=Oak-barks= (Fr., _Écorces de Chêne_; Ger., _Eichenrinden_).--The barks of several species of oak have valuable tanning properties. They are chiefly:--The common oak (_Quercus Robur_, varieties: _sessiliflora_, Ger. _Traubeneiche_; _pedunculata_, Ger. _Stieleiche_), which is of even greater importance as a timber-tree; the cork-oak (_Q. Suber_); the evergreen oak (_Q. Ilex_); and the American chestnut-oak (_Q. Castanea_). These barks are among the most esteemed tannins as regards quality of leather, but are incapable of giving much weight, and from their bulk are costly to handle, containing only 10-12 per cent. of tannin (quercitannic acid). They give a reddish fawn-coloured leather, and deposit a good deal of bloom, but yield little or no gallic acid. The barks of the cork-oak and evergreen oak from Southern Europe, are stronger and darker-coloured than English bark. The American chestnut-oak contains a peculiar fluorescent principle like æsculin. Our imports of unspecified barks for tanners' and dyers' use in 1880 were:--189,399 cwt., 101,108_l._, from Australia; 123,302 cwt., 32,974_l._, Belgium; 57,232 cwt., 20,988_l._, United States; 22,100 cwt., 6030_l._, Holland; 18,648 cwt., 3676_l._, Italy; 16,151 cwt., 6972_l._, Algeria; 22,669 cwt., 8838_l._, other countries; total, 449,501 cwt., 180,586_l._ Our imports of unenumerated bark-extracts in the same year were valued at:--516,578_l._ from Holland, 92,654_l._ France, 30,187_l._ United States, 16,315_l._ British North America, 12,796_l._ Belgium, 13,769_l._ other countries; total, 682,299_l._ Our re-exports of barks in 1880 were:--19,548 cwt., 10,348_l._, to Germany; 14,627 cwt., 7425_l._, France; 4555 cwt., 3041_l._, Holland; 10,304 cwt., 6080_l._, other countries; total, 49,034 cwt., 26,894_l._ With regard to cork-tree bark, James Gordon & Co., Liverpool, obligingly write that very little comes to England, the great bulk going direct to Ireland, where the consumption is large. The imports at Liverpool in 1880 were 186 tons, average value 8_l._ per ton. Of oak-bark, Hungary, in 1877, produced 25,000 tons, of which, 20,000 were exported to Germany for tanning purposes. The approximate London market values of oak-bark are:--English, 12-16_l._ per load of 45 cwt.; Foreign, tree, 5-8_l._ a ton; ditto, coppice, 6-8_l._ In 1879, Algiers exported 12,660,047 _kilo._ (of 2·2 lb.) of tanning bark.