The Tom Swift Megapack

by Victor Appleton

  “And very clever it is,” said Mr. Damon. “Do you suppose the danger is all over, Tom?”

  “For the time being, yes. But we must unship that damaged propeller, and go on with the two.”

  The necessary orders were given, and several men from the engine-room at once began the removal of the damaged blades.

  As several spare ones were carried aboard one could be put on in place of the broken one, had this been desired. But Tom thought the accident a good chance to see how his craft would act with only two-thirds of her motive force available, so he did not order the damaged propeller replaced. When it was lowered to the deck it was carefully examined.

  “What made it break?” Ned wanted to know.

  “That’s a question I can’t answer,” Tom replied. “There may have been a defect in the wood, but I had it all carefully examined before I used it.”

  The propeller was one of the “built-up” type, with alternate layers of ash and mahogany, but some powerful force had torn and twisted the blades. The wood was splintered and split, and some jagged pieces, flying off at a tangent, so great was the centrifugal force, had torn holes in the strong gas bag.

  “Did something hit it; or did it hit something?” asked Ned as he saw Tom carefully examining the broken blades.

  “Hard to say. I’ll have a good look at this when we get back. Just now I want to finish that gun test we didn’t get a chance to start.”

  “You don’t mean to say you’re going to keep on, and with the balloon damaged; are you?” cried Mr. Damon, in surprise.

  “Certainly—why not?” Tom replied. “In warfare accidents may happen, and if the Mars can’t go on, after a little damage like this, what is going to happen when she’s fired on by a hostile ship? Of course I’m going on!”

  “Bless my necktie!” ejaculated the odd man.

  “That’s the way to talk!” exclaimed Lieutenant Marbury. “I’m with you.”

  There really was very little danger in proceeding. The Mars was just as buoyant as before, for more gas had been automatically made, and forced into the uninjured compartments of the bag. At the same time enough sand ballast had been allowed to run out to make the weight to be lifted less in proportion to the power remaining.

  True, the speed would be less, with two propellers instead of three, and the craft would not steer as well, with the torn ends of the gas bag floating out behind. But this made a nearer approach to war conditions, and Tom was always glad to give his inventions the most severe tests possible.

  So, after a little while, during which it was seen that the Mars was proceeding almost normally, the matter of discharging the guns was taken up again.

  The weapons were all ready to fire, and when Tom had attached the pressure gauges to note how much energy was expended in the recoil, he gave the word to fire.

  The two big weapons were discharged together, and for a moment after the report echoed out among the cloud masses every soul on the ship feared another accident had happened.

  For the big craft rolled and twisted, and seemed about to turn turtle. Her forward progress was halted, momentarily, and a cry of fear came from several of the members of the crew, who had had only a little experience in aircraft.

  “What’s the matter?” cried Ned. “Something go wrong?”

  “A little,” admitted Tom, with a rueful look on his face. “Those recoil checks didn’t work as well in practice as they did in theory.”

  “Are you sure they are strong enough?” asked Lieutenant Marbury.

  “I thought so,” spoke Tom. “I’ll put more tension on the spring next time.”

  “Bless my watch chain!” cried Mr. Damon. “You aren’t going to fire those guns again; are you, Tom?”

  “Why not? We can’t tell what’s the matter, nor get things right without experimenting. There’s no danger.”

  “No danger! Don’t you call nearly upsetting the ship danger?”

  “Oh, well, if she turns over she’ll right herself again,” Tom said. “The center of gravity is low, you see. She can’t float in any position but right side up, though she may turn over once or twice.”

  “Excuse me!” said Mr. Damon firmly. “I’d rather go down, if it’s all the same to you. If my wife ever knew I was here I’d never hear the last of it!”

  “We’ll go down soon,” Tom promised. “But I must fire a couple of shots more. You wouldn’t call the recoil checks a success, would you?” and the young inventor appealed to the government inspector.

  “No, I certainly would not,” was the prompt answer. “I am sorry, too, for they seemed to be just what was needed. Of course I understand this is not an official test, and I am not obliged to make a report of this trial. But had it been, I should have had to score against you.

  “I realize that, and I’m not asking any favors, but I’ll try it again with the recoil checks tightened up. I think the hydrostatic valves were open too much, also.”

  Preparations were now made for firing the four-inch guns once more. All this while the Mars had been speeding around in space, being about two miles up in the air. Tom’s craft was not designed to reach as great an elevation as would be possible in an aeroplane, since to work havoc to an enemy’s fortifications by means of aerial bombs they do not need to be dropped from a great height.

  In fact, experiments in Germany have shown that bombs falling from a great height are less effective than those falling from an airship nearer the earth. For a bomb, falling from a height of two miles, acquires enough momentum to penetrate far into the earth, so that much of the resultant explosive force is expended in a downward direction, and little damage is done to the fortifications. A bomb dropped from a lower altitude, expending its force on all sides, does much more damage.

  On the other hand, in destroying buildings, it has been found desirable to drop a bomb from a good height so that it may penetrate even a protected roof, and explode inside.

  Once more Tom made ready to fire, this time having given the recoil checks greater resistance. But though there was less motion imparted to the airship when the guns were discharged, there was still too much for comfort, or even safety.

