fire-place is constructed in the following manner:—A tube enters
the cylindrical boiler at one end; and, proceeding onwards near
the other extremity, is turned and recurved, so as to be carried
back parallel to the direction in which it entered. It is thus
conducted out of the boiler, at another part of the same end at
which it entered. One of the ends of this tube communicates with
the chimney E, which is carried upwards as represented in the
figure. The other mouth is furnished [Pg325] with a door; and in
it is placed the grate, which is formed of horizontal bars,
dividing the tube into two parts; the upper part forming the
fire-place, and the lower the ash-pit. The fuel is maintained in a
state of combustion, on the bars, in that part of the tube
represented at C D; and the flame is carried by the draught of the
chimney round the curved flue, and issues at E into the chimney.
The flame is thus conducted through the water, so as to expose the
latter to as much heat as possible.
[Illustration: _Fig._ 84.]
A section of the cylinder is represented at F, immersed in the
boiler, except a few inches of the upper end, where the four-way
cock G is placed for regulating the admission of the steam. A tube
is represented at H, which leads from this four-way cock into the
chimney; so that the waste steam, after working the piston, is
carried off through this tube, and passes into the chimney. The
upper end of the piston-rod is furnished with a cross-bar, which
is placed in a direction at right angles to the length of the
boiler, and also to the [Pg326] piston-rod. This bar is guided in
its motion by sliding on two iron perpendicular rods fixed to the
sides of the boiler, and parallel to each other. To the ends of
this cross-bar are joined two connecting rods, the lower ends of
which work two cranks fixed on an axis extending across and
beneath the boiler, and immediately under the centre of the
cylinder. This axis is sustained in bearings formed in the legs
which support the boiler, and upon its extremity is fixed the
fly-wheel as represented at B. A large-toothed wheel is placed on
this axis; which, being turned with the cranked axle, communicates
motion to other wheels; and through them, to any machinery which
the engine may be applied to move.
[Illustration: _Fig._ 85.]
As the four-way cock is represented in the figure, the steam
passes from the boiler through the curved passage G above the
piston, while the steam below the piston is carried off through a
tube which does not appear in the figure, by which it is conducted
to the tube H, and thence to the chimney. The steam, therefore,
which passes above the piston presses it downwards; while the
pressure upwards does not exceed that of the atmosphere. The
piston will therefore descend with a force depending on the excess
of the pressure of the steam produced in the boiler above the
atmospheric pressure. When the piston has arrived at the bottom of
the cylinder, the cock is made to assume the position represented
in _fig._ 85. This effect is produced by the motion of the
piston-rod. The steam now passes from above the piston, through
the tube H, into the chimney, while the steam from the boiler is
conducted through another tube below the piston. The pressure
above the piston, in this case, does not exceed that of the
atmosphere; while the pressure below it will be that of the steam
in the boiler. The piston will therefore ascend with the
difference of these pressures. On the arrival of the piston at the
top of the cylinder, the four-way cock is again turned to the
position represented in _fig._ 85., and the piston again descends;
and in the same manner the process is continued. A safety-valve is
placed on the boiler at V, loaded with a weight W, proportionate
[Pg327] to the strength of the steam with which it is proposed to
work.
In the engines now described, this valve was frequently loaded at
the rate of from 60 to 80 lbs. on the square inch. As the boilers of
high-pressure engines were considered more liable to accidents from
bursting than those in which steam of a lower pressure was used,
greater precautions were taken against such effects. A second
safety-valve was provided, which was not left in the power of the
engine-man. By this means he had a power to diminish the pressure of
the steam, but could not increase it beyond the limit determined by
the valve which was removed from his interference. The greatest
cause of danger, however, arose from the water in the boiler being
consumed by evaporation faster than it was supplied; and therefore
falling below the level of the tube containing the furnace. To guard
against accidents arising from this circumstance, a hole was bored
in the boiler, at a certain depth, below which the water should not
be allowed to fall; and in this hole a plug of metal was soldered
with lead, or with some other metal, which would fuse at that
temperature which would expose the boiler to danger. Thus, in the
event of the water being exhausted, so that its level would fall
below the plug, the heat of the furnace would immediately melt the
solder, and the plug would fall out, affording a vent for the steam,
without allowing the boiler to burst. The mercurial steam-gauge,
already described, was also used as an additional security. When the
force of the steam exceeded the length of the column of mercury
which the tube would contain, the mercury would be blown out, and
the tube would give vent to the steam. The water by which the boiler
was replenished was forced into it by a pump worked by the engine.
