LEATHER, Manufacture and Uses of. Of all the ancient industries that of the manu facture of leather is one of the most interesting on account of the convertibility of an easily de composed sdbstance into one which resists pu trefaction. The manufacture of leather is as old as history itself. In China the manufacture and use of leather was known before the Christian era, and in Egypt leather has been found in mausoleums of the ancients, showing us that nations in the remote ages of the past were practised in the art and left slight traces of their high civilization to be admired to-day. The Persians and Babylonians passed the art over to the Greeks and Romans and so down through the different mediaeval nations to tis. The American Indians were also well versed in the art of making leather, although their method of tanning was entirely different to that of the ancient races, yet the fact remains that they also discovered a way of treating the skins of animals in such a way as to prevent the putre faction of animal tissues.
Composition of Hides and Skins.— The skin of an animal consists of three layers— the outerskin, middle and underslcin. The outer skin which cannot be tanned is removed with the hair, leaving the middle skin or grain and the underskin or flesh. The upper part of the skin in which the coat of hair, wool or fur is rooted is a thin layer termed the epidermis or cuticle. Next beneath this is the much thicker corium or true skin, and next to this the under skin.
The epidermis does not combine with tannin or other substances to produce leather. It is therefore useless to the tanner and is removed at the same time as the hair. The portion of the skin thereby exposed is technically termed the side. The corium or true skin is the actual leather skin and is made up of inter laced bundles of gelatinous fibres. It is more or less filled with fluid matter that serves to renew the cuticle and maintain the skin in a pliant and moist condition. In the tanning process these matters are removed, reducing the weight of the skin considerably, and there remains nothing but the fibrous portion to be acted on by the tanning materials. The quality
of leather which can be produced from a skin depends upon the thickness, flexibility and strength of the corium, which exceeds the com bined thickness of all the other layers of the skin. The under skin consists of a loose con nective tissue, in which the sweat and fat glands, the blood vessels and the muscular fibres are embedded. The side upon which the con nective tissue of the under side is located is technically designated as the °flesh) side. The under skin or flesh is composed of interlaced fibres which give the strength to the tanned stock and is therefore a most important factor for the tanner while the middle skin gives the fine smooth appearance to the finished product. The skin, being organic, is composed of carbon, oxygen, hydrogen, nitrogen and sulphur, which go to make up the middle and under skin.
Source and Uses of Hides and Skins.— Most of the leather in common use is made from the hides and skins of domestic animals, those of cattle being by far the most important, followed by goatskins, sheepskins, horsehides, pigskins and in a small measure dogskins. Many skins of wild animals, principally those of the kangaroo, deer, peccary, alligator, seal, wal rus and buffalo are in fairly general use. Cattle hides are used chiefly for shoe upper and sole leathers, harness, belting, upholstery, bag and case leathers, and to some degree in bookbind ing. Goatskins are used for shoes, gloves, bookbinding and fancy leathers. Sheepskins are used for shoe linings, gloves and the greater part of the fancy leathers. Horsehides are used for shoes and utility gloves. Pigskins are used for the inner parts of shoes, utility gloves, bookbinding, fancy leathers and saddle seats. Dogskins find limited application in glove leathers. Kangaroo is used for fine shoe leathers. Deerskins, known as buckskins, are used for both shoes and gloves, peccary for utility gloves, alligator for bag and fancy leathers, seal for bags, bookbinding and fancy leather& walrus for jewelers' polishing wheels and buffalo for heavy soles.