Page:Popular Science Monthly Volume 41.djvu/364

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350
THE POPULAR SCIENCE MONTHLY.

converting it into an almost perfect vacuum, and at the same time force liquor into it, producing a pressure of one hundred pounds to the square inch. Between the hides he placed cocoa matting, so that the free circulation of the liquor should be in no way interfered with. In the top of the tank, where it was impossible to put hides, some small blocks of wood were placed. He afterward exhausted the air in his tank, forced in the liquor, and then waited several days, but his experiment was a complete failure. On examining the contents of the tank, he found the wood thoroughly saturated with tannin, but the hides were scarcely colored. The pressure that would kyanize wood would not tan leather. Recently attempts have been made to employ

PSM V41 D364 Scouring machine.jpg
Fig. 10.—Scouring Machine.

electricity to hasten the operation, but as yet no practical and satisfactory "quick tanning" process has been found.

Few, if any, of the pioneer tanneries remain. That, however, which used to belong to Mathias Ogden and Colonel Oliver Spencer, at Elizabethtown, N. J., in 1784, was probably a good example of the original type. That consisted only of forty or fifty oblong boxes, without cover or outlet below, sunk into a bed of clay near a small stream. The boxes did duty as vats and leaches. On one side of them stood an open shed which fronted a half-dozen more boxes, the "limes" and "pools" of the beam-house, while on the other side was a circular trough, made of hewed timber, fifteen feet in diameter, in which the bark was crushed by alternate wooden and stone wheels propelled by two old horses. It was essentially a home-made plant. The wind swept through it without hindrance, and the rain and snow beat un-