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CANNON

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CANNON

made of iron bars hooped with iron rings. The balls were first stone, afterwards iron. The early cannon had various names, as bombards or culverins; then they were named from the -weight of the ball, as six-pounders; but now they are designated by the diameter of the bore, as 16-inch caliber, or by their weight, as a 25-ton gun. After the great wars of the lyth century vast improvements were effected in the manufacture and use of cannon, but these have been superseded by those of the igth century, and the last have in turn seen themselves replaced by extraordinary improvements and inventions.

The interior of a cannon consists of the vent or breach, the chamber and the bore. The vent is the channel by which fire is brought to the charge, the chamber is the seat of the charge, the bore is the tube along which the ball passes. A cannon must fire accurately, destructively and rapidly without injuring the users. Its maker must provide for the strains caused by its weight and for the explosion's tendency to tear the gun. (Large, heavy cannon are known simply as guns.) The enormously increased weight and inertia of projectiles to-day and their swift rotation in rifled cannon try the gun so severely that steel is now used almost universally. Making a cannon begins by a draughtsman making figures and drawings of every size and with absolute accuracy. His work goes to a mill where steel-forgings are ready. The gun is to consist of a tube, a jacket over this and rings around the jacket. A huge forging is put on a lathe, perhaps 100 feet long, and the tube is bored out, oiled, tempered and rebored. This time the inside of the tube is cut with a spiral groove, the rifling, which, when the shell is fired, gives it a rotary motion, increases its range, steadiness and accuracy, and keeps the point in the direction of flight. Meanwhile the rings and jacket are made in a similar way. Putting these parts over the tube completes the gun. But all must fit as tightly together as if the gun were one solid piece of steel. This is done by playing oil the cooling and contraction of metal and its" heating and expansion against one another. The tube is kept cold, but the jacket is heated a day or two to 700°. Then the tube is stood upright, the hot jacket quickly slipped down on the cold metal, and the gun left to cool two days while the jacket shrinks tight. Finally, the gun is taken to a lathe again, and here, while it is in a horizontal position, the hoops or rings are shrunk on.

The built-up gun, as such a cannon is called, resulted from shrinking a hoop over the breech of an American cannon used in the Civil War. The hoop strengthened the gun so much that others were ordered and the process perpetuated. The wire-

wound gun is a tube wound about with a ribbon or thin band of steel relate, great tension being used while winding. As ribbons of steel are much stronger than large hoops, the wire-wound cannon is stronger still than the built-up cannon.

Cannon are of various sorts. Guns are heavy cannon intended to throw solid shot with large charges of powder, and are distinguished from other cannon by their great weight and length and by the absence of a chamber. It is replaced by a breech-block, a mechanism that carries the charge into its place. The Vickers-Maxim breech is used in the great cannon of the American navy, and automatically ejects the exploded primer and raises the new load into position. Howitzers are light, short cannon used in battles on land to throw shells into the enemy's ranks at short distances. Mortars are still shorter cannon with a large bore, and are used to throw bombs or shells into the air, so that they will fall into fortified places. Shell-guns are long jcannon used for shooting shells straight at an object. Cannon are also divided into smoothbore and rifled cannon, though few smoothbores are now in use. Cannon are made of iron, steel and bronze or brass. Heavy cannon are now made in a great many different shapes. One of the largest kinds now used in the forts of the United States is the Rodman gun. Some of these guns are so large that they will carry a ball 20 inches in diameter. The Armstrong gun is one of the best modern heavy guns. It has been made ' as large as 13^-inch caliber. The Krupp guns have become celebrated because of their enormous size and great durability. They have been made weighing over 120,000 pounds. The gatling gun is a machine-gun, constructed with ten barrels, which are revolved around an axis by a handle. As each barrel comes to a certain point, a cartridge is pushed into it by a machine and fired. As many as 400 shots can be fired in a minute and with great range and precision. Some of the most powerful modern cannon are sighted for 8,700 yards, and at that distance may be relied upon to strike an object ten feet high. In battle, however, fire is rarely opened at a greater distance than 3,000 yards. G-athmann and Zalinski invented pneumatic guns, using compressed air, to throw shells three miles that contained 100 Ibs. of dynamite or 500 of guncotton, but they did not succeed in real war. Machine-guns, rapid-fire guns and revolving cannon are now the most important kinds of cannon. The United States sea-coast defense has a 16-inch cannon that far surpasses the Armstrong, French and Italian cannon of 16.25 to 17.7 inches in power and range. It is a third more powerful than the Armstrong Mid more