When the board members left, the chief promised to let Tom know the result of the formal report as soon as possible.

The young inventor did not have long to wait. In about two weeks, during which time he and Ned perfected several little matters about the cannon, there came an official-looking document.

"Well, we'll soon know the verdict," spoke Tom, somewhat nervously, as he opened the envelope. Quickly he read the enclosure.

"What is it!" cried Ned.

"The government accepts my gun!" exclaimed the young inventor. "It will purchase a number as soon as they can be made. We are to take one to Panama, where it will be set up. Hurray, Ned, my boy! Now for Panama!"



CHAPTER XXI

OFF FOR PANAMA

"Well, Tom, it doesn't seem possible; does it, old man?"

"You're right, Ned—in a way. And yet, after all the hard work we've done, almost anything is possible."

"Hard work! We? Oh, pshaw! You've done most of it, Tom. I only helped here and there."

"Indeed, and you did more than that. If it hadn't been for you, Mr. Damon and Koku we'd never have gotten off as soon as we did. The government is the limit for doing things, sometimes."

"Bless my timetable! but I agree with you," put in Mr. Damon. "But at last we are on the way, in spite of delays."

This conversation took place on board one of Uncle Sam's warships, which the President had designated to take Tom's giant cannon to the Panama Canal.

The big gun had been lashed to the deck of the vessel, and was well protected from the weather. In the hold the parts of the disappearing carriage, which Tom had at last succeeded in having made, were securely stowed. In another part of the warship were the big projectiles, some arranged to be fired as solid shots, and others with a bursting charge. There was also a good supply of the powerful explosive, and Tom had taken extraordinary precautions so that it could not be tampered with. Koku had been detailed as a sort of guard over it, and to relieve him was a trustworthy sergeant of marines.

"If anyone tries to dope that powder now, and spoil my test at Panama," declared Tom, "he'll wish he'd never tried it."

"Especially if Koku gets hold of him," added Ned, grimly.

"But I don't believe there is any danger," went on the young inventor. "I spoke about what had happened, and the ordnance board took extra precautions to see that none but men and officers who could be implicitly trusted had anything to do with this expedition."

"You don't really believe anything like treachery would be attempted; do you, Tom?"

"I don't know what to say. Certainly I can't see why anyone connected with Uncle Sam would want to throw cold water on a plan to fortify the canal, even if an outsider has invented the gun—I mean someone like myself, not connected with the army or navy."

"If it's anything it's jealousy," declared Ned, "That General Waller—"

"There you go again, Ned. Let's not talk about it. Come on forward and see what progress we are making."

It must not be supposed that to get the big gun aboard the vessel, arrange for a new supply of the explosive, and for many of the great projectiles, had been easy work. It was a task that taxed the skill and strength of Tom and his friends to the utmost.

There had been wearying delays, especially in the matter of making the disappearing carriage. At times it seemed as if the required projectiles would never be finished. The powder, too, gave trouble, for sometimes batches would be turned out that were utterly worthless.

But Tom never gave up, even when it seemed that some of the failures were purposely made. Ned declared that there was a conspiracy against his chum, but Tom could not see it that way. It was due to a combination of circumstances, he insisted.

But finally the gun had been put aboard the ship, having been transported from the proving ground in the valley, and they were now en route to Panama. There the giant cannon was to be set up, and tried again. If it came up to expectations it was to be finally adopted as the official gun for the protection of the big canal, and Tom would receive a substantial reward.

"And I'm confident that it will make good," said the young inventor to his chum, as they paced the deck of the vessel. "In fact, I'm so sure I have practically engaged the Universal Steel Company to hold itself in readiness to make several more of the guns."

"But suppose Uncle Sam decides against the cannon on this second test?"

"Well, then I've lost out, that's all," declared Tom, philosophically. "But I don't believe they will."

"It certainly is a giant cannon," remarked Ned, as he paused to look at the prostrate monster, lashed to the deck, with its wrappings of tarpaulins. "It looks bigger here than it did when you fired the shot that saved the town, Tom."

"Yes, I suppose it does, by contrast. But let's go down and see how the powder and shells are standing the trip. I told the captain to have them securely lashed, so if we struck rough weather, and the vessel rolled, they wouldn't carry away."

"Especially the powder," put in Ned. "If that starts to banging around—well, I'd rather be somewhere else."

"Bless my rain gauge!" cried Mr. Damon. "Please don't say such things. You make me nervous. You're as bad as that steel foreman."

"All right, I'll be better," promised Ned, with a laugh.

The two chums found that every precaution had been taken in regard to the projectiles and powder. Koku was on guard, the giant regarding the boxes of explosive with a calm but determined eye. It would not be well for any unauthorized hand to tamper with them.

"Am dere anyt'ing I kin do fo' yo'-all, Massa Tom?" inquired Eradicate, as the young inventor and Ned prepared to go on deck again. The aged colored man had insisted on coming as a sort of personal bodyguard to Tom, and the latter had not the heart to refuse him. Eradicate was desperately jealous of the giant.

"Huh!" Eradicate had said, "anybody kin sit an' look at a lot ob dem powder boxes; but 'tain't everybody what kin wait on Massa Tom. I kin, an' I'se gwine t' do it." And so he had.

