Part 9 (1/2)

He was one of the first to introduce steam machinery underground with the latter object. Indeed, the Killingworth mines came to be regarded as the models of the district; the working arrangements generally being conducted in a skilful and efficient manner, reflecting the highest credit on the colliery engineer.

Besides attending to the underground arrangements, the improved transit of the coals above-ground from the pithead to the s.h.i.+pping-place, demanded an increasing share of his attention. Every day's experience convinced him that the locomotive constructed by him after his patent of the year 1815, was far from perfect; though he continued to entertain confident hopes of its eventual success. He even went so far as to say that the locomotive would yet supersede every other traction-power for drawing heavy loads. Many still regarded his travelling engine as little better than a curious toy; and some, shaking their heads, predicted for it ”a terrible blow-up some day.” Nevertheless, it was daily performing its work with regularity, dragging the coal-waggons between the colliery and the staiths, and saving the labour of many men and horses. There was not, however, so marked a saving in haulage as to induce the colliery masters to adopt locomotive power generally as a subst.i.tute for horses.

How it could be improved and rendered more efficient as well as economical, was constantly present to Stephenson's mind.

At an early period of his labours, or about the time when he had completed his second locomotive, he began to direct his particular attention to the state of the Road; as he perceived that the extended use of the locomotive must necessarily depend in a great measure upon the perfection, solidity, continuity, and smoothness of the way along which the engine travelled. Even at that early period, he was in the habit of regarding the road and the locomotive as one machine, speaking of the rail and the wheel as ”man and wife.”

All railways were at that time laid in a careless and loose manner, and great inequalities of level were allowed to occur without much attention being paid to repairs. The consequence was a great loss of power, as well as much tear and wear of the machinery, by the frequent jolts and blows of the wheels against the rails. His first object therefore was, to remove the inequalities produced by the imperfect junction between rail and rail. At that time, (in 1816) the rails were made of cast iron, each rail being about three feet long; and sufficient care was not taken to maintain the points of junction on the same level. The chairs, or cast-iron pedestals into which the rails were inserted, were flat at the bottom; so that, whenever any disturbance took place in the stone blocks or sleepers supporting them, the flat base of the chair upon which the rails rested being tilted by unequal subsidence, the end of one rail became depressed, whilst that of the other was elevated. Hence constant jolts and shocks, the reaction of which very often caused the fracture of the rails, and occasionally threw the engine off the road.

To remedy this imperfection Mr. Stephenson devised a new chair, with an entirely new mode of fixing the rails therein. Instead of adopting the _b.u.t.t-joint_ which had hitherto been used in all cast-iron rails, he adopted the _half-lap joint_, by which means the rails extended a certain distance over each other at the ends, like a scarf-joint. These ends, instead of resting upon the flat chair, were made to rest upon the apex of a curve forming the bottom of the chair. The supports were also extended from three feet to three feet nine inches or four feet apart.

These rails were accordingly subst.i.tuted for the old cast-iron plates on the Killingworth Colliery Railway, and they were found to be a very great improvement upon the previous system, adding both to the efficiency of the horse-power, still employed in working the railway, and to the smooth action of the locomotive engine, but more particularly increasing the efficiency of the latter.

[Picture: Half-lap Joint]

This improved form of rail and chair was embodied in a patent taken out in the joint names of Mr. Losh, of Newcastle, iron-founder, and of Mr.

Stephenson, bearing date 30th September, 1816. Mr. Losh being a wealthy, enterprising iron-manufacturer, and having confidence in George Stephenson and his improvements, found the money for the purpose of taking out the patent, which, in those days, was a very costly as well as troublesome affair.

The specification of the same patent also described various important improvements in the locomotive itself. The wheels of the engine were improved, being altered from cast to malleable iron, in whole or in part, by which they were made lighter as well as more durable and safe. But the most ingenious and original contrivance embodied in this patent was the subst.i.tute for springs which Mr. Stephenson invented. He contrived that the steam generated in the boiler should perform this important office. The method by which this was effected displayed such genuine mechanical genius, that we would particularly call attention to the device, which was the more remarkable, as it was contrived long before the possibility of steam locomotion had become an object of general inquiry or of public interest.

