14 



CALIFORNIA TANBARK OAK. 



The long dry season of California is highly favorable to the tanbark 

 industry , since it obviates precaution against rain. Bark held over 

 winter must be sheltered, since more than 25 per cent of tannin is 

 leached out by rain in one winter. Dampness also causes mold, 

 which injures the leather and is difficult to get rid of. 



QUALITY OF THE BARK. 



The proportion of tannin varies with the part of the tree from which 

 the bark is taken and with the local and geographical situation of the 

 tree. Old bark near the base of the trunk contains the highest pro- 

 portion. The color of a cross section of fresh bark is an index of the 

 quality in this respect ; bark richest in tannin is a deep red, while the 

 poorest is pale or yellowish. Bark is not considered ripe until it has 

 formed three layers, a rougher outer "ross," a central "meat," and 

 an inner "fiber." Before it has divided thus the tannin content is 

 low. Trees in virgin stands arrive at this maturity at from 55 to 70 

 years of age. 



The variation in bark quality on a typical tree is shown in Table 6 : 



TABLE 6. Analyses showing distribution of tannin from the base to the top of the tree. 1 



1 Tree 18 inches in diameter 4 feet from the ground, and 96 feet high, in northerly h'ollow, southern Hum- 

 boldt County. 



Sunshine and light increase the secretion of tannin. For this 

 reason the best bark grows on ridges, and the southern districts yield 

 a richer product than the northern. Bark from the Santa Lucia 

 Mountains, the southernmost of all the districts, is the richest in the 

 market and averages as high as from 20 to 24 per cent. According 

 to the tanners who have used bark from widely separated districts, 

 that grown in the "Bald Hills" district in the interior, beyond the 

 influence of the sea fogs, is richer than that from the coast, where the 

 trees are shaded by redwoods and are in the fog belt. Bark from the 

 coast of Oregon is low in tannin, with an average of only 12 or 14 

 per cent. 



