CHAPTER XXVI 



HARVESTING TANBARK 



The barks of the hemlock and of several species of oak were 

 for years the main source of the tannin supply of the United 

 States, but the growing scarcity of these species has led to the 

 introduction of various substitutes, among them quebracho wood 

 extract from South America and chestnut wood extract. The 

 eastern hemlock {Tsuga canadensis) furnishes the only coniferous 

 tanbark in the East. The western hemlock {T. hetero phylla) of 

 the Pacific Coast, which is now used only to a Umited extent, 

 will be in demand in the future, because of the high percentage 

 of tannin it contains. The chief eastern oak whose bark is 

 used for tanning is the chestnut oak {Quercus prinus). In the 

 West the bark of the tanbark oak {Q. densiflora) is extensively 

 harvested for this purpose. Various black and white oaks are 

 used to a limited extent. 



The average per cents of tannin contained in the barks of 

 different species are as follows:^ 



HEMLOCK 



The peeling of bark can be carried on only during the growing 

 season. It begins from the first to the middle of May and lasts 



' Report on the Forests of North America (exclusive of Mexico), by Charles S. 

 Sargent. Vol. IX, Tenth Census. Washington, D. C, 1884, p. 265. 



459 



