AMERICAN INSTITUTE. 529 



This operation is repeated two or three times, after which the skin is placed 

 in a pit dug in the ground and smoked the same way their meat is treated. 

 The principal ingredient used by leather manufacturers in preparing sheep- 

 skins is alum. A large number of patents have been taken out for im- 

 proved processes in tanning ; those which are claimed as hastening the 

 process owe their merits to the application of such materials as would be 

 tised in tawing, and the product might be called a tawed-tanned leather. 

 The whole number of patents taken out for tanning processes already 

 exceed one hundred. They may be divided into two classes, the chemical 

 and the mechanical. 



The art of tanning can be defined, in a single sentence, as a chemical 

 union of the skin of an animal with tannic acid ; in other words, leather is 

 a true chemical compound consisting of about fifty-four per cent, of gelatin 

 and forty-six per cent, of tannin. Gluten and tannin in liquid form unite 

 instantaneously. This simple fact was first discovered and proved by 

 Deyeus, a French chemist. Since his time much has been done by chemists 

 to ascertain the amount of tannin contained in various vegetable formations. 

 Long lists are found in several English works, at the head of which stand 

 kino, catechu, and japonica, a preparation from an East Indian vegetable ; 

 nut-galls, which are the excrescences found on a dwarf oak in warm coun- 

 tries; oak, sumach, willow, and chestnut. In several of these works no 

 mention is made of hemlock. 



On the use of this bark the Hon. Zadoc Pratt, who has tanned more sole 

 leather than any other one man in the world, at the annual dinner of the 

 Hide and Leather Association in February last, said "hemlock is truly an 

 American bark, and that of the Catskills affords more tannin and is better 

 adapted to make sole leather than any other ; the farther you go from the 

 Catskill mountains the less tannin you find in the hemlock. When wo 

 sent the first hemlock leather to England, John Bull's chemists said it waa 

 not tanned, and declared they could bring it back to hide. The mistake waa 

 perhaps a natural one, but it was none the less a mistake, for after trying 

 their utmost skill upon it, they were obliged to exclaim that they did not 

 know "what those Yankees' red tannin had been doing to it." 



Although our American chemists have not fully investigated this subject, 

 principally because our wealthy tanners have not offered to pay them for 

 it, yet Col. Pratt asserts that hemlock contains more tannin than any other 

 bark, and with it millions of sides are tanned every year. 



The mechanical improvements in the art of tanning since the Revolution 

 have been so great, they may be said to have made a complete revolution 

 in the whole method. For the principal improvements we are indebted to 

 the genius of one man, and I propose in a short sketch of him to present 

 them in detail. 



Col. William Edwards was born in the year 1770, at Elizabethtown, N". 



J. He was the grandson of the celebrated divine. Dr. Jonathan Edwards. 



His mother was Ilhoda Ogden, an elder sister of Gov. Ogden of Nevf 



Jersey. His father was a country merchant and an active Whig. William 



[Am. Inst.J 34 



