104 OUTLINES OF FORESTRY. 



that which falls on any other part of the earth's 

 surface, either runs rapidly off the surface or 

 sinks slowly into the ground. 



The part that runs directly off the ground will 

 be greater than the part which sinks into the 

 ground, when the surface is bare and devoid of 

 vegetation. On the contrary, the part which sinks 

 into the ground will be greater than the part which 

 runs directly oft' the surface, when the surface is 

 covered by forests. But the proportion of the 

 rainfall which sinks into the ground, as compared 

 with that which runs directly off the surface, is 

 greater where the sides of mountains are covered 

 with forests than in any other case. 



Since the rivers which rise in the mountains are 

 more regularly fed by the springs when the greater 

 part of the rainfall sinks quietly into the ground, 

 and since this occurs on mountains that are 

 covered with trees, the importance of keeping the 

 sides of the mountains well wooded is evident. 



"When the sides of mountains are covered with 

 forests, the rivers that rise on their slopes are not 

 only less apt to overflow their banks during heavy 

 rainfalls, but are also less apt to dry up and be- 

 come shallow during droughts, than if such forests 

 were removed. 



