SCIENTIFIC MEMOIRS. 



VOL. I.— PART III. 



Article XV. 



Memoir on the Motive Poiver of Heat ; by E. Clapeybon. > 

 Mining Engineer. 



From the Journal de V Ecole Royale Polytechnique; Paris; vol. xiv. p. \b2 et seq. 



§1- 



X? EW questions are more worthy of fixing the attention of geometers 

 and natural philosophers than those which relate to the constitution of 

 gases and vapours : the functions they exercise in nature, and the ad- 

 vantages which industry derives from them, account sufficiently for the 

 numerous and important labours of which they have been the object : 

 this vast question, however, is far from being exhausted. The law of 

 Mariotte and that of Gay-Lussac, which establish the relations exist- 

 ing between the volume, the pressure, and the temperature of a given 

 quantity of any gas, have both long since obtained the assent of scientific 

 men. The experiments recently made by MM. Arago and Dulong leave 

 no doubt of the accuracy of the first of those laws within very ex- 

 tended limits of pressure ; but these important results give no information 

 respecting the quantity of heat which the gases contain, and which is dis- 

 engaged by pressure or diminution of temperature, — they do not give the 

 law of the specific caloricswhen the pressure and the volume are constant. 

 This part of the theory of heat, however, has been the object of profound 

 researches, among which we may cite those of MM. La Roche and Be- 

 rard on the specific caloric of gases. Lastly, M. Dulong, in a memoir 

 which he published under the title of Recherches sur la Chaleur Speci- 

 fique des Fluides Elastiques, has established by experiments free from 

 all objection, that equal volumes of all elastic fluids at the same tempe- 

 rature and under the same pressure, being suddenly compressed or di- 

 lated by the same fraction of their volume, disengage or absorb the same 

 absolute quantity of heat. 



Vol. I — Part III. 2 b 



