Of the first class, the common single-acting house-pumps shown in Figs. 157 and 158 are examples; the pumps are simply modifications of the suction-pump; a common form of lift-pump has a pitman-rod which pushes the water up instead of lifting it through a spout at or near the top of the cylinder. The details of the suction-pump are as follows—at the bottom of the cylinder is a pipe communicating with the liquid to be raised, and a valve which opens from beneath. A similar valve is placed in the piston. A force-pump is shown in Fig. 159; from the two figures the difference between the lift and the force-pump may be understood; while the former raises the liquid above its piston from which it flows under no pressure, the latter forces it out of the barrel under a varying pressure which depends upon circumstances. When the piston rises the suction valve opens, and the valve in the piston closes by the air-pressure. The liquid then enters the barrel beneath the piston. On the descending stroke the suction valve closes, and the liquid flows upward into the discharge pipe. [Illustration: FIG. 159.] _In Fig. 160 is shown an air-chamber_ attached to a force-pump for the purpose of preventing shocks in the discharge, and for producing a steady flow; air-chambers are also frequently attached to suction pipes for a similar purpose. According to the underlying principles of action thus far explained hundreds of thousands of pumps have been constructed and operated. It is beyond the limits of this volume—or any single book to give the names and details of these so-called “hand-pumps,” however, three approved styles are shown in Figs. 161, 162, 163. Fig. 161 represents a _double acting force pump_ used extensively on ship-board, wharves, around factories, mills, etc., and in residences, for tank pumping. On ships these pumps perform the three-fold purpose of filling boilers when cold, washing down decks and to satisfy government inspection as to fire protection; in service in mines they are unaffected by mine water, the working parts being made non-corrosive. It is claimed that a three-inch diameter cylinder with a stroke of four and a half inches with a 1-1/4-inch suction pipe and 1-inch discharge pipe will lift and force water 150 ft. high and has a capacity of ·28 gallons for each stroke, with the water not more than twenty-five feet below the pump. [Illustration: FIG. 160.] Fig. 162 represents _a two cylinder force pump_; this has vertical single acting pistons actuated by one lever, producing the same results as a double-acting pump. It is claimed that the total lift and force, from supply to point of delivery, with the pump not more than twenty-five feet above water will attain one hundred feet; that a 3-inch × 4 inch cylinder, 1-1/2-inch suction and 1-1/4-inch discharge will deliver ·24 gallons of water for each stroke.