Lives of the Engineers Part 7

Trevithick himself seems from this time to have taken no further steps to bring the locomotive into general use. We find him, shortly after, engaged upon schemes of a more promising character, abandoning the engine to other mechanical inventors, though little improvement was made in it for several years. An imaginary difficulty seems to have tended, amongst other obstacles, to prevent its adoption; viz., the idea that, if a heavy weight were placed behind the engine, the "grip" or "bite" of its smooth wheels upon the equally smooth iron rail, must necessarily be so slight that they would whirl round upon it, and, consequently, that the machine would not make progress. Hence Trevithick, in his patent, provided that the periphery of the driving-wheels should be made rough by the projection of bolts or cross-grooves, so that the adhesion of the wheels to the road might be secured.

Following up the presumed necessity for a more effectual adhesion between the wheels and the rails, Mr. Blenkinsop of Leeds, in 1811, took out a patent for a racked or tooth-rail laid along one side of the road, into which the toothed-wheel of his locomotive worked as pinions work into a rack. The boiler of his engine was supported by a carriage with four wheels without teeth, and rested immediately upon the axles. These wheels were entirely independent of the working parts of the engine, and therefore merely supported its weight upon the rails, the progress being effected by means of the cogged-wheel working into the cogged-rail. The engine had two cylinders, instead of one as in Trevithick's engine. The invention of the double cylinder was due to Matthew Murray, of Leeds, one of the best mechanical engineers of his time; Mr. Blenkinsop, who was not a mechanic, having consulted him as to all the practical arrangements.

The connecting-rods gave the motion to two pinions by cranks at right angles to each other; these pinions communicating the motion to the wheel which worked into the cogged-rail.

Mr. Blenkinsop's engines began running on the railway from the Middleton Collieries to Leeds, about 3 miles, on the 12th of August, 1812. They continued for many years to be one of the princ.i.p.al curiosities of the place, and were visited by strangers from all parts. In 1816, the Grand Duke Nicholas (afterwards Emperor) of Russia observed the working of Blenkinsop's locomotive with curious interest and admiration. An engine dragged as many as thirty coal-waggons at a speed of about 3 miles per hour. These engines continued for many years to be thus employed in the haulage of coal, and furnished the first instance of the regular employment of locomotive power for commercial purposes.

The Messrs. Chapman, of Newcastle, in 1812, endeavoured to overcome the same fict.i.tious difficulty of the want of adhesion between the wheel and the rail, by patenting a locomotive to work along the road by means of a chain stretched from one end of it to the other. This chain was pa.s.sed once round a grooved barrel-wheel under the centre of the engine: so that, when the wheel turned, the locomotive, as it were, dragged itself along the railway. An engine, constructed after this plan, was tried on the Heaton Railway, near Newcastle; but it was so clumsy in its action, there was so great a loss of power by friction, and it was found to be so expensive and difficult to keep in repair, that it was soon abandoned.

Another remarkable expedient was adopted by Mr. Brunton, of the b.u.t.terley Works, Derbyshire, who, in 1813, patented his Mechanical Traveller, to go _upon legs_ working alternately like those of a horse. {73} But this engine never got beyond the experimental state, for, at its very first trial, the driver, to make sure of a good start, overloaded the safety-valve, when the boiler burst and killed a number of the bystanders, wounding many more. These, and other contrivances with the same object, projected about the same time, show that invention was actively at work, and that many minds were anxiously labouring to solve the important problem of locomotive traction upon railways.

But the difficulties contended with by these early inventors, and the step-by-step progress which they made, will probably be best ill.u.s.trated by the experiments conducted by Mr. Blackett, of Wylam, which are all the more worthy of notice, as the persevering efforts of this gentleman in a great measure paved the way for the labours of George Stephenson, who, shortly after, took up the question of steam locomotion, and brought it to a successful issue.

The Wylam waggon-way is one of the oldest in the north of England. Down to the year 1807 it was formed of wooden spars or rails, laid down between the colliery at Wylam-where old Robert Stephenson had worked-and the village of Lemington, some four miles down the Tyne, where the coals were loaded into keels or barges, and floated down past Newcastle, to be shipped for London. Each chaldron-waggon had a man in charge of it, and was originally drawn by one horse. The rate at which the waggons were hauled was so slow that only two journeys were performed by each man and horse in one day, and three on the day following. This primitive waggon-way pa.s.sed, as before stated, close in front of the cottage in which George Stephenson was born; and one of the earliest sights which met his infant eyes was this wooden tramroad worked by horses.

