ORIGIN OF SAND--SAND NOW CARRIED DOWN TO THE SEA--THE SANDS OF EGYPT AND THE ADJACENT DESERT----THE SUEZ CANAL----THE SANDS OF EGYPT--COAST DUNES AND SAND PLAINS--SAND BANKS--DUNES ON COAST OF AMERICA--DUNES OF WESTERN EUROPE--FORMATION OF DUNES--CHARACTER OF DUNE SAND--INTERIOR STRUCTURE OF DUNES--FORM OF DUNES--GEOLOGICAL IMPORTANCE OF DUNES--INLAND DUNES-- AGE, CHARACTER, AND PERMANENCE OF DUNES--USE OF DUNES AS BARRIER AGAINST THE SEA--ENCROACHMENTS OF THE SEA--THE LIIMFJORD--ENCROACHMENTS OF THE SEA--DRIFTING OF DUNE SANDS--DUNES OF GASCONY--DUNES OF DENMARK--DUNES OF PRUSSIA--ARTIFICIAL FORMATION OF DUNES--TREES SUITABLE FOR DUNE PLANTATIONS--EXTENT OF DUNES IN EUROPE--DUNE VINEYARDS OF CAPE BRETON-- REMOVAL OF DUNES--INLAND SAND PLAINS--THE LANDES OF GASCONY--THE BELGIAN CAMPINE--SANDS AND STEPPES OF EASTERN EUROPE--ADVANTAGES OF RECLAIMING DUNES--GOVERNMENT WORKS OF IMPROVEMENT. _Origin of Sand._ Sand, which is found in beds or strata at the bottom of the sea or in the channels of rivers, as well as in extensive deposits upon or beneath the surface of the dry land, appears to consist essentially of the detritus of rocks. It is not always by any means clear through what agency the solid rock has been reduced to a granular condition; for there are beds of quartzose sand, where the sharp, angular shape of the particles renders it highly improbable that they have been formed by gradual abrasion and attrition, and where the supposition of a crushing mechanical force seems equally inadmissible. In common sand, the quartz grains are the most numerous; but this is not a proof that the rocks from which these particles were derived were wholly, or even chiefly, quartzose in character; for, in many composite rocks, as, for example, in the granitic group, the mica, felspar, and hornblende are more easily decomposed by chemical action, or disintegrated, comminuted, and reduced to an impalpable state by mechanical force, than the quartz. In the destruction of such rocks, therefore, the quartz would survive the other ingredients, and remain unmixed, when they had been decomposed and had entered into new chemical combinations, or been ground to slime and washed away by water currents.