In order to economise the heat, this water was contained in a tube
T, which surrounded the pipe H. As the waste steam, after working
the piston, passed off through H, it imparted a portion of its heat
to the water contained in the tube T, which was thus warmed to a
certain temperature before it was forced into the boiler by the
pump. Thus a part of the heat, which was originally [Pg328] carried
from the boiler in the form of steam, was returned again to the
boiler with the water with which it was fed.
It is evident that engines constructed in this manner may be
applied to all the purposes to which the condensing engines are
applicable.
(183.) Two years after the date of the patent of this engine, its
inventor constructed a machine of the same kind for the purpose of
moving carriages on railroads; and applied it successfully, in the
year 1804, on the railroad at Merthyr Tydvil, in South Wales. It
was in principle the same as that already described. The cylinder
however was in a horizontal position, the piston-rod working in
the direction of the line of road: the extremity of the
piston-rod, by means of a connecting rod, worked cranks placed on
the axletree, on which were fixed two cogged wheels: these worked
in others, by which their motion was communicated finally to
cogged wheels fixed on the axle of the hind wheels of the
carriage, by which this axle was kept in a state of revolution.
The hind wheels being fixed on the axletree, and turning with it,
were caused likewise to revolve; and so long as the weight of the
carriage did not exceed that which the friction of the road was
capable of propelling, the carriage would thus be moved forwards.
On this axle was placed a fly-wheel to continue the rotatory
motion at the termination of each stroke. The fore wheels are
described as being capable of turning like the fore wheels of a
carriage, so as to guide the vehicle. The projectors appear to
have contemplated, in the first instance, the use of this carriage
on common roads; but that notion seems to have been abandoned, and
its use was only adopted on the railroad before mentioned. On the
occasion of its first trial, it drew after it as many carriages as
contained ten tons of iron a distance of nine miles; which stage
it performed without any fresh supply of water, and travelled at
the rate of five miles an hour.
(184.) Capital and skill have of late years been directed with
extraordinary energy to the improvement of inland transport; and
this important instrument of national wealth and civilisation has
received a proportionate impulse. Effects are now witnessed,
which, had they been narrated a few years [Pg329] since, could
only have been admitted into the pages of fiction or volumes of
romance. Who could have credited the possibility of a ponderous
engine of iron, loaded with some hundred passengers, in a train of
carriages of corresponding magnitude, and a large quantity of
water and coal, taking flight from Manchester and arriving at
Liverpool, a distance of above thirty miles, in little more than
an hour? And yet this is a matter of daily and almost hourly
occurrence. The rapidity of transport thus attained is not less
wonderful than the weights transported. Its capabilities in this
respect far transcend the exigencies even of the two greatest
commercial marts in Great Britain. Loads, varying from fifty to
one hundred and fifty tons, are transported at the average rate of
fifteen miles an hour; and in one instance we have seen a load—we
should rather say a _cargo_—of waggons, conveying merchandise to
the amount of two hundred and thirty tons gross, transported from
Liverpool to Manchester at the average rate of twelve miles an
hour.
The astonishment with which such performances must be viewed,
might be qualified, if the art of transport by steam on railways
had been matured, and had attained that full state of perfection
which such an art is always capable of receiving from long
experience, aided by great scientific knowledge, and the unbounded
application of capital. But such is not the present case. The art
of constructing locomotive engines, so far from having attained a
state of maturity, has not even emerged from its infancy. So
complete was the ignorance of its powers which prevailed, even
among engineers, previous to the opening of the Liverpool railway,
that the transport of heavy goods was regarded as the chief object
of the undertaking, and its principal source of revenue. The
incredible speed of transport, effected even in the very first
experiments in 1830, burst upon the public, and on the scientific
world, with all the effect of a new and unlooked-for phenomenon.
On the unfortunate occasion which deprived this country of Mr.