It was planned to proceed directly to Colon, the eastern terminus of the canal, from New York, stopping at Santiago to transact some government business there. The big gun was to be mounted on a barbette near the Gatun locks, pointing out to sea, and the trial shots would be fired over the water.

Eventually the gun would be so mounted as to swing in a circle, so as to command the land as well as the water; and, in fact, if the government decided to adopt Tom's giant cannon as the official protective arm of the canal, they would all be so mounted. For, of course, it might be possible for land as well as sea forces to attack and try to capture the big ditch.

The first few days of the voyage were pleasant enough. The weather was fine, and Tom was kept busy explaining to many of the officers aboard the ship the principles of his gun, powder and projectiles. Members of the ordnance board, who had been detailed to witness the test, were also much interested as Tom modestly described his work on the giant cannon.

At Santiago de Cuba, when Tom and Ned were standing near the gangway, watching the officers returning from shore leave, for the ship was to proceed soon, after a two days' stay, the young inventor started as he noticed a military man walking aboard.

"Look, Ned!" he exclaimed, in a low voice.

"Where?"

"At that man—an officer in civilian dress, I should judge—haven't you seen him before?"

"I have, Tom. Now, where was it? I seem to remember his face; and yet he wasn't dressed like this the last time I saw him."

"I guess not, Ned. He had on a uniform then."

"By jinks! I have it. That German officer—von Brunderger! That's he!"

"You're right, Ned. And he's got his servant with him, I guess," and Tom nodded toward a stolid German who was carrying the other's suitcase.

"I wonder what he's doing aboard here?" went on our hero's chum.

"We'll soon know," spoke Tom. "He's seen us and is nodding. We might as well go meet him."

"Ah, my good friend, Tom Swift!" exclaimed General von Brunderger, genially, as he grasped the hands of Tom and Ned. "I am glad to see you both again." He seemed to mean it, though he had not been especially cordial to them at the first gun test. "Take my grip below," he said in German to the man, "and, Rudolph, find Lieutenant Blake and inform him that I am on board. I have been invited to go to Panama by Lieutenant Blake," he added to Tom. "I have never seen the big ditch that you wonderful Americans have so nearly finished."

"It is going to be a big thing," spoke Tom. "I am proud that my gun is going to help protect it."

"Ah, so you were successful, then?" and his voice expressed surprise. "I had not heard. And the big gun; is he here?" Though speaking very good English, von Brunderger occasionally lapsed into the idioms of his Fatherland.

"Yes, it's on board," said Tom. "Are you going to Panama for any special purpose?"

Ned declared afterward that the German started as Tom asked this question, but if he did the young inventor scarcely noticed it. In an instant, however, von Brunderger was composed again.

"I go but to see the big ditch before the water is let in," he replied. "And since your gun is to have a test I shall be glad to witness that. You see, I am commissioned by my Kaiser to learn all that you Americans will allow me to in reference to your ways of doing things—in the army, the navy and in the pursuit of peace. After all, preparation for war is the best means of securing peace. Your officers have been more than kind and I have taken advantage of the offer to go to Panama. Lieutenant Blake said the ship would stop here, and, as I had business in Cuba, I came and waited. I am delighted to see you both again."

He went below, leaving Tom and Ned staring at one another.

"Well, what do you think of it?" asked Ned.

"I don't see anything to be worried about," declared Tom. "It's true that a German once tried to make trouble for me, but this von Brunderger is all right, as far as I can learn. He has the highest references, and is an accredited representative of the Kaiser. You are too suspicious, Ned, just as you were in the case of General Waller."

"Maybe so."

From Santiago, swinging around the island of Jamaica, the warship took her way, with the big gun, to Colon. When half way across the Caribbean Sea they encountered rough weather.

The storm broke without any unusual preliminaries, but quickly increased to a hurricane, and when night fell it saw the big ship rolling and tossing in a tempestuous sea. Torn was anxious about his big gun, but the captain assured him that double lashings would make it perfectly safe.

Tom and Ned had seen little of the German officer that day, nor, in fact, since he came aboard. He kept much in the quarters of the other officers, and the report was current that he was a "jolly good fellow."

Rather anxious as to the outcome of the storm, Tom turned in late that night, not expecting to sleep much, for there were many unusual noises. But he did drop off into a doze, only to be awakened about an hour later by a commotion on deck.

"What's up, Ned?" he called to his chum, who had an adjoining stateroom.

"I don't know, Tom. Something is going on, though. Hear that thumping and pounding!"

As Ned spoke there came a tremendous noise from the deck.

"By Jove!" yelled Tom, jumping from his berth. "It's my big gun! It has torn loose from the lashings and may roll overboard!"



CHAPTER XXII

AT GATUN LOCKS

"Steady there now, men! Pass forward those lashings! Careful! Look out, or you'll be caught by it when she rolls! Another turn around the bitts!"

It was the officer of the deck giving orders to a number of marines and sailors as Tom hastily clad, leaped on deck, followed by his chum. The warship was pitching and tossing worse than ever in the heaving billows, and the men were engaged in making fast the giant cannon, which, as Tom had surmised, had torn loose from the steel cables holding it down on deck.

