The bark is removed by a kind of ax, parallel cuts being carried around the tree transversely and united by others in a longitudinal direction, so as to produce oblong sheets of bark. Care must be taken not to cut into the inner bark, or the tree would be killed. The pieces of cork are flattened out by heat or by weights, and are slightly charred on the surface to close the pores. Cork is light, impervious to water, and by pressure can be greatly reduced in bulk, returning again to its original size. These qualities render it peculiarly serviceable for the stopping of vessels of different kinds, for floats, buoys, swimming-belts or jackets, artificial limbs, etc. Corks for bottles are cut either by hand or by means of a machine. The best corks are cut across the grain. The Story in a Giant Cannon Origin of the Cannon. The shotgun and rifle, the familiar weapons of the sportsman and the foot-soldier, are not the ancestors of the cannon, as might be surmised. On the contrary, the cannon was the predecessor of the musket and its successors. The rifle, however, antedated the rifled cannon, the type of modern artillery. We do not know when cannon first appeared, but it may have been soon after the discovery of gunpowder in Europe. This explosive seems to have been known in China long before knowledge of it reached the west, but we do not know to what extent it was developed and used in that country. [Illustration: THREE-INCH FIELD GUN UNDER TEST AT FORT RILEY, KANSAS In the trials conducted by the Board of Ordnance and Fortification of the United States Army. This gun and carriage, complete, weighs 2,020 pounds. Charge, 18.5 ounces of smokeless powder. Weight of projectile, 15 pounds. Muzzle velocity, 1,800-foot seconds. _Courtesy of the Bethlehem Steel Co._]