186 



DIVISION III. 



MISCELLANEOUS PEODUCTS USED IN THE AETS 

 AND MANUEACTUEL^G PEOCESSES. 



Under this division we rank a very heterogeneous assem- 

 blage of materials, many of them exercising immense in- 

 fluence in the commerce of nations. Eirst, we have those 

 which, by the peculiar influence of the chemical principle 

 called Tannin (tannic acid) contained in them, convert the 

 albumen and gelatine of animal tissues into tannates of 

 those bases, thus forming compounds which are insoluble in 

 water, hence the durability of leather. Next we have the 

 varied materials of the dyers^ art, carefully selected and 

 requiring nice manipulation, and the powerful aid of the 

 chemist, to produce the infinitely varied tints of colour 

 which give beauty to the textile fabrics of the weaver ; and, 

 to close the series, we have the gums, resins, and oils, which 

 are applied in numerous ways to the arts of social life. 



