On the Economy of Machinery and Manufactures, Charles Babbage [classic romance novels .TXT] 📗
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barrel; and if the barrel is loose upon the axis, the
paddle-wheel makes the axis only revolve, and the boat remains in
its place: but the moment the axis is attached to its surrounding
barrel, this begins to turn, and winding up the rope, the boat is
gradually drawn up against the stream; and may be employed as a
kind of tug-boat for vessels which have occasion to ascend the
rapid. When the tug-boat reaches the summit the barrel is
released from the axis, and friction being applied to moderate
its velocity, the boat is allowed to descend.
54. Clocks occupy a very high place amongst instruments by
means of which human time is economized: and their multiplication
in conspicuous places in large towns is attended with many
advantages. Their position, nevertheless, in London, is often
very ill chosen; and the usual place, halfway up on a high
steeple, in the midst of narrow streets, in a crowded city, is
very unfavourable, unless the church happen to stand out from the
houses which form the street. The most eligible situation for a
clock is, that it should project considerably into the street at
some elevation, with a dial-plate on each side, like that which
belonged to the old church of St Dunstan, in Fleet Street, so
that passengers in both directions would have their attention
directed to the hour.
55. A similar remark applies, with much greater force, to the
present defective mode of informing the public of the position of
the receiving houses for the twopenny and general post. In the
lowest corner of the window of some attractive shop is found a
small slit, with a brass plate indicating its important office so
obscurely that it seems to be an object rather to prevent its
being conspicuous. No striking sign assists the anxious enquirer,
who, as the moments rapidly pass which precede the hour of
closing, torments the passenger with his enquiries for the
nearest post-office. He reaches it, perhaps, just as it is
closed; and must then either hasten to a distant part of the town
in order to procure the admission of his letters or give up the
idea of forwarding them by that post; and thus, if they are
foreign letters, he may lose, perhaps, a week or a fortnight by
waiting for the next packet.
The inconvenience in this and in some other cases, is of
perpetual and everyday occurrence; and though, in the greater
part of the individual cases, it may be of trifling moment, the
sum of all these produces an amount, which it is always worthy of
the government of a large and active population to attend to. The
remedy is simple and obvious: it would only be necessary, at each
letter-box, to have a light frame of iron projecting from the
house over the pavement, and carrying the letters G. P., or T.
P., or any other distinctive sign. All private signs are at
present very properly prohibited from projecting into the street:
the passenger, therefore, would at once know where to direct his
attention, in order to discover a post-office; and those
letter-boxes which occurred in the great thoroughfares could not
fail to be generally known.
Exerting Forces Too Great for Human Power, and Executing
Operations Too Delicate for Human Touch
56. It requires some skill and a considerable apparatus to
enable many men to exert their whole force at a given point; and
when this number amounts to hundreds or to thousands, additional
difficulties present themselves. If ten thousand men were hired
to act simultaneously, it would be exceedingly difficult to
discover whether each exerted his whole force, and consequently,
to be assured that each man did the duty for which he was paid.
And if still larger bodies of men or animals were necessary, not
only would the difficulty of directing them become greater, but
the expense would increase from the necessity of transporting
food for their subsistence.
The difficulty of enabling a large number of men to exert
their force at the same instant of time has been almost obviated
by the use of sound. The whistle of the boatswain performs this
service on board ships; and in removing, by manual force, the
vast mass of granite, weighing above 1,400 tons, on which the
equestrian figure of Peter the Great is placed at St Petersburgh,
a drummer was always stationed on its summit to give the signal
for the united efforts of the workmen.
An ancient Egyptian drawing was discovered a few years since,
by Champollion, in which a multitude of men appeared harnessed to
a huge block of stone, on the top of which stood a single
individual with his hands raised above his head, apparently in
the act of clapping them, for the purpose of insuring the
exertion of their combined force at the same moment of time.
57. In mines, it is sometimes necessary to raise or lower
great weights by capstans requiring the force of more than one
hundred men. These work upon the surface; but the directions must
be communicated from below, perhaps from the depth of two hundred
fathoms. This communication, however, is accomplished with ease
and certainty by signals: the usual apparatus is a kind of
clapper placed on the surface close to the capstan, so that every
man may hear, and put in motion from below by a rope passing up
the shaft.
At Wheal Friendship mine in Cornwall, a different contrivance
is employed: there is in that mine an inclined plane, passing
underground about twothirds of a mile in length. Signals are
communicated by a continuous rod of metal, which being struck
below, the blow is distinctly heard on the surface.
