84 M. POUILLET ON SOLAR HEAT, 
must conclude that the presence of the sun augments the tem- 
perature of the equatorial zone by 
11675. 
In the same manner, the mean temperature of the atmospheric 
column would be at the equator 
— 149°. 
The preceding formule show that it is about —10°; thus, the 
intermittent presence of the sun increases by 
139° 
the mean temperature of the entire atmosphere in the torrid zone. 
This effect of the sun to augment the terrestrial temperatures 
much exceeds that which M. Poisson obtained in considering the 
variations of temperature at different depths beneath the surface 
of the ground; but it appears to me that the two methods will 
yield results more accordant, when we can introduce in a more 
direct manner, into the formule, the influence of the atmosphere, 
which is so considerable. 
To extend these calculations to other regions, we must take 
into account the decrease of the temperature of the ground in 
proportion as the latitude increases; but, by approximation, it is 
easy to recognise that the effects of the wind concur to raise the 
temperature of the polar regions, by lowering more or less the 
temperatures of the regions comprised between the polar and 
tropical circles; the temperature of the equatorial zone itself 
appears little lowered by this cause. 
The object of this extract is especially to give an idea of the 
theoretical principles and the experimental methods which serve 
as the basis of this investigation. I may be allowed to invite 
the attention of geometricians and natural philosophers particu- 
larly to these two points: with respect to the numbers which 
result from my experiments, they will have to be modified ; 
subsequent researches, simultaneously undertaken on different 
points of the globe, will be necessary to give them all the pre- 
cision which they require. 
