OF HYDRAULIC ENGINES. 137 



water-wheel, A A, upon its axis, to turn a trundle up- LECT. 

 on each side ; the cranks being upon the axis of the v^^-^ 

 trundle. And by proportioning the cog-wheels to the 

 trundles, the motion of the pumps may be made quicker, 

 according to the quantity and strength of the water 

 upon the first wheel ; which may be as great as the work- 

 man pleases ; according to the length and breadth of the 

 float-boards or wings of the wheel. In this manner, the 

 engine for raising water at London-Bridge was construct- 

 ed ; in which, the water-wheel being 20 feet diameter, 

 and the floats 14 feet long. 



Where a stream or fall of water cannot be had, and A pump- 

 gentlemen want to have water raised, and brought to go byhoi" 

 their houses from a rivulet or spring : this may be 8e9- 

 effected by a horse-engine, working three forcing-pumps 

 which stand in a reservoir filled by the spring or rivu- 

 let : the pistons being moved up and down in the pumps 

 by means of a triple crank ABC, (Plate ID.) which, as it 

 is turned round by the trundle G, raises and depresses the 

 rods D,E,F. The trundle maybe turned by such a wheel 

 as F in Plate II. having levers y, y, y, y, on its upright 

 axle, to which horses may be joined for working the 

 engine. And if the wheel has three times as many cogs 

 as the trundle has staves or rounds, the trundle and 

 cranks will make three revolutions for every one of the 

 wheel : and as each crank will fetch a stroke in the time 

 it goes round, the three cranks will make nine strokes 

 for every turn of the great wheel. 



The cranks should be made of cast iron, because that 

 will not bend ; and they should each make an angle of 

 120 with both of the others, as at a,b,c, which is (as it 

 were) a view of their radii, in looking endwise at the 

 axis : and then there will be always one or other of them 

 going downward, which will push the water forward with 

 a continued stream into the main pipe. For, when 6 

 is almost at its lowest situation, and is therefore just be- 

 ginning to lose its action upon the piston which it 



