MOTIVE POWER OF HEAT. 



that of experiment, let us ascertain how much mo- 

 tive power a kilogram of carbon actually develops 

 in the best-known steam-engines. 



The engines which, up to this time, have shown 

 the best results are the large double-cylinder en- 

 gines used in the drainage of the tin and copper 

 mines of Cornwall. The best results that have 

 been obtained with them are as follows : 



65 millions of Ibs. of water have been raised one 

 English foot by the bushel of coal burned (the 

 bushel weighing 88 Ibs.). This is equivalent to 

 raising, by a kilogram of coal, 195 cubic metres of 

 water to a height of 1 metre, producing thereby 

 195 units of motive power per kilogram of coal 

 burned. 



195 units- are only the twentieth of 3920, the 

 theoretical maximum ; consequently ^ only of the 

 motive power of the combustible has been util- 

 ized. 



We have, nevertheless, selected our example from 

 among the best steam-engines known. 



Most engines are greatly inferior to these. The 

 old engine of Chaillot, for example, raised twenty 

 cubic metres of water thirty-three metres, for 

 thirty kilograms of coal consumed, which amounts 

 to twenty-two units of motive power per kilogram, 

 result nine times less than that given above, 



