_Shed_ in Old English had the meaning _to separate_ or _distinguish_. It is so used in the _Owl and the Nightingale_, v. 197. Palsgrave (_Lesclarcissement, etc._, p. 717) defines _I shede_, I departe thinges asonder; and the word still means _to divide_ in several English local dialects. Hence, _watershed_, the division or separation of the waters, is good English both in sense and spelling. CHAPTER IV. THE WATERS. LAND ARTIFICIALLY WON FROM THE WATERS: _a_, EXCLUSION OF THE SEA BY DIKING; _b_, DRAINING OF LAKES AND MARSHES; _c_, GEOGRAPHICAL INFLUENCE OF SUCH OPERATIONS--LOWERING OF LAKES--MOUNTAIN LAKES--CLIMATIC EFFECTS OF DRAINING LAKES AND MARSHES--GEOGRAPHICAL AND CLIMATIC EFFECTS OF AQUEDUCTS, RESERVOIRS, AND CANALS--SURFACE AND UNDERDRAINING, AND THEIR CLIMATIC AND GEOGRAPHICAL EFFECTS--IRRIGATION AND ITS CLIMATIC AND GEOGRAPHICAL EFFECTS. INUNDATIONS AND TORRENTS: _a_, RIVER EMBANKMENTS; _b_, FLOODS OF THE ARDECHE; _c_, CRUSHING FORCE OF TORRENTS; _d_, INUNDATIONS OF 1856 IN FRANCE; _e_, REMEDIES AGAINST INUNDATIONS--CONSEQUENCES IF THE NILE HAD BEEN CONFINED BY LATERAL DIKES. IMPROVEMENTS IN THE VAL DI CHIANA--IMPROVEMENTS IN THE TUSCAN MAREMME--OBSTRUCTION OF RIVER MOUTHS--SUBTERRANEAN WATERS--ARTESIAN WELLS--ARTIFICIAL SPRINGS--ECONOMIZING PRECIPITATION. _Land artificially won from the Waters._ Man, as we have seen, has done much to revolutionize the solid surface of the globe, and to change the distribution and proportions, if not the essential character, of the organisms which inhabit the land and even the waters. Besides the influence thus exerted upon the life which peoples the sea, his action upon the land has involved a certain amount of indirect encroachment upon the territorial jurisdiction of the ocean. So far as he has increased the erosion of running waters by the destruction of the forest, he has promoted the deposit of solid matter in the sea, thus reducing its depth, advancing the coast line, and diminishing the area covered by the waters. He has gone beyond this, and invaded the realm of the ocean by constructing within its borders wharves, piers, lighthouses, breakwaters, fortresses, and other facilities for his commercial and military operations; and in some countries he has permanently rescued from tidal overflow, and even from the very bed of the deep, tracts of ground extensive enough to constitute valuable additions to his agricultural domain. The quantity of soil gained from the sea by these different modes of acquisition is, indeed, too inconsiderable to form an appreciable element in the comparison of the general proportion between the two great forms of terrestrial surface, land and water; but the results of such operations, considered in their physical and their moral bearings, are sufficiently important to entitle them to special notice in every comprehensive view of the relations between man and nature.