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CHAPTER V.

THE LOCOMOTIVE ENGINE—GEORGE STEPHENSON BEGINS ITS IMPROVEMENT.

    THE rapid increase in the coal-trade of the Tyne about the beginning of the present century had the effect of stimulating the ingenuity of mechanics, and encouraging them to devise improved methods of transporting the coal from the pits to the shipping-places.  From our introductory chapter, it will have been observed that the improvements which had thus far been effected were confined almost entirely to the road.  The railway wagons still continued to be drawn by horses.  By improving and flattening the tram-way, considerable economy in horse-power had been secured; but, unless some more effective method of mechanical traction could be devised, it was clear that railway improvement had almost reached its limits.

    Notwithstanding Trevithick's comparatively successful experiment with the first railway locomotive on the Merthyr Tydvil tram-road in 1804, described in a former chapter, he seems to have taken no farther steps to bring his invention into notice.  He was probably discouraged by the breakage of the cast-iron plates, of which the road was formed, which were crushed under the load of his engine, and could not induce the owners of the line to relay it with better materials so as to give his locomotive a fair trial.

    An imaginary difficulty, also, seems to have tended, among other obstacles, to prevent the adoption of the locomotive, 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 any progress. [p.152]  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 thereby be better secured.

    Trevithick himself does not seem to have erected another engine, but we gather from the evidence given by Mr. Bastrick in the committee on the Liverpool and Manchester Bill in 1825, that ten or twelve years before that time he had made an engine for Trevithick after his patent, and that the engine was exhibited in London.  "A circular railroad was laid down," said Mr. Bastrick, and it was stated that this engine was to run against a horse, and that which went a sufficient number of miles was to win.  It is not known what afterward became of this engine. [Ed.—see p.86.]

    There were, however, at a much earlier period, several wealthy and enterprising men, both in Yorkshire and Northumberland, who were willing to give the locomotive a fair trial; and had Trevithick but possessed the requisite tenacity of purpose—had he not been too soon discouraged by partially successful experiments—he might have risen to both fame and fortune, not only as the inventor of the locomotive, but as the practical introducer of railway locomotion.

    One of Trevithick's early friends and admirers was Mr. Blackett, of Wylam.  The Wylam wagon-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 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-wagon had a man in charge of it, and was originally drawn by one horse.  The rate at which the wagons 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 wagon-way passed, 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 tram-road worked by horses.

    Mr. Blackett was the first colliery owner in the North who took an active interest in the locomotive.  He had witnessed the first performances of Trevithick's steam-carriage in London, and was so taken with the idea of its application to railway locomotion that he resolved to have an engine erected after the new patent for use upon his tram-way at Wylam.  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 made under the superintendence of one John Steele, [p.154] 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 backward and forward many times.  For some reason or other, however—it is said because the engine was 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 farther steps to carry out his idea.  The final abandonment of Trevithick's locomotive at Pen-y-darran perhaps contributed to deter him from proceeding farther; but he had the Wylam wooden tram-way taken up in 1808, and a plate-way of cast iron laid down instead—a single line furnished with sidings to enable the laden wagons to pass 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 enabled to draw two, or even three laden wagons.

    Although the locomotive seemed about to be lost sight of, it was not forgotten.  In 1811, Mr. Blenkinsop, the manager of the Middleton Collieries, near Leeds, revived the idea of employing it in lieu of horses to haul the coals along his tram-way.  Mr. Blenkinsop, in the patent which he took out for his proposed engine, followed in many respects the design of Trevithick; but, with the help of Matthew Murray, of Leeds, one of the most ingenious mechanics of his day, he introduced several important and valuable modifications.  Thus he employed two cylinders of 8 in. diameter instead of one, as in Trevithick's engine.  These cylinders were placed vertically, and immersed for more than half their length in the steam space of the boiler.  The eduction pipes met in a single tube at the top, and threw the steam into the air.  The boiler was cylindrical in form, but of cast iron.  It had one flue, the fire being at one end and the chimney at the other. The engine was supported on a carriage without springs, resting directly upon two pairs of wheels and axles unconnected with the working parts, and which merely served to carry the engine upon the rails.  The motion was effected in this way: the piston-rods, by means of cross-heads, worked the connecting-rods, which came down to two cranks on each side below the boiler, placed at right angles in order to pass their centres with certainty.  These cranks worked two shafts fixed across the engine, on which were small-toothed wheels working into a larger one between them; and on the axis of this large wheel, outside the framing, were the driving-wheels, one of which was toothed, and worked into a rack on one side of the railway.

    It will be observed that the principal new features in this engine were the two cylinders and the toothed-wheel working into a rack-rail.  Mr. Blenkinsop contrived the latter expedient in order to insure sufficient adhesion between the wheel and the road, supposing that smooth wheels and smooth rails would be insufficient for the purpose.  Clumsy and slow though the engine was compared with modem locomotives, it was nevertheless a success.  It was the first engine that plied regularly upon any railway, doing useful work; and it continued so employed for more than twenty years.  What was more, it was a commercial success, for its employment was found to be economical compared with horse-power.  In a letter to Sir John Sinclair, Mr. Blenkinsop stated that his engine weighed five tons; consumed two thirds of a hundred weight of coals and fifty gallons of water per hour; drew twenty-seven wagons, weighing ninety-four tons, on a dead level, at three and a half miles an hour, or fifteen tons up an ascent of 2 in. in the yard; that when "lightly loaded" it travelled at a speed of ten miles an hour; that it did the work of sixteen horses in twelve hours; and that its cost was £400.  Such was Mr. Blenkinsop's own account of the performances of his engine, which was for a long time regarded as one of the wonders of the neighbourhood. [p.156]

    The Messrs. Chapman, of Newcastle, in 1812 endeavoured to overcome the same fictitious 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 passed 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 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 very soon abandoned.  Another remarkable expedient was adopted by Mr. Brunton, of the Butterley Works, Derbyshire, who in 1813 patented his Mechanical Traveller, to go upon legs working alternately like those of a horse. [p.157]  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 busily at work, and that many minds were anxiously labouring to solve the problem of steam locomotion on railways.

    Mr. Blackett, of Wylam, was encouraged by the success of Mr. Blenkinsop's experiment, and again he resolved to make a trial of the locomotive upon his wagon-way.  Accordingly, in 1812, he ordered a second engine, which was so designed as to work with a toothed driving-wheel upon a rack-rail as at Leeds.  This locomotive was constructed by Thomas Waters, of Gateshead, under the superintendence of Jonathan Foster, Mr. Blackett's principal engine-wright.  It was a combination of Trevithick's and Blenkinsop's engines; but it was of a more awkward construction than either.  Like Trevithick's, it had a single cylinder with a fly-wheel, which Blenkinsop had discarded.  The boiler was of cast iron.  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 wagon, 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 cumbrous 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 praise-worthy 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 making yet another trial.  He accordingly directed his engine-wright, Jonathan Foster, 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.  The engine proved more successful than the former one, and it was found capable of dragging eight or nine loaded wagons, 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 out to drag the wagons as before, and others to haul the engine back to the workshops.  It was constantly getting out of order; its plugs, pumps, or cranks got wrong, and it was under repair as often as at work.  At length it became so cranky that the horses were usually sent after it to drag it along when it gave up, and the workmen generally declared it to be a "perfect plague."  Mr. Blackett did not obtain credit among his neighbours for these experiments.  Many laughed at his machines, regarding them only in the light of crotchets—frequently quoting the proverb of "a fool and his money are soon parted."  Others regarded them as absurd innovations on the established method of hauling coal, and pronounced that they would "never answer."

