have disappeared, and ships will find free sailing-ground where men are now living and cattle and sheep are pasturing.
Of course, man struggles to defend himself against this enemy. The only way of counteracting its movements is to cover the sand with vegetation and make it inaccessible to the attacks of the wind, and this is not very easily accomplished. The sand consists chiefly—seventy-five to ninety-eight per cent—of uncultivable quartz sand, in which only easily satisfied plants can be made to grow. The wind is, besides, sometimes so strong on the sea-coast as to permit lowly plants to grow only with difficulty, and trees not at all. Sand is, moreover, so fugitive a substance that plants are liable to be torn from it before they have taken firm root. But these hindrances can be overcome, though with difficulty. One of the first instances in which a sand mass was thus tamed was in Denmark in 1738. The sands of the Landes in France have been bound with entire success. Measures of precaution were undertaken in the neighborhood of Dantzic about the middle of the last century. As everywhere else on the Baltic, the dunes had been covered by Nature, except on the side toward the sea, with firs and bushes of all sorts, and thereby protected against the wind. But the ignorant greed of men had removed the wood, grubbed up the stumps, allowed cattle to tread the heaths at will, and treated the dunes so recklessly that their protective covering disappeared, and their sand masses were exposed to the winds. Consequently, at the beginning of the eighteenth century the villages of Kleinvogler and Schmergrube were wholly and Polski partly overwhelmed. It was not till about the middle of the century, when the dunes nearer to Dantzic began to encroach upon the fir-wood appertaining to the city, that measures of protection were thought of. The first measure suggested was the planting of fences of fir-boughs on the comb of the dune, to intercept the sand brought by the wind. This scheme failed. The deposits of sand in front and rear of the hedges made the constant planting of new barriers over the old ones necessary; and the dune increased in height at an alarming rate, involving a great danger of the sudden breaking down of the ridge, when the destruction effected by the sand would be worse than if it had been let alone.
In this dilemma, the Natural History Society of Dantzic, in 1768, offered a prize for the best answer to the question, "What are the most effective and cheapest means of preventing the overflow of the lowlands with sand, and of stopping the further growth of the dunes?" Titius, Professor of Natural History in Wittenberg, gained the prize, by an essay in which he indicated the restoration of the coast-woods as the only permanent remedy, and the planting of a sand-grass (Arundo arenaria) as the measure with which the immediate emergency might be met. His sug-
