WOOD PULP. The invention of forming paper pulp from wood has revolutionized the paper trade in the United States, especially in printing paper. It now constitutes a vast indus try. The poplars—quaking ash is the best— and others, soft without being gummy, are espe cially useful. In Europe, the industry is a large one, and as in this country, increasing yearly. In Europe much soft pine is used. There are three methods of reducing the wood in pulp. In two the initial processes are the same. Cut transversely by machinery into small pieces, after having been barked—or it would be more correct to say thin slices—the wood is boiled in water under high pressure. In one process, known as the " soda process," it is afterwards treated like wise under great heat, with caustic soda, which leaves it a pure cellulose mass. This mass is subsequently washed and passed through an ordinary " breaker," then over a machine with an endless sieve or felt, from which it issues as a roll, or what is known in commerce as wood pulp. In the other process, known as the "acid process," the wood is treated with sulphuric acid instead of caustic soda. In color, the " wood pulp" is light gray, and when dry it is of great tenacity. By the soda process, two to four and one-half tons of wood are required for one ton of pulp. Considerable controversy exists as to
the merits of the two processes, but the respec tive pulps sell at about the same price, and, ex cept by very experienced paper-makers, it is said, could not be distinguished. The other process is known as the " mechanical process," the wood being simply ground—practically in water—into minute fibers and partially dried in the usual manner. The logs are brought in a "lade" up to the saws and cut into pieces varying from a foot to two feet in length. These pieces are in turn barked and split by machinery, and passed on to have the knots bored out and the pith removed. Upright grinding-stones are kept revolving in water or, at all events, are kept drenched with water, and against these stones the wood is held by a hydraulic piston, which can be adjusted so as to produce long or short fiber. Open pipes carry the water with the fiber in suspension— the mass resembling a cloudy stream—onto the knotters or sieves, which check the passage of unground chips, while the strained material is carried onto an ordinary paper-making machine with an endless web or fine sieve, whence it issues in the shape of large sheets, with 50 per cent. of the water squeezed out of them.