"Come on, Ned!" cried Tom. "We've got to help here!"

"That's right. Look at her swing, would you? If she hits anything it's a goner!"

The breech of the gun appeared to be the end that had come loose, while the muzzle still held fast. And this immense mass of steel was swinging about, eluding the efforts of the ship's officers and crew to capture it. And it seemed only a question of time when the muzzle would tear loose, too. Then, free on deck, the giant cannon would roll through the frail bulwarks, and plunge into the depths of the sea.

"Look out for yourselves, boys!" cried the officer, as he saw Tom and Ned. "This is no plaything!"

"I know it!" gasped Tom. "But we've got to fasten it down."

"That's what we're trying to do," answered the other. "We did get the bight of a cable over the breech, but the men could not hold it, even though they took a couple of turns around the bitts."

"Ned, go call Koku!" cried Tom. "We need him up here."

"That's right!" declared his chum. "If anyone can hold the cable with the weight of the big gun straining on it, the giant can. I'll get him!"

"On deck, Koku, quick!" gasped Ned. "Master's cannon may fall into the sea."

"But the powder!" asked the big man, simply. "Master told me to guard the powder. I stay here."

"No, I'll stay!" insisted Ned. "You are needed on deck, I'll take your place here."

Koku stared uncomprehendingly for a moment, while the loosened gun continued to thump and pound on the deck as though it would burst through. Then it filtered through the dull brain of honest Koku what was wanted.

"I go," he said, and he hurried up the companionway, while Ned, eager to be with Tom, took up the less exciting work of guarding the powder.

Once more, with the giant strength of Koku to aid in the work, the task of lashing the gun again to the deck was undertaken. A bight of steel cable was gotten around the breech, and then passed to a big bitt, or stanchion, bolted to the deck. Koku, working on the heaving deck, amid the hurricane, took a turn around the brace.

There came a roll of the ship that threatened to send the gun sliding against the stanchion, but Koku braced himself. His arms, great bunches of muscles, strained and fairly cracked with the strain. The wire rope seemed to give. Then, as the ship rolled the other way, the strain eased. Koku, aided by the cable, and by the leverage given by the several turns about the bitts, had held the big gun.

"Quick!" cried Tom. "Now another rope so it can't roll the opposite way, and we'll have her."

For a moment the ship was on a level keel, and taking advantage of this, when the weight of the gun would be neutral, another cable was passed around it. Then it was a comparatively easy matter to put on more lashings until the giant cannon was once more fast.

"Whew! But that was tough work!" exclaimed Tom, as he once more entered the stateroom with Ned.

"It must have been," agreed his chum, who had been relieved at the powder station by the giant.

"I thought it would surely go overboard," went on Tom. "Only for Koku it would have. Those fellows couldn't hold it when the ship rolled."

"How did it happen to get loose?" asked Ned.

"Oh, the cables frayed, I suppose. I'll take a look in the morning. Say, but this is some storm!"

"Is the gun all right now?"

"Yes, it's fastened down like a mummy. It can't get loose unless the whole deck comes with it. We can sleep in peace."

"Not much sleep in this blow, I guess," responded Ned.

But they did manage to get some rest by morning, at which time the hurricane seemed to have blown itself out. The day saw the sea gradually calm down, and the big cannon was made additionally secure against a possible recurrence of the accident. But a few days more and it would be safe at Colon.

Tom and Ned had gone on deck soon after breakfast to look at the cannon. All about were pieces of the broken cables, that had been cast aside when the new lashings were put on. Ned picked up one end, remarking:

"These seem mighty strong. It's queer how they broke."

"Well, there was quite a weight upon them," spoke Tom.

Ned did not reply for a moment. Then, as he looked at another piece of a severed cable, he exclaimed:

"Tom, the weight of your gun never broke these."

"What do you mean, Ned?"

"I mean that they were partly filed, or cut through—then the storm and the pressure of the gun did the rest. Look!"

He held out the piece of wire rope. There, on the end, could be seen several strands cleanly severed, as though a file or a hacksaw had been used.

"By Jove!" murmured Tom. He looked about the deck. There was no one near the big gun. "Ned," whispered his chum, "there's something wrong here. It's more of that conspiracy to defeat my aims. Don't say anything about this, and we'll keep our eyes open. We'll do a bit of detective work."

"The scoundrels!" exclaimed Ned. "I wish we knew who they were. General Waller isn't aboard, and what other of the officers has a gun of his own that he would rather see accepted by the government than yours?"

"None that I know of," replied Tom.

"General Waller might have hired someone to—"

"Don't go making any unwarranted charges," warned the young inventor.

"Or perhaps that German, Tom, might—"

"Hush!" cautioned Tom. "Here he comes now," and, as he spoke, General von Brunderger came strolling along the deck.

"I am glad to see that the accident of last night had no serious effects," he said, smiling.

"It was no accident!" burst out Ned.

"No accident? You surprise me. I thought—"

"Oh, Ned means that some of the cables look as though they had been cut," hastily put in Tom, nudging his chum in the ribs as a signal for him to keep quiet.

