TOM SWIFT AND HIS GIANT CANNON

or

The Longest Shots on Record

by

Victor Appleton



CONTENTS

CHAPTER

I ON A LIVE WIRE II "WE'LL TAKE A CHANCE!" III PLANNING A BIG GUN IV KOKU'S BRAVE ACT V OFF TO SANDY HOOK VI TESTING THE WALLER GUN VII THE IMPOSSIBLE OCCURS VIII A BIG PROBLEM IX THE NEW POWDER X SOMETHING WRONG XI FAILURE AND SUCCESS XII A POWERFUL BLAST XIII CASTING THE CANNON XIV A NIGHT INTRUDER XV READY FOR THE TEST XVI A WARNING XVII THE BURSTING DAM XVIII THE DOPED POWDER XIX BLOWING DOWN THE BARRIER XX THE GOVERNMENT ACCEPTS XXI OFF FOR PANAMA XXII AT GATUN LOCKS XXIII NEWS OF THE MINE XXIV THE LONGEST SHOT XXV THE LONG-LOST MINE



TOM SWIFT AND HIS GIANT CANNON



CHAPTER I

ON A LIVE WIRE

"Now, see here, Mr. Swift, you may think it all a sort of dream, and imagine that I don't know what I'm talking about; but I do! If you'll consent to finance this expedition to the extent of, say, ten thousand dollars, I'll practically guarantee to give you back five times that sum."

"I don't know, Alec, I don't know," slowly responded the aged inventor. "I've heard those stories before, and in my experience nothing ever came of them. Buried treasure, and lost vessels filled with gold, are all well and good, but hunting for an opal mine on some little-heard-of island goes them one better."

"Then you don't feel like backing me up in this matter, Mr. Swift?"

"No, Alec, I can't say I do. Why, just stop and think for a minute. You're asking me to put ten thousand dollars into a company, to fit out an expedition to go to this island—somewhere down near Panama, you say it is—and try to locate the lost mine from which, some centuries ago, opals and other precious stones came. It doesn't seem reasonable."

"But I'm sure I can find the mine, Mr. Swift!" persisted Alec Peterson, who was almost as elderly a man as the one he addressed. "I have the old documents that tell how rich the mine once was, how the old Mexican rulers used to get their opals from it, and how all trace of it was lost in the last century. I have all the landmarks down pat, and I'm sure I can find it. Come on now, take a chance. Put in this ten thousand dollars. I can manage the rest. You'll get back more than five times your investment."

"If you find the mine—yes."

"I tell you I will find it! Come now, Mr. Swift," and the visitor's voice was very pleading, "you and your son Tom have made a fortune for yourselves out of your different inventions. Be generous, and lend me this ten thousand dollars."

Mr. Swift shook his head.

"I've heard you talk the same way before, Alec," he replied. "None of your schemes ever amounted to anything. You've been a fortune-hunter all your life, nearly; and what have you gotten out of it? Just a bare living."

"That's right, Mr. Swift, but I've had bad luck. I did find the lost gold mine I went after some years ago, you remember."

"Yes, only to lose it because the missing heirs turned up, and took it away from you. You could have made more at straight mining in the time you spent on that scheme."

"Yes, I suppose I could; but this is going to be a success—I feel it in my bones."

"That's what you say, every time, Alec. No, I don't believe I want to go into this thing."

"Oh, come—do! For the sake of old times. Don't you recall how you and I used to prospect together out in the gold country; how we shared our failures and successes?"

"Yes, I remember that, Alec. Mighty few successes we had, though, in those days."

"But now you've struck it rich, pardner," went on the pleader. "Help me out in this scheme—do!"

"No, Alec. I'd rather give you three or four thousand dollars for yourself, if you'd settle down to some steady work, instead of chasing all over the country after visionary fortunes. You're getting too old to do that."

"Well, it's a fact I'm no longer young. But I'm afraid I'm too old to settle down. You can't teach an old dog new tricks, pardner. This is my life, and I'll have to live it until I pass out. Well, if you won't, you won't, I suppose. By the way, where is Tom? I'd like to see him before I go back. He's a mighty fine boy."

"That's what he is!" broke in a new voice. "Bless my overshoes, but he is a smart lad! A wonderful lad, that's what! Why, bless my necktie, there isn't anything he can't invent; from a button-hook to a battleship! Wonderful boy—that's what!"

"I guess Tom's ears would burn if he could hear your praises, Mr. Damon," laughed Mr. Swift. "Don't spoil him."

"Spoil Tom Swift? You couldn't do it in a hundred years!" cried Mr. Damon, enthusiastically. "Bless my topknot! Not in a thousand years—no, sir!"

"But where is he?" asked Mr. Peterson, who was evidently unused to the extravagant manner of Mr. Damon.

"There he goes now!" exclaimed the gentleman who frequently blessed himself, some article of his apparel, or some other object. "There he goes now, flying over the house in that Humming Bird airship of his. He said he was going to try out a new magneto he'd invented, and it seems to be working all right. He said he wasn't going to take much of a flight, and I guess he'll soon be back. Look at him! Isn't he a great one, though!"

"He certainly is," agreed Mr. Peterson, as he and Mr. Swift went to the window, from which Mr. Damon had caught a glimpse of the youthful Inventor in his airship. "A great lad. I wish he could come on this mine-hunt with me, though I'd never consent to go in an airship. They're too risky for an old man like me."

"They're as safe as a church when Tom Swift runs them!" declared Mr. Damon. "I'm no boy, but I'd go anywhere with Tom."

"I'm afraid you wouldn't get Tom to go with you, Alec," went on Mr. Swift, as he resumed his chair, the young inventor in his airship having passed out of sight. "He's busy on some new invention now, I believe. I think I heard him say something about a new rifle."

"Cannon it was, Mr. Swift," said Mr. Damon. "Tom has an idea that he can make the biggest cannon in the world; but it's only an idea yet."

"Well, then I guess there's no hope of my interesting him in my opal mine," said the fortune-hunter, with rather a disappointed smile. "Nor you either, Mr. Swift."

"No, Alec, I'm afraid not. As I said, I'd rather give you outright three or four thousand dollars, if you wanted it, provided that you used it for your own personal needs, and promised not to sink it in some visionary search."

Mr. Peterson shook his head.

"I'm not actually in want," he said, "and I couldn't accept a gift of money, Mr. Swift. This is a straight business proposition."

"Not much straight business in hunting for a mine that's been lost for over a century," replied the aged inventor, with a glance at Mr. Damon, who was still at the window, watching for a glimpse of Tom on his return trip in the air craft.

"If Tom would go, I'd trail along," said the odd man. "We haven't done anything worth speaking of since he used his great searchlight to detect the smugglers. But I don't believe he'll go. That mining proposition sounds good."

"It is good!" cried Mr. Peterson, with fervor, hoping he had found a new "prospect" in Mr. Damon.

"But not business-good," declared Mr. Swift, and for some time the three argued the matter, Mr. Swift continuing to shake his head.

Suddenly into the room there ran an aged colored man, much excited.

"Fo' de land sakes!" he cried. "Somebody oughter go out an' help Massa Tom!"

"Why, what's the matter, Eradicate?" asked Mr. Swift, leaping to his feet, an example followed by the other two men. "What has happened to my son?"

"I dunno, Massa Swift, but I looked up jest now, an' dere he be, in dat air-contraption ob his'n he calls de Hummin' Burd. He's ketched up fast on de balloon shed roof, an' dere he's hangin' wif sparks an' flames a-shootin' outer de airship suffin' scandalous! It's jest spittin' fire, dat's what it's a-doin', an' ef somebody don't do suffin' fo' Massa Tom mighty quick, dere ain't gwin t' be any Massa Tom; now dat's what I'se a-tellin' you!"

"Bless my shoe buttons!" gasped Mr. Damon. "Come on out, everybody! We've got to help Tom!"

"Yes!" assented Mr. Swift. "Call someone on the telephone! Get a doctor! Maybe he's shocked! Where's Koku, the giant? Maybe he can help!"

"Now doan't yo' go t' gittin' all excited-laik," objected Eradicate Sampson, the aged colored man. "Remember yo' all has got a weak heart, Massa Swift!"

"I know it; but I must save my son. Hurry!"

Mr. Swift ran from the room, followed by Mr. Damon and Mr. Peterson, while Eradicate trailed after them as fast as his tottering limbs would carry him, murmuring to himself.

"There he is!" cried Mr. Damon, as he caught sight of the young inventor in his airship, in a position of peril. Truly it was as Eradicate had said. Caught on the slope of the roof of his big balloon shed, Tom Swift was in great danger.

From his airship there shot dazzling sparks, and streamers of green and violet fire. There was a snapping, cracking sound that could be heard above the whir of the craft's propellers, for the motor was still running.

"Oh, Tom! Tom! What is it? What has happened?" cried his father.

"Keep back! Don't come too close!" yelled the young inventor, as he clung to the seat of the aeroplane, that was tilted at a dangerous angle. "Keep away!"

"What's the matter?" demanded Mr. Damon. "Bless my pocket comb—what is it?"

"A live wire!" answered Tom. "I'm caught in a live wire! The trailer attached to the wireless outfit on my airship is crossed with the wire from the power plant. There's a short circuit somewhere. Don't come too close, for it may burn through any second and drop down. Then it will twist about like a snake!"

"Land ob massy!" cried Eradicate.

"What can we do to help you?" called Mr. Swift. "Shall I run and shut off the power?" for in the shop where Tom did most of his inventive work there was a powerful dynamo, and it was on one of the wires extending from it, that brought current into the house, that the craft had caught.

"Yes, shut it off if you can!" Tom shouted back. "But be careful. Don't get shocked! Wow! I got a touch of it myself that time!" and he could be seen to writhe in his seat.

"Oh, hurry! hurry! Find Koku!" cried Mr. Swift to Mr. Damon, who had started for the power house on the run.

