The next step was to construct a model engine for the purpose of embodying the invention in a working form. With this object Watt hired an old cellar, situated in the first wide entry to the north of the beef-market in King Street, and there proceeded with his model. He found it much easier, however, to prepare his plan than to execute it. Like most ingenious and inventive men, Watt was extremely fastidious; and this occasioned considerable delay in the execution of the work. His very inventiveness to some extent proved a hinderance; for new expedients were perpetually occurring to him, which he thought would be improvements, and which he, by turns, endeavoured to introduce. Some of these expedients he admits proved fruitless, and all of them occasioned delay. Another of his chief difficulties was in finding competent workmen to execute his plans. He himself had been accustomed only to small metal work, with comparatively delicate tools, and had very little experience “in the practice of mechanics in great,” as he termed it. He was therefore under the necessity of depending, in a great measure, upon the handiwork of others. But mechanics capable of working out Watt’s designs in metal were then with difficulty to be found. The beautiful self-acting tools and workmanship which have since been called into being, principally by his own invention, did not then exist. The only available hands in Glasgow were the blacksmiths and tinners, little capable of constructing articles out of their ordinary walks; and even in these they were often found clumsy, blundering, and incompetent. The result was, that in consequence of the malconstruction of the larger parts, Watt’s first model was only partially successful. The experiments made with it, however, served to verify the expectations he had formed, and to place the advantages of the invention beyond the reach of doubt. On the exhausting-cock being turned, the piston, when loaded with 18 lbs., ascended as quick as the blow of a hammer; and the moment the steam-cock was opened, it descended with like rapidity, though the steam was weak, and the machine snifted at many openings.
Satisfied that he had laid hold of the right principle of a working steam-engine, Watt felt impelled to follow it to an issue. He could give his mind to no other business in peace until this was done. He wrote to a friend that he was quite barren on every other subject. “My whole thoughts,” said he, “are bent on this machine. I can think of nothing else.”[80] He proceeded to make another and bigger, and, he hoped, a more satisfactory engine, in the following August; and with that object he removed from the old cellar in King-street to a larger apartment in the then disused pottery or delftwork near the Broomielaw. There he shut himself up with his assistant, John Gardiner, for the purpose of erecting his engine. The cylinder was five or six inches in diameter, with a two-feet stroke. The inner cylinder was enclosed in a wooden steam-case, and placed inverted, the piston working through a hole in the bottom of the steam-case. After two months’ continuous application and labour it was finished and set to work; but it leaked in all directions, and the piston was far from air-tight. The condenser also was in a bad way, and needed many alterations. Nevertheless, the engine readily worked with 10½ lbs. pressure on the inch, and the piston lifted a weight of 14 lbs. The improvement of the cylinder and piston continued Watt’s chief difficulty, and taxed his ingenuity to the utmost. At so low an ebb was the art of making cylinders that the one he used was not bored but hammered, the collective mechanical skill of Glasgow being then unequal to the boring of a cylinder of the simplest kind; nor, indeed, did the necessary appliances for the purpose then exist anywhere else. In the Newcomen engine a little water was poured upon the upper surface of the piston, and sufficiently filled up the interstices between the piston and the cylinder. But when Watt employed steam to drive down the piston, he was deprived of this resource, for the water and the steam could not coexist. Even if he had retained the agency of the air above, the drip of water from the crevices into the lower part of the cylinder would have been incompatible with keeping the surface hot and dry, and, by turning into vapour as it fell upon the heated metal, it would have impaired the vacuum during the descent of the piston.
While he was occupied with this difficulty, and striving to overcome it by the adoption of new expedients, such as leather collars and improved workmanship, he wrote to a friend, “My old white-iron man is dead;” the old white-iron man, or tinner, being his leading mechanic. Unhappily, also, just as he seemed to have got the engine into working order, the beam broke, and having great difficulty in replacing the damaged part, the accident threatened, together with the loss of his best workman, to bring the experiment to an end. But though discouraged by these misadventures, he was far from defeated, but went on as before, battling down difficulty inch by inch, and holding good the ground he had won, becoming every day more strongly convinced that he was in the right track, and that the important uses of the invention, could he but find time and means to perfect it, were beyond the reach of doubt.
But how to find the means! Watt himself was a comparatively poor man; having no money but what he earned by his business of mechanical instrument making, which he had for some time been neglecting through his devotion to the construction of his engine. What he wanted was capital, or the help of a capitalist willing to advance him the necessary funds to perfect his invention. To give a fair trial to the new apparatus would involve an expenditure of several thousand pounds; and who on the spot could be expected to invest so large a sum in trying a machine so entirely new, depending for its success on physical principles very imperfectly understood?
There was no such help to be found in Glasgow. The tobacco lords, though rich, took no interest in steam power, and the manufacturing class, though growing in importance, had full employment for their little capital in their own concerns.
CHAPTER VIII.
Watt’s Connexion with Dr. Roebuck—Watt acts as Surveyor and Engineer.
Dr. Black continued to take a lively interest in Watt’s experiments, and lent him occasional sums of money from time to time to enable him to prosecute them to an issue. But the Doctor’s means were too limited to permit him to do more than supply Watt’s more pressing necessities. Meanwhile, the debts which the latter had already incurred, small though they were in amount, hung like a millstone round his neck. Black then bethought him whether it would not be possible to associate Watt with some person possessed of sufficient means, and of an active commercial spirit, who should join as a partner in the risk, and share in the profits of the enterprise. Such a person, he thought, was Dr. Roebuck, the founder of the Carron Iron Works, an enterprising man, of undaunted spirit, not scared by difficulties, nor a niggard of expense when he saw before him any reasonable prospect of advantage.[81]
Roebuck was at that time engaged in sinking for coal on a large scale near Boroughstoness, where he experienced considerable difficulty in keeping the shafts clear of water. The Newcomen engine, which he had erected, was found comparatively useless, and he was ready to embrace any other scheme which held out a reasonable prospect of success. Accordingly, when his friend Dr. Black informed him of an ingenious young mechanic at Glasgow who had invented a steam-engine, capable of working with increased power, speed, and economy, Roebuck immediately felt interested, and entered into correspondence with Watt on the subject. He was at first somewhat sceptical as to the practicability of the new engine, so different in its action from that of Newcomen; and he freely stated his doubts to Dr. Black. He was under the impression that condensation might in some way be effected in the cylinder without injection; and he urged Watt to try whether this might not be done. Contrary to his own judgment, Watt tried a series of experiments with this object, and at last abandoned them, Roebuck himself admitting his error.
Up to this time Watt and Roebuck had not met, though they carried on a long correspondence on the subject of the engine. In September, 1765, we find Roebuck inviting Watt to come over with Dr. Black to Kinneil (where Roebuck lived), and discuss with him the subject of the engine. Watt wrote to say that “if his foot allowed him” he would visit Carron on a certain day, from which we infer that he intended to walk. But the way was long and the road miry, and Watt could not then leave his instrument shop, so the visit was postponed. In the mean time Roebuck urged Watt to press forward his invention with all speed, “whether he pursued it as a philosopher or as a man of business.”