The pile was removed to a screw press, wherein as much water as possible was squeezed out of the paper. Cellulose fibers have a strong affinity for water, however, and it is said that under any pressure which such a pile could withstand, without becoming crushed and gruelly, the paper would retain water equal to one-half its weight. Hence, the last vestiges of moisture, excepting of course that amount normally retained by air-dried paper, had to be removed by evaporation. In the old days, this was accomplished by hanging the sheets over poles to dry. After that, if the paper required sizing, the sheets were dipped one by one into a pot of animal size, then dried once more. Lastly they were finished to the desired surface by being placed between smooth plates and pressed. FIBER CHARACTERISTICS. A few moments’ consideration of the changes which the fibers undergo from their condition of isolation as they exist mixed in the vat, to their status as components of a sheet of paper, will help to make clear much that seems obscure about the behavior of a sheet of finished paper, as well as to explain the reason for the different processes executed on the paper-machine. The fiber is a hollow, collapsed tube, the ends bruised and frayed by the treatment in the beating and refining engines. Absorptive in nature to a marked degree, it swells with the water it takes up and is limp and flaccid. As the mold is raised horizontally out of the vat in the process of forming sheets, all the fibers which had been suspended in the water which passed through the meshes of the mold are caught like so many fish in a net, and lie spread in a limp, impressionable mass over the surface of the mold until they are transferred by the “coucher man” to the felt. Little alteration can take place in the general position of the fibers after they have been “couched,” consequently the formation of the sheet is the most important stage of the process. As the water is pressed out, each fiber contracts to some extent, and, from a consistency like gruel, the formed sheet passes to a more stable state, wherein it can be gently handled without disintegrating. [Illustration: FOURDRINIER MACHINES, CRANE & CO. A good view of the surface-sizing vat is obtained in the machine on the right hand. The paper is being slit just before its introduction into the vat.] As the drying proceeds there is a marked shrinkage in the dimensions of the sheet, caused by the shrinking of each individual fiber, until the fibers are thoroughly set, enmeshed one with the other.