CLASSES OF CANNON. Cannon are classified as guns. howitzers, and mortars. Guns fire at high velocity and therefore low elevation, about 11?' being the maxinmm ; howitzers. shorter than guns of same calibre, have lower velocity, and therefore, range for range, higher angles of ele vation. generally up to 20'; mortars, still shorter in proportion, fire at still lower velocities and at 45' to GO° elevation.
Another classification of cannon, depending upon their use, whether for field. or seacoast purposes. involves no essential ences in the guns themselves, other than the limits of weights imposed by the required mo bility. ( See FIELD ARTILLERY; SIEGE GLTN ; and COAST ARTILLERY.) Net another classifica tion of cannon. depending upon their mode of operation and service. differentiates between the ordinary breech mechanism with separate loading of projectile, charge, and printer, and the rapid fire (or quick-fire) gun, semi-automatic, auto matic, and machine gun. The rapid-fire is one with a breech mechanism opened and closed by a single motion of a lever and loaded with fixed ammunition—projectile, charge. and primer fixed in a metal case, so that all can be inserted at one motion. (They will be found described under RAPID-FIRE Guys.) Semi-automatic guns are those rapid-fire guns in which the energy of recoil is utilized to open the breech, reload, and cock—each round however. inserted by hand and the trigger pulled for each dis charge. Automatic guns are those in which the above utilization of recoil is extended to aII operations. the cartridges being fed automatically in strips or belts, or otherwise, and the gun firing round after round automatically as long as a trigger is pressed.
Machine guns include all guns in which the action is as described for automatic guns, whether the power for operation is derived from the recoil as above, and as exemplified in the Maxim. Colt, and Hotchkiss automatic guns, or is supplied by a cannoneer or motor continuou-ly turning a crank as in the Gatling machine gun and the Hotchkiss revolving cannon. They will
be found treated under MACHINE GUN.
At one time much was promised for guns in which compressed air was employed to throw large quantities of dynamite or other high ex plosive relatively short distances. A pneumatic dynamite for coast defence was invented by Captain L. Zalinski, 1. S. A., and after a number of experiments several of these guns were constructed and installed in fortifications in the 'United States. but these have since been removed as obsolete. These gins were smoothbore, the largest having a tube 50 feet in length and a calibre of 15 inches. Compressed air derived from a compression plant located near by and stored in reservoirs so that it could be used in the gun at a of I000 pounds to the square inch was employed. A range of about 5000 yards was attained with the I5-ineh gulls and projectiles containing 100 pounds of high explosives. The Zalinski gun has also been used at sea. the dy namite cruiser Vesuvius having been constructed with three tubes, and was employed at Santiago, but without the success anticipated. Another form of pneumatic gun is the Sims-Dudley gun. in which a projectile containing, a charge of about four pounds of high explosives is fired by air compressed by the explosion of in a lower barrel. This gun was used with some suc cess during the Spanish-American War. See AIR GUN.
The distinctions between smoothbores and rifles, and between muzzle-loaders and breech loaders, are obvious; all modern guns are breech loading and rifles, but it is customary to desig nate them as 'breech-loading rifles' ( B.L.11.) to avoid confusion with the obsolete guns still in existence.