The sparks and lances of fire seemed to increase around the young inventor. The airship could be seen to slip slowly down the sloping roof.

"Land ob massy! He am suah gwine t' fall!" yelled Eradicate.

"Oh, he'll never get that current shut off in time!" murmured Mr. Swift, as he started after Mr. Damon.

"Wait! I think I have a plan!" called Mr. Peterson. "I think I can save Tom!"

He did not waste further time in talk, but, running to a nearby shed, he got a long ladder that he saw standing under it. With this over his shoulder he retraced his steps to the balloon hangar and placed the ladder against the side. Then he started to climb up.

"What are you going to do?" yelled Tom, leaning over from his seat to watch the elderly fortune-hunter.

"I'm going to cut that wire!" was the answer.

"Don't! If you touch it you'll be shocked to death! I may be able to get out of here. So far I've only had light shocks, but the insulation is burning out of my magneto, and that will soon stop. When it does I can't run the motor, and—"

"I'm going to cut that wire!" again shouted Mr. Peterson.

"But you can't, without pliers and rubber gloves!" yelled Tom. "Keep away, I tell you!"

The man on the ladder hesitated. Evidently he had not thought of the necessity of protecting his hands by rubber covering, in order that the electricity might be made harmless. He backed down to the ground.

"I saw a pair of old gloves in the shed!" he cried. "I'll get them—they look like rubber."

"They are!" cried Tom, remembering now that he had been putting up a new wire that day, and had left his rubber gloves there. "But you haven't any pliers!" the lad went. "How can you cut wire without them? There's a pair in the shop, but—"

"Heah dey be! Heah dey be!" cried Eradicate, as he produced a heavy pair from his pocket. "I—I couldn't find de can-opener fo' Mrs. Baggert, an' I jest got yo' pliers, Massa Tom. Oh, how glad I is dat I did. Here's de pincers, Massa Peterson."

He handed them to the fortune-hunter, who came running back with the rubber gloves. Mr. Damon was no more than half way to the power house, which was quite a distance from the Swift homestead. Meanwhile Tom's airship was slipping more and more, and a thick, pungent smoke now surrounded it, coming from the burning insulation. The sparks and electrical flames were worse than ever.

"Just a moment now, and I'll have you safe!" cried the fortune-hunter, as he again mounted the ladder. Luckily the charged wire was near enough to be reached by going nearly to the top of the ladder.

Holding the pincers in his rubber-gloved hands, the old man quickly snipped the wire. There was a flash of sparks as the copper conductor was severed, and then the shower of sparks about Tom's airship ceased.

In another second he had turned on full power, the propellers whizzed with the quickness of light, and he rose in the air, off the shed roof, the live wire no longer entangling him. Then he made a short circuit of the work-shop yard, and came to the ground safely a little distance from the balloon hangar.

"Saved! Tom is saved!" cried Mr. Swift, who had seen the act of Mr. Peterson from a distance. "He saved my boy's life!"

"Thanks, Mr. Peterson!" exclaimed the young inventor, as he left his seat and walked up to the fortune-hunter. "You certainly did me a good turn then. It was touch and go! I couldn't have stayed there many seconds longer. Next time I'll know better than to fly with a wireless trailer over a live conductor," and he held out his hand to Mr. Peterson.

"I'm glad I could help you, Tom," spoke the other, warmly. "I was afraid that if you had to wait until they shut off the power it would be too late."

"It would—it would—er—I feel—I—"

Tom's voice trailed off into a whisper and he swayed on his feet.

"Cotch him!" cried Eradicate. "Cotch him! Massa Tom's hurt!" and only just in time did Mr. Peterson clutch the young inventor in his arms. For Tom, white of face, had fallen back in a dead faint.



CHAPTER II

"WE'LL TAKE A CHANCE!"

"Carry him into the house!" cried Mr. Swift, as he came running to where Mr. Peterson was loosening Tom's collar.

"Git a doctor!" murmured Eradicate. "Call someone on de tellifoam! Git fo' doctors!"

"We must get him into the house first," declared Mr. Damon, who, seeing that Tom was off the shed roof, had stopped mid-way to the powerhouse, and retraced his steps. "Let's carry him into the house. Bless my pocketbook! but he must have been shocked worse than he thought."

They lifted the inert form of our hero and walked toward the mansion with him, Mrs. Baggert, the housekeeper, standing in the doorway in dismay, uncertain what to do.

And while Tom is being cared for I will take just a moment to tell my new readers something more about him and his inventions, as they have been related in the previous books of this series.

The first volume was called "Tom Swift and His Motor-Cycle," and this machine was the means of his becoming acquainted with Mr. Wakefield Damon, the odd gentleman who so often blessed things. On his motor-cycle Tom had many adventures.

The lad was of an inventive mind, as was his father, and in the succeeding books of the series, which you will find named in detail elsewhere, I related how Tom got a motorboat, made an airship, and later a submarine, in all of which craft he had strenuous times and adventures.

His electric runabout was quite the fastest car on the road, and when he sent his wonderful wireless message he saved himself and others from Earthquake Island. He solved the secret of the diamond makers, and, though he lost a fine balloon in the caves of ice, he soon had another air craft—a regular sky-racer. His electric rifle saved a party from the red pygmies in Elephant Land, and in his air glider he found the platinum treasure. With his wizard camera, Tom took wonderful moving pictures, and in the volume immediately preceding this present one, called "Tom Swift and His Great Searchlight," I had the pleasure of telling you how the lad captured the smugglers who were working against Uncle Sam over the border.

Tom, as you will see, had, with the help of his father, perfected many wonderful inventions. The lad lived with his aged parent, his mother being dead, in the village of Shopton, in New York State.

While the house, which was presided over by the motherly Mrs. Baggert, was large, it was almost lost now amid the many buildings surrounding it, from balloon and airship hangars, to shops where varied work was carried on. For Tom did most of his labor himself, of course with men to help him at the heavier tasks. Occasionally he had to call on outside shops.

In the household, beside his father, himself and Mrs. Baggert, was Eradicate Sampson, an aged colored man-of-all-work, who said he was called "Eradicate" because he eradicated dirt. There was also Koku, a veritable giant, one of two brothers whom Tom had brought with him from Giant Land, when he escaped from captivity there, as related in the book of that name.

Mr. Damon was, with Ned Newton, Tom's chum, the warmest friend of the family, and was often at Tom's home, coming from the neighboring town of Waterford, where he lived.

Tom had been back some time now from working for the government in detecting the smugglers, but, as you may well suppose, he had not been idle. Inventing a number of small things, including useful articles for the house, was a sort of recreation for him, but his mind was busy on one great scheme, which I will tell you about in due time.

Among other things he had just perfected a new style of magneto for one of his airships. The magneto, as you know, is a sort of small dynamo, that supplies the necessary spark to the cylinder, to explode the mixture of air and gasoline vapor. He was trying out this magneto in the Humming Bird when the accident I have related in the first chapter occurred.

"There! He's coming to!" exclaimed Mrs. Baggert, as she leaned over Tom, who was stretched out on the sofa in the library. "Give him another smell of this ammonia," she went on, handing the bottle to Mr. Swift.

"No—no," faintly murmured Tom, opening his eyes. "I—I've had enough of that, if you please! I'm all right."

"Are you sure, Tom?" asked his father. "Aren't you hurt anywhere?"

"Not a bit, Dad! It was foolish of me to go off that way; but I couldn't seem to help it. It all got black in front of me, and—well, I just keeled over."

"I should say you did," spoke Mr. Peterson.

"An' ef he hadn't a-been there to cotch yo' all," put in Eradicate, "yo' all suah would hab hit de ground mighty hard."

"That's two services he did for me today," said Tom, as he managed to sit up. "Cutting that wire—well, it saved my life, that's certain."

"I believe you, Tom," said Mr. Swift, solemnly, and he held out his hand to his old mining partner.

"Do you need the doctor?" asked Mr. Damon, who was at the telephone. "He says he'll come right over—I can get him in Tom's electric runabout, if you say so. He's on the wire now."

"No, I don't need him," replied the young inventor. "Thank him just the same. It was only an ordinary faint, caused by the slight electrical shocks, and by getting a bit nervous, I guess. I'm all right—see," and he proved it by standing up.

"He's ail right—don't come, doctor," said Mr. Damon into the telephone. "Bless my keyring!" he exclaimed, "but that was a strenuous time!"

"I've been in some tight places before," went on Tom, as he sat down in an easy chair, "and I've had any number of shocks when I've been experimenting, but this was a sort of double combination, and it sure had me guessing. But I'm feeling better every minute."

"A cup of hot tea will do you good," said motherly Mrs. Baggert, as she bustled out of the room. "I'll make it for you."

"You cut that wire as neatly as any lineman could," went on Tom, glancing from Mr. Peterson out of the window to where one of his workmen was repairing the break. "When I flew over it in my airship I never gave a thought to the trailer from my wireless outfit. The first I knew I was caught back, and then pulled down to the balloon shed roof, for I tilted the deflecting rudder by mistake.

"But, Mr. Peterson," Tom went on, "I haven't seen you in some time. Anything new on, that brings you here?" for the fortune-hunter had called at the Swift house after Tom had gone out to the shop to get his airship ready for the flight to try the magneto.

"Well, Tom, I have something rather new on," replied Mr. Peterson. "I hoped to interest your father in it, but he doesn't seem to care to take a chance. It's a lost opal mine on a little-known island in the Caribbean Sea not far from the city of Colon. I say not far—by that I mean about twenty miles. But your father doesn't want to invest, say, ten thousand dollars in it, though I can almost guarantee that he'll get five times that sum back. So, as long as he doesn't feel that he can help me out, I guess I'd better be traveling on."

"Hold on! Wait a minute. Don't be in a hurry," said Mr. Swift.

Mr. Peterson was an old friend, and when he and Mr. Swift were young men they had prospected and grub-staked together. But Mr. Swift soon gave that up to devote his time to his inventions, while Mr. Peterson became a sort of rolling stone.