    Notwithstanding, however, the comparative failure of the second locomotive, Mr. Blackett persevered with his experiments.  He was zealously assisted 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 sufficient adhesion 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 windlasses attached by gearing to the several wheels.  The frame having been properly weighted, six men were set to work the windlasses, 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 then 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 wagons 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 wagons upon a moderately level road. [160-1]

    From this time forward, considerably less difficulty was experienced in working the coal-trains upon the Wylam tram-road.  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. [p.160-2]  Below is a representation of this 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 passing 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 vehicle drawn by horses, came in sight, the locomotive was to be stopped, and the frightful blast of the engine thus suspended until the passing animals had got out of sight.  Much interruption was thus caused to the working of the railway, and it excited considerable dissatisfaction among the workmen.  The following plan was adopted to abate the nuisance: a reservoir was provided immediately behind the chimney (as shown in the opposite 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.  This arrangement was devised with the express object of preventing a blast in the chimney, the value of which, as we shall subsequently find, was not detected until George Stephenson, adopting it with a preconceived design and purpose, demonstrated its importance and value—as being, in fact, the very life-breath of the locomotive engine.

    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, for the purpose of 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 means of horses to the shipping staiths on the Tyne, several miles distant.  The adoption of a tram-road, it is true, had tended to facilitate their transit; nevertheless, the haulage was both tedious and expensive.  With the view of economizing labour, Stephenson laid down inclined planes where the nature of the ground would admit of this expedient being adopted.  Thus a train of full wagons let down the incline by means of a rope running over wheels laid along the tram-road, the other end of which was attached to a train of empty wagons 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 means of horses—the keep of which was at that time very costly, in consequence of the high price of corn—was still a great desideratum, and the best practical minds in the collieries were actively engaged in trying 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 plate-way along which it worked. [p.162]  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 tram-way leading from the collieries of Kenton and Coxlodge, on the 2d September, 1813.  This locomotive drew sixteen chaldron wagons, 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 among the crowd of spectators that day; and after examining the engine and observing its performances, he remarked 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 Coxlodge engine, he contemplated the construction of a new locomotive, which was to surpass all that had preceded it.  He observed that those engines which had been constructed up to this time, however ingenious in their arrangements, were in a great measure practical failures.  Mr. Blackett's was as yet both clumsy and expensive.  Chapman's had been removed from the Heaton tram-way in 1812, and was regarded as a total failure.  And the Blenkinsop engine at Coxlodge 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 shortly blown up, there was an end of that engine, and the colliery owners did not feel encouraged to try any farther experiment.

    An efficient and economical working locomotive engine, therefore, still remained to be invented, and to accomplish this object 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 entitle him to the merit of inventing the working locomotive, 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 principal partner, had already formed a very favourable opinion of the new colliery 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 authorized 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, when speaking of his early career at a public meeting in Newcastle, "was at Killingworth Colliery, and with Lord Ravensworth's money. [p.164]  Yes, Lord Ravensworth and partners were the first to intrust 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 being John Thirlwall, the colliery blacksmith, an excellent mechanic in his way, though quite new to the work now intrusted to him.
 

    In this first locomotive constructed at Killingworth, Stephenson to some extent followed the plan of Blenkinsop's engine.  The wrought-iron boiler was cylindrical, eight feet in length and thirty-four inches in diameter, with an internal flue-tube twenty inches wide passing through it.  The engine had two vertical cylinders of eight inches diameter and two feet stroke let into the boiler, which worked the propelling gear with cross-heads and connecting-rods.  The power of the two cylinders was combined by means of spur-wheels, which communicated the motive power to the wheels supporting the engine on the rail, instead of, as in Blenkinsop's engine, to cog-wheels 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 neutralize 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 total absence of springs.

    The wheels of the locomotive were all smooth, 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 wagon moderately loaded, and throw their entire weight upon the spokes on one side, when he found that the wagon could thus be easily propelled forward without the wheels slipping.  This, together with other experiments, satisfied him, as it had already satisfied Mr. Hedley, of the expediency of adopting smooth wheels on his engine, and it was so made 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 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.

    Although a considerable advance upon previous locomotives, "Blucher" (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 cog-wheels 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 dint of cost.

    We give the remainder of the history of George Stephenson's efforts to produce an economical working locomotive in the words of his son Robert, as communicated to the author in 1856, for the purposes of his father's "life."

    "A few months of experience and careful observation upon the operation of this (his first) engine convinced my father that the complication arising out of the action of the two cylinders being combined by spur-wheels would prevent their coming into practical application.  He then directed his attention to an entire change in the construction and mechanical arrangements, and in the following year took out a patent, dated February 28th, 1816, 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 great simplicity in the mode by which power was communicated to the wheels supporting the engine.

    "This second engine consisted as before of two vertical cylinders, which communicated directly with each pair of the four wheels that supported the engine by 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 engine, which was a rigid mass, with the wheels rolling upon the irregular surface of the rails; for it was evident that the two rails of the line of railway could not always be maintained at the same level with respect to each other—that one wheel at the end of the axle might be depressed into a part of the line which had subsided, while the other would be elevated.  In such a position of the axle and wheels it was clear 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 always to preserve complete parallelism with the axle of the wheels with which it was in communication.

    "In order to obtain the flexibility combined with direct action which was essential for insuring power and avoiding needless friction and jars from irregularities in the rail, my father employed 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 end 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, it being permitted to take place without producing jar or friction upon any part of the machine.

    "The next important point was to combine each pair of wheels by some simple mechanism, instead of the cog-wheels which had formerly been used. My father began by inserting each axle into two cranks at right angles to each other, with rods communicating horizontally between them.  An engine was made on this plan, and answered extremely well.  But at that period (1815) the mechanical skill of the country was not equal to the task of forging cranked axles of the soundness and strength necessary to stand the jars incident to locomotive work; so my father was compelled to fall back upon a substitute which, though less simple and less efficient, was within the mechanical capabilities of the workmen of that day, either for construction or repair.  He adopted a chain which rolled over indented wheels placed on the centre of each axle, and so arranged that the two pairs of wheels were effectually coupled and made to keep pace with each other.  But these chains 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 forward again.  Nevertheless, these engines continued in profitable use upon the Killingworth Colliery Railway for some years.  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; and this expedient completely answered the purpose required, without involving any expensive or difficult workmanship.

