From Wikipedia:

James Watt was a Scottish inventor, mechanical engineer, and chemist whose Watt steam engine, an improvement of the Newcomen steam engine, was fundamental to the changes brought by the Industrial Revolution in both his native Great Britain and the rest of the world.

While working as an instrument maker at the University of Glasgow, Watt became interested in the technology of steam engines. He realized that contemporary engine designs wasted a great deal of energy by repeatedly cooling and reheating the cylinder. Watt introduced a design enhancement, the separate condenser, which avoided this waste of energy and radically improved the power, efficiency, and cost-effectiveness of steam engines. Eventually he adapted his engine to produce rotary motion, greatly broadening its use beyond pumping water.
Watt attempted to commercialize his invention, but experienced great financial difficulties until he entered a partnership with Matthew Boulton in 1775. The new firm of Boulton and Watt was eventually highly successful and Watt became a wealthy man. In his retirement, Watt continued to develop new inventions though none was as significant as his steam engine work. He died in 1819 at the age of 83.

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James Watt is the reason the industrial Revolution started in Britian