On the Economy of Machinery and Manufactures - Charles Babbage (interesting books to read in english .TXT) 📗
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from its connection with geological theories, that it becomes
important to possess an instrument which shall, if possible,
indicate the direction of the shock, as well as its intensity.
An observation made a few years since at Odessa, after an
earthquake which happened during the night, suggests a simple
instrument by which the direction of the shock may be determined.
A glass vase, partly filled with water, stood on the table of
a room in a house at Odessa; and, from the coldness of the glass,
the inner part of the vessel above the water was coated with dew.
Several very perceptible shocks of an earthquake happened between
three and four o’clock in the morning; and when the observer got
up, he remarked that the dew was brushed off at two opposite
sides of the glass by a wave which the earthquake had caused in
the water. The line joining the two highest points of this wave
was, of course, that in which the shock travelled. This
circumstance, which was accidentally noticed by an engineer at
Odessa,(4*) suggests the plan of keeping, in countries subject to
earthquakes, glass vessels partly filled with treacle, or some
unctuous fluid, so that when any lateral motion is communicated
to them from the earth, the adhesion of the liquid to the glass
shall enable the observer, after some interval of time, to
determine the direction of the shock.
In order to obtain some measure of the vertical oscillation
of the earth, a weight might be attached to a spiral spring, or a
pendulum might be sustained in a horizontal position, and a
sliding index be moved by either of them, so that the extreme
deviations should be indicated by it. This, however, would not
give even the comparative measure accurately, because a
difference in the velocity of the rising or falling of the
earth’s surface would affect the instrument.
NOTES:
1. Transactions of the Society of Arts, 1819, p. 116.
2. The contrivance is due to Mr Hencky, of High Holborn, in whose
establishment it is in constant use.
3. About seven or eight years since, without being aware of Sir
David Brewster’s proposal. I adapted a barometer, as a pendulum,
to the works of a common eight day clock: it remained in my
library for several months, but I have mislaid the observations
which were made.
4. Memoires de l’Academie des Sciences de Petersburgh, 6e serie,
tom. i. p. 4.
Economy of the Materials Employed
77. The precision with which all operations by machinery are
executed, and the exact similarity of the articles thus made,
produce a degree of economy in the consumption of the raw
material which is, in some cases, of great importance. The
earliest mode of cutting the trunk of a tree into planks, was by
the use of the hatchet or the adze. It might, perhaps, be first
split into three or four portions, and then each portion was
reduced to a uniform surface by those instruments. With such
means the quantity of plank produced would probably not equal the
quantity of the raw material wasted by the process: and, if the
planks were thin, would certainly fall far short of it. An
improved tool, completely reverses the case: in converting a tree
into thick planks, the saw causes a waste of a very small
fractional part; and even in reducing it to planks of only an
inch in thickness, does not waste more than an eighth part of the
raw material. When the thickness of the plank is still further
reduced, as is the case in cutting wood for veneering, the
quantity of material destroyed again begins to bear a
considerable proportion to that which is used; and hence circular
saws, having a very thin blade, have been employed for such
purposes. In order to economize still further the more valuable
woods, Mr Brunel contrived a machine which, by a system of
blades, cut off the veneer in a continuous shaving, thus
rendering the whole of the piece of timber available.
78. The rapid improvements which have taken place in the
printing press during the last twenty years, afford another
instance of saving in the materials consumed, which has been well
ascertained by measurement, and is interesting from its
connection with literature. In the old method of inking type, by
large hemispherical balls stuffed and covered with leather, the
printer, after taking a small portion of ink from the ink-block,
was continually rolling the balls in various directions against
each other, in order that a thin layer of ink might be uniformly
spread over their surface. This he again transferred to the type
by a kind of rolling action. In such a process, even admitting
considerable skill in the operator, it could not fail to happen
that a large quantity of ink should get near the edges of the
balls, which, not being transferred to the type, became hard and
useless, and was taken off in the form of a thick black crust.
Another inconvenience also arose—the quantity of ink spread on
the block not being regulated by measure, and the number and
direction of the transits of the inking-balls over each other
depending on the will of the operator, and being consequently
irregular, it was impossible to place on the type a uniform layer
of ink, of the quantity exactly sufficient for the impression.
The introduction of cylindrical rollers of an elastic substance,
formed by the mixture of glue and treacle, superseded the
inking-balls, and produced considerable saving in the consumption
of ink: but the most perfect economy was only to be produced by
mechanism. When printing-presses, moved by the power of steam,
were introduced, the action of these rollers was found to be well
adapted to their performance; and a reservoir of ink was formed,
from which a roller regularly abstracted a small quantity at each
impression. From three to five other rollers spread this portion
uniformly over a slab (by most ingenious contrivances varied in
almost each kind of press), and another travelling roller, having
fed itself on the slab, passed and repassed over the type just
before it gave the impression to the paper.
