BARK. Several kinds of bark, being used for processes in the arts or for medicine, enter largely into commerce. Of the former class are oak bark, cork bark, mimosa or wattle bark, and quercitron bark ; and the most im portant among the latter is Jesuits' or Peru vian bark.. [Crtionox4.] Some others, such RS CINNAMON and CASSIA, are noticed else where.
Oak bark is extensively, and was formerly almost exclusively, used in tanning, for which it is valuable on account of the large propor tion which it contains of the peculiar astrin gent called tannin. Sir H. Davy has shown that Si lbs. of oak bark are equal in efficiency to 2f lbs. of galls, 3 lbs. of Sumach, 7i lbs. of the bark of the Leicester willow, 111bs. of the bark of the Spanish chestnut, 18 lbs. of elm bark, or 211bs. of common willow bark. The quantity of tannin, however, varies both with the age of the trees, and with the season in which they are cut ; being more abundant in the bark of young than of old trees, while if taken in the spring the bark has four and a half times the quantity, in a given weight, that it would have in the winter.
Cork bark, or Cork, is the outer bark of an evergreen oak (Querens sober), which grows abundantly in Portugal, Spain, the south of France, and Italy. Most of the cork bark used in Europe is supplied by Spain and Por tugal, but that of the best quality by France. As the cork is really dead bark, it maybe care fully removed without injuring the tree, which may be stripped every eight or ten years, be ginning when it is fifteen years old. At each successive stripping the produce becomes greater in quantity, and better in quality. The inner bark, which contains much tannin, can not be removed without destroying the tree.
Cork bark is usually charred lightly when taken from the tree, to improve the texture by closing the pores; but this process, which is liable to impart a disagreeable flavour to liquors stopped with cork so treated, is not required for the thinner but closer layers of young bark. The lightness of cork recant, mends its use as floats for fishing-nets, for life-preservers, for insuring the buoyancy of life-boats, and for similar purposes ; while its compressibility and elasticity, being combine( with a closeness of pore which prevents flu passage of liquids, render it valuable for stop ping bottles and casks. [CORR-MANUFACTURE..
Mimosa, or wattle bark, is collected from tw( species of Mimosa which abound in Nev South Wales, Van Diemen's Land, and Nev Zealand, where it is employed in tanning. I contains about 150 lbs. of pure tannin in ton of bark, which is about three fifths of tin proportion yielded by the best white oal bark ; and it imparts a reddish colour to th( leather.
Quercitron bark is the produce of the Querea mgrs, or tinctoria, a North American oak, am is used as a yellow dye. The colouring matte: resides wholly in the inner bark ; and care needful in extracting it to avoid any admix titre of the tannin of the bark, which wouli give a brown tinge.
The imports of bark for tanning iu 1811 amounted to the very large quantity o: 365,755 cwt., of which more than two-thirds were supplied by Holland and Belgium. Oal bark sells at present from 90s. to 130s. per ton