A well-known machine used for drawing water from the sea, or discharging it from the ship's pump-well.
♦ Chain-pump, consists of a long chain, equipped with a sufficient number of metal discs armed with leather, fitting the cylinders closely, and placed at proper distances, which, working upon two wheels, one above deck and the other below, in the bottom of the hold, passes downward through a copper or wooden tube, and returning upward through another, continuously lifts portions of water. It is worked by a long winch-handle, at which several men may be employed at once; and it thus discharges more water in a given time than the common pump, and with less labour.
♦ Main pumps. The largest pumps in a ship, close to the main-mast, in contradistinction to bilge pumps, which are smaller, and intended to raise the water from the bilges when a ship is laying over so that it cannot run to the main pump-well. Hand-pump, is the distinctive appellation of the common small pump. Superseded by Downton and others.