some of them thought, out of season. He pointed out the greater
convenience of locomotive power for the purposes of a public highway,
likening it to a series of short unconnected chains, any one of which
could be removed and another substituted without interruption to the
traffic; whereas the fixed-engine system might be regarded in the light
of a continuous chain extending between the two termini, the failure of
any link of which would derange the whole. But the fixed engine party
was very strong at the board, and, led by Mr. Cropper, they urged the
propriety of forthwith adopting the report of Messrs. Walker and
Rastrick. Mr. Sandars and Mr. William Rathbone, on the other hand,
desired that a fair trial should be given to the locomotive; and they
with reason objected to the expenditure of the large capital necessary
to construct the proposed engine-houses, with their fixed engines,
ropes, and machinery, until they had tested the powers of the locomotive
as recommended by their own engineer. George Stephenson continued to
urge upon them that the locomotive was yet capable of great
improvements, if proper inducements were held out to inventors and
machinists to make them; and he pledged himself that, if time were
given him, he would construct an engine that should satisfy their
requirements, and prove itself capable of working heavy loads along the
railway with speed, regularity, and safety. At length, influenced by his
persistent earnestness not less than by his arguments, the directors, at
the suggestion of Mr. Harrison, determined to offer a prize of L500 for
the best locomotive engine, which, on a certain day, should be produced
on the railway, and perform certain specified conditions in the most
satisfactory manner.[7]
The requirements of the directors as to speed were not excessive. All
that they asked for was that ten miles an hour should be maintained.
Perhaps they had in mind the animadversions of the _Quarterly Review_ on
the absurdity of travelling at a greater velocity, and also the remarks
published by Mr. Nicholas Wood, whom they selected to be one of the
judges of the competition, in conjunction, with Mr. Rastrick, of
Stourbridge, and Mr. Kennedy, of Manchester.
It was now felt that the fate of railways in a great measure depended
upon the issue of this appeal to the mechanical genius of England. When
the advertisement of the prize for the best locomotive was published,
scientific men began more particularly to direct their attention to the
new power which was thus struggling into existence. In the meantime
public opinion on the subject of railway working remained suspended, and
the progress of the undertaking was watched with intense interest.
During the progress of this important controversy with reference to the
kind of power to be employed in working the railway, George Stephenson
was in constant communication with his son Robert, who made frequent
visits to Liverpool for the purpose of assisting his father in the
preparation of his reports to the board on the subject. Mr. Swanwick
remembers the vivid interest of the evening discussions which then took
place between father and son as to the best mode of increasing the
powers and perfecting the mechanism of the locomotive. He wondered at
their quick perception and rapid judgment on each other's suggestions;
at the mechanical difficulties which they anticipated and provided for
in the practical arrangement of the machine; and he speaks of these
evenings as most interesting displays of two actively ingenious and able
minds stimulating each other to feats of mechanical invention, by which
it was ordained that the locomotive engine should become what it now is.
These discussions became more frequent, and still more interesting,
after the public prize had been offered for the best locomotive by the
directors of the railway, and the working plans of the engine which they
proposed to construct had to be settled.
One of the most important considerations in the new engine was the
arrangement of the boiler, and the extension of its heating surface to
enable steam enough to be raised rapidly and continuously for the
purpose of maintaining high rates of speed--the effect of high pressure
engines being ascertained to depend mainly upon the quantity of steam
which the boiler can generate, and upon its degree of elasticity when
produced. The quantity of steam so generated, it will be obvious, must
chiefly depend upon the quantity of fuel consumed in the furnace, and,
by necessary consequence, upon the high rate of temperature maintained
there.
It will be remembered that in Stephenson's first Killingworth engines he
invited and applied the ingenious method of stimulating combustion in
the furnace by throwing the waste steam into the chimney after
performing its office in the cylinders, thereby accelerating the ascent
of the current of air, greatly increasing the draught, and consequently
the temperature of the fire. This plan was adopted by him, as we have
seen, as early as 1815, and it was so successful that he himself
attributed to it the greater economy of the locomotive as compared with
horse-power. Hence the continuance of its use upon the Killingworth
Railway.
