196 THOMSON ON CARNOT'S 



quently, the temperature of the water will be 140. 

 Now (Regnault, end of Memoire X.) the latent 

 heat of a pound of saturated steam at 140 is 508, 

 and since, to compensate for each pound of steam 

 removed from the boiler in the working of the 

 engine, a pound of water, at the temperature of 

 the condenser, which may be estimated at 30, is 

 introduced from the hot- well; it follows that 618 

 units of heat are introduced to the boiler for each 

 pound of water evaporated. But the work pro- 

 duced, for each pound of water evaporated, was 

 found above to be 156,556 foot-pounds. Hence 

 JJ5 AV~> or 253 foot-pounds, is the amount of work 

 produced for each unit of heat transmitted through 

 the Fowey Consols engine. Now in Table II. we 

 find 583.0 as the theoretical effect due to a unit de- 

 scending from 140 to 0, and 143 as the effect due 

 to a unit descending from 30 to 0. The difference 

 of these numbers, or 440,* is the number of foot- 

 is from 2| to 5 atmospheres; and, therefore, as we find 

 from Regnault's table of the pressure of saturated steam, 

 the temperature of the water in the boiler must, in all of 

 them, lie between 128 and 152. For the better class of 

 engines, the average temperature of the water in the boiler 

 may be estimated at 140, the corresponding pressure of 

 steam being 3| atmospheres. 

 * This number agrees very closely with the number 



