441 PHILOSOPHICAL TRANSACTIONS. [aNNO 1731. 



the end of which, at c, 1, 2, 3, 4, are jointed 4 rods with their forcing plugs, 

 working into d 1, 2, 3, 4, A cylinders of cast iron 4f feet long, 7 inches bore 

 above, and g below, where the valves lie, fastened by screwed flanches, over 

 the 4 holes of a hollow trnnk of cast iron, having 4 valves in it just over eeee, 

 at the joining on of the bottom of the barrels, or cylinders; and at one end a 

 sacking pipe and grate f, going into the water, which supplies all the 4 cy- 

 linders alternately. 



From the lower part of the cylinders d 1, d2, d3, d4, come out necks 

 turning upward archwise, as gggg, whose upper parts are cast with flanches to 

 screw up to the trunk hhhh; which necks have bores 7 inches in diameter, and 

 holes in the trunk above, communicating with them, at which joining are 

 placed 4 valves. The trunk is cast with 4 bosses, or protuberances, standing 

 out against the valves, to give room for their opening and shutting; and on 

 the upper side are 4 holes stopped with plugs, to take out on occasion, to 

 cleanse the valves. One end of this trunk is stopped by a plug i; to the other, 

 iron pipes are joined, as i 2 by flanches, through which the water is forced up 

 to any height, or place required. 



Besides these 4 forcers, there are 4 more, placed at the other ends of the 

 librae, or levers (not shown in the fig. to avoid confusion, but to be seen on 

 the left hand) the rods being fixed at a 1, 2, 3, 4, working in 4 such cylinders, 

 with their parts dd, &c. ee, f, gg, and i, as before described, standing near kk. 



At the other end of the wheel at b, is placed all the same sort of work, as 

 is described at the end a, viz. 



The cog-wheel i The 4 levers ac, ac, &c. 



The trundle k 8 forcing rods ad, ad, &c. 



The spindle x 8 cylinders de, de, &c. 



The crank y, z 4 trunks, as ee, hh, &c. 



The sucking pipes f 1 forcing pipes, as i. 



So that one single wheel works 16 pumps. All which work could not be 

 drawn in one perspective view, without rendering it very much confused. 



The following is a calculation of the quantity of water raised by the engine 

 at London -bridge. 



In the first arch next the city is one wheel, with double work of 16 forcers. 



C first wheel double work at one end, ? ^ 



I .i_ lU- I 1 ; aud single at the other C 



In the third arch < j 1 1 ■ .t • ui o 



j second wheel in the middle 8 



(. third wheel 16 



In all 52 forcers 



One revolution of a wheel makes in every forcer 2^ strokes i ' 



So that one turn of the 4 wheels makes 114 strokes 



