SCIENTIFIC MEMOIRS. 
VOL. IV.—PART XIV. 
ARTICLE VII. 
On the Heat and Elasticity of Gases and Vapours. By C. 
HoutzmMann, Professor of Natural Philosophy and Mathe- 
matics at the Lyceum, Manheim *. 
[From a Pamphlet published in a separate form. Manheim, 1845.] 
PREFACE. 
POISSON has published a treatise + upon the dependency of 
the density and elasticity of a gas on the quantity of heat it 
contains, which is based on the correctness of Mariotte’s law, 
of Gay-Lussac’s law of the constancy of the coefficient of ex- 
pansion on the application of heat, on the assumption that the 
relation of specific heats, when the pressure and the volume 
are constant, is independent of temperature and pressure ; and, 
finally, on the supposition that the quantity of heat increases 
in proportion to the expansion of the air, the pressure being 
constant. 
Of these assumptions the two first are undoubtedly firmly 
established, at least within very wide limits ; but the third, re- 
Specting the relation of the specific heats, is certainly incorrect, 
as is evident from Clapeyron’s treatise on the motive power of 
heat {, and as will equally appear from this treatise. 
It is from this cause that the results of Poisson’s investi- 
gation are not in harmony with experience, which is most di- 
* From the German by W. Francis, Ph.D., F.L.S. 
Tt Ann. de Chim. et Phys. xxiii. 337, or Gibbert, Ann., Ixxvi. 269 ; likewise 
Poisson, Traité de Mécanique, 2 ed. ii. 637. 
{ Journal de I’ Ecole Polytechnique, t. xiv. 170, and also Scientific Memoirs, 
vol. i. part 3, p. 347. 
VOL. IV. PART XIV. P 
