646 REGNAULT’S HYGROMETRICAL RESEARCHES. 
the second by 
| L_f'af 
l+af’” 760’ 
0 representing the density of the aqueous vapour in relation to 
the air. 
If y represents the calorific capacity of the air, the quantity 
of heat given out by the dry air of the stratum, in falling from 
the temperature ¢ to the temperature 7’, is 
* 1 es 
iT ROR SN 
The aqueous vapour which existed in this air parts with a quan- 
tity of heat which, designating by k the calorific capacity of the 
aqueous vapour, is 
wa} k ———_ 
oR) 
(¢— 2). 
1 x I 
1+ad!* 760 sae! 
Lastly, let A be the latent se of the aqueous vapour between 
the temperatures ¢ and ¢’; we shall have for the heat absorbed 
by the vapour which forms, 
Rissa Dy doe 
I eid oeEor" 
Equating this last quantity of heat to the sum of the two first, 
we obtain 
wor 
uf ter 1 : 
ia 1+ad!’ 760 PET Cael tat!” eo he oe wh at! 66" “G—t), 
or simply, 
y(h—f!) (¢-t) + bkati—)=8 (f'—2);  . (1) 
whence 
Lott aes 
ge A pay 
1+—(@-“) 14> (¢-2) 
In this formula it is necessary to know, besides the data them- 
selves of the observation,— 
1. The specific heat y of the dry air: M. August admits it to 
be equal to 0°2669, according to the experiments of Laroche and 
Bérard ; 
2. The specific heat & of the aqueous vapour: M. August 
supposes it equal to that of the air, for want of a better datum; 
3. The density 3 of the aqueous vapour: M. August admits 
