TOTAL INFLUENCE OF THE FOREST. 
161 
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 
nearest to the equator, and where radiation tends powerfully 
during the night to lower the temperature under a sky with¬ 
out 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 forests in 
Northern America exert a refrigerating influence equally pow¬ 
erful. But the conditions of the soil are so different in the two 
regions compared, that I think we cannot, with entire con¬ 
fidence, reason from the one to the other, and it is much to be 
desired that observations be made*on the summer and winter 
temperature of both the air and the ground in the depths of 
the North American forests, before it is too late.f 
* Becquerel, Des Climate , etc., pp. 139—141. 
t Dr. Williams made some observations on this subject in 1789, and in 
1791, but they generally belonged to the warmer months, and I do not 
know that any extensive series of comparisons between the temperature of 
the ground in the woods and the fields has been attempted in America. 
11 
