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94 THE CrriL ENGINEER AND ARCHITECT’S JOURNAL. [March, nership with liim that, in 1802, Trevithick, while at Camborne, took out his patent for the high-pressure steam engine. About the year 1723, Leopold, a German philosopher, in his comments on Papin’s apparatus in the Theatrum Machinarum, had given the first idea of the application of steam on the high-pressure principle, but his suggestions remained without any practical results. Watt indeed had made some allusion to this principle in his attempts to obtain a locomo tive power, but at any rate was not able to avail himself of it, even if he understood its application, and to the last day of his life displayed an obstinate prejudice against it. It does not appear that Watt had then read the Theatrum Machinarum, and it is not likely that Trevithick in his Cornish seclusion ever saw it, so that lie has the merit of invention as much as of application. The introduction of this improvement gave increased powers to steam, and it is of that importance, that Stuart, not likely from national sympathy to be over-prejudiced in favour of an Englishman, is even inclined to date the era of the steam engine from this invention. It is certain that independently of its merits, this ap plication of steam power is already of paramount importance from its great extension. It affords the means of locomotion on all the rail ways in the world, propels tire swarms of American steamers, and is greatly used in manufacturing operations. In 1804, Trevithick had the opportunity of trying his engine on the Merthyr Tvdvil tramroad as a motive power applied to a carriage. The engine had an eight inch cylinder, and the piston had a stroke of four feet six inches ; it travelled at the rate of five miles an hour, and drew as many waggons as carried ten tons of iron, without requiring any water, for a distance of nine miles.* Stuart says that the great obstacle to its introduction at this time was the supposed want of adhesion, or hold of the wheels upon the rails, to effect the locomotion of the engine. Trevithick and Vivian erected several of their high pressure engines in Wales and other places, and it was about this time, although we do not know whether before or after the experiment on the Merthyr Tyd- vil tramroad, that Trevithick put into operation the first locomotive en gine in London. In the great metropolis Trevithick found ample support in his countryman, Davies Gilbert, the Earl of Stanhope, Mr. Isaac Rogers, Mr. Samuel Rehe, Mr. Henry Clarke, and others con nected with his native county or the cause of science. The engine he used was about the size of an orchestra drum, and which he attached to a phaeton between the back wheels. With this carriage an experi ment was made in Lord’s cricket ground, at Marylebone, several men of science alternately steering it, and expressing their perfect satisfaction as to the ease with which it was directed. From hence it was steered down the New-road, andGray’s-inn-lane, to the coachbnilder’s, whence the phaeton was obtained. Thus it passed overground, since the site of Hancock’s experiments, and perhaps ultimately destined to be witness of the final triumph of this branch of locomotion. The next day Trevithick took this same engine and exhibited it in a cutler’s shop, working the machinery ; which was one of his essays, to show its general applicability. Subsequently he had a temporary tramroad constructed w ithin an enclosure on the ground now occupied by Euston-square. This road was of an elliptical form, and on it he ran his locomotive. It was opened to the public as an exhibition, and people crowded to see it, but the second day Trevithick, in one of his usual freaks, re moved the engine, and, to the great disappointment of visitants, closed the ground. This he did under the impression that it was better to let the affair drop, until he saw the opportunity to avail himself of it advantageously. Another occupation of his metropolitan career was the tunnel under the Thames, in which he owed it only to his own pertinacity that he disappointed both the public and himself. Ralph Dodd, an engineer of some note of the last century, was the first to commence operations for a tunnel under the Thames from Gravesend to Tilbury Fort. His plan was to avail himself of the chalk stratum which he supposed to run under the bed of the river, and he expected that the chalk quarried out would sufficiently pay the expenses of working, leaving its subsequent use as a viaduct to afford a handsome income. As was mentioned by a correspondent in one of our late numbers,j- he obtained an Act of Parliament for his plan in 1799, with power to raise 30,0001., and to increase his capital incase of need to 50,0001., his estimate being only 1.5,0001. The work was commenced, and proceeded for about three years, but was ultimately stopped on account of the expense of drainage. He had gone on the assumption that the chalk would be in one solid stratum, and that he should not be embarrassed by water, having in his estimates allowed only 17801. for this purpose, and treated the expense as merely contingent. He found, however, such great inconvenience from under-springs rising through fissures in the chalk, that as we have said, he was obliged to abandon the project. ’ Historical and Descriptive Anecdotes of the Steam Engine, by It, Stuart, p. 100.