64 MOTIVE POWER OF HEAT. 



tact with the air, which is thus kept at a constant 

 temperature during the rarefaction. The body A 

 furnishes the caloric necessary to keep the tem- 

 perature constant. 



(3) The body A is removed, and the air is then 

 no longer in contact with any body capable of fur- 

 nishing it with caloric. The piston meanwhile 

 continues to move, and passes from the position ef 

 to the position gh. The air is rarefied without 

 receiving caloric, and its temperature falls. Let 

 us imagine that it falls thus till it becomes equal 

 to that of the body B\ at this instant the piston 

 stops, remaining at the position gh. 



(4) The air is placed in contact with the body 

 B\ it is compressed by the return of the piston as 

 it is moved from the position gh to the position 

 cd. This air remains, however, at a constant 

 temperature because of its contact with the , body 

 B 9 to which it yields its caloric. 



(5) The body B is removed, and the compres- 

 sion of the air is continued, which being then 

 isolated, its temperature rises. The compression 

 is continued till the air acquires the temperature 

 of the body A. The piston passes during this 

 time from the position cd to the position ik. 



(6) The air is again placed in contact with the 

 body A. The piston returns from the position iJc 



