178 



ON THE ECONOMICAL PRODUCTION OF 



will admit that steam may be safely worked at a pressure of 

 14 atmospheres. The temperature of the boiler correspond- 

 ing to that pressure will, according to the experiments of the 

 French Academicians, be 387° Fahr. The temperature of 

 the condenser might be kept at 80°. Reducing the above 

 to temperatures reckoned from the absolute zero, we obtain 

 for the work evolved by the combustion of each grain of coal, 

 W= '^61-45 (84^-539) ^ ^^^..g fo„t.p„„„a. 



It would therefore appear, even in the extreme case which 

 I have adduced, that the performance of the steam-engine is 

 considerably inferior to that of the air engine. The supe- 

 riority of the latter vpould have been still more evident had I 

 also taken an extreme case as an illustration of its economy. 

 It must, moreover, be remarked that the heated air escaping 

 from the engine at a temperature so high as 2191° might be 

 made available in a variety of ways to increase still more the 

 quantity of work evolved. A part of this heated air might 

 also be employed in the furnaces instead of cold atmos- 

 pheric air. 



We may also hope eventually to realize the great advan- 

 tage which would be secured to the air engine by causing the 

 air, in its passage from the pump to the cylinder, to come 

 into contact with the fuel by the combustion of which its 

 elasticity is to be increased. It appears to me that the air 

 might pass through a number of air-tight chambers, each 

 containing ignited fuel, and that whenever any one of the 

 chambers required replenishing, its connexion with the en- 

 gine might be cut oif by means of proper valves, until by 

 removing an air-tight lid or door the chamber could be filled 

 again with fuel. By means of suitable valves, it would be 

 easy to regulate the quantity of air passing through each 

 chamber so as to keep its temperature uniform; and by a 

 separate pipe, furnished also with valves, by which the air 



