MANUFACTURE OF. The chief object in the manufacture of bank-notea Is to render forgery impossible, or at least easy of detection. This is sought to be effected by peculiarity of paper, design, and prInting„ or by a combination of these means. See PAPER. The main reliance has been on mechanical design—the writing. the emblems, and the ornaments being so combined as to render forgery difficult. The ink. too, is peeu liar (see INK), being the blackest and most indelible of inks. As a further security against forgery, a self. registeruig machiutt was contrived by 3Iessrs..Oldliam. Copper plate printing was the only printing in use for bank-notes till 1837, when a great improvement was made by Messrs. Perkins & Heath. This was the reproduction of designs by the mill and die by mechanical pressure. The pattern is engraved on a soft steel plate, which is then hardened, to transfer the pattern by pressure to a soft steel roller, on which, of course, the pattern is produced in relief; the roller or mill is then hardened, to reproduce the pattern in the plate from which the printing is to be done; and thus almost any number of plates for all common purposes can easily be produced.. No bank of England notes are issued twice.
This system of siderography continued in use for bank-note printing in the bank of England till 18.).), when electrotype-printing was introduced by Mr. Smee, with the
assistance of the mechanical officials (see ELECTROTYPING); and since that time the notes of the bank of England have been all produced by surface-printing- by the electrotype.
The usual production of notes equals a value of about .U-1,000.000 per week; it being the policy of the bank to renew the notes before the paper loses that peculiar crispness which distinguishes it from all other paper, and is a safeguard against forgery.
There are seventy or eighty kinds of bank of England notes, differing in their denom inations or values, but similar in the mode of printing. The paper is expressly naade for the purpose, by one firm only, and is remarkable for its strength, lightness, and diffi culty of imitation. The hank of Ireland notes are printed on the copperplate plan, not by surface-printing; but the use of delicate mechanism enables this to be done with great accuracy and celerity; the bank of France notes are produced from plates, the result of photogniphy, electrotyping, and steel-plate printing. Zincography and lithog raphy are employed by some banks; aud also acierage, a mode of hardening copper electrotypes with a thin surface of steel.