THE HOLDING AND RECLAMATION OF SAND DUNES AND SAND 
WASTES BY TREE PLANTING. 
BY H. P. BAKES. 
OKIGIN OF DUNES. 
By a dune we mean a low hill of drifting sand usually formed on the 
sea-coast or shore of large inland lakes. Along the sea-coast the move- 
ment of the tide, the flow of which is more rapid_ than the ebb, tends to 
carry sand beyond the action of the waves, where it is caught by sea 
winds and carried up the beach to be piled in dunes and hills. 
It the land winds are of greater frequency, duration or strength than 
the sea winds, the sands left by the retreating waves will be constantly 
blown hack into the water, but if the prevailing air currents are in the 
opposite direction, the sands soon will be carried out of the reach of the 
highest waves and will be transported continually farther and farther 
into the interior of the land unless obstructed by high grounds, vegeta- 
tion or other obstacles. So long as the sand is kept wet by spray or 
by capillary attraction it is net disturbed by air currents, but as soon 
as the waves retire sufficiently to allow it to dry it becomes the sport of 
the winds and is driven up the gently sloping beach until arrested by 
stones, vegetation, or other obstructions, and thus an accumulation is 
formed which constitutes the foundation of a dune. By successive 
accumulations they gradually rise to the height of 30, 50, 60 or 100 feet, 
and . sometimes even much higher. The dunes once deposited are held 
together and kept in shape partly by mere gravity, and partly by the 
slight cohesion of the lime, clay and organic material mixed with the 
sand; and from capillary attraction, evaporation from lower strata, and 
retention of rain water. 
In working through the sand hill country of western Nebraska, and 
through the dune region of the Columbia river it was an interesting 
thing to find that the sand of the dunes or hills was always moist a little 
below the surface. Even with moisture present strong winds instead of 
adding to the elevation of the dunes sweep off loose particles from their 
surface, and this, with others 'blown between the new-forming dunes 
build up a second row of dunes, and so on according to the character of 
the wind, the supply and consistence of the sand and the face of the coun- 
try. In this way is sometimes formed a belt of sand dunes irregularly 
dispersed and varying much in height and dimensions and often times 
many miles in breadth. 
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