The son of a Clydeside shipbuilder, 1736-1819, Watt began work as a mathematical instrument maker in Glasgow at the age of 17. Shortly afterwards he opened his own shop and as a result met many of the local scientists and engineers.
In 1764, while repairing a Newcomen steam engine. Watt became aware of the ineffieiences associated with the need to cool and condense the vapor at each stroke (see Steam Engines). He realized that the solution was to build an engine with a separate external condenser but he did not bring this concept to fruition until 1790. The Watt engine, built in partnership with Mathew Boulton, made a major contribution to the industrial revolution.
Watt produced other novel engines for pumping water from mines and for driving mill machinery. These employed new forms of gearing and control mechanisms, including the centrifugal governor which he invented in 1788, His business was very successful and he retired a rich man.
Watt was the first to use the term "horsepower", a unit of engine power that has been the standard for two hundred years. It is appropriate that the modern unit of power, the Watt, should take his name.