NEWCOMEN’S ATMOSPHERIC ENGINE
The first practical use of steam power was applied to the pumping of water from the deep mines of Cornwall. Newcomen’s engine, which antedated Watt’s by several decades, was known as an atmospheric engine. It consisted of a cylinder fitted with a piston, but the top of the cylinder was open. The piston was connected to one end of a lever or walking beam, the other end of which was connected by a chain with the plunger of a pump situated at the bottom of the mine shaft. Little power was required to lift the piston because it was counterbalanced by the chain and plunger attached to the opposite end of the walking beam. The real work was done in pushing the piston down and thereby raising the pump plunger. Steam under low pressure was let into the cylinder under the piston to raise it and then a jet of water was sprayed into the steam-filled cylinder. This condensed the steam, producing vacuum and the atmospheric pressure acting on the upper surface of the piston forced the piston down, raising the pump plunger. The engine ran very slowly, making only about 15 strokes per minute. Later it was improved, producing about 30 strokes per minute.