Page:Popular Science Monthly Volume 41.djvu/376

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mechanical combination of gelatin and tannin or mineral salts or oil it is evident that tanned leather is not the only kind of leather. Indeed, there may be said to be three kinds, depending on the constituent elements. There are (1) tanned leather, in which the gelatin is combined with tannin or tannic acid; (2) tawed leather, in which the gelatin is combined with mineral salts; and (3) shamoyed leather, in which the gelatin is combined with oils and fatty substances. Sir Humphry Davy has distinguished between the first of these and the second and third by the statement that tanned leather is a chemical combination, its characteristic being that water will not separate its constituent elements or dissolve their connection, whereas in the case of the others it will return them to their original components. All three kinds of leather are made largely in this country. Tawed and shamoyed leather are used extensively for gloves, clothing, and domestic purposes. Some of the finer qualities have a wide use for fancy finish and ornamentation; but red tanned leather is the oldest in this country, and overtops the others by far in extent and importance, and the processes described have been those pertaining to its manufacture. And there is a wide variety in that. The heavier grades of leather, such as are used for trunks and the soles of boots and shoes, are made from the butts or the back of the hides of the buffalo, ox, and cow. The lighter grades, such as kip or upper leather, are made from the hides of young cattle older than calves and from the hides of a small breed of cattle common to India, Russia, and Africa; while all the spongy leather and morocco, or its imitation, is prepared from sheep and goat skins. These distinctions, however, are only general, but they indicate the lines along which the various branches of the industry divide. American tanners, too, have not been slow about introducing new varieties of leather. Japanned leather, used largely for fancy work and for certain styles of shoes, was first made in this country in 1818 by Seth Boyden, of Newark, N. J. In the manufacture of this the leather is first coated with a compound of linseed oil, umber, and lampblack, applied three or four times, and then is treated to a varnish made of Prussian blue and linseed oil. The leather, which had previously been stretched over frames, is afterward run into ovens heated up to 175° Fahr. Newark, too, was the original home of the enameled leather industry, David Crockett having introduced that finish. This is made much like the japanned leather, except that it is less smooth and less highly polished, the aim being to bring the grain into relief. This is used almost wholly in the coverings of carriages, and it is a branch in which America has always held the lead. Alligator skins were first tanned in Louisiana about 1855, and a considerable business has since grown up in some of the States.