Watt Improves Steam Engine

This series has four easy 5-minute installments. This first installment: The Condenser.

Introduction
No greater service has been rendered to the world through mechanical invention than that performed by James Watt in his improvement of the steam-engine. Watt was born at Greenock, Scotland, in 1736. During the eighty-three years of his life much progress was made in mechanics and engineering in different countries, but the name of Watt remains the most brilliant among contemporary workers in these departments of practical science.

The first contriver of a working steam-engine is supposed to have been Edward, second Marquis of Worcester (1601-1667). No complete description of his engine is known to exist, and conjectures about it disagree; but it is not questioned that he made important contributions to the great invention, upon which others at the same time were engaged. The construction of the first actual working steam-engine is usually credited to Thomas Savery, born in England about 1650. He devised a “fire-engine,” as he called it, for the raising of water, but, owing to the want of strong boilers and a suitable form of condenser, it imperfectly served its purpose, and was soon superseded by the better engine of Thomas Newcomen, here referred to by Arago.

Newcomen was an English inventor, born in 1663. With Savery and Cawley, he invented and in 1705 patented the atmospheric steam-engine by which he is known, and which, as told by Arago, gave place to the superior invention of Watt.

This selection is from Biographies of Distinguished Men by François Arago published in 1857. For works benefiting from the latest research see the “More information” section at the bottom of these pages.

Arago was an eminent French physicist and astronomer (1786-1853), who is even better known through his biographies of other great workers in science. His account of “the fruitful inventions which will forever connect the name of Watt with the steam-engine” is all the more valuable for preservation because written while the steam-engine was still in an early stage of its development.

Time: 1769
Place: Glasgow

In physical cabinets we find a good many machines on which industry had founded great hopes, though the expense of their manufacture or that of keeping them at work has reduced them to be mere instruments of demonstration. This would have been the final fate of Newcomen’s machine, in localities at least not rich in combustibles, if Watt’s efforts had not come in to give it an unhoped-for degree of perfection. This perfection must not be considered as the result of some fortuitous observation or of a single inspiration of genius; the inventor achieved it by assiduous labor, by experiments of extreme delicacy and correctness. One would say that Watt had adopted as his guide that celebrated maxim of Bacon’s: “To write, speak, meditate, or act when we are not sufficiently provided with facts to stake out our thoughts is like navigating without a pilot along a coast strewed with dangers or rushing out on the immense ocean without compass or rudder.”

In the collection belonging to the University of Glasgow there was a little model of a steam-engine by Newcomen that had never worked well. The professor of physics, Anderson, desired Watt to repair it. In the hands of this powerful workman the defects of its construction disappeared; from that time the apparatus was made to work annually under the inspection of the astonished students. A man of common mind would have rested satisfied with this success. Watt, on the contrary, as usual with him, saw cause in it for deep study. His researches were successively directed to all the points that appeared likely to clear up the theory of the machine. 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.

Here was enough to occupy the life of a laborious physicist, yet Watt found means to conduct all these numerous and difficult researches to a good termination, without the work of the shop suffering thereby. Dr. Cleland wished, not long since, to take me to the house, near the port of Glasgow, whither our associate* retired, on quitting his tools, to become an experimenter. It was razed to the ground! Our anger was keen but of short duration. Within the area still visible of the foundations ten or twelve vigorous workmen appeared to be occupied in sanctifying the cradle of modern steam-engines; they were hammering with redoubled blows various portions of boilers, the united dimensions of which certainly equaled those of the humble dwelling that had disappeared there. On such a spot, and under such circumstances, the most elegant mansion, the most sumptuous monument, the finest statue, would have awakened less reflection than those colossal boilers.

[* Watt was one of the eight foreign associates of the French Academy of Sciences, which body Arago was addressing. — ED.]

If the properties of steam are present to your mind, you will perceive at a glance that the economic working of Newcomen’s engine seems to require two irreconcilable conditions. When the piston descends, the cylinder is required to be cold, otherwise it meets some steam there, still very elastic, which retards the operation very much, and diminishes the effect of the external atmosphere. Then, when steam at the temperature of 100° flows into the same cylinder and finds it cold, the steam restores its heat by becoming partially fluid, and until the cylinder has regained the temperature of 100° its elasticity will be found considerably attenuated; thence will ensue slowness of motion, for the counterpoise will not raise the piston until there is sufficient spring contained in the cylinder to counterbalance the action of the atmosphere; thence there will also arise an increase of expense.

No doubt will remain on the immense importance of this economical observation, when I shall have stated that the Glasgow model at each oscillation expended a volume of steam several times larger than that of the cylinder. The expense of steam, or, what comes to the same thing, the expense of fuel, or, if we like it better, the pecuniary cost of keeping on the working of the machine, would be several times less if the successive heatings and coolings, the inconveniences of which have just been described, could be avoided.

This apparently insolvable problem was solved by Watt in the most simple manner. It sufficed for him to add to the former arrangement of the engine a vessel totally distinct from the cylinder, and communicating with it only by a small tube furnished with a tap. This vessel, now known as “the condenser,” is Watt’s principal invention.

To Be Continued.

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