rate as the surface of the drum. They are, in other words, so connected, that they can only move together and at the same speed. The printing is effected in this way. The drum and cylinders are set in motion; and in moving, the types on the surface of the drum become inked, and the eight cylinders are supplied with paper. The drum in passing round presses the type successively against each of the eight cylinders, and thus in turning round once eight sheets are printed.

Let us now explain how the type is inked eight times whilst the drum is turning round once; and how the eight cylinders are supplied with paper. Beside each of the eight paper cylinders are placed a set of inking rollers; near these are placed two ductor rollers. These ductor rollers receive a coating of ink from reservoirs placed above them. An inking table is attached to the great drum, and as it passes, receives a coating of ink from each of these rollers. The inking table next meets the rollers which ink the type, and transfers the coating of ink to them. Next, the types pass along, and encountering the inking rollers, receive the ink in turn. Next, the types encounter the paper on the cylinders, and thus they are printed. In a single revolution of the great central drum, therefore, the inking table receives a supply twice successively from the ductor rollers, delivers over that supply eight times successively to the inking rollers,

which in their turn deliver it eight times successively to the faces of the type, from which it is conveyed finally to the eight sheets of paper upon the eight cylinders.

It remains to be explained how the eight cylinders are supplied with paper. Over each of them is erected a sloping desk, upon which a stock of unprinted paper is placed. An attendant standing by the side of the desk, pushes the paper, sheet by sheet, towards an apparatus known as the fingers of the drum. These fingers seizing the sheet by the edge, draw it straight down in a line with the drum, just as we draw down a window blind, and when it has descended sufficiently, a self-acting frame moves it sideways instead of downwards, and it is carried between tapes towards the printing-cylinder. As it passes round the printing-cylinder the types have been moved round sufficiently to print it. The sheet is then carried back, still sideways, by the same tapes on the other side of the frame, until it arrives at another desk upon which it is received by another attendant. It may be stated here that one of the difficulties which Mr. Applegath had to encounter in the construction of this vast piece of machinery was so to regulate the self-acting machine that the impression of the type should always be made in the centre of the page, and so that the print on one side of the paper might come exactly back to back with the print on the

other side. This is generally accomplished, though an occasional deviation will occur. The type fixed on the drum moves round at the rate of five feet per second, and the paper to be printed is moved in contact with it, of course, at exactly the same rate. Now, if by any error in the placing of a sheet of paper, or in its motion, it should arrive at the printing cylinder so little as 1-60th part of a second too soon or too late, that is, before or after the type has arrived opposite the printing cylinder, each column will be printed one 1-60th part of five feet out of its place, that is to say, one inch. In that case the edge of the print on one side of the sheet would be an inch nearer to the edge of the paper than the print on the other side. Such an incident rarely happens, but when it does the sheet is spoiled. Still the waste from the slipping of the sheets is considerably greater in the horizontal machine, than in the present vertical machine.

The movement of the vertical machine is round and round again without interruption. The Times machine prints no less than eight sheets at every revolution. The moment that one sheet is drawn into the machine, space is left for another, which the attendant immediately supplies, and in this manner the machine receives from him two sheets in every five seconds. As the same thing takes place at each of the eight cylinders, 16, sheets are

drawn into the machine and printed every five seconds. The Times machine prints between 10,000 and 11,000 sheets an hour with ease; but if the men who place the sheets are very expert, it will work off from 12,000 to 13,000 an hour. Indeed, the rapidity of the machine is limited only by the power of the men to feed it with paper. If still greater speed were required, it might be obtained without changing the principle of the machine. It would only be necessary to increase the size of the great central drum carrying the type, so that a larger number of printing cylinders might be placed round it. If, for instance, a machine with eight cylinders will print 10,000 sheets an hour, a machine with sixteen cylinders would print 20,000 an hour.

The benefit arising from the machine printing is incalculable. The machine has relieved men of hard toil which was often hurtful to health. Sheets of a greatly increased size can now be printed. The cost of printing has been greatly reduced, and the employment of printers greatly increased. The result has been an extraordinary diffusion of all kinds of knowledge, and a great advance in the civilization of the world.

The Printing Office.

We have now described the rise and progress of Printing, the manufacture of type, the

construction of the press and machine, and, in short, the apparatus by which the art is practised. We proceed to describe the printing of a book; and in doing this we shall conduct our readers through a printing-office* whilst the work is going on.

We commence with the author of the book. The author having fixed on the size of the page and the type in which his book shall be printed, the printer usually makes an estimate of the number of pages which the manuscript will occupy, and the cost of the printing. This is done with great accuracy by a process called "casting-off the copy." The words in two or three pages of the manuscript are counted, and the average number contained in one page is made the standard of the whole of the manuscript. Thus, if

Page 1 contains 97 words

n e average

is, then, 100.

number of words in each page

If each page of the manu

script contains 100 words, 50 pages of manuscript will contain 5,000 words. The next