James Watt, the son of a merchant, inventor and mechanical engineer, is renowned for his improvements of the steam engine.

He was born on January 19, 1736, in Greenock and worked as a mathematical-instrument maker from the age of nineteen. His interest turned to improving the steam engines, invented by the English engineers Thomas Savery and Thomas Newcomen.

James determined the properties of steam, especially the relation of its density to its temperature and pressure, and designed a separate condensing chamber for the steam engine that prevented enormous losses of steam in the cylinder and enhanced the vacuum conditions.

His first patent in 1769 covered this device and other improvements on Newcomen’s engine, such as steam-jacketing, oil lubrication, and insulation of the cylinder, in order to maintain the high temperatures necessary for maximum efficiency.

He continued his research and patented several other important inventions, including the rotary engine for driving various types of machinery, including the double-action engine, in which steam is admitted alternately into both ends of the cylinder and the steam indicator, which records the steam pressure in the engine. James continued to experiment and in 1781 he produced a rotary-motion steam engine.

The misconception that Watt was the actual inventor of the steam engine arose from the fundamental nature of his contributions to its development. James coined the term horsepower to compare the power output of steam engines, his version of the unit being equivalent to 550 foot-pounds per second (approx. 745.7 watts).

Watt also invented several other things, not least a copying device for letters.

He died on August 19, 1819 in Heathfield, England.

This is the James Watt Cairn located in the Greenock cemetery as a tribute to this great man. The stones used were gathered from all over the world.

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