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  • 1915
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“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.

The guns there were made double, with the extra barrel filled with water or sand, that could be shot out as was the regular charge. As both barrels were fired at the same time, and in opposite directions, with the same amount of powder, one neutralized the other, and the recoil was canceled, the ship remaining steady after fire.

“By Jove! I believe that will do the trick!” cried Tom. “I’m going to try it.”

“Good luck to you!” cried Ned.

It was no easy matter to change all the guns of the Mars, and fit them with double barrels. But by working day and night shifts Tom managed it. Meanwhile, a careful watch was kept over the shops. Several new men applied for work, and some of them were suspicious enough in looks, but Tom took on no new hands.

Finally the new guns were made, and tried with the Mars held on the ground. They behaved perfectly, the shooting of sand or water from the dummy barrel neutralizing the shot from the service barrel.

“And now to see how it works in practice!” cried Tom one day. “Are you with me for a long flight, Ned?”

“I sure am!”

The next evening the Mars, with a larger crew than before, and with Tom, Ned, Mr. Damon and Lieutenant Marbury aboard, set sail.

“But why start at night?” asked Ned.

“You’ll see in the morning,” Tom answered.

The Mars flew slowly all night, life aboard her, at about the level of the clouds, going on almost as naturally as though the occupants of the cabins were on the earth. Excellent meals were served.

“But when are you going to try the guns?” asked Ned, as he got ready to turn in.

“Tell you in the morning,” replied Tom, with a smile.

And, in the morning, when Ned looked down through the plate glass in the cabin floor, he uttered a cry.

“Why, Tom! We’re over the ocean!” he cried.

“I rather thought we’d be,” was the calm reply. “I told George to head straight for the Atlantic. Now we’ll have a test with service charges and projectiles!”

CHAPTER XVIII
IN A STORM

Surprise, for the moment, held Mr. Damon, Ned and Lieutenant Marbury speechless. They looked from the heaving waters of the ocean below them to the young pilot of the Mars. He smiled at their astonishment.

“What–what does it mean, Tom?” asked Ned. “You never said you were going to take a trip as far as this.”

“That’s right,” chimed in Mr. Damon. “Bless my nightcap! If I had known I was going to be brought so far away from home I’d never have come.”

“You’re not so very far from Water ford,” put in Tom. “We didn’t make any kind of speed coming from Shopton, and we could be back again inside of four hours if we had to.”

“Then you didn’t travel fast during the night?” asked the government man.

“No, we just drifted along,” Tom answered. “I gave orders to run the machinery slowly, as I wanted to get it in good shape for the other tests that will come soon. But I told George, whom I left in charge when I turned in, to head for New York. I wanted to get out over the ocean to try the guns with the new recoil arrangement.”

“Well, we’re over the ocean all right,” spoke Ned, as he looked down at the heaving waters.

“It isn’t the first time,” replied Tom cheerfully. “Koku, you may serve breakfast now,” for the giant had been taken along as a sort of cook and waiter. Koku manifested no surprise or alarm when he found the airship floating over the sea. Whatever Tom did was right to him. He had great confidence in his master.

“No, it isn’t the first time we’ve taken a water flight,” spoke Ned. “I was only surprised at the suddenness of it, that’s all.”

“It’s my first experience so far out above the water,” observed Lieutenant Marbury, “though of course I’ve sailed on many seas. Why, we’re out of sight of land.”

“About ten miles out, yes,” admitted Tom. “Far enough to make it safe to test the guns with real projectiles. That is what I want to do.”

“And we’ve been running all night?” asked Mr. Damon.

“Yes, but at slow speed. The engines are in better shape now than ever before,” Tom said. “Well, if you’re ready we’ll have breakfast.”

The meal was served by Koku with as much unconcern as though they were in the Swift homestead back in Shopton, instead of floating near the clouds. And while it was being eaten in the main cabin, and while the crew was having breakfast in their quarters, the aerial warship was moving along over the ocean in charge of George Watson, one of Tom’s engineers, who was stationed in the forward pilot-house.

“So you’re going to give the guns a real test this time, is that it, Tom?” asked Ned, as he pushed back his plate, a signal that he had eaten enough.

“That’s about it.”

“But don’t you think it’s a bit risky out over the water this way. Supposing something should–should happen?” Ned hesitated.

“You mean we might fall?” asked Tom, with a smile.

“Yes; or turn upside down.”

“Nothing like that could happen. I’m so sure that I have solved the problem of the recoil of the guns that I’m willing to take chances. But if any of you want to get off the Mars while the test is being made, I have a small boat I can lower, and let you row about in that until–“

“No, thank you!” interrupted Mr. Damon, as he looked below. There was quite a heavy swell on, and the ocean did not appear very attractive. They would be much more comfortable in the big Mars.

“I think you won’t have any trouble,” asserted Lieutenant Marbury. “I believe Tom Swift has the right idea about the guns, and there will be so small a shock from the recoil that it will not be noticeable.”

“We’ll soon know,” spoke Tom. “I’m going to get ready for the test now.

They were now well out from shore, over the Atlantic, but to make certain no ships would be endangered by the projectiles, Tom and the others searched the waters to the horizon with powerful glasses. Nothing was seen and the work of loading the guns was begun. The bomb tubes, in the main cabin, were also to be given a test.

As service charges were to be used, and as the projectiles were filled with explosives, great care was needed in handling them.

“We’ll try dropping bombs first,” Tom suggested. “We know they will work, and that will be so much out of the way.

To make the test a severe one, small floating targets were first dropped overboard from the Mars. Then the aerial warship, circling about, came on toward them. Tom, seated at the range- finders, pressed the button that released the shells containing the explosives. One after another they dropped into the sea, exploding as they fell, and sending up a great column of salt water.

“Every one a hit!” reported Lieutenant Marbury, who was keeping “score.”

“That’s good,” responded Tom. “But the others won’t be so easy. We have nothing to shoot at.”

They had to fire the other guns without targets at which to aim. But, after all, it was the absence of recoil they wanted to establish, and this could be done without shooting at any particular object.

One after another the guns were loaded. As has been explained, they were now made double, one barrel carrying the projectile, and the other a charge of water.

“Are you ready?” asked Tom, when it was time to fire. Lieutenant Marbury, Ned and Mr. Damon were helping, by being stationed at the pressure gauges to note the results.

“All ready,” answered Ned.

“Do you think we’d better put on life preservers, Tom?” asked Mr. Damon.

“Nonsense! What for?”

“In case–in case anything happens.”

“Nothing will happen. Look out now, I’m going to fire.”

The guns were to be fired simultaneously by means of an electric current, when Tom pressed a button.

