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Updated: May 16, 2025
He published the result of his observations in his 'Century of Inventions, which formed a sort of text-book for inquirers into the powers of steam for a time, until Savary, Newcomen, and others, applying it to practical purposes, brought the steam-engine to the state in which Watt found it when called upon to repair a model of Newcomen's engine, which belonged to the University of Glasgow.
In 1711, almost a hundred years after the arrival at Jamestown and Plymouth of the fathers of our present civilization, the steam-engine that is called Newcomen's began to be used for the pumping of water out of mines. This engine, slightly modified, and especially by the boy who invented the automatic cut-off for the steam valves, was a most rude and clumsy machine measured by our ideas.
In the year 1760, James Watt, who was by occupation what is now known as a model-maker, and who lived in Glasgow, was called upon to repair a model of a Newcomen engine belonging to the university. While thus engaged he was impressed with the great waste of steam, or of time and fuel, which is the same thing, involved in the alternate heating and cooling of Newcomen's cylinder.
When the piston descends in Newcomen's engine, it is by the weight of the atmosphere. The atmosphere is cold; hence it must cool the sides of the metal cylinder, which is open at the top, in proportion as it expands itself over the entire surface. This cooling is not compensated during the whole ascension of the piston, without the expense of a certain quantity of steam.
He ascertained the proportion in which water dilates in passing from a state of fluidity into that of vapor; the quantity of water that a certain weight of coal can convert into vapor; the quantity and weight of steam expended at each oscillation by one of Newcomen's engines of known dimensions; the quantity of cold water that must be injected into the cylinder to give a certain force to the piston's descending oscillation; and finally the elasticity of steam at various temperatures.
Watt, though greatly irritated, was not discouraged. His engines were not, in the first place, like Newcomen's, mere pumps, mere draining-pumps. In a few years he transformed them into universal motive powers, and of indefinite force. His first step in this line was the invention of a double-acting engine (
In 1762 Watt tried some experiments on high-pressure steam, and made a model to show how motion could be obtained from that power; but did not pursue his experiments on account of the supposed danger of such pressure. He next had a model of Newcomen's engine, which would not work well, sent him to repair. Watt soon found out its faults, and made it work as it should do.
As soon as the piston has quite reached the bottom, the mere turning of a tap suffices to bring the two areas of the cylinder, situated above and below the piston, into communication with each other, so that both shall be filled with steam at the same degree of elasticity; and the piston being thus equally acted upon, upward and downward, ascends again to the top of the cylinder, as in Newcomen's atmospheric engine, merely by the action of a slight counterpoise.
Leaving for the present the history of the gas engine, which brings us to a stage comparable to the state of the steam engine during the Newcomen's time, it will be advisable to give some consideration to the principles concerned in the economical and efficient working of gas engines, in order to understand the more recent developments.
It was in 1763, when he was twenty-eight and had the appointment of mathematical-instrument maker to the University of Glasgow, that a model of Newcomen's steam pumping engine was brought into his shop for repairs.
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