MANUFACTURES.

25

Engraving copper plates.by pressure .-This is one of the most beautiful instances of see, i.the Art of Copying carried to an almost unlimited extent; and the delicacy with which t—it can be execute , an the precision with which the finest traces of the graving tool impressionscan 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 havebrought this Art at once almost to perfection. An engraving is first made upon softsteel, which is hardened by a peculiar process without in the least injuring its deli-cacy. . A cylinder of soft steel, pressed with great force against the hardened steelengraving, is now made to roll slowly backward and forward over it. The soft steelcylinder receives the design, but it is in relief. This is i„ its turn hardened withoutinjury; and if it be slowly rolled to and fro with strong pressure on successive platesof copper, it will imprint on a thousand of them a perfect fac-simile of the original steelengraving from which it resulted. Thus is the number of copies producible from thesame design multiplied a thousand fold.

But even this is very far short of the limits to which this process may beextended. The ardened steel roller may be employed to make a few of its firstimpressions upon p ates of soft steel, and these being hardened may in their turnbecome the parents of other rollers, each generating copper plates like the original.

The possible extent o which fac-similes of an original engraving may thus be multi-plied almost con ounds the imagination, and appears to be, for all practical purposes,unlimited. There are two principles which peculiarly fit this Art for rendering the for-gery of Bank-notes, to prevent which Mr. Perkins proposed it, a matter of great diffi-culty. The first is t e perfect identity of every impression with every other, so thatany variation m the minutest li ne would at once cause detection. The other principleis, that the plates rom which all the impressions are deduced may be formed by theunited labours of artists most eminent in their several departments, all working atthe same time; and that, as only one original of each design is necessary, the expense,however great, will be trifling, compared with the immense multitude of copies pro-duced from it. r r

Gold and silver moulding. Many of the mouldings used by jewellers consist of thinslips of metal, which have received their form by passing between steel rollers, thustaking a succession of Copies of the devices engraved upon them.

Ornamental papers.—-Sheets of paper coloured or covered with gold or silver leaf, Embossingand embossed with various patterns, are used for covering books, and for many orna- papeT"** 1mental purposes. The figures upon these are produced by the same process, thatof passing the sheets of paper between engraved rollers.

OF COPYING BY STAMPING.

This principle of Copying is extensively employed in the Arts. It is generally exe-cuted by means of large presses worked with a screw and heavy fly-wheel. The

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