Though the adoption of the steam blast greatly quickened combustion and
contributed to the rapid production of high-pressure steam, the limited
amount of heating surface presented to the fire was still felt to be an
obstacle to the complete success of the locomotive engine. Mr.
Stephenson endeavoured to overcome this by lengthening the boilers and
increasing the surface presented by the flue-tubes. The "Lancashire
Witch," which he built for the Bolton and Leigh Railway, and used in
forming the Liverpool and Manchester Railway embankments, was
constructed with a double tube, each of which contained a fire, and
passed longitudinally through the boiler. But this arrangement
necessarily led to a considerable increase in the weight of those
engines, which amounted to about twelve tons each; and as six tons was
the limit allowed for engines admitted to the Liverpool competition, it
was clear that the time was come when the Killingworth engine must
undergo a farther important modification.
For many years previous to this period, ingenious mechanics had been
engaged in attempting to solve the problem of the best and most
economical boiler for the production of high-pressure steam.
The use of tubes in boilers for increasing the heating surface had long
been known. As early as 1780, Matthew Boulton employed copper tubes
longitudinally in the boiler of the Wheal Busy engine in Cornwall--the
fire passing _through_ the tubes--and it was found that the production
of steam was thereby considerably increased. The use of tubular boilers
afterwards became common in Cornwall. In 1803, Woolf, the Cornish
engineer, patented a boiler with tubes, with the same object of
increasing the heating surface. The water was _inside_ the tubes, and
the fire of the boiler outside. Similar expedients were proposed by
other inventors. In 1815 Trevithick invented his light high-pressure
boiler for portable purposes, in which, to "expose a large surface to
the fire," he constructed the boiler of a number of small perpendicular
tubes "opening into a common reservoir at the top." In 1823 W. H. James
contrived a boiler composed of a series of annular wrought-iron tubes,
placed side by side and bolted together, so as to form by their union a
long cylindrical boiler, in the centre of which, at the end, the
fireplace was situated. The fire played round the tubes, which contained
the water. In 1826 James Neville took out a patent for a boiler with
vertical tubes surrounded by the water, through which the heated air of
the furnace passed, explaining also in his specification that the tubes
might be horizontal or inclined, according to circumstances. Mr.
Goldsworthy, the persevering adaptor of steam-carriages to travelling on
common roads, applied the tubular principle in the boiler of his engine,
in which the steam was generated _within_ the tubes; while the boiler
invented by Messrs. Summer and Ogle for their turnpike-road
steam-carriage consisted of a series of tubes placed vertically over the
furnace, through which the heated air passed before reaching the
chimney.
About the same time George Stephenson was trying the effect of
introducing small tubes in the boilers of his locomotives, with the
object of increasing their evaporative power. Thus, in 1829, he sent to
France two engines constructed at the Newcastle works for the Lyons and
St. Etienne Railway, in the boilers of which tubes were placed
containing water. The heating surface was thus considerably increased;
but the expedient was not successful, for the tubes, becoming furred
with deposit, shortly burned out and were removed. It was then that M.
Seguin, the engineer of the railway, pursuing the same idea, is said to
have adopted his plan of employing horizontal tubes through which the
heated air passed in streamlets, and for which he took out a French
patent.
In the meantime Mr. Henry Booth, secretary to the Liverpool and
Manchester Railway, whose attention had been directed to the subject on
the prize being offered for the best locomotive to work that line,
proposed the same method, which, unknown to him, Matthew Boulton had
employed but not patented, in 1780, and James Neville had patented, but
not employed, in 1826; and it was carried into effect by Robert
Stephenson in the construction of the "Rocket," which won the prize at
Rainhill in October, 1829. The following is Mr. Booth's account in a
letter to the author:
"I was in almost daily communication with Mr. Stephenson at the time,
and I was not aware that he had any intention of competing for the prize
till I communicated to him my scheme of a multitubular boiler. This new
plan of boiler comprised the introduction of numerous small tubes, two
or three inches in diameter, and less than one-eighth of an inch thick,
through which to carry the fire instead of a single tube or flue
eighteen inches in diameter, and about half an inch thick, by which
plan we not only obtain a very much larger heating surface, but the
heating surface is much more effective, as there intervenes between the
fire and the water only a thin sheet of copper or brass, not an eighth
of an inch thick, instead of a plate of iron of four times the
substance, as well as an inferior conductor of heat.
