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chiefly depends on the increase of weight which a 

 hide acquires during the process that converts it 

 into leather. This in strong (sole) leather is gene- 

 rally one-third of the dry weight ; or, what tanners 

 are more accustomed to calculate on in Ireland, 

 the finished leather is half the weight of the hide 

 when fresh from the slaughter-house. The ex- 

 tractive matter forms an important part of this 

 weight, and therefore, any test which the manu- 

 facturer might apply to ascertain the tanning power 

 of an astringent material, and which acted only on 

 pure tan, would completely mislead him. 1 am 

 inclined to think that any gallic acid present is also 

 absorbed by the skin. In spent ouze the power of 

 striking black precipitates with solutions of iron is 

 lost, and transferred to the leather, particularly 

 that made with oak bark. In short, the tanner 

 wants something which, when presented to an as- 

 tringent infusion, will seize on, and enable him to 

 estimate every thing which would (in his process 

 on the large scale) contribute to the weight of his 

 leather, 



" I know nothing which can do this so well as the 

 skin itself, and I find that by a little management 

 it may be made to yield us the information we 

 require, quicker than has hitherto been thought 

 possible. 



It cannot be doubted that a strong bull hide 

 will continue to absorb tanning matter for two 

 years, if the process be so arranged ; but if we al- 

 ter the usual proportion of the materials, the result 

 as to time, will differ exceedingly. If a fresh skin 



