The unprecedented innovation of the steam-atmospheric engine by Thomas Newcomen (1663-1729) of Dartmouth and his assistant John Calley stands at the beginning of the development of practical thermal prime movers in the early years of the eighteenth century. Spreading through Europe and then to the Cornwall mines in the New World, it was one of the strategic innovations in world history and the single greatest act of synthesis in the ensuing history of the steam engine.

This engine represents the Newcomen line of engines, also known as "fire engines," which employed a vacuum created by condensing steam from a pressure just above atmospheric. The small 22-inch diameter cylinder engine, whose early history is unknown but dated before 1800, is a direct descendant of Newcomen's first machine.