He was a good man, but somewhat visionary, and a bit inclined to "take chances"—such as looking for lost treasure—rather than to devote himself to some steady employment. The result was that he led rather a precarious life, though never being actually in want.

"No, pardner," he said to Mr. Swift. "It's kind of you to ask me to stay; but this mine business has got a grip on me. I want to try it out. If you won't finance the project someone else may. I'll say good-bye, and—"

"Now just a minute," said Mr. Swift. "It's true, Alec, I had about made up my mind not to go into this thing, when this accident happened to Tom. Now you practically saved his life. You—"

"Oh, pshaw! I only acted on the spur of the moment. Anyone could have done what I did," protested the fortune-hunter.

"Oh, but you did it!" insisted Mr. Swift, "and you did it in the nick of time. Now I wouldn't for a moment think of offering you a reward for saving my son's life. But I do feel mighty friendly toward you—not that I didn't before—but I do want to help you. Alec, I will go into this business with you. We'll take a chance! I'll invest ten thousand dollars, and I'm not so awful worried about getting it back, either—though I don't believe in throwing money away."

"You won't throw it away in this case!" declared Mr. Peterson, eagerly. "I'm sure to find that mine; but it will take a little capital to work it. That's what I need—capital!"

"Well, I'll supply it to the extent of ten thousand dollars," said Mr. Swift. "Tom, what do you think of it? Am I foolish or not?"

"Not a bit of it, Dad!" cried the young man, who was now himself again. "I'm glad you took that chance, for, if you hadn't—well, I would have supplied the money myself—that's all," and he smiled at the fortune-hunter.



CHAPTER III

PLANNING A BIG GUN

"BUT, Tom, I don't see how in the world you can ever hope to make a bigger gun than that."

"I think it can be done, Ned," was the quiet answer of the young inventor. He looked up from some drawings on the table in the office of one of his shops. "Now I'll just show you—"

"Hold on, Tom. You know I have a very poor head for figures, even if I do help you out once in a while on some of your work. Skip the technical details, and give me the main facts."

The two young men—Ned Newton being Tom's special chum—were talking together over Tom's latest scheme.

It was several days after Tom's accident in the airship, when he had been saved by the prompt action of Mr. Peterson. That fortune-hunter, once he had the promise of Mr. Swift to invest in his somewhat visionary plan of locating a lost opal mine near the Panama Canal, had left the Swift homestead to arrange for fitting out the expedition of discovery. He had tried to prevail on Tom to accompany him, and, failing in that, tried to work on Mr. Damon.

"Bless my watch chain!" exclaimed that odd gentleman. "I would like to go with you first rate. But I'm so busy—so very busy—that I can't think of it. I have simply neglected all my affairs, chasing around the country with Tom Swift. But if Tom goes I—ahem! I think perhaps I could manage it—ahem!"

"I thought you were busy," laughed Tom.

"Oh, well, perhaps I could get a few weeks off. But I'm not going—no, bless my check book, I must get back to business!"

But as Mr. Damon was a retired gentleman of wealth, his "business" was more or less of a joke among his friends.

So then, a few days after the departure of Mr. Peterson, Tom and Ned sat in the former's office, discussing the young inventor's latest scheme.

"How big is the biggest gun ever made, Tom?" asked his chum. "I mean in feet, in inches, or in muzzle diameter, however they are measured."

"Well," began Tom, "of course some nation may, in secret, be making a bigger gun than any I have ever heard of. As far as I know, however, the largest one ever made for the United States was a sixteen-inch rifled cannon—that is, it was sixteen inches across at the muzzle, and I forget just how long. It weighed many tons, however, and it now lies, or did a few years ago, in a ditch at the Sandy Hook proving grounds. It was a failure."

"And yet you are figuring on making a cannon with a muzzle thirty inches across—almost a yard—and fifty feet long and to weigh—"

"No one can tell exactly how much it will weigh," interrupted Tom. "And I'm not altogether certain about the muzzle measurement, nor of the length. It's sort of in the air at present. Only I don't see why a larger gun than any that has yet been made, can't be constructed."

"If anybody can invent one, you can, Tom Swift!" exclaimed Ned, admiringly.

"You flatter me!" exclaimed his chum, with a mock bow.

"But what good will it be?" went on Ned. "Making big guns doesn't help any in war, that I can see."

"Ned!" exclaimed Tom, "you don't look far enough ahead. Now here's my scheme in a nutshell. You know what Uncle Sam is doing down in his big ditch; don't you?"

"You mean digging the Panama Canal?"

Yes, the greatest engineering feat of centuries. It is going to make a big change in the whole world, and the United States is going to become—if she is not already—a world-power. Now that canal has to be protected—I mean against the possibility of war. For, though it may never come, and the chances are it never will, still it may.

"Uncle Sam has to be ready for it. There never was a more true saying than 'in time of peace prepare for war.' Preparing for war is, in my opinion, the best way not to have one.

"Once the Panama Canal is in operation, and the world-changes incidental to it have been made, if it should pass into the hands of some foreign country—as it very possibly might do—the United States would not only be the laughing-stock of the world, but she would lose the high place she holds.

"Now, then, to protect the canal, several things are necessary. Among them are big guns—cannon that can shoot a long distance—for if a foreign nation should send some of their new dreadnaughts over here—vessels with guns that can shoot many miles—where would the canal be once a bombardment was opened? It would be ruined in a day—the immense lock-gates would be destroyed. And, not only from the guns aboard ships would there be danger, but from siege cannon planted in Costa Rica, or some South American country below the canal zone.

"Now, to protect the canal against such an attack we need guns that can shoot farther, straighter and more powerfully than any at present in use, and we've got to have the most powerful explosive. In other words, we've got to beat the biggest guns that are now in existence. And I'm going to do it, Ned!"

"You are?"

"Yes, I'm going to invent a cannon that will make the longest shots on record. I'm going to make a world-beater gun; or, rather, I'm going to invent it, and have it made, for I guess it would tax this place to the limit.

"I've been thinking of this for some time, Ned. I've been puttering around inventing new magnetos, potato-parers and the like, but this is my latest hobby. The Panama Canal is a big thing—one of the biggest things in the world. We need the biggest guns in the world to protect it.

"And, listen: Uncle Sam thinks the same way. I understand that the best men in the service—at West Point, Annapolis and Sandy Hook, as well as elsewhere—are working in the interest of the United States to perfect a bigger cannon than any ever before made. In fact, one has just been constructed, and is going to be tried at the Sandy Hook proving grounds soon. I'm going to see the test if I can.

"And here's another thing. Foreign nations are trying to steal Uncle Sam's secrets. If this country gets a big cannon, some other nation will want a bigger one. It's a constant warfare. I'm going to devote my talents—such as they are—to Uncle Sam. I'm going to make the biggest cannon in the world—the one that will shoot the farthest and knock into smithereens all the other big guns. That's the only way to protect the canal. Do you understand, Ned?"

"Somewhat, Tom. Since I gave up my place in the bank, and became a sort of handy-lad for you, I know more about your work. But isn't it going to be dangerous to make a cannon like that?"

"Well, in a way, yes, Ned. But we've got to take chances, just as father did when he invested ten thousand dollars in that opal mine. He'll never see his money again."

"Don't you think so?"

"No, Ned."

"And when do you expect to start on your gun, Tom?"

"Right away. I'm making some plans now. I'm going down to Sandy Hook and witness the test of this new big cannon. You can come along, if you like."

"Well, I sure will like. When is it?"

"Oh, in about a week. I'll have to look—"

"'Scuse me, Massa Tom," broke in Eradicate, as he put his head through the half-opened office door. "'Scuse me, but dere's a express gen'men outside, wif his auto truck, an' he's got some packages fo' yo' all, marked 'dangerous—explosive—an' keep away fom de fire.' He want t' know what he all gwine t' do wif 'em, Massa Tom?"

"Do with 'em? Oh, I guess it's that new giant powder I sent for. Why, Eradicate, have him bring 'em right in here."

"Yais, sah, Massa Tom. Dat's all right; but he jest can't bring 'em in," and Eradicate looked behind him somewhat apprehensively.

"Can't bring 'em in? Why not, I'd like to know?" exclaimed Tom. "He's paid for it."

"'Scuse me, Massa Tom," said the colored man, "but dat express gen'men can't bring dem explosive powder boxes in heah, 'case as how his autermobile hab done ketched fire an' he cain't get near it nohow. Dat's why, Massa Tom!"

"Caesar's ghost!" yelled the young inventor. "The auto on fire, and that powder in it! Come on Ned!" and he made a rush for the door.



CHAPTER IV

KOKU'S BRAVE ACT

"Tom! Tom!" cried Ned, as he watched the disappearing figure of his chum. "Come back here! If there's going to be an explosion we ought to run out of the back door!"

"I'm not running away!" flashed back Tom. "I'm going to get that powder out of the auto before it goes up! If it does we'll be blown to kingdom come, back door or front door! Come on!"

"Bacon and eggs!" yelled Ned. "He's running an awful risk! But I can't let him go alone! I guess we're in for it!"

Then he, too, rushed from the office toward the front of the shop, before which, in a sort of private road, stood the blazing auto. And Ned, who had now lost sight of Tom, because of our hero having turned a corner in the corridor, heard excited shouts coming from the seat of trouble.

"If that's some new kind of powder Tom's sent for, to test for his new big gun, and it goes up," Ned said to himself, as he rushed on, "this place will be blown to smithereens. All Tom's valuable machinery and patents will be ruined!"

Ned had now reached the front door of the shop. He had a glimpse of the burning auto—a small express truck, well loaded with various packages. And, through the smoke, which from the odor must have been caused by burning gasoline, Ned could see several boxes marked in red letters:

DANGEROUS EXPLOSIVE

KEEP AWAY FROM FIRE

"Keep away from fire!" murmured the panting lad. "If they can get any nearer fire I don't see how."

