CORK, is a substance analogous to wood, it is the exterior bark of a tree be longing to the genus oak, which grows wild in the southern parts of Europe. When the tree is fourteen or fifteen years old it is fit to be barked, and may be done successively for several years. The bark always grows up again, and its quality improves as the age of the tree increases. If the bark is not taken off in due time, it splits and peels off by itself, being pushed away by the second growth. The best bark comes from Spain and Portugal : it is taken off in sheets, care being used in keeping them as large as possible. After it is detached from the tree the Portuguese burn or char it, laying the convex side of the bark to the fire in order to straighten and swell it. It is then piled in stacks ready for sale.
Cork is formed into soles for shoes, into corks and bungs for stopping bot tles, &c. into a floatage for the nets of fishermen ; it is employed generally, though perhaps with a considerable de gree of. error, in teaching the art of swimming ; it is also ingeniously used, on account of its lightness, when an am putation of the human leg lies been ne cessary, to supply the deficiency; the Spaniards line stone walls with it, which not only renders their houses very warm, but corrects the moisture of the air ; the Egyptians made of it, which, be ing . covered in the inside with a re sinous composition, preserved their dead bodies. It is burnt to make that light black substance called Spanish black, from its having been first made in Spain.
Cork bark has not only been applied as above, but also in the preservation of life when endangered by shipwreck; the most conspicuous exhibition of its advan tages is in the application of it in the construction of the " life boat," or " cork boat," as it was originally called. See
BOAT, Idle.
A cork jacket too has been revived from an old German discovery, by Mr. Dubourg, to -preserve the lives of persons in danger of drowning, which is construct ed as fOtlows : pieces of cork about thi ee inches long by two wide, and the usual thickness of the bark, are inclosed be tween two pieces of strong cloth or can vass, and formed like a jacket without sleeves ; the pieces of cloth are sewed to gether round each piece of cord, to keep them in their proper situations; Dv! lower j part of the jacket, about the hips, is made like the sante pert of woruens' stays, to give freedom to the thighs in swimming : it is made sufficiently large to tit a robust man, and is secured to the body by two or three strong tapes sewed far back on each side, and tied before. ; the strings are thus placed, to enable any wearer to tighten it to his own conve nience. Cork in its action has the elas ticity of a spring, and when pressed into any aperture, its exerts a force acting out wardly on all sides from the centre. It..is this quality that makes it valuable in shutting out the external air from liquors and elastic fluids ; and it is fitted for this purpose in a degree proportioned to the impermeability of its pores. The elas ticity of cork has also been employed for many other purposes in the arts ; it forms the spring of the lifter in ordinary candle sticks, and where the frame is not heavy, it can be made into a good substi tute for the pulleys and weights of the sashes of windows.