"The cables cut!" exclaimed the German, and his voice indicated anxious solicitude.

"Or else filed," went on Tom easily, with a warning glance at Ned. "But I dare say they were old cables, that had been used on other work, and may have become frayed. Everything is safe now, though. New cables were lashed on this morning."

"I am glad to hear it. It would be a—er—ah, a national calamity to lose so valuable a gun, and the opening of the canal so near at hand. I am glad that your invention is safe, Herr Swift," and he smiled genially at Tom and Ned.

"What did you shut me off for?" asked Ned, when he and his chum were alone in their stateroom again.

"Because I didn't want you to make any breaks before him," answered Tom.

"Then you suspect—"

"I suspect many things, Ned, but I'm not going to show my hand until I'm ready. I'm going to watch and listen."

"And I'll be with you."

But no further accidents occurred. There were no more storms, no attempt was made to meddle with Tom's powder, and in due season the ship arrived at Colon, and after much labor the great gun, its carriage, the shells and the powder were taken to the barbette at the Gatun locks, designed to admit vessels from the Caribbean Sea into Gatun Lake.

"And now for some more hard work," remarked Tom, as all the needful stores were landed.



CHAPTER XXIII

NEWS OF THE MINE

"Just a little farther over this way, Ned. That's better. Now mark it there, and we'll have it clamped down."

"But can you get enough elevation here, Tom?"

"Oh, yes, I think so. Besides, I've added a few more inches to the lift of the disappearing carriage, and it will send the gun so much farther in the air. I think this will do. Where is Koku?"

"Here I be, Master."

"Just get hold of that small derrick, Koku, and lift up one of the projectiles. I want to see if they come in the right place for the breech before I set the hoisting apparatus permanently."

The giant was soon engaged in winding up the rope of an improvised hoist that stood about in the position the permanent one was to go. From the interior of the barbette, which was, in effect, a bomb-proof structure, there was lifted one of the big projectiles destined to be hurled from Tom Swift's giant cannon.

"Yes, I think that will do," decided the young inventor, as he watched Koku. "Now, Mr. Damon, if you will kindly oversee this part of the work, I'll see if we can't get that motor in better shape. It didn't work worth a cent this morning."

"Bless my rubber coat, Tom, I'll do all I can to help you!" declared the odd man.

"Massa Tom! Massa Tom!" called Eradicate.

"Yes, Rad. What is it?"

"Heah am dem chicken sandwiches, an' some hot coffee fo' yo' all. I done knowed yo' alt wouldn't hab no time t' stop fo' dinnah, so I done made yo' all up a snack."

"That's mighty good of you, Rad," spoke Tom, with a laugh. "I was getting pretty hungry; but I didn't want to stop until I had things moving in better shape. Come on, Ned, let's knock off for a few minutes and take a bite. You, too, Mr. Damon."

As they sat about the place where the gun was being mounted, munching sandwiches and drinking the coffee which the aged colored man had so thoughtfully provided, Eradicate said, with a chuckle:

"By gar! Dey can't git erlong wifout dish yeah coon, arter all! Ha! ha! Dat cocoanut giant he mighty good when it comes t' fastening big guns down so dey won't blow away, but when it comes t' eatin' dey has t' depend on ole Eradicate! Ha! ha! I'se got dat cocoanut giant beat all right!"

"He sure is jealous of Koku," remarked Ned, as Tom and Mr. Damon smiled at the colored man.

"He certainly hit me in the right spot," declared Tom, as he reached for another sandwich.

They had landed from the warship several days before, and from then on there had been hard work and plenty of it. Tom was here, there and everywhere, directing matters so that his gun would be favorably placed.

Some preliminary work had been done before they arrived in the way of preparing a place to mount the gun, and this work was now proceeding. The officers of the ordnance department were in actual charge, but they always deferred to Tom, since he had most at stake.

"It will be some days before you can actually fire your gun; will it not?" asked Ned of his chum, as they finished the lunch, and prepared to resume work.

"Yes—a week at least, I expect. It is taking longer to set up the carriage than I thought. But it will be an improvement over the solid one we formerly used. That was fine, Rad," he concluded as the colored man went back to the shack of which he had taken possession for himself and his cooking operations. It adjoined the quarters to which Tom, Ned, Mr. Damon and Koku had been assigned.

"Golly! I ain't so old yit but what I knows de stuff Massa Tom laiks!" exclaimed the colored man, moving off with a chuckle.

Tom, though he had many suspicions about the cut cables that had nearly been the cause of his gun sliding into the sea, had learned nothing definite—nor had Ned.

The German officer, with his body servant, who seldom spoke, had landed at Colon, and was proceeding to make himself at home with the officers and men who were building the canal. Occasionally he paid a visit to Tom and Ned, where they were engaged about the big gun. He always seemed pleasant, and interested in their labors, asking many question, but that was all, and our hero began to feel that perhaps he was wrong in his suspicions.

As for Ned, he veered uncertainly from one suspicion to another. At one time he declared that von Brunderger and General Waller were in a conspiracy to upset Tom's plans. Again he would accuse the German alone, until Tom laughingly bade him attend more to work and less to theories.

