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Chrimes watch: Watt remembered

Spring marks the 250th anniversary of a significant breakthrough in the development of the steam engine: James Watt’s invention of the separate condenser.

James Watt was asked to repair Glasgow University’s model Newcomen engine

Source: Louis Figuier

James Watt was asked to repair Glasgow University’s model Newcomen engine

One Sunday in May 1765, Watt was strolling across Glasgow Green, and in his own words, “had passed the old washing-house. I was thinking upon the [Newcomen steam] engine at the time, and had gone as far as the herd’s house, when the idea came into my mind that, as steam was an elastic body, it would rush into a vacuum, and if a communication were made between the cylinder and an exhausted vessel, it would rush into it, and might be there condensed without cooling the cylinder.”

Watt’s description of his Eureka moment suggests a somewhat fortuitous process of invention. But, his stroll was preceded by a great deal of experimentation.

The Newcomen engine was introduced in 1712, and since then engineers and scientists had contemplated improvements.

Temperature change

In 1763 Watt was asked to repair Glasgow University’s model Newcomen engine. He took advantage of this, carrying out experiments, and identifying problems – notably the wastage of steam during the ascent of the piston, and the attempt to form a vacuum by cooling the system.

He demonstrated the elasticity of steam at various temperatures, observed the volume of water converted to steam, trialled different materials for cylinders and configurations of the machinery. He demonstrated the latent heat of steam, and had scientific understanding to back his observations.

John Smeaton was also striving to improve the engine. Smeaton’s success was appreciated, but he failed to make the intellectual leap that Watt’s had made. But the cost of using Watt’s patents meant mine owners continued with cheaper Newcomen type engine, and water power remained attractive to factory owners.

While Smeaton is remembered as “the father of civil engineering”, Watt is regarded as a mechanical engineer. Both however were multi-talented, and one reason Watt did not advance his engine more quickly was his employment on Scottish canal and river surveys.

250-year celebration

Glasgow University and the Scottish Engineering Hall of Fame celebrate Watt’s inspirational stroll on 5 June.

More details at www.engineeringhalloffame.org

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