“Here they go!” exclaimed the young inventor.

There was a moment of waiting, and then came a thundering roar. The Mars trembled, but she did not shift to either side from an even keel. From one barrel of the guns shot out the explosive projectiles, and from the other spurted a jet of water, sent out by a charge of powder, equal in weight to that which forced out the shot.

As the projectile was fired in one direction, and the water in one directly opposite, the two discharges neutralized one another.

Out flew the pointed steel shells, to fall harmlessly into the sea, where they exploded, sending up columns of water.

“Well!” cried Tom as the echoes died away. “How was it?”

“Couldn’t have been better,” declared Lieutenant Marbury. “There wasn’t the least shock of recoil. Tom Swift, you have solved the problem, I do believe! Your aerial warship is a success!”

“I’m glad to hear you say so. There are one or two little things that need changing, but I really think I have about what the United States Government wants.”

“I am, also, of that belief, Tom. If only–” The officer stopped suddenly.

“Well?” asked Tom suggestively.

“I was going to say if only those foreign spies don’t make trouble.”

“I think we’ve seen the last of them,” Tom declared. “Now we’ll go on with the tests.”

More guns were fired, singly and in batteries, and in each case the Mars stood the test perfectly. The double barrel had solved the recoil problem.

For some little time longer they remained out over the sea, going through some evolutions to test the rudder control, and then as their present object had been accomplished Tom gave orders to head back to Shopton, which place was reached in due time.

“Well, Tom, how was it?” asked Mr. Swift, for though his son had said nothing to his friends about the prospective test, the aged inventor knew about it.

“Successful, Dad, in every particular.”

“That’s good. I didn’t think you could do it. But you did. I tell you it isn’t much that can get the best of a Swift!” exclaimed the aged man proudly. “Oh, by the way, Tom, here’s a telegram that came while you were gone,” and he handed his son the yellow envelope.

Tom ripped it open with a single gesture, and in a flash his eyes took in the words. He read:

“Look out for spies during trial flights.”

The message was signed with a name Tom did not recognize.

“Any bad news?” asked Mr. Swift.

“No–oh, no,” replied Tom, as he crumpled up the paper and thrust it into his pocket. “No bad news, Dad.”

“Well, I’m glad to hear that,” went on Mr. Swift. “I don’t like telegrams.”

When Tom showed the message to Lieutenant Marbury, that official, after one glance at the signature, said:

“Pierson, eh? Well, when he sends out a warning it generally means something.”

“Who’s Pierson?” asked Tom.

“Head of the Secret Service department that has charge of this airship matter. There must be something in the wind, Tom.”

Extra precautions were taken about the shops. Strangers were not permitted to enter, and all future work on the Mars was kept secret. Nevertheless, Tom was worried. He did not want his work to be spoiled just when it was about to be a success. For that it was a success, Lieutenant Marbury assured him. The government man said he would have no hesitation in recommending the purchase of Tom’s aerial warship.

“There’s just one other test I want to see made,” he said.

“What is that?” Tom inquired.

“In a storm. You know we can’t always count on haying good weather, and I’d like to see how she behaves in a gale.”

“You shall!” declared the young inventor.

For the next week, during which finishing touches were put on the big craft, Tom anxiously waited for signs of a storm. At last they came. Danger signals were put up all along the coast, and warnings were sent out broadcast by the Weather Bureau at Washington.

One dull gray morning Tom roused his friends early and announced that the Mars was going up.

“A big storm is headed this way,” Tom said, “and we’ll have a chance to see how she behaves in it.”

And even as the flight began, the forerunning wind and rain came in a gust of fury. Into the midst of it shot the big aerial warship, with her powerful propellers beating the moisture-laden air.

CHAPTER XIX
QUEER HAPPENINGS

“Say, Tom, are you sure you’re all right?”

“Of course I am! What do you mean?”

It was Ned Newton who asked the question, and Tom Swift who answered it. The chums were in the pilot-house of the dipping, swaying Mars, which was nosing her way into the storm, fighting on an upward slant, trying, if possible, to get above the area of atmospheric disturbance.

“Well, I mean are you sure your craft will stand all this straining, pulling and hauling?” went on Ned, as he clung to a brass hand rail, built in the side of the pilot-house wall for the very purpose to which it was now being put.

“If she doesn’t stand it she’s no good!” cried Tom, as he clung to the steering wheel, which was nearly torn from his hands by the deflections of the rudders.

“Well, it’s taking a big chance, it seems to me,” went on Ned, as he peered through the rain-spotted bull’s-eyes of the pilot- house.

“There’s no danger,” declared Tom. “I wanted to give the ship the hardest test possible before I formally offered her to the government. If she can’t stand a blow like this she isn’t what I thought her, and I’ll have to build another. But I’m sure she will stand the racket, Ned. She’s built strongly, and even if part of the gas bag is carried away, as it was when our propeller shattered, we can still sail. If you think this is anything, wait until we turn about and begin to fight our way against the wind.”

“Are you going to do that, Tom?”

“I certainly am. We’re going with the gale now, to see what is the highest rate of speed we can attain. Pretty soon I’m going to turn her around, and see if she can make any headway in the other direction. Of course I know she won’t make much, if any speed, against the gale; but I must give her that test.”

“Well, Tom, you know best, of course,” admitted Ned. “But to me it seems like taking a big risk.”

And indeed it did seem, not only to Ned, but to some of the experienced men of Tom’s crew, that the young inventor was taking more chances than ever before, and Tom, as my old readers well know, had, in his career, taken some big ones.

The storm grew worse as the day progressed, until it was a veritable hurricane of wind and rain. The warnings of the Weather Bureau had not been exaggerated. But through the fierce blow the Mars fought her way. As Tom had said, she was going with the wind. This was comparatively easy. But what would happen when she headed into the storm?

Mr. Damon, in the main cabin, sat and looked at Lieutenant Marbury, the eccentric man now and then blessing something as he happened to think of it.

“Do you–do you think we are in any danger?” he finally asked.

“Not at present,” replied the government expert.

“You mean we will be–later?”

“It’s hard to say. I guess Tom Swift knows his business, though.”

“Bless my accident insurance policy!” murmured Mr. Damon. “I wish I had stayed home. If my wife ever hears of this–” He did not seem able to finish the sentence.

In the engine-room the crew were busy over the various machines. Some of the apparatus was being strained to keep the ship on her course in the powerful wind, and would be under a worse stress when Tom turned his craft about. But, so far, nothing had given way, and everything was working smoothly.