    "Another important improvement was introduced in this engine. The eduction steam had hitherto been allowed to escape direct into the open atmosphere; but my father, having observed the great velocity with which the waste-steam escaped, compared with the velocity with which the smoke issued from the chimney of the same engine, thought that by conveying the eduction steam into the chimney, and there allowing it to escape in a vertical direction, its velocity would be imparted to the smoke from the engine, or to the ascending current of air in the chimney.  The experiment was no sooner made than the power of the engine became more than doubled; combustion was stimulated, as it were, by a blast; consequently, the power of the boiler for generating steam was increased, and, in the same proportion, the useful duty of the engine was augmented.

    "Thus, in 1815, my father had succeeded in manufacturing an engine which included the following important improvements on all previous attempts in the same direction: simple and direct communication between the cylinder 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 fuel by employing the waste steam which had formerly been allowed uselessly to escape.  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 be regarded, in fact, as a type of the present locomotive engine.

Stephenson's locomotive for Killingworth Colliery.

    "In describing my father's application of the waste steam for the purpose of increasing the intensity of combustion in the boiler, and thus increasing the power of the engine without adding to its weight, and while claiming for this engine the merit of being a type of all those which have been successfully devised since the commencement of the Liverpool and Manchester Railway, it is necessary to observe that the next great improvement in the same direction, the 'multitubular boiler,' which took place some years later, could never have been used without the help of that simple expedient, the steamblast, by which power only the burning of coke was rendered possible.

    "I can not pass over this last-named invention of my father's without remarking how slightly, as an original idea, it has been appreciated; and yet how small would be the comparative value of the locomotive engine of the present day without the application of that important invention!

    "Engines constructed by my father in the year 1818 upon the principles just described are in use on the Killingworth Colliery Railway to this very day (1866), conveying, at the speed of perhaps five or six miles an hour, heavy coal-trains, probably as economically as any of the more perfect engines now in use.

    "There was another remarkable piece of ingenuity in this machine, which was completed so many years before the possibility of steam-locomotion became an object of general commercial interest and Parliamentary inquiry.  I have before observed that up to and after the year 1818 there was no such class of skilled mechanics, nor were there such machinery and tools for working in metals, as are now at the disposal of inventors and manufacturers.  Among other difficulties of a similar character, it was not possible at that time to construct springs of sufficient strength to support the improved engines.  The rails then used being extremely light, the roads became worn down by the traffic, and occasionally the whole weight of the engine, instead of being uniformly distributed over four wheels, was thrown almost diagonally upon two.  In order to avoid the danger arising from such irregularities in the road, my father arranged the boiler so 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 passed downward 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 that pressure being nearly equal to the support of one fourth of the weight of the engine, each axle, whatever might be its position, had the same amount of weight to bear, and consequently the entire weight was at all times nearly equally distributed among the wheels.  This expedient was more necessary in this case, as the weight of the new locomotive engines far exceeded that of the carriages which had hitherto been used upon colliery railways, and therefore subjected the rails to much greater risk from breakage.  And this mode of supporting the engine remained in use until the progress of spring-making had considerably advanced, when steel springs of sufficient strength superseded this highly ingenious mode of distributing the weight of the engine uniformly among the wheels."

    The invention of the Steam-blast by George Stephenson in 1815 was fraught with the most important consequences to railway locomotion, and it is not saying too much to aver that the success of the locomotive has been in a great measure 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 multitubular boiler (afterward invented) could never have been fully tested; and locomotives might still have been dragging themselves unwieldily along at little more than five or six miles an hour.

    As this invention has been the subject of considerable controversy, it becomes necessary to add a few words respecting it in this place.  It has been claimed as the invention of Trevithick in 1804, of Hedley in 1814, of Goldsworthy Gurney in 1820, and of Timothy Hackworth in 1829.  With respect to Trevithick, it appears that he discharged the waste steam into the chimney of his engine, but without any intention of thereby producing a blast; [p.171] and that he attached no value to the expedient is sufficiently obvious from the fact that in 1815 he took out a patent for urging the fire by means of fanners, similar to a winnowing machine.  The claim put forward on behalf of William Hedley, that he invented the blast-pipe for the Wylam engine, is sufficiently contradicted by the fact that the Wylam engine had no blast-pipe.  "I remember the Wylam engine," Robert Stephenson wrote to the author in 1857, "and I am positive there was no blast-pipe."  On the contrary, the Wylam engine embodied a contrivance for the express purpose of preventing a blast.  This is clearly shown by the drawing and description of it contained in the first edition of Nicholas Wood's "Practical Treatise on Railroads," published in 1825.  This evidence is all the more valuable for our purpose as it was published long before any controversy had arisen as to the authorship of the invention, and, indeed, before it was believed that any merit whatever belonged to it.  And it is the more remarkable, as Nicholas Wood himself, who published the first practical work on railways, did not at that time approve of the steam-blast, and referred to the Wylam engine in illustration of how it might be prevented.

    The following passage from Mr. Wood's book clearly describes the express object and purpose for which George Stephenson invented and applied the steam-blast in the Killingworth engines.  Describing their action, Mr. Wood says:

    "The steam is admitted to the top and bottom of the piston by means of a sliding valve, which, being moved up and down alternately, opens a communication between the top and bottom of the cylinder and the pipe that is open into the chimney and turns up within it.  The steam, after performing its office within the cylinder, is thus thrown into the chimney, and the power with which it issues will be proportionate to the degree of elasticity; and the exit being directed upwards accelerates the velocity of the current of heated air accordingly." [p.172-1]

    And again, at another part of the book, he says:

    "There is another great objection urged against locomotives, which is, the noise that the steam makes in escaping into the chimney; this objection is very singular, as it is not the result of any inherent form in the organization of such engines, but an accidental circumstance.  When the engines were first made, the steam escaped into the atmosphere, and made comparatively little noise; it was found difficult then 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 draught of the chimney. Mr. Stephenson thought that by causing the steam, to escape into the chimney through a pipe with its end turned upward, the velocity of the current would be accelerated, and such was the effect; but, in remedying one evil, another has been produced, which, though objectionable in some places, was not considered as objectionable on a private railroad.  The tube through the boiler having been increased, there is now no longer any occasion for the action of the steam to assist the motion of the heated air in the chimney.  The steam thrown in this manner into the chimney acts as a trumpet, and certainly makes a very disagreeable noise.  Nothing, however, is more easy to remedy, and the very act of remedying this defect will also be the means of economizing the fuel." [p.172-2]

    Mr. Wood then proceeds to show how the noise caused by the blast—how, in fact, the blast itself, might be effectually prevented by adopting the expedient employed in the Wylam engine; which was, to send the exhaust steam, not into the chimney (where alone the blast could act with effect by stimulating the draught), but into a steam-reservoir provided for the purpose. His words are these:

    "Nothing more is wanted to destroy the noise than to cause the steam to expand itself into a reservoir, and then allow it to escape gradually to the atmosphere through the chimney.  Upon the Wylam railroad the noise was made the subject of complaint by a neighbouring gentleman, and they adopted this mode, which had the effect above mentioned." [p.173]

    It is curious to find that Mr. Nicholas Wood continued to object to the use of the steam-blast down even to the time when the Liverpool and Manchester Railway Bill was before Parliament.  In his evidence before the Committee on that Bill in 1825, he said: "Those engines [at Killingworth] puff very much and the object is to get an increased draught in the chimney.  Now (by enlarging the flue-tube and giving it a double turn through the boiler) we have got a sufficiency of steam without it, and I have no doubt, by allowing the steam to exhaust itself in a reservoir, it would pass quietly into the chimney without that noise."  In fact, Mr. Wood was still in favour of the arrangement adopted in the Wylam engine, by which the steam-blast had been got rid of altogether.

