On the Economy of Machinery and Manufactures by Charles Babbage (novels to read in english .TXT) 📖

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.