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Plate XCIX.—Hydrostatics.—Fig. 1. A quadruple pump-mill for raising water. more
The height of modern technology in 1771: a super-efficient pump powered by a water wheel!
The ngine is represented in Plate 99. fig. 1. In which ABCD is a wheel, turned by water according to the order of the letters. On the horizontal axis are four small wheels, toothed almost half round; and the parts of their edges on which there are no teeth are cut down so as to be even with the bottoms of the teeth where they stand.
The teeth of these four wheels take alternately into the teeth of four racks, which hang by two chains over the pullies Q and L; and to the lower ends of these tacks there are four irons fixed, which go down into the four forcing pumps, S, R, M, and N. And, as the wheels turn, the tacks and pump-rods are alternately moved up and down.
Thus, suppose the wheel G has pulled down the rack I, and drawn up the rack K by the chain: as the last tooth of G just leaves the uppermost tooth of I, the first tooth of H is ready to take into the lowermost tooth of the rack K, and pull it down as far as the teeth go; and then the rack I is pulled upward through the whole space of its teeth, and the wheel G is ready to take hold of it, and pull it down again, and so draw up the other —— In the same manner, the wheels E and F work the racks O and P.
These four wheels are fixed on the axle of the great wheel in such a manner, with respect to the positions of their teeth, that whilst they continue turning round, there is never one instant of time in which one or another of the pump rods is not going down and forcing the water. So that, in this engine, there is no occasion for having a general air-vessel to all the pumps, to procure a constant stream of water flowing from the upper end of the main pipe.
From each of these pumps, near the lowest end, in the water, there goes off a pipe, with a valve on its farthest end from the pump; and these ends of the pipes all enter one close-box, into which they deliver the water; and into this box, the lower end of the main conduct pipe is fixed. So that, as the water is forced or pushed into the box, it is also pushed up the main pipe to the height that it is intended to be raised. (p. 810)