THE Cork Oak is not so large a tree as the common oak. There are several varieties: a broad leaved and a narrow leaved, which are evergreens; besides other varieties which shed their leaves. The broad leaved evergreen is, however, the most common, and it is the one from which the cork of commerce is chiefly obtained. It was well known in the days of the Greeks and Romans,the latter of whom used it for a variety of purposes, and among the rest for the stopping of bottles. They used it for floats to their nets and fishing tackle; for buoys to their anchors; and when Camillus was sent to the Capitol, through the Tiber, during the siege by the Gauls, he had a life-preserver of cork under his dress.
The Cork Oak is abundant, in Portugal, Spain, part of the south of France, and Italy; on the opposite coast of the Mediterranean, and the Levant. Spain and Portugal supply the greater portion of the cork which is consumed in Europe. The cork is the bark which the tree pushes outwards, as is common to all trees; but here the outer bark is of larger quantity, and is more speedily renewed. When removed, there is a liber, or inner bark, below it, and from this the cork is reproduced in the course of a few years, while the tree is said to live longer, and grow more vigorously, than if the cork were not removed. The first time that the cork is taken off, is when the tree is about fifteen years old. That crop is thin, hard, full of fissures, and consequently of little value; and the second, which is removed about ten years after, is also of an inferior quality. After this, the operation is repeated once in eight or ten years, the produce being greater in quantity, and superior in quality, each successive time. According to Duhamel, a cork-tree, thus barked, will live a hundred and fifty years.
The months of July and August are those which are chosen for removing the cork. The bark is cleft longitudinally, at certain intervals, down to the crown of the root, with an axe, of which the handle terminates in a wedge; and a circular incision is then made from each extremity of the longitudinal cuts. The bark is then beaten, to detach it from the liber; and it is lifted up by introducing the wedged handle, taking care to leave sufficient of the inner laminae upon the wood, without which precaution the tree would certainly die. The bark being thus removed, it is divided into convenient lengths; and it is then flattened, and slightly charred, to contract the pores. This sub-stance is the rough cork of commerce; and it is thus fit to be cut into floats, stoppers, shoe-soles, and other articles of domestic use, by the manu-facturer. The cork of the best quality is firm, elastic, and of a slightly red color. Two thousand five hundred tons of cork were imported into Great Britain in 1827. Cork burned in vessels of a particular construction gives the substance called Spanish black.