Tom Swift acted promptly, for he realized the necessity. The events that had hedged him about since he had begun work on his giant cannon made him suspicious. He did not quite know whom to suspect, nor the reasons for their actions, but he had been on the alert for several days, and was now ready to act.
The instant Ned answered as he did, and warned Tom, the young inventor slid his hand under his pillow and pressed an auxiliary electric switch he had concealed there. In a moment the rooms were flooded with a bright light, and the two lads had a momentary glimpse of an intruder making a dive for the window.
"There he is, Tom!" cried Ned.
"What do you want?" demanded Tom, instinctively. But the intruder did not stay to answer.
Instead, he made a dive for the casement. It was one story above the ground, but this did not cause him any hesitation. It was summer, and the window was open, though a wire mosquito net barred the aperture. This was no hindrance to the man, however.
As Ned and Tom leaped from their beds, Ned catching up the heavy, empty water pitcher as a weapon, and Tom an old Indian war club that served as one of the ornaments of his room, the fellow, with one kick, burst the screen.
Then, clambering out on the sill, he dropped from sight, the boys hearing him land with a thud on the turf below. It was no great leap, though the fall must have jarred him considerably, for the boys heard him grunt, and then groan as if in pain.
"Quick!" cried Ned. "Ring the bell for Koku, Ned. I want to capture this fellow if possible."
"Who is he?" asked Ned.
"I don't know, but we'll see if we can size him up. Signal for the giant!"
There was an electric bell from Tom's room to the apartment of his big servant, and a speaking tube as well. While Ned was pressing the button, and hastily telling the giant what had happened, urging him to get in pursuit of the intruder, Tom had taken from his bureau a powerful, portable, electric flash lamp, of the same variety as that used by the would-be thief. Only Tom's was provided with a tungsten filament, which gave a glaring white pencil of light, increased by reflectors.
And in this glare the young inventor saw, speeding away over the lawn, the form of a big man.
"There he goes, Ned!" he shouted.
"So I see. Koku will be right on the job. I told him not to dress. Can you make out who the fellow is?"
"No, his back is toward us. But he's limping, all right. I guess that jump jarred him up a bit. Where is Koku?"
"There he goes now!" exclaimed Ned, as a figure leaped from the side door of the house—a gigantic figure, scantily clad.
"Get to him, Koku!" cried Tom.
"Me git, Master!" was the reply, and the giant sped on.
"Let's go out and lend a hand!" suggested Ned, looking at the water pitcher as though wondering what he had intended to do with it.
"I'm with you," agreed Tom. "Only I want to get into something a little more substantial than my pajamas."
As the two lads hurriedly slipped on some clothing they heard the voice of Mr. Swift calling:
"What is it, Tom? Has anything happened?"
"Nothing much," was the reassuring answer. "It was a near-happening, only Ned woke up in time. Someone was in our rooms—a burglar, I guess."
"A burglar! Good land a massy!" cried Eradicate, who had also gotten up to see what the excitement was about. "Did you cotch him, Massa Tom?"
"No, Rad; but Koku is after him."
"Koku? Huh, he nebber cotch anybody. I'se got t' git out dere mahse'f! Koku? Hu! I s'pects it's dat no-'count cousin ob mine, arter mah chickens ag'in! I'll lambaste dat coon when I gits him, so I will. I'll cotch him for yo'-all, Massa Tom," and, muttering to himself, the aged colored man endeavored to assume the activity of former years.
"Hark!" exclaimed Ned, as he and Tom were about ready to take part in the chase. "What's that noise, Tom?"
"Sounds like a motor-cycle."
"It is. That fellow—"
"It's the same chap!" interrupted Tom. "No use trying to chase him on that speedy machine. He's a mile away from here by now. He must have had it in waiting, ready for use. But come on, anyhow."
"Where are you going?"
"Out to the shop. I want to see if he got in there."
"But the charged wires?"
"He may have cut them. Come on."
It was as Tom had suspected. The deadly, charged wires, that formed a protecting cordon about his shops, had been cut, and that by an experienced hand, probably by someone wearing rubber gloves, who must have come prepared for that very purpose. During the night the current was supplied to the wires from a storage battery, through an intensifying coil, so that the charge was only a little less deadly than when coming direct from a dynamo.