It has already been observed that up to, and indeed after, the period of which we speak, there was no such cla.s.s of skilled mechanics, nor were there any such machines and tools in use, as are now available to inventors and manufacturers. Although skilled workmen were in course of gradual training in a few of the larger manufacturing towns, they did not, at the date of Stephenson's patent, exist in any considerable numbers, nor was there then any cla.s.s of mechanics capable of constructing springs of sufficient strength and elasticity to support locomotive engines of ten tons weight.

In order to avoid the dangers arising from the inequalities of the road, Stephenson so arranged the boiler of his new patent locomotive that it was supported upon the frame of the engine by four cylinders, which opened into the interior of the boiler. These cylinders were occupied by pistons with rods, which pa.s.sed downwards and pressed upon the upper side of the axles. The cylinders opening into the interior of the boiler, allowed the pressure of steam to be applied to the upper side of the piston; and the pressure being nearly equivalent to one-fourth of the weight of the engine, each axle, whatever might be its position, had at all times nearly the same amount of weight to bear, and consequently the entire weight was pretty equally distributed amongst the four wheels of the locomotive. Thus the four floating pistons were ingeniously made to serve the purpose of springs in equalising the weight, and in softening the jerks of the machine; the weight of which, it must also be observed, had been increased, on a road originally calculated to bear a considerably lighter description of carriage. This mode of supporting the engine remained in use until the progress of spring-making had so far advanced that steel springs could be manufactured of sufficient strength to bear the weight of locomotive engines.

[Picture: Old Killingworth Locomotive, still in use]

The result of the actual working of the new locomotive on the improved road amply justified the promises held forth in the specification. The traffic was conducted with greater regularity and economy, and the superiority of the engine, as compared with horse traction, became still more marked. It is a fact worthy of notice, that the identical engines constructed in 1816 after the plan above described are to this day to be seen in regular useful work upon the Killingworth Railway, conveying heavy coal-trains at the speed of between five and six miles an hour, probably as economically as any of the more perfect locomotives now in use.

Mr. Stephenson's endeavours having been attended with such marked success in the adaptation of locomotive power to railways, his attention was called by many of his friends, about the year 1818, to the application of steam to travelling on common roads. It was from this point that the locomotive started, Trevithick's first engine having been constructed with this special object. Stephenson's friends having observed how far behind he had left the original projector of the locomotive in its application to railroads, perhaps naturally inferred that he would be equally successful in applying it to the purpose for which Trevithick and Vivian had intended their first engine. But the accuracy with which he estimated the resistance to which loads were exposed on railways, arising from friction and gravity, led him at a very early stage to reject the idea of ever applying steam power economically to common-road travelling.

In October, 1818, he made a series of careful experiments in conjunction with Nicholas Wood, on the resistance to which carriages were exposed on railways, testing the results by means of a dynamometer of his own construction. The series of practical observations made by means of this instrument were interesting, as the first systematic attempt to determine the precise amount of resistance to carriages moving along railways. It was then for the first time ascertained by experiment that the friction was a constant quant.i.ty at all velocities. Although this theory had long before been developed by Vince and Coulomb, and was well known to scientific men as an established truth, yet, at the time when Stephenson made his experiments, the deductions of philosophers on the subject were neither believed in nor acted upon by practical engineers.

He ascertained that the resistances to traction were mainly three; the first being upon the axles of the carriages, the second, or rolling resistance, being between the circ.u.mference of the wheel and the surface of the rail, and the third being the resistance of gravity. The amount of friction and gravity he could accurately ascertain; but the rolling resistance was a matter of greater difficulty, being subject to much variation. He satisfied himself, however, 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 dismissed by him as entirely impracticable. Taking it as 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 upwards of 50 per cent. This was demonstrated by repeated experiments, and the important fact, thus rooted in his mind, was never lost sight of in the course of his future railway career.

It was owing in a great measure to these painstaking experiments that he early became convinced of the vital importance, in an economical point of view, of reducing the country through which a railway was intended to pa.s.s as nearly as possible to a level. Where, as in the first coal railways of Northumberland and Durham, the load was nearly all one way,-that is, from the colliery to the s.h.i.+pping-place,-it was an advantage to have an inclination in that direction. The strain on the powers of the locomotive was thus diminished, and it was easy for it to haul the empty waggons back to the colliery up even a pretty steep incline. But when the loads were both ways, he deemed it of great importance that the railroad should be constructed as nearly as possible on a level.

