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from its fearful devastations as well as

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.

Chapter 9

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.

Chapter 10

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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