As hour succeeded hour and nothing happened, the timid ones aboard began to take more courage. Tom never for a moment lost heart. He knew what his craft could do, and he had taken her up in a terrific storm with a definite purpose in view. He was the calmest person aboard, with the exception, perhaps, of Koku. The giant did not seem to know what fear was. He depended entirely on Tom, and as long as his young master had charge of matters the giant was content to obey orders.

There was to be no test of the guns this time. They had worked sufficiently well, and, if need be, could have been fired in the gale. But Tom did not want his men to take unnecessary risks, nor was he foolhardy himself.

“We’ll have our hands full when we turn around and head into the wind,” he said to his chum. “That will be enough.”

“Then you’re really going to give the Mars that test?”

“I surely am. I don’t want any comebacks from Uncle Sam after he accepts my aerial warship. I’ve guaranteed that she’ll stand up and make headway against a gale, and I’m going to prove it”

Lieutenant Marbury was told of the coming trial, and he prepared to take official note of it. While matters were being gotten in readiness Tom turned the wheel over to his assistant pilot and went to the engine-room to see that everything was in good shape to cope with any emergency. The rudders had been carefully examined before the flight was made, to make sure they would not fail, for on them depended the progress of the ship against the powerful wind.

“I rather guess those foreign spies have given up trying to do Tom an injury,” remarked Ned to the lieutenant as they sat in the main cabin, listening to the howl of the wind, and the dash of the rain.

“Well, I certainly hope so,” was the answer. “But I wouldn’t be too sure. The folks in Washington evidently think something is likely to happen, or they wouldn’t have sent that warning telegram.”

“But we haven’t seen anything of the spies,” Ned remarked.

“No, but that isn’t any sign they are not getting ready to make trouble. This may be the calm before the storm. Tom must still be on the lookout. It isn’t as though his inventions alone were in danger, for they would not hesitate to inflict serious personal injury if their plans were thwarted.”

“They must be desperate.”

“They are. But here comes Tom now. He looks as though something new was about to happen.”

“Take care of yourselves now,” advised the young aero-inventor, as he entered the cabin, finding it hard work to close the door against the terrific wind pressure.

“Why?” asked Ned.

“Because we are going to turn around and fight our way back against the gale. We may be turned topsy-turvy for a second or two.”

“Bless my shoe-horn!” cried Mr. Damon. “Do you mean upside down, Tom?”

“No, not that exactly. But watch out!”

Tom went forward to the pilot-house, followed by Ned and the lieutenant. The latter wanted to take official note of what happened. Tom relieved the man at the wheel, and gradually began to alter the direction of the craft.

At first no change was noticeable. So strong was the force of the wind that it seemed as though the Mars was going in the same direction. But Ned, noticing a direction compass on the wall, saw that the needle was gradually shifting.

“Hold fast!” cried Tom suddenly. Then with a quick shift of the rudder something happened. It seemed as though the Mars was trying to turn over, and slide along on her side, or as if she wanted to turn about and scud before the gale, instead of facing it. But Tom held her to the reverse course.

“Can you get her around?” cried the lieutenant above the roar of the gale.

“I–I’m going to!” muttered Tom through his set teeth.

Inch by inch he fought the big craft through the storm. Inch by inch the indicator showed the turning, until at last the grip of the gale was overcome.

“Now she’s headed right into it!” cried Tom in exultation. “She’s nosing right into it!”

And the Mars was. There was no doubt of it. She had succeeded, under Tom’s direction, in changing squarely about, and was now going against the wind, instead of with it.

“But we can’t expect to make much speed,” Tom said, as he signaled for more power, for he had lowered it somewhat in making the turn.

But Tom himself scarcely had reckoned on the force of his craft, for as the propellers whirled more rapidly the aerial warship did begin to make headway, and that in the teeth of a terrific wind.

“She’s doing it, Tom! She’s doing it!” cried Ned exultingly.

“I believe she is,” agreed the lieutenant.

“Well, so much the better,” Tom said, trying to be calm. “If she can keep this up a little while I’ll give her a rest and we’ll go up above the storm area, and beat back home.”

The Mars, so far, had met every test. Tom had decided on ten minutes more of gale-fighting, when from the tube that communicated with the engine-room came a shrill whistle.

“See what that is, Ned,” Tom directed.

“Yes,” called Ned into the mouthpiece. “What’s the matter?”

“Short circuit in the big motor,” was the reply. “We’ve got to run on storage battery. Send Tom back here! Something queer has happened!”

CHAPTER XX
THE STOWAWAYS

Ned repeated the message breathlessly.

“Short circuit!” gasped Tom. “Run on storage battery! I’ll have to see to that. Take the wheel somebody!”

“Wouldn’t it be better to turn about, and run before the wind, so as not to put too great a strain on the machinery?” asked Lieutenant Marbury.

“Perhaps,” agreed Tom. “Hold her this way, though, until I see what’s wrong!”

Ned and the government man took the wheel, while Tom hurried along the runway leading from the pilot-house to the machinery cabin. The gale was still blowing fiercely.

The young inventor cast a hasty look about the interior of the place as he entered. He sniffed the air suspiciously, and was aware of the odor of burning insulation.

“What happened?” he asked, noting that already the principal motive power was coming from the big storage battery. The shift had been made automatically, when the main motor gave out.

“It’s hard to say,” was the answer of the chief engineer. “We were running along all right, and we got your word to switch on more power, after the turn. We did that all right, and she was running as smooth as a sewing-machine, when, all of a sudden, she short-circuited, and the storage battery cut in automatically.”

“Think you put too heavy a load on the motor?” Tom asked.

“Couldn’t have been that. The shunt box would have taken that up, and the circuit-breaker would have worked, saving us a burn- out, and that’s what happened-a burn-out. The motor will have to be rewound.”

“Well, no use trying to fight this gale with the storage battery,” Tom said, after a moment’s thought. “We’ll run before it. That’s the easiest way. Then we’ll try to rise above the wind.”

He sent the necessary message to the pilot-house. A moment later the shift was made, and once more the Mars was scudding before the storm. Then Tom gave his serious attention to what had happened in the engine room.

As he bent over the burned-out motor, looking at the big shiny connections, he saw something that startled him. With a quick motion Tom Swift picked up a bar of copper. It was hot to the touch–so hot that he dropped it with a cry of pain, though he had let go so quickly that the burn was only momentary.

“What’s the matter?” asked Jerry Mound, Tom’s engineer.

“Matter!” cried Tom. “A whole lot is the matter! That copper bar is what made the short circuit. It’s hot yet from the electric current. How did it fall on the motor connections?”

