After the pieces are detached 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 artful introduction of soot and dirt. The pieces are next loaded with weights to make them even; and lastly they are dried, stacked, or packed in bales for exportation. Many of the uses of cork were well known to the ancients. Its elasticity renders it peculiarly serviceable for the stopping of vessels of different kinds; and thus preventing either the liquids therein contained from running 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 fifteenth century. The practice of employing this substance for jackets to assist in swimming is very ancient; and it has lately been applied in various ways towards the preservation of life, when endangered by shipwreck. The floats of nets used for fishing are frequently made of cork: pieces fastened together make buoys, which, by floating on the surface of the water, afford direction for vessels in harbours, rivers, and other places. In some parts of Spain it is customary to line the walls of houses with cork, which not only renders them warm, but prevents the admission of moisture. The ancient Egyptians sometimes made coffins of it. On account of its lightness, cork is used for false legs; and, from its being impervious by water, it is sometimes placed betwixt the soles of shoes to keep out moisture. When burned, it constitutes that light black substance known by the name of _Spanish black_. In the cutting of corks for use, the only tool employed is a broad, thin, and sharp knife; and, as the cork tends very much to blunt this, it is sharpened upon a board by one whet, or stroke on each side, after every cut; and, now and then, upon a common whet-stone. The corks for bottles are cut in the length way 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 stopping out the air than the others. The parings of cork are sold to the makers of Spanish black. 239. _The WALNUT is a well-known shell fruit, produced by a tree_ (Juglans regia, Fig. 69), _which grows wild in the northern parts of China and Persia, and has winged leaves; the leaflets, about nine in number, large, oblong, smooth, thick; and the end one with a stalk._