    If these statements, made in Mr. Wood's book, be correct—and they have never been disputed—they render it perfectly clear that George Stephenson invented and applied the steam-blast for the express purpose of quickening combustion in the furnace by increasing the draught in the chimney.  Although urged by Wood to abandon the blast, Stephenson continued to hold by it as one of the vital powers of the locomotive engine.  It is quite true that in the early engines, with only a double flue passing through the boiler, run as they were at low speeds, the blast was of comparatively less importance.  It was only when the improved passenger engine, fitted with the multitubular boiler, was required to be run at high speeds that the full merits of the blast were brought out; and in detecting its essential uses in this respect, and sharpening it for the purpose of increasing its action, the sagacity of Timothy Hackworth, of Darlington, is entitled to due recognition.

 


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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 work-people.  Killingworth Colliery was not free from such deplorable calamities; and during the time that Stephenson was employed as 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 ten persons were killed.  Stephenson was near the pit mouth at the time, and the circumstances connected with the explosion made a deep impression on his mind, as appears from the graphic account which he gave of it to the Committee of the House of Commons on accidents in mines, some thirty years after the event.

    "The pit," said he,

"had just ceased drawing coals, and nearly all the men had got out.  It was some time in the afternoon, a little after midday.  There were five men that went down the pit; four of them for the purpose of preparing a place for the furnace.  The fifth was a person who went down to set them to work.  I sent this man down myself, and he had just got to the bottom of the shaft about two or three minutes when the explosion took place.  I had left the mouth of the pit, and had gone about fifty or sixty yards away, when I heard a tremendous noise, looked round, and saw the discharge come out of the pit like the discharge of a cannon.  It continued to blow, I think, for a quarter of an hour, discharging every thing that had come into the current.  Wood came up, stones came up, and trusses of hay that went up into the air like balloons.  Those trusses had been sent down during the day, and I think they had in some measure injured the ventilation of the mine.  The ground all round the top of the pit was in a trembling state.  I went as near as I durst go; every thing appeared cracking and rending about me.  Part of the brattice, which was very strong, was blown away at the bottom of the pits.  Very large pumps were lifted from their places, so that the engine could not work.  The pit was divided into four by partitions; it was a large pit, fourteen feet in diameter, and partitions were put down at right angles, which made four compartments.  The explosion took place in one of those four quarters, but it broke through into all the others at the bottom, and the brattice or partitions were set on fire at the first explosion.

    "Nobody durst go near the shafts for some time, for fear of another explosion taking place.  At last we considered it necessary to run the rope backward and forward, and give the miners, if there were any at the bottom of the shaft, an opportunity of catching the rope as it came to the bottom.  Several men were safely got up in this way; one man, who had got hold of the rope, was being drawn up, when a farther explosion took place while he was still in the shaft, and the increased current which came about him projected him as it were up the shaft; yet he was landed without injury: it was a singular case. . . . The pit continued to blast every two or three hours for about two days.  It appears that the coal had taken fire, and as soon as the carburetted hydrogen gas, collected in sufficient quantity to reach the part where it was burning, it ignited again; but none of the explosions were equal to the first, on account of many parts of the mine having become filled with azotic gas, or the after-damp of the mine.  All the ditches in the country-side were stopped to get water to pour into the pit.  We had fire-engines brought from Newcastle, and the water was poured in till it came above the fire, and then it was extinguished.  The loss to the owners of the colliery by this accident must have been about £20,000." [p.176]

    Another explosion took place in the same pit in 1809, by which twelve 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 the of the worst being that of 1812, in the Felling Pit near Gateshead, a mine belonging to Mr. Brandling, by which no fewer than ninety men and boys were suffocated or burnt to death; and a similar accident occurred in the same pit in the year following, by which twenty-two men and boys perished.

    It was natural that 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 inclined planes, along which the coals were sent to the pit entrance, he was necessarily very often under ground, 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; and 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 tried, while 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 the year 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 engine-man to lower him down the shaft in the corve.  There was danger, it might be death, before him, but he must go.

    He was soon at the bottom, and in the midst of the men, who were paralyzed at the danger which threatened the lives of all in the pit.  Leaping from the corve on its touching the ground, he called out, "Are there six men among you who have the courage to follow me?  If so, come, and we will put the fire out."  The Killingworth pitmen had the most perfect confidence in their engine-wright, and they readily volunteered to follow him.  Silence succeeded the frantic tumult of the previous minute, and the men set to work with a will.  In every mine, bricks, mortar, and tools enough are at hand, and by Stephenson's direction the materials were forthwith carried to the required spot, where, in a very short time, a wall was raised at the entrance to the main, he himself taking the most active part in the work.  The atmospheric air was by this means excluded, the fire was extinguished, most of the people in the pit were saved from death, and the mine was preserved.

    This anecdote of George Stephenson was related to the writer, near the pit-mouth, by one of the men.  Kit Heppel, who had been present, and helped to build up the brick wall by which the fire was stayed, though several of the workmen were suffocated.  Heppel relates that, when down the pit some days after, seeking out the dead bodies, the cause of the accident was the subject of some conversation between himself and Stephenson, and Heppel then asked him, "Can nothing be done to prevent such awful occurrences?"  Stephenson replied that he thought something might be done.  "Then," said Heppel, "the sooner you begin the better, for the price of coal-mining now is pitmen's lives."

    Fifty years since, many of the best pits were so full of the inflammable gas given forth by the coal that they could not be worked without the greatest danger, and for this reason some were altogether abandoned.  The rudest possible means were adopted of producing light sufficient to enable the pitmen to work by.  The phosphorescence of decayed fish-skins was tried; but this, though safe, was very inefficient.  The most common method employed was what was called a steel mill, the notched wheel of which, being made to revolve against a flint, struck a succession of sparks, which scarcely served to do more than make the darkness visible.  A boy carried the apparatus, working the wheel; and by the imperfect light thus given forth the miner plied his dangerous trade.  Candles were only used in those parts of the pit where gas was not abundant.  Under this rude system not more than one third of the coal could be worked, while two thirds were left.

    What the workmen, not less than the coal-owners, eagerly desired was a lamp that should give forth sufficient light, without communicating flame to the inflammable gas which accumulated in certain parts of the pit.  Something had already been done toward the invention of such a lamp by Dr. Clanny, of Sunderland, who, in 1818, contrived an apparatus to which he gave air from the mine through water, by means of bellows.  This lamp went out of itself in inflammable gas.  It was found, however, too unwieldy to be used by the miners for the purposes of their work, and did not come into general use.  A committee of gentlemen interested in coal-mining was formed to investigate the causes of the explosions, and to devise, if possible, some means of preventing them.  At the invitation of that committee, Sir Humphry Davy, then in the full zenith of his reputation, was requested to turn his attention to the subject.  He accordingly visited the collieries near Newcastle on the 24th of August, 1815, and at the close of that year, on the 9th of November, 1815, he read before the Royal Society of London his celebrated paper "On the Fire-damp of Coal Mines, and on Methods of Lighting the Mine so as to prevent its Explosion."

