SAND-DRIFT is sand driven and accumulated by the wind. Deposits thus formed are occasionally found among the stratified rocks, but compared with other strata they are few, though, from their anomalous character, an acquaintance with their phenomena is of importance to the geologist. Moving sands are at the present day, in many places, .altering the surface of the land. In the interior of great dry continents, as Africa, India, and Australia, extensive districts are covered with moving sands. The continuous blowing of a steady wind in one direction often covers a rich tract with this arid material. But the influence of the wind on loose sand is most evident along low sandy •coasts, where hills, called "dunes," are formed entirely of it; they sometimes attain a considerable height, as much, for instance, as 200 or 300 feet. Dunes are advancing on the French coasts of the bay of Biscay at the rate of about 60 ft. per annum, covering houses and farms in their progress. Similar accumulations are forming on the coasts Cornwall, Wexford, and other parts of the British isles. The Culbin sands, in Nairnshire, cover a large district which at a period not very distant was rich arable land. The prevailing wind is from the w., hence the hills are slowly moving in an
easterly direction, at the rate of a mile in somewhat less than a hundred years. A .singular stratification exists in these bills. The prevailing w. wind lifts, or rather rolls the particles of sand up the gentle incline of the western aspect of the hill, until they reach the summit, where they fall, forming a steep declivity to the e., equal to the .angle of repose for sand. A shower consolidates the surface of the new bed, or a land breeze carrying the fine dust separates it by a very thin layer of finer material from the •one that follows, and thus, as the bill moves eastward, a regular series of strata is formed at a very high angle. Little can be done to arrest the progress of these devastating sand drifts. It has been recommended to plant came arenaria and similar sand-loving plants, which have long creeping roots: they certainly check to a considerable extent the influ ence of the wind.