the extremity of the lever, and as such, acts with greater force
on the safety-valve, than when removed to a point nearer to the
axis on which it revolves: so that should _low_ pressure steam, or
that which has a less expansive force, be required, it will only be
necessary to remove it nearer towards the axis on which it turns.
The lever and balance-ball safety valve already described, appear
but little calculated for those engines in which high pressure
steam is employed, as the engine-man, in an over anxious zeal for
the full performance of the machinery confided to his care, has
been frequently known to increase the internal pressure of a large
boiler many thousand pounds beyond the resistance to which it was
originally proved. To prevent a recurrence of those accidents, which
first drew the attention of the legislature to this important part
of the engine, it appears advisable to inclose the safety-valve in
an iron case, of which a section is annexed.
[Illustration]
The valve _B_ in this case rests upon a conical seat in the boiler
_A_, and is furnished with a series of small moveable plates
lettered _c_, which are employed to increase or diminish the entire
weight of the safety-valve, the whole being covered by the box _D_;
and as this is pierced with a number of small holes, the steam
readily escapes when the expansive force exceeds the resistance
offered by the loaded valve.
The patent _revolving wheel_ invented by Mr. Masterman, appears to
promise the best results of any rotatory engine yet invented, the
friction being much less than in any other apparatus in which steam
is employed as a prime mover. In this engine, Mr. Masterman proposes
to employ water, or the fluid metal mercury as the immediate agent,
which he effects by inclosing it in the tubular rim of a large
wheel, furnished with valves opening in one direction. This wheel,
as is shewn in the opposite diagram, is made to revolve on a hollow
axis connected with the steam boiler. The arms or spokes which
radiate from the axis are also hollow; and on the admission of
steam from the boiler, it is conducted through the arm immediately
opposite, and entering the rim of the wheel, comes in contact with,
and presses against the column of water beneath and the closed valve
above the arm. The water being previously heated to the boiling
point, no condensation ensues, but the whole weight of water, which
was previously balanced in two columns of equal height, is driven,
by the pressure of the steam, to the side opposite to that at
which the elastic vapour entered, and that side of the wheel will
necessarily preponderate. If this process be repeated, the steam
being allowed to blow through each radiating arm in succession, a
continuous rotatory motion will be produced. Should it be advisable
to employ steam of less elasticity, a condenser may be added, and
that too without materially increasing the expense.
[Illustration]
The application of steam-engines to the _propelling_ of _carriages_
on the public road, has hitherto been considered as a refinement
in mechanics, rather to be wished for than a matter of reasonable
expectation. The _locomotive_ engine was first employed for this
purpose by Messrs. Trevithick and Vivian, in 1802; and it found a
ready introduction to the mining districts where rail-roads are
general. In some cases, five, six, and even ten waggons laden with
coal are dragged up an inclined plane by means of these vehicles;
and of course impelled by a high pressure engine, from the utter
impossibility of carrying condensing water in a moveable vehicle.
An engine of four horses' power, employed by Mr. Blenkinsop,
impelled a carriage lightly loaded on a rail-road at the rate of ten
miles an hour, and when connected with thirty coal waggons, each
weighing more than three tons, its average rate was about one-third
of that pace.
When the locomotive engine was first tried, it was found difficult
to produce a sufficient degree of re-action between the wheels and
the tract road; so that the wheels turned round without propelling
the vehicle. This inconvenience was, however, obviated by Mr.
Blenkinsop, who, when he adopted the locomotive engine, took up
the common rails, on one side of the whole length of the road,
and replaced them by a series of racks, or rails, furnished with
large teeth. The impelling wheel of the engine was made to act in
these teeth, so that it continued to work in a rack which insured a
sufficient degree of re-action.
From the great weight of an ordinary _locomotive engine_ as well as
the construction of its impelling wheel, it must be evident that
the employment of this species of prime mover on the public roads
would be in the highest degree destructive; and as such that its
use will for some years to come be partially confined to the mining
districts, in which the greatest facilities are offered for its
general adoption. Indeed, we find in one neighbourhood alone, and
within a space of less than thirty square miles, more than twenty
miles of road admirably adapted for this species of conveyance; and
it is a well known fact, that there are many situations in which
iron rail-roads might be advantageously employed, in which it would
be quite impossible to open a navigable canal. In illustration
of the above fact, it may be proper to state, that a company,
with a large capital, is now forming for the express purpose of
facilitating the conveyance of goods by locomotive engines.
The mode of applying the steam-engine to the purposes of navigation
is equally simple with its employment in our manufactures.
