James Watt

James Watt was born in Greenock, Scotland, the son of a shipwright and merchant. Often in poor health as a child, he was taught much at home and loved making models in his father's workshop. He trained as a maker of mathematical instruments in London and then worked at the University of Glasgow. In 1764 he was asked to repair a model of a Newcomen steam engine, the kind used to pump water from mines, and noticed how much fuel it wasted by heating and cooling the same cylinder. In 1765, on a Sunday walk, he hit on the idea of a separate condenser, which made the engine far more efficient. Developing it took years. In 1775 he went into partnership with the Birmingham manufacturer Matthew Boulton, and their firm built engines for mines, mills and factories. Watt added a way to turn the engine's motion into rotation, a governor to control its speed, and a gauge for measuring power, and coined the term horsepower. The unit of power, the watt, is named for him. He died in 1819.

Faith: Raised by Presbyterian Covenanter parents; he later became a deist. Source: Wikipedia