LEA

LEA

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The fuppofed improvement in the procefs oftanning pradHfed and actually propofed by M.Seguin may here be fhortly mentioned. Thisingenious artift wifhing to abridge the enormoustime employed in common tanning (and confe-quent expence; and confidering the tan as nearlythe only aCtive principle in this procefs, adoptedthe plan of ufing folutions of tan, inftead of themixture of bark and ooze ufually employed, andof feveral and known degrees of ftrength inwhich the fkin might be rapidly pafied from theweakeft to the ftrongell by a more regulated gra-dation than is ufually done. For this purpofehe had a feries of vats containing the oak-bark, and began by pouring water on one ofthem, and after a fhort time drawing it offclear through a hole at the bottom. This firftooze was then poured on the bark of the fecondvat, and drawn off as before, by which it becamefenfibly ftronger of tan. This liquor again wasufed to the third vat, and again to a fourth, ac-cording to the number, till it became quitefaturated with tan. In the mean time frefhwater was poured on the bark of the differentvats in the fame order, which produced a fecondooze ftill very flrong but inferior to the firft:and thus three or four or more different oozeswere obtained, all differing in ftrength, andwhich was the tanning liquor employed. Thefkins then being previoufly prepared in the wayalready defcribed, were paffed fucceffivelythrough the different oozes, beginning with theweakeft and afcending to the itrongeft till theywere compleatly tanned, which was known bythe difappearance of the white line in the middleof the fkin when cut through.

It appears beyond a doubt that the procefs oftanning is moft materially fhortened by thismethod of M. Seguin, and that very perfectleather is produced, but though now known forleveral years it does not appe'ar to be adopted toany extent in this country, where leather is ma-nufactured in vaft quantities both for homeconfumption and for exportation to many partsof Europe , in which Englifh leather is in thehigheft repute. From the way in which theoozes are made, according to M. Seguin, theymuft of neceffity contain much more tan in pro-portion to the extradl and other vegetable matterthan where the bark itfelf is buffered to remain infubftance along with the ooze and fkin for manymonths, as the tan is much the moft folubleof .all the fubftances that are to be extract-ed by water, fo that bark may readily be cxhauft-ed of tan, long before the extract, refill, gallicacid, and ether materials are got out. It is faid

that the leather prepared in this new method islefs durable and more brittle than in the old way.

The only real improvement of late adoptedin this part of the procefs is to ufe fome of theoozes warm by which the Ikin is fooner pene-trated with the ooze, and a faving of time madeof fome confequence.

Dr. Macbride propofes lime-water to be ufedinftead of common water for the extradiion ofthe tan from the oak-bark, but this feems to bemifehievous, as the only affignable effedt of thelime would be to contradt a firm union with aportion of the gallic acid and the tan, the refultof which would be an infoluble calcareous fub-ftance utterly unfit for any purpofes of tanning.

Of Tawing, Leather-drejftng and dyeing, andother procejfes.

The drefling and preparing of the fkins oflambs, ftieep, goats, and other thin hides, thoughin many particulars clofely refembling themethod ufed with the thick cow and ox hides,forms ufually a totally diftindt branch of bufi-nefs, and is one in which a good deal of pradticalfkill and nicety of manipulation is required tofucceed perfectly. The procefles are veryvarious according to the article required, andthis branch of the manufacture fupplies theimmenfe demand of white and dyed leather forgloves, the (fo called) morocco leather of differ-ent colours and qualities for coach linings,book-binding, pocket-books, and tliin leather foran infinite number of fmaller purpofes. Ofthefe the white leather alone is not tanned butfinifhed by the procefs of tawing, but thecoloured leather receives always a tanning (ge-nerally by fumach) independent of the otherdyeing materials. The previous preparation ofeach, or that in which the fkin is thoroughlycleanfed and reduced to the ftate of fimplemembrane in which it is called pelt, is effentiallythe fame whether for tawing or dyeing. It isthus performed at the beft manufactories atBermondfey, near London , a place long cele-brated for all branches of the leather bufinefs.

By far the greater number of the lkins areimported: if lambs they are thus prepared ,the fkins are firft foaked for a time in water, tocleanfe them from any loofe dirt and blood, andput upon the beam commonly ufed for the pur-pofe, which is a half cylinder of wood coveredwith flrong leather, and scraped on the fldhfide with the femicircular blunt knife with twohandles ufed in this operation. They are thenhung up in confiderable numbers in a fmall cloferoom heated by flues, where they remain to