190 HOLTZMANN ON THE HEAT AND ELASTICITY 
stinctly evidenced, and was even recognised by Poisson himself, 
when they are applied to vapours. 
A second treatise on this subject is the one just mentioned 
by Clapeyron, in so far as it relates to gases. It is founded on 
a work by S. Carnot, which I have not been able to procure, 
and sets out from the view, which is certainly correct, that in the 
passage of heat from one body to another the mechanical action 
developed by the transferer of the heat is independent of the na- 
ture and extent of this bearer *. 
The results he has obtained are correct, so far as the laws of 
Mariotte and Gay-Lussac, assumed by him, are valid; but his 
formulz contain an undetermined function, which in the more 
direct way I have taken is determined, and which gives to those 
formule applicability and their true import. 
I first show how the effect of the heat added to a gas may 
be represented by a purely mechanical action, i. e. by a weight 
which is raised a certain height ; this effect I assume as the ar- 
bitrary measure of the heat, and I arrive by this means at an 
expression for the quantity of heat contained in a quantity of gas 
at a given pressure and at a given temperature, and this with- 
out the employment of any hypothesis. 
One function remains undetermined in this expression; I 
assume, in order to determine it, that the specific heat of a gas 
is independent of the temperature, and I adduce the facts which 
render this assumption most highly probable. With this then 
the quantity of heat in the given gas is fully determined. 
Applications are then made of this determination to these 
phznomena which are exhibited in variations of the density and 
of the temperature of the atmosphere, and the statements ar- 
rived at by theory compared with those of experiment, if any 
such exist. 
With the assistance of the proposition recently confirmed by 
De Pambour, that the quantity of heat is constant in vapours at 
the maximum of tension, the expression advanced gives a for- 
mula for the quantity of heat which indicates the elasticity of 
the vapour by its temperature; this is the same formula to 
which Roche and Von Wrede arrived with other coeffcients, 
and in accordance with which Magnus combined the results of 
his observations. 
From this formula then I determine the expansion of vapours 
* Poggendorff’s dAnnalen, vol. lix. p. 462, 
