138 Methd of "Tanning Leather hi Lewis, May 



place, they allowed the cold wp.tei to extracl the tanning prin- 

 ciple, and then immerfed the flciiiG. 



I could not learn that it made any difference, whether the 

 vegetables were ui'ed in a green (late, or were dried previous to 

 their being ufed. But 1 underftood it was necefiary to avoid 

 foaking them in water after they were gathered, as tliis would 

 carry off part of their tanning principle. 



After the llcins have imbibed a fuihcient portion of the tan, 

 they are llretched upon (licks, and expofed to the air. When 

 dried, thofe intended for upper-leathers are rubbed upon a door, 

 to increafe their ilexibility. 



Chemills have afcertained, that tlie gallic acid, though natn-r 

 rally connected w-i[h tan, may be feparated from it, and is alto- 

 gether a different fubilance ; but they have not afcertained 

 what tan is, nor the mode in which it operates. In all the cafes 

 that fell under my notice, it appeared that the tan never pro- 

 duced its effecft, in hardening or corrugating the leather, and 

 rendering it impervious to water, until after the (kins were dried, 

 and expofed fome time to the air, juff as the ink is never good 

 until after it has been frequently (liaken and expofed to the air. 



The tan leaves the (kins of a brown colour, and the black dye 

 is never applied until after the leather is made into fhoes. The 

 black dye is communicated by anointing the flioes with a folu- 

 tion of fulphate of iron ; and fometimes, where this cannot be 

 got, they have rccourfe to a ferruginous fpring. The iron flrikes 

 a black colour with the tan previouily exilling in the leather, 

 and, at the fame time, renders it more impervious to winter. 



The (kins of horfes and black cattle, who have either died, 

 or fallen from rocks, together with thofe of a few beafls flaugh- 

 tered for their ov/n ufe, are chiefly prepared In this way, and 

 are generally fufficient for the internal confumptlon of the peo- 

 ple. The thicker (kins are ufed fr.r foles, and the thinner, and 

 more flexible, for upper leathers. In places reforted to by (hip- 

 ping, they commonly ufe fpun hemp and rofni for (litching their 

 fhoes. In other places, they ufe a fine thong of tanned horfe 

 leather for this purpofe ; and it is furprifing lio-w tight and neat 

 fome can make (hoes by tills lall mode of (litching. 



I have had (hoes (provincially called broghar, or brogues) tan- 

 ned and made in the way here defcribed, which were mucli 

 eafier for the feet, afforded a firmer (lep upon craggy moun- 

 tains, and laded longer, by double the time, in traverfing moors, 

 and other rough ground, than I ever experienced in the beft 

 London leather of equal thicknefs. 



I (hould have obferved, that extracting the tan by boiling, is 

 always reckoned the moll ceconomical pra6lice, as it extra£l5 

 a much greater proportion of the fluff from the fame mate- 

 rials, and enables them to make the liquor of a certain known 



ftrength. 



