Building a Newcomen Atmospheric Engine — The First Engine to Do Real Work

In 1712 Thomas Newcomen built a machine that changed the world quietly, by pumping water out of coal mines. It was the first engine to turn the heat of a fire into useful mechanical work on a large scale, and every steam engine and motor that followed descends from it.

Its genius is counter-intuitive: the steam does not push the piston. Newcomen's engine fills a cylinder with low-pressure steam, then sprays in cold water to condense that steam into a few drops, leaving a vacuum. The ordinary pressure of the atmosphere — about a tonne on a large piston — then shoves the piston down into the vacuum. That downward stroke rocks a great wooden beam whose far end lifts the mine pump. Because air pressure does the work, it is called an atmospheric engine.

It was thirsty and wasteful, reheating its whole cylinder every stroke, but it was tireless and it worked. For sixty years Newcomen engines drained the mines that supplied the coal that fed the Industrial Revolution — until James Watt's separate condenser made the steam engine efficient enough to drive factories and locomotives.