70 A TEXT-BOOK OF GRASSES 
has been reclaimed. In the United States there are several 
areas of sand-dunes, the most important being on Cape 
Cod near Provincetown, Cape Henry, Virginia, along the 
south end and east side of Lake Michigan, and along the 
Columbia River, Oregon, in the semi-arid region. Sand- 
dunes are formed by the wind blowing the dry sand. 
Dunes that are bare of vegetation shift gradually as the 
prevailing wind blows the sand over the crest. When 
vegetation becomes established the wind is unable to 
move the sand and the dunes become fixed. 
Moving dunes may do much damage when formed in 
the vicinity of the works of man by covering up buildings 
or railroad tracks, or, when formed near streams or 
harbors, by diverting the course of the one or filling the 
other, or when formed near a forest which they may over- 
whelm. Sand-dunes are formed along the sandy shores 
of the ocean or of large lakes when the prevailing winds 
are from the water. The waves are constantly throwing 
up sand which, when dry, is blown upon the beach, form- 
ing hills. The same often occurs along rivers in dry regions, 
as along the Columbia above the Dallas, and along the 
Arkansas in western Kansas. 
92. Reclaiming sand-dunes.— Moving dunes are 
worthless for agricultural purposes and may be a menace 
to property. The first step in reclaiming such dunes is 
to fix the sand by applying a covering to prevent its being 
shifted by the wind. Interior dunes have been success- 
fully fixed in Europe by covering with cut heather, a 
common plant in sandy wastes. In other places brush or 
rows of sticks thrust into the sand have served the pur- 
pose. One of the most successful methods has been the 
planting of beach-grass. After the shifting of the sand 
has been prevented by any of these methods, trees are 
