This magnificent engine was patented in 1705 by Thomas Newcomen, and is generally regarded as the first 'modern' steam engine. Unlike later steam engines, the Newcomen works on the atmospheric principle. The Newcomen was first used to pump water from mines in England. The pump rod at left is coupled to the driving piston by a large rocking beam.
Water is boiled continuously to produce steam.
At the top of the stroke the steam valve is closed and a water jet is briefly turned on, cooling the steam in the cylinder. The cool steam contracts, sucking the piston downward. At the end of the stroke, the cooling water is drained from the cylinder by an extra passage not illustrated here. During the upward stroke, an auxiliary pump fills the cooling water reservoir. Newcomen engines were successful in part because they were very safe to operate.