    But a humbler though not less diligent and original thinker had been at work before him, and had already practically solved the problem of the Safety-lamp.  Stephenson was, of course, well aware of the desire which prevailed in the colliery districts for the invention of a lamp which should give light enough for the miners to work by without exploding the fire-damp, and the painful incidents above described only served to quicken his eagerness to master the difficulty.

    For several years he had been engaged, in his own rude way, in making experiments with the fire-damp in the Killingworth mine.  The pitmen used to expostulate with him on these occasions, believing the experiments to be fraught with danger.  One of the sinkers, called M'Crie, observing him holding up lighted candles to the windward of the "blower" or fissure from which the inflammable gas escaped, entreated him to desist; but Stephenson's answer was, that "he was busy with a plan by which he hoped to make his experiments useful for preserving men's lives."  On these occasions the miners usually got out of the way before he lit the gas.

    In 1815, although he was very much occupied with the business of the collieries and the improvement of his locomotive engine, he was also busily engaged in making experiments upon the inflammable gas in the Killingworth Pit.  As he himself afterward related to the Committee of the House of Commons which sat on the subject of Accidents in Mines in 1835, he imagined that if he could construct a lamp with a chimney so arranged as to cause a strong current, it would not fire at the top of the chimney, as the burnt air would ascend with such a velocity as to prevent the inflammable air of the pit from descending toward the flame; and such a lamp, he thought, might be taken into a dangerous atmosphere without risk of exploding.

    Such was Stephenson's theory, when he proceeded to embody his idea of a miner's safety-lamp in a practical form.  In the month of August, 1815, he requested his friend Nicholas Wood, the head viewer, to prepare a drawing of a lamp according to the description which he gave him.  After several evenings' careful deliberations, the drawing was prepared, and it was shown to several of the head men about the works.  "My first lamp," said Stephenson, describing it to the committee above referred to, "had a chimney at the top of the lamp, and a tube at the bottom to admit the atmospheric air, or fire-damp and air, to feed the burner or combustion of the lamp.  I was not aware of the precise quantity required to feed the combustion; but to know what quantity was necessary, I had a slide at the bottom of the tube in my first lamp, to admit such a quantity of air as might eventually be found necessary to keep up the combustion."

    Accompanied by his friend Wood, Stephenson went into Newcastle, and ordered a lamp to be made according to his plan by the Messrs. Hogg, tinmen, at the head of the Side—a well-known street in Newcastle.  At the same time, he ordered a glass to be made for the lamp at the Northumberland Glass-house in the same town.  This lamp was received from the makers on the 21st of October, and was taken to Killingworth for the purpose of immediate experiment.

    "I remember that evening as distinctly as if it had been but yesterday," said Robert Stephenson, describing the circumstances to the author in 1857.  "Moodie came to our cottage about dusk, and asked 'if father had got back with the lamp.'  'No.'  'Then I'll wait till he comes,' said Moodie; 'he can't be long now.'  In about half an hour, in came my father, his face all radiant.  He had the lamp with him!  It was at once uncovered and shown to Moodie.  Then it was filled with oil, trimmed, and lighted.  All was ready, only the head viewer hadn't arrived.  'Run over to Benton for Nichol, Robert,' said my father to me, 'and ask him to come directly; say we're going down the pit to try the lamp.'  By this time it was quite dark, and off I ran to bring Nicholas Wood.  His house was at Benton, about a mile off.  There was a short cut through Benton Church-yard, but just as I was about to pass the wicket I saw what I thought was a white figure moving about among the grave-stones.  I took it for a ghost!  My heart fluttered, and I was in a great fright, but to Nichol's house I must get, so I made the circuit of the churchyard; and when I got round to the other side I looked, and, lo! the figure was still there.  But what do you think it was?  Only the grave-digger, plying his work at that late hour by the light of his lantern set upon one of the grave-stones!  I found Wood at home, and in a few minutes he was mounted and off to my father's.  When I got home I was told they had just left—it was then about eleven—and gone down the shaft to try the lamp in one of the most dangerous parts of the mine."

    Arrived at the bottom of the shaft with the lamp, the party directed their steps toward one of the foulest galleries in the pit, where the explosive gas was issuing through a blower in the roof of the mine with a loud hissing noise.  By erecting some deal boarding round that part of the gallery into which the gas was escaping, the air was thus made more foul for the purpose of the experiment.  After waiting about an hour, Moodie, whose practical experience of fire-damp in pits was greatest than that of either Stephenson or Wood, was requested to go into the place which had thus been made foul; and, having done so, he returned, and told them that the smell of the air was such that if a lighted candle were now introduced an explosion must inevitably take place.  He cautioned Stephenson as to the danger both to themselves and to the pit if the gas took fire; but Stephenson declared his confidence in the safety of his lamp, and, having lit the wick, he boldly proceeded with it toward the explosive air.  The others, more timid and doubtful, hung back when they came within hearing of the blower; and, apprehensive of the danger, they retired into a safe place, out of sight of the lamp, which gradually disappeared with its bearer in the recesses of the mine.  It was a critical moment, and the danger was such as would have tried the stoutest heart.  Stephenson, advancing alone, with his yet untried lamp, in the depths of those underground workings, calmly venturing his life in the determination to discover a mode by which the lives of many might be saved, and death disarmed in these fatal caverns, presented an example of intrepid nerve and manly courage more noble even than that which, in the excitement of battle and the collective impetuosity of a charge, carries a man up to the cannon's mouth.

    Advancing to the place of danger, and entering within the fouled air, his lighted lamp in hand, Stephenson held it firmly out, in the full current of the blower, and within a few inches of its mouth.  Thus exposed, the flame of the lamp at first increased, then flickered, and then went out; but there was no explosion of the gas.  Returning to his companions, who were still at a distance, he told them what had occurred.  Having now acquired somewhat more confidence, they advanced with him to a point from which they could observe the experiment repeated, but still at a safe distance.  They saw that when the lighted lamp was held within the explosive mixture, there was a great flame; the lamp was almost full of fire; and then it seemed to be smothered out.  Again returning to his companions, he re-lighted the lamp, and repeated the experiment.  This was done several times, with the same result.  At length Wood and Moodie ventured to advance close to the fouled part of the pit; and, in making some of the later trials, Mr. Wood himself held up the lighted lamp to the blower. [p.183]  Such was the result of the first experiments with the first practical Miner's Safety-lamp, and such was the daring resolution of its inventor in testing its qualities.