The engine room force gathered about the young inventor. No one could explain how the copper bar came to be where it was. Certainly no one of Tom’s employees had put it there, and it could not have fallen by accident, for the motor connections were protected by a mesh of wire, and a hand would have to be thrust under them to put the bar in place. Tom gave a quick look at his men. He knew he could trust them–every one. But this was a queer happening.

For a moment Tom did not know what to think, and then, as the memory of that warning telegram came to him, he had an idea.

“Were any strangers in this cabin before the start was made?” he asked Mr. Mound.

“Not that I know of,” was the answer.

“Well, there may be some here now,” Tom said grimly. “Look about.”

But a careful search revealed no one. Yet the young inventor was sure the bar of copper, which had done the mischief of short-circuiting the motor, had been put in place deliberately.

In reality there was no danger to the craft, since there was power enough in the storage battery to run it for several hours. But the happening showed Tom he had still to reckon with his enemies.

He looked at the height gauge on the wall of the motor-room, and noted that the Mars was going up. In accordance with Tom’s instructions they were sending her above the storm area. Once there, with no gale to fight, they could easily beat their way back to a point above Shopton, and make the best descent possible.

And that was done while, under Tom’s direction, his men took the damaged motor apart, with a view to repairing it.

“What was it, Tom?” asked Ned, coming back to join his chum, after George Ventor, the assistant pilot, had taken charge of the wheel.

“I don’t exactly know, Ned,” was the answer. “But I feel certain that some of my enemies came aboard here and worked this mischief.”

“Your enemies came aboard?”

“Yes, and they must be here now. The placing of that copper bar proves it.”

“Then let’s make a search and find them, Tom. It must be some of those foreign spies.”

“Just what I think.”

But a more careful search of the craft than the one Tom had casually made revealed the presence of no one. All the crew and helpers were accounted for, and, as they had been in Tom’s service for some time, they were beyond suspicion. Yet the fact remained that a seemingly human agency had acted to put the main motor out of commission. Tom could not understand it.

“Well, it sure is queer,” observed Ned, as the search came to nothing.

“It’s worse than queer,” declared Tom, “it’s alarming! I don’t know when I’ll be safe if we have ghosts aboard.”

“Ghosts?” repeated Ned.

“Well, when we can’t find out who put that bar in place I might as well admit it was a ghost,” spoke Tom. “Certainly, if it was done by a man, he didn’t jump overboard after doing it, and he isn’t here now. It sure is queer!”

Ned agreed with the last statement, at any rate.

In due time the Mars, having fought her way above the storm, came over Shopton, and then, the wind having somewhat died out, she fought her way down, and, after no little trouble, was housed in the hangar.

Tom cautioned his friends and workmen to say nothing to his father about the mysterious happening on board.

“I’ll just tell him we had a slight accident, and let it go at that,” Tom decided. “No use in causing him worry.”

“But what are you going to do about it?” asked Ned.

“I’m going to keep careful watch over the aerial warship, at any rate,” declared Tom. “If there’s a hidden enemy aboard, I’ll starve him out.”

Accordingly, a guard, under the direction of Koku, was posted about the big shed, but nothing came of it. No stranger was observed to sneak out of the ship, after it had been deserted by the crew. The mystery seemed deeper than ever.

It took nearly a week to repair the big motor, and, during this time, Tom put some improvements on the airship, and added the finishing touches.

He was getting it ready for the final government test, for the authorities in Washington had sent word that they would have Captain Warner, in addition to Lieutenant Marbury, make the final inspection and write a report.

Meanwhile several little things occurred to annoy Tom. He was besieged with applications from new men who wanted to work, and many of these men seemed to be foreigners. Tom was sure they were either spies of some European nations, or the agents of spies, and they got no further than the outer gate.

But some strangers did manage to sneak into the works, though they were quickly detected and sent about their business. Also, once or twice, small fires were discovered in outbuildings, but they were soon extinguished with little damage. Extra vigilance was the watchword.

“And yet, with all my precautions, they may get me, or damage something,” declared Tom. “It is very annoying!”

“It is,” agreed Ned, “and we must be doubly on the lookout.”

So impressed was Ned with the necessity for caution that he arranged to take his vacation at this time, so as to be on hand to help his chum, if necessary.

The Mars was nearing completion. The repaired motor was better than ever, and everything was in shape for the final test. Mr. Damon was persuaded to go along, and Koku was to be taken, as well as the two government officials.

The night before the trip the guards about the airship shed were doubled, and Tom made two visits to the place before midnight. But there was no alarm.

Consequently, when the Mars started off on her final test, it was thought that all danger from the spies was over.

“She certainly is a beauty,” said Captain Warner, as the big craft shot upward. “I shall be interested in seeing how she stands gun fire, though.”

“Oh, she’ll stand it,” declared Lieutenant Marbury. The trip was to consume several days of continuous flying, to test the engines. A large supply of food and ammunition was aboard.

It was after supper of the first day out, and our friends were seated in the main cabin laying out a program for the next day, when sudden yells came from a part of the motor cabin devoted to storage. Koku, who had been sent to get out a barrel of oil, was heard to shout.

“What’s up?” asked Tom, starting to his feet. He was answered almost at once by more yells.

“Oh, Master! Come quickly!” cried the giant. “There are many men here. There are stowaways aboard!”

CHAPTER XXI
PRISONERS

For a moment, after hearing Koku’s reply. neither Tom nor his friends spoke. Then Ned, in a dazed sort of way, repeated:

“Stowaways!”

“Bless my–” began Mr. Damon, but that was as far as he got.

From the engine compartment, back of the amidship cabin, came a sound of cries and heavy blows. The yells of Koku could be heard above those of the others.

Then the door of the cabin where Tom Swift and his friends were was suddenly burst open, and seven or eight men threw themselves within. They were led by a man with a small, dark mustache and a little tuft of whiskers on his chin–an imperial. He looked the typical Frenchman, and his words, snapped out, bore out that belief.

What he said was in French, as Tom understood, though he knew little of that language. Also, what the Frenchman said produced an immediate result, for the men following him sprang at our friends with overwhelming fierceness.

Before Tom, Ned, Captain Warner, Mr. Damon or Lieutenant Marbury could grasp any weapon with which to defend themselves, had their intentions been to do so, they were seized.

Against such odds little could be done, though our friends did not give up without a struggle.

“What does this mean?” angrily demanded Tom Swift. “Who are you? What are you doing aboard my craft? Who are–“

His words were lost in smothered tones, for one of his assailants put a heavy cloth over his mouth, and tied it there, gagging him. Another man, with a quick motion, whipped a rope about Tom’s hands and feet, and he was soon securely bound.

