Mechanical Theory of Heat to the Steam Engine, 195 



I "have also carried out this calculation for the above special 

 case, whereby I have obtained the values given in the table for 

 W 



that is for the work done during the expansion by the unit 



of mass. The kilogram is selected as the unit of mass, and 



the kilogram- meter as the unit of work. For — the value 



found by Joule, 423*55, is employed.* For comparison with the 

 numbers in the table I will also add, that we obtain for the 

 work which is done daring the evaporation itself, by the steam 

 which overcomes the external counter-pressure, in the case of 

 which 1 kilogram of water evaporates at the temperature of 

 150° and under a corresponding pressure, the value 18700. 



25° 



63700 



18. We turn our atten- 

 tion now to the consideration 

 of the steam engine itself. 

 In the accompanying sche- 

 matic figure, which is only 

 intended to facilitate the 

 general view of the whole 

 series of processes connected 

 with the action of a com- 

 mon steam-engine, let A rep- 

 resent the boiler, the con- 

 tents of which are kept by 

 the source of heat, at the 

 constant temperature T l . 

 From this, a portion of the 

 steam passes into the cylin- 

 der B, and forces the piston to a certain height. Then the cylin- 

 der is cut off from the boiler, and the steam contained in it, lifts 

 the piston still higher by expansion. The cylinder is thereupon 

 put into connexion with the space O, which shall represent the 

 condenser. We shall assume with respect to this, that it is not 

 kept cool by injected water but by cooling from without, which, 

 as above remarked, produces no important difference in the re- 

 sults, but simplifies the consideration of the subject. Let the con- 



* i is the equivalent of work for the unit of heat, and the above number signi- 

 fies that the quantity of heat which is able to warm 1 kilogram of water from 0° 

 to 1°. when converted into mechanical work gives a quantity of work equal to 

 423 55 Kgr. M. * J * 



t 



150° 



125° 



100° 



75° 



50° 



w 



M 



0 



11300 



28200 



35900 



49300 



