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cuAP. IX.] IXESCRIPTION OF THE ENGINE. 89
The engine was, after much labour and anxiety, and frequent alterations of parts, at length brought to completion, having been about ten months in hand. It was first placed upon the Killingworth Railway on the 25th of July, 1814; and its powers were tried on the same day. On an ascending gradient of 1 in 450, the engine succeeded in drawing after it eight loaded carriages of thirty tons' weight at about four miles an hour; and for some time after it continued regularly at work. It was indeed the most successful working engine that had yet been constructed.
Although a considerable advance upon all previous locomotives, “Blutcher” (as the engine was popularly called) was nevertheless a somewhat cumbrous and clumsy machine. The parts were huddled together. The boiler constituted the principal feature; and being the foundation of the other parts, it was made to do duty not only as a generator of steam, but also as a basis for the fixings of the machinery and for the bearings of the wheels and axles. The want of springs was seriously felt; and the progress of the engine was a succession of jolts, causing considerable derangement to the machinery. The mode of communicating the motive power to the wheels by means of the spur gear also caused frequent jerks, each cylinder alternately propelling or becoming propelled by the other, as the pressure of the one upon the wheels became greater or less than the pressure of the other, and, when the teeth of the cogwheel became at all worn, a rattling noise was produced during the travelling of the engine.
As the principal test of the success of the locomotive was its economy as compared with horse power, careful calculations were made with the view of ascertaining this important point. The result was, that it was found the working of the engine was at first barely economical; and at the end of the year the steam power and the horse power were ascertained to be as nearly as possible upon a par in point of cost. The fate of the locomotive in a great measure depended on this very engine. Its speed was not beyond that of a horse's walk, and the heating surface presented to the fire being comparatively small, sufficient steam could not be raised to enable it to accomplish more on an average than about three miles an hour. The result was anything but decisive; and the locomotive might have been condemned as useless, had not Mr. Stephenson at this juncture applied the steam-blast, and at once more than doubled the power of the engine. Although Trevithick, in the engine constructed by him in 1804, allowed the waste steam to escape into the chimney, there was no object in the arrangement except to get rid of a nuisance and to avoid the unsightliness of the escaped steam blowing off in jets into the open air. The exit pipe adopted by Mr. Trevithick, as we have already observed, was not contrived with the view of producing any effect; nor does any seem to have been produced, for it is certain that he afterwards abandoned the arrangement. It is remarkable that a man so ingenious as Trevithick should not have discerned its advantages; but it is clear that he could not have done so, for as late as 1815, after George Stephenson had discovered and successfully adopted the steam blast, Trevithick took out a patent, the principal object of which was to “produce a current of air in the manner of a winnowing machine, to blow the fire.” “Flat plates or leaves,” revolving in a case, were the means adopted by him for this purpose; and in the same patent he proposed to “place in the flue a screw or set of vanes, somewhat similar to a smoke-jack,” which were “to revolve by connection with the steam-engine, for the purpose of creating an artificial draft in the chimney.” This contrivance was, however, a useless one, as Mr. Stephenson's mode of applying the blast already threw it far into the shade as a means of stimulating combustion by artificial means.
chap. Ix.] INVENTION OF THE STEAM BLAST. 91
It is remarkable how little Trevithick really accomplished for railway progress, notwithstanding his ingenuity and skill as an inventor and mechanician. Instructed by Murdock and assisted by Vivian, he was enabled to erect his first steam-carriage, after which he constructed his first railway locomotive. But Trevithick was one of those men who are satisfied with making a beginning. He was not endowed with the gift of continuance — the quality of perseverance. With half the cleverness, and double the application, he might have successfully worked out the problem of railway locomotion, and kept ahead of all competitors.
George Stephenson was a man of an entirely different fibre. His patience was never baffled by failure; his faith was never shaken by opposition. When he became fully possessed by a conviction, he held to it with dogged tenacity, and braved the shafts of ridicule, the arguments of opponents, and the shrugs and the sneers of the utterly indifferent. Above all, he was an accurate and careful observer; and the improvements which he was enabled to effect in the locomotive were mainly due to the care with which he noted facts, and the patient reflection which he bestowed upon them, with the object of turning them to useful account.