In like manner the others were treated, and, despite the struggles of Mr. Damon, the two government men and Ned, they were soon put in a position where they could do nothing–helplessly bound, and laid on a bench in the main cabin, staring blankly up at the ceiling. Each one was gagged so effectively that he could not utter more than a faint moan.

Of the riot of thoughts that ran through the heads of each one, I leave you to imagine.

What did it all mean? Where had the strange men come from? What did they mean by thus assaulting Tom and his companions? And what had happened to the others of the crew–Koku, Jerry Mound, the engineer, and George Ventor, the assistant pilot?

These were only a few of the questions Tom asked himself, as he lay there, bound and helpless. Doubtless Mr. Damon and the others were asking themselves similar questions.

One thing was certain–whatever the stowaways, as Koku had called them, had done, they had not neglected the Mars, for she was running along at about the same speed, though in what direction Tom could not tell. He strained to get a view of the compass on the forward wall of the cabin, but he could not see it.

It had been a rough-and-tumble fight, by which our friends were made prisoners, but no one seemed to have been seriously, or even slightly, hurt. The invaders, under the leadership of the Frenchman, were rather ruffled, but that was all.

Pantingly they stood in line, surveying their captives, while the man with the mustache and imperial smiled in a rather superior fashion at the row of bound ones. He spoke in his own tongue to the men, who, with the exception of one, filed out, going, as Tom and the others could note, to the engine-room in the rear.

“I hope I have not had to hurt any of you,” the Frenchman observed, with sarcastic politeness. “I regret the necessity that caused me to do this, but, believe me, it was unavoidable.”

He spoke with some accent, and Tom at once decided this was the same man who had once approached Eradicate. He also recognized him as the man he had seen in the woods the day of the outing.

“He’s one of the foreign spies,” thought Tom “and he’s got us and the ship, too. They were too many for us!”

Tom’s anxiety to speak, to hold some converse with the captor, was so obvious that the Frenchman said:

“I am going to treat you as well as I can under the circumstances. You and your other friends, who are also made prisoners, will be allowed to be together, and then you can talk to your hearts’ content.”

The other man, who had remained with the evident ringleader of the stowaways, asked a question, in French, and he used the name La Foy.

“Ah!” thought Tom. “This is the leader of the gang that attacked Koku in the shop that night. They have been waiting their chance, and now they have made good. But where did they come from? Could they have boarded us from some other airship?”

Yet, as Tom asked himself that question, he knew it could hardly have been possible. The men must have been in hiding on his own craft, they must have been, as Koku had cried out– stowaways–and have come out at a preconcerted signal to overpower the aviators.

“If you will but have patience a little longer,” went on La Foy, for that was evidently the name of the leader, “you will all be together. We are just considering where best to put you so that you will not suffer too much. It is quite a problem to deal with so many prisoners, but we have no choice.”

The two Frenchmen conversed rapidly in their own language for a few minutes, and then there came into the cabin another of the men who had helped overpower Tom and his friends. What he told La Foy seemed to give that individual satisfaction, for he smiled.

“We are going to put you all together in the largest storeroom, which is partly empty,” La Foy said. “There you will be given food and drink, and treated as well as possible under the circumstances. You will also be unbound, and may converse among yourselves. I need hardly point out,” he went on, “that calling for help will be useless. We are a mile or so in the air, and have no intention of descending,” and he smiled mockingly.

“They must know how to navigate my aerial warship,” thought Tom. “I wonder what their game is, anyhow?”

Night had fallen, but the cabin was aglow with electric lights. The foreigners in charge of the Mars seemed to know their way about perfectly, and how to manage the big craft. By the vibration Tom could tell that the motor was running evenly and well.

“But what happened to the others–to Mound, Ventor and Koku?” wondered Tom.

A moment later several of the foreigners entered. Some of them did not look at all like Frenchmen, and Tom was sure one was a German and another a Russian.

“This will be your prison–for a while,” said La Foy significantly, and Tom wondered how long this would be the case. A sharp thought came to him–how long would they be prisoners? Did not some other, and more terrible, fate await them?

As La Foy spoke, he opened a storeroom door that led off from the main, or amidship, cabin. This room was intended to contain the supplies and stores that would be taken on a long voyage. It was one of two, being the larger, and now contained only a few odds and ends of little importance. It made a strong prison, as Tom well knew, having planned it.

One by one, beginning with Tom, the prisoners were taken up and placed in a recumbent position on the floor of the storeroom. Then were brought in the engineer and assistant pilot, as well as Koku and a machinist whom Tom had brought along to help him. Now the young inventor and all his friends were together. It took four men to carry Koku in, the giant being covered with a network of ropes.

“On second thought,” said La Foy, as he saw Koku being placed with his friends, “I think we will keep the big man with us. We had trouble enough to subdue him. Carry him back to the engine- room.”

So Koku, trussed up like some roped steer, was taken out again.

“Now then,” said La Foy to his prisoners, as he stood in the door of the room, “I will unbind one of you, and he may loose the bonds of the others.”

As he spoke, he took the rope from Tom’s hands, and then, quickly slipping out, locked and barred the door.

CHAPTER XXII
APPREHENSIONS

For a moment or two, after the ropes binding his hands were loosed, Tom Swift did nothing. He was not only stunned mentally, but the bonds had been pulled so tightly about his wrists that the circulation was impeded, and his cramped muscles required a little time in which to respond.

But presently he felt the tingle of the coursing blood, and he found he could move his arms. He raised them to his head, and then his first care was to remove the pad of cloth that formed a gag over his mouth. Now he could talk.

“I–I’ll loosen you all in lust a second,” he said, as he bent over to pick at the knot of the rope around his legs. His own voice sounded strange to him.

“I don’t know what it’s all about, any more than you do,” he went on, speaking to the others. “It’s a fierce game we’re up against, and we’ve got to make the best of it. As soon as we can move, and talk, we’ll decide what’s best to do. Whoever these fellows are, and I believe they are the foreign spies I’ve been warned about, they are in complete possession of the airship.”

Tom found it no easy matter to loosen the bonds on his feet. The ropes were well tied, and Tom’s fingers were stiff from the lack of circulation of blood. But finally he managed to free himself. When he stood up in the dim storeroom, that was now a prison for all save Koku, he found that he could not walk. He almost toppled over, so weak were his legs from the tightness of the ropes. He sat down and worked his muscles until they felt normal again.

A few minutes later, weak and rather tottery, he managed to reach Mr. Damon, whom he first unbound. He realized that Mr. Damon was the oldest of his friends, and, consequently, would suffer most. And it was characteristic of the eccentric gentleman that, as soon as his gag was removed he burst out with:

“Bless my wristlets, Tom! What does it all mean?”

