On the Economy of Machinery and Manufactures

by Charles Babbage

116. Square glass bottles. The round forms which are usually given to vessels of glass are readily produced by the expansion of the air with which they are blown. It is, however, necessary in many cases to make bottles of a square form, and each capable of holding exactly the same quantity of fluid. It is also frequently desirable to have imprinted on them the name of the maker of the medicine or other liquid they are destined to contain. A mould of iron, or of copper, is provided of the intended size, on the inside of which are engraved the names required. This mould, which is used in a hot state, opens into two parts, to allow the insertion of the round, unfinished bottle, which is placed in it in a very soft state before it is removed from the end of the iron tube with which it was blown. The mould is now closed, and the glass is forced against its sides, by blowing strongly into the bottle.

117. Wooden snuff boxes. Snuff boxes ornamented with devices, in imitation of carved work or of rose engine turning, are sold at a price which proves that they are only imitations. The wood, or horn, out of which they are formed, is softened by long boiling in water, and whilst in this state it is forced into moulds of iron, or steel, on which are cut the requisite patterns, where it remains exposed to great pressure until it is dry.

118. Horn knife handles and umbrella handles. The property which horn possesses of becoming soft by the action of water and of heat, fits it for many useful purposes. It is pressed into moulds, and becomes embossed with figures in relief, adapted to the objects to which it is to be applied. If curved, it may be straightened; or if straight, it may be bent into any forms which ornament or utility may require; and by the use of the mould these forms may be multiplied in endless variety. The commoner sorts of knives, the crooked handles for umbrellas, and a multitude of other articles to which horn is applied, attest the cheapness which the art of copying gives to the things formed of this material.

119. Moulding tortoise-shell. The same principle is applied to things formed out of the shell of the turtle, or the land tortoise. From the greatly superior price of the raw material, this principle of copying is, however, more rarely employed upon it; and the few carvings which are demanded, are usually performed by hand.

120. Tobacco-pipe making. This simple art is almost entirely one of copying. The moulds are formed of iron, in two parts, each embracing one half of the stem; the line of junction of these parts may generally be observed running lengthwise from one end of the pipe to the other. The hole passing to the bowl is formed by thrusting a long wire through the clay before it is enclosed in the mould. Some of the moulds have figures, or names, sunk in the inside, which give a corresponding figure in relief upon the finished pipe.

121. Embossing upon calico. Calicoes of one colour, but embossed all over with raised patterns, though not much worn in this country, are in great demand in several foreign markets. This appearance is produced by passing them between rollers, on one of which is figured in intaglio the pattern to be transferred to the calico. The substance of the cloth is pressed very forcibly into the cavities thus formed, and retains its pattern after considerable use. The watered appearance in the cover of the volume in the reader's hands is produced in a similar manner. A cylinder of gun-metal, on which the design of the watering is previously cut, is pressed by screws against another cylinder, formed out of pieces of brown paper which have been strongly compressed together and accurately turned. The two cylinders are made to revolve rapidly, the paper one being slightly damped, and, after a few minutes, it takes an impression from the upper or metal one. The glazed calico is now passed between the rollers, its glossy surface being in contact with the metal cylinder, which is kept hot by a heated iron enclosed within it. Calicoes are sometimes watered by placing two pieces on each other in such a position that the longitudinal threads of the one are at right angles to those of the other, and compressing them in this state between flat rollers. The threads of the one piece produce indentations in those of the other, but they are not so deep as when produced by the former method.

122. Embossing upon leather. This art of copying from patterns previously engraved on steel rollers is in most respects similar to the preceding. The leather is forced into the cavities, and the parts which are not opposite to any cavity are powerfully condensed between the rollers.

123. Swaging. This is an art of copying practised by the smith. In order to fashion his iron and steel into the various forms demanded by his customers, he has small blocks of steel into which are sunk cavities of different shapes; these are called swages, and are generally in pairs. Thus if he wants a round bolt, terminating in a cylindrical head of larger diameter, and having one or more projecting rims, he uses a corresponding swaging tool; and having heated the end of his iron rod, and thickened it by striking the end in the direction of the axis (which is technically called upsetting), he places its head upon one part of the lage; and whilst an assistant holds the other part on the top of the hot iron, he strikes it several times with his hammer, occasionally turning the head one quarter round. The heated iron is thus forced by the blows to assume the form of the mould into which it is impressed.

124. Engraving by pressure. This is one of the most beautiful examples of the art of copying carried to an almost unlimited extent; and the delicacy with which it can be executed, and the precision with which the finest traces of the graving tool can be transferred from steel to copper, or even from hard steel to soft steel, is most unexpected. We are indebted to Mr Perkins for most of the contrivances which have brought this art at once almost to perfection. An engraving is first made upon soft steel, which is hardened by a peculiar process without in the least injuring its delicacy. A cylinder of soft steel, pressed with great force against the hardened steel engraving, is now made to roll very slowly backward and forward over it, thus receiving the design, but in relief. The cylinder is in its turn hardened without injury., and if it be slowly rolled to and fro with strong pressure on successive plates of copper, it will imprint on a thousand of them a perfect facsimile of the original steel engraving from which it was made. Thus the number of copies producible from the same design may be multiplied a thousand-fold. But even this is very far short of the limits to which the process may be extended. The hardened steel roller, bearing the design upon it in relief may be employed to make a few of its first impressions upon plates of soft steel, and these being hardened become the representatives of the original engraving, and may in their turn be made the parents of other rollers, each generating copperplates like their prototype. The possible extent to which facsimiles of one original engraving may thus be multiplied, almost confounds the imagination, and appears to be for all practical purposes unlimited.

This beautiful art was first proposed by Mr Perkins for the purpose of rendering the forgery of bank notes a matter of great difficulty; and there are two principles which peculiarly adapt it to that object: first, the perfect identity of all the impressions, so that any variation in the minutest line would at once cause detection; secondly, that the original plates may be formed by the united labours of several artists most eminent in their respective departments; for as only one original of each design is necessary, the expense, even of the most elaborate engraving, will be trifling, compared with the multitude of copies produced from it.