Target practice with our big guns aboard a battleship is rather an important occasion, as it is not often done. It is too expensive to fire away hundreds of pounds of powder and projectiles, the cost of which runs into the thousands. But it must be done occasionally.
When it is done, in order to get as nearly as possible to actual war conditions, it is customary to have the unexpected happen. That is to say, the target, which is a big square of canvas on a float, is towed by some other ship, and where or when it is to appear is not known to the men who work the guns. This is to make them quick and resourceful.
“Watch out now, men,” advised the officer. “Arden, keep your wits about you. Remember there is quite a swell on to-day, and allow accordingly when you point the gun.”
It might be stated here that the big guns are moved and controlled by machinery, but the machinery is under the fingers of the pointer and his assistants. By a simple movement of a lever the gun can be shifted up or down or from side to side. And probably all know that elevation is one of the most important matters in firing.
If a gun is taken, or for that matter a bean-shooter, and some projectile is fired or blown through the air, it will be noticed that it goes in a straight line for only a short distance. Then it begins to curve down and fall. This is due to loss of energy, and to the attraction of gravitation.
Now if the gun be held, say, exactly parallel to the earth’s surface, it will be noted that the projectile will go a certain distance. Lower the gun, and it will not go so far. Raise it and the bullet (or bean, if the trial is made with a bean-shooter) will go much farther. And it is this angle of fire that is most important.
By computation it is possible to know at just what angle or inclination to point the gun in order to send its projectile to a certain point at a known distance away. And in order to find this distance it is necessary to use what are called range-finders.
These are something like telescopes, but the science known as triangulation is brought into use, also. So a range-finder on a battleship can in a short time signal to the gun-pointer just how far away a certain hostile ship or a target may be. When the gun-pointer knows the distance, he knows just how much to elevate or depress his gun in order to make the projectile come somewhere near the object at which he is aiming.
“All ready now. I think we’ll get the range soon,” said the officer in charge of the turret where Ned and Frank were stationed.
Every one was on the alert. The lads stood at attention. Into the breech of the big gun had been put the steel projectile, and back of that the powder, hundreds of pounds of it. Frank stood ready to press the trigger, which would detonate the primer and explode the charge. In front of him was the telescope sight, and at his fingers’ ends were the controls that would move the gun whichever way he wished. Ned stood at the ammunition hoist.