FIG. 66. HOW A FLAT TRAJECTORY AFFECTS THE PROJECTILE.
Now, the way this gun was made was to rifle the barrel of it, and this gave a turning motion to the projectile when it was fired, that is, it spun around on its long axis, and the trajectory was flat, which means that the path of the projectile in its flight from the gun to its target was only slightly curved.
FIG. 67. HOW A BOW TRAJECTORY AFFECTS THE PROJECTILE.
Both of these things made the projectile deviate from its course the instant it struck the water, or ricochet (pronounced rik-o-sháy) as it is called; that is, it bounced from the water in exactly the same way that a flat stone skips along when you throw it close to the surface of a pond or lake.
The right kind of gun to use on submarine chasers is not rifled, and the projectile should be given a trajectory, or path, that is much the same as that of an arrow; the result is that a shot can be fired at a submarine which is submerged to a depth of 20 feet or so and be effective because the curve of the path is such that the projectile drops straight, or nearly straight, down on the submarine and penetrates the water as shown in [Fig. 67].
FIG. 68. HOW AIR CRAFT CAN SPOT A SUBMERGED SUBMARINE.
Submarine Air Chasers.—Besides the submarine chasers just described, there are two other kinds that have shown great possibilities as destroyers of undersea craft. These are (1) the airship, or dirigible balloon, and (2) the airplane, and it is more than likely that in the near future, should the war keep on, the latter craft alone will be used for submarine chasers.