For a long period, the only mode of raising water from wells, was by letting down vases or buckets into them by a cord, but gradually the pulley and windlass succeeded, and even irrigation in Eastern countries, upon which the success of their agriculture depends, was carried on by water thus raised from wells, and borne by laborers to the field. The excessive labor and inconvenience of this practice, led to the formation of vast tanks for the collection of water, from which it might be conducted in open channels to the points proposed. In comparison with some of these tanks, our largest reservoirs sink into insignificance. " In the Carnatic, it is recorded, that there are tanks eight miles in length and three in breadth. In Bengal, they frequently cover one hundred acres, and are lined with stone." Knox, in his Historical Relations of Ceylon, says the natives formed tanks two or three fathoms deep, some of which were in length above a mile. The next step in the use of water, was to raise it above its level, and the ma- chines for this purpose are of very ancient date. The Jantu, which has for centuries been, and still is, used in Hindoostan to raise water for the irrigation of land, is thus described by Mr. Ward in his History of the Hindoos. " It consists of a hollow trough of wood about fifteen feet long, six inches wide and ten inches deep, and is placed on a horizontal beam supported on bamboos. One end of the trough rests upon the bank, whether of a pond, river or tank, where a gutter is prepared to carry off the water, and the other is dipped into the reservoir or river, by a man on a stage plunging it in with his feet. A long bamboo with a large weight of earth at the extremity, is fastened to the end of the Jantu next the river, and passing over the gallows before mentioned, poises up the Jantu full of water, and causes it to empty itself into the gutter. This machine raises the water three feet, but by placing a series of these one above another, it may be raised to any height, the water being plunged into small reservoirs sufficiently deep to admit the Jantu above to be plunged low enough to fill it. Water is thus conveyed to the distance of a mile or more." A more efficient machine than this, and even more ancient is the iSwape, or common balance-pole, which is employed so universally in the wells of our own country, and which was employed thirty-four centuries ago, by the 6 PRELIMINARY ESSAY. Egyptians, as appears from sculptures dating back to 1532, B. C., on which these machines are represented, and more especially from the remains of one recently discovered by Mr. Wilkinson in an ancient tomb of Thebes. All nations, ancient and modern, employed this machine ; and the Long Island and New Jersey farmer now raises water from his well, by the same contrivance in use in the time of the Pharoah's. The Swape is still in constant use on the Nile, particularly in Upper Egypt, where the banks are more elevated, arid in which consequently, successive basins of rock or puddled earth are made to receive the contributions of each bucket. The average lift of the Swape is seven feet, and by a series of these, one above the other, the water is finally delivered on the summit of the bank, thence to irrigate the vast plains beyond. The chain of pots is also seen side by side with the Swape, and is the more efficient mechanism, by delivering the water at once at the summit. It is, moreover, worked by animal power — and but that it is taxed by the government double the sum paid by the Swape, would probably supersede it. The tympanum, the noria or Egyptain wheel, the Persian wheel, the chain of pots, and the screw, all improved devices to raise water, were of very ancient use — and so remained until the introduction of the pump. The chain-pump, which is in fact only a modification of the chain of pots, by passing the chain through a tight tube, round or square, and for pots substituting wooden or metallic pallets or pistons, fitting the interior of the tube and pushing the water before them, was known in China from the earliest ages, but does not appear to have been introduced into Europe till about the middle of the seventeenth century ; they are chiefly used now in an improved form on board ships of war. The ordinary pump, or sucking-pump, as it ^vas at first called, though evidently known to the Greeks and Romans, and used in their