"This looks bad, Tom," said Ned.
"It does, but wait until we get inside and look around. I'm glad I took my gun-plans to the house with me."
But a quick survey of the shop did not reveal any damage done, nor had anything been taken, as far as Tom could tell. The office of his main shop was pretty well upset, and it looked as though the intruder had made a search for something, and, not finding it, had entered the house.
"It was the gun-plans he was after, all right," decided Tom. "And I believe it was the same fellow who has been making trouble for me right along."
"You mean General Waller?"
"No, that German—the one who was at the machine shop."
"But who is he—what is his object?"
"I don't know who he is, but he evidently wants my plans. Probably he's a disappointed inventor, who has been trying to make a gun himself, and can't. He wants some of my ideas, but he isn't going to get them. Well, we may as well get back to bed, after I connect these wires again. I must think up a plan to conceal them, so they can't be cut."
While Tom and Ned were engaged on this, Koku came back, much out of breath, to report:
"Me not git, Master. He git on bang-bang machine and go off—puff!"
"So we heard, Koku. Never mind, we'll get him yet."
"Hu! Ef I had de fust chanst at him, I'd a cotched dat coon suah!" declared Eradicate, following the giant. "Koku he done git in mah way!" and he glared indignantly at the big man.
"That's all right, Rad," consoled Tom. "You did your best. Now we'll all get to bed. I don't believe he'll come back." Nor did he.
Tom and Ned were up at the first sign of daylight, for they wanted to go to the steel works, some miles away, in time to see the cannon taken out of the mould, and preparations made for boring the rifle channels. They found the manager, anxiously waiting for them.
"Some of my men are as interested in this as you are," he said to the young inventor. "A number of them declare that the cast will be a failure, while some think it will be a success."
"I think it will be all right, if my plans were followed," said Tom. "However, we'll see. By the way, what became of that German who made such a disturbance the day we cast the core?"
"Oh, you mean Baudermann?"
"Yes."
"Why, it's rather queer about him. The foreman of the shop where he was detailed, saw that he was an experienced man, in spite of his seemingly stupid ways, and he was going to promote him, only he never came back."
"Never came back? What do you mean?"
"I mean the day after the cast of the gun was made he disappeared, and never came back."
"Oh!" exclaimed Tom. He said nothing more, but he believed that he understood the man's actions. Failing to obtain the desired information, or perhaps failing to spoil the cast, he realized that his chances were at an end for the present.
With great care the gun was hoisted from the mould. More eyes than Tom's anxiously regarded it as it came up out of the casting pit.
"Bless my buttonhook!" cried Mr. Damon, who had gone with the lads. "It's a monster; isn't it?"
"Oh, wait until you see it with the jackets on!" exclaimed Ned, who had viewed the completed drawings. "Then you'll open your eyes."
The great piece of hollow steel tubing was lifted to the boring lathe. Then Tom and the manager examined it for superficial flaws.
"Not one!" cried the manager in delight.
"Not that I can see," added Tom.. "It's a success—so far."
"And that was the hardest part of the work," went on the manager of the steel plant. "I can almost guarantee you success from now on."
And, as far as the rifling was concerned, this was true. I will not weary you with the details of how the great core of Tom Swift's giant cannon was bored. Sufficient to say that, after some annoying delays, caused by breaks in the machinery, which had never before been used on such a gigantic piece of work, the rifling was done. After the jackets had been shrunk on, it would be rifled again, to make it true in case of any shrinkage.
Then came the almost Herculean task of shrinking on the great red-hot steel jackets and wire-windings, that would add strength to the great cannon. To do this the central core was set up on end, and the jackets, having been heated in an immense furnace, were hoisted by a great crane over the core, and lowered on it as one would lower his napkin ring over the rolled up napkin.
It took weeks of hard work to do this, and Tom and Ned, with Mr. Damon occasionally for company, remained almost constantly at the plant. But finally the cannon was completed, the rifling was done over again to correct any imperfections, and the manager said:
"Your cannon is completed, Mr. Swift. I want to congratulate you on it. Never have we done such a stupendous piece of work. Only for your plans we could not have finished it. It was too big a problem for us. Your cannon is completed, but, of course, it will have to be mounted. What about the carriage?"
