196

BOOK VI.

The fifth pump of this kind is partly like the third and partly like thefourth, because it is turned by strong men like the last, and like the thirdit has two axles and three drums, though each axle is horizontal. Thejournals of each axle are so fitted in the pillows of the beams that they cannotfly out ; the lower axle has a crank at one end and a toothed drum at theother end ; the upper axle has at one end a drum made of rundles, and atthe other end, a drum to which are fixed iron clamps, in which the links of achain catch in the same way as before, and from the same depth, draw waterthrough pipes by means of balls. This revolving machine is turned by twopairs of men alternately, for one pair stands working while the other sitstaking a rest ; while they are engaged upon the task of turning, one pullsthe crank and the other pushes, and the drums help to make the pump turnmore easily.

The sixth pump of this kind likewise has two axles. At one end of thelower axle is a wheel which is turned by two men treading, this is twenty-three feet high and four feet wide, so that one man may stand alongsidethe other. At the other end of this axle is a toothed wheel. The upper 19axle has two drums and one wheel; the first drum is made of rundles, and tothe other there are fixed the iron clamps. The wheel is like the one on thesecond machine which is chiefly used for drawing earth and broken rockout of shafts. The treaders, to prevent themselves from falling, grasp intheir hands poles which are fixed to the inner sides of the wheel. Whenthey turn this wheel, the toothed drum being made to revolve, sets in motionthe other drum which is made of rundles, by which means again the linksof the chain catch to the cleats of the third drum and draw water throughpipes by means of balls,—from a depth of sixty-six feet.

But the largest machine of all those which draw water is the one whichfollows. First of all a reservoir is made in a timbered chamber ; this reser-voir is eighteen feet long and twelve feet wide and high. Into this reservoira stream is diverted through a water-race or through the tunnel; it has twoentrances and the same number of gates. Levers are fixed to the upper partof these gates, by which they can be raised and let down again, so that by oneway the gates are opened and in the other way closed. Beneath the openingsare two plank troughs which carry the water flowing from the reservoir, andpour it on to the buckets of the water-wheel, the impact of which turns thewheel. The shorter trough carries the water, which strikes the bucketsthat turn the wheel toward the reservoir, and the longer trough carriesthe water which strikes those buckets that turn the wheel in the oppositedirection. The casing or covering of the wheel is made of joined boards towhich strips are affixed on the inner side. The wheel itself is thirty-six feetin diameter, and is mortised to an axle, and it has, as I have already said,two rows of buckets, of which one is set the opposite way to the other, sothat the wheel may be turned toward the reservoir or in the opposite

19 In the original text this is given as “ lower,” and appears to be an erroi.