i86 BOOK VI. 



wide and three digits thick. The sides of each pump-rod are covered and 

 protected by iron plates, which ^re held on by iron screws, so that a part 

 which has received damage can be repaired. In the " claws " is set a 

 small round axle, a foot and a half long and two palms thick. The ends are 

 encircled by iron bands to prevent the iron journals which revolve in the 

 iron bearings of the wood from sHpping out of it.^^ From this little axle 

 the wooden " claws " extend two feet, with a width and thickness of six 

 digits ; they are three palms distant from each other, and both the inner and 

 outer sides are covered with iron plates. Two rounded iron keys two digits 

 thick 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 second 

 pump-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 and 

 is immovable. Each such piston-rod is thirteen feet long and three digits 

 thick, and descends into the first pipe of each pump to such depth that its 

 disc nearly reaches the valve-box. When it descends into the pipe, the 

 water, penetrating through the openings of the disc, raises the leather, and 

 when the piston-rod is raised the water presses down the leather, and this 

 supports its weight ; then the valve closes the box as a door closes an 

 entrance. The pipes are joined by two iron bands, one palm wide, one 

 outside the other, but the inner one is sharp all round that it may 

 fit into each pipe and hold them together. Although at the present time 

 pipes lack the inner band, still they have nipples by which they are joined 

 together, for the lower end of the upper one holds the upper end of the lower 

 one, each being hewn away for a length of seven digits, the former inside, the 

 latter outside, so that the one can fit into the other. When the piston-rod 

 descends 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 run 

 in through the perforations. Each one of such pumps is composed of two 

 lengths of pipe, each of which is twelve feet long, and the inside diameter is 

 seven 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 are 

 six perforations around the pipe through which the water flows into it. The 

 upper 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 is 

 two feet long and one foot wide and deep. There is the same number of 

 axles, " claws," and rods of each kind as there are pumps ; if there are three 

 pumps, there are only two tanks, because the sump of the shaft and the drain 

 of the tunnel take the place of two. The following is the way this machine 

 draws 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 second 

 pump-rod, and the first piston-rod ; then the second pump-rod raises the 

 second " 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, 



^*This description certainly does not correspond in every particular with the 

 illustration. 



