James Watt (19.01. 1736-19.08.1819) —a Scottish inventor, the creator of the universal steam engine, Fellow of the Royal Society of Edinburgh (1784). Born in Greenock. From 1756 he worked as a mechanic at the University of Glasgow, and after 1765 was occupied with improving the steam engine.
He studied the properties of water vapour, in particular the dependence of the temperature of saturated vapour on pressure. A detailed study of Newcomen's steam engine led him to introduce many improvements in it. He invented the condenser — the third main element of a heat engine (1765), the centrifugal governor for the admission of steam, the slide valve, the steam jacket around the cylinder, the double-acting cylinder, and the mechanism for transmitting motion from the piston to the beam (Watt's parallelogram), and put forward the idea of using the expansion of steam in the cylinder (1782). Thanks to these improvements there was created (1784) the universal double-acting steam engine with continuous rotation (the Watt steam engine), economical and efficient, which came into wide use and played a great part in the transition to machine production (the first single-acting steam engine was built by Watt in 1774). He introduced the first unit of power — the horsepower. He also designed a number of instruments: an open mercury manometer, a mercury vacuum gauge for the condenser, the water gauge glass for boilers, and the pressure indicator. He invented copying ink (1780) and established the composition of water (1781).
Fellow of the Royal Society (1785), member of the Paris Academy of Sciences (1814). The unit of power, the watt, is named after him.