    Before leaving the pit, Stephenson expressed his opinion that, by an alteration of the lamp which he contemplated, he could make it burn better.  This was by a change in the slide through which the air was admitted into the lower part of the lamp, under the flame.  After making some experiments on the air collected at the blower, by means of bladders which were mounted with tubes of various diameters, he satisfied himself that, when the tube was reduced to a certain diameter, the explosion would not pass through; and he fashioned his slide accordingly, reducing the diameter of the tube until he conceived it was quite safe.  In about a fortnight the experiments were repeated in the pit, in a place purposely made foul as before.  On this occasion a larger number of persons ventured to witness the experiments, which again proved successful.  The lamp was not yet, however, so efficient as the inventor desired.  It required, he observed, to be kept very steady when burning in the inflammable gas, otherwise it was liable to go out, in consequence, as he imagined, of the contact of the burnt air (as he then called it), or azotic gas, which lodged round the exterior of the flame.  If the lamp was moved backward and forward, the azote came in contact with the flame and extinguished it.  "It struck me," said he, "that if I put more tubes in, I should discharge the poisonous matter that hung round the flame by admitting the air to its exterior part."

    Although he had then no access to scientific works, nor intercourse with scientific men, nor any thing that could assist him in his inquiries on the subject besides his own indefatigable spirit of inquiry, Stephenson contrived a rude apparatus, by means of which he proceeded to test the explosive properties of the gas and the velocity of current (for this was the direction of his inquiries) required to permit the explosion to pass through tubes of different diameters.  In making these experiments in his cottage at the West Moor, Nicholas Wood and George's son Robert usually acted as his assistants, and sometimes the gentlemen of the neighbourhood—among others, William Brandling and Matthew Bell, who were interested in coal-mining—attended as spectators.  One who was present on such an occasion remembers that, when an experiment was about to be performed, and all was ready, George called to Mr. Wood, who worked the stop-cocks of the gasometer, "Wise on [turn on] the hydrogen, Nichol!"

    These experiments were not performed without risk, for on one occasion the experimenting party had nearly blown off the roof of the cottage.  One of these "blows up" was described by Stephenson himself before the Committee on Accidents in Coal Mines in 1835:

    "I made several experiments," said he, "as to the velocity required in tubes of different diameters, to prevent explosion from fire-damp.  We made the mixture in all proportions of light carburetted hydrogen with atmospheric air in the receiver, and we found by the experiments that when a current of the most explosive mixture that we could make was forced up a tube four tenths of an inch in diameter, the necessary current was nine inches in a second to prevent its coming down that tube.  These experiments were repeated several times.  We had two or three blows up in making the experiments, by the flame getting down into the receiver, though we had a piece of very fine wire-gauze put at the bottom of the pipe, between the receiver and the pipe through which we were forcing the current.  In one of these experiments I was watching the flame in the tube, my son was taking the vibrations of the pendulum of the clock, and Mr. Wood was attending to give me the column of water as I called for it, to keep the current up to a certain point.  As I saw the flame descending in the tube I called for more water, and Wood unfortunately turned the cock the wrong way; the current ceased, the flame went down the tube, and all our implements were blown to pieces, which at the time we were not very well able to replace."

    The explosion of this glass receiver, which had been borrowed from the stores of the Philosophical Society at Newcastle for the purpose of making the experiments, caused the greatest possible dismay among the party, and they dreaded to inform Mr. Turner, the secretary, of the calamity which had occurred. [p.185]  Fortunately, none of the experimenters were injured by the accident.

    Stephenson followed up these experiments by others of a similar kind, with the view of ascertaining whether ordinary flame would pass through tubes of a small diameter, and with this object he filed off the barrels of several small keys.  Placing these together, he held them perpendicularly over a strong flame, and ascertained that it did not pass upward.  This was a farther proof to him of the soundness of the principle on which he had been proceeding.

    In order to correct the defect of his first lamp, he accordingly proceeded to alter it so as to admit the air to the flame by several tubes of reduced diameter instead of by a single tube.  He inferred that a sufficient quantity of air would thus be introduced into the lamp for the purposes of combustion, while the smallness of the apertures would still prevent the explosion passing downward, at the same time that the "burnt air" (the cause, in his opinion, of the lamp going out) would be more effectually dislodged.  The requisite alterations were made in the lamp by Mr. Matthews, a tinman in Newcastle, and it was so altered that the air was admitted by three small tubes inserted in the bottom, the openings of which were placed on the outside of the burner, instead of having (as in the original lamp) the one tube opening directly under the flame.

    This second or altered lamp was tried in the Killingworth Pit on the 4th of November, and was found to burn better than the first lamp, and to be perfectly safe.  But, as it did not yet come up entirely to the inventor's expectations, he proceeded to contrive a third lamp, in which he proposed to surround the oil vessel with a number of capillary tubes.  Then it struck him that if he cut off the middle of the tubes, or made holes in metal plates, placed at a distance from each other equal to the length of the tubes, the air would get in better, and the effect in preventing the communication of explosion would be the same.

    He was encouraged to persevere in the completion of his safety-lamp by the occurrence of several fatal accidents about this time in the Killingworth Pit.  On the 9th of November a boy was killed by a blast in the A pit, at the very place where Stephenson had made the experiments with his first lamp; and, when told of the accident, he observed that if the boy had been provided with his lamp, his life would have been saved.  On the 20th of November he went over to Newcastle to order his third lamp from Mr. Watson, a plumber in that town.  Mr. Watson referred him to his clerk, Henry Smith, whom Stephenson invited to join him at a neighbouring public house, where they might quietly talk over the matter, and finally settle the plan of the new lamp.  They adjourned to the "Newcastle Arms," near the present High-Level Bridge, where they had some ale, and a design of the lamp was drawn in pencil upon a half-sheet of foolscap, with a rough specification subjoined.  The sketch, when shown to us by Robert Stephenson some years since, still bore the marks of the ale.  It was a very rude design, but sufficient to work from.  It was immediately placed in the hands of the workmen, finished in the course of a few days, and experimentally tested in the Killingworth Pit like the previous lamps on the 30th of November, by which date neither Stephenson nor Wood had heard of Sir Humphry Davy's experiments, nor of the lamp which that gentleman proposed to construct.

    An angry controversy afterward took place as to the respective merits of George Stephenson and Sir Humphry Davy in respect of the invention of the Safety-lamp.  A committee was formed on both sides, and the facts were stated in various ways.  It is perfectly clear, however, that Stephenson had ascertained the fact that flame will not pass through tubes of a certain diameter—the principle on which the safety-lamp is constructed—before Sir Humphry Davy had formed any definite idea on the subject, or invented the model lamp afterward exhibited by him before the Royal Society.  Stephenson had actually constructed a lamp on such a principle, and proved its safety, before Sir Humphry had communicated his views on the subject to any person; and by the time that the first public intimation had been given of his discovery, Stephenson's second lamp had been constructed and tested in like manner in the Killingworth Pit.  The first was tried on the 21st of October, 1815; the second was tried on the 4th of November; but it was not until the 9th of November that Sir Humphry Davy presented his first lamp to the public.  And by the 30th of the same month, as we have seen, Stephenson had constructed and tested his third safety-lamp.
 

