[By R. P. Leitch.]
Meanwhile Watt went on inventing, even while he was complaining of his inability to invent, and of the uselessness of inventing. Invention had grown into a habit with him, which he could not restrain. In the very letter in which he wrote “It is of no use inventing—everybody is seizing upon our schemes,” he communicated to Boulton that he had contrived a machine, then erecting at Dalcoath, for the purpose of stopping the engine when at full speed, when any accident happened to the rods or outside chains,—first taking away the power, and then holding the bob fast whenever it might be at the turn.[227] A few days later he communicated that he had contrived a new way of opening the regulators. He was also finishing his plan of the new equalising beam, and the double expansion engine, which he requested might be proceeded with at once. “I have shown the equalising beam,” said he, “to no person whatever. Please push it on. It is our dernier ressort, and may perhaps be all that villany will leave us, and that not long.”[228] Boulton wrote back, bidding his partner to be of good heart. “If our spirits don’t fail us,” said he, “I think our engine won’t.”
At the same time Watt was inventing his new jointed top-working gear, which he reported answered exceedingly well with the Dalcoath engine; and, in pursuance of an idea thrown out by Boulton, he perfected the model of a horizontal-axled elliptical with one pulley, which he described as performing à merveille, being free from all untoward frictions. He was also busy inventing a new method of an equalising beam, by causing the gudgeon to change its place; and another by means of a roller acting upon a curve in the nature of the working gear. Besides his experiments in mechanics, he was prosecuting investigations as to the properties of nutgalls in combination with various chemical substances, for the purpose of obtaining the best kind of ink for use with his copying machines; and at another time we find him contriving various iron cements for joints, confessing that he had “lost all faith in putty;” the result of which was his discovery of the well-known metallic cement.
In the correspondence between the partners on these various topics, we seem to see the ideas out of which so many inventions grew, in their various stages of birth, growth and development. They concealed nothing from each other, but wrote with the most perfect unreserve. Each improved on the other’s ideas,—Watt upon Boulton’s, and Boulton upon Watt’s; both experimenting on the same subject at the same time, and communicating the results in the most elaborate detail. The phrase often occurs in their letters: “I write thus fully that you may see exactly what is passing in my mind.” The letters were sometimes of extraordinary length, one of Boulton’s (dated 25th September, 1781) extending to eight pages folio, closely written, containing upwards of 4000 words. Scarcely a day passed without their spending several hours in writing to each other. Boulton also kept up a correspondence with Mrs. Watt, in addition to his elaborate letters to her husband. The lady entered into various matters of personal interest, describing her occupations and domestic pursuits, and communicating the state of her husband’s health, which was a matter of no less interest to Boulton than to herself.
As the autumn set in with its fogs and rains, Watt’s headaches returned with increased severity, and he repeatedly complained to Boulton of being “stupid and ill, and scarcely able to think.” “I tremble,” said he, “at the thought of making a complete set of drawings. I wish you could find me out a draughtsman of abilities; as I cannot stand it much longer.”[229] Watt’s temper was also affected by the state of his health; and he confessed that he felt himself not at all cut out for the work he had to do, so far as related to business: “I am not philosopher enough,” he said, “to despise the ills of life; and when I suffer myself to get into a passion, I observe it hurts me more than it does anybody else. I never was cut out for business, and wish nothing so much as not to be obliged to do any; which perhaps will never fall to my lot; therefore I must drag on a miserable existence the best way I can.”[230]
Watt was very busy at this time in preparing the specification and drawings of the circular motion, which he said he found an extremely difficult job owing to the distracted state of his head. The letters patent for the invention had been secured on the 25th October, 1781, and he had four months allowed him in which to prepare and lodge the full description. He laboured at his work late and early, his mind being for months in the throes of invention. In the beginning of November we find him writing to Boulton, sending him the “first three yards of the specification,” written out on folio sheets joined together. Watt’s letters to his partner at this time contain numerous rough sketches of his proposed methods for securing circular motion without using the crank, from which he conceived himself to be in a measure precluded by Pickard’s patent. He devised no fewer than five distinct methods by which this object might be accomplished, by means of wheels of various sorts rotating round an axis. The method eventually preferred was the one invented by Wm. Murdock, and commonly known as the sun and planet motion.[231] “It has the singular property,” said Watt, “of going twice round for each stroke of the engine, and may be made to go oftener round if required without additional machinery.”
SUN AND PLANET MOTION.
Rough sketches of these various methods were forwarded to Soho in order that the requisite careful drawings of them might be prepared in time to be lodged with the specification; but when they reached Watt in Cornwall, he declared them to be so clumsily executed that he could not for very shame send them in; and though greatly pressed by mining business, and suffering from “backache, headache, and lowness of spirits,” he set to work to copy them with his own hands. He worked up his spare time so diligently, that in ten days he had the plans finished and returned to Boulton, whom he wrote saying that he had improved the construction of several of the machines, and “got one copy of the specification drawing finished in an elegant manner upon vellum, being the neatest drawing he had ever made.”[232] The necessary measures being then taken to perfect the patent, it was duly enrolled on the 23rd February, 1782.
During the time that Watt was busy completing the above specification and drawings, his mind was full of other projects, one of which was the perfecting of his new expansive engine.[233] It is curious to find him, in his letters to Boulton, anticipating the plan of superheating the steam before entering the cylinders, which has since been carried into effect with so much success.