HYDRAULICS. c 20i 



of delivering. The pit must be as deep in water 

 as from K to N O. A is a wooden trunk, round 

 or square, open at both ends, and having a valve, 

 P, at the bottom. The top of this trunk must be 

 in a level with K, and has a small cistern, F. It 

 also communicates laterally with a rising-pipe G, 

 furnished with a valve opening upwards. L is a 

 beam of timber, so fitted to the trunk, as to fill it 

 without sticking, and is of at least equal length. 

 It hangs by a chain from a working-beam, and is 

 loaded on the top with weights exceeding that of 

 the column of water which it displaces. 



Now, suppose this beam to descend from the 

 position in which it is drawn in the figure; the 

 water must rise all round it, in the crevice which 

 is between it and the trunk, and also in the rising- 

 pipe; because the valve P shuts and O opens; so 

 that when the plunger L has got to the bottom, 

 the water will stand at the level of K. When the 

 plunger is again drawn up to the top by the action 

 of the moving power, the water sinks again in the 

 trunk, but not in the rising-pipe, because it is 

 stopped by the valve O. Then allowing the 

 plunger to descend again, the water must again 

 rise in the trunk to the level of K, and it must 

 now flow out at K ; and the quantity discharged 

 will be equal to the part of the beam below the 

 surface of the pit-water, deducting the quantity 

 which fills the small space between the beam and 

 the trunk. This quantity may be reduced almost; 

 to nothing; for if the inside of the trunk, and the 

 outside of the beam, be made tapering, the beam 

 may be let down till they exactly fit; and as this 

 may be done in square work, a good workman may 

 make it exceedingly accurate. But, in this case* 

 the lower half of the beam, and trunk, must not 