Slowly the work progressed. The gun was mounted after much labor, and then arrangements began to be made for the test. A series of shots were to be fired out to sea, and the proper precautions were to be taken to prevent any ships from being struck.

"Though if you intend to send a projectile thirty miles," said one of the officers, "I'm afraid there may be some danger, after all. Are you sure you have a range of thirty miles, Mr. Swift?"

"I have," answered Tom, calmly, "and with the increased elevation that I am able to get here, it may exceed that."

The officer said nothing, but he looked at Tom in what our hero thought was a peculiar manner.

A few days before the date set for the test one of the sentinels, who had been detailed to keep curiosity-seekers away from the giant cannon, approached Tom and said:

"There is a gentleman asking to see you, Mr. Swift."

"Who is it?" asked Tom, laying aside a pressure gauge he intended attaching to the gun.

"He says his name is Peterson—Alec Peterson. Do you want to see him?"

"Yes, let him come up," directed the young inventor. "Do you hear that, Ned?" he called. "Our fortune-hunting friend is here."

"Maybe he's found that lost opal mine," suggested Ned.

"I hope he has, for dad's sake," went on Tom. "Hello, Mr. Peterson!" he called, as he noticed the old prospector coming along. "Have you had any luck?"

"I heard you were down here," said the many not answering the question directly, "and as I had to run over from my island for some supplies I thought I'd stop and see you. How are you?" and he shook hands.

"Fine!" answered Tom. "Have you found the lost mine yet?"

Alec Peterson paused a moment. Then he said slowly:

"No, Tom, I haven't succeeded in locating the mine yet. But I—I expect to any day now!" he added, hastily.



CHAPTER XXIV

THE LONGEST SHOT

"Well, Mr. Peterson," remarked Tom, after a pause, "I'm sure I hope you will succeed in your quest. You must have met disappointment so far."

"I have, Tom. But I'm not going to give up. Can't you come over and see me before you go back North?"

"I'll try. Just where is your island?"

"Off in that direction," responded the fortune-hunter, pointing to the northeast. "It's a little farther from here than I thought it was at first—about thirty miles. But I have a little second-hand steam launch that my pardners and I use. I'll come for you, take you over and bring you back any time you say."

"After my gun has been tested," said Tom, with a smile. "Better stay and see it."

"No, I must get back to the island. I have some new information that I am sure will enable me to locate the lost mine."

"Well, good-bye, and good luck to you," called Tom, as the fortune-hunter started away.

"Do you think he'll ever find the opals, Tom?" asked Ned.

His chum shook his head.

"I don't believe so," he answered. "Alec has always been that way—always visionary—always just about to be successful; but never quite getting there."

"Then your father's ten thousand dollars will be lost?"

"Yes, I suppose so; but, in a way, dad can stand it. And if I make good on this gun test, ten thousand dollars won't look very big to me. I guess dad gave it to Alec from a sort of sentimental feeling, anyhow."

"You mean because he saved you from the live wire?"

"That's it, Ned. It was a sort of reward, in a way, and I guess dad won't be broken-hearted if Alec doesn't succeed. Only, of course, he'll feel badly for Alec himself. Poor old man! he won't be able to do much more prospecting. Well, Ned, let's get to work on that ammunition hoist. It still jams a little on the ways, and I want it to work smoothly. There's no use having a hitch—even a small one—when the big bugs assemble to see how my cannon shoots."

"That's right, Tom. Well, start off, I'm with you."

The two youths labored for some time, being helped, of course, by the workmen provided by the government, and some from the steel concern.

There were many little details to look after, not the least of which was the patrolling of the stretch of ocean over which the great projectiles would soar in reaching the far-off targets at which Tom had planned to shoot. No ships were to be allowed to cross the thirty-mile mark while the firing was in progress. So, also, the zone where the shots were expected to fall was to be cleared.

But at last all seemed in readiness. The gun had been tried again and again on its carriage. The projectiles were all in readiness, and the terribly powerful ammunition had been stored below the gun in a bomb-proof chamber, ready to be hoisted out as needed.

Because the gun had been fired so many times with a charge of powder heavier than was ordinarily called for, and had stood the strain well, Tom had no fear of standing reasonably close to it to press the button of the battery. There would be no retreating to the bombproof this time.

The German officer was occasionally seen about the place where the gun was mounted, but he appeared to take only an ordinary interest in it. Tom began to feel more than ever that perhaps his suspicions were unfounded.

Some officials high in government affairs had arrived at Colon in anticipation of the test, which, to Tom's delight, had attracted more attention than he anticipated. At the same time he was a bit nervous.

"Suppose it fails, Ned?" he said.

"Oh, it can't!" cried his chum. "Don't think about such a thing."

Plans had been made for a ship to be stationed near the zone of fire, to report by wireless the character of each shot, the distance it traveled, and how near it came to the target. The messages would be received at a station near the barbette, and at once reported to Tom, so that he would know how the test was progressing.

"Well, today tells the tale!" exclaimed the young inventor, as he got up one morning. "How's the weather, Ned?"

"Couldn't be better—clear as a bell, Tom."

