It will be kept in mind that there are four things necessary in printing,--the page of type, or the stereotype or electrotype plate, to print from; the paper, to receive the impression; the ink, to exhibit this impression; and lastly the printing-press to press the paper upon the inked plate. In our walk over the printing-house, let us step into the Press-room where book-work is done. On the left, in the foreground, is a large cylinder press used for printing newspapers; there is another in the distance, and between can be seen parts of a number of hand-presses. On the right are great “platen” presses, that are kept in motion by steam-power. They are used for the nice execution of book-work, and print only from six hundred to one thousand impressions an hour. Let us watch the operation of one of these platen presses on the right. The paper, having been dampened and pressed, is laid on an inclined table on the press, from which the “feeder,” as the girl by the second press in the picture is called, takes one sheet at a time, and places it upon an opposite inclined table, where it is clutched by the iron fingers of the press, and carried into the machine. If we stood near the press, we should see the bed of type adjusted with the face up, and long rollers brought quickly back and forth, evenly smearing it with ink. The iron fingers before mentioned as having grasped the edge of the sheet, lay it on the inked bed of type, where it comes under the platen, when the bed is raised up against the paper; the bed falling again, the force of the machine slides out the paper over rollers upon a light frame, which throws it over upon a board where the pile of sheets collects. This process prints the paper on one side only; turning the paper, the sheets are put through the press the second time, and the printing is completed. [Illustration: PRESS ROOM.] But this and other departments of the art here pursued, give employment to hundreds of operatives of both sexes, throwing off annually many millions of impressions. Here rumbles the thunder of the modern steam-propelled printing-presses. What a clangor is made by the simultaneous revolutions of so much complicated machinery! Broad leather straps, rapidly revolving in every direction, cause you to start back, fearful lest you be caught in their toils. And yet how docile, how easily managed, how orderly, how almost human in intelligence,--and with what lightning swiftness the monster steam-presses throw off their work, so that the eye can scarcely follow the successively printed sheets!