"When the conditions of trial were published, I communicated my
multitubular plan to Mr. Stephenson, and proposed to him that we should
jointly construct an engine and compete for the prize. Mr. Stephenson
approved the plan, and agreed to my proposal. He settled the mode in
which the fire-box and tubes were to be mutually arranged and connected,
and the engine was constructed at the works of Messrs. Robert Stephenson
& Co., Newcastle-on-Tyne.
"I am ignorant of M. Seguin's proceedings in France, but I claim to be
the inventor in England, and feel warranted in stating, without
reservation, that until I named my plan to Mr. Stephenson, with a view
to compete for the prize at Rainhill, it had not been tried, and was not
known in this country."
From the well-known high character of Mr. Booth, we believe his
statement to be made in perfect good faith, and that he was as much in
ignorance of the plan patented by Neville as he was of that of Seguin.
As we have seen, from the many plans of tubular boilers invented during
the preceding thirty years, the idea was not by any means new; and we
believe Mr. Booth to be entitled to the merit of inventing the method by
which the multitubular principle was so effectually applied in the
construction of the famous "Rocket" engine.
The principal circumstances connected with the construction of the
"Rocket," as described by Robert Stephenson to the author, may be
briefly stated. The tubular principle was adopted in a more complete
manner than had yet been attempted. Twenty-five copper tubes, each three
inches in diameter, extended from one end of the boiler to the other,
the heated air passing through them on its way to the chimney; and the
tubes being surrounded by the water of the boiler, it will be obvious
that a large extension of the heating surface was thus effectually
secured. The principal difficulty was in fitting the copper tubes in the
boiler ends so as to prevent leakage. They were manufactured by a
Newcastle coppersmith, and soldered to brass screws which were screwed
into the boiler ends, standing out in great knobs. When the tubes were
thus fitted, and the boiler was filled with water, hydraulic pressure
was applied; but the water squirted out at every joint, and the factory
floor was soon flooded. Robert went home in despair; and in the first
moment of grief he wrote to his father that the whole thing was a
failure. By return of post came a letter from his father, telling him
that despair was not to be thought of--that he must "try again;" and he
suggested a mode of overcoming the difficulty, which his son had
already anticipated and proceeded to adopt. It was, to bore clean holes
in the boiler ends, fit in the smooth copper tubes as tightly as
possible, solder up, and then raise the steam. This plan succeeded
perfectly, the expansion of the copper tubes completely filling up all
interstices, and producing a perfectly water-tight boiler, capable of
withstanding extreme external pressure.
The mode of employing the steam-blast for the purpose of increasing the
draught in the chimney was also the subject of numerous experiments.
When the engine was first tried, it was thought that the blast in the
chimney was not sufficiently strong for the purpose of keeping up the
intensity of fire in the furnace, so as to produce high-pressure steam
with the required velocity. The expedient was therefore adopted of
hammering the copper tubes at the point at which they entered the
chimney, whereby the blast was considerably sharpened; and on a farther
trial it was found that the draught was increased to such an extent as
to enable abundance of steam to be raised. The rationale of the blast
may be simply explained by referring to the effect of contracting the
pipe of a water-hose, by which the force of the jet of water is
proportionately increased. Widen the nozzle of the pipe, and the jet is
in like manner diminished. So it is with the steam-blast in the chimney
of the locomotive.
