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.

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.

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 entitle 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.

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 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 cogwheels became at all worn, a rattling noise was produced during the travelling of the engine.

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 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.

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.

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.

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 circumstances 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.

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.

He was soon at the bottom, and in the midst of the men, who were paralysed by 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 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.

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 methods 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 after the miner, working the wheel, and by the imperfect light thus given forth he 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; and two-thirds were left.

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 anxiety which prevailed in the colliery districts as to the invention of a lamp which should give light enough for the miners to work by without exploding the fire-damp.  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 his experiments to be fraught with danger.  One of the sinkers, 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 inflammable gas in the Killingworth pit.  According to the explanation afterwards given by him, 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 towards the flame; and such a lamp, he thought, might be taken into a dangerous atmosphere without risk of exploding.

Stephenson proceeded to order a lamp to be made by a Newcastle tinman, according to his plan; and at the same time he directed a glass to be made for the lamp at the Northumberland Glass House.  Both were received by him from the makers on the 21st October, and the lamp was taken to Killingworth for the purpose of immediate experiment.

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 mixtures 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 4/10 of an inch in diameter, the necessary current was 9 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 able to replace.”

In order to correct the defect of his first lamp he resolved 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 explosive gas passing downwards, at the same time that the “burnt air” (the cause, in his opinion, of the lamp going out) would be more effectually dislodged.  He accordingly took the lamp to a tinman in Newcastle, and had it altered so that the air was admitted by three small tubes inserted in the bottom of the lamp, 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 November, and was found to burn better than the first, and to be perfectly safe.  But as it did not yet come quite up 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 explosion would be the same.

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 recognised; and 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, pursuing his experiments in obscurity, with a view only to usefulness; the other was the scientific prodigy of his day, 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.  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.”

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 for raising 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 independent 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 labours.  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.

This was not at all in George’s line.  He had never appeared in print; and it seemed to him a more formidable thing to write a letter for “the papers” than to invent a safety-lamp or design a locomotive.  However, he called to his aid his son Robert, set him down before a sheet of foolscap, and told him to “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 the penmanship was called in question, and he had written his best.  Mr. Brandling, however, revised the letter, which was shortly after published in the local journals.

However great the merits of Stephenson in connexion with the invention of the tube safety-lamp, they cannot be regarded as detracting 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 even appears that Mr. Smithson Tennant and Dr. Wollaston had observed the same fact several years before, though neither Stephenson nor Davy knew 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.

When the question of priority was under discussion at the studio of Mr. Lough, the sculptor, 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 unbiassed 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, independent of all that Sir Humphry Davy had ever done in the matter.”

Stephenson’s experiments on fire-damp, and his labours in connexion with the invention of the safety-lamp, occupied but a small portion of his time, which was necessarily devoted for the most part to the ordinary business of the colliery.  From the day of his appointment as engine-wright, one of the subjects which particularly occupied his attention was the best practical method of winning and raising the coal.  He was one of the first to introduce steam machinery underground with the latter object.  Indeed, the Killingworth mines came to be regarded as the models of the district; the working arrangements generally being conducted in a skilful and efficient manner, reflecting the highest credit on the colliery engineer.

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

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

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

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

Although Stephenson’s locomotive engines were in daily use for many years on the Killingworth Railway, they excited comparatively little interest.  They were no longer experimental, but had become an established tractive power.  The experience of years had proved that they worked more steadily, drew heavier loads, and were, on the whole, considerably more economical than horses.  Nevertheless eight years passed before another locomotive railway was constructed and opened for the purposes of coal or other traffic.

Stephenson had no means of bringing his important invention prominently under the notice of the public.  He himself knew well its importance, and he already anticipated its eventual general adoption; but being an unlettered man, he could not give utterance to the thoughts which brooded within him on the subject.  Killingworth Colliery lay far from London, the centre of scientific life in England.  It was visited by no savans nor literary men, who might have succeeded in introducing to notice the wonderful machine of Stephenson.  Even the local chroniclers seem to have taken no notice of the Killingworth Railway.