Huskisson, the wounded body of that statesman was transported a
distance of about fifteen miles in twenty-five minutes, being at
the rate of thirty-six miles an hour. The revenue of the road
arising from passengers since its opening, [Pg330] has, contrary
to all that was foreseen, been nearly double that which has been
derived from merchandise. So great was the want of experience in
the construction of engines, that the company was at first
ignorant whether they should adopt large steam engines fixed at
different stations on the line, to pull the carriages from station
to station, or travelling engines to drag the loads the entire
distance. Having decided on the latter, they have, even to the
present moment, laboured under the disadvantage of the want of
that knowledge which experience alone can give. The engines have
been constantly varied in their weight and proportions, in their
magnitude and form, as the experience of each successive month has
indicated. As defects became manifest they were remedied;
improvements suggested were adopted; and each year produced
engines of such increased power and efficiency, that their
predecessors were abandoned, not because they were worn out, but
because they had been outstripped in the rapid march of
improvement. Add to this, that only one species of travelling
engine has been effectively tried; the capabilities of others
remain still to be developed; and even that form of engine which
has received the advantage of a course of experiments on so grand
a scale to carry it towards perfection, is far short of this
point, and still has defects, many of which, it is obvious, time
and experience will remove.
If, then, the locomotive engine, subject thus to all the
imperfections inseparable from a novel contrivance—with the
restrictions on the free application of skill and capital, arising
from the nature of the monopolies granted to railway companies—with
the disadvantage of very limited experience, the great parent of
practical improvement, having been submitted to experiments hitherto
only on a limited scale, and confined almost to one form of
machine;—if, under such disadvantages, such effects have been
produced as are now daily witnessed by the public, what may not be
looked for from this extraordinary power when the enterprise of the
country shall be more unfettered—when greater fields of experience
are opened—when time, ingenuity, and capital have removed or
diminished existing imperfections, and have brought to light new and
more powerful principles? This is not mere speculation [Pg331] on
abstract possibilities, but refers to what is in actual progress.
The points of greatest wealth and population—the centres of largest
capital and most active industry throughout the country—will soon
be connected by lines of railway; and various experiments are
proposed, with more or less prospect of success, for the application
of steam engines on stone roads where the intercourse is not
sufficient to render railways profitable.
The important commercial and political effects attending such
increased facility and speed in the transport of persons and goods,
are too obvious to require any very extended notice here. A part of
the price (and in many cases a considerable part) of every article
of necessity or luxury, consists of the cost of transporting it from
the producer to the consumer; and consequently every abatement or
saving in this cost must produce a corresponding reduction in the
price of every article transported; that is to say, of every thing
which is necessary for the subsistence of the poor, or for the
enjoyment of the rich—of every comfort, and of every luxury of
life. The benefit of this will extend, not to the consumer only, but
to the producer: by lowering the expense of transport of the
produce, whether of the soil or of the loom, a less quantity of that
produce will be spent in bringing the remainder to market, and
consequently a greater surplus will reward the labour of the
producer. The benefit of this will be felt even more by the
agriculturist than by the manufacturer; because the proportional
cost of transport of the produce of the soil is greater than that of
manufactures. If two hundred quarters of corn be necessary to raise
four hundred, and one hundred more be required to bring the four
hundred to market, then the net surplus will be one hundred. But if
by the use of steam carriages the same quantity can be brought to
market with an expenditure of fifty quarters, then the net surplus
will be increased from one hundred to one hundred and fifty
quarters; and either the profit of the farmer, or the rent of the
landlord, must be increased by the same amount.
But the agriculturist would not merely be benefited by an
increased return from the soil already under cultivation. Any
[Pg332] reduction in the cost of transporting the produce to
market would call into cultivation tracts of inferior fertility,
the returns from which would not at present repay the cost of
cultivation and transport. Thus land would become productive which
is now waste, and an effect would be produced equivalent to adding
so much fertile soil to the present extent of the country. It is
well known, that land of a given degree of fertility will yield
increased produce by the increased application of capital and
labour. By a reduction in the cost of transport, a saving will be
made which may enable the agriculturist to apply to tracts already
under cultivation the capital thus saved, and thereby increase
their actual production. Not only, therefore, would such an effect
be attended with an increased extent of cultivated land, but also
with an increased degree of cultivation in that which is already
productive.
It has been said, that in Great Britain there are above a million
of horses engaged in various ways in the transport of passengers
and goods, and that to transport each horse requires as much land
as would, upon an average, support eight men. If this quantity of
animal power were displaced by steam engines, and the means of
transport drawn from the bowels of the earth, instead of being
raised upon its surface, then, supposing the above calculation
correct, as much land would become available for the support of
human beings as would suffice for an additional population of
eight millions; or, what amounts to the same, would increase the
means of support of the present population by about one third of
the present available means. The land which now supports horses
for transport would then support men, or produce corn for food.
