screws regulates the thickness of the side, and by sectional tubes or rings serves as a friction-roller. When it is desired to split
Fig. 18.—Hoyt Spent Tan Furnace. The above illustration is from the Hoyt furnace at Wilcox, Pa. which consists of two pairs of ovens connected with three horizontal boilers. The portion in the cut consists of a section through one of the ovens and one of the boilers, showing the oven, ash pit, grate, holes for feeding the tan into the oven, the boilers, and the door to sweep out the flues.
whole hides, a still more complicated machine is employed. This is known as the belt-knife splitting machine, and was invented in 1854 by Joseph F. Flanders and Jere. A. Marden, of Newburyport, Mass. The knife in this machine consists of an endless band of steel, which revolves at a high speed, with its cutting edges close to the sides of a pair of rollers. Through these latter the leather is fed and pressed closely against the knife. The lower roller is made up of a series of rings which are capable of yielding so as to accommodate themselves to the varying thickness of the hides. The thickness of the splits is determined by a small hand-screw, by which the upper roller is raised or depressed as the case may require. The knife itself in its course of revolution comes in contact with an emery-wheel and thus is kept keen. These machines present a blade varying between fifty-seven and seventy-two inches in length, and by them an ordinary cow-hide can be split into three or four distinct parts with the utmost precision.