[Illustration: Figure 115.--The Farm Pump. It superseded the iron-bound bucket, the slimy old bucket, the malaria-lined bucket that hung in the well, but it wore out the women. Oil was never wasted on its creaking joints. Later it was fitted with a stuffing-box and an air-chamber, and the plunger was hitched to the windmill. To the right are shown two kinds of post-hole diggers. The upper digger is sometimes used to clear the fine earth out of the bottom of a hole dug by the lower digger.] _Suction-Pumps._--The word suction, when applied to pumps, is a misnomer. The principle upon which such pumps work is this: The pump piston drives the air out of the pump cylinder which produces a vacuum. The pressure of the atmosphere is about fifteen pounds per square inch of surface. This pressure forces sufficient water up through the so-called suction pipe to fill the vacuum in the cylinder. The water is held in the cylinder by foot-valves or clack-valves. As the piston again descends into the cylinder it plunges into water instead of air. A foot-valve in the bottom end of the hollow piston opens while going down and closes to hold and lift the water as the piston rises. Water from the well is forced by atmospheric pressure to follow the piston and the pump continues to lift water so long as the joints remain air-tight. The size of piston and length of stroke depend on the volume of water required, the height to which it must be lifted and the power available. A small power and a small cylinder will lift a small quantity of water to a considerable height. But increasing the volume of water requires a larger pump and a great increase in the power to operate it. The size of the delivery pipe has a good deal to do with the flow of water. When water is forced through a small pipe at considerable velocity, there is a good deal of friction. Often the amount of water delivered is reduced because the discharge pipe is too small. Doubling the diameter of a pipe increases its capacity four times. Square turns in the discharge pipe are obstructions; either the pipe must be larger or there will be a diminished flow of water. Some pump makers are particular to furnish easy round bends instead of the ordinary right-angled elbows. A great many pumps are working under unnecessary handicaps, simply because either the supply pipe or discharge pipe is not in proportion to the capacity of the pump, or the arrangement of the pipes is faulty. [Illustration: Figure 116.--Hand Force-Pump. Showing two ways of attaching wooden handles to hand force-pumps.] [Illustration: Figure 117.--Rotary Pump. Twin water-chamber rotary pumps take water through the bottom and divide the supply, carrying half of the stream around to the left and the other half to the right. The two streams meet and are discharged at the top.] [Illustration: Figure 118.--Section of Rotary Pump.]