"I have plans for that," replied Tom; "but for the present I am going to put it on a temporary one. I want to test the gun now. It looks all right, but whether it will shoot accurately, and for a greater distance than any cannon has ever sent a projectile before, is yet to be seen."
"Where will you test it?"
"That is what we must decide. I don't want to take it too far from here. Perhaps you can select a place where it would be safe to fire it, say with a range of about thirty miles."
"Thirty miles! why, my dear sir—"
"Oh, I'm not altogether sure that it will go that distance," interrupted Tom, with a smile; "but I'm going to try for it, and I want to be on the safe side. Is there such a place near here?"
"Yes, I guess we can pick one out. I'll let you know."
"Then I must get back and arrange for my powder supply," went on the young inventor. "We'll soon test my giant cannon!"
"Bless my ear-drums!" cried Mr. Damon. "I hope nothing bursts. For if that goes up, Tom Swift—"
"I'm not making it to burst," put in Tom, with a smile. "Don't worry. Now, Ned, back to Shopton to get ready for the test."
"Whew, how it rains!" exclaimed Ned, as he looked out of the window.
"And it doesn't seem to show any signs of letting up," remarked Tom. "It's been at it nearly a week now, and it is likely to last a week longer."
"It's beastly," declared his chum. "How can you test your gun in this weather?"
"I can't. I've got to wait for it to clear."
"Bless my rubber boots! it's just got to stop some time," declared Mr. Damon. "Don't worry, Tom."
"But I don't like this delay. I have heard that General Waller has perfected a new gun—and it's a fine one, from all accounts. He has the proving grounds at Sandy Hook to test his on, and I'm handicapped here. He may beat me out."
"Oh, I hope not, Tom!" exclaimed Ned. "I'm going to see what the weather reports say," and he went to hunt up a paper.
It was several weeks after the completion of Tom's giant cannon. In the meanwhile the gun had been moved by the steel company to a little-inhabited part of New York State, some miles from the plant. The gun had been mounted on an improvised carriage, and now Tom and his friends were waiting anxiously for a chance to try it.
The work was not complete, for the steel company employees had been hampered by the rain. Never before, it seemed, had there been so much water coming down from the clouds. Nearly every day was misty, with gradations from mere drizzles to heavy downpours. There were occasional clear stretches, however, and during them the men worked.
A few more days of clear weather would be needed before the gun could be fastened securely to the carriage, and then Tom could fire one of the great projectiles that had been cast for it. Not until then would he know whether or not his cannon was going to be a success.
Meanwhile nothing more had been heard or seen of the spy. He appeared to have given up his attempts to steal Tom's secret, or to spoil his plans, if such was his object.
The place of the test, as I have said, was in a deserted spot. On one side of a great valley the gun was being set up. Its muzzle pointed up the valley, toward the side of a mountain, into which the gigantic projectile could plow its way without doing any damage. Tom was going to fire two kinds of cannon balls—a solid one, and one containing an explosive.
The gun was so mounted that the muzzle could be elevated or depressed, or swung from side to side. In this way the range could be varied. Tom estimated that the greatest possible range would be thirty miles. It could not be more than that, he decided, and he hoped it would not be much less. This extreme range could be attained by elevating the gun to exactly the proper pitch. Of course, any shorter range could, within certain limits, also be reached.
The gun was pointed slantingly up the valley, and there was ample room to attain the thirty-mile range without doing any damage.
At the head of the valley, some miles from where the giant cannon was mounted, was an immense dam, built recently by a water company for impounding a stream and furnishing a supply of drinking water for a distant city. At the other end of the valley was the thriving village of Preston. A railroad ran there, and it was to Preston station that Tom's big gun had been sent, to be transported afterward, on specially made trucks, drawn by powerful autos, to the place where it was now mounted.
Tom had been obliged to buy a piece of land on which to build the temporary carriage, and also contract for a large slice of the opposite mountain, as a target against which to fire his projectiles.
The valley, as I have said, was desolate. It was thickly wooded in spots, and in the centre, near the big dam, which held back the waters of an immense artificial lake, was a great hill, evidently a relic of some glacial epoch. This hill was a sort of division between two valleys.
Tom, Ned, Mr. Damon, with Koku, and some of the employees of the steel company, had hired a deserted farmhouse not far from the place where the gun was being mounted. In this they lived, while Tom directed operations.
