Page:The Strand Magazine (Volume 4).djvu/599

 This frame swings forward and downward, and, depositing its sheets on the bench standing for their reception, returns for more. There are two such frames, depositing each simultaneously two sheets of sixteen pages each, and the machine can print 1,250 such sets of sixty-four pages in an hour. This is a bald description of the main features of the machine, which, wonderfully compact as it is, nevertheless is a mass of ingenuities. There is a deal more skill required in the printing of such illustrations as these pages contain than many are apt to imagine. For instance, there is the process of "over-laying"—an art in itself, and a difficult one. It consists in adding various thicknesses in paper to the impression cylinder, in order that the impression on each plate shall be varied—the darkest shadows of the engravings receiving the heaviest pressure, the finest lines the lightest, and all intermediate shades in proportion.

The Web Press is a wonderful construction. At one end is observed an immense roll of paper unwinding into the machine at the rate of nearly two hundred feet a minute. This paper first passes over a jet of steam, which slightly softens—does not wet—its surface; next it passes under a cylinder covered with thirty-two curved printing plates, inked by seven rollers. This prints thirty-two pages on one side. Then it travels to a reversing cylinder, and presents its other side to a second plate cylinder, provided with another batch of thirty-two plates, which print upon it, exactly behind the original pages, thirty-two more. So far, the process has occupied less than two seconds. Still the paper travels on, and passes under a small cylinder with a hidden knife, which cuts the printed paper into strips four leaves long and two leaves wide. Still on these cut sheets are carried between endless bands of tape. Various complicated and unexplainable devices give each alternate sheet a quicker progress, carrying it over that which went before; under creasing blades and circular knives the paper passes, and in the end emerges in four-folded sections of eight pages each. Eight such sections emerge at each revolution of the cylinders all accurately printed, cut, folded and registered, and ready for the binder. At the side of the machine is a brass plate with glazed holes, behind which constantly changing figures denote the number of sheets turned out. Two lads are kept busily at work seizing the folded parts and packing them in boxes on trolleys; and yet, marvellously fast as the machine does its work, it is all with a regular, deliberate movement which seems almost slow.

The Stop Cylinder Press is a smaller machine, printing, as has been seen, at a comparatively slow rate, upon one side of the