“That’s more than I can say, Mr. Damon,” replied Tom, with a mournful shake of his head. “I’m very sorry it happened, for it looks as though I hadn’t taken proper care. The idea of those men stowing themselves away on board here, and me not knowing it; and then coming out unexpectedly and getting possession of the craft! It doesn’t speak very well for my smartness.”

“Oh, well, Tom, anyone might have been fooled by those plotting foreigners,” said Mr. Damon. “Now, we’ll try to turn matters about and get the best of them. Oh, but it feels good to be free once more!”

He stretched his benumbed and stiffened limbs and then helped Tom free the others. They stood up, looking at each other in their dimly lighted prison.

“Well, if this isn’t the limit I don’t know what is!” cried Ned Newton.

“They got the best of you, Tom,” spoke Lieutenant Marbury.

“Are they really foreign spies?” asked Captain Warner.

“Yes,” replied his assistant. “They managed to carry out the plot we tried to frustrate. It was a good trick, too, hiding on board, and coming out with a rush.”

“Is that what they did?” asked Mr. Damon.

“It looks so,” observed Tom. “The attack must have started in the engine-room,” he went on, with a look at Mound and Ventor. “What happened there?” he asked.

“Well, that’s about the way it was,” answered the engineer. “We were working away, making some adjustments, oiling the parts and seeing that everything was running smoothly, when, all at once, I heard Koku yell. He had gone in the oil room. At first I thought something had gone wrong with the ship, but, when I looked at the giant, I saw he was being attacked by four strange men. And, before I, or any of the other men, could do anything, they all swarmed down on us.

“There must have been a dozen of them, and they simply overwhelmed us. One of them hit Koku on the head with an iron bar, and that took all the fight out of the giant, or the story might have been a different one. As it was, we were overpowered, and that’s all I know until we were carried in here, and saw you folks all tied up as we were.”

“They burst in on us in the same way,” Tom explained. “But where did they come from? Where were they hiding?”

“In the oil and gasoline storeroom that opens out of the motor compartment,” answered Mound, the engineer. “It isn’t half full, you know, and there’s room for more than a dozen men in it. They must have gone in some time last night, when the airship was in the hangar, and remained hidden among the boxes and barrels until they got ready to come out and overpower us.”

“That’s it,” decided Tom. “But I don’t understand how they got in. The hangar was well guarded all night.”

“Some of your men might have been bribed,” suggested Ned.

“Yes, that is so,” admitted Tom, and, later, he learned that such had been the case. The foreign spies, for such they were, had managed to corrupt one of Tom’s trusted employees, who had looked the other way when La Foy and his fellow-conspirators sneaked into the airship shed and secreted themselves.

“Well, discussing how they got on board isn’t going to do us any good now,” Tom remarked ruefully. “The question is–what are we going to do?”

“Bless my fountain pen!” cried Mr. Damon. “There’s only one thing to do!”

“What is that?” asked Ned.

“Why, get out of here, call a policeman, and have these scoundrels arrested. I’ll prosecute them! I’ll have my lawyer on hand to see that they get the longest terms the statutes call for! Bless my pocketbook, but I will!” and Mr. Damon waxed quite indignant.

“That’s easier said than done,” observed Torn Swift, quietly. “In the first place, it isn’t going to be an easy matter to get out of here.”

He looked around the storeroom, which was then their prison. It was illuminated by a single electric light, which showed some boxes and barrels piled in the rear.

“Nothing in them to help us get out,” Tom went on, for he knew what the contents were.

“Oh, we’ll get out,” declared Ned confidently, “but I don’t believe we’ll find a policeman ready to take our complaint. The upper air isn’t very well patrolled as yet.”

“That’s so,” agreed Mr. Damon. “I forgot that we were in an airship. But what is to he done, Tom? We really are captives aboard our own craft.”

“Yes, worse luck,” returned the young inventor. “I feel foolish when I think how we let them take us prisoners.”

“We couldn’t help it,” Ned commented. “They came on us too suddenly. We didn’t have a chance. And they outnumbered us two to one. If they could take care of big Koku, what chance did we have?”

“Very little,” said Engineer Mound. “They were desperate fellows. They know something about aircraft, too. For, as soon as Koku, Ventor and I were disposed of, some of them went at the machinery as if they had been used to running it all their lives.”

“Oh, the foreigners are experts when it comes to craft of the air,” said Captain Warner.

“Well, they seem to be running her, all right,” admitted the young inventor, “and at good speed, too. They have increased our running rate, if I am any judge.”

“By several miles an hour,” confirmed the assistant pilot. “Though in which direction they are heading, and what they are going to do with us is more than I can guess.”

“That’s so!” agreed Mr. Damon. “What is to become of us? They may heave us overboard into the ocean!”

“Into the ocean!” cried Ned apprehensively. “Are we near the sea?”

“We must be, by this time,” spoke Tom. “We were headed in that direction, and we have come almost far enough to put us somewhere over the Atlantic, off the Jersey coast.”

A look of apprehension was on the faces of all. But Tom’s face did not remain clouded long.

“We won’t try to swim until we have to,” he said. “Now, let’s take an account of stock, and see if we have any means of getting out of this prison.

CHAPTER XXIII
ACROSS THE SEA

With one accord the hands of the captives sought their pockets. Probably the first thought of each one was a knife–a pocket knife. But blank looks succeeded their first hopeful ones, for the hands came out empty.

“Not a thing!” exclaimed Mr. Damon. “Not a blessed thing! They have even taken my keys and–my fountain pen!”

“I guess they searched us all while they were struggling with us, tying us up,” suggested Ned. “I had a knife with a big, strong blade, but it’s gone.

“So is mine,” echoed Tom.

“And I haven’t even a screwdriver, or a pocket-wrench,” declared the engineer, “though I had both.”

“They evidently knew what they were doing,” said Lieutenant Marbury. “I don’t usually carry a revolver, but of late I have had a small automatic in my pocket. That’s gone, too.”

“And so are all my things,” went on his naval friend. “That Frenchman, La Foy, was taking no chances.”

“Well,” if we haven’t any weapons, or means of getting out of here, we must make them,” said Tom, as hopefully as he could under the circumstances. “I don’t know all the things that were put in this storeroom, and perhaps there may be something we can use.”

“Shall we make the try now?” asked Ned. “I’m getting thirsty, at least. Lucky we had supper before they came out at us.”

“Well, there isn’t any water in here, or anything to eat, of so much I am sure,” went on Tom “So we will have to depend on our captors for that.”

“At least we can shout and ask for water,” said Lieutenant Marbury. “They have no excuse for being needlessly cruel.”