  “Well, something’s wrong, that’s sure,” remarked Tom, in rather disappointed tones as he noted the effect of the second shots. “If we get as much recoil from the two guns, what would happen if we fired them all at once?”

  “Don’t do it! Don’t do it, I beg of you!” entreated Mr. Damon. “Bless my toothbrush—don’t do it!”

  “I won’t—just at present,” Tom said, ruefully. “I’m afraid I’ll have to begin all over again, and proceed along new lines.”

  “Well, perhaps you will,” said the lieutenant. “But you may invent something much better than anything you have now. There is no great rush. Take your time, and do something good.”

  “Oh, I’ll get busy on it right away,” Tom declared. “We’ll go down now, and start right to work. I’m afraid, Ned, that our idea of a door-spring check isn’t going to work.”

  “I might have known my idea wouldn’t amount to anything,” said the young bank clerk.

  “Oh, the idea is all right,” declared Tom, “but it wants modifying. There is more power to those recoils than I figured, though our first experiments seemed to warrant us in believing that we had solved the problem.”

  “Are you going to try the bomb-dropping device?” asked the lieutenant.

  “Yes, there can’t be any recoil from that,” Tom said. “I’ll drop a few blank ones, and see how accurate the range finders are.”

  While his men were getting ready for this test Tom bent over the broken propeller, looking from that to the recoil checks, which had not come up to expectations. Then he shook his head in a worried and puzzled manner.

  CHAPTER XVII

  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 the bombs 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.”

  “Well, it proved the accuracy of your aim, at any rate,” observed Lieutenant Marbury. “The bomb dropping device of your aerial warship is perfect—I can testify to that.”

  “And I’ll have the guns fixed soon, so there will be no danger of a recoil, too,” added Tom Swift, with a determined look on his face.

  “What’s next?” asked Mr. Damon, looking at his watch. “I really ought to be home, Tom.”

  “We’re going back now, and down. Are you sure you don’t want me to drop you in your own front yard, or even on your roof? I think I could manage that.”

  “Bless my stovepipe, no, Tom! My wife would have hysterics. Just land me at Shopton and I’ll take a car home.”

  The damaged airship seemed little the worse for the test to which she had been subjected, and made her way at good speed in the direction of Tom’s home. Several little experiments were tried on the way back. They all worked well, and the only two problems Tom had to solve were the taking care of the recoil from the guns and finding out why the propeller had broken.

  A safe landing was made, and the Mars once more put away in her hangar. Mr. Damon departed for his home, and Lieutenant Marbury again took up his residence in the Swift household.

  “Well, Tom, how did it go?” asked his father.

  “Not so very well. Too much recoil from the guns.”

  “I was afraid so. You had better drop this line of work, and go at something else.”

  “No, Dad!” Tom cried. “I’m going to make this work. I never had anything stump me yet, and I’m not going to begin now!”

  “Well, that’s a good spirit to show,” said the aged inventor, with a shake of his head, “but I don’t believe you’ll succeed, Tom.”

  “Yes I will, Dad! You just wait.”

  Tom decided to begin on the problem of the propeller first, as that seemed more simple. He knew that the gun question would take longer.

  “Just what are you trying to find out, Tom?” asked Ned, a few nights later, when he found his chum looking at the broken parts of the propeller.

  “Trying to discover what made this blade break up and splinter that way. It couldn’t have been centrifugal force, for it wasn’t strong enough.”

  Tom was “poking” away amid splinters, and bits of broken wood, when he suddenly uttered an exclamation, and held up something. “Look!” he cried. “I believe I’ve found it.”

  “What?” asked Ned.

  “The thing that weakened the propeller.
Look at this, and smell!” He held out a piece of wood toward Ned. The bank employee saw where a half-round hole had been bored in what remained of the blade, and from that hole came a peculiar odor.

  “It’s some kind of acid,” ventured Ned.

  “That’s it!” cried Tom. “Someone bored a hole in the propeller, and put in some sort of receptacle, or capsule, containing a corrosive acid. In due time, which happened to be when we took our first flight, the acid ate through whatever it was contained in, and then attacked the wood of the propeller blade. It weakened the wood so that the force used in whirling it around broke it.”

  “Are you sure of that?” asked Ned.

  “As sure as I am that I’m here! Now I know what caused the accident!”

  “But who would play such a trick?” asked Ned. “We might all have been killed.”

  “Yes, I know we might,” said Tom. “It must be the work of some of those foreign spies whose first plot we nipped in the bud. I must tell Marbury of this, but don’t mention it to dad.”

  “I won’t,” promised Ned.

  Lieutenant Marbury agreed with Tom that someone had surreptitiously bored a small hole in the propeller blade, and had inserted a corrosive acid that would take many hours to operate. The hole had been varnished over, probably, so it would not show.

  “And that means I’ve got to examine the other two blades,” Tom said. “They may be doctored too.”

  But they did not prove to be. A careful examination showed nothing wrong. An effort was made to find out who had tried to destroy the Mars in midair, but it came to nothing. The two men in custody declared they knew nothing of it, and there was no way of proving that they did.

  Meanwhile, the torn gas bag was repaired, and Tom began working on the problem of doing away with the gun recoil. He tried several schemes, and almost was on the point of giving up when suddenly he received a hint by reading an account of how the recoil was taken care of on some of the German Zeppelins.