Watt, James, inventor of the modern steam-engine, born in Greenock, son of a merchant; began life as a mathematical-instrument maker, opened business in Glasgow under university patronage, and early began to experiment on the mechanical capabilities of steam; when in 1703, while engaged in repairing the model of a Newcomen's engine, he hit upon the idea which has immortalised his name. This was the idea of a separate condenser for the steam, and from that moment the power of steam in the civilisation of the world was assured; the advantages of the invention were soon put to the proof and established, and by a partnership on the part of Watts with Matthew Boulton (q.v.) Watt had the satisfaction of seeing his idea fairly launched and of reaping of the fruits. Prior to Watt's invention the steam-engine was of little other use than for pumping water (1736‒1819).
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Watson, William * Watteau, Antoine