    Stephenson's theory of the "burnt air'' and the "draught" was no doubt wrong, but his lamp was right, and that was the great fact which mainly concerned him.  Torricelli did not know the rationale of his tube, nor Otto von Guericke that of his air-pump; yet no one thinks of denying them the merit of their inventions on that account.  The discoveries of Volta and Galvani were in like manner independent of theory; the greatest discoveries consisting in bringing to light certain grand facts, on which theories are afterward framed.  Our inventor had been pursuing the Baconian method, though he did not think of that; his sole object being to invent a safe lamp, which he knew could only be done through the process of repeated experiment.  Hence his numerous experiments on the fire-damp at the blowers in the mine, as well as on carburetted hydrogen gas in his cottage by means of the apparatus above described.  By experiment he distinctly ascertained that the explosion of fire-damp could not pass through small tubes; and he also did what had not before been done by any inventor—he constructed a lamp on this principle, and repeatedly proved its safety at the risk of his life.  At the same time, there is no doubt that it was to Sir Humphry Davy that the merit belonged of elucidating the true law on which the safety-lamp is constructed.

    The subject of this important invention excited so much interest in the northern mining districts, and Stephenson's numerous friends considered his lamp so completely successful—having stood the test of repeated experiments—that they urged him to bring his invention before the Philosophical and Literary Society of Newcastle, of whose apparatus he had availed himself in the course of his experiments on fire-damp.  After much persuasion he consented to do so, and a meeting was appointed for the purpose of receiving his explanations on the evening of the 5th of December, 1815.  Stephenson was at that time so diffident in manner and unpractised in speech, that he took with him his friend Nicholas Wood to act as his interpreter and expositor on the occasion.  From eighty to a hundred of the most intelligent members of the society were present at the meeting when Mr Wood stood forward to expound the principles on which the lamp had been formed, and to describe the details of its construction.  Several questions were put, to which Mr Wood proceeded to give replies to the best of his knowledge.  But Stephenson who up to that time had stood behind Wood, screened from notice, observing that the explanations given were not quite correct, could no longer control himself, and, standing forward, he proceeded in his strong Northumbrian dialect to describe the lamp down to its minutest details.  He then produced several bladders full of carburetted hydrogen, which he had collected from the blowers in the Killingworth mine, and proved the safety of his lamp by numerous experiments with the gas, repeated in various ways, his earnest and impressive manner exciting in the minds of his auditors the liveliest interest both in the inventor and his invention.

    Shortly after, Sir H. Davy's model lamp was received and exhibited to the coal-miners at Newcastle, on which occasion the observation was made by several gentlemen, "Why, it is the same as Stephenson's!"

    Notwithstanding Stephenson's claim to be regarded as the first inventor of the Tube Safety-lamp, his merits do not seem to have been generally recognized.  Sir Humphry Davy carried off the larger share of the éclat which attached to the discovery.  What chance had the unknown workman of Killingworth with so distinguished a competitor?  The one was as yet but a colliery engine-wright, scarce raised above the manual-labour class, without chemical knowledge or literary culture, pursuing his experiments in obscurity, with a view only to usefulness; the other was the scientific prodigy of his day, the pet of the Royal Society, the favourite of princes, the most brilliant of lecturers, and the most popular of philosophers.

    No small indignation was expressed by the friends of Sir Humphry Davy at Stephenson's "presumption" in laying claim to the invention of the Safety-lamp.  The scientific class united to ignore him entirely in the matter.  In 1831, Dr. Paris, in his "Life of Sir Humphry Davy," thus wrote: "It will hereafter be scarcely believed that an invention so eminently scientific, and which could never have been derived but from the sterling treasury of science, should have been claimed on behalf of an engine-wright of Killingworth, of the name of Stephenson—a person not even possessing a knowledge of the elements of chemistry."

    But Stephenson was really far above claiming for himself an invention not his own.  He had already accomplished a far greater thing even than the making of a safety-lamp: he had constructed a successful locomotive, which was to be seen in daily work on the Killingworth Railway.  By the improvements he had made in the engine, he might almost be said to have invented it; yet no one—not even the philosophers—detected as yet the significance of that wonderful machine.  It excited no scientific interest, called forth no leading articles in the newspapers or the reviews, and formed the subject of no eloquent lectures at the Royal Society; for railways were as yet comparatively unknown, and the might which slumbered in the locomotive was scarcely, as yet, even dreamed of.  What railways were to become rested in a great measure with that "engine-wright of Killingworth, of the name of Stephenson," though he was scarcely known as yet beyond the bounds of his own district.

    As to the value of the invention of the safety-lamp there could be no doubt and the colliery owners of Durham and Northumberland, to testify their sense of its importance, determined to present a testimonial to its inventor.  The friends of Sir H. Davy met in August, 1816, to take steps to raise a subscription for the purpose.  The advertised object of the meeting was to present him with a reward for the invention of his safety-lamp.  To this no objection could be taken; for, though the principle on which the safety-lamps of Stephenson and Davy were constructed was the same, and although Stephenson's lamp was unquestionably the first successful lamp that had been constructed on such principle, and proved to be efficient, yet Sir H. Davy did invent a safety-lamp, no doubt quite independently of all that Stephenson had done; and having directed his careful attention to the subject, and elucidated the true theory of explosion of carburetted hydrogen, he was entitled to all praise and reward for his labour.  But when the meeting of coal-owners proposed to raise a subscription for the purpose of presenting Sir H. Davy with a reward for "his invention of the safety-lamp," the case was entirely altered, and Stephenson's friends then proceeded to assert his claims to be regarded as its first inventor.

    Many meetings took place on the subject, and much discussion ensued, the result of which was that a sum of £2000 was presented to Sir Humphry Davy as "the inventor of the safety-lamp;" but, at the same time, a purse of 100 guineas was voted to George Stephenson, in consideration of what he had done in the same direction.  This result was, however, very unsatisfactory to Stephenson, as well as to his friends; and Mr. Brandling, of Gosforth, suggested to him that, the subject being now fairly before the public, he should publish a statement of the facts on which his claim was founded.

    But this was not at all in George Stephenson's line.  He had never appeared in print before, and it seemed to him a far more formidable thing to write a letter for publication in "the papers" than even to invent a safety-lamp or design a locomotive.  Having called his son Robert to his assistance, he set him down before a sheet of foolscap, and when all was ready, he said, "Now, put down there just what I tell you."  The composition of this letter, as we were informed by the writer of it, occupied more evenings than one; and when it was at length finished after many corrections, and fairly copied out, the father and son set out—the latter dressed in his Sunday's round jacket—to lay the joint production before Mr. Brandling, at Gosforth House.  Glancing over the letter, Mr. Brandling said, "George, this will never do."  "It is all true, sir," was the reply.  "That may be; but it is badly written."  Robert blushed, for he thought it was the penmanship that was called in question, and he had written his very best.  Mr. Brandling then requested his visitors to sit down while he put the letter in a more polished form, which he did, and it was shortly after published in the local papers.

