BOOK VI. 



175 



more useful than the first one for drawing water out of shafts, into which 

 much water is continually flowing. This machine has no iron frame nor 

 drums, but has around its axle a wooden wheel which is turned by treading ; 

 the axle, since it has no drum, docs not last very long. In other respects 

 this pump resembles the first kind, except that it differs from it by having 

 a double chain. Clamps should be fixed to the axle of this machine, just as 

 to the drum of the other one ; some of these are made simple and others 

 with triple curves, but each kind has four barbs. 



The third machine, which far excels the two just described, is made 

 when a running stream can be diverted to a mine ; the impetus of the 

 stream striking the paddles revolves a water-wheel in place of the wheel 

 turned by treading. With regard to the axle, it is like the second machine. 



A — Wheel whose paddles are turned by the force of the stream. 

 C — Drum of axle, to which clamps are fixed. D — Chain. E — Link. F- 

 G — Balance drum. 



Axle. 

 Dippers. 



but the drum which is round the axle, the chain, and the balance drum, are 

 like the first machine. It has much more capacious dippers than even the 

 second machine, but since the dippers are frequently broken, miners rarely 

 use these machines ; for they prefer to lift out small quantities of water by 

 the first five machines or to draw it up by suction pumps, or, if there is 



