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, it 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 



