The Governor Regulates the Steam

Today’s installment concludes Watt Improves Steam Engine,
our selection from Biographies of Distinguished Men by François Arago published in 1857.

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Previously in Watt Improves Steam-Engine.

Power is not the only element of success in industrial works. Regularity of action is not less important; but what regularity could be expected from a motive power engendered by fire fed by shovelfuls, and the coal itself of various qualities; and this under the direction of a workman, sometimes not very intelligent, almost always inattentive? The motive steam will be more abundant, it will flow more rapidly into the cylinder, it will make the piston work faster in proportion as the fire is more intense. Great inequalities of movement then appear to be inevitable. Watt’s genius had to provide against this serious defect. The throttle-valves by which the steam issues from the boiler to enter the cylinder are constantly open. When the working of the engine accelerates, these valves partly close; a certain volume of steam must therefore occupy a longer time in passing through them, and the acceleration ceases. The aperture of the valves, on the contrary, dilates when the motion slackens. The pieces requisite for the performance of these various changes connects the valves with the axes which the engine sets to work, by the introduction of an apparatus, the principle of which Watt discovered in the regulator of the sails of some flourmills: this he named the “governor,” which is now called the “centrifugal regulator.” Its efficacy is such, that a few years ago, in the cotton-spinning manufactory of a renowned mechanic, Mr. Lee, there was a clock set in motion by the engine of the establishment, and it showed no great inferiority to a common spring clock.

Watt’s regulator, and an intelligent use of the revolving principle — that is the secret, the true secret, of the astonishing perfection of the industrial products of our epoch; this is what now gives to the steam-engine a rate entirely free from jerks. That is the reason why it can, with equal success, embroider muslins and forge anchors, weave the most delicate webs and communicate a rapid movement to the heavy stones of a flourmill. This also explains how Watt had said, fearless of being reproached for exaggeration, that to prevent the comings and goings of servants, he would be served, he would have gruel brought to him, in case of illness, by tables connected with his steam-engine. I am aware it is supposed by the generality of people that this suavity of motion is obtained only by a loss of power; but it is an error, a gross error: the saying, “much noise and little work,” is true, not only in the moral world, but is also an axiom in mechanics.

A few words more and we shall reach the end of our technical details. Within these few years great advantage has been found in not allowing a free access of steam from the boiler into the cylinder, during the whole time of each oscillation of the engine. This communication is interrupted, for example, when the piston has reached one-third of its course. The two remaining thirds of the cylinder’s length are then traversed by virtue of the acquired velocity, and especially by the detention of the steam. Watt had already indicated such an arrangement. Some very good judges esteem the economical importance of the steam-detent as equal to that of the condenser. It seems certain that since its adoption the Cornwall engines give unhoped-for results; that with one bushel of coal they equal the labor of twenty men for ten hours. Let us keep in mind that in the coal districts a bushel of coal only costs ninepence, and it will be demonstrated that over the greater part of England Watt reduced the price of a man’s day’s work, a day of ten hours’ labor, to less than a sou (one halfpenny).

Numerical valuations make us appreciate so well the importance of his inventions that I cannot resist the desire to present two more improvements. I borrow them from one of the most celebrated correspondents of the Academy — from Sir John Herschel.

The ascent of Mont Blanc, starting from the valley of Chamounix, is justly considered as the hardest work that a man can accomplish in two days. Thus, the maximum mechanical work of which we are capable in twice twenty-four hours is measured by transporting the weight of our body to the elevation of Mont Blanc. This work or its equivalent would be accomplished by a steam-engine in the course of burning one kilogram (two pounds) of coal. Watt has, therefore, ascertained that the daily power of a man does not exceed what is contained in half a kilogram (one pound) of coal.

Herodotus records that the construction of the great Pyramid of Egypt employed 100,000 men for 20 years. The pyramid consists of calcareous stone; its volume and its weight can be easily calculated; its weight has been found to be about 5,900,000 kilograms (nearly 5,000 tons). To elevate this weight to 38 meters, which is the pyramid’s center of gravity, it would require to burn 8244 hectoliters of coal. Our English neighbors have some foundries where they consume this quantity every week.

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

This ends our series of passages on Watt Improves Steam-Engine by François Arago from his book Biographies of Distinguished Men published in 1857. This blog features short and lengthy pieces on all aspects of our shared past. Here are selections from the great historians who may be forgotten (and whose work have fallen into public domain) as well as links to the most up-to-date developments in the field of history and of course, original material from yours truly, Jack Le Moine. – A little bit of everything historical is here.

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