12 THE BOOK OF FORESTRY 
of the utmost importance to the agriculturist and horti- 
culturist of that region. 
Concerning the influence of forests on climate, 1t may 
be said that large bodies of timber tend to make the 
climate more moderate. In the summer it is always 
cooler in the forest than outside in the open field, and 
strange to say it is warmer in the forest in the wintertime 
than in the open spaces. 
Snow lingers longer in the springtime beneath the 
forest cover and in every way the forest tends to make 
climatic changes more gradual. For a long time scien- 
tists in this country were loath to accept the theory 
that forests had any influence on rainfall, although 
experiments by French foresters had indicated that 
extensive forest cover at high elevations undoubt- 
edly increased the amount of rain and snow. How- 
ever, recent investigations indicate quite clearly 
that rains in the interior of continental America are 
to a large degree dependent upon the presence of large 
bodies of timber situated in the track of prevailing 
winds. 
Concerning the influences of forests upon run-off, 
the beneficial effects are much easier to prove. In fact, 
it is generally known that were it not for the presence 
of forest cover on the steep slopes of our watersheds, 
many of our streams would be raging torrents for a 
few days in the spring and dry, gravelly beds through- 
out the summer season. That a continuous supply of 
water for drinking or power purposes is lacking is often 
due to extensive clear cutting upon a large watershed. 
The wonderful effects of forest cover in increasing 
the length of time in which a raindrop passes from the 
air to the creek or river below can best be likened 
to the action of a layer of sponges or blotting-paper 