"Oh, mah golly!" gasped Eradicate, who had lumbered on behind Ned. "Oh, mah golly! Oh, good land ob massy! Look at Massa Tom!"

"I've got to help him!" cried Ned, for he saw that his chum had rushed to the rear of the auto, and was endeavoring to drag one of the powder boxes across the lowered tail-board. Tom was straining and tugging at it, but did not seem able to move the case. It was heavy, as Ned learned later, and was also held down by the weight of other express packages on top of it.

"Oh, mah golly!" cried Eradicate. "Git some watah, somebody, an' put out dat fire!"

"No—no water!" yelled Tom, who heard him. "Water will only make it worse—it'll scatter the blazing gasoline. The feed pipe from the tank must have burst. Throw on sand—sand is the only thing to use!"

"I'll git a shubble!" cried Eradicate. "I'll git a sand-shubble!" and he tottered off.

"Wait, Tom, I'll give you a hand!" cried Ned, as he saw his chum step away from the end of the auto for a moment, as a burst of flame, and choking smoke, driven by the wind, was blown almost in his face. "I'll help you!"

"We've got to be lively, then, Ned!" gasped Tom. "This is getting hotter every minute! Where's that Koku? He could yank these boxes out in a jiffy!"

And indeed a giant's strength was needed at that moment.

Ned glanced around to see if he could catch a glimpse of the big man whom Tom had brought from Giant Land, but Koku was not in sight.

"Let's have another try now, Ned!" suggested Tom, when a shift in the wind left the rear of the auto comparatively free from smoke and flame.

"You fellows had better skip!" cried the expressman, who had been throwing light packages off his vehicle from in front, where, as yet, there was no fire. "That powder'll go up in another minute. Some of the boxes are beginning to catch now!" he yelled. "Look out!"

"That's right!" shouted Tom, as he saw that the edge of one of the wooden cases containing the powder was blazing slightly. "Lively, Ned!"

Ned held back only for a second. Then, realizing that the time to act was now or never, and that even if he ran he could hardly save himself, he advanced to Tom's side. The smoke was choking and stifling them, and the flames, coming from beneath the auto truck, made them gasp for breath.

Together Tom and Ned tugged at the nearest case of powder—the one that was ablaze.

"We—we can't budge it!" panted Tom.

"It—it's caught somewhere," added Ned. "Oh, if Koku were only here!"

There was a sound behind the lads. A voice exclaimed:

"Master want shovel, so Eradicate say—here it is!"

They turned and saw a big, powerful man, with a simple, child-like face, standing calmly looking at the burning auto.

"Koku!" cried Tom. "Quick! Never mind the shovel! Get those powder boxes out of that cart before they go up! Yank 'em out! They're too much for Ned and me! Quick!"

"Oh, of a courseness I will so do!" said Koku, to whom, even yet, the English language was somewhat of a mystery. He dropped the shovel, and, heedless of the thick smoke from the burning gasoline, reached over and took hold of the nearest box. It seemed as though he pulled it from the auto truck as easily as Tom might have lifted a cork.

Then, carrying the box, which was now burning quite fiercely on one corner, over toward Tom and Ned, who had moved back, the giant asked:

"What you want of him, Master?"

"Put it down, Koku, and get out all the others! Lively, now, Koku!"

"I do," was the simple answer. The giant put the box on the grass and ran back toward the auto.

"Quick, Ned!" shouted Tom. "Throw some sand on this burning box! That will put out the fire!"

A few handfuls of earth served to extinguish the little blaze, and by this time Koku had come back with another box of powder.

"Get 'em all, Koku, get 'em all! Then we can put out the fire on the auto."

For the giant it was but child's play to carry the heavy boxes of powder, and soon he had them all removed from the truck. Then, with the danger thus narrowly averted, they all, including the expressman, turned in and began throwing sand on the fire, which now had a good hold on the body of the auto. The shovel, which Eradicate had sent by Koku, who could use more speed than could the aged colored man, came in handy.

Soon the fire was out, though not before the truck had been badly damaged, and some of its load destroyed. But, beyond a charring of some of the powder boxes, the explosive was intact.

"Whew! That was a lucky escape," murmured Tom, as he sat down on one of the boxes, and wiped the smoke and sweat from his face. "A little later and there'd only been a hole in the ground to tell what happened. Hot work; eh, Ned?"

"I guess yes, Tom."

"I thought of the powder as soon as I saw that the truck was on fire," explained the expressman; "but I didn't know what to do. I was kinder flustered, I guess. This is the second time this old truck has caught fire from a leaky gasoline pipe. I guess that will be the last—it will for me, anyhow. I'll resign if they don't give me another machine. Will you sign for your stuff?" he asked Tom, holding out the receipt book, which had escaped the flames.

"Yes, and I'm mighty glad I'm here to sign for it," replied the young inventor. "Now, Koku, I guess you can take that stuff up to the shop; but be careful where you put it."

"I do, Master," replied the giant.

"What sort of powder is that, Tom?" asked Ned a little later, when they were again back in the office, the excitement having calmed down. The expressman had gone back to town afoot, to arrange about getting another vehicle for what remained of his load. "Is it the kind they use in big guns?"

"One of the kinds," replied Tom. "I sent for several samples, and this is one. I'm going to conduct some tests to see what kind I'll need for my own big gun. But I expect I'll have to invent an explosive as well as a cannon, for I want the most powerful I can get. Want to look at some of this powder?"

"Yes, if you think it's safe."

"Oh, it's safe enough if you treat it right. I'll show you," and working carefully Tom soon had one of the boxes open. Reaching into the depths he held up a handful of something that looked like sticks of macaroni. "There it is," he said.

"That powder?" cried Ned. "That's a queer kind. I've seen the kind they use in some guns on the battleships. That powder was in hexagonal form, about two inches across, and had a hole in the centre. It was colored brown."

"Well, powder is made in many forms," explained Tom. "A person who has only seen black gunpowder, with its little grains, would not believe that this was one grain of the new powder."

"That macaroni stick a grain of powder?" cried Ned.

"Yes, we'll call it a grain," went on the young inventor, "just as the brown, hexagonal cube you saw was a grain. You see, Ned, the idea is to explode all the powder at once—to get instantaneous action. It must all burn up at once as soon as it is detonated, or set off.

"To do that you have to have every grain acted on at the same moment, and that could not be done if the powder was in one solid chunk, or closely packed. For that reason they make it in different shapes, so it will lie loose in the firing chamber, just as a lot of jack-straws are piled up. In fact, some of the new powder looks like jack-straws. Some, as this, for instance, looks like macaroni. Other is in cubes, and some in long strings."

As he spoke Tom struck a match and held the flames near the end of one of the "macaroni" sticks.

"Caesar's grandmother!" yelled Ned. "Are you crazy, Tom?" as he started to leap for a window.

"Don't get excited," spoke Tom, quietly. "There's no danger," and he actually set fire to the stick of queer powder, which burned like some wax taper.

"But—but—" stammered Ned.

"It is only when powder is confined that it explodes," Tom explained. "If it can burn in the open it's as harmless as water, provided you don't burn too much at once. But put it in something where the resulting gases accumulate and can't escape, and then—why, you have an explosion—that's all."

"Yes—that's all," remarked Ned, grimly, as he nervously watched the burning stick of powder. Tom let it flame for a few seconds, and then calmly blew it out.

"You know what a little puff black gunpowder gives, if you burn some openly on the ground," went on Tom; "don't you, Ned?"

"Sure, I've often done that."

"But put that same powder in a tight box, and set fire to it, and you have a bang instead of a puff. It's the same way with this powder, only it doesn't even puff, for it burns more slowly.

"An explosion, you see, is the sudden liberation at one time of the gases which result when the powder is burned. If the gases are given off gradually, and in the open, no harm is done. But put a stick like this in, say, a steel box, all closed up, save a hole for the fuse, and what do you have? An explosion. That's the principle of all guns and cannon.

"But say, Ned, I'm getting to be a regular lecturer. I didn't know I was running on so. Why didn't you stop me?"

"Because I was interested. Go on, tell me some more."

"Not now. I want to get this powder in a safe place. I'm a little nervous about it after that fire. You see if it had caught, when tightly packed in the boxes, there would have been a terrific explosion, though it does burn so harmlessly in the open air. Now let me see—"

Tom was interrupted by the postman's whistle, and a little later Eradicate came in with the mail that had been left in the box at the shop door. Tom rapidly looked over the letters.

"Here's the note I want, I think," he said, Selecting one. "Yes, this is it. 'Permission is hereby granted,' he read, 'to Thomas Swift to visit,' and so on, and so on. This is the stuff, Ned!" he cried.

"What is it?"

"A permit to visit the government proving grounds at Sandy Hook, Ned, and see 'em test that new big gun I was telling you about. Hurray! We'll go down there, and I'll see how my ideas fit in with those of the government's experts."

"Did you say 'we' would go down, Tom?"

"I sure did. You'll go with me; won't you?"

"Well, I hadn't thought very much about it, but I guess I will. When is it?"

"A week from today, and I'm going to need all that time to get ready. Now let's get busy, and we'll arrange to go to Sandy Hook. I've had trouble enough to get this permit—I guess I'll put it where it won't get lost," and he locked it in a secret drawer of his desk.

Then the lads stored the powder in a safe place, and soon were busy about several matters in the shop.



CHAPTER V

OFF TO SANDY HOOK

"What's the idea of this government test of the big gun, Tom?" asked Ned. "I got so excited about that near-explosion the other day, that I didn't think to ask you all the particulars."

"Why, the idea is to see if the gun will work, and do all that the inventor claims for it," was the answer. "They always put a new gun through more severe tests than anything it will be called on to stand in actual warfare. They want to see just how much margin of safety there is."

"Oh I see. And is this one of the guns that are to be used in fortifying the Panama Canal?"