"The paper says 'clear' tomorrow," read Ned, on his return. "'Clear, with freshening winds.'"
"That means rain, with no wind at all," declared Tom, with a sigh. "Well, it can't be helped. As Mr. Damon says, it will clear some time."
"Bless my overshoes!" exclaimed the odd gentleman. "It always has cleared; hasn't it?"
No one could deny this.
There came a slackening in the showers, and Tom and Ned, donning raincoats, went out to see how the work was progressing. They found the men from the steel concern busy at the great piece of engineering.
"How are you coming on?" asked Tom of the foreman.
"We could finish it in two days if this rain would only let up," replied the man.
"Well, let's hope that it will," observed Tom.
"If it doesn't, there's likely to be trouble up above," went on the foreman, nodding in the direction of the great dam.
"What do you mean?"
"I mean that the water is getting too high. The dam is weakening, I heard."
"Is that so? Why, I thought they had made it to stand any sort of a flood."
"They evidently didn't count on one like this. They've got the engineer who built it up there, and they're doing their best to strengthen it. I also heard that they're preparing to dynamite it to open breeches here and there in it, in case it is likely to give way suddenly."
"You don't mean it! Say, if it does go out with a rush it will wipe out the village."
"Yes, but it can't hurt us," went on the foreman. "We're too high up on the side of the hill. Even if the dam did burst, if the course of the water could be changed, to send it down that other valley, it would do no harm, for there are no settlements over there," and he pointed to the distant hill.
It was near this hill that Tom intended to direct his projectiles, and on the other side of it was another valley, running at right angles to the one crossed by the dam.
As the foreman had said, if the waters (in case the dam burst) could be turned into this transverse valley, the town could be saved.
"But it would take considerable digging to open a way through that side of the mountain, into the other valley," went on the man.
"Yes," said Tom, and then he gave the matter no further thought, for something came up that needed his attention.
"Have you your explosive here?" asked the foreman of the young inventor the next day, when the weather showed signs of clearing.
"Yes, some of it," said Tom. "I have another supply in a safe place in the village. I didn't want to bring too much here until the gun was to be fired. I can easily get it if we need it. Jove! I wish it would clear. I want to get out in my Humming Bird, but I can't if this keeps up." Tom had brought one of his speedy little airships with him to Preston.
The following day the clouds broke a little, and on the next the sun shone. Then the work on the gun went on apace. Tom and his friends were delighted.
"Well, I think we can try a shot tomorrow!" announced Tom with delight on the evening of the first clear day, when all hands had worked at double time.
"Bless my powder-horn!" exclaimed Mr. Damon. "You don't mean it!"
"Yes, the gun is all in place," went on the young inventor. "Of course, it's only a temporary carriage, and not the disappearing one I shall eventually use. But it will do. I'm going to try a shot tomorrow. Everything is in readiness."
There came a knock on the door of the room Tom had fitted up as an office in the old farmhouse.
"Who is it?" he asked.
"Me—Koku," was the answer.
"Well, what do you want, Koku?"
"Man here say him must see Master."
Tom and Ned looked at each other, suspicion in their eyes.
"Maybe it's that spy again," whispered Ned.
"If it is, we'll be ready for him," murmured his chum. "Show him in, Koku, and you come in too."
But the man who entered at once disarmed suspicion. He was evidently a workman from the dam above, and his manner was strangely excited.
"You folks had better get out of here!" he exclaimed.
"Why?" asked Tom, wondering what was going to happen.
"Why? Because our dam is going to burst within a few hours. I've been sent to warn the folks in town in time to let them take to the hills. You'd better move your outfit. The dam can't last twenty-four hours longer!"
"Bless my fountain pen!" exclaimed Mr. Damon. "You don't mean it!"
"I sure do!" went on the man who had brought the startling news. "And the folks down below aren't going to have any more time than they need to get out of the way. They'll have to lose some of their goods, I reckon. But I thought I'd stop on my way down and warn you. You'd better be getting a hustle on."
"It's very kind of you," spoke Tom; "but I don't fancy we are in any danger."
"No danger!" cried the man. "Say, when that water begins to sweep-down here nothing on earth can stop it. That big gun of yours, heavy as it is, will be swept away like a straw, I know—I saw the Johnstown flood!"
