It will be remembered that one of the early speculations of Roger Bacon related to the employment of engines of navigation without oarsmen, “so that the greatest river and sea ships, with only one man to steer them, may sail swifter than if they were fully manned,”—that one of the uses to which Papin proposed to apply the steam-engine was to “propel ships against the wind and tide,” in illustration of which he constructed his model steamboat,—and that, shortly after Newcomen’s engine had become generally introduced as a pumping power, Jonathan Hulls took out a patent with the object of applying it to tow ships into and out of harbours. Hulls was followed, after a long interval, by Jouffroy in France and by Fitch in America, but none of their experiments proved successful; and it was not until Watt invented the condensing engine that it was found practicable to employ steam as a regular propelling power in navigation.
It was natural that the extraordinary success of Watt’s invention should direct attention anew to the subject. The engine, in the powerful, compact, economical, and manageable form, into which he had brought it, was found able to effect rotary motion in the various processes of manufacture; and, in a maritime country like England, the thought that would naturally occur to many minds would be this: If the steam-engine can drive mill-wheels, why may it not in like manner be employed to drive the wheels of carriages by land and the paddle-wheels of vessels by sea? The subject was, indeed, often brought under the notice of both Boulton and Watt; but the anxiety, annoyance and expense to which they had been subjected in defending their original patent, deterred them from venturing on this new field of enterprise. Watt never made his proposed locomotive engine for running on common roads; and the model constructed by Murdock at Redruth in 1784, remained a model still.
The subject was, however, shortly after taken up by William Symington, at Wanlockhead, in Scotland, where his father was employed as engineman in superintending the working of one of Boulton and Watt’s pumping-engines. The sight of this engine, and his father’s employment upon it, had probably the effect of first directing his attention to steam-power and its extended uses; and having heard of Murdock’s ingenious design from Boulton and Watt’s men, who were constantly visiting and inspecting the pumping-engine,[364] it occurred to him to try whether he could not himself construct the model of a steam-carriage for use on common roads. He succeeded in making his model, and when it was finished, Mr. Meason, the manager of the Wanlockhead Lead Mines, was so much pleased with it that he asked the young man to accompany him to Edinburgh, to show it to the leading men of science in that city. Mr. Meason allowed it to be exhibited at his own house, Symington being in attendance to give explanations. Some of the Edinburgh professors, who came to see the model, were so much pleased with the youthful inventor (then only about twenty years of age), and the indications of mechanical genius which his machine displayed, that they strongly recommended Mr. Meason to enter him as a student at the University, which he readily assented to, and Symington accordingly matriculated at Edinburgh College in 1786, and, amongst other lectures, attended those of Dr. Black on Chemistry in the following session.
The Scotch roads were in too bad a condition at the time to admit of their being run over by a locomotive, and Symington eventually abandoned his proposed scheme. But he had also an idea that the steam-engine might be economically applied to the working of boats on canals, or ships at sea; and with that object he invented an engine specially adapted for the purpose. This clearly appears from his correspondence with Thomas Gilbert, M.P., brother to the Duke of Bridgewater’s land steward. Mr. Gilbert had inspected the model of the steam-carriage while on a visit to Edinburgh, and at the same time had some conversation with Symington as to the employment of the steam-engine in hauling canal-boats, the result of which was that Symington promised to write him more fully on both topics. He proceeded to do so in a letter dated Wanlockhead, 24th September, 1786; in which, after describing the dimensions, power, mode of working, and the probable price (about 70l.) of a full-sized locomotive, he proceeded—
“But an engine of the same power and apparatus for working boats on canals, will only coast about fifty pounds, and will only weight 110 st. Each strock of the engine will have a force equall to 160 st. weight when applied, which undoubtedly will be able to drag a great weight upon water, when we run the proportion between it and what a man can do in a boat with common oars, whose exertion does not exceed more than 7 stones; but of this you will be a better judge than me. The engine we propose for working the land-carriage is Mr. Watt’s, with some very material alterations; and before we can use it we must make an agreement with him, which we intend to propose immediately. But the engine we propose to work boats or ships with is an engine intirely of our own invention, and more powerful and better adapted for the purpose than Mr. Watt’s engine. This engine of our own we have presently at worke here is a large moddle, by which we have properly ascertained its power, and found it exceed Mr. Watt’s engine nearly two pounds upon each square inch on the piston, without any greater consumpt of coals. Another advantage attending our engine is its being little more complicated than the old engine that works with an atmospheric pressure. We are to use our endeavours immediately for a patent for this engine as well as our carriage; your assistance, when we get application made, will be of great service to us, and thankfully received by, Sir, &c. &c., William Symington.”[365]
About the same time that Symington was exhibiting his model carriage in Edinburgh, Mr. Miller of Dalswinton was trying experiments at Leith in propelling boats by paddle-wheels worked by men at a capstan. He had a triple vessel built, with wheels placed inside, on turning which the vessel was impelled forward. It will be observed that this was but a repetition of the old experiment of Blasco Garay at Barcelona, and of Savery on the Thames. The experiments were on the whole successful, but the power employed in propelling the vessel was felt to be defective, and the turning of the capstan was very hard work, at which men could not be brought to work continuously for any long period.
MILLER’S TRIPLE VESSEL.
Mr. Miller, being curious as to all mechanical novelties, went, amongst others, to see Symington’s model locomotive; and in the course of conversation with the inventor informed him of his own project, describing the difficulty he had experienced in getting his paddles turned for lack of power. The immediate remark of Symington was, “Why don’t you use the steam-engine?” He proceeded to show how easily the engine might be connected with the wheels of the boat, using the model of the steam-carriage before him to explain his meaning. Mr. Miller appeared to have been struck by the suggestion, and in the pamphlet which he shortly after published describing his new vessel, he referred to the probable employment of steam-power for the purpose of driving the paddles. “I have reason to believe,” he said, “that the power of the steam-engine may be applied to work the wheels, so as to give them a quicker motion, and consequently to increase that of the ship. In the course of this summer, I intend to make the experiment; and the result, if favourable, shall be communicated to the public.”[366]
Mr. Miller subsequently contrived and constructed a double vessel, 60 feet in length, worked by a paddle-wheel placed amidships between the two halves of the ship, with a clear waterway in the middle in which the paddle was worked, propelling the vessel. An experiment with this new ship was tried in June, 1787, which was considered successful. “The vessel being put in motion by the water-wheel, wrought by five men at the capstern, was steered so as to keep the wind right ahead, and her rate of going was found by the log to be three and a half miles in the hour.”[367] A sailing-match was arranged by Mr. Miller, in which he was to run his vessel from Inchcolm (a small island in the Frith of Forth) to Leith, against a Custom-house wherry which was reckoned a fast sailer. In this race the double vessel beat by a few minutes. A young man named James Taylor, who officiated in Mr. Miller’s family as tutor to his two younger sons, was on board the vessel, and took his turn in working the wheels, which he found to be “very severe exercise.” In consequence of this trial and its results, Taylor became persuaded that unless a more commanding power than that of men could be applied, the invention of the paddle-ship would prove of little use; and on turning the matter over in his mind, he suggested to Mr. Miller the use of the steam-engine. This, however, was no new idea, as, from what we have already stated, it is clear that it had already occurred to Symington, who had even contrived an engine for the express purpose of propelling ships. As Taylor was intimate with Symington, and a fellow-student with him at Edinburgh College in the session of 1786–7, it is probable that Taylor obtained from him his first idea of the application of the steam-engine to Mr. Miller’s paddle-boat.