If the pump should make a longer stroke on one end than on the other, simply lengthen or shorten the rocker connection so that the rocker bar, H, will touch the rocker roller, I, equally distant from the center pin, J. In case the pump hesitates in making its return stroke, it is because the rocker roller, I, is too low and does not come in contact with the rocker bar, H, soon enough. To raise it, take out the rocker roller stud, K, give the set screw in this stud a sufficient downward turn, and the stud with its roller may at once be raised to its proper height. [Illustration: FIG. 278.] When the valve rod has a tendency to tremble, slightly tighten the valve rod stuffing-box nut. When the valve motion is properly adjusted, the vertical arm should not quite touch the collar, L, and the clamp, M. Rocker roller, I, coming in contact with the rocker bar, H, reverses the stroke. The water piston is packed by means of segments that will be seen by taking off the follower. The packing may be quickly set out to insure a good vacuum and at the same time not to be so tight as to bind. All wearing parts are made adjustable. THE MOORE. The valve for admitting steam to and exhausting it from the cylinder of this pump is contained within the cylinder and moves simultaneously with the steam piston, having no outside mechanism. See Fig. 278. The piston, and also the valve, are of the form of spools, each representing a hollow sleeve with a ring packed piston head at either end. The piston is secured to the piston rod and the sleeve connecting the two heads serves as the valve seat for the cylindrical valve. The sleeve of the piston contains two longitudinal ports, one port communicating with one end of the cylinder, and the other port communicating with the opposite end. Suitable holes drilled through the walls of the sleeve and communicating with the longitudinal ports, act as admission and exhaust ports, with which the holes and cavities in the sleeve coincide at proper positions in the stroke. Referring to the accompanying engraving, Fig. 279, which represents the valve and piston in the position occupied when ready to commence a stroke from left to right, the reader will easily understand the action of these parts. When the piston reaches the end of the stroke steam enters through the steam pipe at A, between the pistons, and forces the valve to the left as shown. This movement opens the port, B, and also brings the cavity, C, in communication with port, D, steam being admitted through ports, B and D, into the longitudinal port, F, thence into the clearance, G, of the cylinder. This causes the piston to move toward the right. When the piston has moved a short distance to the right steam is admitted into the space, H, surrounding the valve, and passing into the cavity, C, and through the port, D, furnishes steam to complete the stroke.