Denis Papin Quote

Turning a small surface of water into vapour by fire, applied to the bottom of the cylinder that contains it; which vapour forces up the plug (or piston) in the cylinder to a considerable height, and which, as the vapour condenses, (as the water cools when taken from the fire,) descends again by air's pressure, and is applied to raise water out of the mine.

Denis Papin, Letter, as quoted by Robert Stuart Meikleham, A Descriptive History of the Steam Engine (1824)