processes. After another careful examination and cleaning, the wax mould is immersed in the first plating bath, where it receives, by chemical action, a very thin first coat of copper. Next it goes into the copper-depositing bath, which is a large tank full of a forbidding-looking fluid, wherein the mould, with many others, is suspended from rods laid across the top. A dynamo buzzes furiously at the head of this tank, and dispatches electricity through its contents, liberating therefrom minute particles of copper, and attaching them to the thin film already deposited. The entire process might be gone through in this bath, but the chemical deposit is precipitated first for the sake of quickness. Some few hours of this immersion leaves a bright shell of copper, as thick as fairly stout writing-paper, upon the mould. This latter is then carefully washed away in hot water, and there remains an exact and delicate facsimile in thin copper of the original page of type.
"The Strand Magazine" Printing Room.
But before this can be printed from it must be "backed up." Another careful examination is the preliminary to this process, which consists in pouring upon the back of the copper shell—a quantity of molten metal—principally lead—to a thickness of about a fifth of an inch, so as to make up a solid plate, with the printing surface in copper. The rough edges of this plate are trimmed off with a fine circular saw, and another machine shaves it to the proper thickness. Then a skilled workman closely scrutinizes the plate for any inequality of surface caused by heat, etc., and cleverly beats it up perfectly flat; after which another machine is called into requisition, which shaves the edges exactly square and to size; still another machine finally shaves down the plate to the mathematically exact thickness required—a machine which can take off an almost transparent shaving half the thickness of tissue paper. Then a very exact piece of mechanism bevels the edges precisely to the correct angle required to fit the cylinder whereupon the plate is to be fixed for printing. After this, being placed upon a flexible piece of steel, the plate is brought between the jaws of the shaper, which, being heated by gas and air blast, close together and bring it to the proper curve to fit upon the printing cylinder. Then the plate is finally examined for minute defects, and, if found satisfactory, is sent to do its work. Such are the processes—in addition to some other smaller and subsidiary ones not necessary to explain—through which the metal surface from which this page is printed went before even approaching the printing machine. At any stage of the operations, even the final examination, a defect not easily remedied involves the casting aside of the plate and
