The caloric 

 developed in the furnace by the effect of the com- 

 bustion traverses the walls of the boiler, produces 

 steam, and in some way incorporates itself with it. 

 The latter carrying it away, takes it first into the 

 cylinder, where it performs some function, and 

 from thence into the condenser, where it is lique- 

 fied by contact with the cold water which it en- 

 counters there. Then, as a final result, the cold 

 water of the condenser takes possession of the 

 caloric developed by the combustion. It is heated 

 by the intervention of the steam as if it had been 

 placed directly over the furnace. The steam is 

 here only a means of transporting the caloric. 

 It fills the same office as in the heating of baths 

 by steam, except that in this case its motion is 

 rendered useful. 



We easily recognize in the operations that we 

 have just described the re-establishment of equi- 

 librium in the caloric, its passage from a more or 

 less heated body to a cooler one. The first of 

 these bodies, in this case, is the heated air of the 

 furnace; the second is the condensing water. The 

 re-establishment of equilibrium of the caloric 

 takes place between them, if not completely, at 



