Part 16 (1/2)

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 battles.h.i.+p can in a short time signal to the gun-pointer just how far away a certain hostile s.h.i.+p 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.

A shrill whistle sounded in the turret. The officer in charge listened.

”The range is thirteen thousand yards,” he said. An observer in a crow's-nest on one of the masts had sent in this information. The target was just coming into view, and through the range-finder the distance was quickly computed.

”Aye, aye, sir!” answered Frank in response to the officer. Then he bent down to peer through the telescope sight.

”Can you see it?” asked the officer.

”Not yet--there it is!” cried Frank, suddenly.

”Fire when you sight it properly.”

There was a moment's hesitation. Then Frank's finger pressed on the lever that would send the great projectile on its way.

Such a crash followed that every one was deafened for a moment, in spite of the fact that every man in the turret stood on his toes to lessen the shock, and had his ears stuffed with cotton. The great gun recoiled, the back action being taken up by shock-absorbers, however. A sharp, acrid smell filled the turret. Smoke drifted in. Men staggered back and opened their mouths for air. It seemed as if ten thousand thunder claps had been made into one.

Then came a silence.

”Do you think you hit it?” asked Ned, and his voice sounded so strange, after the great crash, that nearly every one laughed.

”Silence!” called the officer in charge.

Again came a whistle through the speaking tube.

”Yes!” answered the listening officer. ”A hit? Good! You made a hit the first try!” he shouted to Frank. ”Try again.”

Frank blushed with pleasure. But one would never have known that his cheeks reddened, for he was black with grease and oil, having been engaged in going over the mechanism before he made the shot. The smoke was gradually blackening every one.

No sooner had the gun recoiled and moved back into place again, than compressed air rushed automatically into the breech and barrel, to drive out any slow-burning pieces of powder that might possibly ignite the next charge when it was inserted.

”Once more!” called the officer in charge, as up came the supply of powder and the projectile. Ned and his mates shoved them into the gun, and again the breech was closed with a clang.

”Listen for the range,” directed the officer. ”They may try to fool us.”

For in order to get as nearly as possible to actual war conditions, the target-towers were often instructed to run a zigzag course, sometimes close to, and again far away from the firing s.h.i.+p.

Once more came the signal into the turret from the range-finder.

”Eight thousand yards!”