These views, thus early entertained, originated in Stephenson's mind the peculiar character of railroad works as distinguished from other roads; for, in railways, he early contended that large sums would be wisely expended in perforating barriers of hills with long tunnels, and in raising the lower levels with the excess cut down from the adjacent high ground. In proportion as these views forced 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 favour of a level railway was, in his view, an argument against the rough and hilly course of a common road.

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 pa.s.sed before another locomotive railway was constructed and opened for the purposes of coal or other traffic.

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 antic.i.p.ated 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.

There seemed, indeed, to be so small a prospect of introducing the locomotive into general use, that Stephenson,-perhaps feeling the capabilities within him,-again recurred to his old idea of emigrating to the United States. Before joining Mr. Burrel as partner in a small foundry at Forth Banks, Newcastle, he had thrown out to him the suggestion that it would be a good speculation for them to emigrate to North America, and introduce steamboats upon the great inland lakes there. The first steamers were then plying upon the Tyne before his eyes; and he saw in them the germ of a great revolution in navigation.

It occurred to him that North America presented the finest field for trying their wonderful powers. He was an engineer, his partner was an iron-founder; and between them he thought they might strike out a path to fortune in the mighty West. Fortunately, this idea remained a mere speculation so far as Stephenson was concerned: and it was left to others to do what he had dreamt of achieving. After all his patient waiting, his skill, industry, and perseverance were at length about to bear fruit.

In 1819 the owners of the Hetton Colliery, in the county of Durham, determined to have their waggon-way altered to a locomotive railroad.

The result of the working of the Killingworth Railway had been so satisfactory, that they resolved to adopt the same system. One reason why an experiment so long continued and so successful as that at Killingworth should have been so slow in producing results, perhaps was, that to lay down a railway and furnish it with locomotives, or fixed engines where necessary, required a very large capital, beyond the means of ordinary coal-owners; whilst the small amount of interest felt in railways by the general public, and the supposed impracticability of working them to a profit, as yet prevented ordinary capitalists from venturing their money in the promotion of such undertakings. The Hetton Coal Company were, however, possessed of adequate means; and the local reputation of the Killingworth engine-wright pointed him out as the man best calculated to lay out their line, and superintend their works. They accordingly invited him to act as the engineer of the proposed railway, which was to be the longest locomotive line that had, up to that time, been constructed. It extended from the Hetton Colliery, situated about two miles south of Houghton-le-Spring, in the county of Durham, to the s.h.i.+pping-places on the banks of the Wear, near Sunderland. Its length was about eight miles; and in its course it crossed Warden Law, one of the highest hills in the district. The character of the country forbade the construction of a flat line, or one of comparatively easy gradients, except by the expenditure of a much larger capital than was placed at the engineer's disposal. Heavy works could not be executed; it was therefore necessary to form the line with but little deviation from the natural conformation of the district which it traversed, and also to adapt the mechanical methods employed for its working to the character of the gradients, which in some places were necessarily heavy.

Although Stephenson had, with every step made towards its increased utility, become more and more identified with the success of the locomotive engine, he did not allow his enthusiasm to carry him away into costly mistakes. He carefully drew the line between the cases in which the locomotive could be usefully employed, and those in which stationary engines were calculated to be more economical. This led him, as in the instance of the Hetton Railway, to execute lines through and over rough countries, where gradients within the powers of the locomotive engine of that day could not be secured, employing in their stead stationary engines where locomotives were not practicable. In the present case, this course was adopted by him most successfully. On the original Hetton line, there were five self-acting inclines,-the full waggons drawing the empty ones up,-and two inclines worked by fixed reciprocating engines of sixty horse power each. The locomotive travelling engine, or ”the iron horse,” as the people of the neighbourhood then styled it, did the rest.

On the day of the opening of the Hetton Railway, the 18th November, 1822, crowds of spectators a.s.sembled from all parts to witness the first operations of this ingenious and powerful machinery, which was entirely successful. On that day five of Stephenson's locomotives were at work upon the railway, under the direction of his brother Robert; and the first s.h.i.+pment of coal was then made by the Hetton Company, at their new staiths on the Wear. The speed at which the locomotives travelled was about 4 miles an hour, and each engine dragged after it a train of 17 waggons, weighing about 64 tons.