22 



ing the degree of astringency or tanning strength 

 in all kinds of bark, which cannot fail to be of very 

 great importance to dealers in that article, parti- 

 cularly to tanners ; as by this means they can in a 

 few hours ascertain the different degrees of strength 

 in all kinds of bark, of course come at once at its 

 real value ; a thing hitherto unknown but by the 

 long and tedious process of tanning: — 



" Of all the manufactures which depend on 

 chemistry for explanation and improvement, that 

 of leather, though highly favoured by the atten- 

 tion of scientific men, is still, perhaps, most in need 

 of their aid. 



" Notwithstanding Seguin's happy discovery of 

 the chemical affinity between tan and gelatine, 

 which promised to introduce something like analy- 

 tic certainty into his art, the practical tanner is yet 

 unable to estimate the goodness of any bark (pre- 

 vious to its actual use,) otherwise than by its ex- 

 ternal characters. He depends wholly on the col- 

 our, taste, and the healthy brittleness, which in 

 many cases requires an experienced eye to distin- 

 guish it from the brittleness produced by decay. 

 By the mere appearance he may indeed discrimi- 

 nate between sound and unsound bark of the same 

 species ; but when both are fresh and healthy, or 

 of different kinds, (for instance, valonia and cork 

 tree bark,) his eye and tongue no longer assist him 

 in determining the proportioned worth of either. 



" Any method therefore which would enable the 

 tanner to ascertain with speed and certainty the com- 

 parative value of astringents, (of which the market 

 always affords a striking variety) by the examina- 