    As the controversy continued for some time longer to be carried on in the Newcastle papers, Mr. Stephenson, in the year 1817, consented to publish the detailed plans, with descriptions, of the several safety-lamps which he had contrived for use in the Killingworth Colliery.  The whole forms a pamphlet of only sixteen pages of letter-press. [p.192]

    His friends, being fully satisfied of his claims to priority as the inventor of the safety-lamp used in the Killingworth and other collieries, proceeded to hold a public meeting for the purpose of presenting him with a reward "for the valuable service he had thus rendered to mankind."  Charles J. Brandling, Esq., occupied the chair; and several resolutions were passed, of which the first and most important was as follows: "That it is the opinion of this meeting that Mr. George Stephenson, having discovered the fact that explosion of hydrogen gas will not pass through tubes and apertures of small dimensions, and having been the first to apply that principle in the construction of a safety lamp, is entitled to a public reward."

    A subscription was immediately commenced with this object, and a committee was formed, consisting of the Earl of Strathmore, C. J. Brandling, and others.  The subscription list was headed by Lord Ravensworth, one of the partners in the Killingworth Colliery, who showed his appreciation of the merits of Stephenson by giving 100 guineas.  C. J. Brandling and partners gave a like sum, and Matthew Bell and partners, and John Brandling and partners, gave 50 guineas each.

    When the resolutions appeared in the newspapers, the scientific friends of Sir Humphry Davy in London met, and passed a series of counter-resolutions, which they published, declaring their opinion that Mr. Stephenson was not the author of the discovery of the fact that explosion of hydrogen will not pass through tubes and apertures of small dimensions, and that he was not the first to apply that principle to the construction of a safety-lamp.  To these counter resolutions were attached the well-known names of Sir Joseph Banks, P.R.S., William Thomas Brande, Charles Hatchett, W. H. Wollaston, and Thomas Young.

    Mr. Stephenson's friends then, to make assurance doubly sure, and with a view to set the question at rest, determined to take evidence in detail as to the date of discovery by George Stephenson of the fact in question, and its practical application by him in the formation and actual trial of his safety-lamp.  The witnesses examined were George Stephenson himself, Mr. Nicholas Wood, and John Moodie, who had been present at the first trial of the lamp; the several tinmen who made the lamps; the secretary and other members of the Literary and Philosophical Society of Newcastle, who were present at the exhibition of the third lamp; and some of the workmen who were present at the Killingworth Colliery, who had been witnesses of Stephenson's experiments on fire-damp made with the lamps at different times before Sir Humphry Davy's investigations had been heard of.  This evidence was quite conclusive to the minds of the gentlemen who investigated the subject, and they published it in 1817, together with their Report, in which they declared that, "after a careful inquiry into the merits of the case, conducted, as they trusty in a spirit of fairness and moderation, they can perceive no satisfactory reason for changing their opinion." [p.193]

    The Stephenson subscription, when collected, amounted to £1000.  Part of the money was devoted to the purchase of a silver tankard, which was presented to the inventor, together with the balance of the subscription, at a public dinner given in the Assembly Rooms at Newcastle. [p.194]  But what gave Stephenson even greater pleasure than the silver tankard and purse of sovereigns was the gift of a silver watch, purchased by small subscriptions collected among the colliers themselves, and presented to him by them as a token of their esteem and regard for him as a man, as well as of their gratitude for the perseverance and skill with which he had prosecuted his valuable and life-saving invention to a successful issue.  To the last day of his life he spoke with pride of this watch as the most highly-prized gift he had ever received.

    However great may be the merits of Stephenson in connection with the invention of the tube safety-lamp, they can not be regarded as detracting in any degree from the reputation of Sir Humphry Davy.  His inquiries into the explosive properties of carburetted hydrogen gas were quite original, and his discovery of the fact that explosion will not pass through tubes of a certain diameter was made independently of all that Stephenson had done in verification of the same fact.  It would even appear that Mr. Smithson Tennant and Dr. Wollaston had observed the same fact several years before, though neither Stephenson nor Davy knew of it while they were prosecuting their experiments.  Sir Humphry Davy's subsequent modification of the tube-lamp, by which, while diminishing the diameter, he in the same ratio shortened the tubes without danger, and in the form of wire gauze enveloped the safety-lamp by a multiplicity of tubes, was a beautiful application of the true theory which he had formed upon the subject.

    The increased number of accidents which have occurred from explosions in coal-mines since the general introduction of the Davy lamp led to considerable doubts being entertained as to its safety, and inquiries were consequently made as to the means by which it might be farther improved; for experience has shown that, under certain circumstances, the Davy lamp is not safe.  Stephenson was himself of opinion that the modification of his own and Sir Humphry Davy's lamp, by combining the glass cylinder with the wire-gauze, would give the best lamp.  At the same time, it must be admitted that the Davy and the Geordy lamps alike failed to stand the severe tests to which they were submitted by Dr. Pereira, before the Committee on Accidents in Mines.  Indeed, Dr. Pereira did not hesitate to say that, when exposed to a current of explosive gas, the Davy lamp is "decidedly unsafe," and that the experiments by which its safety had been "demonstrated" in the lecture-room had proved entirely "fallacious."

    It is worthy of remark that, under circumstances in which the wire-gauze of the Davy lamp becomes red-hot from the high explosiveness of the gas, the Geordy lamp is extinguished; and we can not but think that this fact testifies to the decidedly superior safety of the Geordy.  An accident occurred in the Oaks Colliery Pit at Barnsley on the 20th of August, 1857, which strikingly exemplified the respective qualities of the lamps.  A sudden outburst of gas took place from the floor of the mine along a distance of fifty yards.  Fortunately, the men working in the pit at the time were all supplied with safety-lamps—the hewers with Stephenson's, and the hurriers with Davy's.  On this occasion, the whole of the Stephenson lamps, over a space of five hundred yards, were extinguished almost instantaneously; whereas the Davy lamps were filled with fire and became red-hot, so that several of the men using them had their hands burnt by the gauze.  Had a strong current of air been blowing through the gallery at the time, an explosion would most probably have taken place—an accident which, it will be observed, could not, under such circumstances, occur from the use of the Geordy, which is immediately extinguished as soon as the air becomes explosive. [p.196]

    Nicholas Wood, a good judge, has said of the two inventions, "Priority has been claimed for each of them—I believe the inventions to be parallel.  By different roads they both arrived at the same result.  Stephenson's is the superior lamp.  Davy's is safe—Stephenson's is safer."

    When the question of priority was under discussion at Mr. Lough's studio in 1857, Sir Matthew White Ridley asked Robert Stephenson, who was present, for his opinion on the subject.  His answer was, "I am not exactly the person to give an unbiased opinion; but, as you ask me frankly, I will as frankly say, that if George Stephenson had never lived, Sir Humphry Davy could and most probably would have invented the safety-lamp; but again, if Sir Humphry Davy had never lived, George Stephenson certainly would have invented the safety-lamp, as I believe he did, independently of all that Sir Humphry Davy had done in the matter."

    To this day the Geordy lamp continues in regular use in the Killingworth Collieries, and the Killingworth pitmen have expressed to the writer their decided preference for it compared with the Davy.  It is certainly a strong testimony in its favour that no accident is known to have arisen from its use since it was generally introduced into the Killingworth pits.