"But we're so high up on the side of the hill, that the water won't come here," put in Ned. "We had that all figured out when we heard the dam was weak. We're not in any danger; do you think so, Tom?"
"Well, I hardly do, or I would not have set the gun where I did. Tell me," he went on to the man, "is there any way of opening the dam, to let the water out gradually?"
"There is, but the openings are not enough with such a flood as this. The engineers never counted on so much rain. It's beyond any they ever had here. You see, there was a small creek that we dammed up to make our lake. Some of the water from the spillway flows into that now, but its channel won't hold a hundredth part of the flood if the dam goes out.
"You'd better move, I tell you. The dam is slowly weakening. We've done all we can to save it, but that's out of the question. The only thing to do is to run while there's time. We've tried to make additional openings, but we daren't make any more, or the wall will be so weakened that it will go out in less than twenty-four hours.
"You've had your warning, now profit by it!" he added. "I'm going to tell those poor souls down in the valley below. It will be tough on them; but it can't be helped."
"If the dam bursts and the water could only be turned over into the transverse valley, this one would be safe," said Tom, in a low voice.
"Yes, but it can't be done!" the messenger exclaimed. "Our engineers thought of that, but it would take a week to open a channel, and there isn't time. It can't be done!"
"Maybe it can," spoke Tom, softly, but no one asked him what he meant.
"Well, I must be off," the man went on. "I've done my duty in warning you."
"Yes, you have," agreed Tom, "and if any damage comes to us it will be our own fault. But I don't believe there will."
The man hastened out, murmuring something about "rash and foolhardy people."
"What are you going to do, Tom?" asked Ned.
"Stay right here."
"But if the dam bursts?"
"It may not, but, if it does, we'll be safe. I have had a look at the water, and there's no chance for it to rise here, even if the whole dam went out at once, which is not likely. Don't worry. We'll be all right."
"Bless my checkbook!" cried Mr. Damon. "But what about those poor people in the valley?"
"They will have time to flee, and save their lives," spoke the young inventor; "but they may lose their homes. They can sue the water company for damages, though. Now don't do any more worrying, but get to bed, and be ready for the test tomorrow. And the first thing I do I'm going to have a little flight in the Humming Bird to get my nerves in trim. This long rain has gotten me in poor shape. Koku, you must be on the alert tonight. I don't want anything to happen to my gun at the last minute."
"Me watch!" exclaimed the giant, significantly, as he picked up a heavy club.
"Do you anticipate any trouble?" asked Ned, anxiously.
"No, but it's best to be on the safe side," answered Tom. "Now let's turn in."
Certainly the next day, bright and sunshiny as it broke, had in it little of impending disaster. The weather was fine after the long-continued rains, and the whole valley seemed peaceful and quiet. At the far end could be seen the great dam, with water pouring over it in a thin sheet, forming a small stream that trickled down the centre of the valley, and to the town below.
But, through great pipes that led to the drinking system, though they were unseen, thundered immense streams of solid water, reducing by as much as the engineers were able the pressure on the concrete wall.
Tom and Ned, in the Humming Bird, took a flight out to the dam shortly after breakfast, when the steel men were putting a few finishing touches to the gun carriage, ready for the test that was to take place about noon.
"It doesn't look as though it would burst," observed Ned, as the aircraft hovered over the big artificial lake.
"No," agreed Tom. "But I suppose the engineers want to be on the safe side in case of damage suits. I want to take a look at the place where the other valley comes up to this at right angles."
He steered his powerful little craft in that direction, and circled low over the spot.
"A bursting projectile, about where that big white stone is, would do the trick," murmured Tom.
"What trick?" asked Ned, curiously.
"Oh, I guess I was talking to myself," admitted Tom, with a laugh. "I may not have to do it, Ned."
"Well, you're talking in riddles today, all right, Tom. When you get ready to put me wise, please do."
"I will. Now we'll get back, and fire our first long shot. I do hope I make a record."
There was much to be done, in spite of the fact that the foreman of the steel workers assured Tom that all was in readiness. It was some time that afternoon when word was given for those who wished to retire to an improvised bomb-proof. Word had previously been sent down the valley so that no one, unless he was looking for trouble, need be in the vicinity of the gun, nor near where the shots were to land.
