54 MOTIVE POWER OF HEAT. 



The operations which we have just described 

 might have been performed in an inverse direction 

 and order. There is nothing to prevent forming 

 vapor with the caloric of the body B, and at the 

 temperature of that body, compressing it in such 

 a way as to make it acquire the temperature of the 

 body A, finally condensing it by contact with this 

 latter body, and continuing the compression to 

 complete liquefaction. 



By our first operations there would have been 

 at the same time production of motive power 

 and transfer of caloric from the body A to the 

 body B. By the inverse operations there is at the 

 same time expenditure of motive power and return 

 of caloric from the body B to the body A. But 

 if we have acted in each case on the same quantity 

 of vapor, if there is produced no loss either of 

 motive power or caloric, the quantity of motive 

 power produced in the first place will be equal to 

 that which would have been expended in the second, 

 and the quantity of caloric passed in the first case 

 from the body A to the body B would be equal to 

 the quantity which passes back again in the second 

 from the body B to the body A ; so that an indefi- 



B a mass of ice ready to melt, these bodies might, as we 

 know, furnish or receive caloric without thermometrig 

 change. 



