James Watt, the celebrated improver of the steam-engine, was born at Greenock, January 19, 1736; and died at his seat of Heathfield, Staffordshire, August 25, 1819. His father was a merchant and magistrate of Greenock, and James received a good education in its public schools. Having determined to adopt the trade of mathematical-instrument maker, he went to London (1754) to learn the art, but ill-health compelled him to return after only a year's apprenticeship. Shortly after his return he endeavoured to establish himself in Glasgow. The corporation objecting, he was appointed in 1757 mathematical-instrument maker to the university, and resided within its walls till 1763, when he removed into the town. It was May 1765 when Watt thought of the idea of a separate condenser, into which the steam could be drawn by means of an air-pump, but it was 1776 before his first two engines began work. One of these was to built to supply air to the blast furnaces of John Wilkinson's ironworks at Denbighshire in Wales. In return, Wilkinson bored cylinders for Watt's engines on his recently invented boring-mill.

Without the precision of Wilkinson's cylinders, Watt's engines could never have succeeded, requiring as they did airtight operation at high working temperatures. Watt naturally moved on to using rotary motion to power other machinery.

From this time till 1774 he acted as a civil engineer - made several surveys for canals and harbours, and some of his plans were afterwards carried into execution. It was during this period that he conceived and gave shape to his improvements on the steam-engine, which have rendered his name famous.

To give his inventions practical form he associated himself in 1774 with Mathew Boulton, the firm of Boulton and Watt having their works at Soho, Birmingham. He retired from business in 1800. Watt was a fellow of the Royal Societies of London and Edinburgh, and member of the National Institute of France. He was twice married, and was survived by one son, who carded on the establishment at Soho in partnership with a son of Mr. Boulton's. Besides improving the steam-engine, Watt invented or improved a variety of mechanical appliances, including a letter-copying press. He was a man of high mental powers generally, and possessed a wide and varied knowledge of literature and science.