178 VEGETABLE SUBSTANCES. 



CHAPTER XL 



SUBSTANCES USED IN TANNING. 

 OAK BARK CATECHU MANGROVE MIMOSA, 



THE art of tanning the skins of animals is of very 

 remote antiquity. Pliny attributes the invention of 

 leather to Tychius of Boeotia. But although of so 

 ancient a practice, this art has, until a very recent 

 period, been always carried on by persons wholly 

 unacquainted with any thing concerning it save its 

 practical processes, and who have pursued the rou- 

 tine of operations in which they have been instructed, 

 without knowing the real cause of any of the changes 

 produced. 



Oak bark was for a long time exclusively used for 

 this purpose in England, and after it had served its 

 office in the tan-pit, it was rejected as useless, and 

 supposed to be incapable of yielding farther advan- 

 tage. It is said that our gardeners are indebted to 

 William the Third for teaching them to apply this 

 refuse of the tan-yard to horticultural purposes; he 

 having first introduced the use of it for the purpose 

 of raising orange-trees, as practised in Holland. Its 

 useful qualities in producing artificial warmth for 

 exotic plants were not however generally known or 

 appreciated for many years afterwards, until in 1719 

 the cultivation of pine-apples was first attempted in 

 England. It then came into general use, and has 

 ever since been held in great estimation by gardeners. 

 After coming out of the tanner's pit, if it be laid in a 

 heap for a week or two, fermentation is induced, and 