Thus, his adoption of the steam blast in the chimney was in no way the issue of accident; but it was an invention the result of careful observation and patient reflection. In his first locomotive the eduction steam was allowed to escape into the open atmosphere, with a hissing blast, which was the terror of horses and cattle, and was generally complained of as a nuisance. A neighbouring squire even threatened an action against the colliery lessees if it were not put an end to. But Mr. Stephenson's attention had already been drawn to the circumstance of the much greater velocity with which the steam issued from the exit pipe, compared with that at which the smoke escaped from the chimney of the engine. He then thought that, by conveying the eduction steam into the chimney by means of a small pipe after it had performed its office in the cylinders, and allowing it to escape in a vertical direction, its velocity would be imparted to the smoke from the fire, or to the ascending current of air in the chimney", thereby increasing the draft, and consequently the intensity of combustion in the furnace. The experiment was no sooner made than the power of the engine was at once more than doubled: combustion was stimulated by the blast; consequently the capability of the boiler to generate steam was greatly increased, and the effective power of the engine augmented in precisely the same proportion, without in any way adding to its weight. This simple but beautiful expedient, though it has hitherto received but slight notice as an original idea on the part of its author, was really fraught with the most important consequences to railway communication; and it is not too much to say that the success of the locomotive depended upon its adoption. Without the steam blast, the advantages of the “multitubular boiler” could never have been fairly tested;
* Mr. Nicholas Wood gives the following account of the circumstances which led to the invention of the steam blast by Mr. Stephenson:—“When the engines were first made, the steam escaped into the atmosphere, and made comparatively little noise. It was found difficult thus to produce steam in sufficient quantity to keep the engine constantly working, or rather to obtain an adequate rapidity of current in the chimney to give sufficient intensity to the fire. To effect a greater rapidity, or to increase the draft of the chimney, Mr. Stephenson thought that, by causing the steam to escape into the chimney through a pipe with its end turned upwards, the velocity of the current would be accelerated ; and such was the effect.” (Practical Treatise on Railroads, by Nicholas Wood, C.E. Ed. 1825, p. 292.) This passage clearly shows the preconceived design and purpose of Mr. Stephenson in inventing the steam blast. A claim has, nevertheless, been set up in behalf of Timothy Hackworth as its inventor in 1829, although the design, mechanism, and rationale of the invention, as effected by Mr. Stephenson in 1815, and adopted by him in all the Killingworth engines from that year downwards, were clearly described by Mr. Wood in 1825 !
chap. Ix.] INVENTION OF THE STEAM BLAST. 93
and it was these two improvements, working together, which afterwards secured the triumph of the locomotive on the opening of the Liverpool and Manchester Railway. Without the steam blast, by which the intensity of combustion was . kept up to the highest point, and the evolution of steam thus rapidly effected, high rates of speed by means of the combustion of coke could not have been attained, and locomotives might still have been dragging themselves unwieldily along at little more than five or six miles an hour. The steam blast had scarcely been adopted, with so decided a success, when Mr. Stephenson, observing the numerous defects in his engine, and profiting by the experience which he had already acquired, determined to construct a second engine, in which to embody his improvements in their best form. Careful and cautious observation of the working of his locomotive had convinced him that the complication arising out of the action of the two cylinders being combined by spurwheels would prevent its coming into practical use. He accordingly directed his attention to an entire change in the construction and mechanical arrangements of the machine; and in the following year, conjointly with Mr. Dodds, who provided the necessary funds, he took out a patent, dated the 28th of February, 1815", for an engine which combined in a remarkable degree the essential requisites of an economical locomotive; that is to say, few parts, simplicity in their action, and directness in the mode by which the power was communicated to the wheels supporting the engine. This locomotive, like the first, had two vertical cylinders, which communicated directly with each pair of the four wheels that supported the engine, by means of a cross head and a
* A grant to Ralph Dodds and George Stephenson, both of Killingworth, engineers, for their various Improvements in the Construction of Locomotive Engines. Patent Office, No. 3887.