The method pursued to accomplish this result is, to dissolve 32 parts of quicksilver in 500 parts of common aqua-fortis, and dilute the solution with one half or two-thirds of its bulk of water according to the strength of the acid. The skin having been laid upon a table with the hair uppermost, a stout brush, slightly moistened with the mercurial solution, is passed over the smooth surface of the hairs with strong pressure. This application must be repeated several times in succession, till every part of the fur is equally touched, and till about two-thirds of the length of the hairs are moistened, or a little more should they be rigid. In order to aid this impregnation, the skins are laid together in pairs with the hairy sides in contact, and put in this state into the stove-room, and exposed to a heat in proportion to the weakness of the mercurial solution. The drying should be rapidly effected, as otherwise the concentration of the nitrate of mercury will not produce its effect in causing the retraction and curling of the hairs. No other acid or metallic solution but the above has been found to answer the desired purpose of the hat-maker, although sulphuric acid without the quicksilver has a limited effect when the skins are treated as those above described. For other purposes, such as that of the upholsterer, hair is curled by first boiling and then baking it in an oven; or it may be spun into ropes and baked, after which it is teased asunder. Preparatory to cutting the fur from the pelt, the skins are dampened and flattened; they are thus made smooth and ready for the operation, which is performed by hand, with knives about two inches long by four wide, having a short upright handle. The skins are held upon a cutting-board, and the pelt kept moistened with water; a sheet of tin is laid upon the skin, pressed down by the left hand, whilst the knife in the right hand, being guided by the edge of the tin, is run rapidly forward and backward across the skin, gradually sliding the tin toward the tail; by this means the fur is gathered up, and kept in one fleece. The pelts are appropriated to the manufacture of gilder's cement, or will make excellent glue. Machines in the form of revolving shears, similar to those used for dressing cloth, are employed for such skins as are uneven in the pelt, and which cut the pelt from the fur in slender shreds, being quite the reverse of the hand method, which cuts the fur from the pelt. Stiffening and Water-Proofing Materials. There is reason to suppose that when hats were first invented and long subsequently, the quantity of stuff or material weighed out for a single hat was of itself considered sufficient to stand unharmed the drenchings which it was likely to encounter.