598 PROTECTION OF DUNES. 
the Northern States, in conjunction with some of the American 
oaks, birches, and poplars, and especially the robinia or locust, 
would prove very suitable to be employed on the sand-hills of 
Cape Cod and Long Island. The ailanthus, now coming into 
notice as a sand-loving tree, some species of tamarisk, and 
perhaps the Aspressus macrocarpa, already found useful on 
the dunes in California, may prove valuable auxiliaries in re- 
sisting the encroachment of drifting sands, whether in America 
or in Europe, and the intermixing of different species would 
doubtless be attended with as valuable results in this as in other 
branches of forest economy. 
It cannot, indeed, be affirmed that human power is able to 
arrest altogether the incursions of the waves on sandy coasts, 
by planting the beach, and clothing the dunes with wood. On 
the contrary, both in Holland and on the French coast, it has 
been found necessary to protect the dunes 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.* 
Besides the special office of dune plantations already noticed, 
these forests have the same general uses as other woods, and 
they have sometimes formed by their droppings so thick a layer 
of vegetable mould that the sand beneath has become sufficiently 
secured to allow the wood to be felled, and the surface to be 
ploughed and cultivated with ordinary field crops. 
In some cases it has been found possible to confine and 
cultivate coast sand-hills, even without preliminary forestal 
plantation. Thus, in the vicinity of Cap Breton in France, a 
peculiar process is successfully employed, both for preventing 
the drifting of dunes, and for rendering the sands themselves 
* See a very interesting article entitled ‘‘Le Littoral de la France,” by 
ELIShE RECLUS, in the Revue des Deux Mondes for December, 1862, pp. 901, 
936, 