The objection that a quantity of land exists in the country
capable of supporting horses alone, and that such land would be
thrown out of cultivation, scarcely deserves notice here. The
existence of any considerable quantity of such land is extremely
doubtful. What is the soil which will feed a horse and not feed
oxen or sheep, or produce food for man? But even if it be admitted
that there exists in the country a small portion of such land,
that portion cannot exceed, nor indeed equal, what would be
sufficient for the number of horses [Pg333] which must after all
continue to be employed for the purposes of pleasure, and in a
variety of cases where steam must necessarily be inapplicable. It
is to be remembered, also, that the displacing of horses in one
extensive occupation, by diminishing their price must necessarily
increase the demand for them in others.
The reduction in the cost of transport of manufactured articles,
by lowering their price in the market, will stimulate their
consumption. This observation applies of course not only to home
but to foreign markets. In the latter we already in many branches
of manufactures command a monopoly. The reduced price which we
shall attain by cheapness and facility of transport will still
further extend and increase our advantages. The necessary
consequence will be, an increased demand for manufacturing
population; and this increased population again reacting on the
agricultural interests, will form an increased market for that
species of produce. So interwoven and complicated are the fibres
which form the texture of the highly civilised and artificial
community in which we live, that an effect produced on any one
point is instantly transmitted to the most remote and apparently
unconnected parts of the system.
The two advantages of increased cheapness and speed, besides
extending the amount of existing traffic, call into existence new
objects of commercial intercourse. For the same reason that the
reduced cost of transport, as we have shown, calls new soils into
cultivation, it also calls into existence new markets for
manufactured and agricultural produce. The great speed of transit
which has been proved to be practicable, must open a commerce
between distant points in various articles, the nature of which
does not permit them to be preserved so as to be fit for use
beyond a certain time. Such are, for example, many species of
vegetable and animal food, which at present are confined to
markets at a very limited distance from the grower or feeder. The
truth of this observation is manifested by the effects which have
followed the intercourse by steam on the Irish Channel. The
western towns of England have become markets for a prodigious
quantity of Irish produce, which it had been previously [Pg334]
impossible to export. If animal food be transported alive from the
grower to the consumer, the distance of the market is limited by
the power of the animal to travel, and the cost of its support on
the road. It is only particular species of cattle which bear to be
carried to market on common roads and by horse carriages. But the
peculiar nature of a railway, the magnitude and weight of the
loads which may be transported on it, and the prodigious speed
which may be attained, render the transport of cattle, of every
species, to almost any distance, both easy and cheap. In process
of time, when the railway system becomes extended, the metropolis
and populous towns will therefore become markets, not as at
present to districts within limited distances of them, but to the
whole country.
The moral and political consequences of so great a change in the
powers of transition of persons and intelligence from place to place
are not easily calculated. The concentration of mind and exertion
which a great metropolis always exhibits, will be extended in a
considerable degree to the whole realm. The same effect will be
produced as if all distances were lessened in the proportion in
which the speed and cheapness of transit are increased. Towns at
present removed some stages from the metropolis, will become its
suburbs; others, now at a day's journey, will be removed to its
immediate vicinity; business will be carried on with as much ease
between them and the metropolis, as it is now between distant points
of the metropolis itself. Let those who discard speculations like
these as wild and improbable, recur to the state of public opinion,
at no very remote period, on the subject of steam navigation. Within
the memory of persons who have not yet passed the meridian of life,
the possibility of traversing by the steam engine the channels and
seas that surround and intersect these islands, was regarded as the
dream of enthusiasts. Nautical men and men of science rejected such
speculations with equal incredulity, and with little less than scorn
for the understanding of those who could for a moment entertain
them. Yet we have witnessed steam engines traversing not these
channels and seas alone, but sweeping the face of the waters round
every coast in Europe. The [Pg335] seas which interpose between our
Asiatic dominions and Egypt, and those which separate our own shores
from our West Indian possessions, have offered an equally
ineffectual barrier to its powers, and the establishment of a
regular steam communication between the capitals of the Old and New
World has ceased to be a question of practicability, having become
merely one of commercial profit. If steam be not used as the only
means of connecting the most distant points of our planet, it is not
because it is inadequate to the accomplishment of that end, but
because the supply of the material, from which at the present moment
it derives its powers, is restricted by local and accidental
circumstances.[30]
We propose in the present chapter to lay before our readers some
account of the means whereby the effects above referred to have
been produced; of the manner and degree in which the public have
availed themselves of these means; and of the improvements of
which they seem to us to be susceptible.