58. In all our larger manufactories numerous instances occur
of the application of the power of steam to overcome resistances
which it would require far greater expense to surmount by means
of animal labour. The twisting of the largest cables, the
rolling, hammering, and cutting large masses of iron, the
draining of our mines, all require enormous exertions of physical
force continued for considerable periods of time. Other means are
had recourse to when the force required is great, and the space
through which it is to act is small. The hydraulic press of
Bramah can, by the exertion of one man, produce a pressure of
1,500 atmospheres; and with such an instrument a hollow cylinder
of wrought iron three inches thick has been burst. In rivetting
together the iron plates, out of which steamengine boilers are
made, it is necessary to produce as close a joint as possible.
This is accomplished by using the rivets red-hot: while they are
in that state the two plates of iron are rivetted together, and
the contraction which the rivet undergoes in cooling draws them
together with a force which is only limited by the tenacity of
the metal of which the rivet itself is made.
59. It is not alone in the greater operations of the engineer
or the manufacturer, that those vast powers which man has called
into action, in availing himself of the agency of steam, are
fully developed. Wherever the individual operation demanding
little force for its own performance is to be multiplied in
almost endless repetition, commensurate power is required. It is
the same ‘giant arm’ which twists ‘the largest cable’, that spins
from the cotton plant an ‘almost gossamer thread’. Obedient to
the hand which called into action its resistless powers, it
contends with the ocean and the storm, and rides triumphant
through dangers and difficulties unattempted by the older modes
of navigation. It is the same engine that, in its more regulated
action, weaves the canvas it may one day supersede, or, with
almost fairy fingers, entwines the meshes of the most delicate
fabric that adorns the female form.(1*)
60. The Fifth Report of the Select Committee of the House of
Commons on the Holyhead Roads furnishes ample proof of the great
superiority of steam vessels. The following extracts are taken
from the evidence of Captain Rogers, the commander of one of the
packets:
Question. Are you not perfectly satisfied, from the experience
you have had, that the steam vessel you command is capable of
performing what no sailing vessel can do?
Answer. Yes.
Question. During your passage from Gravesend to the Downs, could
any square-rigged vessel, from a first-rate down to a sloop of
war, have performed the voyage you did in the time you did it in
the steamboat?
Answer. No: it was impossible. In the Downs we passed several
Indiamen, and 150 sail there that could not move down the
channel: and at the back of Dungeness we passed 120 more.
Question. At the time you performed that voyage, with the weather
you have described, from the Downs to Milford, if that weather
had continued twelve months, would any square-rigged vessel have
performed it?
Answer. They would have been a long time about it: probably,
would have been weeks instead of days. A sailing vessel would not
have beat up to Milford, as we did, in twelve months.
61. The process of printing on the silver paper, which is
necessary for banknotes, is attended with some inconvenience,
from the necessity of damping the paper previously to taking the
impression. It was difficult to do this uniformly and in the old
process of dipping a parcel of several sheets together into a
vessel of water, the outside sheets becoming much more wet than
the others, were very apt to be torn. A method has been adopted
at the Bank of Ireland which obviates this inconvenience. The
whole quantity of paper to be damped is placed in a close vessel
from which the air is exhausted; water is then admitted, and
every leaf is completely wetted; the paper is then removed to a
press, and all the superfluous moisture is squeezed out.
62. The operation of pulverizing solid substances and of
separating the powders of various degrees of fineness, is common
in the arts: and as the best graduated sifting fails in effecting
this separation with sufficient delicacy, recourse is had to
suspension in a fluid medium. The substance when reduced by
grinding to the finest powder is agitated in water which is then
drawn off: the coarsest portion of the suspended matter first
subsides, and that which requires the longest time to fall down
is the finest. In this manner even emery powder, a substance of
great density, is separated into the various degrees of fineness
which are required. Flints, after being burned and ground, are
suspended in water, in order to mix them intimately with clay,
which is also suspended in the same fluid for the formation of
porcelain. The water is then in part evaporated by heat, and the
plastic compound, out of which our most beautiful porcelain is
formed, remains. It is a curious fact, and one which requires
further examination than it has yet received, that, if this
mixture be suffered to remain long at rest before it is worked
up, it becomes useless; for it is then found that the silex,
which at first was uniformly mixed, becomes aggregated together
in small lumps. This parallel to the formation of flints in the
chalk strata deserves attention.(2*)
63. The slowness with which powders subside, depends partly
on the specific gravity of the substance, and partly on the
magnitude of the particles themselves. Bodies, in falling through
a resisting medium, after a certain time acquire a uniform
velocity, which is called their terminal velocity, with which
they continue to descend: when the particles are very small, and
the medium dense, as water, this terminal velocity is soon
arrived at. Some of the finer powders even of emery require
several hours to subside through a few feet of water,
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