156. The machine just described naturally suggests other views which seem to deserve some consideration, and, perhaps, some experiment. If a medal were placed under the tracing point of a pentagraph, an engraving tool subst.i.tuted for the pencil, and a copperplate in the place of the paper; and if, by some mechanism, the tracing point, which slides in a vertical plane, could, as it is carried over the different elevations of the medal, increase or diminish the depth of the engraved line proportionally to the actual height of the corresponding point on the medal, then an engraving would be produced, free at least from any distortion, although it might be liable to objections of a different kind. If, by any similar contrivance, instead of lines, we could make on each point of the copper a dot, varying in size or depth with the alt.i.tude of the corresponding point of the medal above its plane, than a new species of engraving would be produced: and the variety of these might again be increased, by causing the graving point to describe very small circles, of diameters, varying with the height of the point on the medal above a given plane; or by making the graving tool consist of three equidistant points, whose distance increased or diminished according to some determinate law, dependent on the elevation of the point represented above the plane of the medal. It would, perhaps, be difficult to imagine the effects of some of these kinds of engraving; but they would all possess, in common, the property of being projections, by parallel lines, of the objects represented, and the intensity of the shade of the ink would either vary according to some function of the distance of the point represented from some given plane, or it would be a little modified by the distances from the same plane of a few of the immediately contiguous points.
157. The system of shading maps by means of lines of equal alt.i.tude above the sea bears some a.n.a.logy to this mode of representing medals, and if applied to them would produce a different species of engraved resemblance. The projections on the plane of the medal, of the section of an imaginary plane, placed at successive distances above it, with the medal itself, would produce a likeness of the figure on the medal, in which all the inclined parts of it would be dark in proportion to their inclination. Other species of engraving might be conceived by subst.i.tuting, instead of the imaginary plane, an imaginary sphere or other solid, intersecting the figure in the medal.
158. Lace made by caterpillars. A most extraordinary species of manufacture, which is in a slight degree connected with copying, has been contrived by an officer of engineers residing at Munich. It consists of lace, and veils, with open patterns in them, made entirely by caterpillars. The following is the mode of proceeding adopted: he makes a paste of the leaves of the plant, which is the usual food of the species of caterpillar(4*) he employs, and spreads it thinly over a stone, or other flat substance. He then, with a camel-hair pencil dipped in olive oil, draws upon the coating of paste the pattern he wishes the insects to leave open. This stone is then placed in an inclined position, and a number of the caterpillars are placed at the bottom. A peculiar species is chosen, which spins a strong web; and the animals commencing at the bottom, eat and spin their way up to the top, carefully avoiding every part touched by the oil, but devouring all the rest of the paste. The extreme lightness of these veils, combined with some strength, is truly surprising.
One of them, measuring twenty-six and a half inches by seventeen inches, weighed only 1.51 grains; a degree of lightness which will appear more strongly by contrast with other fabrics. One square yard of the substance of which these veils are made weighs 4 1/3 grains, whilst one square yard of silk gauze weighs 137 grains, and one square yard of the finest patent net weighs 262 1/2 grains. The ladies" coloured muslin dresses, mentioned in the table subjoined, cost ten shillings per dress, and each weigh six ounces; the cotton from which they are made weighing nearly six and two-ninth ounces avoirdupois weight.
Weight of one square yard of each of the following articles(5*)
Weight of Weight cotton used Value finished of in waking per yard one square one square Description of goods measure yard yard
s. d. Troy grains Troy grains
Caterpillar veils -- 4 1/3 -- Silk gauze 3-4 wide 1 0 137 -- Finest patent net -- 262 1/2 -- Fine cambric muslin -- 551 -- 6-4ths jaconet muslin 2 0 613 670 Ladies" coloured muslin dresses 3 0 788 875 6-4ths cambric 1 2 972 1069 9-8ths calico 0 9 988 1085 1/2-yard nankeen 0 8 2240 2432
159. This enumeration, which is far from complete, of the arts in which copying is the foundation, may be terminated with an example which has long been under the eye of the reader; although few, perhaps, are aware of the number of repeated copyings of which these very pages are the subject.
