A hydraulic machine, variously constructed, for raising water and other liquids. The common or suction pump is constructed as follows :-The lower end of a long, narrow, vertical pipe, called the suction-pipe, is immersed in a well or reservoir of water, and the upper end communicates with a wider pipe, called the barrel, which has a lid on the top and a spout on one side near the top. The barrel contains two valves, both opening upwards, -the lower one, between the suction-pipe and the barrel, called the suction-valve ; and the upper one, called the piston valve, affixed to the upper surface of a movable piston, connected by a rod with the handle of __ the pump. On working the pump the air below the piston is exhausted, and water is forced into the vacuum and through the lower valve by atmospheric pressure. On the descent of the piston the water above the lower valve, closing that valve by its weight, passes through the piston, and is then lifted to the level of the discharging tube or spout. (See Air-pump and Force-pump.')