FOREST PROTECTION. 157 



is travelling inward at the rate of perhaps fifteen feet 

 per year, and is destroying quite a growth of forest trees. 

 This dune is thirty or forty feet high as high as the 

 trees and as the prevailing strong winds are from the 

 east, its tendency is always inland. 



In some parts of Europe, notably in Gascony, France, 

 dunes have destroyed an immense amount of territory 

 in former ages. Whole villages have at times been grad- 

 ually wiped out by the encroaching dunes. The sand is 

 so fine and so easily moved by the wind that there is very 

 little chance for any vegetation to grow on it, and it is 



FIG. 57. Sand-dune near Seven Mile Beach, New Jersey. 



only in recent times that methods have been successfully 

 adopted to hold it in place. 



There are Notable Sand-Dunes at Provincetown on 

 Cape Cod, Mass., on which the State and National govern- 

 ments have expended much money in efforts to hold them 

 in place. These dunes are in three ridges with deep valleys 

 between in which the humus of the ground cover of for- 