In order to shew that this plan of inking puts the proper
quantity of ink upon the type, we must prove, first—that the
quantity is not too little: this would soon have been discovered
from the complaints of the public and the booksellers; and,
secondly that it is not too great. This latter point was
satisfactorily established by an experiment. A few hours after
one side of a sheet of paper has been printed upon, the ink is
sufficiently dry to allow it to receive the impression upon the
other; and, as considerable pressure is made use of, the tympan
on which the side first printed is laid, is guarded from soiling
it by a sheet of paper called the set-off sheet. This paper
receives, in succession, every sheet of the work to be printed,
acquiring from them more or less of the ink, according to their
dryness, or the quantity upon them. It was necessary in the
former process, after about one hundred impressions, to change
this set-off sheet, which then became too much soiled for further
use. In the new method of printing by machinery, no such sheet is
used, but a blanket is employed as its substitute; this does not
require changing above once in five thousand impressions, and
instances have occurred of its remaining sufficiently clean for
twenty thousand. Here, then, is a proof that the quantity of
superfluous ink put upon the paper in machine-printing is so
small, that, if multiplied by five thousand, and in some
instances even by twenty thousand, it is only sufficient to
render useless a single piece of clean cloth.(1*) The following
were the results of an accurate experiment upon the effect of the
process just described, made at one of the largest printing
establishments in the metropolis.(2*) Two hundred reams of paper
were printed off, the old method of inking with balls being
employed; two hundred reams of the same paper, and for the same
book, were then printed off in the presses which inked their own
type. The consumption of ink by the machine was to that by the
balls as four to nine, or rather less than one-half.
NOTES:
1. In the very best kind of printing, it is necessary, in the old
method, to change the set-off sheet once in twelve times. In
printing the same kind of work by machinery, the blanket is
changed once in 2000.
2. This experiment was made at the establishment of Mr Clowes, in
Stamford Street.
Of the Identity of the Work When It is of the Same Kind, and its
Accuracy when of Different Kinds
79. Nothing is more remarkable, and yet less unexpected, than
the perfect identity of things manufactured by the same tool. If
the top of a circular box is to be made to fit over the lower
part, it may be done in the lathe by gradually advancing the tool
of the sliding-rest; the proper degree of tightness between the
box and its lid being found by trial. After this adjustment, if a
thousand boxes are made, no additional care is required; the tool
is always carried up to the stop, and each box will be equally
adapted to every lid. The same identity pervades all the arts of
printing; the impressions from the same block, or the same
copperplate, have a similarity which no labour could produce by
hand. The minutest traces are transferred to all the impressions,
and no omission can arise from the inattention or unskilfulness
of the operator. The steel punch, with which the cardwadding for
a fowling-piece is cut, if it once perform its office with
accuracy, constantly reproduces the same exact circle.
80. The accuracy with which machinery executes its work is,
perhaps, one of its most important advantages: it may, however,
be contended, that a considerable portion of this advantage may
be resolved into saving of time; for it generally happens, that
any improvement in tools increases the quantity of work done in a
given time. Without tools, that is, by the mere efforts of the
human hand, there are, undoubtedly, multitudes of things which it
would be impossible to make. Add to the human hand the rudest
cutting instrument, and its powers are enlarged: the fabrication
of many things then becomes easy, and that of others possible
with great labour. Add the saw to the knife or the hatchet, and
other works become possible, and a new course of difficult
operations is brought into view, whilst many of the former are
rendered easy. This observation is applicable even to the most
perfect tools or machines. It would be possible for a very
skilful workman, with files and polishing substances, to form a
cylinder out of a piece of steel; but the time which this would
require would be so considerable, and the number of failures
would probably be so great, that for all practical purposes such
a mode of producing a steel cylinder might be said to be
impossible. The same process by the aid of the lathe and the
sliding-rest is the everyday employment of hundreds of workmen.
81. Of all the operations of mechanical art, that of turning
is the most perfect. If two surfaces are worked against each
other, whatever may have been their figure at the commencement,
there exists a tendency in them both to become portions of
spheres. Either of them may become convex, and the other concave,
with various degrees of curvature. A plane surface is the line of
separation between convexity and concavity, and is most difficult
to hit; it is more easy to make a good
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