"That's good. Well, let's have grub, and then go out and see how my pet is."

"Oh, I guess nothing could happen, with Koku on guard."

"No, hardly. I'm going to keep him in the ammunition room until after the test, too. I'm going to take no chances."

"That's the ticket!"

The gun was found all right, in its great tarpaulin cover, and Tom had the latter taken off that he might go over every bit of mechanism. He made a few slight changes, and then got ready for the final trials.

On an improvised platform, not too near the giant cannon, had gathered the ordnance board, the specially invited guests, a number of officers and workers in the canal zone, and one or two representatives of foreign governments. Von Brunderger was there, but his "familiar," as Ned had come to call the stolid German servant, was not present.

Tom took some little time to explain, modestly enough, the working of his gun. A number of questions were asked, and then it was announced that the first shot, with only a practice charge of powder, would be fired.

"Careful with that projectile now. That's it, slip it in carefully. A little farther forward. That's better. Now the powder—Koku, are you down there?" and Tom called down the tube into the ammunition chamber.

"Me here, Master," was the reply.

"All right, send up a practice load."

Slowly the powerful explosive came up on the electric hoist. It was placed in the firing chamber and the breech dosed.

"Now, gentlemen," said Tom, "this is not a shot for distance. It is merely to try the gun and get it warmed up, so to speak, for the real tests that will follow. All ready?"

"All ready!" answered Ned, who was acting as chief assistant.

"Here she goes!" cried Tom, and he pressed the button.

Many were astonished by the great report, but Tom and the others, who were used to the service charges, hardly noticed this one. Yet when the wireless report came in, giving the range as over fourteen thousand yards, there was a gasp of surprise.

"Over eight miles!" declared one grizzled officer; "and that with only a practice charge. What will happen when he puts in a full one?'

"I don't know," answered a friend.

Tom soon showed them. Quickly he called for another projectile, and it was inserted in the gun. Then the powder began to come up the hoist. Meanwhile the young inventor had assured himself that the gun was all right. Not a part had been strained.

This time, when Tom pressed the button there was such a tremendous concussion that several, who were not prepared for it, were knocked back against their neighbors or sent toppling off their chairs or benches. And as for the report, it was so deafening that for a long time after it many could not hear well.

But Tom, and those who knew the awful power of the big cannon, wore specially prepared eardrum protectors, that served to reduce the shock.

"What is it?" called Tom to the wireless operator, who was receiving the range distance from the marking ship.

"A little less than twenty-nine miles."

"We must do better than that," said Tom. "I'll use more powder, and try one of the newer shells. I'll elevate the gun a trifle, too."

Again came that terrific report, that trembling of the ground, that concussion, that blast of air as it rushed in to fill the vacuum caused, and then the vibrating echoes.

"I think you must have gone the limit this time, Tom!" yelled Ned, as he turned on the compressed air to blow the powder fumes and unconsumed bits of explosive from the gun tube.

"Possibly," admitted Tom. "Here comes the report." The wireless operator waved a slip of paper.

"Thirty-one miles!" he announced.

"Hurray!" cried Mr. Damon. "Bless my telescope! The longest shot on record!"

"I believe it is," admitted the chief of the ordnance department. "I congratulate you, Mr. Swift."

"I think I can do better than that," declared Tom, after looking at the various recording gauges, and noting the elevation of the gun. "I think I can get a little flatter trajectory, and that will give a greater distance. I'm going to try."

"Does that mean more powder, Tom?" asked Ned.

"Yes, and the heaviest shell we have—the one with the bursting charge. I'll fire that, and see what happens. Tell the zone-ship to be on the lookout," he said to the wireless operator, giving a brief statement of what he was about to attempt.

"Isn't it a risk, Tom?" his chum asked.

"Well, not so much. I'm sure my cannon will stand it. Come on now, help me depress the muzzle just a trifle," and by means of the electric current the big gun was raised at the breech a few inches.

As is well known, cannon shots do not go in straight lines. They leave the muzzle, curve upward and come down on another curve. It is this curve described by the projectile that is called the trajectory. The upward curve, as you all know, is caused by the force of the powder, and the downward by the force of gravitation acting on the shot as soon as it reaches its zenith. Were it not for this force the projectiles could be fired in straight lines. But, as it is, the cannon has to be elevated to send the shot up a bit, or it would fall short of its mark.

Consequently, the flatter the trajectory the farther it will go. Tom's object, then, was to flatten the trajectory, by lowering the muzzle of the gun, in order to attain greater distance.

"If this doesn't do the trick, we'll try it with the muzzle a bit lower, and with a trifle more powder," he said to Ned, as he was about to fire.

The young inventor was not a little nervous as he prepared to press the button this time. It was a heavier charge than any used that day, though the same quantity had been fired on other occasions with safety. But he was not going to hesitate.

Coincident with the pressure of Tom's fingers there seemed to be a veritable earthquake. The ground swayed and rocked, and a number of the spectators staggered back. It was like the blast of a hundred thunderbolts. The gun shook as it recoiled from the shock, but the wonderful disappearing carriage, fitted with coiled, pneumatic and hydrostatic buffers, stood the strain.