Through powerful glasses Tom and Ned surveyed the distant mountain that was to be the target. Several great squares of white cloth had been put at different bare spots to make the finding of the range easy.
"I guess we're ready now," announced the young inventor, a bit nervously. "Bring up the powder, Koku."
"Me bring," exclaimed the giant, calmly, as he went to the bomb-proof where the powerful explosive was kept.
The great projectile was in readiness to be slung into the breech by means of the hoisting apparatus, for it weighed close to two tons. It was carefully inserted under Tom's supervision. It carried no bursting charge, for Tom's first shot was merely to establish the extreme range that his cannon would shoot.
"Now the powder," called the young inventor. To avoid accidents Koku handled this himself, the hoisting apparatus being dispensed with. Tom figured out that five hundred pounds of his new, powerful explosive would be about the right amount to use, and this quantity, divided into several packages to make the handling easier, was quickly inserted in the breech of the gun by Koku.
"Bless my doormat!" cried Mr. Damon, who stood near, looking nervously on. "Don't drop any of that."
"Me no drop," was the answer.
Tom was busily engaged in figuring on a bit of paper, and Ned, who looked over his shoulder, saw a complicated compilation that looked to be a combination of geometry, algebra, differential calculus and other higher mathematics.
"What are you doing, Tom?" he asked.
"I'm trying to confirm my own theories by means of figures, to see if I can really reach that farthest target."
"What, not the one thirty miles away.
"That's it, Ned. I want to get a thirty-mile range if I can."
"It isn't possible, Tom."
"Bless my tape measure! I should say not!" cried Mr. Damon.
"We'll see," replied Tom, quietly. "Put in the primer, Ned; and, Koku, close the breech and slot it home."
In a few seconds the great gun was ready for firing.
"Now," said Tom, "this thing may be all right, and it may not. The only thing that can cause an accident will be a flaw in the steel. No one can guard against that. So, in order to be on the safe side, we will all go into the bomb-proof, and I will fire the gun from there. The wires are long enough."
They all agreed that this was good advice, and soon the steel men and Tom's friends were gathered in a sort of cave that had been hollowed out in the side of the hill, and at an angle from the big gun.
"If it does burst—which I hope it won't," said Tom, "the pieces will fly in straight lines, so we will be safe enough here. Ned, are you are ready at the instruments?"
"Yes, Tom."
"I want you to note the registered muzzle velocity. Mr. Damon, you will please read the pressure gauge. After I press the button I'm going to watch the landing of the projectile through the telescope."
The gun had been pointed, as I have said, at the farthest target—one thirty miles away, telescope sights on the giant cannon making this possible.
"All ready!" cried Tom.
"All ready," answered Ned.
There was a tense moment; Tom's thumb pressed home the electric button, and then came the explosion.
It seemed for a moment as if everyone was lifted from his feet. They had all stood on their tiptoes, and opened their mouths to lessen the shock, but even then it was terrific. The very ground shook—from the roof of their cave small stones and gravel rattled down on their heads. Their ear-drums were numbed from the shock. And the noise that filled the valley seemed like a thousand thunderbolts merged into one.
Tom rushed from the bombproof, dropping the electric button. He caught sight of his gun, resting undisturbed on the improvised carriage.
"Hurray!" he cried in delight. "She stood the charge all right. And look! look!" he cried, as he pointed the glasses toward the distant hillside. "There goes my projectile as straight as an arrow. There! By Caesar, Ned! It landed within three feet of the target! Oh, you beauty!" he yelled at his giant cannon. "You did all I hoped you would! Thirty miles, Ned! Think of that! A two-ton projectile being shot thirty miles!"
"It's great, Tom!" yelled his chum, clapping him on the back, and capering about. "It's the longest shot on record."
"It certainly is," declared the foreman of the steel workers, who had helped in casting many big guns. "No cannon ever made can equal it. You win, Tom Swift!"
"Bless my armor plate!" gasped Mr. Damon. "What attacking ship against the Panama Canal could float after a shot like that."
"Not one," declared Tom; "especially after I put a bursting charge into the projectile. We'll try that next."
