AN OCEAN FLIGHT
Dropping bombs from an aeroplane, or a dirigible balloon, is a comparatively simple matter.Of course there are complications that may ensue, from the danger of carrying high explosives in the limited quarters of an airship, with its inflammable gasoline fuel, and ever-present electric spark, to the possible premature explosion of the bomb itself.But they seem to be considered minor details now.
On the other hand, while it is comparatively easy to drop a bomb from a moving aeroplane, or dirigible balloon, it is another matter to make the bomb fall just where it will do the most damage to the enemy.It is not easy to gauge distances, high up in the air, and then, too, allowance must be made for the speed of the aircraft, the ever-increasing velocity of a falling body, and the deflection caused by air currents.
The law of velocity governing falling bodies is well known.It varies, of course, according to the height, but in general a body falling freely toward the earth, as all high-school boys know, is accelerated at the rate of thirty-two feet per second.This law has been taken advantage of by the French in the present European war.The French drop from balloons, or aeroplanes, a steel dart about the size of a lead pencil, and sharpened in about the same manner.Dropping from a height of a mile or so, that dart will acquire enough velocity to penetrate a man from his head all the way through his body to his feet.
But in dropping bombs from an airship the damage intended does not so much depend on velocity.It is necessary to know how fast the bomb falls in order to know when to set the time fuse that will explode it; though some bombs will explode on concussion.
At aeroplane meets there are often bomb-dropping contests, and balls filled with a white powder (that will make a dust-cloud on falling, and so show where they strike) are used to demonstrate the birdman's accuracy.
"We'll see how our bomb-release works," Tom went on."But we'll have to descend a bit in order to watch the effect.""You're not going to use real bombs, are you, Tom?" asked Ned."Indeed not.Just chalk-dust ones for practice.Now here is where thebombs will be placed," and he pointed to the three openings in the floor of the amidship cabin.The wire nettings were taken out and one could look down through the holes to the earth below, the ground being nearer now, as Tom had let out some of the lifting gas.
"Here is the range-finder and the speed calculator," the young inventor went on as he indicated the various instruments."The operator sits here, where he can tell when is the most favorable moment for releasing the bomb."Tom took his place before a complicated set of instruments, and began manipulating them.One of his assistants, under the direction of Lieutenant Marbury, placed in the three openings bombs, made of light cardboard, just the size of a regular bomb, but filled with a white powder that would, on breaking, make a dust-cloud which could be observed from the airship.
"I have first to determine where I want to drop the bomb," Tom explained, "and then I have to get my distance from it on the range-finder.Next I have to know how fast I am traveling, and how far up in the air I am, to tell what the velocity of the falling bomb will attain at a certain time.This I can do by means of these instruments.some of which I have adapted from those used by the government," he said, with a nod to the officer.
"That's right--take all the information you can get," was the smiling response.
"We will now assume that the bombs are in place in the holes in the floor of the cabin," Tom went on."As I sit here I have before me three buttons.They control the magnets that hold the bombs in place.If I press one of the buttons it breaks the electrical current, the magnet no longer has any attraction, and it releases the explosive.Now look down.I am going to try and drop a chalk bomb near that stone fence."The Mars was then flying over a large field and a stone fence was in plain view.
"Here she goes!" cried Tom, as he made some rapid calculations from his gauge instruments.There was a little click and the chalk bomb dropped.
There was a plate glass floor in part of the cabin, and through this the progress of the pasteboard bomb could be observed.
"She'll never go anywhere near the fence!" declared Ned."You let it drop too soon, Tom!""Did I? You just watch.I had to allow for the momentum that would be given the bomb by the forward motion of the balloon."Hardly had Tom spoken than a puff of white was seen on the very top of the fence.
"There it goes?" cried the lieutenant."You did the trick, Swift!""Yes, I thought I would.Well, that shows my gauges are correct, anyhow.Now we'll try the other two bombs."In succession they were released from the bottom of the cabin, at other designated objects.The second one was near a tree.It struck within five feet, which was considered good.
"And I'll let the last one down near that scarecrow in the field," said Tom, pointing to a ragged figure in the middle of a patch of corn.
Down went the cardboard bomb, and so good was the aim of the young inventor that the white dust arose in a cloud directly back of the scarecrow.
And then a queer thing happened.For the figure seemed to come to life, and Ned, who was watching through a telescope, saw a very much excited farmer looking up with an expression of the greatest wonder on his face.He saw the balloon over his head, and shook his fist at it, evidently thinking he had had a narrow escape.But the pasteboard bomb was so light that, had it hit him, he would not have been injured, though he might have been well dusted.
"Why, that was a man! Bless my pocketbook!" cried Mr.Damon."I guess it was," agreed Tom."I took it for a scarecrow.
