210 TANNING. 



getables which are of an astringent nature, contain 

 tannin (which may be known by their giving preci- 

 pitates with gelatine, insoluble in water), and will 

 answer this purpose. The leaves, branches, fruit, 

 flowers, of a vast number of plants; every part of the 

 oak, as the leaves and acorns, oak saw-dust, and the 

 barks of almost all trees, contain more or less tannin. 

 Mr. Biggins made a great many experiments 

 upon the quantity of tanning principle in various 

 barks, from which he constructed the following 

 table. 