By means of compressed air the gases and some particles of the unexploded powder were blown out of the big cannon. Then it was loaded again, the projectile this time carrying a bursting charge of another explosive that would be set off by concussion.
Once more they retired to the bombproof, and again the great gun was fired. Once more the ground shook, and they were nearly deafened by the shock.
Then, as they looked toward the distant hillside, they saw a shower of earth and great rocks rise up. It was like a sand geyser. Then, when this settled back again, there was left a gaping hole in the side of the mountain.
"That does the business!" cried Tom. "My cannon is a success!"
The last shot did not go quite as far as the first, but it was because a different kind of projectile was used. Tom was perfectly satisfied, however. Several more trials were given the gun, and each one confirmed the young inventor in his belief that he had made a wonderful weapon.
"If that doesn't fortify the Panama Canal nothing will," declared Ned.
"Well, I hope I can convince Uncle Sam of that," spoke Tom, simply.
The muzzle velocity and the pressure were equal to Tom's highest hopes. He knew, now, that he had hit on just the right mixture of powder, and that his gun was correctly proportioned. It showed not the slightest strain.
"Now we'll try another bursting shell," he said, after a rest, during which some records were made. "Then we'll call it a day's work. Koku, bring up some more powder. I'll use a little heavier charge this time."
It was while the gun was being loaded that a horseman was seen riding wildly down the valley. He was waving a red flag in his hand.
"Bless my watch chain!" cried Mr. Damon. "What's that?"
"It looks as though he was coming to give us a warning," suggested the steel foreman.
"Maybe someone has kicked about our shooting," remarked Ned.
"I hope not," murmured Tom.
He looked at the horseman anxiously. The rider came nearer and nearer, wildly waving his flag. He seemed to be shouting something, but his words could not be made out. Finally he came near enough to be heard.
"The dam! The dam!" he cried. "It's bursting. Your shots have hastened it. The cracks are widening. You'd better get away!" And he galloped on.
"Bless my toilet soap!" gasped Mr. Damon.
"I was afraid of this!" murmured Tom. "But, since our shots have hastened the disaster, maybe we can avert it."
"How?" demanded Ned.
"I'll show you. All hands come here and we'll shift this gun. I want it to point at that big white stone!" and he indicated an immense boulder, well up the valley, near the place where the two great gulches joined.
"What are you going to do, Tom?" cried Ned, as he, with the others, worked the hand gear that shifted the big gun. When it was permanently mounted electricity would accomplish this work. "What's your game, Tom?"
"Don't you remember, Ned? When we were talking about the chance of the dam bursting, I said if the current of suddenly released water could be turned into the other valley, the people below us would be saved."
"Yes."
"Well, that's what I'm going to do. I'm going to fire a bursting shell at the point where the two valleys come together. I'll break down the barrier of rock and stone between them."
"Bless my shovel and hoe!" cried Mr. Damon.
"If we can turn enough of the water into the other valley, where no one lives, and where it can escape into the big river there, the amount that will flow down this valley will be so small that only a little damage will be done."
"That's right!" declared the steel foreman, as he caught Tom's idea. "It's the only way it could be done, too, for there won't be time to make the necessary excavation any other way. Is the gun swung around far enough, Mr. Swift?"
"No, a little more toward me," answered Tom, as he peered through the telescope sights. "There, that will do. Now to get the proper elevation," and he began to work the other apparatus, having estimated the range as well as he could.
In a few seconds the giant cannon was properly trained on the white rock. Meanwhile the horseman, with his red flag, had continued on down the valley. In spite of his warning of the night before, it developed that a number had disregarded it, and had remained in their homes. Most of the inhabitants, however, had fled to the hills, to stay in tents, or with such neighbors as could accommodate them. Some lingered to move their household goods, while others fled with what they could carry.
It was to see that the town was deserted by these late-stayers that the messenger rode, crying his warning as did the messenger at the bursting of the Johnstown dam twenty-odd years ago.
"The projectile!" cried Tom, as he saw that all was in readiness. "Lively now! I can see the top of the dam beginning to crumble," and he laid aside the telescope he had been using.
The projectile, with a heavy charge of bursting powder, was slung into the breech of the gun.
"Now the powder, Koku!" called Tom. "Be quick; but not so fast that you drop any of it."
