A, represents the original reservoir, or spring; the upper surface of which corresponds with the horizontal line B, C, and also with the bottom of the reservoir, K.
D, the main-pipe, which is 112 inch in diameter, and nearly 200 yards in length.
E, is a branch-pipe of similar dimensions, for the use of the kitchen-offices.—Mr. Whitehurst observes, that these offices are situated 18 or 20 feet, at the least, beneath the surface of the reservoir, A, and that the cock, F, is about 16 feet below it.
G, represents a valve-box; and g exhibits the valve.
H, is an air-vessel.
o, o, represent the ends of the main-pipe, which are inserted in the air-vessel, and are bent downwards, to prevent the air from being driven out, when the water is forced into it.
W, denotes the surface of the water.
Mr. Whitehurst remarks that, as water discharged from an aperture beneath a pressure of 16 feet perpendicular height, moves at the rate of 32 feet in one second of time, its velocity from the cock, F, will be in a similar ratio. And, though the aperture of such cock be not nearly equal to the diameter of the pipe, D, yet the pressure of the fluid contained in the pipe will be very considerable: so that if a column of water, 200 yards high, be thus set in motion, and then suddenly stopped by the cock, F, its great force will open the valve, g; and condense the air in the box, H, as often as the water is drawn from the cock. This condensation was sufficient to force the water into the reservoir, K, and even to burst the vessel, H, within a few months after its first construction; though it was made of sheet-lead, in the proportion of 9 or 10lbs. to 1 square foot; and was apparently very firm. Hence it may be rationally concluded, that the impetus of the water is far superior to the simple pressure of the column, I, K; and is therefore equal to a greater resistance (if it were required) than a pressure of four or five feet perpendicular height.
This ingenious contrivance is now applied to a variety of ma-
