436 SUPPLEMENT. 



ing to the order of the letters, by the fall of water E F, 

 which need not be more than three feet. The axle G 

 of the wheel is elevated so, as to make an angle of 

 about 44 degrees with the horizon ; and on the top of 

 that axle is a wheel H, which turns such another wheel 

 / of the same number of teeth : the axle K of this last 

 wheel being parallel to the axle G of the two former 

 wheels. 



The axle G is cut into a double-threaded screw 

 exactly resembling the 

 screw on the axis of the 

 fly of a common jack, 

 which must be (what is 

 called) a right-handed 



screw, like the wood-screws, if the first wheel turns in 

 the direction ABCD; but must be a left-handed 

 screw, if the steam turns the wheel the contrary way. 

 And, which ever way the screw on the axle G be cut, 

 the screw on the axle K must be cut the contrary 

 way; because these axles turn in contrary direc- 

 tions. 



The screws being thus cut, they must be covered 

 close over with boards like those of a cylindrical cask ; 

 and then they will be spiral tubes. Or, they may be 

 made of tubes of stiff 

 leather,and wrapt round 

 the axles in shallow 

 grooves cut therein. 



The lower end of the axle G turns constantly in the 

 stream that turns the wheel, and the lower ends of the 

 spiral tubes are open into the water. So that, as the 

 wheel and axle are turned round, the water rises in the 

 spiral tubes, and runs out at L, through the holes M, 

 N, as they come about below the axle. These holes 

 (of which there may be any number, as four or six) are 

 in a broad close ring on the top of the axle, into 



