164 USES OF FORESTS AND OTHER 



Forests serve not only to prevent the wasting of 

 the soil under the pelting influence of the rain but 

 they also greatly restrain the action of the rivers, 

 even the largest. Thus the Mississippi River and 

 other similar great streams are restrained in the 

 destruction they would otherwise bring to the allu- 

 vial plains ort either side of their current by the 

 constant growth of trees which line the banks. 

 Willows, Poplars, and certain other water-loving 

 plants thrive along the banks of the stream, send 

 their roots downward beneath the surface occupied 

 by the flood-waters and so make a strong net-work 

 which resists the cutting action of the river and 

 keeps the stream within narrow bounds. Even in 

 our brooks where they flow through virgin forests 

 the falling trees and other drift-wood make fre- 

 quent dams across the path of the waters, and here 

 the soil washed from the highlands is retained, 

 making little patches of earth. 



Forests also act to prevent floods. If the rain 

 falls on an unforested country the water flows 

 quickly over the bare surface to the brooks and 

 thence to the larger rivers on its way to the sea. 

 In such a region the rain goes away to the ocean 

 as it does from our house roofs or paved streets. 

 When, however, the rain falls upon the forests, 