"Well, Ned, I don't know, exactly. You see, the government isn't telling all its secrets. I assume that it is, and that's why I'm anxious to see what sort of a gun it is.

"As a matter of fact, I'm going into this thing on a sort of chance, just as dad did when he invested in Mr. Peterson's opal mine."

"Do you think anything will come of that, Tom?"

"I don't know. If we get down to Panama, after I have made my big gun, we may take a run over, and see how he is making out. But, as I said, I'm going into this big cannon business on a sort of gamble. I have heard, indirectly, that Uncle Sam intends to use a new type of gun in fortifying the Panama Canal. It's about forty-nine miles long, you know, and it will take many guns to cover the whole route, as well as to protect the two entrances."

"Not so very many if you make a gun that will shoot thirty miles," remarked Ned, with a smile.

"I'm not so sure I can do it," went on Tom. "But, even at that, quite a number of guns will be needed. For if any foreign nation, or any combination of nations, intend to get the canal away from us, they won't make the attack from one point. They'll come at us seven different ways for Sunday, and I've never heard yet of a gun that can shoot seven ways at once. That's why so many will be needed.

"But, as I said, I don't know just what type the Ordnance Department will favor, and I want to get a line. Then, even if I invent a cannon that will outshoot all the others, they may not take mine. Though if they do, and buy a number of them, I'll be more than repaid for my labor, besides having the satisfaction of helping my country."

"Good for you, Tom! I wish it was time to go to Sandy Hook now. I'm anxious to see that big gun. Do you know anything about it?"

"Not very much. I have heard that it is not quite as large as the old sixteen-inch rifle that they had to throw away because of some trouble, I don't know just what. It was impractical, in spite of its size and great range. But this new gun they are going to test is considerably smaller, I understand.

"It was invented by a General Wailer, and is, I think, about twelve inches across at the muzzle. In spite of that comparatively small size, it fires a projectile weighing a thousand pounds, or half a ton, and takes five hundred pounds of powder. Its range, of course, no one knows yet, though I have heard it said that General Wailer claims it will shoot twenty miles."

"Whew! Some shot!"

"I'm going to beat it," declared Tom, "and I want to do it without making such a monstrous gun that it will be difficult to cast it.

"You see, Ned, there is, theoretically, nothing to prevent the casting of a steel rifled cannon that would be fifty inches across at the muzzle, and making it a hundred feet long. I mean it could be done on paper—figured out and all that. But whether you would get a corresponding increase in power or range, and be able to throw a relatively larger projectile, is something no one knows, for there never has been such a gun made. Besides, the strain of the big charge of powder needed would be enormous. So I don't want merely to make a giant cannon. I want one that will do a giant's work, and still be somewhere in the middle-sized class."

"I see. Well, you'll probably get some points at Sandy Hook."

"I think so. We go day after tomorrow."

"Is Mr. Damon going?'

"I think not. If he does I'll have to get another pass, for mine only calls for two persons. I got it through a Captain Badger, a friend of mine, stationed at the Sandy Hook barracks. He doesn't have anything to do with the coast defense guns, but he got the pass to the proving grounds for me."

Tom and his chum talked for some time about the prospects for making a giant cannon, and then the young inventor, with Ned's aid, made some powder tests, using some of the explosive that had so nearly caught fire.

"It isn't just what I want," Tom decided, after he had put small quantities in little steel bombs, and exploded them, at a safe distance, and under a bank of earth, by means of an electric primer.

"Why, Tom, that powder certainly burst the bombs all to pieces," said Ned, picking up a shattered piece of steel.

"I know, but it isn't powerful enough for me. I'm going to send for samples of another kind, and if I can't get what I want I'll make my own powder. But come on now, this stuff gives me a headache. Let's take a little flight in the Humming Bird. We'll go see Mr. Damon," and soon the two lads were in the speedy little monoplane, skimming along like the birds. The fresh air soon blew away their headaches, caused by the fumes from the nitro-glycerine, which was the basis of the powder. Dynamite will often produce a headache in those who work with it.

Two days later Tom and Ned set off for Sandy Hook.

This long, neck-like strip of land on the New Jersey coast is, as most of you know, one of the principal defenses of our country.

Foreign vessels that steam into New York harbor first have to pass the line of terrible guns that, back of the earth and concrete defenses, look frowningly out to sea. It is a wonderful place.

On the Sandy Hook Bay side of the Hook there is a life-saving station. Right across, on the sea side, are the big guns. Between are the barracks where the soldiers live, and part of the land is given over to a proving ground, where many of the big guns are taken to be tested.

Tom and Ned reached New York City without incident of moment, and, after a night spent at a hotel, they went to the Battery, whence the small government steamer leaves every day for Sandy Hook. It is a trip of twenty-one miles, and as the bay was rather rough that day, Tom and Ned had a taste of a real sea voyage. But they were too experienced travelers to mind that, though some other visitors were made quite ill.

A landing was made on the bay side of the Hook, it being too rough to permit of a dock being constructed on the ocean side.

"Now we'll see what luck we have," spoke Tom, as he and Ned, inquiring the way to the proving grounds from a soldier on duty, started for them. On the way they passed some of the fortifications.

"Look at that gun!" exclaimed Ned, pointing to a big cannon which seemed to be crouched down in a sort of concrete pit. "How can they fire that, Tom? The muzzle points directly at the stone wall. Does the wall open when they want to fire?"

"No, the gun raises up, peeps over the wall, so speak, shoots out its projectile, and then crouches down again."

"Oh, you mean a disappearing gun."

"That's it, Ned. See, it works by compressed air," and Tom showed his chum how, when the gun was loaded, the projectile in place, and the breech-block screwed fast, the officer in charge of the firing squad would, on getting the range from the soldier detailed to calculate it, make the necessary adjustments, and pull the lever.

The compressed air would fill the cylinders, forcing the gun to rise on toggle-jointed arms, so that the muzzle was above the bomb-proof wall. Then it would be fired, and sink back again, out of sight of the enemy.

The boys looked at several different types of big rifled cannon, and then passed on. They could hear firing in the distance, some of the explosions shaking the ground.

"They're making some tests now," said Tom, hurrying forward.

Ned followed until, passing a sort of machine shop, the lads came to where a sentry paced up and down a concrete walk.

"Are these the proving grounds?" asked Tom. "This is the entrance to them," replied the soldier, bringing his rifle to "port," according to the regulations. "What do you want?"

"To go in and watch the gun tests," replied Tom. "I have a permit," and he held it out so the soldier could see it.

"That permit is no good here;" the sentry exclaimed.

"No good?" faltered Tom.

"No, it has to be countersigned by General Wailer. And, as he's on the proving grounds now, you can't see him. He's getting ready for the test of his new cannon."

"But that's just what we want to see!" cried Tom. "We want to get in there purposely for that. Can't you send word to General Wailer?"

"I can't leave my post," replied the sentry, shortly. "You'll have to come another time, when the General isn't busy. You can't get in unless he countersigns that permit."

"Then it may be too late to witness the test," objected the young inventor. "Isn't there some way I can get word to him?"

"I don't think so," replied the sentry. "And I'll have to ask you to leave this vicinity. No strangers are allowed on the proving grounds without a proper pass."



CHAPTER VI

TESTING THE WALLER GUN

Tom looked at Ned in dismay. After all their work and planning, to be thus thwarted, and by a mere technicality! As they stood there, hardly knowing what to do, the sound of a tremendous explosion came to their ears from behind the big pile of earth and concrete that formed the bomb-proof around the testing ground.

"What's that?" cried Ned, as the earth shook.

"Just trying some of the big guns," explained the sentry, who was not a bad-natured chap. He had to do his duty. "You'd better move on," he suggested. "If anything happens the government isn't responsible, you know."

"I wish there was some way of getting in there," murmured Tom.

"You can see General Waller after the test, and he will probably countersign the permit," explained the sentry.

"And we won't see the test of the gun I'm most interested in," objected Tom. "If I could only—"

He stopped as he noticed the sentry salute someone coming up from the rear. Tom and Ned turned to behold a pleasant-faced officer, who, at the sight of the young inventor, exclaimed:

"Well, well! If it isn't my old friend Tom Swift! So you got here on my permit after all?"

"Yes, Captain Badger," replied the lad, and then with a rueful face he added: "But it doesn't seem to be doing me much good. I can't get into the proving grounds."

"You can't? Why not?" and he looked sharply at the sentry.

"Very sorry, sir," spoke the man on guard, "but General Wailer has left orders, Captain Badger, that no outsiders can enter the proving grounds when his new gun is being tested unless he countersigns the permits. And he's engaged just now. I'm sorry, but—"

"Oh, that's all right, Flynn," said Captain Badger. "It isn't your fault, of course. I suppose there is no rule against my going in there?" and he smiled.

"Certainly not, sir. Any officer may go in," and the guard stepped to one side.

"Let me have that pass, Tom, and wait here for me," said the Captain. "I'll see what I can do for you," and the young officer, whose acquaintance Tom had made at the tests when the government was purchasing some aeroplanes for the army, hurried off.

He came back presently, and by his face the lads knew he had been successful.

"It's all right," he said with a smile. "General Waller countersigned the pass without even looking at it. He's so excited over the coming test of his gun that he hardly knows what he is doing. Come on in, boys. I'll go with you."

"Then they haven't tested his gun yet?" Asked Tom, eagerly, anxious to know whether he had missed anything.

"No, they're going to do so in about half an hour. You'll have time to look around a bit. Come on," and showing the sentinel the counter-signed pass, Captain Badger led the two youths into the proving grounds.

Tom and Ned saw so much to interest them that they did not know at which to look first. In some places officers and firing squads were testing small-calibre machine guns, which shot off a round with a noise like a string of firecrackers on the Chinese New Year's. On other barbettes larger guns were being tested, the noise being almost deafening.