Doubts were, however, expressed whether the greater draught obtained by
the contraction of the blast-pipe was not counterbalanced in some degree
by the negative pressure upon the piston. Hence a series of experiments
was made with pipes of different diameters, and their efficiency was
tested by the amount of vacuum that was produced in the smoke-box. The
degree of rarefaction was determined by a glass tube fixed to the bottom
of the smoke-box and descending into a bucket of water, the tube being
open at both ends. As the rarefaction took place, the water would, of
course, rise in the tube, and the height to which it rose above the
surface of the water in the bucket was made the measure of the amount of
rarefaction. These experiments proved that a considerable increase of
draught was obtained by the contraction of the orifice; accordingly, the
two blast-pipes opening from the cylinders into either side of the
"Rocket" chimney, and turned up within it, were contracted slightly
below the area of the steam-ports, and before the engine left the
factory, the water rose in the glass tube three inches above the water
in the bucket.
The other arrangements of the "Rocket" were briefly these: the boiler
was cylindrical, with flat ends, six feet in length, and three feet four
inches in diameter. The upper half of the boiler was used as a reservoir
for the steam, the lower half being filled with water. Through the lower
part the copper tubes extended, being open to the fire-box at one end,
and to the chimney at the other. The fire-box, or furnace, two feet wide
and three feet high, was attached immediately behind the boiler, and was
also surrounded with water. The cylinders of the engine were placed on
each side of the boiler, in an oblique position, one end being nearly
level with the top of the boiler at its after end, and the other
pointing toward the centre of the foremost or driving pair of wheels,
with which the connection was directly made from the piston-rod to a pin
on the outside of the wheel. The engine, together with its load of
water, weighed only four tons and a quarter; and it was supported on
four wheels, not coupled. The tender was four-wheeled, and similar in
shape to a waggon--the foremost part holding the fuel, and the hind part
a water cask.
When the "Rocket" was finished it was placed upon the Killingworth
Railway for the purpose of experiment. The new boiler arrangement was
found perfectly successful. The steam was raised rapidly and
continuously, and in a quantity which then appeared marvellous. The same
evening Robert despatched a letter to his father at Liverpool, informing
him, to his great joy, that the "Rocket" was "all right," and would be
in complete working trim by the day of trial. The engine was shortly
after sent by waggon to Carlisle, and thence shipped for Liverpool.
The time so much longed for by George Stephenson had now arrived, when
the merits of the passenger locomotive were about to be put to the
test. He had fought the battle for it until now almost single-handed.
Engrossed by his daily labours and anxieties, and harassed by
difficulties and discouragements which would have crushed the spirit of
a less resolute man, he had held firmly to his purpose through good and
through evil report. The hostility which he experienced from some of the
directors opposed to the adoption of the locomotive was the circumstance
that caused him the greatest grief of all; for where he had looked for
encouragement, he found only carping and opposition. But his pluck never
failed him; and now the "Rocket" was upon the ground to prove, to use
his own words, "whether he was a man of his word or not."
On the day appointed for the great competition of locomotives at
Rainhill the following engines were entered for the prize:
1. Messrs. Braithwaite and Ericsson's "Novelty."
2. Mr. Timothy Hackworth's "Sanspareil."
3. Messrs. R. Stephenson & Co.'s "Rocket."
4. Mr. Burstall's "Perseverance."
The ground on which the engines were to be tried was a level piece of
railroad, about two miles in length. Each was required to make twenty
trips, or equal to a journey of seventy miles, in the course of the day,
and the average rate of travelling was to be not under ten miles an
hour. It was determined that, to avoid confusion, each engine should be
tried separately, and on different days.
The day fixed for the competition was the 1st of October, but, to allow
sufficient time to get the locomotives into good working order, the
directors extended it to the 6th. It was quite characteristic of the
Stephensons that, although their engine did not stand first on the list
for trial, it was the first that was ready, and it was accordingly
ordered out by the judges for an experimental trip. Yet the "Rocket" was
by no means the "favourite" with either the judges or the spectators.
