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Irrigation

water, canals, canal, lands, supplied, five, waters and manner

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IRRIGATION is the art of conducting water at pleasure over levels or inclined planes, in such manner that the whole may receive the benefit of partial immer sion ; whereby the surface may be duly supplied with moisture,and the vegetable productions intended to be encouraged, should be enabled to put forth abun dantly, and to yield a good crop. Irriga tion is with us rather a novel practice, but was well understood by the ancients, and has been in use among the Chinese up to the earliest dales of their records. In Hindostan, the whole of the rubbee, or small.grain crop, is artificially watered ; the grain being deposited in October, while the ground remains moist, after the heavy rains which had fallen for months previously to the operations of tillage; so that the seed speedily germinates. But the perfect drought attendant on the five successive month s,would infallibly destroy the promising verdure, were it not that the peasants divide their lands into small squares, about four or five feet each way, between each pair of which a small chan nel, made by banking the soil, pro tempore, in a very simple manner, conducts the lit tle stream supplied from numerous wells made expressly for the occasion. When the ear, or blossom, has shot forth, wa tering is discontinued. The Chinese pro ceed on the grand scale ; they not only divide their fields by numerous channels, but even warp whole tracts of low land; whereby they insure immense returns. The Africans, in some parts, follow the Ilindostanee plan ; but raise their water chiefly from the rivers, or obtain their supplies of that invaluable element from natural reservoirs, formed by the hollows among hills. In every part of Asia, but especially in the Mysore country, former ly under the dominion of the late Sultan Tippoo, the retention of water, for the purposes of irrigation, is a matter of such importance as to be entirely under the auspices and controul of the government. Tippoo caused banks, or, as they are called in India, bonds, to be made be tween the bases of hills, so as to intercept the copious streams, which, during the rainy seasons, flow from the hilly coun try. An example worthy of imitation ! Thus immense bodies of water might be collected in many parts of the United Kingaoms, whence mills and various machinery might be worked, without causing any waste of valuable land ; the soil, in situations appropriate to such purposes, being for the most part poor, and unfit for tillage.

The Milanese territory exhibits the greatest expanse of irrigation known in Europe. In that country are to be seen noble canals running in every direction, totally exempted from local prejudice, private pique, or self-interest. All are under the authority and protection of go vernment, which lets out the water to the various occupiers of meadows, at a fixed rate, according to the quantity supplied. Sometimes these canals are farmed out, by putting up the several sluices to auc tion ; in other instances the canals go with the lands.

Whatever may be the manner in which their water is dispersed, its due preserva tion is an object of general solicitude, on account of the benefits which indivi duals derive from its use ; while the go vernment, both from that motive, and the support of the revenue produced by farming of the canals, do not allow the smallest despoliation to pass unpunished. We are assured, by the best authorities, that the whole of the pasture lands in the Milanese exhibit uncommon fertility; and that the canals are so very extensive, and the branches from them so nume rous, that few need complain of a want of water for irrigation. These works are known to he of no modern date : some have existed for centuries, chiefly apper taining to monasteries ; their waters be ing let out by measure to fertilize their adjacent lands. The great canal, known by the designation of Vecchiabbia, was in a flourishing state early in the eleventh century, beyond which we do not know what might have been its age. In 1220, the great canal of Adda, which waters the plains of Lodi, was finished; in 1305, the canal of Treveglio, which communi cated with four others of very ancient workmanship, was completed ; and in 1460, the canal of Martesano, extending thirty-two English miles: in this aque duct, besides the main branch, of thirty five feet in width, there were made nine teen scaricatori, or lesser canals, which served, when the waters rose very high, to draw off the surplus, so as to prevent injury to the main line, and to prevent inundation along its course : when the latter returned to a more tranquil state, the scaricatori, which were not so deep as the main line, served to supply it with what remained of their contents.

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