150 



EXPERIMENTS UPON TANNING MATERIALS. 



The volume of a 8t^^ol of wood, after peeling. 

 The specific gravity of green wood, peeled. 

 The weight of greeu bark. 

 The volume of green bark. 

 The specific gravity of green bark. 

 The weight, of bark dried in the forest. 

 The volume of bark dried in the forest. 

 The specific gravity of bark dried in the forest. 



Without going through the details of these experiments the following comparison of 

 results may be given : . ^ , 



1. The volume of a store of peelable oak increases with age, and m proportion to the 

 size of wood. In the case of trunks from peelable forests tifty-five to sixty-two years 

 old, it is 0.725 cubic meters, and for coppice, 0.521. In the branches and trunks of full 

 grown trees it is 0.430 cubic metern, and for the branches of coppice wood, 0.237. 



2. The quantity of bark which gives a st^re of wood separately is not proportional 

 to the real volume, because then a stfere from a plantation yielding " average bark" 

 should yield much more green bark than one yielding " glossy bark," while the pro- 

 portion is as follows : 



A st^re of peelable wood yields : 



Bark tlriod in 

 th 3 forest. 



" Glossy bark " from branches of coppice 



"Average bark " from branches of full grown tree 



Eark from trunks 16 years old 



Bark from trunks 24 years old 



Bark from trunks 38 years old 



Baik from trunks 55 to C2 years old 



Quintals. 

 0.70 

 1.30 

 1.(2 

 1. .52 

 1.49 

 1.52 



3. The quantities of green bark which a cubic meter of each class of products yields 

 decreases rapidhj as the age increases. The difference is less rapid in bark dried iu the 

 forest; and, as will be further shown, young bark loses relatively more water than 

 that which is old. The justice of this conclusion will appear from the following state- 

 ment : 2 



Bark dried in 

 the forest. 



"Glossy bark" from branches of coppice 



"Average bark" from branches of full grown trees 



Bark from trunks 16 years old 



Bark from trunks 24 years old 



Bark from trunks 38 years old 



Bark from trunks 55 to 62 years old 



4. If we take into account the quantity of bark produced, as compared with the 

 whole amount of oak wood of all kinds (some of which is not peelable), the production 

 of bark will remain almost constant for different ages. 



A cubic meter of wood of all kinds yields as follows : 



Bark dried in 

 the forest. 



Bark from coppices Ifi years old 



B:\rk from coppices 24 years old 



Bark from coppices 38 "years old 



B.-vrk from reserves 55 to 6i years old 



QuintaU. 

 3.80 

 3.84 

 3.87 

 3.32 



Quintals. 

 2. CO 



1 The stere has the same dimensions as the ciMe meter, but is applied to articles like 

 wood, which are piled so as to leave interstices between the pieces, while the latter is 

 used to express the solid contents, no allowance for vacant places. It is also used iu 

 measuring charcoal. 



* According to M. Bouvart the yield of dry bark is 103 kilograms for coppice 15 

 ypar.4old ; 102 kilograms for that which is 20 years ; 101 kilograms for 25 years, and 40 

 kihigrams for trees 48 years old. 



