368 M. CLAPEYRON ON THE MOTIVE POWER OF HEAT. 
(See the note appended to this Memoir.) 
We shall now deduce various consequences from the general equation 
at which we have arrived. 
We have previously seen that when we compress a body by the quan- 
tity dv, the temperature remaining constant, the heat disengaged by 
the condensation is equal to 
r (4 =) 
|aa_ aq \ae) |, 
pa oe BB (ZF | 
dp a 
dQadT dQdT_¢ 
dQ=dv 
and as 
the preceding expression takes the form 
IQmdy = —dp 
array 
G dv 
This last equation may be put under the form 
dv 
dQ=-—d piece 
= is the differential coefficient of the volume with regard to the tem- 
perature, the pressure remaining constant. 
We thus arrive at this general law, which is applicable to all the sub- 
stances of nature, solid, liquid, or gaseous : Jf the pressure supported by 
different bodies, taken at the same temperature, be augmented by a small 
quantity, quantities of heat will be disengaged from it, which will be pro- 
portional to their dilatability by heat. 
This result is the most general consequence deducible from this axiom: 
that it is absurd to suppose that motive force or heat can be created 
gratuitously and absolutely. 
§ VI. 
The function of the temperature C is, as we see, of great importance, 
in consequence of the part it, sustains in the theory of heat: it enters 
into the expression of the latent caloric whichis contained in all sub- 
stances, and which is disengaged from them by pressure. Unfortu- 
nately no experiments have been made from which we can determine 
the values of this function, corresponding to all the values of the tem- 
perature. To obtain ¢ = 0 we must proceed in the following manner. 
