Watt's rotative beam engine, 1788.
© Science Museum / Science & Society Picture Library
Sectioned view of cyclinder and valves. James Watt, (1736-1819), Scottish engineer and instrument maker, invented the modern steam engine which became the main source of power in the 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 be kept hot. This reduced fuel consumption and saved time.