BARK, FOIt TANNINC. The B. of many trees is capable of being used for tanning (q.v.), but those kind:3 of B. are preferred which particularly abound in tannic acid. Oak 13. is principally used in Britain and throughout Europe; also in North America, although that of America is obtained from species of oak different from the European; in Spain, the inner layer of the B. of the cork oak, or cork-tree, is employed, and it is to sonic extent imported into Britain for the use of tanners. The 13. of the chestnut is also much esteemed. Larch II. and willow 13. are used in preparing some kinds of leather. The 11. of the birch and that of the alder are also birch B. being, however, more esteemed for steeping fishermen's nets and cordage, to preserve them from rotting, than for the preparation of leather. Different species of acacia (q.v.) and of eucalyptus (q.v.) furnish barks used for tanning in Australia, some of which have, to a small extent, become articles of commerce.
The barLing of trees can be accomplished with facility only in spring. when the sap has begiin to timeline. The tree being felled, the rough external lifeless parts of the 13. are removed as useless, by means of a sharp instrument called a scraper; the smaller branches are cut into lengths of about 2 ft., and their B. is loosened by beating with a
mallet, and easily taken off—as boys at the same season make plane-tree whistles; the B. of the trunk and main branches is cut through by a chisel-like instillment, called •a into siinilar lengths, each of which is divided longitudinally, and finally stripped off by the aid of mallets, chisels, etc. The B. is sometimes dried in sheds, being placed on narrow shelves or frames in such a was that there may be a very free circulation of air about it; sometimes in the open air, when it is very generally made to rest in a sloping. position against trunks of trees placed horizontally at a little distanee from the ground, the larger pieces of B. being placed so as to protect the smaller both from sun and rain. Great care is necessary in the drying of 13.. as it is much spoiled if allowed to get moldy, and is liable to suffer injury from rain or from the exposure of its inner surface to the sun.—Oak and birch B. are usually about equal hi their price, which. however, varies very much. from S.14 to £8 per ton. Larch B. is much less valu able; it is also of much greater bulk in proportion to its weight. The B. is a very important Source of the revenue derived from many woods and coppices.