Should the piston stop at mid-stroke it will start again as soon as steam is turned on, because the port, D, remains open until the valve is reversed at the opposite end of the stroke. When the piston reaches the latter position, Fig. 280, the valve is reversed, due to steam entering at A, and again forcing the pistons apart, as shown. The steam, which drove the piston from left to right, now escapes through the port, I, into the cavity, J, and around the sleeve to the holes, K, Fig. 279, where it enters the hollow piston, and finally escapes through the hollow rod, L, and the port, M. The live steam for the next stroke from right to left, now enters through ports, N and O, Fig. 280, and flows through the longitudinal port, P, into the end, Q, of the cylinder. [Illustration: FIG. 279.] [Illustration: FIG. 280.] The exhaust steam may be allowed to flow into the atmosphere or into the suction chamber as desired. A valve is located in the base of the pump, which changes the course of the steam from the atmospheric discharge to the suction chamber. The valve is operated by a lever shown by dotted lines. When the lever is turned down toward the steam end, the steam is directed into the atmospheric exhaust, and when turned in the opposite direction the steam will enter the pump suction and be condensed. _There is no valve setting to be done on this pump._ Should the pump fail to work properly, due to the failure of the steam end, all that is necessary is to take out the valve and piston and clean them thoroughly and after replacing them and starting the pump to see that these parts are properly lubricated. The remainder of the pump requires the same care and attention that is, or should be, given all pumps. THE SNOW. The auxiliary valve of this pump is a plain flat slide operated by a valve stem, the latter being moved back and forth by means of a rocker shaft, as shown in the engraving, the upper end of which alternately comes in contact with the collars on the stem. The outer end of the valve stem passes through a sleeve attached to a pin in the upper end of the rocker arm, as shown. A knuckle joint near the stuffing-box permits the rod to vibrate without causing any derangement in the alignment of valve stem through the stuffing-boxes.