[1021]. Endless chain of buckets.

[1022]. Archimedean screw; a spiral pipe serves the same purpose as the worm revolving in a cylindrical case.

[Larger plate.]

[1023]. Chain pump, frequently used still. The lower length of pipe should be bored to fit the buckets on chain; the rest of the pipe may be a little larger in diameter and not bored.

[1024]. Lifting wheel for raising water.

The following four examples are machines for raising water to any height by employing a fall of water of comparative low pressure:—

[1025]. Hydraulic ram. A stream of water runs down the incline pipe and flows away at the ball valve; when its speed reaches a certain point it suddenly closes the ball valve, and the shock opens the delivery valve, water flows into the air vessel till the power of the stream is checked, when the delivery valve closes, the ball drops, and the action is repeated.

[1026]. The Robinet. Direct-action water pressure self-acting pump; performs the same work as the hydraulic ram, that is by using a low fall and large quantity of water it raises a smaller quantity to a greater height, the low-pressure water acting on the large double-acting piston. The valve is reversed by the motion of the engine.

[1027]. Hydraulic pumping engine. A modification of the Robinet. A is the driving cylinder, B the pump. The main slide valve is worked by two pistons, and the pressure water distributed by an auxiliary four-way cock or small slide valve, connected to a stop rod from the main crosshead. See also [No. 1741]. See [Sec. 93].