162 
INFLUENCE OF FOREST ON HUMIDITY. 
INFLUENCE OF FORESTS ON THE HUMIDITY OF THE AIR AND 
THE EARTH. 
a. As Inorganic Matter. 
The most important influence of the forest on climate is, 
no doubt, that which it exercises on the humidity of the air 
and the earth, and this climatic action it exerts partly as dead, 
partly as living matter. By its interposition as a curtain be¬ 
tween the sky and the ground, it intercepts a large proportion 
of the dew and the lighter showers, which would otherwise 
Dr. Williams’s thermometer was sunk to the depth of ten inches, and gave 
the following results: 
Time. 
Temperature 
of ground in 
pasture. 
Temperature 
of ground in 
woods. 
Difference. 
May 
23. 
62 
46 
6 
U 
28. 
57 
48 
9 
June 
16. 
64 
61 
13 
U 
27. 
62 
51 
11 
July 
16. 
62 
61 
11 
4i 
30. 
65£ 
55£ 
10 
Aug. 
15. 
68 
68 
10 
u 
31. 
59i 
65 
H 
Sept. 
15. 
69£ 
65 
H 
Oct. 
1. 
69£ 
55 
H 
U 
15. 
49 
49 
0 
Nov. 
1. 
43 
43 
0 
u 
16. 
43£ 
43£ 
0 
On the 14th of January, 1791, in a winter remarkable for its extreme 
severity, he found the ground, on a plain open field where the snow had 
been blown away, frozen to the depth of three feet and five inches; in 
the woods where the snow was three feet deep, and where the soil had 
frozen to the depth of six inches before the snow fell, the thermometer, 
at six inches below the surface of the ground, stood at 39°. In consequence 
of the covering of the snow, therefore, the previously frozen ground had 
been thawed and raised to seven degrees above the freezing point.— Wil¬ 
liams’s Vermont , i, p. 74. 
Bodies of fresh water, so large as not to be sensibly affected by local 
influences of narrow reach or short duration, would afford climatic indi¬ 
cations well worthy of special observation. Lake Champlain, which forms 
the boundary between the States of New York and Vermont, presents very 
favorable conditions for this purpose. This lake, which drains a basin of 
about 6,000 square miles, covers an area, excluding its islands, of about 500 
