RELATIONS OF TREES TO WATER. Ill 



of the soil underneath them, made porous by mosses, de- 

 cayed leaves, and other dSlris, so that the plains and val- 

 leys have a moderate oozing supply of moisture for a 

 long time after every shower. Without this covering, the 

 water when precipitated upon the slopes, would immedi- 

 ately rush down over an unprotected surface in torrents 

 upon the space below. 



Every one has witnessed the effects of clearing the 

 woods and other vegetation from moderate declivities in 

 his own neighborhood. He has observed how rapidly a 

 valley is inundated by heavy showers, if the rising 

 grounds that form its basin are bare of trees and planted 

 with the farmer's crops. Even grass alone serves to check 

 the rapidity with which the water finds its way to the 

 bottom of the slope. Let it be covered with bushes and 

 vines, and the water flows with a speed still more dimin- 

 ished. Let this shrubbery grow into a forest, and the 

 valley would never be inundated except by a long-con- 

 tinued and flooding rain. Woods and their undergrowth 

 are indeed the only barriers against frequent and sudden 

 inundations, and the only means in the economy of na- 

 ture for preserving an equal fulness of streams during all 

 seasons of the year. 



At first thought, it may seem strange that the clearing 

 of forests should be equally the cause both of drought 

 and inundations ; but these apparently incompatible facts 

 are easily explained by considering the different effects 

 produced by woods standing in different situations. An 

 excess of moisture in the valleys comes from the drain- 

 age of the hills, and the same conditions that will cause 

 them to be dried up at certain times will cause them to 

 be flooded at others. Nature's design seems to be to pre- 

 serve a constant moderate fulness of streams and stand- 

 ing water. This purpose she accomplishes by clothing 

 the general surface of the country with wood. When 



