Around the fixed frame at different but exact points above the large drum, there are eight revolving tympan cylinders, or which feed in the sheets to the revolving drum, and against the surface of which the form, as it revolves, im presses the paper. The attendants push in the sheets, one by one, to the tym pans, in each of which is an open section, with fingers worked by a cam, which are open when they come round to receive a sheet, then close upon it, wrapping the said sheet around the smooth surface of the tympan ; at this very period, the typo on the large drum has come round, and is acting on the paper. When the type has printed the sheet, the fingers spoken of open like the human hand and the printed sheet is whipped off the tympan and carried away back to the end of the press, there to be taken off and folded neatly down by a vibratory flyer, four of which are placed one above another, (one for each tympan,) at each side of the press. The two outside edges of each sheet of paper are held against a smooth narrow strap on the tympan on each side. Above each tympan cylinder it will be observed there are a number of small pulleys, with straps running around them, extending the whole length of each tympan, and running on its sur face. The straps of these small pulleys run away back over a like set of pulleys, above the flyers. Whenever the type forms its impression on the sheet, the fingers spoken of let the paper free, and then these small straps whip up the sheet and carry it along, as on a flying railroad, to be folded by the flyer. After the form makes its impression on the paper which is wrapped around the tym pan, it comes in contact with the two small ink-rollers, which ink the surface of the type, and fit it to print the sheet on the next tympan, and so on continu ally. These small inking rollers have their journals fitted on springs, so as to allow them to be pushed up or down by the type, and then to be forced against the distributing surface, to take up the ink for their next performance.
In this one press, it may be said, "their are eight combined," that is, in respect to its effective power. One, two, three, or more tympan cylinders can be detached, and the rest left free to work. This makes it very conveni ent, for it requires but a moment's labor to set the press so as to work with any number less than the eight attendants.
Although this machine is so large, strictly speaking it is exceedingly simple in its operaiton, and it works with a smoothness and regularity that commands admiration. The building of this great press for the New-York Sun was com menced in 1819, and it was completed in 1851.
In the construction of this press Messrs. Hoe & Co. state that there are employed no less than six thousand bolts and screws, one thousand two hundred wheels, two hundred and two wooden rollers, four hundred pulleys, four hundred tape guides, besides an amazing amount of cogged wheel con nections, arms, braces, and other con nections. There are also required to give motion to various parts of the machine, HO less than five hundred yards of belting. It can print 20,000 copies in one hour. It has been in successful operation print ing the New-York Sun for the past six months, and it operates with astonishing precision.
The manufactory of Messrs. Hoe & Co., N. Y., is the most extensive one of its kind in this country. In it are made
several varieties of presses, both cylinder and platen ; a description of those man ufactured in that establishment to a great extent comprehends the notice of those presses most in use. Among the cylin der presses are, 1. The Type Revolving Fast Printing Machine, the mechanism of which is as follows : A horizontal cylinder of about four and a half feet in diameter, is mounted on a shaft, with appropriate bearings ; about one-tburth 01 the circumference of this cylinder constitutes the bed of the press, which is adapted to receive the form of types—the remainder is used as a cylindrical distributing table. The diameter of the cylinder is less than that of the farm of types, in order that the distributing portion of it may pass the impression cylinders without touching. The ink is contained in a fountain placed beneath the large cylinder, from which it is taken by a duster roller and trans ferred, by a vibrating distributing roller, to the cylindrical distributing table ; the fountain roller receives a slow and con tinuous rotary motion, to carry up the ink from the fountain.
The large cylinder being put in mo tion, the form of types thereon is, in succession, carried to four or more cor responding horizontal impression cylin ders, arranged at proper distances around it, to give the impression to four or more sheets, one introduced by each impres sion cylinder. The fly and feed-b oards of two of the impression cylinders are similar to those on the well-known dou ble cylinder press ; on the other two, the sheet is fed in below and thrown out above. The sheets are taken directly from the feed-board, by iron fingers attached to each impression cylinder. Between each two of the im pression cylinders there arc two inking rollers, which vibrate on the distributing surface while taking a supply of ink, and at the proper time are caused to rise, by a cam, so as to pass over the form, when they again fall to the distributing surface. Each page is locked up upon a detached segment of the large cylinder, called by the compositors a " turtle," and this constitutes the bed and chase. The column-rules run parallel with the shafts of the cylinder, and are conse quently straight while the head, ad and dash-rules are in the form of segments of a circle. A cross section of the column-rules would pre sent the form of a wedge, with the small end pointing to the centre of the cylinder, so as to bind the types near the top ; for, the types being parallel, in stead of radiating from the centre, it is obvious that if the column-rules were also parallel, they must stand apart at the top, no matter how tight they were pressed together at the base ; but with these wedge-shaped column rules, which arc held down to the bed or "turtle" by tongues, projecting at intervals along their length, and sliding in rebated grooves cut crosswise in the face of the bed, the space in the grooves, between the col umn-rules, being filled with sliding blocks of metal, accurately fitted, the outer surface level. with the surface of the bed, the ends next the column-rules being cut away underneath to receive a projection on the sides of the tongues, and screws at the end and side of each page to lock them together, the types are as secure on this as they can be on the old flat bed.