208 



I selected trees of each sort, which to appearance 

 had the same chance of growing, — their health, ex- 

 posure, and the soil they grew in being the same ; of 

 the same age, (16 years,) and each pair admeasuring 

 the same over the bark. The common oak bark lost 

 seven-eighteenths of its weight when green, in dry- 

 ing ; the Turkey oak bark lost eight-eighteenths, and 

 weighed, when dry, from one-sixteenth to three-six- 

 teenths, or at an average, about one-eight more than 

 the common oak bark. 



Wishing to know the relative value of each kind of 

 bark, I took 480 grains of the dry bark, and proceed- 

 ed to ascertain the quantity of tannin, or the tanning 

 principle contained in each kind, by Sir Humphrey 

 Davy's method. — See his Elements of Agricultural 

 Chemistry, second edition, page 91. 



I found the above quantity of common oak bark to 

 contain 36 grains of tannin. And the same quantity 

 of Turkey oak bark to contain 28 and four-fifth grains 

 of tannin. So that when the common oak bark is 

 worth L.9 per ton to the tanner, the Turkey oak bark 

 is only worth about L.7 per ton. 



From the above experiment it appears that the 

 bark from an acre of common oak is nearly one-tenth 

 more valuable than from an acre of Turkey oak. 

 Notwithstanding this difference of value, however, I 

 am of opinion, that in particular situations, such as 

 well sheltered places, where the soil is of a light 

 sandy nature, it might be more profitable to plant 

 such places with Turkey oak instead of common oak. 

 As from the rapidity with which the Turkey oak 

 shoots forth, in such situations, above the common 

 oak, I would suppose that it might probably turn out 

 double the weight of bark. 