Mr. Blackett was the first colliery owner in the North who took an active interest in the locomotive. Having formed the acquaintance of Trevithick in London, and inspected the performances of his engine, he determined to repeat the Pen-y-darran experiment upon the Wylam waggon-way. He accordingly obtained from Trevithick, in October, 1804, a plan of his engine, provided with "friction-wheels," and employed Mr. John Whinfield, of Pipewellgate, Gateshead, to construct it at his foundry there. The engine was constructed under the superintendence of one John Steele, an ingenious mechanic who had been in Wales, and worked under Trevithick in fitting the engine at Pen-y-darran. When the Gateshead locomotive was finished, a temporary way was laid down in the works, on which it was run backwards and forwards many times. For some reason, however-it is said because the engine was deemed too light for drawing the coal-trains-it never left the works, but was dismounted from the wheels, and set to blow the cupola of the foundry, in which service it long continued to be employed.

Several years elapsed before Mr. Blackett took any further steps to carry out his idea. The final abandonment of Trevithick's locomotive at Pen-y-darran perhaps contributed to deter him from proceeding further; but he had the wooden tramway taken up in 1808, and a plate-way of cast-iron laid down instead-a single line furnished with sidings to enable the laden waggons to pa.s.s the empty ones. The new iron road proved so much smoother than the old wooden one, that a single horse, instead of drawing one, was now enabled to draw two, or even three, laden waggons.

Encouraged by the success of Mr. Blenkinsop's experiment at Leeds, Mr.

Blackett determined to follow his example; and in 1812 he ordered a second engine, to work with a toothed driving-wheel upon a rack-rail.

This locomotive was constructed by Thomas Waters, of Gateshead, under the superintendence of Jonathan Foster, Mr. Blackett's princ.i.p.al engine-wright. It was a combination of Trevithick's and Blenkinsop's engines; but it was of a more awkward construction than either. The boiler was of cast-iron. The engine was provided with a single cylinder six inches in diameter, with a fly-wheel working at one side to carry the crank over the dead points. Jonathan Foster described it to the author in 1854, as "a strange machine, with lots of pumps, cog-wheels, and plugs, requiring constant attention while at work." The weight of the whole was about six tons.

When finished, it was conveyed to Wylam on a waggon, and there mounted upon a wooden frame supported by four pairs of wheels, which had been constructed for its reception. A barrel of water, placed on another frame upon wheels, was attached to it as a tender. After a great deal of labour, the c.u.mbrous machine was got upon the road. At first it would not move an inch. Its maker, Tommy Waters, became impatient, and at length enraged, and taking hold of the lever of the safety valve, declared in his desperation, that "either _she_ or _he_ should go." At length the machinery was set in motion, on which, as Jonathan Foster described to the author "she flew all to pieces, and it was the biggest wonder i' the world that we were not all blewn up." The incompetent and useless engine was declared to be a failure; it was shortly after dismounted and sold; and Mr. Blackett's praiseworthy efforts thus far proved in vain.

He was still, however, desirous of testing the practicability of employing locomotive power in working the coal down to Lemington, and he determined on another trial. He accordingly directed his engine-wright to proceed with the building of a third engine in the Wylam workshops.

This new locomotive had a single 8-inch cylinder, was provided with a fly-wheel like its predecessor, and the driving-wheel was cogged on one side to enable it to travel in the rack-rail laid along the road. This engine proved more successful than the former one; and it was found capable of dragging eight or nine loaded waggons, though at the rate of little more than a mile an hour, from the colliery to the shipping-place.

It sometimes took six hours to perform the journey of five miles. Its weight was found too great for the road, and the cast-iron plates were constantly breaking. It was also very apt to get off the rack-rail, and then it stood still. The driver was one day asked how he got on? "Get on?" said he, "we don't get on; we only get off!" On such occasions, horses had to be sent to drag the waggons as before, and others to haul the engine back to the work-shops. It was constantly getting out of order; its plugs, pumps, or cranks, got wrong; it was under repair as often as at work; at length it became so cranky that the horses were usually sent out after it to drag it when it gave up; and the workmen generally declared it to be a "perfect plague." Mr. Blackett did not obtain credit amongst his neighbours for these experiments. Many laughed at his machines, regarding them only in the light of crotchets,-frequently quoting the proverb that "a fool and his money are soon parted." Others regarded them as absurd innovations on the established method of hauling coal; and p.r.o.nounced that they would "never answer."

