James Watt

James Watt

Watt was born on January 19, 1736, in Greenock, Scotland. He worked as a mathematical-instrument maker from the age of 19 and soon became interested in improving the steam engines, invented by the engineers Thomas Savery and Thomas Newcomen, which were used at the time to pump water from mines. Watt 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. Watt's 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.

At this time, Watt was the partner of the inventor John Roebuck, who had financed his researches. In 1775, however, Roebuck's interest was taken over by the manufacturer Matthew Boulton, owner of the Soho Engineering Works at Birmingham, and he and Watt began the manufacture of steam engines. Watt continued his research and patented several other important inventions, including the rotary engine for driving various types of machinery; 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. He retired from the firm in 1800 and thereafter devoted himself entirely to research work.

In an engine designed by English inventor Thomas Newcomen in 1705, steam admitted to the bottom of a vertical cylinder at very low pressure moved a counterweighted piston to the top of the cylinder. At this point, a valve opened and sprayed a jet of cold water into the cylinder. The water condensed the steam, and atmospheric pressure forced the piston back to the bottom of the cylinder. While making improvements to the New common engine, Scottish scientist James Watt designed an engine that had a separate condensing chamber for the steam. This engine, patented in 1769, greatly increased the economy of the new common machine by avoiding the loss of steam that occurred in alternate heating and cooling of the engine cylinder.

The misconception that Watt was the actual inventor of the steam engine arose from the fundamental nature of his contributions to its development. The centrifugal or flyball governor, which he invented in 1788, and which automatically regulated the speed of an engine, is of particular interest today.