EXPERIMENTS UPON TANNING MATERIALS. 



151 



5. The yield per cent, of green bark from freshly-cut wood diminishes in proportion 

 as the age increases, and it is the same from the foot of the trunk toward the top, be- 

 cause it contains — 



Of " glossy bark," in the branches, 35 per cent, of tbe volume of fireshly-cut wood. 



Of " average bark," in the branches, 3U per cent, of volume. 



Of " glossy bark," in the trunk, 27 per cent, of volume. 



Of " average bark," in the trunk, 18 per cent, of volume. 



It also results from all the experiments that have been made that the lower part of 

 the trunk, from the soil to a point two or even three meters above, gives a much less 

 per cent, in volume of bark than that above this height. 



6. The loss in weight on the amount of \\ater withdrawn from bark by drying iu a 

 forest diminishes in proportion as the wood is of greater age, and, consequently, from 

 tho foot of the tree toward the top, as follows : 



Of " glossy bark," of the branches, 49 per cent, in weight. 



Of " average bark," of the branches, 45 per cent, in weight. 



Of " glossy bark," of the trunk, 42 per cent, in weight. 



Of " average bark," in the trunk, 32 per cent, iu weight. 



It also results from all experiments that the loss in w»-ight in the lower part of tho 

 trunk, up to 2 meters in height, is a little less— about 13 per cent.— than that which 

 occurs in the trunk at greater height. 



7. Likewise the loss of volume which green bark snfferp in drying in the forest is 

 less for wood of greater age, and, as a consequence, it is less at the loot of the tree 

 than at the top, it being as follows : 



In "glossy bark " of the branches from a green state, 41 per cent. 



In "average bark " of the branches from a green state, 30 per cent. 



In " glossy bark " of the trunk iu a green state, 34 i>er cent. 



In " average bark " of the trunk in a green state, 21 per cent. 



Tbe decrease of percentage iu volume is slightly less than tho loss per cent, in weight. 

 The difference is greater with bark taken from stems of less ago than it is when taken 

 trom those that are older. 



8. The volume is almost constant for a given weight of bark. It is always greater 

 in bark dried iu the forest than in green bark, and it also increases with the age of 

 peel able wood. 



One quintal of bark measures as follows in cubic meters : 



For this purpose it would be convenient to employ reduction-tables for converting 

 cubic meters into the corresponding weight of "glossy" or "average" bark, as well 

 as green bark, into bark that was forest-drieil . 



9. In comparing the peelable wood of tho trunk with that of the branches, as also 

 the bark yielded by the stem with that from the branches, we get different results, 

 according as it may be " glossy " or " average " br.rk. 



To 100 stores of oak yielding " glossy bark " in tho trunk we have 10.8 stores of 

 peelable wood in the branches. 



To 100 stores yielding " average bark " we have 57.5 stores of peelable wood in the 

 branches. 



To lOO cubic meters of oak yielding " glossy bark" iu tho trunk we have 4.9 cubic 

 meters of peelable wood in the branches. 



To 100 cubic meters yielding " average bark " in the trunk we have 33 cubic meters 

 of peelable wood in the branches. 



To 100 kilometers of green " glossy bark " from the trunk we have 6.4 kilometers in 

 the branches. 



To 100 kilograms of green " average bark " from the trunk we have 61 kilograms in 

 the branches. 



To 100 kilograms of " glossy bark " from the trunk, dried iu the forest, we have 5.5 

 kilograms iu the branches. 



To 100 kilograms of " average bark" from the trunk, dried in the forest, we have 50 

 kilograms in the branches. 



10. The specific weight of green oak wood not peeled is generally uniform in young 

 plantations. But in older trees it varies between 0.94 to 1.00 ; but the specific weight 



