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BOOK VI.

wide and three digits thick. The sides of each pump-rod are covered andprotected by iron plates, which are held on by iron screws, so that a partwhich has received damage can be repaired. In the “ claws ” is set asmall round axle, a foot and a half long and two palms thick. The ends areencircled by iron bands to prevent the iron journals which revolve in theiron bearings of the wood from slipping out of it . 16 From this little axlethe wooden “ claws ” extend two feet, with a width and thickness of sixdigits ; they are three palms distant from each other, and both the inner andouter sides are covered with iron plates. Two rounded iron keys two digitsthick are immovably fixed into the claws. The one of these keys per-forates the lower end of the first pump-rod, and the upper end of the secondpump-rod which is held fast. The other key, which is likewise immovable,perforates the iron end of the first piston-rod, which is bent in a curve andis immovable. Each such piston-rod is thirteen feet long and three digitsthick, and descends into the first pipe of each pump to such depth that itsdisc nearly reaches the valve-box. When it descends into the pipe, thewater, penetrating through the openings of the disc, raises the leather, andwhen the piston-rod is raised the water presses down the leather, and thissupports its weight ; then the valve closes the box as a door closes anentrance. The pipes are joined by two iron bands, one palm wide, oneoutside the other, but the inner one is sharp all round that it mayfit into each pipe and hold them together. Although at the present timepipes lack the inner band, still they have nipples by which they are joinedtogether, for the lower end of the upper one holds the upper end of the lowerone, each being hewn away for a length of seven digits, the former inside, thelatter outside, so that the one can fit into the other. When the piston-roddescends into the first pipe, that valve which I have described is closed;when the piston-rod is raised, the valve is opened so that the water can runin through the perforations. Each one of such pumps is composed of twolengths of pipe, each of which is twelve feet long, and the inside diameter isseven digits. The lower one is placed in the sump of the shaft, or in a tank,and its lower end is blocked by a round piece of wood, above which there aresix perforations around the pipe through which the water flows into it. Theupper part of the upper pipe has a notch one foot deep and a palm wide,through which the water flows away into a tank or trough. Each tank istwo feet long and one foot wide and deep. There is the same number ofaxles, “ claws,” and rods of each kind as there are pumps ; if there are threepumps, there are only two tanks, because the sump of the shaft and the drainof the tunnel take the place of two. The following is the way this machinedraws water from a shaft. The wheel being turned raises the first pump-rod, and the pump-rod raises the first “ claw,” and thus also the secondpump-rod, and the first piston-rod ; then the second pump-rod raises thesecond “ claw,” and thus the third pump-rod and the second piston-rod;then the third pump-rod raises the third “ claw ” and the third piston-rod,

15 This description certainly does not correspond in every particular with theillustration.