The development of the rifle from the old smooth-bore musket, by cutting grooves or channels in the form of a screw in the interior surface, was found so advantageous in increase of precision of aim and length of range, that the rifling of cannon in time followed and is now universally used. Breech loading has also replaced muzzle loading, another vast advantage in the use of artillery. A form of breech-loading cannon was introduced in the sixteenth century, but the advantageous use of this device is of late invention. An important result of these changes is the use of elongated instead of round balls, this permitting of the employment of much heavier projectiles for the same width of bore. Modern Cannon. Until 1888 the largest cannon in use was the 119-ton Krupp, made in 1884 for Italy; but in 1888-90 the same house produced a 135-ton gun for Cronstadt. The heaviest British gun at that time was of 111-ton weight. This threw a projectile of 1,800 pounds with a muzzle velocity of 2,216 feet per second. But there later came a reaction in favor of lighter guns and quick firers. The heavy cannon of recent times are not cast, as of old, but are made of forged-steel by what is known as the building-up process. The different parts of these are called the tube, jacket, hoops, locking rings, trunnion rings, wire winding, etc. Cannons are subject to great stress in firing, this being of two kinds. One is the longitudinal stress, acting in the direction of the length and tending to pull the muzzle away from the breech. The other is the circumferential or tangential stress, which tends to split the gun open in lines parallel to the axis of the bore. These stresses are results of the longitudinal and radial pressures of the gas developed by the ignition and explosion of the powder. Such destructive forces have to be guarded against in the building of a cannon and have led to a great development over the old-time casting processes. As long as projectile velocities under 1,500 feet per second were employed cannons cast in one piece sufficed, but when greater velocities were sought, the pressure grew so extreme that no cast or forged metal tube would stand the strain. [Illustration: THREE-INCH MOUNTAIN GUN AND CARRIAGE Weight of gun, 206-1/2 pounds. Length of gun, 37.25 inches (12.4 calibers). Weight of projectile, 12 pounds. Travel of projectile in bore, 27.55 inches (9.2 calibers). Weight of charge, 12.5 ounces of smokeless powder. Muzzle velocity, 1,224-foot seconds. Muzzle energy, 123-foot tons. Weight of gun and carriage complete, 726 pounds. This gun and carriage break up into four loads of approximately 200 pounds each. The equipment carries 16 complete rounds of ammunition with it, which are divided equally among four boxes. The saddles are so made that the load will go on any saddle. _Courtesy of the Bethlehem Steel Co._] How Cannon are Now Made.