order to carry the system recommended by them into effect, they proposed to divide the railroad between Liverpool and Manchester into nineteen stages of about a mile and a half each, with twenty-one engines fixed at the different points to work the trains forward.
Such was the result, so far, of George Stephenson’s labours. Two of the best practical engineers of the day concurred in reporting substantially in favour of the employment of fixed engines. Not a single professional man of eminence supported the engineer in his preference for locomotive over fixed engine power. He had scarcely an adherent, and the locomotive system seemed on the eve of being abandoned. Still he did not despair. With the profession as well as public opinion against him—for the most frightful stories were abroad respecting the dangers, the unsightliness, and the nuisance which the locomotive would create—Stephenson held to his purpose. Even in this, apparently the darkest hour of the locomotive, he did not hesitate to declare that locomotive railroads would, before many years had passed, be “the great highways of the world.”
He urged his views upon the directors in all ways, and, as some of them thought, at all seasons. He pointed out the greater convenience of locomotive power for the purposes of a public highway, likening it to a series of short unconnected chains, any one of which could be removed and another substituted without interruption to the traffic; whereas the fixed engine system might be regarded in the light of a continuous chain extending between the two termini, the failure of any link of which would derange the whole. [206] He represented to the Board that the locomotive
was yet capable of great improvements, if proper inducements were held out to inventors and machinists to make them; and he pledged himself that, if time were given him, he would construct an engine that should satisfy their requirements, and prove itself capable of working heavy loads along the railway with speed, regularity and safety. At length, influenced by his persistent earnestness not less than by his arguments, the directors, at the suggestion of Mr. Harrison, determined to offer a prize of £500 for the best locomotive engine, which, on a certain day, should be produced on the railway, and perform certain specified conditions in the most satisfactory manner. [207]
It was now felt that the fate of railways in a great measure depended upon the issue of this appeal to the mechanical genius of England. When the advertisement of the prize for the best locomotive was published, scientific men began more particularly to direct their attention to the new power which was thus struggling into existence. In the mean time public opinion on the subject of railway
working remained suspended, and the progress of the undertaking was watched with intense interest.
During the progress of the discussion with reference to the kind of power to be employed, Mr. Stephenson was in constant communication with his son Robert, who made frequent visits to Liverpool for the purpose of assisting his father in the preparation of his reports to the Board on the subject. They had also many conversations as to the best mode of increasing the powers and perfecting the mechanism of the locomotive. These became more frequent and interesting, when the prize was offered for the best locomotive, and the working plans of the engine which they proposed to construct came to be settled.
One of the most important considerations in the new engine was the arrangement of the boiler and the extension of its heating surface to enable steam enough to be raised rapidly and continuously, for the purpose of maintaining high rates of speed,—the effect of high-pressure engines being ascertained to depend mainly upon the quantity of steam which the boiler can generate, and upon its degree of elasticity when produced. The quantity of steam so generated, it will be obvious, must depend chiefly upon the quantity of fuel consumed in the furnace, and by necessary consequence, upon the high rate of temperature maintained there.
It will be remembered that in Stephenson’s first Killingworth engines he invented and applied the ingenious method of stimulating combustion in the furnace, by throwing the waste steam into the chimney after performing its office in the cylinders, thus accelerating the ascent of the current of air, greatly increasing the draught, and consequently the temperature of the fire. This plan was adopted by him, as we have already seen, as early as 1815; and it was so successful that he himself attributed to it the greater economy of the locomotive as compared with horse power. Hence the continuance of its use upon the Killingworth Railway.
Though the adoption of the steam-blast greatly quickened combustion and contributed to the rapid production of high-pressure steam, the limited amount of heating surface presented to the fire was still felt to be an obstacle to the complete success of the locomotive engine. Mr. Stephenson endeavoured to overcome this by lengthening the boilers and increasing the surface presented by the flue-tubes. The “Lancashire Witch,” which he built for the Bolton and Leigh Railway, and used in forming the Liverpool and Manchester Railway embankments, was constructed with a double tube, each of which contained a fire and passed longitudinally through the boiler. But this arrangement necessarily led to a considerable increase in the weight of the engine, which amounted to about twelve tons; and as six tons was the limit allowed for engines admitted to the Liverpool competition, it was clear that the time was come when the Killingworth locomotive must undergo a further important modification.