HOW EXHAUST LEAD IS CONTROLLED.
The exhaust lead is controlled by the pin in the lap-and-lead lever, which is on the center, or horizontal, when the cross-head is at either end of the cylinder. The steam lead is controlled by the pin that is vertical, or above the center of the lap-and-lead lever, when the cross-head is at either end of the stroke. Both steam and exhaust lead are uniform at all points of cut-off. By this arrangement of the valve-gear and valves, steam can be cut off at any point of the stroke (by moving the sliding-block toward the center of the rocker-arm), and is retained, if desired, to the last inch of the stroke. In receiving, the steam is evenly distributed at all points of the cut-off.
There are about as many pieces to this gearing as to the ordinary link-gear; but it is considerably cheaper in construction, and much more durable; while it does away with two eccentrics, and their straps and connections.