— Jiichoben’s Operative Mechanic, p. 209. t Vol. 1, p. 3*1, This tended to throw a damp on such plans, and when Trevithick pro posed a similar tunnel under the Thames at Rotherhithe,he found a na tural reluctance to support any such undertaking. Several of his friends, however, raised a subscription to enable him to make an experiment on a small scale, and the result was anxiously awaited to justify an appeal to the public for carrying out the entire plan. In 1809, therefore, Trevithick was employed in running a small driftway parallel to the bed of the Thames. The committee of sub scribers justly felt every assurance of the success of the undertaking, for the operation was extremely simple, while they had entire confidence in his skill and ability, from the experience he had gained in similar underground mining works. We have tunnels four miles in length to some of our canals, and abundance of communications in the mining districts under the surface of the earth, and even beneath the sea ; but notwithstanding the ease of such a work, extraneous causes have always hitherto prevented this kind of viaduct from being used under rivers. Trevithick, to save labour and expense, committed the usual funda mental error of not going deep enough below the bed of the river, the object in his case being a close-run endeavour to keep at the least possible distance from it. Had his experiment been concluded, this would have enabled him to give a plausible original estimate at any hazard of subsequent increased expense. This error, however, was not productive of much inconvenience to him, nor was it the immediate cause of the abandonment of the enterprise, for he carried his drift way to a greater extent without impediment than has been done in any other attempt. It was not until he had gone 930 feet* under the river, that he encountered any obstacle, when he got into a hole in the muddy bottom of the river, and at one time a piece of uncooked ship beef, which had fallen from one of the vessels, drifted into the works. Although the Corporation authorities refused to allow him any facilities, he managed to get this hole stopped, and again went on with vigor ; he carried on the excavation at the rate of from four to ten feet per day, and soon completed a thousand feet, to the great joy of every one concerned. On arriving at this distance, according to his previous agreement with the committee, Trevithick was to receive a hundred guineas, which, after a verification of the work by a surveyor, were paid to him. This surveyor was appointed by the subscribers to check Trevithick, and in giving in his report, confirming the measurement, stated that the line had been run one foot out of the perpendicular. This statement Trevithick took in high dudgeon, and chose to consider it as a deep reflection on his engineeiing skill to have deviated one foot in a thousand. His Cornish blood was excited, and with his usual impetuosity, he set to work to disprove the assertion, without any regard to consulting his own interest, or embroiling himself with the committee. Of all possible contrivances for effecting this object, he adopted the most absurd, which was no less than to make a hole in the roof of the tunnel at low w’ater, and to push through a series of jointed rods to be received by a party in a boat, and then observed from the shore. Even had he been successful in carrying out this process, it would have afforded no criterion of the precision of the work, as the set of the current would necessarily have swerved the rod. Trevithick was employed in the driftway in carrying out this contrivance, and as delays of course ensued in fitting together the rods, the gully consequent on the opening in the roof ultimately admitted so much water as to render a retreat necessary. With a moral courage innate to his character,and worthy of a better cause, he sent the men on before him, and very nearly fell a sacrifice to his devotion. It has been already observed that the driftway was parallel to the bed of the river, and consequently curved ; it necessarily happened, therefore, that the enter ing w’ater wotdd lodge, syphon-like, in thebottom of the curve, at which part, on Trevithick’s arrival, he found so much water as hardly to be able to escape, for as he ascended the slope on the other side, and climbed the ladders, the water rose to his neck. It is needless to say, that this act of rashness was the death-blow to the project, while it added the climax to the many acts of inconsistency with which Trevithick’s erratic career w'as disturbed. On a subsequent occasion, being cross- examined as to this occurrence while witness on a trial, he admitted the fact of his ruining the works, and his determination in any similar circumstance to defend his own character at whatever sacrifice to other people. The work thus ended after having reached 1,011 feet, and remains within a hundred feet of its proposed terminus, a melancholy monument at once of his folly and his skill. After these events Trevithick returned to Camborne, and we now approach another of those epochs of his life, in which his labours were again destined to be followed by the most extended results. Here we have an instance of the operation of those trains of finite causes, which, while they are sometimes productive of the most unexpected advan tages, too often baffle all human expectations and anangements.f * Mechanics* Magazine, Vol. 1. t Transactions of the Cornwall ecological Sycietj. Mr- Buase's Memoir,