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Thomas Newcomen (1663-1729). Thomas Newcomen was an English blacksmith of Dartmouth, Devon. He invented the atmospheric steam engine, which was an improvement on Slavery's engine. Newcomen's engine pumped steam into a cylinder. The steam was then condensed by cold water which created a vacuum on the inside of the cylinder. The resulting atmospheric pressure operated a piston, creating downward strokes. In Newcomen's engine the intensity of pressure was not limited by the pressure of the steam, unlike what Thomas Savery had patented in 1698. In 1712, Newcomen together with John Calley built their first engine on top of a water filled mine shaft and used it to pump water out of the mine. Even though Newcomen’s work was very important, he remains a little known individual, with no known portrait available anywhere in the world. 65 years later Watt came up with an improvement to the Newcomen’s engine. In addition to the first cylinder a second cylinder was added, a condenser, allowed the main cylinder to run at a reasonably hot temperature without cooling off and pre-condensing the steam. This was the main problem with Newcomen's engine as the water sprayed into the cylinder to condense the steam also cooled the cylinder. Efficiency of subsequent strokes was hence reduced. Steam from the hot main cylinder in Watt's engine is sucked into the condenser cylinder where it condenses into water forming a vacuum in the main cylinder. The other problem with Newcomen's engine was the quality of the main cylinder. Being cast, the inner surface was rough so it was difficult to obtain a good piston-to-cylinder seal. Watt used bored cylinders (a technique used to make cannon barrels) which sealed better and so produced better vacuums.

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