S02 



TANNING. 



When a portion of cutis is macerated for some 

 hours in water, with agitation and pressure, the 

 blood, and all the extraneous matter with which it 

 was loaded, are separated from it, but its texture 

 remains unaltered. On evaporating the water em- 

 ployed, a small quantity of gelatine may be ob- 

 tained. No subsequent maceration in cold water 

 has any farther effect ; the weight of the cutis is 

 not diminished, and its texture is not altered ; but 

 if it be boiled in a sufficient quantity of water, it 

 may be completely dissolved, and the whole of it, 

 by evaporating the water, obtained in the state of 

 gelatine. 



It was mentioned, when treating of chemistry, 

 that gelatine wdth tannin^ or the tanning principle o^ 

 vegetables, formed a combination, which is inso- 

 luble in water. Upon this depends the art of 

 making leather ; the gelatinous part of the skin 

 combining with the tannin of the bark usually 

 employed. 



The process which has long been used in this 

 country is as follows ; the leather tanned in Eng- 

 land consists chiefly of three sorts, known by the 

 name o^ butts or backs, hides, and skins. Butts are 

 generally made from the stoutest and heaviest ox 

 hides, and are managed as follows : after the horns 

 are taken off, tlie hides are laid smooth in heaps for 

 one or two days in the summer, and for five or six 

 in the winter ; they are then hung on poles, in a 

 close room called a smoke-house, in which is kept 

 a smouldering fire of wet tan ; this occasions a 

 small degree of putrefaction, by which means the 

 hair is easily got offj by spreading the hide on a 

 sort of wooden horse or beam, and scraping it with 

 a crooked knife. The hair being taken off, the 

 hide is thrown into a pit or pool of water, to 



