70 A PRIMER OF FORESTRY. 



and is certain to be followed by the formation of tor- 

 rents. The danger is greatest when the soil has been 

 laid bare by the browsing and the hoofs of grazing 

 animals, among which sheep and goats are especially 

 destructive, or where the forest floor has been burned 

 away. 



FIG. 45. Destruction by flood. North Carolina. 



When these conditions are both present, as in parts 

 of the Sierra Nevada Mountains of California, of 

 the Cascade Range in Oregon, and in man} T other 

 parts of the West, the prosperity of the valleys is in 

 serious danger. Fire and overgrazing on the moun- 

 tains combine to endanger the future water supply 

 of irrigated or irrigable areas in the valleys below. 



