The persecutions which a warm-hearted man meets with, in the quarters where strict justice would lead him to expect unanimous testimonies of gratitude, seldom fail to discourage, and to sour his disposition. Nor did Watt's good-humor remain proof against such trials. Seven long years of lawsuits had excited in him such a sentiment of indignation, that it occasionally showed itself in severe expressions; thus he wrote to one of his friends: "What I most detest in this world are plagiarists! The plagiarists. They have already cruelly assailed me; and if I had not an excellent memory, their impudent assertions would have ended by persuading me that I have made no improvement in steam-engines. The bad passions of those men to whom I have been most useful (would you believe it?) have gone so far as to lead them to maintain that those improvements, instead of deserving this denomination, have been highly prejudicial to public wealth."
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 (à double effet).
In the engine known under this name, as well as in the one denominated the "modified" engine, the steam from the boiler, when the mechanic wishes it, goes freely above the piston and presses it down without meeting any obstacle; because at that same moment, the lower area of the cylinder is in communication with the condenser. This movement once achieved, and a certain cock having been opened, the steam from the caldron can enter only below the piston and elevates it. The steam above it, which had produced the descending movement, then goes to regain its fluid state in the condenser, with which it has become, in its turn, in free communication. The contrary arrangement of the cocks replaces all things in their primitive state, as soon as the piston has regained its maximum height. Thus similar effects are reproduced indefinitely.
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 connect 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 flour-mills: 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 flour-mill. 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 during 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 during 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 metres, which is the pyramid's centre of gravity, it would require to burn 8244 hectolitres of coal. Our English neighbors have some foundries where they consume this quantity every week.