Notwithstanding, however, the comparative failure of this second locomotive, Mr. Blackett persevered with his experiments. He was zealously a.s.sisted by Jonathan Foster the engine-wright, and William Hedley, the viewer of the colliery, a highly ingenious person, who proved of great use in carrying out the experiments to a successful issue. One of the chief causes of failure being the rack-rail, the idea occurred to Mr. Hedley that it might be possible to secure adhesion enough between the wheel and the rail by the mere weight of the engine, and he proceeded to make a series of experiments for the purpose of determining this problem. He had a frame placed on four wheels, and fitted up with windla.s.ses attached by gearing to the several wheels. The frame having been properly weighted, six men were set to work the windla.s.ses; when it was found that the adhesion of the smooth wheels on the smooth rails was quite sufficient to enable them to propel the machine without slipping.

Having found the proportion which the power bore to the weight, he demonstrated by successive experiments that the weight of the engine would of itself produce sufficient adhesion to enable it to draw upon a smooth railroad the requisite number of waggons in all kinds of weather.

And thus was the fallacy which had heretofore prevailed on this subject completely exploded, and it was satisfactorily proved that rack-rails, toothed wheels, endless chains, and legs, were alike unnecessary for the efficient traction of loaded waggons upon a moderately level road.

From this time forward considerably less difficulty was experienced in working the coal trains upon the Wylam tramroad. At length the rack-rail was dispensed with. The road was laid with heavier rails; the working of the old engine was improved; and a new engine was shortly after built and placed upon the road, still on eight wheels, driven by seven rack-wheels working inside them-with a wrought-iron boiler through which the flue was returned so as largely to increase the heating surface, and thus give increased power to the engine.

[Picture: Improved Wylam Engine]

As may readily be imagined, the jets of steam from the piston, blowing off into the air at high pressure while the engine was in motion, caused considerable annoyance to horses pa.s.sing along the Wylam road, at that time a public highway. The nuisance was felt to be almost intolerable, and a neighbouring gentleman threatened to have it put down. To diminish the noise as much as possible, Mr. Blackett gave orders that so soon as any horse, or horses, came in sight, the locomotive was to be stopped, and the frightful blast of the engine thus suspended until the pa.s.sing animals had got out of hearing. Much interruption was thus caused to the working of the railway, and it excited considerable dissatisfaction amongst the workmen. The following plan was adopted to abate the nuisance: a reservoir was provided immediately behind the chimney (as shown in the preceding cut) into which the waste steam was thrown after it had performed its office in the cylinder; and from this reservoir, the steam gradually escaped into the atmosphere without noise.

While Mr. Blackett was thus experimenting and building locomotives at Wylam, George Stephenson was anxiously studying the same subject at Killingworth. He was no sooner appointed engine-wright of the collieries than his attention was directed to the means of more economically hauling the coal from the pits to the river-side. We have seen that one of the first important improvements which he made, after being placed in charge of the colliery machinery, was to apply the surplus power of a pumping steam-engine, fixed underground, to drawing the coals out of the deeper workings of the Killingworth mines,-by which he succeeded in effecting a large reduction in the expenditure on manual and horse labour.

The coals, when brought above ground, had next to be laboriously dragged by horses to the shipping staiths on the Tyne, several miles distant.

The adoption of a tramroad, it is true, had tended to facilitate their transit. Nevertheless the haulage was both tedious and costly. With the view of economising labour, Stephenson laid down inclined planes where the nature of the ground would admit of this expedient. Thus, a train of full waggons let down the incline by means of a rope running over wheels laid along the tramroad, the other end of which was attached to a train of empty waggons placed at the bottom of the parallel road on the same incline, dragged them up by the simple power of gravity. But this applied only to a comparatively small part of the road. An economical method of working the coal trains, instead of by horses,-the keep of which was at that time very costly, from the high price of corn,-was still a great desideratum; and the best practical minds in the collieries were actively engaged in the attempt to solve the problem.

