Leather manufacture may be broadly divided into two stages: "tanning," in which the raw hide is converted into the imputrescible and more or less flexible material known as "leather"; and "currying," in which this leather is further manipulated, and treated with fatty matters, to soften and render it more waterproof, and to improve its appearance. Glove-kid, and certain other leathers, however, are not tanned at all, but "tawed," or prepared with a mixture in which alum and salt are the most active ingredients; chamois, "shammy," or "wash" leather, is produced by fulling with oil alone, and many leathers can scarcely be said to be curried, although more or less oil is used in the final processes of "finishing" or "dressing." The first subject to be treated of in this work will be the operation of tanning, properly so called, taking for example the tannage of sole- and belting-leather. This demands thorough explanation, in both its practical and theoretical aspects, not only because it is one of the most important branches of the trade, but because the principles involved are those which equally underlie all other tanning methods. The next to be dealt with will be the modifications of the process which are necessary in tanning the more flexible leathers used for boot-uppers, hose-pipes, and saddlery purposes; then the currying of these leathers; and finally, the manufacture of moroccos, Russian, and japanned leathers, calf- and glove-kid, &c. CHAPTER I. ANATOMICAL STRUCTURE OF HIDE. Before speaking of actual processes of manufacture, it is necessary to devote some attention to the structure and chemical constitution of hide or skin, which forms the raw material. Although a great variety of skins are employed in tanning, they are all constituted on the same general type, and an anatomical description of the hide of the ox will apply almost equally to those of the calf, sheep, and goat; but from differences in thickness and closeness of texture, their practical uses differ widely. Fig. 1 shows a section of ox-hide, cut parallel with the hair, magnified about 50 diam.: _a_, epithelial layer or _epidermis_, consisting of horny layer above, and _rete malpighi_ below; _b_, _pars papillaris_, and _c_, _pars reticularis_ of _corium_, _derma_, or true skin; _d_, hairs; _e_, sebaceous or fat-glands; _f_, sudoriferous or sweat-glands; _g_, opening of ducts of sweat-glands; _h_, _erectores pili_ muscles, for erecting the hair.