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BOOK VI. 



again turns the toothed wheel of the upper small axle and thus the drum to 

 which the clamps are fixed. In this way the chain, together with the empty 

 dippers, is slowly let down, close to the footwall side of the vein, into the sump 

 to the bottom of the balance drum, which turns on a Uttle iron axle, both ends 

 of which are set in a thick iron bearing. The chain is rolled round the drum 

 and the dippers fill with water ; the chain being drawn up close to the hanging- 

 wall side, carries the dippers filled with water above the drum of the upper 

 axle. Thus there are always three of the dippers inverted and pouring 

 water into a lip, from which it flows away into the drain of the tunnel. This 

 machine is less useful, because it cannot be constructed without great expense, 

 and it carries off but httle water and is somewhat slow, as also are other 

 machines which possess a great number of drums. 



A — Wheel which is turned by treading. B — Axle. C — Double chain. D^I.ink 



OF DOUBLE CHAIN. E — DiPPERS. F — SIMPLE CLAMPS. G — ClAMP WITH TRIPLE CURVES. 



The next machine of this kind, described in a few words by Vitruvius,^* 

 more rapidly brings up dippers, holding a congius ; for this reason, it is 



'*Vitruvius (x., 9). " But if the water is to be supplied to still higher places, a double 

 " chain of iron is made to revolve on the axis of the wheel, long enough to reach to the lower 

 " level. This is furnished with brazen buckets, each holding about a congius. Then by turning 

 " the wheel, the chain also turns upon the axis and brings the buckets to the top thereof, on 

 " passing which they are inverted and pour into the conduits the water they have raised." 