They all agreed that this might not be a bad plan, and were preparing to raise a united shout, when there came a knock on the door of their prison.

“Are you willing to listen to reason?” asked a voice they recognized as that of La Foy.

“What do you mean by reason?” asked Tom bitterly. “You have no right to impose any conditions on us.”

“I have the right of might, and I intend exercising it,” was the sharp rejoinder. “If you will listen to reason–“

“Which kind–yours or ours?” asked Tom pointedly.

“Mine, in this case,” snapped back the Frenchman. “What I was going to say was that I do not intend to starve you, or cause you discomfort by thirst. I am going to open the door and put in food and water. But I warn you that any attempt to escape will be met with severe measures.

“We are in sufficient force to cope with you. I think you have seen that.” He spoke calmly and in perfect English, though with a marked accent. “My men are armed, and will stand here ready to meet violence with violence,” he went on. “Is that understood?”

For a moment none of the captives replied.

“I think it will be better to give in to him at least for a while,” said Captain Warner in a low voice to Tom. “We need water, and will soon need food. We can think and plan better if we are well nourished.”

“Then you think I should promise not to raise a row?”

“For the time being–yes.”

“Well, I am waiting!” came in sharp tones from the other side of the portal.

“Our answer is–yes,” spoke Tom. “We will not try to get out– just yet,” he added significantly.

A key was heard grating in the lock, and, a moment later, the door slid back. Through the opening could be seen La Foy and some of his men standing armed. Others had packages of food and jugs of water. A plentiful supply of the latter was carried aboard the Mars.

“Keep back from the door!” was the stern command of La Foy. “The food and drink will be passed in only if you keep away from the entrance. Remember my men are armed!”

The warning was hardly needed, for the weapons could plainly be seen. Tom had half a notion that perhaps a concerted rush would carry the day for him and his friends, but he was forced to abandon that idea.

While the guards looked on, others of the “pirate crew,” as Ned dubbed them, passed in food and water. Then the door was locked again.

They all felt better after drinking the water, which was made cool by evaporation, for the airship was quite high above the earth when Tom’s enemies captured it, and the young inventor felt sure it had not descended any.

No one felt much like eating, however, so the food was put away for a time. And then, somewhat refreshed, they began looking about for some means of getting out of their prison.

“Of course we might batter down the door, in time, by using some of these boxes as rams,” said Tom. “But the trouble is, that would make a noise, and they could stand outside and drive us back with guns and pistols, of which they seem to have plenty.”

“Yes, and they could turn some of your own quick-firers on us,” added Captain Warner. “No, we must work quietly, I think, and take them unawares, as they took us. That is our only plan.”

“We will be better able to see what we have here by daylight,” Tom said. “Suppose we wait until morning?”

That plan was deemed best, and preparations made for spending the night in their prison.

It was a most uncomfortable night for all of them. The floor was their only bed, and their only covering some empty bags that had contained supplies. But even under these circumstances they managed to doze off fitfully.

Once they were all awakened by a violent plunging of the airship. The craft seemed to be trying to stand on her head, and then she rocked violently from side to side, nearly turning turtle. “What is it?” gasped Ned, who was lying next to Tom.

“They must be trying some violent stunts,” replied the young inventor, “or else we have run into a storm.”

“I think the latter is the case,” observed Lieutenant Marbury.

And, as the motion of the craft kept up, though less violently, this was accepted as the explanation. Through the night the Mars flew, but whither the captives knew not.

The first gray streaks of dawn finally shone through the only window of their prison. Sore, lame and stiff, wearied in body and disturbed in mind, the captives awoke. Tom’s first move was toward the window. It was high up, but, by standing on a box, he could look through it. He uttered an exclamation.

“What is it?” asked Ned, swaying to and fro from the violent motion ef the aerial warship.

“We are away out over the sea,” spoke Tom, “and in the midst of a bad storm.”

CHAPTER XXIV
THE LIGHTNING BOLT

Tom turned away from the window, to find his companions regarding him anxiously.

“A storm,” repeated Ned. “What sort?”

“It might turn into any sort,” replied Tom. “All I can see now is a lot of black clouds, and the wind must be blowing pretty hard, for there’s quite a sea on.”

“Bless my galvanometer!” cried Mr. Damon. “Then we are out over the ocean again, Tom?”

“Yes, there’s no doubt of it.”

“What part?” asked the assistant pilot.

“That’s more than I can tell,” Tom answered.

“Suppose I take a look?” suggested Captain Warner. “I’ve done quite a bit of sailing in my time.”

But, when he had taken a look through the window at which Tom had been standing, the naval officer descended, shaking his head.

“There isn’t a landmark in sight,” he announced. “We might be over the middle of the Atlantic, for all I could tell.”

“Hardly as far as that,” spoke Tom. “They haven’t been pushing the Mars at that speed. But we may be across to the other side before we realize it.”

“How’s that?” asked Ned.

“Well, the ship is in the possession of these foreign spies,” went on Tom. “All their interests are in Europe, though it would be hard to say what nationality is in command here. I think there are even some Englishmen among those who attacked us, as well as French, Germans, Italians and Russians.”

“Yes, it seems to be a combination of European nations against us,” admitted Captain Warner. “Probably, after they have made good their seizure of Tom’s aerial warship, they will portion her out among themselves, or use her as a model from which to make others.”

“Do you think that is their object?” asked Mr. Damon.

“Undoubtedly,” was the captain’s answer. “It has been the object of these foreign spies, all along, not only to prevent the United States from enjoying the benefits of these progressive inventions, but to use them for themselves. They would stop at nothing to gain their ends. It seems we did not sufficiently appreciate their power and daring.”

“Well, they’ve got us, at any rate,” observed Tom, “and they may take us and the ship to some far-off foreign country.”

“If they don’t heave us overboard half-way there,” commented Ned, in rather gloomy tones

“Well, of course, there’s that possibility,” admitted Tom. “They are desperate characters.”

“Well, we must do something,” declared Lieutenant Marbury. “Come, it’s daylight now, and we can see to work better. Let’s see if we can’t find a way to get out of this prison. Say, but this sure is a storm!” he cried, as the airship rolled and pitched violently.

“They are handling her well, though,” observed Tom, as the craft came quickly to an even keel. “Either they have a number of expert birdmen on board, or they can easily adapt themselves to a new aircraft. She is sailing splendidly.”

“Well, let’s eat something, and set to work,” proposed Ned.

They brought out the food which had been given to them the night before, but before they could eat this, there came a knock on the door, and more food and fresh water was handed in, under the same precautions as before.

Tom and his companions indignantly demanded to be released, but their protests were only laughed at, and while the guards stood with ready weapons the door was again shut and locked.

