SCIENTIFIC MEMOIRS. 
VOL. I.—PART III. 
ARTICLE XY. 
Memoir on the Motive Power of Heat ; by KE. CLarryron, 
Mining Engineer. 
From the Journal de ’ Ecole Royale Polytechnique; Paris; vol. xiv. p. 153 et seq. 
§ 1. 
Few 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 
aw 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 Bé- 
rard on the specific caloric of gases. Lastly, M. Dulong, in a memoir 
which he published under the title of Recherches sur la Chaleur Spéci- 
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- 
Jated by the same Sraction of their volume, pope a or absorb pods same 
absolute quantity of heat. 
Vou. I.—Parrt II. 2B 
