He was still, however, desirous of testing the practicability of
employing locomotive power in working the coal down to Lemington, and he
determined on another trial.  He accordingly directed his engine-wright
to proceed with the building of a third engine in the Wylam workshops.
This new locomotive had a single 8-inch cylinder, was provided with a
fly-wheel like its predecessor, and the driving-wheel was cogged on one
side to enable it to travel in the rack-rail laid along the road.  This
engine proved more successful than the former one; and it was found
capable of dragging eight or nine loaded waggons, though at the rate of
little more than a mile an hour, from the colliery to the shipping-place.
It sometimes took six hours to perform the journey of five miles.  Its
weight was found too great for the road, and the cast-iron plates were
constantly breaking.  It was also very apt to get off the rack-rail, and
then it stood still.  The driver was one day asked how he got on?  "Get
on?" said he, "we don't get on; we only get off!"  On such occasions,
horses had to be sent to drag the waggons as before, and others to haul
the engine back to the work-shops.  It was constantly getting out of
order; its plugs, pumps, or cranks, got wrong; it was under repair as
often as at work; at length it became so cranky that the horses were
usually sent out after it to drag it when it gave up; and the workmen
generally declared it to be a "perfect plague."  Mr. Blackett did not
obtain credit amongst his neighbours for these experiments.  Many laughed
at his machines, regarding them only in the light of
crotchets,--frequently quoting the proverb that "a fool and his money are
soon parted."  Others regarded them as absurd innovations on the
established method of hauling coal; and pronounced that they would "never
answer."

Notwithstanding, however, the comparative failure of this 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 adhesion enough between
the wheel and the rail by the mere weight of the engine, and he proceeded
to make a series of experiments for the purpose of determining this
problem.  He had a frame placed on four wheels, and fitted up with
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 found the proportion which the power bore to the weight, he
demonstrated by successive experiments that the weight of the engine
would of itself produce sufficient adhesion to enable it to draw upon a
smooth railroad the requisite number of waggons in all kinds of weather.
And thus was the fallacy which had heretofore prevailed on this subject
completely exploded, and it was satisfactorily proved that rack-rails,
toothed wheels, endless chains, and legs, were alike unnecessary for the
efficient traction of loaded waggons upon a moderately level road.

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

                     [Picture: Improved Wylam Engine]

As may readily be imagined, the jets of steam from the piston, blowing
off into the air at high pressure while the engine was in motion, caused
considerable annoyance to horses 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 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 hearing.  Much interruption was thus caused to the
working of the railway, and it excited considerable dissatisfaction
amongst the workmen.  The following plan was adopted to abate the
nuisance: a reservoir was provided immediately behind the chimney (as
shown in the preceding cut) into which the waste steam was thrown after
it had performed its office in the cylinder; and from this reservoir, the
steam gradually escaped into the atmosphere without noise.

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

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

In the first place Stephenson resolved to make himself thoroughly
acquainted with what had already been done.  Mr. Blackett's engines were
working daily at Wylam, past the cottage where he had been born; and
thither he frequently went to inspect the improvements made by Mr.
Blackett from time to time both in the locomotive and in the plateway
along which it worked.  Jonathan Foster informed us that, after one of
these visits, Stephenson declared to him his conviction that a much more
effective engine might be made, that should work more steadily and draw
the load more effectively.

He had also the advantage, about the same time, of seeing one of
Blenkinsop's Leeds engines, which was placed on the tramway leading from
the collieries of Kenton and Coxlodge, on the 2nd September, 1813.  This
locomotive drew sixteen chaldron waggons containing an aggregate weight
of seventy tons, at the rate of about three miles an hour.  George
Stephenson and several of the Killingworth men were amongst the crowd of
spectators that day; and after examining the engine and observing its
performances, he observed to his companions, that "he thought he could
make a better engine than that, to go upon legs."  Probably he had heard
of the invention of Brunton, whose patent had by this time been
published, and proved the subject of much curious speculation in the
colliery districts.  Certain it is, that, shortly after the inspection of
the 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, had proved practical failures.  Mr.
Blackett's was as yet both clumsy and expensive.  Chapman's had been
removed from the Heaton tramway in 1812, and was regarded as a total
failure.  And the Blenkinsop engine at 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 soon after blown up, there was an end of that
engine; and the colliery owners did not feel encouraged to try any
further experiment.

An efficient and economical working locomotive, therefore, still remained
to be invented; and to accomplish this object Mr. Stephenson now applied
himself.  Profiting by what his predecessors had done, warned by their
failures and encouraged by their partial successes, he commenced his
labours.  There was still wanting the man who should accomplish for the
locomotive what James Watt had done for the steam-engine, and combine in
a complete form the best points in the separate plans of others,
embodying with them such original inventions and adaptations of his own
as to 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.

