70 M. POUILLET ON SOLAR HEAT, 
heat. Thus, in dividing the atmosphere, for example, into 100 
concentric strata of the same mass, the individual absorbing 
powers of any two strata will be proportional to the different 
specific heat of these two strata. Near the surface of the earth, 
where the pressure is great and the capacity small, the propor- 
tion of heat absorbed will be consequently less than near the 
limits of the atmosphere, where the pressure is feeble and the 
capacity considerable; we see that at the same time the inferior 
stratum occupies a vertical height much smaller than that of the 
upper stratum. This consideration modifies, as we have stated, 
the quantities of solar heat which reach the summits of the high 
mountains, and it leads to a general expression for these quanti- 
ties of heat, in which it remains to substitute the barometric 
pressures and the corresponding specific heats. It is thus that 
the absorption, which we have found and verified by experiment, 
may extend to the different heights to which it is possible to 
ascend in order to make observations there analogous to those 
which we have made at Paris. 
Lastly, this same principle, and those which have been deve- 
loped above, lead us to express, in a simple manner, the total 
quantity of radiant heat which is emitted in a given time by 
the unity of surface of any atmospheric strata whatever. This 
quantity of heat depends, in fact, only on the peculiar tempera- 
ture of that stratum which we shall represent by ¢, on its capa- 
city for heat c, and on its mass m, then on the number B=1°146, 
which is the constant of the radiation ; and lastly, on an unknown 
constant & which depends on the nature of the elastic fluid; it 
value is then 
Bkmea’. 
For another stratum of the same mass, situated at a greater 
height, the temperature of which would be ?#' and its capacity c', 
the total quantity of heat lost in the same time would be 
la 
Bkme a’. 
This being established, let us consider the state of the atmo- 
sphere under the equator, admitting that the sky there has been 
long unclouded, and that the equilibrium of temperature is there 
established throughout the height of the atmospheric column: 
then, the mean temperature of each day being nearly constant 
upon the soil, and constant also in each of the strata of air, at 
whatever height, the soil and the different strata of the atmo- 
