84 THE SCIENTIFIC ASPECTS OF TANNING. 



addition of Hydrate of Lime to precipitate the Chalk, thus enabling 

 the tanner to choose the most favourable situation, irrespective of 

 the properties of the water. At present we are not aware of 

 tanyards where this process is applied. 



Tanning materials will be our next subject. Samples of most 

 are on the table before us. Oak Bark claims our first attention. 

 In its different ages of growth, going under the names of Coppice, 

 Store Flittim, or Timber Bark. The youngest, Coppice, contains 

 a large proportion of extractive matter, which tends to mellow the 

 action of the Tannic acid at this stage ; a picked sample which has 

 little or no epidermis, will yield as much as 12*35 per cent 

 tannic acid. Messrs. Mulligan and Bowling in their careful series 

 of analyses, give us the tannic acid in Oak Bark — ■ 



50 years old... ... 8*90 



70 years old... ... 6.12 



In certain localities, as the tree grows, the rough exterior 

 epidermis thickens rapidly, lessening year by year the value of the 

 bark. No other tanning material with which we are acquainted 

 can occupy the same position as Oak Bark, possessing in itself all 

 that was necessary to make a good tough wearable leather. Up to 

 the year 1830, when the trade was permitted to go free of all 

 excise restrictions, oak bark was the staple material on which the 

 tanner relied. But the enormous increase and developement of 

 the trade soon proved that, unless other materials of greater 

 strength and mure speedy action were discovered, leather could not 

 be produced in sufficient quantities to supply the demand. 



Various sub^iances have been imported, amongst the foremost 

 we must place Valonm. The Acorn cup df the Quercus cegilops 

 growing on the northern shores of the Levant, Smyrna being the 

 principal port Iroiu which it is exported. In 1830 we imported 

 86,538 cwt. J in 18,5 England received 24,131 tons. Although 

 the Morea, Inland ^ ot Greece, Asia Minor, and Palestine seem all 

 adapted to the growth uf this description of oak, which with a 

 little care and attention in planting would yield ten times the 



