CORK, the external bark of a species of oak (Quercus sober) which grows in Spain, Portugal, France, Italy, Tunis, Algeria and Morocco, and is distinguished by the cellular texture of its bark, and the leaves being ever green, oblong, somewhat oval, downy under neath and waved. The area over which the culture extends is about as follows: Portugal, 600,000 hectares; Spain, 300,000 ha.; Italy, 80,000 ha.; France and her African possessions, 661,000 ha., of which 426,000 are in Algiers and 82,000 in Tunis. The cork oak grows in forests in the company mostly of firs and evergreen oaks, but in a part of Tunis there are forests consisting entirely of cork oaks. The bark of these Tunisian forests is said to be of an extraordinarily excellent kind. France, Great Britain, Germany and the United States re ceive about 85 per cent of the total production of cork. Germany, Russia and the United States have no prohibitory duties on importa tion of cork and cork goods, and admit the material free or with only a trifling impost. Great Britain also permits of the free entry of cork and draws most of its supplies from France, Spain and Portugal. The last named takes the chief place in cork productions, pro ducing nearly one-half of the total growth of the bark—about 450000 quartels out of the million produced. The greater part of this perhaps three-fourths—is the crude bark, while the remainder is in manufactured stoppers. Spain exports only manufactured wares. In the collecting of cork it is customary to slit it with a knife at certain distances, in a perpendicular direction from the top of the tree-trunk to the bottom; and to make two incisions across, one near the top and the other near the bottom of the trunk For the purpose of stripping off the bark, a curved knife with a handle at each end is used. Sometimes it is stripped in pieces the whole length, and sometimes in shorter pieces, cross cuts being made at certain intervals. In some instances, after the perpendicular and transverse incisions are made, the cork is left upon the trees until, by the growth of the new bark beneath, it becomes sufficiently loose to be removed by the hand. After the pieces are de tached, they are soaked in water, and when nearly dry are placed over a fire of coals, which blackens their external surface. By the latter operation they are rendered smooth, and all the smaller blemishes are thereby concealed; the larger holes and cracks are filled up by the in troduction of soot and dirt. They are next loaded with weights to make them even, and subsequently are dried and stacked, or packed in bales for exportation. In the course of eight or nine years the same tree will yield another supply of cork. The quality of the cork im proves with each successive stripping; and the trees continue to live and thrive under the operation for 150 years and upwards. The tree is an evergreen species of oak. It reaches the height of about 30 feet. The outer layer of .bark by annual additions from within gradually becomes a thick soft homogeneous mass, possessing those compressible and elastic properties upon which the economic value of the material chiefly depends. The first stripping
takes place when the trees are from 15 to 20 years of age. This first yield is woody in tex ture, and is useful only as a tanning substance, or for forming rustic work in ferneries, etc.
The uses of cork were well known to the ancients, and were nearly the same as those to which it is applied by us. Its elasticity renders it peculiarly serviceable for the stopping of ves sels of different kinds, and thus preventing either the liquids therein contained from run ning out, or the external air from passing in. The use of cork for stopping glass bottles is generally considered to have been introduced about the 15th century.
The practice of employing this substance for jackets to assist in swimming is very ancient; and it has been applied in various ways toward the preservation of life when endangered by shipwreck. The cork jacket, used to preserve the lives of persons in danger of drowning, may be constructed as follows: Pieces of cork about three inches long by two inches wide, and the usual thickness of the bark, are enclosed be tween two pieces of strong cloth or canvas, and formed like a jacket.without sleeves; the pieces of cloth are sewed together round each piece of cork, to keep them in their proper situation; the lower part of the jacket about the hips is made wide enough to give freedom to the thighs in swimming; and the whole is made sufficiently large to fit a stout man, and is secured to the by two or three strong straps sewed far back on each side, and tied before; the straps being thus placed to enable any wearer to tighten it to his own convenience.
The floats of nets used for fishing are fre quently made of cork. Pieces fastened together make buoys, which afford direction for vessels in harbors, rivers and other places. In some parts of Spain it is customary to line the walls of houses with cork, which renders them warm and prevents the admission of moisture. On ac count of its lightness cork is used in making artificial legs; and from its being impervious to water it is sometimes placed between the soles of shoes to keep out moisture.
In the cutting of corks (when they are made by hand, and not, as is now generally the case, by machinery), the only tool employed is a very broad, thin and sharp knife; and as the cork tends very much to blunt this, it is sharpened on a board by one whet or stroke on each side after every cut, and now and then upon a common whetstone. The corks for bottles are cut length wise of the bark, and consequently the pores lie across. Bungs and corks of large size are cut in a contrary direction: the pores in these are therefore downward — a circumstance which renders them much more defective in excluding air than the others. The parings of cork are used for making Spanish black, and largely in the manufacture of linoleum and similar goods. The United States imports unmanufactured cork annually to the value of over $3,000,000, and manufactured cork to the value of $2,500,000 approximately.