WASHING.--A washing engine consists of an oval tub about four feet high. It is divided longitudinally by a partition or “mid-feather,” with a passage left at either end for the circulation of the stock. On one side is located a large roll, having a continuous parallel series of knives horizontally inserted in its surface. The floor of the engine slopes gently to a point under the roll, where a bed plate is set. Behind the roll is a raised partition or dam, over which the stock is thrown as it passes between the beater roll and the bed plate. This is known as the “back-fall,” and assists in the circulation. The roll may be raised or lowered over the bed plate, and by this means the breaking of the stock is regulated. Affixed to the tub are one or more washing cylinders, so arranged that they may be lowered into the stock. These are constructed in such a way that during the process of washing the water passes through their wire-covered surfaces and is drained into the hollow axle of the roll by an interior arrangement, called buckets. The axle, being open at one end, permits the wash water to escape. At first the engine is partly filled with water, then the rags are gradually thrown in until the tub is full. The revolving roll keeps the mass in circulation, while the rags are broken and shredded as they pass beneath it. A continuous stream of fresh water runs into the tub, and in running out through the revolving washer drums carries off the dirt, but the fibers themselves can not pass through the wire coverings, so remain until cleansed. Necessarily the water used must be free from sediment or mineral impurities, such as iron, otherwise it would fill the stock with specks. Therefore, a filter plant is usually maintained. BLEACHING.--After the washing has been completed the drums are raised clear of the stock and bleaching liquor is introduced. This is an important step, and if not carefully managed may impair the stock. For instance, if bleaching is carried on at too high a temperature, the white color obtained will not be permanent, and discoloration will occur after the paper is made. Much of the paper, which at first displays a brilliant white color, will afterward take on a yellowish tinge, especially if it is exposed to light. A comparison between the century-old hand-made papers and modern “fine writings,” makes the old papers appear a “natural” shade, but place both for a few hours in the sunlight and often the modern paper will fade, whereas the old sun-bleached papers remain unaltered. The high artificial bleaching does not insure permanent results. After the bleach liquor has been thoroughly mixed in, the stock is discharged into drainers and allowed to stand for a week or more, until no traces of chlorine remain. In this state the pulp is known as “half-stock.” The treatment of hemp is so similar to that of rags that a description here of the process is superfluous. WOOD-PULPS.