CONDITIONS FOR THE GROWTH OF TREES. 47 



are also the natural birthplaces of the rivers. 

 The preservation of the forests on the sides of 

 mountains is necessary to insure such a drainage 

 of the rainfall as will hest preserve the uniform 

 flow of the rivers and best prevent them from 

 overflowing their banks in times of rain, or be- 

 coming too shallow in times of drought. 



The preservation of the forests is necessary in 

 certain portions of the lowlands to protect the 

 crops from the direct action of winds that are 

 either too hot or too cold. 



When it is necessary to cut down the forests for 

 the sake of their timber, the areas on which they 

 grew in all cases should be replanted, so that 

 such areas may be able to yield continually suc- 

 cessive crops of timber so necessary for man's 

 needs. 



As to the necessity for an abundance of water 

 well distributed throughout the year in order to 

 insure the growth of trees, Guyot, in his " Earth 

 and Man," * says, on page 189 : 



* " The Earth and Man : Lectures on Comparative Physical 

 Geography in its Relation to the History of Mankind," by 

 Arnold Guyot. Boston: Gould, Kendall & Lincoln, 59 

 Washington Street, 1849. 