"Stand on your tiptoes, and open your mouth when you see a big cannon about to be fired," advised Captain Badger, as he walked alongside the boys.

"What good does that do?" inquired Ned.

"It makes your contact with the earth as small as possible—standing on your toes," the officer explained, "and so reduces the tremor. Opening your mouth, in a measure, equalizes the changed air pressure, caused by the vacuum made when the powder explodes. In other words, you get the same sort of pressure down inside your throat, and in the tubes leading to the ear—the same pressure inside, as outside.

"Often the firing of big guns will burst the ear drums of the officers near the cannon, and this may often be prevented by opening the mouth. It's just like going through a deep tunnel, or sometimes when an elevator descends quickly from a great height. There is too much outside air pressure on the ear drums. By opening your mouth and swallowing rapidly, the pressure is nearly equaled, and you feel no discomfort."

The boys tried this when the next big gun was fired, and they found it true. They noticed quite a crowd of officers and men about a certain large barbette, and Captain Badger led them in that direction.

"Is that General Wailer's gun?" asked Tom.

"That's where they are going to test it," was the answer.

Eagerly Tom and Ned pressed forward. No one of the many officers and soldiers grouped about the new cannon seemed to notice them. A tall man, who seemed very nervous and excited, was hurrying here and there, giving orders rapidly.

"How is that range now?" he asked. "Let me take a look! Are you sure the patrol vessels are far enough out? I think this projectile is going farther than any of you gentlemen have calculated."

"I believe we have correctly estimated the distance," answered someone, and the two entered into a discussion.

"That excited officer is General Wailer," explained Captain Badger, in a low voice, to Tom and Ned.

"I guessed as much," replied the young inventor. Then he went closer to get a better look at the big cannon.

I say big cannon, and yet it was not the largest the government had. In fact, Tom estimated the calibre to be less than twelve inches, but the cannon was very long—much longer in proportion than guns of greater muzzle diameter. Then, too, the breech, or rear part, was very thick and heavy.

"He must be going to use a tremendous lot of powder," said Tom.

"He is," answered Captain Badger. "Some of us think he is going to use too much, but he says it is impossible to burst his gun. He wants to make a long-range record shot, and maybe he will."

"That's a new kind of breech block," commented Tom, as he watched the mechanism being operated.

"Yes, that's General Waller's patent, too. They're going to fire soon."

I might explain, briefly, for the benefit of you boys who have never seen a big, modern cannon, that it consists of a central core of cast steel. This is rifled, just as a small rifle is bored, with twisted grooves throughout its length. The grooves, or rifling, impart a twisting motion to the projectiles, and keep them in a straighter line.

After the central core is made and rifled, thick jackets of steel are "shrunk" on over the rear part of the gun. Sometimes several jackets are put on, one over the other, to make the gun stronger.

If you have ever seen a blacksmith put a tire on a wheel you will understand what I mean. The tire is heated, and this expands it, or makes it larger. It is put on hot, and when it cools it shrinks, getting smaller, and gripping the rim of the wheel in a strong embrace. That is what the jackets of steel do to the big guns.

A big rifled cannon is loaded from the rear, or breech, just as is a breech-loading shotgun or rifle. That is, the cannon is opened at the back and the projectile is put in by means of a derrick, for often the projectiles weigh a thousand pounds or more. Next comes the powder—hundreds of pounds of it—and then it is necessary to close the breech.

The breech block does this. That block is a ponderous piece of steel, quite complicated, and it swings on a hinge fastened to one side of the rear of the gun. Once it is swung back into place, it is made fast by means of screw threads, wedges or in whatever way the inventor of the gun deems best.

The breech block must be very strong, and held firmly in place, or the terrific force of the powder would blow it out, wreck the gun and kill those behind it. You see, the breech block really stands a great part of the strain. The powder is between it and the projectile, and there is a sort of warfare to see which will give way—the projectile or the block. In most cases the projectile gracefully bows, so to speak, and skips out of the muzzle of the gun, though sometimes the big breech block will be shattered.

With eager eyes Tom and Ned watched the preparations for firing the big gun. The charge of powder was hoisted out of the bomb-proof chamber below the barbette, and then the great projectile was brought up in slings. At the sight of that Tom realized that the gun was no ordinary one, for the great piece of steel was nearly three feet long, and must have weighed nearly a thousand pounds. Truly, much powder would be needed to send that on its way.

"I'm afraid, General, that you are using too much of that strong powder," Tom heard one officer say to the inventor of the gun. "It may burst the breech."

"Nonsense, Colonel Washburn. I tell you it is impossible to burst my gun—impossible, sir! I have allowed for every emergency, and calculated every strain. I have a margin of safety equal to fifty per cent."

"Very well, I hope it proves a success."

"Of course it will. It is impossible to burst my gun! Now, are we ready for the test."

The gun was rather crude in form, not having received its final polish, and it was mounted on a temporary carriage. But even with that Tom could see that it was a wonderful weapon, though he thought he would have put on another jacket toward the muzzle, to further strengthen that portion.

"I'm going to make a gun bigger than that," said Tom to Ned. He spoke rather louder than he intended, and, as it was at a moment when there was a period of silence, the words carried to General Waller, who was at that moment near Tom.

"What's that?" inquired the rather fiery-tempered officer, as he looked sharply at our hero.

"I said I was going to make a larger gun than that," repeated Tom, modestly.

"Sir! Do you know what you are saying? How did you come in here, anyhow? I thought no civilians were to be admitted today! Explain how you got here!"

Tom felt an angry flush mounting to his cheeks.

"I came in here on a pass countersigned by you," he replied.

"A pass countersigned by me? Let me it."

Tom passed it over.

"Humph, it doesn't seem to be forged," went on the pompous officer. "Who are you, anyhow?"

"Tom Swift."

"Hum!"

"General Waller, permit me to introduce Tom Swift to you," spoke Captain Badger, stepping forward, and trying not to smile. "He is one of our foremost inventors. It is his type of monoplane that the government has adopted for the coming maneuvers at Panama, you may recall, and he was very helpful to Uncle Sam in stopping that swindling on the border last year—Tom and his big searchlight. Mr. Swift, General Waller," and Captain Badger bowed as he completed the introduction.

"What's that. Tom Swift here? Let me meet him!" exclaimed an elderly officer coming through the crowd. The others parted to make way for him, as he seemed to be a person of some importance, to judge by his uniform, and the medals he wore.

"Tom Swift here!" he went on. "I want to shake hands with you, Tom! I haven't seen you since I negotiated with you for the purchase of those submarines you invented, and which have done such splendid service for the government. Tom, I'm glad to see you here today."

The face of General Waller was a study in blank amazement.



CHAPTER VII

THE IMPOSSIBLE OCCURS

There were murmurs throughout the throng about the big gun, as the officer approached Tom Swift and shook hands with him.

"What have you in mind now, Tom, that you come to Sandy Hook?" the much-medaled officer asked.

"Nothing much, Admiral," answered our hero.

"Oh, yes, you have!" returned Admiral Woodburn, head of the naval forces of Uncle Sam. "You've got some idea in your head, or you wouldn't come to see this test of my friend's gun. Well, if you can invent anything as good for coast defense, or even interior defense, as your submarines, it will be in keeping with what you have done in the past. I congratulate you, General Waller, on having Tom Swift here to give you the benefit of some of his ideas."

"I—I haven't had the pleasure of meeting Mr. Swift before," said the gun inventor, stiffly. "I did not recognize his name when I countersigned his pass."

It was plain that the greeting of Tom by Admiral Woodburn had had a marked effect in changing sentiment toward our hero. Captain Badger smiled as he noticed with what different eyes the gun inventor now regarded the lad.

"Well, if Tom Swift gives you any points about your gun, you want to adopt them," went on the Admiral. "I thought I knew something about submarines, but Tom taught me some things, too; didn't you, Tom?"

"Oh, it was just a simple matter, Admiral," said Tom, modestly. "Just that little point about the intake valves and the ballast tanks."

"But they changed the whole matter. Yes, General, you take Tom's advice—if he gives you any."

"I don't know that I will need any—as yet," replied General Waller. "I am confident my gun will be a success as it is at present constructed. Later, however, if I should decide to make any changes, I will gladly avail myself of Mr. Swift's counsel," and he bowed stiffly to Tom. "We will now proceed with the test," he went on. "Kindly send a wireless to the patrol ships that we are about to fire, and ask them to note carefully where the projectile falls."

"Very good, sir," spoke the officer in immediate charge of the matter, as he saluted. Soon from the aerials snapped the vicious sparks that told of the wireless telegraph being worked.

I might explain that near the spot where the projectile was expected to fall into the sea—about fifteen miles from Sandy Hook—several war vessels were stationed to warn shipping to give the place a wide berth. This was easy, since the big gun had been aimed at a spot outside of the steamship lanes. Aiming the rifle in a certain direction, and giving it a definite angle of inclination, made it practically certain just where the shot would fall. This is called "getting the range," and while, of course, the exact limit of fire of the new gun was not known, it had been computed as nearly as possible.

"Is everything ready now?" asked General Waller, while Tom was conversing with his friends, Captain Badger and Admiral Woodburn, Ned taking part in the conversation from time to time.

"All ready, sir," was the assurance. The inventor was plainly nervous as the crucial moment of the test approached. He went here and there upon the barbette, testing the various levers and gear wheels of the gun.

The projectile and powder had been put in, the breech-block screwed into place, the primer had been inserted, and all that remained was to press the button that would make the electrical connection, and explode the charge. This act of firing the gun had been intrusted to one of the soldiers, for General Waller and his brother officers were to retire to a bomb-proof, whence they would watch the effect of the fire, and note the course of the projectile.

"It seems to me," remarked Ned, "that the soldier who is going to fire the gun is in the most danger."

"He would be—if it exploded," spoke Tom, for his officer friends had joined their colleagues, most of whom were now walking toward the shelter. "But I think there is little danger.

