James Watt (Greenock, 1736 – Birmingham, 1819), an instrument maker at the University of Glasgow, conceives in 1765 the separate condenser — an independent vessel where steam condenses without cooling the cylinder — while repairing a Newcomen model. The patent is granted in 1769. In 1782 he adds double-acting motion (steam acting on both piston strokes), multiplying power. The Boulton & Watt company (1775) manufactures and sells the engines at industrial scale. Watt introduces the concept of "horsepower" (hp) to communicate performance to non-technical customers. The Watt engine's efficiency triples that of Newcomen's. His contribution is not inventing the steam engine — Newcomen already had a practical one — but making it efficient enough for applications beyond mine pumping: textile manufacturing, paper, foundries, transport.