Chap. XVII.

ON PUMPS.

Suppose A, fig.

1840., to be a weightof 200lbs. suspendedto an axle traversedby an iron bar whichcarries two pis-ton-rods. A manpressing with hisfoot on the treadle __

E would workboth pistons, forwhen making aneffort of only GOpounds, the leverbeing 4 feet long,and the rods sus-pended to the centreof the axle, theweight may be fourtimes the power;consequently, if wesuppose the pistons2 inches in diameter,they will force acolumn of water 154feet in height.

Pig. 1841. represents suctionand forcing pumps worked byone or two men at a winch A,on whose axle is a fly wheeland a pinion which engagestwo wheels C and D, to whoseaxles two lesser, E and F, areattached, having teeth on onlyhalf their circumference: when thewinch is put in motion, it turnsthe pinion B, and consequentlythe wheels C and D; in likemanner the two others E andF, which engage alternately inthe racks G and II attached tothe piston rods, one of whichforces the water into the discharg-ing pipe O, while the otherraises it above the lower valve.The teeth of the small wheelsbeing turned in opposite di-rections, the first E raises therod G to the last tooth, afterwhich the weight I causes it todescend, forcing the water to aheight proportionate to the sizeof the pump-barrel and the weightof I, which should be greater thanthat of the column of water. Onthe other hand when G ascendsand the piston sucks, the teeth ofthe other wheel, F, engage therack II, making it descend to thelast tooth; the piston N by theaction of the moving power thenforces the water up the pipe O ;when the last tooth is past, therod II is drawn up by the weightK, which must be rather abovethat of the column of water andthe piston and rod. The two rods

Fig 1840.

Pig. 1M1.

4 G 3