Nicholas Wood has since stated that the majority of the judges were
strongly predisposed in favour of the "Novelty," and that "nine-tenths,
if not ten-tenths, of the persons present were against the "Rocket"
because of its appearance." Nearly every person favoured some other
engine, so that there was nothing for the "Rocket" but the practical
test. The first trip made by it was quite successful. It ran about
twelve miles, without interruption, in about fifty-three minutes.
The "Novelty" was next called out. It was a light engine, very compact
in appearance, carrying the water and fuel upon the same wheels as the
engine. The weight of the whole was only three tons and one
hundred-weight. A peculiarity of this engine was that the air was driven
or _forced_ through the fire by means of bellows. The day being now far
advanced, and some dispute having arisen as to the method of assigning
the proper load for the "Novelty," no particular experiment was made
further than that the engine traversed the line by way of exhibition,
occasionally moving at the rate of twenty-four miles an hour. The
"Sanspareil," constructed by Mr. Timothy Hackworth, was next exhibited,
but no particular experiment was made with it on this day. This engine
differed but little in its construction from the locomotive last
supplied by the Stephensons to the Stockton and Darlington Railway, of
which Mr. Hackworth was the locomotive foreman.
The contest was postponed until the following day; but, before the
judges arrived on the ground, the bellows for creating the blast in the
"Novelty" gave way, and it was found incapable of going through its
performance. A defect was also detected in the boiler of the
"Sanspareil," and some further time was allowed to get it repaired. The
large number of spectators who had assembled to witness the contest were
greatly disappointed at this postponement; but, to lessen it, Stephenson
again brought out the "Rocket," and, attaching it to a coach containing
thirty persons, he ran them along the line at a rate of from twenty-four
to thirty miles an hour, much to their gratification and amazement.
Before separating, the judges ordered the engine to be in readiness by
eight o'clock on the following morning, to go through its definite trial
according to the prescribed conditions.
On the morning of the 8th of October the "Rocket" was again ready for
the contest. The engine was taken to the extremity of the stage, the
fire-box was filled with coke, the fire lighted, and the steam raised
until it lifted the safety-valve loaded to a pressure of fifty pounds to
the square inch. This proceeding occupied fifty-seven minutes. The
engine then started on its journey, dragging after it about thirteen
tons' weight in waggons, and made the first ten trips backward and
forward along two miles of road, running the thirty-five miles,
including stoppages, in an hour and forty-eight minutes. The second ten
trips were in like manner performed in two hours and three minutes. The
maximum velocity attained during the trial trip was twenty-nine miles an
hour, or about three times the speed that one of the judges of the
competition had declared to be the limit of possibility. The average
speed at which the whole of the journeys was performed was fifteen miles
an hour, or five miles beyond the rate specified in the conditions
published by the company. The entire performance excited the greatest
astonishment among the assembled spectators; the directors felt
confident that their enterprise was now on the eve of success; and
George Stephenson rejoiced to think that, in spite of all false prophets
and fickle counsellors, the locomotive system was now safe. When the
"Rocket," having performed all the conditions of the contest, arrived at
the "grand stand" at the close of its day's successful run, Mr.
Cropper--one of the directors favourable to the fixed engine
system--lifted up his hands, and exclaimed, "Now has George Stephenson
at last delivered himself...."
The "Rocket" had eclipsed the performance of all locomotive engines that
had yet been constructed, and outstripped even the sanguine expectations
of its constructors. It satisfactorily answered the report of Messrs.
Walker and Rastrick, and established the efficiency of the locomotive
for working the Liverpool and Manchester Railway, and, indeed, all
future railways. The "Rocket" showed that a new power had been born into
the world, full of activity and strength, with boundless capability of
work. It was the simple but admirable contrivance of the steam-blast,
and its combination with the multitubular boiler, that at once gave
locomotion a vigorous life, and secured the triumph of the railway
system.[8]
[Illustration: The "Rocket"]
FOOTNOTES:
[7] The conditions were these:
1. The engine must effectually consume its own smoke.