31 



" I need scarcely mention that the test skins em- 

 ployed in this trial should not be expected to be- 

 come perfect leather, so as to enable the tanner to 

 judge of the quality of the astringent also. That 

 is an operation requiring length of time, and excess 

 of tanning materials, both of which are here inad- 

 missible. 



" In the course of experiments which led me to 

 the adoption of the plan recommended in this 

 essay, I have accumulated a number of compara- 

 tive analyses of the several astringents used in the 

 arts, made with a view to ascertain how the tests 

 would work in all cases, as an index to their tan- 

 ning properties. 



" These I intend to annex to the present paper, 

 but satisfied of the correct action of the test, I 

 omit them for the present, convinced that each 

 individual lot of astringent substance brought to 

 market may differ so widely in composition and 

 quality from each other, that such a table as I 

 might be able to form from the examination of 

 particular samples, (not now at market) would only 

 tend to mislead. 



" My chief hope is, that by the preceding sketch 

 of a process, I have been sufficiently explicit to 

 enable a tanner to proceed for himself towards the 

 attainment of that important object — a knowledge 

 of the comparative value of all the astringent ma- 

 terials which appear at market, in time to regulate 

 his purchase of any." 



purchases of their stock of bark for the year. Those extensively in 

 trade, who necessarily invest thousands of pounds in this expensive 

 material, will need no farther explanation to enable thera to appreciate 

 justly the value of this information. 