Following the awful report, the terrific recoil and the howl of the wind as it rushed into the vacuum created, there was an intense silence. The projectile had been seen by some as a dark speck, rushing through the air like a meteor. Then the wireless operator could be seen writing down a message, the telephone-like receivers clamped over his ears.

"Something happened, all right!" he called aloud. "That shot hit something."

"Not one of the ships!" cried Tom, aghast.

"I don't know. There seems to be some difficulty in transmitting. Wait—I'm getting it: now."

As he ceased speaking there came from underneath the great gun the sound of confused shouts. Tom and Ned recognized Koku's voice protesting:

"No—no—you can't come in here! Master said no one was to come in."

"What is it, Koku?" yelled Tom, springing to the speaking tube connecting with the powder magazine, at the same time keeping an eye on the wireless operator. Tom was torn between two anxieties.

"Someone here, Master!" cried the giant. "Him try to fix powder. Ah, I fix you!" and with a savage snarl the giant, in the concrete chamber below, could be heard to attack someone who cried out gutturally in German:

"Help! Help! Help!"

"Come on, Ned!" cried Tom, making a dash for the stairs that led into the magazine. There was confusion all about, but through it all the wireless operator continued to write down the message coming to him through space.

"What is it, Koku? What is it?" cried Tom, plunging down into the little chamber.

As he reached it, a door leading to the outer air flew open, and out rushed a man, badly torn as to his clothes, and scratched and bleeding as to his face. On he ran, across the space back of the barbette, toward the lower tier of seats that had been erected for the spectators.

"It's von Brunderger's servant!" gasped Ned, recognizing the fellow.

"What did he do, Koku?" demanded the young inventor.

"Him sneak in here—have some of that stuff you call 'dope.' I sent up powder, and I come back here to see him try to put some dope in Master's ammunition."

"The scoundrel!" cried Tom. "They're trying to break me, even at the last minute! Come on, Ned."

They raced outside to behold a curious sight. Straight toward von Brunderger rushed the man as if in a frenzy of fear. He called out something in German to his master, and the latter's face went first red, then white. He was observed to look about quickly, as though in alarm, and then, with a shout at his servant, the German officer rushed from the stand, and the two disappeared in the direction of the barracks.

"What does it mean?" cried Ned.

"Give it up," answered Tom, "except that Koku spoiled their trick, whatever it was. It looks as if this was the end of it, and that the mystery has been cleared up."

"Mr. Swift! Where's Mr. Swift?" shouted the wireless operator. "Where are you?"

"Yes; what is it?" demanded Tom, so excited that he hardly knew what he was doing.

"The longest shot on record!" cried the man. "Thirty-three miles, and it struck, exploded, and blew the top off a mountain on an island out there!" and he pointed across the sun-lit sea.



CHAPTER XXV

THE LONG-LOST MINE

There was a silence after the inspiring words of the operator, and then it seemed that everyone began to talk at once. The record-breaking shot, the effect of it and the struggle that had taken place in the powder room, together with the flight of von Brunderger and his servant, gave many subjects for excited conversation.

"I've got to get at the bottom of this!" cried Tom, making his way through the press of officials to where the wireless operator stood. "Just repeat that," requested Tom, and they all gave place for him, waiting for the answer.

The operator read the message again.

"Thirty-three miles!" murmured Tom. "That is better than I dared to hope. But what's that about blowing the top off an island?"

"That's what you did, with that explosive shell, Mr. Swift. The operator on the firing-zone ship saw the top fly off when the shell struck. The ship was about half a mile away, and when they heard that shell coming the officers thought it was all up with them. But, instead, it passed over them and demolished the top of the mountain.

"Anybody hurt?" asked Tom, anxiously.

"No, it was an uninhabited island. But you have made the record shot, all right. It went farther than any of the others."

"Then I suppose I ought to be satisfied," remarked Tom, with a smile.

"What was that disturbance, Mr. Swift?" asked the chief ordnance officer, coming forward.

"I don't understand it myself," replied the young inventor. "It appeared that someone went into the ammunition room, and Koku, my giant servant, attacked him."

"As he had a right to do. But who was the intruder?"

"Herr von Brunderger's man."

"Ha! That German officer's! Where is he, he must explain this."

But Herr von Brunderger was not to be found, nor was his man in evidence. They had fled, and when a search was made of their rooms, damaging evidence was found. Before a board of investigating officers Koku told his story, after the gun tests had been declared off for the day, they having been most satisfactory.

The German officer's servant, it appeared, had managed to gain entrance to the ammunition chamber by means of a false key to the outer door. There were two entrances, the other being from the top of the platform where the cannon rested. Koku had seen him about to throw something into one of the ammunition cases, and had grappled with him. There was a fight, and, in spite of the giant's strength, the man had slipped away, leaving part of his garments in the grasp of Koku.

An investigation of some of the powder showed that it had been covered with a chemical that would have made it explode prematurely when placed in the gun. It would probably have wrecked the cannon by blowing out the breech block, and might have done serious damage to life as well as property.

"But what was the object?" asked Ned.

"To destroy Tom's gun," declared Mr. Damon.

