17S TOTAL INFLUENCE OF THE FOREST ON TEMPERATURE. 
must, in the study of the climatology of a country, take into 
account the proportion between the area of the forests and the 
surface which is bared of trees and covered with herbs and 
orasses. 
“We should be inclined to believe, @ priort, according to the 
foregoing considerations, that the clearing of the woods, by 
raising the temperature and increasing the dryness of the air, 
ought to react on climate. There is no doubt that, if the 
vast desert of the Sahara were to become wooded in the 
course of ages, the sands would cease to be heated as muchas at 
the present epoch, when the mean temperature is twenty-nine 
degrees [Centigrade, = 85° Fahr.]. In that case, the ascend- 
ing currents of warm air would cease, or be less warm, and 
would not contribute, by descending in our latitudes, to 
soften the climate of Western Europe. Thus the clearing of 
a great country may react on the climates of regions more or 
less remote from it. 
“The observations by Boussingault leave no doubt on 
this point. This writer determined the mean temperature of 
wooded and of cleared points, under the same latitude, and at 
the same elevation above the sea, in localities comprised be- 
tween the eleventh degree of north and the fifth degree of 
south latitude, that is to say, in the portion of the tropics near- 
est to the equator, and where radiation tends powerfully during 
the night to lower the temperature under a sky without 
clouds.” * 
The result of these observations, which has been pretty 
generally adopted by physicists, is that the mean temperature 
of cleared land in the tropics appears to be about one degree 
Centigrade, or a little less than two degrees of Fahrenheit, 
above that of the forest. On page 147 of the volume just 
cited, Becquerel argues that, inasmuch as the same and some- 
times a greater difference is found in favor of the open 
ground, at points within the tropics so elevated as to have a 
temperate or even a polar climate, we must conclude that the 
> BECQUEREL, Des Climats, etc., pp. 139-141. 
