“I have now made an engine that shall not waste a particle of steam. It shall be boiling hot"
James Watt to his friend John Robison
Scottish engineer James Watt (1736-1819) was responsible for some of the most important advances in steam-engine technology. Steam engines had been in use since the 1710s, mainly to pump water from mines. These machines depended upon steam condensing inside a large cylinder after the cylinder was cooled with cold water. As the steam condensed, it took up less space, allowing atmospheric pressure to push down on a movable piston inside the cylinder.
In 1765 Watt made the first working model of his most important contribution to the development of steam power; he patented it in 1769. His innovation was an engine in which steam condensed outside the main cylinder in a separate condenser; the cylinder remained at working temperature at all times. Watt made several other technological improvements to increase The power and efficiency of his engines. For example, he realized that, within a closed cylinder, low-pressure steam could push the piston instead of atmospheric air. It took only a short mental leap for Watt to design a double-acting engine in which steam pushed the piston first one way, then the other, increasing efficiency still further.
Watt's influence in the history of steam-engine technology owes as much to his business partner, Matthew Boulton (1728-1809), as it does to his own ingenuity. The two men formed a partnership in 1775, and Boulton poured huge amounts of money into Watt's innovations. From 1781, Boulton and Watt began making and selling steam engines that produced rotary motion; all previous engines had been restricted to a vertical, pumping action. Rotary steam engines were soon the most common source of power for factories, becoming a major driving force behind Britain's Industrial Revolution.