"Why should von Brunderger want to do that?"

They found the answer among his papers. He had been a German officer of high rank, but had been dismissed from the secret service of his country for bad conduct. Then, it appeared, he thought of the plan of doing some damage to a foreign country in order to get back in the good graces of his Fatherland.

He forged documents of introduction and authority, and was received with courtesy by the United States officials. In some way he heard of Tom's gun, and that it was likely to be so successful that it would be adopted by the United States government. This he wanted to prevent, and he went to great lengths to accomplish this. It was he, or an agent of his, who forged the letter of invitation to General Waller, and who first tried to spoil Tom's test by doping the powder through Koku.

Later he tried other means, sending a midnight visitor to Tom's house and even going to the length of filing the cables in the storm, so the gun would roll off the warship into the sea. All this was found set down in his papers, for he kept a record of what he had done in order to prove his case to his own government. It was his servant who tried to get near the gun while it was being cast.

That he would be restored to favor had he succeeded, was an open question, though with Germany's friendliness toward the United States it is probable that his acts would have been repudiated. But he was desperate.

Failing in many attempts he resolved on a last one. He sent his servant to the ammunition room to "dope" the powder, hoping that, at the next shot, the gun would be mined. Perhaps he hoped to disable Tom. But the plot failed, and the conspirators escaped. They were never heard of again, probably leaving Panama under assumed names and in disguise.

"Well, that explains the mystery," said Tom to Ned a few days later. "I guess we won't have to worry any more."

"No, and I'm sorry I suspected General Waller."

"Oh, well, he'll never know it, so no harm is done. Oh, but I'm glad this is over. It has gotten on my nerves."

"I should say so," agreed Ned.

"Bless my pillow sham!" cried Mr. Damon. "I think I can get a good night's sleep now. So they have formally accepted your giant cannon, Tom?"

"Yes. The last tests I gave them, showing how easily it could be manipulated, convinced them. It will be one of the official defense guns of the Panama Canal."

"Good! I congratulate you, my boy!" cried the odd man. "And now, bless my postage stamp, let's get back to the United States."

"Before we go," suggested Ned, "let's go take a look at that island from which Tom blew the top. It must be quite a sight—and thirty-three miles away! We can get a launch and go out."

But there was no need. That same day Alec Peterson came to Colon inquiring for Tom. His face showed a new delight.

"Why," cried Tom, "you look as though you had found your opal mine."

"I have!" exclaimed the fortune-hunter. "Or, rather, Tom, I think I have you to thank for finding it for me."

"Me find it?"

"Yes. Did you hear about the top of the island-mountain you blew to pieces?"

"We did, but—"

"That was my island!" exclaimed Mr. Peterson. "The mine was in that mountain, but an earthquake had covered it. I should never have found it but for you. That shot you accidentally fired ripped the mountain apart. My men and I were fortunately at the base of it then, but we sure thought our time had come when that shell struck. It went right over our heads. But it did the business, all right, and opened up the old mine. Tom, your father won't lose his money, we'll all be rich. Oh, that was a lucky shot! I knew it was your cannon that did it."

"I'm glad of it!" answered the young inventor, heartily. "Glad for your sake, Mr. Peterson."

"You must come and see the mine—your mine, Tom, for it never would have been rediscovered had it not been for your giant cannon, that made the longest shot on record, so I'm told."

"We will come, Mr. Peterson, just as soon as I close up matters here."

It did not take Tom long to do this. His type of cannon was formally accepted as a defense for the Panama Canal, and he received a fine contract to allow that type to be used by the government. His powder and projectiles, too, were adopted.

Then, one day, he and Ned, with Koku and Mr. Damon, visited the scene of the great shot. As Mr. Peterson had said, the whole top of the mountain had been blown off by the explosive shell, opening up the old mine. While it was not quite as rich as Mr. Peterson had glowingly painted, still there was a fortune in it, and Mr. Swift got back a substantial sum for his investment.

"And now for the good old U. S. A.!" cried Tom, as they got ready to go back home. "I'm going to take a long rest, and the only thing I'm going to invent for the next six months is a new potato slicer." But whether Tom kept his words can be learned by reading the next volume of this series.

"Bless my hand towel!" cried Mr. Damon. "I think you are entitled to a rest, Tom."

"That's what I say," agreed Ned.

"I'll take care ob him—I'll take care ob Massa Tom," put in Eradicate, as he cast a quick look at Koku. "Giants am all right fo' cannon wuk, but when it comes t' comforts Massa Tom gwine t' 'pend on ole 'Radicate; ain't yo' all, Massa Tom?"

"I guess so, Rad!" exclaimed the young inventor, with a laugh. "Is dinner ready?"

"It suah am, Massa Tom, an' I 'specially made some oh dat fricasseed chicken yo' all does admire so much. Plenty of it, too, Massa Tom."

"That's good, Rad," put in Ned. "For we'll all be hungry after that trip to the island. That sure was a great shot Tom—thirty-three miles!"

"Yes, it went farther than I thought it would," replied Tom. And now, as they are taking a closing meal at Panama, ready to return to the United States, we will take leave of Tom Swift and his friends.

THE END