LEATHER consists essentially of the skins of animals chemically altered by the vegetable principle called tannin, or tannic acid (q.v.), so as to arrest that proneness to decompose which is characteristic of soft animal substances. Its invention reaches beyond the dawn of history, and was probably among the earliest germs of civilization; for as the skins of animals would naturally be the first articles of clothing. any means of preserving them more effectually than by drying would be highly prized, The discovery that bark had this effect was doubtless the result of accident. The prin ciple of its action was unknown up the present century; and the same unvarying method had been employed from the earliest times until the last few years, when the invention of new processes has much facilitated the manufacture.
The skins of all animals used in the production of leather consist chiefly of gela tine, a substance which easily enters into chemical combination with the tannic acid found in the bark of most kinds of of trees, and forms what may be termed an insoluble tanno-gelatin. This is the whole theory of tanning, or converting the skins of animals Formerly, oak-bark was supposed to be the only tanning material of any value; but lately very numerous additions have been made to this branch of economic botany.
In addition to the process of tanning in making leather, there are other modes, one of which is taming, another dressing in oil. The following are the skins which form the staple of our leather manufacture: ox, cow, calf and kip, buffalo, horse, sheep, lamb, goat, kid, deer, dog, seal, and hog.
The term pelt is applied to all skins before they arc converted into leather. When simply made into leather in the state we find in shoe-soles, it is called "rough leather;" •but if, in addition, it is submitted to the process called currying, which will be hereafter described, it is termed "dressed leather. • The following trade-terms are in general usei•hides or crop-hides, butts and backs, bends, offal, andskins. The complete hide when rounded, with the cheeks, shanks, and
belly-pieces, etc., pared off, is called a butt; the pieces cut off constitute the offal; and skins are all the lighter forms of leather, such as sheep, goat, deer, etc.
Besides the ox and cow hides furnished by the home-trade, vast numbers arc imported from Montevideo, Buenos Ayres, Russia, and northern Germany, and a very consider 'able number of dry buffalo-hides are brought from the East Indies. The quantity of all sorts imported into Great Britain in 1875. amounted to 1,027,953 cwt.; and the entire value of the hides and leather (uumannfactured) imported in 1875 was as much as -.E4,852,030. These returns, however, comprise a considerable number of horse-hides, which are also sent from South America. Calf-skins and kip-skins (that is, the skins of beasts older than calves, but not full-grown oxen) are, when tanned, used chiefly for the upper-leather of boots and shoes.
Sheep and lamb skins are imported (in the wool) in large quantities from Australia and the cape. of Good Hope; and tanned, from our East Indian possessions. The latter, with the cape skins, are used for book-binding, furniture, gloves, etc. Lamb-skins are imported also from Italy. Sicily, and Spain, and tawed and dyed for making gloves, in imitation of kid. A great portion of all sorts of lambs and sheep are tawed and used •for masons' aprons, sewing harness, plaster-skins, tying up bottles, lining shoes, and other jobbing and inferior purposes.
Deer-skins are dressed by the oil process, and form a great portion of the so-called shamoy leather, which derives its name from the chamois of the Alps, from the skin of which it was formerly made.
Dog-skins are tanned or tawed for gloves, and for thin shoes and boots. &al-skins are manufaCture into the so-called "patent leather," by varnishing their upper surface. the manufacture of this kind of leather has of late become of great importance to the London, Edinburgh, and Newcastle tanners.