"You see, the electric wires are long enough to enable him to stand some distance from the gun. And, if he likes, he can crouch behind that concrete wall of the next barbette. Still, there is some chance of an accident, for, no matter how carefully you calculate the strain of a bursting charge of powder, and how strongly you construct the breech-block to stand the strain, there is always the possibility of a flaw in the metal. So, Ned, I think we'll just go to the bomb-proof ourselves, when we see General Waller making for the same place."

"I suppose," remarked Ned, "that in actual warfare anyone who fired one of the big guns would have to stand close to it—closer than that soldier is now."

"Oh, yes—much," replied Tom, as he watched General Waller giving the last instructions to the private who was to press the button. "Only, of course, in war the guns will have been tested, and this one has not. Here he comes; I guess we'd better be moving."

General Waller, having assured himself that everything was as right as possible, had given the last word to the private and was now making his way toward the bomb-proof, within which were gathered his fellow-officers and friends.

"You had better retire from the immediate vicinity of the gun," said its inventor to Tom and Ned, as he passed them. "For, while I have absolute confidence in my cannon, and I know that it is impossible to burst it, the concussion may be unpleasant at such close range."

"Thank you," said Tom. "We are going to get in a safe place."

He could not refrain from contrasting the general's manner now with what it had been at first.

As for Ned, he could not help wondering why, if the inventor had such absolute faith in his weapon, he did not fire it himself, even at the risk of a "concussion."

How it happened was never accurately known, as the soldier declared positively—after he came out of the hospital—that he had not pressed the button. The theory was that the wires had become crossed, making a short circuit, which caused the gun to go off prematurely.

But suddenly, while Tom, Ned and General Waller were still some distance away from the bomb-proof, there was a terrific explosion. It seemed as if the very foundations of the fortifications would be shattered There was a roaring in the air—a hot burst of flame, and instantly such a vacuum was created that Tom and Ned found themselves gasping for breath.

Dazed, shaken in every bone, with their muscles sore, they picked themselves up from the ground, along which they had been blown with great force in the direction of the bomb-proof. Even as Tom struggled to his feet, intending to run to safety in fear of other explosions, he realized what had happened.

"What—what was it?" cried Ned, as he, too, arose.

"The gun burst!" yelled Tom.

He looked to the left and saw General Waller picking himself up, his uniform torn, and blood streaming from a cut on his face. At the same instant Tom was aware of the body of a man flying through the air toward a distant grass plot, and the young inventor recognized it as that of the soldier who had been detailed to fire the great cannon.

Almost instantaneously as everything happened, Tom was aware of noticing several things, as though they took place in sequence. He looked toward where the gun had stood. It was in ruins. The young inventor saw something, which he took to be the projectile, skimming across the sea waves, and he had a fleeting glimpse of the greater portion of the immense weapon itself sinking into the depths of the ocean.

Then, coming down from a great height in the air, he saw a dark object. It was another piece of the cannon that had been hurled skyward.

"Look out!" Tom yelled, instinctively, as he staggered toward the bomb-proof, Ned following.

He saw a number of officers running out to assist General Waller, who seemed too dazed to move. Many of them had torn uniforms, and not a few were bleeding from their injuries. Then the air seemed filled with a rain of small missiles—stones, dirt, gravel and pieces of metal.



CHAPTER VIII

A BIG PROBLEM

"Are you much hurt, Ned?"

Tom Swift bent anxiously over the prostrate form of his chum. A big piece of the burst gun had fallen close to Ned—so close, in fact, that Tom, who saw it as he neared the entrance to the bomb-proof, shuddered as he raced back. But there was no sign of injury on his chum.

"Are you much hurt, Ned?"

The lad's eyes opened. He seemed dazed.

"No—no, I guess not," he answered, slowly. "I—I guess I'm as much scared as hurt, Tom. It was the wind from that big piece that knocked me down. It didn't actually hit me."

"No, I should say not," put in Captain Badger, who had run out toward the two lads. "If it had hit you there wouldn't have been much of you left to tell the tale," and he nodded toward the big piece of metal Tom had seen coming down from the sky. That part of the cannon forming a portion of the breech had buried itself deep in the earth. It had landed close to Ned—so close that, as he said, the wind of it, as well as the concussion, perhaps, had thrown him with enough force to send the breath from him.

"Glad to hear that, old man!" exclaimed Tom, with a sigh of relief. "If you'd been hurt I should have blamed myself."

"That would have been foolish. I took the same chance that you did," answered Ned, as he arose, and limped off between the captain and Tom.

A great silence seemed to have followed the terrific report. And now the officers and soldiers began to recover from the stupor into which the accident had thrown them. Sentries began pouring into the proving grounds from other portions of the barracks, and an ambulance call was sent in.

General Waller's comrades had hurried out to him, and were now leading him away. He did not seem to be much hurt, though, like many others, he had received numerous cuts and scratches from bits of stone and gravel scattered by the explosion, as well as from small bits of metal that were thrown in all directions.

"Are you hurt, General?" asked Admiral Woodburn, as he put his arm about the shoulder of the inventor.

"No—that is to say, I don't think so. But what happened? Did they fire some other gun in our direction by mistake?"

For a moment they all hesitated. Then the Admiral said, gently:

"No, General. It was your own gun—it burst."

"My gun! My gun burst?"

"That was it. Fortunately, no one was killed."

"My gun burst! How could that happen? I drew every plan for that gun myself. I made every allowance. I tell you it was impossible for it to burst!"

"But it did burst, General," went on the Admiral. "You can see for yourself," and he turned around and waved his hand toward the barbette where the gun had been mounted. All that remained of it now was part of the temporary carriage, and a small under-portion of the muzzle. The entire breech, with the great block, had been blown into fragments, so powerful was the powder used. The projectile one watcher reported, had gone about three hundred yards over the top of the barbette and then dropped into the sea, very little of the force of the explosive having been expended on that. A large piece of the gun had also been lost in the water off shore.

"My gun burst! My gun burst!" murmured General Waller, as if unable to comprehend it. "My gun burst—it is impossible!"

"But it did," spoke Admiral Woodburn, softly. "Come, you had better see the surgeon. You may be more seriously injured than you think."

"Was anyone else hurt?" asked the inventor, listlessly. He seemed to have lost all interest, for the time being.

"No one seriously, as far as we can learn," was the answer.

"What of the man who fired the gun?" inquired the General.

"He was blown high into the air," said Tom. "I saw him."

"But he is not injured beyond some bruises," put in one of the ambulance surgeons. "We have taken him to the hospital. He fell on a pile of bags that had held concrete, and they saved him. It was a miraculous escape."

"I am glad of it," said General Waller. "It is bad enough to feel that I made some mistake, causing the gun to burst; but I would never cease to reproach myself if I felt that the man who fired it was killed, or even hurt."

His friends led him away, and Tom and Ned went over to look at what remained of the great gun. Truly, the powder, expending its force in a direction not meant for it, had done terrific havoc. Even part of the solid concrete bed of the barbette had been torn up.

An official inquiry was at once started, and, while it would take some time to complete it (for the parts of the gun remaining were to be subjected to an exhaustive test to determine the cause of the weakness), it was found that there was some defect in the wiring and battery that was used to fire the charge.

The soldier who was to press the button was sure he had not done so, as he had been ordered to wait until General Waller gave the signal from the bomb-proof. But the gun went off before its inventor reached that place of safety. Just what had caused the premature discharge could never be learned, as part of the firing apparatus had been blown to atoms.

"Well, Tom, what do you think of it?" asked Ned, who had now fully recovered from the shock. The two were about to leave the proving grounds, having seen all that they cared to.

"I don't know just what to think," was the answer. "It sure was a big explosion, and it goes to prove that, no matter how many calculations you make, when you try a new powder in a new gun you don't know what's going to happen, until after it has happened—and then it's too late. It's a big problem, Ned."

"Do you think you can solve it? Are you still going on with your plan to build the biggest cannon ever made?"

"I sure am, Ned, though I don't know that I'll make out any better than General Waller did. It's too bad his was a failure; but I think I see where he made some mistakes."

"Oh, you do; eh?" suddenly exclaimed a voice, and from a nearby parapet, where he had gone to look at one of the pieces of his gun, stepped General Waller. "So you think I made some mistakes, Tom Swift? Where, pray?"

"In making the breech. The steel jackets were of uneven thickness, making the strain unequal. Then, too, I do not think the powder was sufficiently tested. It was probably of uneven strength. That is only my opinion, sir."

"Well, you are rather young to give opinions to men who have devoted almost all their lives to the study of high explosives."

"I realize that, sir; but you asked me for my opinion. I shall hope to profit by your mistakes, too. That is one reason I wanted to see this test."

"Then you are seriously determined to make a gun that you think will rival mine."

"I am, General Wailer."

"For what purpose—to sell to some foreign government?"

"No, sir!" cried Tom, with flashing eyes. "If I am successful in making a cannon that will fire the longest shots on record, I shall offer it to Uncle Sam first of all. If he does not want it, I shall not dispose of it to any foreign country!"

"Hum! Well, I don't believe you'll succeed. I intend to rebuild my gun at once, though I may make some changes in it. I am sure I shall succeed the next time. But as for you—a mere youth—to hope to rival men who have made this problem a life-study—it is preposterous, sir! Utterly preposterous!" and he uttered these words much as he had declared that it was impossible for his gun to burst, even after it was in fragments.

"Come on, Ned," said Tom, in a low voice. "We'll go back home."



CHAPTER IX

THE NEW POWDER

"Bless my cartridge belt, Tom, you don't really mean to say that stuff is powder!" exclaimed Mr. Damon.

"That's what I hope it will prove to be—and powerful powder at that."

"Why, it looks more like excelsior than anything else," went on the odd man, gingerly taking up some yellowish shreds in his fingers.

"And it will burn as harmlessly as excelsior in the open air," went on Tom. "But I hope to prove, when it is confined in a chamber, that it will be highly explosive. I'm going to make a test of it soon."

