Watt, James

(1736–1819) British instrument maker and engineer: invented the modern steam engine.

The son of a Clydeside shipbuilder, Watt had little formal education because of his poor health, but his skills enabled him to set up in business as an instrument maker in the University of Glasgow. While repairing a working model of a Newcomen steam engine, Watt realized that its efficiency could be greatly improved by adding a separate condenser, preventing the loss of energy through steam condensing to water in the cylinder. He formed a business partnership with M Boulton (1728–1809) in Birmingham to develop the idea, improved the engine in several other ways, and in 1790 produced the Watt engine, which became crucial to the success of the industrial revolution. Soon it was being used to pump water out of mines and to power machinery in flour, cotton and paper mills. Watt retired, a very rich man, in 1800. The SI unit of power, the watt, is named after him: it is the power producing energy at the rate of 1 J s –1 .

Watt also invented (in 1779) the first office copying process: he used a gelatinous ink, from which a copy was obtained by pressing damp unsized copy paper on the original. The copy was viewed in a mirror.