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

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

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

                         [Picture: The Spur-gear]

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

The engine was, after much labour and anxiety, and frequent alterations
of parts, at length brought to completion, having been about ten months
in hand.  It was placed upon the Killingworth Railway on the 25th July,
1814; and its powers were tried on the same day.  On an ascending
gradient of 1 in 450, the engine succeeded in drawing after it eight
loaded carriages of thirty tons' weight at about four miles an hour; and
for some time after it continued regularly at work.

Although a considerable advance upon previous locomotives, "Blutcher" (as
the engine was popularly called) was nevertheless a somewhat 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.

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 point of cost.  The fate of the
locomotive in a great measure depended on this very engine.  Its speed
was not beyond that of a horse's walk, and the heating surface presented
to the fire being comparatively small, sufficient steam could not be
raised to enable it to accomplish more on an average than about four
miles an hour.  The result was anything but decisive; and the locomotive
might have been condemned as useless, had not our engineer at this
juncture applied the steam-blast, and by its means carried his experiment
to a triumphant issue.

The steam, after performing its duty in the cylinders, was at first
allowed to escape into the open atmosphere with a hissing blast, to the
terror of horses and cattle.  It was complained of as a nuisance; and an
action at law against the colliery lessees was threatened unless it was
stopped.  Stephenson's attention had been drawn to the much greater
velocity with which the steam issued from the exit pipe compared with
that at which the smoke escaped from the chimney.  He conceived that, by
conveying the eduction steam into the chimney, by means of a small pipe,
after it had performed its office in the cylinders, allowing it to escape
in a vertical direction, its velocity would be imparted to the smoke from
the fire, or to the ascending current of air in the chimney, thereby
increasing the draft, and consequently the intensity of combustion in the
furnace.

The experiment was no sooner made than the power of the engine was at
once more than doubled; combustion was stimulated by the blast;
consequently the capability of the boiler to generate steam was greatly
increased, and the effective power of the engine augmented in precisely
the same proportion, without in any way adding to its weight.  This
simple but beautiful expedient was really fraught with the most important
consequences to railway communication; and it is not too much to say that
the success of the locomotive has in a great measure been the result of
its adoption.  Without the steam-blast, by means of which the intensity
of combustion is maintained at its highest point, producing a
correspondingly rapid evolution of steam, high rates of speed could not
have been kept up; the advantages of the multi-tubular boiler (afterwards
invented) could never have been fairly tested; and locomotives might
still have been dragging themselves unwieldily along at little more than
five or six miles an hour.

The steam-blast had scarcely been adopted, with so decided a success,
when Stephenson, observing the numerous defects in his engine, and
profiting by the experience which he had already acquired, determined to
construct a second engine, in which to embody his improvements in their
best form.  Careful and cautious observation of the working of his
locomotive had convinced him that the complication arising out of the
action of the two cylinders being combined by spur-wheels would prevent
its coming into practical use.  He accordingly directed his attention to
an entire change in the construction and mechanical arrangements of the
machine; and in the following year, conjointly with Mr. Dodds, who
provided the necessary funds, he took out a patent, dated the 28th of
February, 1815, for an engine which combined in a remarkable degree the
essential requisites of an economical locomotive; that is to say, few
parts, simplicity in their action, and directness in the mode by which
the power was communicated to the wheels supporting the engine.

This locomotive, like the first, had two vertical cylinders, which
communicated _directly_ with each pair of the four wheels that supported
the engine, by means of a cross head and a pair of connecting rods.  But
in attempting to establish a direct communication between the cylinders
and the wheels that rolled upon the rails, considerable difficulties
presented themselves.  The ordinary joints could not be employed to unite
the parts of the engine, which was a rigid mass, with the wheels lolling
upon the irregular surface of the rails; for it was evident that the two
rails of the line of way--more especially in those early days of
imperfect construction of the permanent road--could not always be
maintained at the same level,--that the wheel at one end of the axle
might be depressed into one part of the line which had subsided, whilst
the other wheel would be comparatively elevated; and in such a position
of the axle and wheels, it was obvious that a rigid communication between
the cross head and the wheels was impracticable.  Hence it became
necessary to form a joint at the top of the piston-rod where it united
with the cross head, so as to permit the cross head to preserve complete
parallelism with the axle of the wheels with which it was in
communication.

