Page:Popular Science Monthly Volume 31.djvu/654

636 till it has been improved by cultivation. An article of cork, a bottle-cork, for example, is therefore doubly an industrial product: first, as a substance, the qualities of which have been brought out by perfected processes of cultivation and harvesting; and, secondly, as an article that has been manufactured, either by the hand of man or by a machine. It will hence be profitable to study the processes of cultivating and gathering the cork, and the various industrial applications to which the substance lends itself—subjects concerning which no well-composed account has yet been given.

The bark of the cork-oak is composed of two distinct concentric layers: an inner sheet, which is the active part of the bark, and corresponds with the liber of other trees; and a thicker, outer zone, composed of light, compressible, spongy substance, only slightly permeable to liquids, and constituting the cork proper. Wherever upon the body of the tree the inner sheet, or "mother" bark, is destroyed, no further formation of bark or wood takes place; and even a narrow decortication clear around the tree would cause it most certainly to perish. The other coat, or cork, is inert, and does not contribute to the active functions of vegetation; and this explains how it is possible to strip the cork-oak of its corky envelope without endangering the existence of the tree. The inner bark, moreover, if left untouched, will form yearly new layers of cork which may ultimately, when they have become thick enough, be removed in their turn, and furnish the cork of commerce, also called female cork.

According to the most excellent account of the process, given by M. Matthieu, in his "Flore forestière," the demasclage, or removal of the cork, is done in July or August, when the condition of the sap-movement permits an easy separation from the "mother." The work must be suspended when the winds of the sirocco are blowing, for they would destroy the vitality of the inner bark by drying it up immediately; and about two per cent of the trees are likely to be lost, if the operations are crudely performed, by exposure to the glare of the sun. The renewed young bark, if it is permitted to form itself in contact with the air, is also exposed to the attacks of insects and liable to become cracked. To obviate these disadvantages, M. Capgrand Mothes, a French sylviculturist, has devised a method of clothing the stripped oak-trees, by replacing and leaving upon them for a while the cork-bark which has been taken from them. Having been removed in the shape of two half-cylinders, it is easily tied back upon the trunk with wires, while the joinings are covered with strips of paper. The dress is taken off at the end of three months, when the cork which has been utilized to compose it will be found to have become better seasoned than it would have done by the usual method of stacking it. The new bark, under this protection, will have formed only a thin, superficial crust, and that free from cracks and the marks of insect-stings. This process, which furthermore protects the trees against hot