Formation of Downs.[9]
The effects which the sea produces, without the co-operation of rivers, are much less beneficial. When the coast is low, and the bottom sandy, the waves push the sand toward the shore, where, at every reflux of the tide, it becomes partially dried; and the wind, which almost always blows from the sea, drifts it upon the beach. Thus are formed those hillocks of sand, named Downs, which, if the industry of man does not fix them by suitable plants, move slowly, but invariably, toward the interior of the country, and overwhelm fields and dwellings, because the same wind that raises the sand of the beach upon the down, throws that of its summit in the opposite direction from the sea. When the nature of the sand, and that of the water which is raised with it, are such as to form a durable cement, the shells and bones, thrown upon the beach, become incrusted with it. Pieces of wood, trunks of trees, and plants growing near the sea, are enveloped in these aggregates; and thus are produced what might be denominated indurated downs, such as we see upon the coasts of New Holland, and of which a precise idea may be formed from the description given of them by Peron[10].