But the prisoners were not the kind to sit idly down in the face of this. Under Tom’s direction they set about looking through their place of captivity for something by which they could release themselves. At first they found nothing, and Ned even suggested trying to cut a way through the wooden walls with a fingernail file, which he found in one of his pockets, when Tom, who had gone to the far end of the storeroom, uttered a cry.

“What is it–a way out?” asked Lieutenant Marbury anxiously.

“No, but means to that end,” Tom replied. “Look, a file and a saw, left here by some of my workmen, perhaps,” and he brought out the tools. He had found them behind a barrel in the far end of the compartment.

“Hurray!” cried Ned. “That’s the ticket! Now we’ll soon show these fellows what’s what!”

“Go easy!” cautioned Tom. “We must work carefully. It won’t do to slam around and try to break down the door with these. I think we had better select a place on the side wall, break through that, and make an opening where we can come out unnoticed. Then, when we are ready, we can take them by surprise. We’ll have to do something like that, for they outnumber us, you know.”

“That is so,” agreed Captain Warner. “We must use strategy.”

“Well, where would be a good place to begin to burrow out?” asked Ned.

“Here,” said Tom, indicating a place far back in the room. “We can work there in turns, sawing a hole through the wall. It will bring us out in the passage between the aft and amidship cabins, and we can go either way.”

“Then let’s begin!” cried Ned enthusiastically, and they set to work.

While the aerial warship pitched and tossed in the storm, over some part of the Atlantic, Tom and his friends took turns in working their way to freedom. With the sharp end of the file a small hole was made, the work being done as slowly as a rat gnaws, so as to make no noise that would be heard by their captors. In time the hole was large enough to admit the end of the saw.

But this took many hours, and it was not until the second day of their captivity that they had the hole nearly large enough for the passage of one person at a time. They had not been discovered, they thought.

Meanwhile they had been given food and water at intervals, but to all demands that they be released, or at least told why they were held prisoners, a deaf ear was turned.

They could only guess at the fate of Koku. Probably the giant was kept bound, for once he got the chance to use his enormous strength it might go hard with the foreigners.

The Mars continued to fly through the air. Sometimes, as Tom and his friends could tell by the motion, she was almost stationary in the upper regions, and again she seemed to be flying at top speed. Occasionally there came the sound of firing.

“They’re trying my guns,” observed Tom grimly.

“Do you suppose they are being attacked?” asked Ned, hopefully.

“Hardly,” replied Captain Warner. “The United States possesses no craft able to cope with this one in aerial warfare, and they are hardly engaging in part of the European war yet. I think they are just trying Tom’s new guns.”

Later our friends learned that such was the case.

The storm had either passed, or the Mars had run out of the path of it, for, after the first few hours of pitching and tossing, the atmosphere seemed reduced to a state of calm.

All the while they were secretly working to gain their freedom so they might attack and overpower their enemies, they took occasional observations from the small window. But they could learn nothing of their whereabouts. They could only view the heaving ocean, far below them, or see a mass of cloud-mist, which hid the earth, if so be that the Mars was sailing over land.

“But how much longer can they keep it up?” asked Ned.

“Well, we have fuel and supplies aboard for nearly two weeks,” Tom answered.

“And by the end of that time we may all be dead,” spoke the young bank clerk despondently.

“No, we’ll be out of here before then!” declared Lieutenant Marbury.

Indeed the hole was now almost large enough to enable them to crawl out one at a time. They could not, of course, see how it looked from the outside, but Tom had selected a place for its cutting so that the sawdust and the mark of the panel that was being removed, would not ordinarily be noticeable.

Their set night as the time for making the attempt–late at night, when it was hoped that most of their captors would be asleep.

Finally the last cut was made, and a piece of wood hung over the opening only by a shred, all ready to knock out.

“We’ll do it at midnight,” announced Tom.

Anxious, indeed, were those last hours of waiting. The time had almost arrived for the attempt, when Tom, who had been nervously pacing to and fro, remarked:

“We must be running into another storm. Feel how she heaves and rolls!”

Indeed the Mars was most unsteady.

“It sure is a storm!” cried Ned, “and a heavy one, too,” for there came a burst of thunder, that seemed like a report of Tom’s giant cannon.

In another instant they were in the midst of a violent thunderstorm, the airship pitching and tossing in a manner to almost throw them from their feet.

As Tom reached up to switch on the electric light again, there came a flash of lightning that well nigh blinded them. And so close after it as to seem simultaneous, there came such a crash of thunder as to stun them all. There was a tingling, as of a thousand pins and needles in the body of each of the captives, and a strong smell of sulphur. Then, as the echoes of the clap died away, Tom yelled:

“She’s been struck! The airship has been struck!”

CHAPTER XXV
FREEDOM

For a moment there was silence, following Tom’s wild cry and the noise of the thunderclap. Then, as other, though less loud reverberations of the storm continued to sound, the captives awoke to a realization of what had happened. They had been partially stunned, and were almost as in a dream.

“Are–are we all right?” stammered Ned.

“Bless my soul! What has happened?” cried Mr. Damon.

“We’ve been struck by lightning!” Tom repeated. “I don’t know whether we’re all right or not.”

“We seem to be falling!” exclaimed Lieutenant Marbury.

“If the whole gas bag isn’t ripped to pieces we’re lucky,” commented Jerry Mound.

Indeed, it was evident that the Mars was sinking rapidly. To all there came the sensation of riding in an elevator in a skyscraper and being dropped a score of stories.

Then, as they stood there in the darkness, illuminated only by flashes from the lightning outside the window, waiting for an unknown fate, Tom Swift uttered a cry of delight.

“We’ve stopped falling!” he cried. “The automatic gas machine is pumping. Part of the gas bag was punctured, but the unbroken compartments hold!”

“If part of the gas leaked out I don’t see why it wasn’t all set on fire and exploded,” observed Captain Warner.

“It’s a non-burnable gas,” Tom quickly explained. “But come on. This may be our very chance. There seems to be something going on that may be in our favor.”

Indeed the captives could hear confused cries and the running to and fro of many feet.

He made for the sawed panel, and, in another instant, had burst out and was through it, out into the passageway between the after and amidship cabins. His companions followed him.

They looked into the rear cabin, or motor compartment, and a scene of confusion met their gaze. Two of the foreign men who had seized the ship lay stretched out on the floor near the humming machinery, which had been left to run itself. A look in the other direction, toward the main cabin, showed a group of the foreign spies bending over the inert body of La Foy, the Frenchman, stretched out on a couch.

“What has happened?” cried Ned. “What does it all mean?,’