"Me fetch," responded the giant, as he hastened toward the small cave where the explosive was kept. As the big man brought the first lot, and Ned was about to insert it in the breech of the gun, behind the projectile, Tom exclaimed:
"Just let me have a look at that. It's some that I first made, and I want to be sure it hasn't gone stale."
Critically he looked at the powerful explosive. As he did so a change came over his face.
"Here, Koku!" the young inventor said. "Where did you get this?"
"In cave, Master."
"Is there any more left?"
"Only enough for this one shoot."
"By Jove!" muttered Tom. "There's been some trick played here!" and he set off on a run toward the bomb-proof.
"What's the matter?" cried Ned, as he noticed the agitation of his chum.
"The powder has been doped!" yelled Tom. "Something has been put in it to make it nonexplosive. It's no good. It wouldn't send that shell a thousand yards, and it's got to go five miles to do any good. My plan won't work."
"Doped the powder?" gasped Ned. "Who could have done it?"
"I don't know. There must have been some spy at work. Quick, run and ask the foreman if any of his men are missing. I'll see if there's enough of the good powder left to break down the barrier!"
Ned was away like a shot, while the others, not knowing what to make of the strange conduct of the two lads, looked on in wonder. Tom raced toward the cave where the powder was stored, Koku following him.
"Bless my shoe laces!" cried Mr. Damon. "Look at the dam now!"
They gazed to where he pointed. In several places the concrete spillway had crumbled down to a ragged edge, showing that the solid wall was giving way. The amount of water flowing over the dam was greater now. The creek was steadily rising. Down the valley the horseman with the red flag was but a speck in the distance.
"What can I do? What can I do?" murmured Tom. "If all the powder there is left has been doped, I can't save the town! What can I do? What can I do?"
Ned had reached the foreman, who, with his helpers, was standing about the big gun.
"Have any of your men left recently?" yelled Ned.
"Any of my men left? What do you mean?
"Schlichter went yesterday," said the timekeeper. "I thought he was in quite a hurry to get his money, too."
"Schlichter gone!" exclaimed the foreman. "He was no good anyhow. I think he was a sort of Anarchist; always against the government, the way he talked. So he has left; eh? But what's the matter, Ned?"
"Something wrong with the powder. Tom can't shoot the cannon and turn aside the water to save the town. Some of his enemies have been at work. Schlichter leaving at this time, and in such hurry, makes it look suspicious."
"It sure does! And, now I recall it, I saw him yesterday near your powder magazine. I called him down for it, for I knew Tom Swift had given orders that only his own party was to go near it. So the powder is doped; eh?"
"Yes! It's all off now."
He turned to see Tom approaching on the run.
"Any good powder left?" asked Ned.
"Not a pound. Did you hear anything?"
"Yes, one man has disappeared. Oh, Tom, we've got to fail after all! We can't save the town!"
"Yes, we can, Ned. If that dam will only hold for half an hour more."
"What do you mean?"
"I mean that I have another supply of good powder in the village. I secreted some there, you remember I told you. If I can go get that, and get back here in time, I can break down the barrier with one shot, and save Preston."
"But you never can make the trip there and back in time, with the powder, Tom. It's impossible. The dam may hold half an hour, or it may not. But, if it does, you can't do anything!"
"I can't? Well, I'm going to make a big try, Ned. You stay on the job here. Have everything ready so that when I get back with the new explosive, which I hope hasn't been tampered with, I can shove it into the breech, and set it off. Have the wires, primers and button all ready for me."
Then Tom set off on the run.
"Where are you going?" gasped his chum. "You can never run to Preston and back in time."
"I don't intend to. I'm going in my airship. Koku, never mind bringing the rest of the powder from the cave. It's no good. Run out the Humming Bird. I'm going to drive her to the limit. I've just got to get that powder here on time!"
"Bless my timetable!" gasped Mr. Damon. "That's the only way it can be done. Lucky Tom brought the airship along!"
The young inventor, pausing only to get some cans for the explosive, and some straps with which to fasten them in the monoplane, leaped into the speedy craft.
The motor was adjusted; Koku whirled the propeller blades. There was a staccato succession of explosions, a rushing, roaring sound, and then the craft rose like a bird, and Tom circled about, making a straight course for the distant town, while below him the creek rose higher and higher as the dam continued to crumble away.