"It was maintained by many that the results of the experiments led to the greatest possible mechanical absurdities. For instance, it was maintained that, if friction were constant at all velocities upon a level railway, when once a power was applied to a carriage which exceeded the friction of that carriage by the smallest possible amount, that same small excess of power would be able to convey the carriage along a level railway at all conceivable velocities. When this position was put by those who opposed the conclusions at which my father had arrived, he felt great hesitation in maintaining his own views; for it appeared to him at first sight really to be—as it was put by his opponents—an absurdity. Frequent repetition, however, of the experiments to which I have alluded, left no doubt upon his mind that his conclusion that friction was uniform at all velocities was a fact which must be received as positively established; and he soon afterward boldly maintained that that which was an apparent absurdity was, instead, a necessary consequence. I well remember the ridicule that was thrown upon this view by many of those persons with whom he was associated at the time. Nevertheless, it is undoubted, that, could you practically be always applying a power in excess of the resistance, a constant increase of velocity would of necessity follow without any limit. This is so obvious to most professional men of the present day, and is now so axiomatic, that I only allude to the discussion which took place when these experiments of my father were announced for the purpose of showing how small was the amount of science at that time blended with engineering practice. A few years afterward, an excellent pamphlet was published by Mr. Silvester on this question; he took up the whole subject, and demonstrated in a very simple and beautiful manner the correctness of all the views at which my father had arrived by his course of experiments.
"The other resistances to which carriages were exposed were also investigated experimentally by my father. He perceived that these resistances were mainly three—the first being upon the axles of the carriage; the second, which may be called the rolling resistance, being between the circumference of the wheel and the surface of the rail; and the third being the resistance of gravity.
"The amount of friction and gravity he accurately ascertained; but the rolling resistance was a matter of greater difficulty, for it was subject to great variation. He, however, satisfied himself that it was so great, when the surface presented to the wheel was of a rough character, that the idea of working steam-carriages economically on common roads was out of the question. Even so early as the period alluded to he brought his theoretical calculations to a practical test; he scattered sand upon the rails when an engine was running, and found that a small quantity was quite sufficient to retard and even stop the most powerful locomotive engine that he had at that time made. And he never failed to urge this conclusive experiment upon the attention of those who were wasting their money and time upon the vain attempt to apply steam to common roads.
"The following were the principal arguments which influenced his mind to work out the use of the locomotive in a directly opposite course to that pursued by a number of ingenious inventors, who, between 1820 and 1836, were engaged in attempting to apply steam-power to turnpike roads. Having ascertained that resistance might be taken as represented by 10 lbs. to a ton weight on a level railway, it became obvious to him that so small a rise as 1 in 100 would diminish the useful effort of a locomotive by upward of fifty per cent. This fact called my father's attention to the question of gradients in future locomotive lines. He then became convinced of the vital importance, in an economical point of view, of reducing the country through which a railway was intended to pass to as near a level as possible. This originated in his mind the distinctive character of railway works as contradistinguished from all other roads; for in railroads he early contended that large sums would be wisely expended in perforating barriers of hills with long tunnels, and in raising low ground with the excess cut down from the adjacent high ground. In proportion as these views fixed themselves upon his mind, and were corroborated by his daily experience, he became more and more convinced of the hopelessness of applying steam locomotion to common roads; for every argument in favor of a level railway was an argument against the rough and hilly course of a common road. He never ceased to urge upon the patrons of road steam-carriages that if, by any amount of ingenuity, an engine could be made which could by possibility traverse a turnpike road at a speed at least equal to that obtainable by horse-power, and at a less cost, such an engine, if applied to the more perfect surface of a railway, would have its efficiency enormously enhanced. For instance, he calculated that if an engine had been constructed, and had been found to travel uniformly between London and Birmingham at an average speed of 10 miles an hour—conveying, say, 20 or 30 passengers at a cost of 1s. per mile, it was clear that the same engine, if applied to a railway, instead of conveying 20 or 30 people, would have conveyed 200 or 300 people, and instead of a speed of 10 or 12 miles an hour, a speed of at least 30 to 40 miles an hour would have been obtained."
At this day it is difficult to understand how the sagacious and strong common-sense views of Stephenson on this subject failed to force themselves sooner upon the minds of those who were persisting in their vain though ingenious attempts to apply locomotive power to ordinary roads. For a long time they continued to hold with obstinate perseverance to the belief that for such purposes a soft road was better than a hard one—a road easily crushed better than one incapable of being crushed; and they held to this after it had been demonstrated in all parts of the mining districts that iron tram-ways were better than paved roads. But the fallacy that iron was incapable of adhesion upon iron continued to prevail, and the projectors of steam-traveling on common roads only shared in the common belief. They still considered that roughness of surface was essential to produce "bite," especially in surmounting acclivities; the truth being that they confounded roughness of surface with tenacity of surface and contact of parts, not perceiving that a yielding surface which would adapt itself to the tread of the wheel could never become an unyielding surface to form a fulcrum for its progression.
Although Stephenson's locomotive engines were in daily use for many years on the Killingworth Railway, they excited comparatively little interest. They were no longer experimental, but had become an established tractive power. The experience of years had proved that they worked more steadily, drew heavier loads, and were, on the whole, considerably more economical than horses. Nevertheless, eight years passed before another locomotive railway was constructed and opened for the purposes of coal or other traffic.
It is difficult to account for this early indifference on the part of the public to the merits of the greatest mechanical invention of the age. Steam-carriages were exciting much interest, and numerous and repeated experiments were made with them. The improvements effected by M'Adam in the mode of constructing turnpike roads were the subject of frequent discussions in the Legislature, on the grants of public money being proposed, which were from time to time made to him. Yet here at Killingworth, without the aid of a farthing of government money, a system of road locomotion had been in existence since 1814, which was destined, before many years, to revolutionize the internal communications of England and of the world, but of which the English public and the English government as yet knew nothing.
But Stephenson had no means of bringing his important invention prominently under the notice of the public. He himself knew well its importance, and he already anticipated its eventual general adoption; but, being an unlettered man, he could not give utterance to the thoughts which brooded within him on the subject. Killingworth Colliery lay far from London, the centre of scientific life in England. It was visited by no savans nor literary men, who might have succeeded in introducing to notice the wonderful machine of Stephenson. Even the local chroniclers seem to have taken no notice of the Killingworth Railway. The "Puffing Billy" was doing its daily quota of hard work, and had long ceased to be a curiosity in the neighborhood. Blenkinsop's clumsier and less successful engine—which has long since been disused, while Stephenson's Killingworth engines continue working to this day—excited far more interest, partly, perhaps, because it was close to the large town of Leeds, and used to be visited by strangers as one of the few objects of interest in that place. Blenkinsop was also an educated man, and was in communication with some of the most distinguished personages of his day on the subject of his locomotive, which thus obtained considerable celebrity.
The first engine constructed by Stephenson to order, after the Killingworth model, was made for the Duke of Portland in 1817, for use upon his tram-road, about ten miles long, extending from Kilmarnock to Troon, in Ayrshire. It was employed to haul the coals from the duke's collieries along the line to Troon harbor. Its use was, however, discontinued in consequence of the frequent breakages of the cast-iron rails, by which the working of the line was interrupted, and accordingly horses were again employed as before.[50]