DRIFTING OF DUNE SANDS. 
495 
by planting tlie beach, and clothing the dnnes with wood. On 
the contrary, both in Holland and on the French coast, it has 
been found necessary to protect the dnnes themselves by piling 
and by piers and sea walls of heavy masonry. But experience 
has amply shown that the processes referred to are entirely 
successful in preventing the movement of the dunes, and the 
drifting of their sands over cultivated lands behind them ; and 
that, at the same time, the plantations very much retard the 
landward progress of the waters.* 
Drifting of Dune Sands. 
Besides their importance as a barrier against the inroads 
of the ocean, dunes are useful by sheltering the cultivated 
ground behind them from the violence of the sea wind, from 
salt spray, and from the drifts of beach sand which would 
otherwise overwhelm them. But the dunes themselves, unless 
their surface sands are kept moist, and confined by the growth 
of plants, or at least by a crust of vegetable earth, are con¬ 
stantly rolling inward; and thus, while, on one side, they lay 
bare the traces of ancient human habitations or other evidences 
of the social life of primitive man, they are, on the other, bury¬ 
ing fields, houses, churches, and converting populous districts 
into barren and deserted wastes. 
Especially destructive are they when, by any accident, a 
cavity is opened into them to a considerable depth, thereby 
giving the wind access to the interior, where the sand is thus 
first dried, and then scooped out and scattered far over the 
neighboring soil. The dune is now a magazine of sand, no 
longer a rampart against it, and mischief from this source 
seems more difficult to resist than from almost any other drift, 
because the supply of material at the command of the wind, is 
more abundant and more concentrated than in its original thin 
and widespread deposits on the beach. The burrowing of 
* See a very interesting article entitled “ Le Littoral de la France,” by 
£lis£e Reclus, in the Revue des Deux Mondes , for December, 1862, pp. 
901, 936. 