In the first place Stephenson resolved to make himself thoroughly acquainted with what had already been done. Mr. Blackett's engines were working daily at Wylam, past the cottage where he had been born; and thither he frequently went to inspect the improvements made by Mr.

Blackett from time to time both in the locomotive and in the plateway along which it worked. Jonathan Foster informed us that, after one of these visits, Stephenson declared to him his conviction that a much more effective engine might be made, that should work more steadily and draw the load more effectively.

He had also the advantage, about the same time, of seeing one of Blenkinsop's Leeds engines, which was placed on the tramway leading from the collieries of Kenton and c.o.xlodge, on the 2nd September, 1813. This locomotive drew sixteen chaldron waggons containing an aggregate weight of seventy tons, at the rate of about three miles an hour. George Stephenson and several of the Killingworth men were amongst the crowd of spectators that day; and after examining the engine and observing its performances, he observed to his companions, that "he thought he could make a better engine than that, to go upon legs." Probably he had heard of the invention of Brunton, whose patent had by this time been published, and proved the subject of much curious speculation in the colliery districts. Certain it is, that, shortly after the inspection of the c.o.xlodge engine, he contemplated the construction of a new locomotive, which was to surpa.s.s all that had preceded it. He observed that those engines which had been constructed up to this time, however ingenious in their arrangements, had proved practical failures. Mr.

Blackett's was as yet both clumsy and expensive. Chapman's had been removed from the Heaton tramway in 1812, and was regarded as a total failure. And the Blenkinsop engine at c.o.xlodge was found very unsteady and costly in its working; besides, it pulled the rails to pieces, the entire strain being upon the rack-rail on one side of the road. The boiler, however, having soon after blown up, there was an end of that engine; and the colliery owners did not feel encouraged to try any further experiment.

An efficient and economical working locomotive, therefore, still remained to be invented; and to accomplish this object Mr. Stephenson now applied himself. Profiting by what his predecessors had done, warned by their failures and encouraged by their partial successes, he commenced his labours. There was still wanting the man who should accomplish for the locomotive what James Watt had done for the steam-engine, and combine in a complete form the best points in the separate plans of others, embodying with them such original inventions and adaptations of his own as to ent.i.tle him to the merit of inventing the working locomotive, in the same manner as James Watt is to be regarded as the inventor of the working condensing-engine. This was the great work upon which George Stephenson now entered, though probably without any adequate idea of the ultimate importance of his labours to society and civilization.

He proceeded to bring the subject of constructing a "Travelling Engine,"

as he then denominated the locomotive, under the notice of the lessees of the Killingworth Colliery, in the year 1813. Lord Ravensworth, the princ.i.p.al partner, had already formed a very favourable opinion of the new engine-wright, from the improvements which he had effected in the colliery engines, both above and below ground; and, after considering the matter, and hearing Stephenson's explanations, he authorised him to proceed with the construction of a locomotive,-though his lordship was, by some, called a fool for advancing money for such a purpose. "The first locomotive that I made," said Stephenson, many years after, {82} when speaking of his early career at a public meeting in Newcastle, "was at Killingworth Colliery, and with Lord Ravensworth's money. Yes; Lord Ravensworth and partners were the first to entrust me, thirty-two years since, with money to make a locomotive engine. I said to my friends, there was no limit to the speed of such an engine, if the works could be made to stand."

Our engine-wright had, however, many obstacles to encounter before he could get fairly to work with the erection of his locomotive. His chief difficulty was in finding workmen sufficiently skilled in mechanics, and in the use of tools, to follow his instructions and embody his designs in a practical shape. The tools then in use about the collieries were rude and clumsy; and there were no such facilities as now exist for turning out machinery of an entirely new character. Stephenson was under the necessity of working with such men and tools as were at his command; and he had in a great measure to train and instruct the workmen himself. The engine was built in the workshops at the West Moor, the leading mechanic employed being the colliery blacksmith, an excellent workman in his way, though quite new to the work now entrusted to him.

