756 Transactions of the American Institute. 



prevent the bark from undergoing such chemical changes during 

 the process, as would lessen the amount of tannic acid or astringent 

 salts derivable thereout; being at the same time a system which 

 will enable the tanner to obtain from his leaches, as a reservoir, any 

 strength and quantity of properly conditioned liquors, that the con- 

 dition and nature of each kind of leather he has in progress, will at 

 an}' and all periods (in the operating of his tan yard), render desirable. 



Before examining to what extent my patents (of the 1 1th of March, 

 1856, 2d of January, 1867, 12th of March, 1867, and 20th of 

 August, 1867, for leaching bark, making liquors, and manufactur- 

 ing bark extracts) have accomplished those ends, beyond the means 

 now in general use among tanners, I will make some preliminaiy 

 observations on the experienced operations of chemists, and of such 

 natural phenomena, with their causes and eflects, as appear to me 

 to have an associate bearing on the objects a tanner endeavors to 

 obtain by leaching bark; and though their recital may only call 

 to your recollection your own previous observations of the same 

 facts with regard to leaching, yet I deem it essential that their con- 

 sideration should be fresh in your memory while I read or explain 

 the value of, and the ground covered, or intended to be covered, 

 by the patents and re-issue for the improvements which I now offer 

 to the consideration of the public. 



I would first call your attention to those facts which are most 

 prominently worthy of the attention of tanners who are using hem- 

 lock bark; because that bark possesses extraordinary powers in the 

 retention of its tanning properties, as for instance: 



1. Saw logs of hemlock trees, after lying for months immersed 

 hi a mill-pond, will admit of being peeled, soon after the true 

 season of peeling has commenced, and then yield a bark little 

 inferior for tanners' use, to that cut down and peeled in due season. 



2. A leach of hemlock bark tan (in common with the tan of oak 

 barks) will drain down a few pails of strong liquor, after it has 

 yielded to water with which it has been well boiled, a liquor only 

 measuring two and a half degrees barkometer proof. 



3. Which leach of hemlock bark tan will subsequently yield to 

 proper steam application, a liquor measuring ten degrees in a quan- 

 tity of liquid equal to one-half the bulk of the bark or tan opera- 

 ted on, that being the general proportion or quantity of a liquor 

 to cover the bark in leach. 



4. And selected pieces, picked from that which has been for 

 years in ploughed ground, will give a similar or greater yield. 