It is generally supposed that the _steam-boat_ is of very recent
invention; on the contrary, however, the possibility of employing
steam as a prime mover in the propelling of vessels was suggested as
far back as the reign of Charles I.
In one of the old tracts preserved in the library of the London
Institution there is a very curious representation of a steam-boat,
constructed by an engineer of the name of Hulls. And this
individual, now so little known, was undoubtedly the first who
applied a steam-engine to the purpose of navigation.
To impel a vessel by this means, two paddle wheels, like those used
in an under-shot water-wheel, are connected by means of a long axis
and crank, with the working beam of the steam-engine; and if this
motion is not found sufficiently rapid, a wheel and pinion are
added, which, although it _decreases_ the effective power of the
engine, yet _increases_ the velocity of the paddle wheels.
To illustrate the great advantages possessed by the steam-engine,
even in its rudest state, over every other species of prime mover
yet enumerated, it may now be advisable to examine its effective
force when employed in the working of pumps. It has been found
that one hundred weight of coals burned in an engine on the old
construction, would raise at least _twenty thousand cubic feet_
of water twenty-four feet high; an engine with a twenty-four inch
cylinder doing the work of _seventy four horses_. An engine on Capt.
Savery's plan, constructed by Mr. Keir, has been found to raise
nearly _three millions_ of pounds of water, and Mr. Watt's engine,
upwards of _thirty millions_ of pounds the same height.
To the mining interests this valuable present of science to the
arts has been peculiarly acceptable; as a large portion of our now
most productive mineral districts must long ere this have been
abandoned, had not the steam-engine been employed as an active
auxiliary in those stupendous works. In the draining of fens and
marsh lands, this machine is in the highest degree valuable; and in
England, particularly, it might be rendered still more generally
useful. In practice it has been ascertained that an engine of
six-horse power will drain more than eight thousand acres, raising
the water six feet in height; whilst the cost of an engine for this
species of work, including the pumps, will not exceed seven hundred
pounds. This is more than ten windmills could perform, at an annual
expenditure of several hundred pounds; while, in the former case,
the outgoings will not exceed one hundred and fifty pounds per
annum. To the mariner also, the steam-engine offers advantages of
a no less important and novel nature than those which have already
been described. By its use he is enabled to traverse the waters both
against wind and tide, with nearly as much certainty, and, as the
machinery is now constructed, with much less danger, than by the
most eligible road conveyance. It too frequently, however, happens
that the faults of any new invention are unjustly magnified, while
its real advantages are seldom duly appreciated; and this axiom has
been fully verified, in the clamour so unjustly raised against the
application of the steam-engine to nautical purposes. Accidents are
now, however, but of rare occurrence; and it is more than probable,
that the great improvements which have been made in the boiler and
safety-valve will effectually secure these parts of the engine from
a recurrence of such tremendous explosions as characterised the
first introduction of steam navigation. And, lastly, the political
economist must hail with the most heartfelt gratification, the
introduction of so able and efficient a substitute for animal labour
as the steam-engine. For it has been calculated that there are at
least ten thousand of these machines at the present time at work in
Great Britain, performing a labour more than equal to that of two
hundred thousand horses, which, if fed in the ordinary way, would
require above one million acres of land for subsistence; and this is
capable of supplying the necessaries of life to more than fifteen
hundred thousand human beings.[11]
[11] _Vide_ Historical Account of the Steam-engine, by C. F.
Partington.
An ingenious foreigner, who lately visited England, has published an
estimate of the mechanical force set in action by the steam-engines
of this country.
He supposes that the _great pyramid_ of Egypt required for its
erection the labour of more than 10,000 men for 20 years:--but if
it were required again to raise the stones from the quarries, and
place them at their present height, the action of the steam-engines
of England, which are managed at most by 36,000 men, would be
sufficient to produce the same effect in 18 hours.
THE END.
LONDON:
PRINTED BY C. ROWORTH, BELL YARD,
TEMPLE BAR.
* * * * *
Transcriber's note:
Minor typographical and punctuation errors have been corrected
without note. Irregularities and inconsistencies in the text have
been retained as printed.
The cover for the eBook version of this book was created by the
transcriber and is placed in the public domain.
On pages 84 and 85 there are two items both of which are numbered
LXXXVIII. The table of contents reflects the same.
In the table of contents the following page numbers have been
changed to match the book:
Page lxxxii:
33. A Needle Alphabet--39 changed to 38
38. A Sieve Alphabet--ibid. changed to 41
Page lxxxiv:
79. A total locking of Cabinet Boxes--78 changed to 77
80. Light Pistol Barrels--ibid. changed to 78