_To set the valve._ Set the lever, A, plumb and the valve to cover all the ports equally. THE DEAN BROS. PUMP. The Dean Bros. pump is shown in Figs. 295, 296 and 297. [Illustration: FIG. 295.] The auxiliary valve, A, Fig. 297, has in its face two diagonal exhaust cavities, B B_{1}. The ports, C C_{1}, and the exhaust port, D, are placed in a triangular position with one another, the diagonal cavities diverging so that the cavity B, when the valve is in place, connects the ports, C_{1} and D. Cavity B_{1} connects the ports C and D, when the valve, A, is at the end of the stroke. The three small cuts show relation of auxiliary valve to ports. [Illustration: FIG. 296.] The piston starts from left to right when the valve, A, moves in an opposite direction, opens the port, C, admitting steam to the auxiliary cylinder at the moment the main piston has reached the end of its stroke. The auxiliary piston, E, is forced to the left, opening the main port and admitting steam to the main cylinder, reversing the movement of the main piston the return stroke of the main piston reverses the movement of the auxiliary valve, whereby the port, C, is closed, at the moment the main piston reaches the end of its outer stroke. The port, C_{1}, is opened by the valve, A, and reverses the valve piston, E, opens the main port and reverses the motion of the main piston. [Illustration: FIG. 297.] This port arrangement admits of a short valve with a long travel. The stroke of the pump can be regulated by moving the stud up or down in the segmental slot, Fig. 296, which varies the travel of the auxiliary valve and reverses the stroke of the main piston as desired. By raising the stud the pump will make shorter strokes, and by lowering it will make longer strokes. The motion of the auxiliary steam slide valve is like that derived from an eccentric. The ports leading to the valve piston, E, Fig. 297, remain closed, except at the moment the main piston is reversed; hence, there can be no waste of steam from leaks when the valve piston becomes worn. Having a long stroke and a rapid motion, the auxiliary valve insures a certain reversal of the piston at the proper time. _To set the valve_, turn the steam chest upside down. Put valve stem through the stuffing-box and secure in place the clamp for small slide valve. The diameter of valve stem is smaller where the clamp is attached.