Page:The American Cyclopædia (1879) Volume XIII.djvu/60

 50 PAPER from which the air is partially exhausted by a set of air pumps, and which withdraws in part the moisture from the paper as it passes over the box. It is then carried between the cloth-covered rollers i i, by the lower one of which and the rollers jjj the wire apron re- turns to receive a fresh supply of pulp, the paper being transferred to the blanket felt &, which conveys it to the press rolls II; these are solid, and over the upper one is a thin edge bar, which removes adhering particles of fibre from the roll, and also serves to arrest the progress of the paper should it stick to the roll, thus preventing injury to the blan- ket. The rolls are adjusted in their bearings by the screw m, so as to exert greater or less pressure. The blanket then conveys the sheet to a position where it may be received by the second press rolls n n, which further compress and expel the moisture from it, and the blanket returns by way of the rollers o o o to the point whence it set out. After pass- ing the press rolls the paper is received on a second endless blanket, which carries it to the first of a series of steam-heated cylinders, 1, 2, 3, 4, 5, between which it is partially dried and conveyed between other pressure rollers, 3, and thence to a second set of drying cyl- inders, 6, 7, 8, whence, after being subjected successively to the pressing and stretching ac- tion of the rolls pp, it is delivered on to the cylinder or reel r. Registering mechanism in- dicates when a certain quantity has been de- livered on to the reel, which is then removed and a fresh one substituted. The number of drying cylinders in a machine of this class may be indefinitely increased. In some cases more than 100 are employed, the object being to allow the sizing material to become thorough- ly incorporated, and to form a product resem- bling hand-laid paper in quality." Several im- provements have been made by which the Four- drinier machine has been brought almost to perfection, and is one of the most admirable pieces of mechanism in the arts. But it is very expensive, for which reason others have been constructed for making the cheaper kinds of paper from coarse material, such as straw and cane. Of such is the cylinder machine of Dick- enson, invented in England in 1809, improved from time to time, and attaining its present form in 1847. A cylinder covered with wire cloth revolves in the chest which receives the pulp from the beating engine, and performs the office of the wire web in the Fourdrinier ma- chine. Scanlan's machine unites the principles of the cylinder and Fourdrinier machines, and makes a double-web paper, the opposite sides of which may be of different colors. Harris's is a two-cylinder machine, which makes a two- web paper. Mr. James Harper of New Haven, Conn., has also patented a combination of the cylinder and Fourdrinier, for which he claims several advantages over other machines. Some of the latest English machines include a drying apparatus consisting of numerous large cylin- ders of wire net, each having a revolving fan in the inside. The wet web of paper passes around all the cylinders in turn, deprived of some of its moisture by each fan, so that when it leaves the last cylinder it is thoroughly dry. It is said that the paper is harder and stronger dried in this way than by steam-heated cylin- ders. Not many years ago paper received its finished surface by being placed between cop- per plates and then passed several times be- tween powerful iron rollers or calenders. But this method has been superseded by what are known as sheet super-calenders, in which the paper is passed between rollers, one of which is made of iron and the other of compressed paper surrounding an iron shaft. The paper used in the preparation of the cylinders is of the strongest kind, usually manila, and when placed on the shaft is subjected to immense hydraulic pressure. The varieties of paper are numerous. They may be classed in general as writing (including draw ing), printing, and wrap- ping ; and besides these are the filtering and blotting papers, which differ from the other kinds in an admixture of woollen rags, by which the product is rendered absorbent. Cartridge paper is a thick variety of white paper used for making cartridges. Bank-note paper is a very strong, flexible, and thin paper, made of the best linen rags ; and tissue paper is a thin trans- parent paper used for tracing drawings, mani- fold writing, and many other purposes. The distinctions of the varieties of writing paper are based on the paper being wove or laid, and on the shades of color and degree of finish. The cream laid and cream wove are of a slight- ly yellowish white, and are now regarded as the choicest varieties. Papers of a bluish tint are prepared by mixing ultramarine with the pulp. A very small amount of ultramarine counteracts the natural yellow color, and pro- duces the nearest approach to white. The light buff color is produced by oxide of iron of a low degree of oxidation, and paper of this shade has been recommended as more grateful to the eye than the glaring surface of the white varie- ties. The trade names of the different sorts of paper designate the different sizes furnished from the mills. The smaller sheets of letter and note paper are prepared from the com- mercial sheets by the stationers. The smallest sheets furnished by the mills, termed pot pa- per, measure 12 by 15 inches ; foolscap, the next size, 13$- by 17 ; post, 15 J by 18| ; copy, 16 by 20; large post, 16^ by 20|; medium post, 18 by 23; sheet and a third foolscap, 13J by 23 ; sheet and a half foolscap, 13 J by 24 ; double foolscap, 17 by 27 ; double pot, 25 by 30 ; double post, 19 by 30|- ; double crown, 20 by 30 ; double medium, 24 by 38 ; demy, 15 by 20; ditto printing, 17| by 22; medium, 17 by 22 ; ditto printing, 18 by 23 ; royal, 19 by 24 ; ditto printing, 20 by 25 ; superroyal, 19 by 27; ditto printing, 21 by 27; imperial, 22 by 30 ; elephant, 23 by 28 ; atlas, 26 by 34; columbier, 23 by 34 ; double elephant, 26| by