1. They are copies, by printing, from stereotype plates.
2. These stereotype plates are copied, by the art of casting, from moulds formed of plaster of Paris.
3. These moulds are themselves copied by casting the plaster in a liquid state upon the moveable types set up by the compositor.
[It is here that the union of the intellectual and the mechanical departments takes place. The mysteries, however, of an author"s copying, form no part of our enquiry, although it may be fairly remarked, that, in numerous instances, the mental far eclipses the mechanical copyist.]
4. These moveable types, the obedient messengers of the most opposite thoughts, the most conflicting theories, are themselves copies by casting from moulds of copper called matrices.
5. The lower part of those matrices, bearing the impressions of the letters or characters, are copies, by punching, from steel punches on which the same characters exist in relief.
6. These steel punches are not themselves entirely exempted from the great principle of art. Many of the cavities which exist in them, such as those in the middle of the punches for the letters a, b, d, e, g, etc., are produced from other steel punches in which these parts are in relief.
We have thus traced through six successive stages of copying the mechanical art of printing from stereotype plates: the principle of copying contributing in this, as in every other department of manufacture, to the uniformity and the cheapness of the work produced.
NOTES:
1. The late Mr Lowry.
2. I posses a lithographic reprint of a page of a table, which appears, from the from of the type, to have been several years old.
3. The construction of the engraving becomes evident on examining it with a lens of sufficient power to show the continuity of the lines.
4. The Phalaena pardilla, which feeds on the Prunus padus.
5. Some of these weights and measures are calculated from a statement in the Report of the Committee of the House of Commons on Printed Cotton Goods; and the widths of the pieces there given are presumed to be the real widths, not those by which they are called in the retail shops.
Chapter 12
On the Method of Observing Manufacturies
160. Having now reviewed the mechanical principles which regulate the successful application of mechanical science to great establishments for the production of manufactured goods, it remains for us to suggest a few enquiries, and to offer a few observations, to those whom an enlightened curiosity may lead to examine the factories of this or of other countries.
The remark--that it is important to commit to writing all information as soon as possible after it is received, especially when numbers are concerned--applies to almost all enquiries. It is frequently impossible to do this at the time of visiting an establishment, although not the slightest jealousy may exist; the mere act of writing information as it is communicated orally, is a great interruption to the examination of machinery. In such cases, therefore, it is advisable to have prepared beforehand the questions to be asked, and to leave blanks for the answers, which may be quickly inserted, as, in a mult.i.tude of cases, they are merely numbers. Those who have not tried this plan will be surprised at the quant.i.ty of information which may, through its means, be acquired, even by a short examination. Each manufacture requires its own list of questions, which will be better drawn up after the first visit. The following outline, which is very generally applicable, may suffice for an ill.u.s.tration; and to save time, it may be convenient to have it printed; and to bind up, in the form of a pocket-book, a hundred copies of the skeleton forms for processes, with about twenty of the general enquiries.
GENERAL ENQUIRIES
Outlines of a description of any of the mechanical arts ought to contain information on the following points
Brief sketch of its history, particularly the date of its invention, and of its introduction into England.
Short reference to the previous states through which the material employed has pa.s.sed: the places whence it is procured: the price of a given quant.i.ty.
[The various processes must now be described successively according to the plan which will be given in (161); after which the following information should be given.]
Are various kinds of the same article made in one establishment, or at different ones, and are there differences in the processes?
To what defects are the goods liable?
What subst.i.tutes or adulterations are used?
What waste is allowed by the master?
What tests are there of the goodness of the manufactured articles?
The weight of a given quant.i.ty, or number, and a comparison with that of the raw material?
The wholesale price at the manufactory? (L s. d.) per ( )
The usual retail price? (L s. d.)
Who provide tools? Master, or men? Who repair tools? Master, or men?
What is the expense of the machinery?
What is the annual wear and tear, and what its duration?
Is there any particular trade for making it? Where?
Is it made and repaired at the manufactory?
In any manufactory visited, state the number ( ) of processes; and of the persons employed in each process; and the quant.i.ty of manufactured produce.
What quant.i.ty is made annually in Great Britain?
Is the capital invested in manufactories large or small?