All About Engines

204 All About Engines side to admit water from the well into which it is built, and which is supplied with water from the River Lea. The right-hand limb is open and has a discharge pipe through which water flows into the reservoir. The mode of operation is as follows: A mixture of gas and air is exploded above the surface of the water in the cylinder, the water being driven for- ward along the play pipe and up into the right- hand limb. When once a large body of water is set in motion it does not stop readily, so it does not cease when the pressure in the cylinder has fallen below that of the atmosphere. Water pours out of the discharge pipe into the reservoir, and fresh water enters from the well through the valve in the side of the cylinder. Gradually the forward motion in the play pipe ceases, and the water begins to return. Swinging back with increasing and then decreasing velocity, it sweeps out through the exhaust valve the waste gases from the explosion, and then begins to flow forward again towards the reservoir. During this stroke gas and air are admitted to the cylinder, the water flows back and compresses them, an explosion occurs, and the whole cycle of operations is repeated. While the pump is at work no attention is re- quired. There are no rubbing surfaces to be lubri- cated, the valves are self-acting, held down on their seats by springs, and locked when not in use by the action of a small water motor. Unlike the ordinary gas engine, all the strokes in a cycle are not of the same length. They have different duties to per- form and are made under different conditions. So