In this first locomotive constructed at Killingworth, Stephenson to some extent followed the plan of Blenkinsop's engine. The boiler was cylindrical, of wrought iron, 8 feet in length and 34 inches in diameter, with an internal flue-tube 20 inches wide pa.s.sing through it. The engine had two vertical cylinders of 8 inches diameter, and 2 feet stroke, let into the boiler, working the propelling gear with cross heads and connecting rods. The power of the two cylinders was combined by means of spurwheels, which communicated the motive power to the wheels supporting the engine on the rail, instead of, as in Blenkinsop's engine, to cogwheels which acted on the cogged rail independent of the four supporting wheels. The engine thus worked upon what is termed the second motion. The chimney was of wrought iron, round which was a chamber extending back to the feed-pumps, for the purpose of heating the water previous to its injection into the boiler. The engine had no springs, and was mounted on a wooden frame supported on four wheels. In order to neutralise as much as possible the jolts and shocks which such an engine would necessarily encounter from the obstacles and inequalities of the then very imperfect plateway, the water-barrel which served for a tender was fixed to the end of a lever and weighted, the other end of the lever being connected with the frame of the locomotive carriage. By this means the weight of the two was more equally distributed, though the contrivance did not by any means compensate for the absence of springs.

[Picture: The Spur-gear]

The wheels of the locomotive were all smooth, Mr. Stephenson having satisfied himself by experiment that the adhesion between the wheels of a loaded engine and the rail would be sufficient for the purpose of traction. Robert Stephenson informed us that his father caused a number of workmen to mount upon the wheels of a waggon moderately loaded, and throw their entire weight upon the spokes on one side, when he found that the waggon could thus be easily propelled forward without the wheels slipping. This, together with other experiments, satisfied him of the expediency of adopting smooth wheels on his engine, and it was so finished accordingly.

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 placed upon the Killingworth Railway on the 25th 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.

Although a considerable advance upon previous locomotives, "Blutcher" (as the engine was popularly called) was nevertheless a somewhat c.u.mbrous and clumsy machine. The parts were huddled together. The boiler const.i.tuted the princ.i.p.al 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 cogwheels became at all worn, a rattling noise was produced during the travelling of the engine.

As the princ.i.p.al 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 four miles an hour. The result was anything but decisive; and the locomotive might have been condemned as useless, had not our engineer at this juncture applied the steam-blast, and by its means carried his experiment to a triumphant issue.

The steam, after performing its duty in the cylinders, was at first allowed to escape into the open atmosphere with a hissing blast, to the terror of horses and cattle. It was complained of as a nuisance; and an action at law against the colliery lessees was threatened unless it was stopped. Stephenson's attention had been drawn to the much greater velocity with which the steam issued from the exit pipe compared with that at which the smoke escaped from the chimney. He conceived that, by conveying the eduction steam into the chimney, by means of a small pipe, after it had performed its office in the cylinders, 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 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 has in a great measure been the result of its adoption. Without the steam-blast, by means of which the intensity of combustion is maintained at its highest point, producing a correspondingly rapid evolution of steam, high rates of speed could not have been kept up; the advantages of the multi-tubular boiler (afterwards invented) could never have been fairly tested; 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 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 spur-wheels 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 pair of connecting rods. But in attempting to establish a direct communication between the cylinders and the wheels that rolled upon the rails, considerable difficulties presented themselves. The ordinary joints could not be employed to unite the parts of the engine, which was a rigid ma.s.s, with the wheels lolling upon the irregular surface of the rails; for it was evident that the two rails of the line of way-more especially in those early days of imperfect construction of the permanent road-could not always be maintained at the same level,-that the wheel at one end of the axle might be depressed into one part of the line which had subsided, whilst the other wheel would be comparatively elevated; and in such a position of the axle and wheels, it was obvious that a rigid communication between the cross head and the wheels was impracticable. Hence it became necessary to form a joint at the top of the piston-rod where it united with the cross head, so as to permit the cross head to preserve complete parallelism with the axle of the wheels with which it was in communication.

In order to obtain that degree of flexibility combined with direct action, which was essential for ensuring power and avoiding needless friction and jars from irregularities in the road, Stephenson made use of the "ball and socket" joint for effecting a union between the ends of the cross heads where they united with the connecting rods, and between the ends of the connecting rods where they were united with the crank-pins attached to each driving-wheel. By this arrangement the parallelism between the cross head and the axle was at all times maintained and preserved, without producing any serious jar or friction on any part of the machine. Another important point was, to combine each pair of wheels by means of some simple mechanism instead of by the cogwheels which had formerly been used. And, with this object, Stephenson made cranks in each axle at right angles to each other, with rods communicating horizontally between them.

