252 APPENDIX B. 



According to the above-mentioned theory, we 

 can foresee that the use of these liquids would 

 present no advantages relatively to the economy 

 of heat. The advantages would be found only in 

 the lower temperature at which it would be possi- 

 ble to work, and in the sources whence, for this 

 reason, it would become possible to obtain caloric. 



NOTE G. This principle, the real foundation 

 of the theory of steam-engines, was very clearly 

 developed by M. Clement in a memoir presented 

 to the Academy of Sciences several years ago. 

 This Memoir has never been printed, and I owe 

 the knowledge of it to the kindness of the author. 

 Not only is the principle established therein, but 

 it is applied to the different systems of steam- 

 engines actually in use. The motive power of 

 each of them is estimated therein by the aid of 

 the law cited page 92, and compared with the re- 

 sults of experiment. 



The principle in question is so little known or 

 so poorly appreciated, that recently Mr. Perkins, a 

 celebrated mechanician of London, constructed a 

 machine in which steam produced under the pres- 

 sure of 35 atmospheres a pressure never before 

 used is subjected to very little expansion of vol- 

 ume, as any one with the least knowledge of this 

 machine can understand. It consists of a single 

 cylinder of very small dimensions, which at ench 



