PRINTING PRESS 



4826 



PRISM 



runners of steel. While the bed moves back- 

 ward from the cylinder, the latter is held by a 

 cam, while automatic fingers seize the printed 

 sheet and carry it over a second but smaller 

 cylinder, from which it glides to the *' flyer" and 

 is deposited on the table. Highly-perfected 

 single-cylinder presses are used for fine book 

 printing. 



A further advance was the perfecting press, 

 which had two cylinders and two type beds, 

 and printed both sides of a sheet, but with two 

 distinct operations. The sheet on such a press 



POWER PRINTING PRESS 

 A standard machine for newspaper printing in 

 small cities. 



is carried over several rollers from one cylin- 

 der to the other. The perfecting machines 

 have been supplanted by the so-called two- 

 revolution presses. These have only one cylin- 

 der, which revolves twice for each sheet printed. 

 The use of this press means that the sheet must 

 be run through twice if it is to be printed 

 on both sides, but the modern two-revolution 

 presses have been perfected so that it is 

 cheaper to use them than the old two-cylinder 

 presses. A good press of this type can be 

 purchased for $2,500 to $3,500, depending on 

 size and special attachments. 



Daily Newspaper Presses. To the ordinary 

 visitor in the pressroom of a great daily news- 

 paper, where the huge machines turn out a 

 whole edition of a paper in an hour or less, it is 

 surprising to note that apparently no one is 

 paying the slightest attention to the printing. 

 The machines keep up a continuous roar; en- 

 gineers, oil can in hand, stroll around, oiling 

 here, examining there, much as engineers on 

 board ship would do. Yet from the bowels of 

 the huge machine they tend is pouring a 

 stream of miles and miles of news and illustra- 

 tions vitally affecting the knowledge and wel- 

 fare of the world. The human brain controls 

 the mighty machinery of a newspaper; human 

 hands are rarely needed. 



One of the most remarkable of modern 

 presses is known as Hoe's Double Octuple 



Rotary Machine, printing from eight reels of 

 paper, each containing a roll five miles in 

 length and double the width of the ordinary 

 newspaper. This press prints, cuts, folds and 

 delivers in quires, at the rate of 06,000 copies 

 an hour, a complete newspaper of thirty-two 

 pages. The working of the machinery is so 

 rapid that when the press is running at full 

 speed the paper is unwound at the rate of ten 

 miles an hour. Such a machine in octuple form 

 costs about $90,000, measures fifty-four feet 

 in length, nineteen in height and twelve in 

 breadth. When all the paper on the reels is 

 unwound and printed, a new set of eight reels 

 can be adjusted ready for printing in three 

 minutes. These presses may also be adapted 

 for color printing (see PRINTING, subhead Color 

 Printing. 



The principle on which all rotary presses are 

 built is the same. The basic idea is that the 

 type, in the form of stereotype plates, is fas- 

 tened to the large cylinder, while smaller cylin- 

 ders carry the paper. Ingenious combinations 

 of cylinders are arranged so that both sides of 

 the paper are printed at once; the paper is fed 

 into the machine from the continuous roll or 

 web about 25,000 feet long, and the printed web 

 is cut into the proper lengths and folded into 

 newspaper form by a series of knives and roll- 

 ers. On these large cylinder presses only 

 stereotype plates are used. The octuple rotary 

 press described above is really a combination 

 of eight separate presses in a single frame; any 

 of them or any combination of them may be 

 run alone. W.F.Z. 



Consult DeVinne's Invention of Printing; Hoe's 

 Short History of the Printing Press. 



Related Subjects. See list at end of the arti- 

 cle PRINTING. 



PRISM, 'priz'm. A solid which has two equal 

 and parallel polygons for its bases and paral- 

 lelograms for its lateral surfaces is a prism. 

 A prism whose lateral faces are perpendicular 

 to the base is a right prism; the lateral faces 

 are rectangles. All of the prisms shown in Fig. 

 1 are right prisms. Other prisms are called 

 oblique; their lateral surfaces are parallelo- 

 grams but not rectangles. Prisms are named 

 from their bases; as triangular, a, rectangular, 

 b, pentagonal, c, etc. (see in Fig. 1). The alti- 

 tude of a prism is the perpendicular distance 

 between the bases. 



The lateral surface is made up of a number 

 of parallelograms, a number equal to the num- 

 ber of the sides of the base. Therefore the 

 area oj the lateral surface is found by multi- 



