Mezzotint by Charles Turner, 1815, after an original painting by Sir Thomas Lawrence, c 1800. James Watt (1736-1819) invented the modern steam engine, which became the main source of power in textile mills in Britain during the Industrial Revolution. His engine had a separate condenser through which steam from the cylinder was pased and cooled, allowing the engine to remain hot, thus reducing fuel consumption. The SI (international standard) unit of power, the watt (W), is named after him. Dimensions overall: 185mm x 140mm.
© Science Museum / Science & Society Picture Library