The Nuttall Encyclopedia
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).
Wood, James, ed. Entry for 'Watt, James'. The Nuttall Encyclopedia. https://www.studylight.org/encyclopedias/eng/nut/w/watt-james.html. Frederick Warne & Co Ltd. London. 1900.