TANNING MATEEIALS. . 147 



within 30 years arisen 80 per cent, in France, witb a still upward tend- 

 ency. In 1874 the gain was 6 per cent., and in 1875 it was estimated 

 that the increase would be 20 to 25 per cent., which was in a large de- 

 gree realized. As the value of bark enters largely into the estimate of 

 profit of growing oak coppices, it becomes of the highest importance to 

 determine the circumstances that give it greatest value, and the age at 

 which it can be cut to best advantage, as the relations between weight, vol- 

 ume, and value of wood and bark, and of tanning material in the bark, are 

 changing with the growth, and even at a given time are different in the 

 several parts of the same tree. 



Time of peeling the Bark. — Oak must be peeled between the time that 

 the buds begin to swell and the appearance of leaves. It peels best in 

 cold, damp weather, and not so well when dry and hot. jS^orth and 

 east winds more or less hinder the process. When vegetation is sus- 

 pended by a series of cold days, as may happen in th<3 north and east 

 of France, they are obliged to suspend the operation of peeling, and 

 the process may hold on till midsummer or till after the leaves are fully 

 out. 



Bark is usually peeled from the tree standing, as far up as can be 

 reached. The upper part and branches peel easier. It must be done 

 when the tree has been felled, and often a day or two after the trunk 

 has been peeled.^ 



The yield of bark in an oak coppice can be estimated within 5 per cent, 

 by sampling a few trees, weighing the wood and bark, and allowing a 

 loss of oncythird in the weight of bark in drying. Of course, with a 

 number of trees given, the calculation becomes easy, and the average 

 result quite near. 



A considerable extent of woodlands in Scotland is devoted to the 

 raising of oak for tanning and for the wood. The age at which cut, de- 

 pends on the soil, situation, exposure, and mode of rearing, and is de- 

 termined by the appearance and condition of the bark. On damp soils, 

 where the bark is much covered with mosses, and becomes rough at an 

 earlier age, it may be cut in fifteen years ; but, as a general rule, twenty 

 years is there considered the best, as the bark then contains relatively 

 more tannin than at any other time. In older trees the corky, rough out- 

 side bark has less or little value to the tanner. The best bark comes 

 from trees in a healthy growing condition, with a thick, juicy liber, and 

 that are cut during the ascent of the sap before the leaves have 

 expanded. The bark of a tree in full leaf is quite raateriallj' less in 

 value than when cut before the leaves appear. Where proper attention 

 is given to the cultivation, the brush is cleared off at the time of cutting, 

 and if there be ditches for drainage, these are cleaned out and repaired. 



Before cutting, a ring of bark from the root up to 30 inches is peeled 

 off. After cutting, the tree is trimmed and cut into convenient lengths. 

 All branches down to an inch in diameter are peeled, and in the smaller 

 pieces it is first loosened by beating with a mallet upon a stone. 



When peeled, the bark is spread upon poles some 3 feet above the 



' Tbe quality of bark is good in proportion as the liber is of much thickness and 

 gorged with sap from vigorous growth. It is best from young trees with active vege- 

 tation and in a warm climate. 



The " yeuse" oak is best of all, the " tmizvn" oak next. They grow along the Medi- 

 terranean aud in the southeast of France. The Quercus sessilifolia SLnA Q. peduncnlata 

 furnish most of the bark used in French tanneries, of which the former is best. Peel- 

 ing reduces the volume of wood a fifth or sixth part. 



Schistose and granitic soils with a warm aspect furnish the best bark. It is estimated 

 that 50 to 55 kilograms of dry bark are got from a st^re of tire-wood. Mean price, KX 

 to 12 francs the 100 kilograms dry bark, delivered in port or railroad d^pot ; about half 

 this price is absorbed in handling and freight. {Xanquette.) 



