Many modified varieties of the cylinder machine have been introduced; the most im portant of them is the gripper. In this machine the types are laid on a traveling table like that described above; the cylinder which gives the pressure is reduced to 12 or 18 incites in diameter, the drums are dispensed with, and the tapes are replaced by a contriv ance called a gripper. This consists of a series of brass grips like fingers arranged along, and fixed to the cylinder; these seize the sheet at the proper moment, and retain it till it is delivered printed. The single gripper is supplied with points for registering. In the double or perfecting variety, the sheet is delivered from the first cylinder into the grippers of the second. There are many varieties of gripper machines; the most popu lar arc the Wharfda]e, a single, and the double gripper, named after its maker, M. Mari noni of Paris. They produce good work, and are well adapted for general purposes.
Non-registering machines for rapid printing are of various kinds, according to the degree of speed which is demanded. In those first introduced, the principle was that of pressure by a cylinder on a form of types laid upon a table, which was passed beneath it by a forward and retrograde motion; the inking being effected as in the above described perfecting machines. Having received one side by means. the sheets were after ward printed on the second side; such second impression containing the news up till the latest hour of going to press. This species of single cylinder printing-machine was well adapted for newspapers of which only a few thousand copies were wanted; and for this purpose it is still in use, particularly in provincial towns in Great Britain. As presses of this sort, however, do not usually yield more than 4,000 or 5,000 impressions per hour, they are quite unfitted for printing newspapers haying a circulation of 20,000 copies and upward, the whole of which must be promptly produced by a certain hour every morning. The liberation of newspapers from the obligatory penny-stamp in 1855 caused so great an increase of circulation that Bone of the ordinary processes, including that just re ferred to, was at all adequate for the work required. Recourse had to be made to an entirely new method of printing, the invention of which is due to Richard M. Hoe of New York.
Hoe's process consisted in placing the types (for which stereotype plates were after ward substituted) on a horizontal cylinder revolving on its axis, against which the sheets were pressed by exterior and smaller cylinders. The pages of type were arranged in
segments of a circle, each segment forming a frame that could be fixed on the cylinder. These frames were technically called turtles. By the ingenious contrivance of making the brass rules that separate the columns of a beveled or wedge shape, the thinner edge being- toward the surface of the turtle, the form of type was susceptible of being tight ened up and made firm. The forms occupied only a portion of the main cylinder, the remainder affording space for time inking apparatus. The smaller surrounding cylinders for effecting the pressure were arranged in a frame-work, in connection with slopes, by which the sheets were fed in blank, and came out printed on one side. The size of the main cylinder, the number of exterior cylinders, and the rate of speed determined the number of impressions printed per hour. Such was the method of working Hoe's rotary machines, which, as wanted, were made with 2, 4, 6, 8, or 10 subsidiary cylinders. The first introduced into Europe (with the exception of one made for newspaper, La Adria, in 1848) was one with six cylinders for printing Lloyd's Weekly Newspaper in London iu 1857. Some idea of the process of working may be obtained from Fig. 3, representing a rotary machine with six feeders. Such a machine with its six feeders, each laying in sheets at the rate of 2,000 per hour, could deliver 12,000 impressions in the hour; and those with 8 and 10 cylinders in proportion.
About the time that the Hoe machines came commonly into use, another great advance was made in the art of rapid printing. In 1859 a long series of experiments ended in the successful substitution of curved stereotype plates for pages of movable type. Besides the risk and wear involved in working pages of type in circular chases, the new method relieves the types from all direct printing-work, so that the fount instead of two years may last twenty.
The Hoe machine, however, with all its advantages, retained the inconvenience of printing only one side at a time, and the multiplication of the feeding cylinders intro. duced too many complications. These difficulties have been entirely overcome by a new machine, the " Walter," contrived and perfected between 1863 and 1868 by the manager of the Times printing establishment. which prints both sides by one operation from a continuous roll of paper. The "Walter" machine is represented iu Fig. 4.