150
[Book I.
square pieces of plank, fitted so as to fill (like the piston of a commonpump) the bore of the tube, are secured ,to the chain, When the machineis to be used, one end of the trunk js placed in the water, a.nd the otherrests on the bank over whi.ch it is to b.e raised. The upper wheel or rolleris put in motion by a crank applied to its axle, and the pallets as they ascendthe trunk, push the water that enters it before them, tili it is dischargedabove. In machines of this description one half of the chain is alwaysoutside of the tube and exposed to view, but in others the trunk is dividedby a plank, so as to form two separate tubes, one above another, and hencethe chain rises in the lower one and returns down the upper, Thesepumps are represented as exceedingly effective, delivering a volume ofwater equal to the bore of the trunk. Whenever a breach occurs in oneof their canals, or repairs are to be made, hundreds of the neighboringpeasants are summoned to the Work, and in afew hours will empty a largesection of it by these machines.
When a pump is intended to raise a great quantity of water at once, itis made proportionably larger, and is moved by a very simple tread wheel;or rather by a series of wooden arms projecting from various parts of alengthen.ed axle, which imparts motion to the chain, as represented in thefigure.
These arms are shaped like the letter T, and the upper side of each ismade smooth for the foot to rest on. The axle turns upon two uprightpieces of wood, kept steady by a pole stretched across them. The ma-chine being fixed, men treading upon the projecting arms, and supportingthemselves upon the beam across the uprights, communicate a rotary mo.-tion to the chain, the pallets attathed to which draw up a constant andcopious stream of water. Another mode of Working them, which Staun-ton observed only at- Chu-san, was by yoking a buffalo, or other animal, toa large horizontal cog wheel, working into a vertical one, fixed on the