The Steam Engine: A Revolutionary Power Source

A model of a beam engine featuring James Watt's parallel linkage for double action

Although various steam motion devices had been known since the time of Hero of Alexandria. This new invention would replace horses with horsepower.

When James Watt was born the horse was still the chief source of power for transportation and many other forms of work. In the 1750’s Watt became an instrument maker affiliated with the University at Glasgow. In this capacity he had a chance to work on a broken Newcomen engine. It fascinated him, but was too slow and cumbersome to have much practical use. By making a few innovations, over a period of years he made a steam engine that was a practical source of power and went down in history as the inventor of the steam engine. The real secret of his innovation was the concept of latent heat which was discovered by another, but which found practical application in Watt’s use of compressed steam to make the heating of water six times more efficient.

The Watt as a unit of power is named after him. He coined the term horsepower as a way to explain how much work his engine could do. James Watt’s steam engine was so good that it was used basically unmodified for nearly a century. It is a spur to the industrial revolution, and is the key to the transportation revolution. Horses and sails which had been used for thousands of years were virtually replaced almost overnight (historically speaking) by steam locomotives, steamboats, and steamships. Robert Fulton, an American, usually gets credit for building the first practical steamboat although a Frenchman, the Marquis de Jouffroy d’Abbans, actually built the first working steamboat in 1783, and Fulton’s was merely the first to run a regular commercial route. Irregardless of who gets the credit, new uses of the steam engine changed the world in the early 1800’s. D’Abbans working boat predates Fulton’s, but it had a tendency to break down often. Another American inventor also came in with an early design that used steam to force a jet of water out the back as a means of propulsion, but boats and trains powered by Watt’s engine proved to be the best.

Not only could goods and passengers travel with unprecedented speed, mail and news also traveled faster, and factories and mills could operate away from sources of water or wind power for the first time. Rivers where mainly downstream shipping had been common became two-way transportation highways, and rails began to crisscross the land. Journeys that had taken days or months could be made in hours or days. Soon, even ocean crossings took significantly less time. It really was a revolutionary change. In the History of Transportation, Watt’s steam engine has to be seen as a milestone beyond compare.