SPRUCE-BARK. 507 



stage made of poles, with the cambium side downwards to pro- 

 tect it against rain. As soon as it is dry it is piled between 

 stakes like firewood, being well trodden down in the stacks. If, 

 as is usually and most conveniently the case, the bark is sold in 

 stacks, they should be made by an employee of the forest owner ; 

 in Wiirtemberg, bark is packed in bales for transport. The 

 bark may also be sold at so much a tree. 



A stacked cubic meter of old oak-bark weighs 130 — 200 kilos 

 (4 to 6 cwt. per load of 50 cubic feet) and more, according to 

 the amount of moisture it contains. More fresh bark goes to a 

 stack than dry bark, for it is easier and softer to pack in the 

 former case. 



Sale by the amount of peeled wood is more uncertain than in 

 the case of young bark, owing to great variability in the pro- 

 portion of bark to peeled Avood ; for according to the age of the 

 trees the wood may be proportional to the bark in any ratio 

 from 3 to 1, up to 6 to 1, or even 8 to 1 in the case of very 

 large trees, i.e., there are 3, 6 or 8 cords of wood to 1 cord of 

 bark. (In the case of oak-trees 55 to 62 j^ears old, Baur found 

 this ratio about 4 to 1.) In old oak trees the quantity of bark 

 is greater in the crown, which contains 2, 4 and 6% more bark 

 than the stem for the same volume of wood ; this is due to the 

 larger surface of the branches than the stems. 



As regards utilization of the much more valuable bark from 

 the branches of old oak trees, von Frivolin has made numerous 

 experiments, showing that there is a gain of 25 to 30 % in 

 utilizing the bark, compared with the mere use of the unpeeled 

 wood for fuel. The oaks in question were lopped of all their 

 branches in the spring, and the stem felled in the succeeding 

 winter. 



2. Spruce-Bark. 



Spruce-bark is much more extensively harvested than old 

 oak-bark, and in eastern and southern Germany and the adjoin- 

 ing Austrian districts when mixed with Knoppern galls, valonea 

 and silver-bark, it is largely used for tanning. It can, however, 

 be used only in the preliminary stages of tanning, or for tanning 

 thin skins ; thick skins are only tanned with spruce-bark when 

 largely mixed with other tanning materials. As most spruce forests 



