THE HOLDING AND RECLAMATION OF SAND DUNES 

 AND SAND WASTES. 



Along both sea coasts of this country, near large interior lakes^ 

 and on or about lake or sea bottoms now dry, there often occur 

 more or less extensive belts or low hills of drifting sand. Along^ 

 the sea coast these are formed in large part by the unequal move- 

 ment of the tide, whose flow tends to carry sand beyond the action 

 of the waves, where it is caught by strong prevailing winds and 

 carried up the beach, to be piled into low dunes and hills. As long- 

 as the sand is moist as a result of spray or capillary movement it is 

 not easily moved by the wind, but as soon as the tide ebbs and the 

 sand dries out it is carried up the beach or shore until stones, vege- 

 tation, or irregularities in topography cause it to be deposited. 

 Gradually these accumulations to the leeward of obstructions are 

 built up by fresh supplies of sand until the dune may reach a 

 height of thirty to one hundred or more feet. After the dunes are 

 formed they are held in place through gravity or cohesion of par- 

 ticles. 



Hills originating from deposits of sand left by inland seas or 

 lakes now dry are built up in the same manner as the dunes along 

 our coasts. As the sand is looser and drier they are not as easily 

 held in place as sea dunes. There is less moisture present, though 

 the action of capillarity is probably as great as in coast dunes. The 

 sand hills of Western Nebraska and the dune areas along the Colum- 

 bia River in Washington and Oregon always show moisture a short 

 distance below the surface, the amount depending some- 

 what upon the elevation of the dune or hill and the size and shape 

 of the particles of sand. The presence of moisture in the sand does 

 not prevent it from being carried further inland by strong winds to 

 aid in the formation of other rows of dunes, which may gradually 

 form a belt or range of hills often very wide and many miles in 

 length, as is illustrated by the dune areas along the east shore of 

 Lake Michigan, from Michigan City to the Straits of Mackinaw. 



DUNE MOVEMENT. 



Studies have been prosecuted to a sufficient extent in this country 

 to allow of definite statements as to the rapidity with which dunes 

 along our sea coasts or in the interior are moving. Observations 

 made during several average seasons lead us to believe that, depend- 