A locomotive was constructed upon this plan in 1815, and was found to answer extremely well. But at that period the mechanical skill of the country was not equal to forging cranked axles of the soundness and strength necessary to stand the jars incident to locomotive work.

Stephenson was accordingly compelled to fall back upon a subst.i.tute, which, although less simple and efficient, was within the mechanical capabilities of the workmen of that day, in respect of construction as well as repair. He adopted a chain which rolled over indented wheels placed on the centre of each axle, and was so arranged that the two pairs of wheels were effectually coupled and made to keep pace with each other.

The chain, however, after a few years' use, became stretched; and then the engines were liable to irregularity in their working, especially in changing from working back to working forward again. Eventually the chain was laid aside, and the front and hind wheels were united by rods on the outside, instead of by rods and crank axles inside, as specified in the original patent. This expedient completely answered the purpose required, without involving any expensive or difficult workmanship.

Thus, in 1815, by dint of patient and persevering labour,-by careful observation of the works of others, and never neglecting to avail himself of their suggestions,-Stephenson succeeded in manufacturing an engine which included the following important improvements on all previous attempts in the same direction:-viz., simple and direct communication between the cylinders and the wheels rolling upon the rails; joint adhesion of all the wheels, attained by the use of horizontal connecting-rods; and finally, a beautiful method of exciting the combustion of the fuel by employing the waste steam, which had formerly been allowed to escape uselessly into the air. Although many improvements in detail were afterwards introduced in the locomotive by George Stephenson himself, as well as by his equally distinguished son, it is perhaps not too much to say that this engine, as a mechanical contrivance, contained the germ of all that has since been effected. It may in fact be regarded as the type of the present locomotive engine.

CHAPTER VI.

INVENTION OF THE "GEORDY" SAFETY-LAMP.

Explosions of fire-damp were unusually frequent in the coal mines of Northumberland and Durham about the time when George Stephenson was engaged in the construction of his first locomotives. These explosions were often attended with fearful loss of life and dreadful suffering to the workpeople. Killingworth Colliery was not free from such deplorable calamities; and during the time that Stephenson was employed as a brakesman at the West Moor, several "blasts" took place in the pit, by which many workmen were scorched and killed, and the owners of the colliery sustained heavy losses. One of the most serious of these accidents occurred in 1806, not long after he had been appointed brakesman, by which 10 persons were killed. Stephenson was working at the mouth of the pit at the time, and the circ.u.mstances connected with the accident made a deep impression on his mind.

Another explosion took place in the same pit in 1809, by which 12 persons lost their lives. The blast did not reach the shaft as in the former case; the unfortunate persons in the pit having been suffocated by the after-damp. More calamitous still were the explosions which took place in the neighbouring collieries; one of the worst being that of 1812, in the Felling Pit, near Gateshead, by which no fewer than 90 men and boys were suffocated or burnt to death. And a similar accident occurred in the same pit in the year following, by which 22 persons perished.

It was natural that George Stephenson should devote his attention to the causes of these deplorable accidents, and to the means by which they might if possible be prevented. His daily occupation led him to think much and deeply on the subject. As engine-wright of a colliery so extensive as that of Killingworth, where there were nearly 160 miles of gallery excavation, in which he personally superintended the working of the inclined planes along which the coals were sent to the pit entrance, he was necessarily very often underground, and brought face to face with the dangers of fire-damp. From fissures in the roofs of the galleries, carburetted hydrogen gas was constantly flowing; in some of the more dangerous places it might be heard escaping from the crevices of the coal with a hissing noise. Ventilation, firing, and all conceivable modes of drawing out the foul air had been adopted, and the more dangerous parts of the galleries were built up. Still the danger could not be wholly prevented. The miners must necessarily guide their steps through the extensive underground ways with lighted lamps or candles, the naked flame of which, coming in contact with the inflammable air, daily exposed them and their fellow-workers in the pit to the risk of death in one of its most dreadful forms.

One day, in 1814, a workman hurried into Stephenson's cottage with the startling information that the deepest main of the colliery was on fire!

He immediately hastened to the pit-head, about a hundred yards off, whither the women and children of the colliery were running, with wildness and terror depicted in every face. In a commanding voice Stephenson ordered the engineman to lower him down the shaft in the corve. There was peril, it might be death, before him, but he must go.