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

A locomotive was constructed upon this plan in 1815, and was found to
answer extremely well.  But at that period the mechanical skill of the
country was not equal to forging cranked axles of the soundness and
strength necessary to stand the jars incident to locomotive work.
Stephenson was accordingly compelled to fall back upon a substitute,
which, although less simple and efficient, was within the mechanical
capabilities of the workmen of that day, in respect of construction as
well as repair.  He adopted a chain which rolled over indented wheels
placed on the centre of each axle, and was so arranged that the two pairs
of wheels were effectually coupled and made to keep pace with each other.
The chain, however, after a few years' use, became stretched; and then
the engines were liable to irregularity in their working, especially in
changing from working back to working forward again.  Eventually the
chain was laid aside, and the front and hind wheels were united by rods
on the outside, instead of by rods and crank axles inside, as specified
in the original patent.  This expedient completely answered the purpose
required, without involving any expensive or difficult workmanship.

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




CHAPTER VI.
INVENTION OF THE "GEORDY" SAFETY-LAMP.


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

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

One day, in 1814, a workman hurried into Stephenson's cottage with the
startling information that the deepest main of the colliery was on fire!
He immediately hastened to the pit-head, about a hundred yards off,
whither the women and children of the colliery were running, with
wildness and terror depicted in every face.  In a commanding voice
Stephenson ordered the engineman to lower him down the shaft in the
corve.  There was peril, it might be death, before him, but he must go.

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.

                    [Picture: The Pit Head, West Moor]

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, the people were saved from death, and the mine was
preserved.

This anecdote of Stephenson was related to the writer, near the
pit-mouth, by one of the men who had been present and helped to build up
the brick wall by which the fire was stayed, though several workmen were
suffocated.  He related that, when down the pit some days after, seeking
out the dead bodies, the cause of the accident was the subject of
conversation, and Stephenson was asked, "Can nothing be done to prevent
such awful occurrences?"  His reply was that he thought something might
be done.  "Then," said the other, "the sooner you start 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 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.

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 attempted towards the invention of such a lamp
by Dr. Clanny, of Sunderland, who, in 1813, 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 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 on the 9th of November
following, 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 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.

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 made, and shown
to several of the head men about the works.

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.

"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 yet 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 the
Churchyard, but just as I was about to pass the wicket, I saw what I
thought was a white figure moving about amongst the grave-stones.  I took
it for a ghost!  My heart fluttered, and I was in a great fright, but to
Wood'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 lanthorn set upon one of the
gravestones!  I found Wood at home, and in a few minutes he was mounted
and off to my father's.  When I got back, 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 towards 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 made more foul
for the purpose of the experiment.  After waiting about an hour, Moodie,
whose practical experience of fire-damp in pits was greater 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 towards 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. {95}

Advancing to the place of danger, and entering within the fouled air, his
lighted lamp in hand, Stephenson held it finally 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 him repeat his experiment, 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 became almost full
of fire; and then it smothered out.  Again returning to his companions,
he relighted the lamp, and repeated the experiment 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.

Before leaving the pit, Stephenson expressed his opinion that by an
alteration of the lamp which he then 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, under the flame.  After making some
experiments on the air collected at the blower, by bladders which were
mounted with tubes of various diameters, he satisfied himself that, when
the tube was reduced to a certain diameter, the foul air 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 a place purposely made foul as before; on
this occasion a larger number of persons ventured to witness them, and
they 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 horizontally, 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 books, nor intercourse with
scientific men, nor anything that could assist him in his investigation,
besides his own indefatigable spirit of inquiry, he contrived a rude
apparatus by which he tested the explosive properties of the gas and the
velocity of current (for this was the direction of his inquiries)
necessary to enable the explosive gas to pass through tubes of different
diameters.  In making these experiments in his humble cottage at the West
Moor, Nicholas Wood and George's son Robert usually acted as his
assistants, and sometimes the gentlemen of the neighbourhood interested
in coal-mining attended as spectators.

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."

Stephenson followed up those 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 further proof to him of the soundness of the course
he was pursuing.

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.

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 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 November he went over to Newcastle to order his third lamp from
a plumber in that town.  The plumber referred him to his clerk, 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 November.
At that time 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 afterwards 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 afterwards 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 October, 1815; the _second_ was tried on
the 4th November; but it was not until the 9th 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.

             [Picture: Davy's and Stephenson's Safety Lamps]

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 Gurike 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 afterwards framed.  Our inventor had been pursuing the
Baconian method, though he did not think of that, but of inventing a safe
lamp, which he knew could only be done through the process of repeated
experiment.  He experimented upon the fire-damp at the blowers in the
mine, and also by means of the apparatus which was blown up in his
cottage, as above described by himself.  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 having pointed out 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, and a meeting was appointed for the purpose
of receiving his explanations, on the evening of the 5th 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 his reserve, 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
recognised; and Sir Humphry Davy carried off the larger share of the
_eclat_ 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."