Watt, James. An eminent British engineer and mechanical inventor. Born at Greenock in 1736. Watt early developed extraordinary talents in practical mechanics and, in 1765, perfected his grand discovery of the condensation of steam by means of an air-tight cylinder, and likewise invented an apparatus to depress the piston of an engine by steam instead of atmospheric pressure. For some years Watt occupied himself in the surveying and engineering of public works in Scotland and, in 1774, entered into partnership with the Messrs. Boulton of Soho, Birmingham, for the manufacture of steam engines, perfecting numerous and great improvements in their mechanism - among others, the regulator by centrifugal force, the throttle valve, the machinery of parallel motion, and the steam barometer. In 1782 Watt invented the double-acting engine, and retired from business in 1800. James Watt died in 1819.