Page:Popular Science Monthly Volume 56.djvu/319

Rh completely purify it, but it also renders it possible to mold it into convenient forms and to compress it so as to greatly increase its efficiency in use. For this purpose the pulp is suspended in water



and pumped to a molding press, where, under a hydraulic pressure of one hundred pounds to the square inch, it is molded into cylinders or prisms about three inches in diameter and five inches and a half high, and these are compressed to two inches in height by a final press exerting a pressure of about sixty-eight hundred pounds to the square inch. As this is regarded as a somewhat hazardous operation, the press is surrounded by a mantlet woven from stout rope to protect the workmen from flying pieces of metal in case of an accident. The operation is analogous to that employed in powder-making, where the gunpowder has been pressed in a great variety of forms and into single grains weighing several pounds apiece.

Even under the enormous pressure of the final press the compressed gun cotton still retains from twelve to sixteen per cent of water, and in this form it is quite safe to store and handle. When dry it is very combustible and burns readily