EMBANKMENT, a mound, or wall of earth, or other materials, used as a defence against the inun dations of rivers, or the extraordinary flux of the sea.
The great value of alluvial soil to the agriculturist, no doubt, gave rise to the invention of banks, or other barriers, to protect such soils from the over flowing of their accompanying rivers. The civilized nations of the highest antiquity were chiefly inhabi tants of vallies and alluvial plains; the soil, moist ure, and warmth of which, by enlarging the parts, and ameliorating the fruits of the vegetable king dom, afforded to man better nourishment, at less la bour, than could be obtained in hilly districts. The country of Paradise, and around Babylon, was flat, and the soil a saponaceous clay, occasionally over flown by the Euphrates. The inhabited part of Egypt was also entirely of this description. Histo rians inform us, that embankments were first used by the Babylonians and Egyptians, very little by the Greeks, and a good deal by the Romans, who embanked the Tiber near Rome, and the Po for many stadia from its embouchure. The latter is perhaps one of the most singular cases of embankment in the world.
The oldest embankment in England is thit of Romney Marsh, as to the origin of which, Dugdale re marks: " that there is no testimony left to us from any record or historian." (History of Embanking and Draining.) It is conjectured to have been the work of the Romans, as well as the banks on each side of the Thames, for several miles above London, which protect from floods and spring tides, several thou sand acres of the richest garden ground in the neigh bourhood of the metropolis.
The commencement of modern embankments in England took place about the middle of the Seven teenth century, under Cromwell. In the space of a few years previously to 1651, 425,000 acres of fens, morasses, or overflown muddy lands, were recovered in Lincolnshire, Cambridgeshire, Hampshire, and Kent; and let at from 2s. 6d. to 30s. an acre. (Harte's Essays, p. 54, 2d edit.) Vermuyden, a Fleming by birth, and a colonel of horse under Cromwell, who had served in Germany during the thirty years' war, was the principal undertaker of these works. The works of this sort constructed in our own times will be found described in the Agricultural Reports of the maritime counties, especially of Lincolnshire, by Ar thur Young.
Previous to entering on the detail of the different descriptions of banks for the purpose of embank ing, we shall here observe, that the pressure of still water against the sides of the vessel contain ing it, being as its depth, it follows, that a bank of any material whatever, impervious to water, whose section is a right angled triangle, and the height of whose perpendicular side is equal to that of the water it is to dam in, will balance or resist this water, whatever may be the breadth of the sur face of the latter ; and, therefore, that as far as width or extent is concerned, it is just as easy to exclude the Atlantic Ocean, as a lake or a river of a few yards in width.