i88 BOOK VI. 



stream can turn it. This water, falling into a race, runs therefrom on to a 

 second high and heavy wheel of a lower machine, whose pump lifts the water 

 out of a deep shaft. Since, however, the water of so small a stream cannot 

 alone revolve the lower water-wheel, the axle of the latter is turned at the start 

 with a crank worked by two men, but as soon as it has poured out into a pool 

 the water which has been drawn up by the pumps, the upper wheel draws 

 up this water by its own pump, and pours it into the race, from which it 

 flows on to the lower water-wheel and strikes its buckets. So both this 

 water from the mine, as well as the water of the stream, being turned down 

 the races on to that subterranean wheel of the lower machine, turns it, and 

 water is pumped out of the deeper part of the shaft by means of two or 

 three pumps. ^** 



If the stream supplies enough water straightway to turn a higher and 

 heavier water-wheel, then a toothed drum is fixed to the other end of the 

 axle, and this turns the drum made of rundles on another axle set below it. 

 To each end of this lower axle there is fitted a crank of round iron curved 

 like the horns of the moon, of the kind employed in machines of this 

 description. This machine, since it has rows of pumps on each side, 

 draws great quantities of water. 



Of the rag and chain pumps there are six kinds known to us, of which 

 the first is made as follows : A cave is dug under the surface of earth or in a 

 tunnel, and timbered on all sides by stout posts and planks, to prevent either 

 the men from being crushed or the machine from being broken by its collapse. 

 In this cave, thus timbered, is placed a water-wheel fitted to an angular axle. 

 The iron journals of the axle revolve in iron pillows, which are held in timbers 

 of sufficient strength. The wheel is generally twenty-four feet high, 

 occasionally thirty, and in no way different from those which are made for 

 grinding corn, except that it is a little narrower. The axle has on one side 

 a drum with a groove in the middle of its circumference, to which are fixed 

 many four-curved iron clamps. In these clamps catch the links of the chain, 

 which is drawn through the pipes out of the sump, and which again falls, 

 through a timbered opening, right down to the bottom into the sump to a 

 balancing drum. There is an iron band around the small axle of the 

 balancing drum, each journal of which revolves in an iron bearing fixed to a 

 timber. The chain turning about this drum brings up the water by the 

 balls through the pipes. Each length of pipe is encircled and protected by 

 five iron bands, a palm wide and a digit thick, placed at equal distances from 

 each other ; the first band on the pipe is shared in common with the 

 preceding length of pipe into which it is fitted, the last band with the succeed- 

 ing length of pipe which is fitted into it. Each length of pipe, except the 

 first, is bevelled on the outer circumference of the upper end to a distance 

 of seven digits and for a depth of three digits, in order that it may be inserted 

 into the length of pipe which goes before it ; each, except the last, is reamed 

 out on the inside of the lower end to a like distance, but to the depth 



^•There is a certain deficiency in the hydraulics of this machine. 