"Give me good notice, so I can get over in the next State!" exclaimed Ned Newton, with a laugh.

This was several days after our friends had returned from the disastrous gun test at Sandy Hook. Tom had at once gotten to work on the problem that confronted him—a problem of his own making—to build a giant cannon that would make the longest shots on record. And he had first turned his attention to the powder, or explosive, to be used.

"For," he said, "there is no use having a big gun unless you can fire it. And the gun I am planning will need something more powerful in the powder line than any I've ever heard of."

"Stronger than the kind General Wailer used?" inquired Ned.

"Yes, but I'll make my cannon correspondingly stronger, too, so there will be no danger."

"Bless my shoe buttons!" exclaimed Mr. Damon. "You boys must have had your nerve with you to stay around Sandy Hook after that gun went up in the air."

"Oh, the danger was all over soon after it began," spoke Tom, with a smile. "But now I'm going to test some of this powder. If you want to run away, Mr. Damon, I'll have Koku take you up in one of the airships, and you'll certainly be safe a mile or so in the air," for Tom had instructed his giant servant how to run one of the simpler biplanes.

"No—no, Tom, I'll stick!" exclaimed the eccentric man. "I'll not promise not to hide behind the fence, or something like that, though, Tom; but I'll stick."

"So will I," added Ned. "How are you going to make the test, Tom?"

"I'll tell you in a minute. I want to do a little figuring first."

Tom had, before going to Sandy Hook, made some experiments in powder manufacturing, but they had not been very satisfactory. He had not been able to get power enough. On his return he had undertaken rather a daring innovation. He had mingled two varieties of powder, and the resulting combination would, he hoped, prove just what he wanted.

The powder was in gelatin form, being made with nitro-glycerine as a base. It looked, as Mr. Damon had said, like a bunch of excelsior, only it was yellow instead of white, and it felt not unlike pieces of dry macaroni.

"I have shredded the powder in this manner," Tom explained, "so that it will explode more evenly and quickly. I want it to burn as nearly instantaneously as possible, and I think it will in this form."

"But how are you going to tell how powerful it is unless you fire it in a cannon?" asked Ned. "And you haven't even started your big gun yet."

"Oh, I'll show you," declared Tom. "There are several ways of making a test, but I have one of my own. I am going to take a solid block of steel, of known weight—say about a hundred pounds. This I will put into a sort of square cylinder, or well, closed at the bottom somewhat like the breech of a gun. The block of steel fits so closely in the square well that no air or powder gas can pass it.

"In the bottom of this well, which may be a foot square, I will put a small charge of this new powder. On top of that will come the steel block. Then by means of electric wires I can fire the charge.

"Attached to the steel well, or chamber, will be a gauge, a pressure recorder and other apparatus. When the powder, of which I will use only a pinch, carefully weighing it, goes off, it will raise the hundred-pound weight a certain distance. This will be noted on the scale. There will also be shown the amount of pressure released in the gas given off by the powder. In that way I can make some calculations."

"How?" asked Ned, who was much interested.

"Well, for instance, if one ounce of powder raises the weight three feet, and gives a muzzle pressure of, say, five hundred pounds, I can easily compute what a thousand pounds of powder, acting on a projectile weighing two tons and a half, would do, and how far it would shoot it."

"Bless my differential gear!" cried Mr. Damon. "A projectile weighing two and a half, tons! Tom, it's impossible!"

"That's what General Waller said about his gun; but it burst, just the same," declared Ned. "Poor man, I felt sorry for him. He seemed rather put out at you, Tom."

"I guess he was—a bit—though I didn't mean anything disrespectful in what I said. But now we'll have this test. Koku, take the rest of this powder back. I'll only keep a small quantity."

The giant, who, being more active than Eradicate, had rather supplanted the aged colored man, did as he was bid, and soon Tom, with Ned and Mr. Damon to help him, was preparing for the test.

They went some distance away from any of the buildings, for, though Tom was only going to use a small quantity of the explosive, he did not just know what the result would be, and he wanted to take no chances.

"I know from personal experience what the two kinds of powder from which I made this sample will do," he said; "but it is like taking two known quantities and getting a third unknown one from them. There is an unequal force between the two samples that may make an entirely new compound."

The steel chamber that was to receive the hundred-pound steel block had been prepared in advance, as had the various gauges and registering apparatus.

"Well, I guess we'll start things moving now," went on Tom, as he looked over the things he had brought from his shops to the deserted meadow. The fact of the test had been kept a secret, so there were no spectators. "Ned, give me a hand with this block," Tom went on. "It's a little too heavy to lift alone." He was straining and tugging at the heavy piece of steel.

"Me do!" exclaimed Koku the giant, gently pushing Tom to one side. Then the big man, with one hand, raised the hundred-pound weight as easily as if it were a loaf of bread, and deposited it where Tom wanted it.

"Thanks!" exclaimed our hero, with a laugh. "I didn't make any mistake when I brought you home with me, Koku."

"Huh! I could hab lifted dat weight when I was a young feller!" exclaimed Eradicate, who was, it is needless to say, jealous of the giant.

The powder had been put in the firing chamber. The steel socket had been firmly fixed in the earth, so that if the force of the explosion was in a lateral direction, instead of straight up, no damage would result. The weight, even if it shot from the muzzle of the improvised "cannon," would only go harmlessly up in the air, and then drop back. The firing wires were so long that Tom and his friends could stand some distance away.

"Are you all ready?" cried Tom, as he looked to see that the wiring was clear.

"As ready as we ever shall be," replied Mr. Damon, who, with Ned and the others, had taken refuge behind a low hill.

"Oh, this isn't going to be much of an explosion," laughed Tom. "It won't be any worse than a Fourth of July cannon. Here she goes!"

He pressed the electric button, there was a flash, a dull, muffled report and, for a moment, something black showed at the top of the steel chamber. Then it dropped back inside again.

"Pshaw!" cried Tom, in disappointed tones. "It didn't even blow the weight out of the tube. That powder's no good! It's a failure!"

Followed by the others, the young inventor started toward the small square "cannon." Tom wanted to read the records made by the gases.

Suddenly Koku cried:

"There him be, master! There him be!" and he pointed toward a distant path that traversed the meadow.

"He? Whom do you mean?" asked Tom, startled the giant's excited manner.

"That man what come and look at Master's new powder," was the unexpected answer. "Him say he want to surprise you, and he come today, but no speak. He run away. Look—him go!" and he pointed toward a figure of distinctly military bearing hurrying along the road that led to Shopton.



CHAPTER X

SOMETHING WRONG

"Bless my buttons!" cried Mr. Damon.

"Let's chase after him!" yelled Ned.

"Koku kin run de fastest oh any oh us," put in Eradicate. "Let him go."

"Hold on—wait a minute!" exclaimed Tom. "We want to know who that man is—and why we're going to chase after him. Koku, I guess it's up to you. Something has been going on here that I don't know anything about. Explain!"

"Well, it's no use to chase after him now," said Ned. "There he goes on his motor-cycle."

As he spoke the man, who, even from a rear view, presented all the characteristics of an army man, so straight was his carriage, leaped upon a motor-cycle that he pulled from the roadside bushes, and soon disappeared in a cloud of dust.

"No, he's gone," spoke Tom, half-regretfully. "But who was he, Koku? You seemed to know him. What was he doing out here, watching my test?"

"Me tell," said the giant, simply. "Little while after Master come back from where him say big gun all go smash, man come to shop when Master out one day. Him very nice man, and him say him know you, and want to help you make big cannon. I say, 'Master no be at home.' Man say him want to give master a little present of powder for use in new cannon. Master be much pleased, man say. Make powder better. I take, and I want Master to be pleased. I put stuff what man gave me in new powder. Man go away—he laugh—he say he be here today see what happen—I tell him you go to make test today. Man say Master be much surprised. That all I know."

Silence followed Koku's statement. To Ned and Mr. Damon it was not exactly clear, but Tom better understood his giant servant's queer talk.

"Is that what you mean, Koku?" asked the young inventor, after a pause. "Did some stranger come here one day when I was out, after I had made my new powder, and did he give you some 'dope' to put in it?"

"What you mean by 'dope'?"

"I mean any sort of stuff."

"Yes, man give me something like sugar, and I sprinkle it on new powder for to surprise Master."

"Well, you've done it, all right," said Tom, grimly. "Have you any of the stuff left?"

"I put all in iron box where Master keep new powder."

"Well, then some of it must be there yet. Probably it sifted through the excelsior-like grains of my new explosive, and we'll find it on the bottom of the powder-case. But enough stuck to the strands to spoil my test. I'll just take a reading of the gauges, and then we'll make an investigation."

Tom, with Ned to help him, made notes of how far the weight had risen in the tube, and took data of other points in the experiment.

"Pshaw!" exclaimed Tom. "There wasn't much more force to my new powder, doped as it apparently has been, than to the stuff I can buy in the open market. But I'm glad I know what the trouble is, for I can remedy it. Come on back to the shop. Koku, don't you ever do anything like this again," and Tom spoke severely.

"No, Master," answered the giant, humbly.

"Did you ever see this man before, Koku?"

"No, Master."

"What kind of a fellow was he?" asked Ned.

"Oh, him got whiskers on him face, and stand very straight, like stick bending backwards. Him look like a soldier, and him blink one eye more than the other."

Tom and Ned started and looked at one another.

"That description fits General Waller," said Ned, in a low voice to his chum.

"Yes, in a way; but it would be out of the question for the General to do such a thing. Besides, the man who ran away, and escaped on his motor-cycle, was larger than General Waller."

"It was hard to tell just what size he was at the distance," spoke Ned. "It doesn't seem as though he would try to spoil your experiments, though."

"Maybe he hoped to spoil my cannon," remarked Tom, with a laugh that had no mirth in it. "My cannon that isn't cast yet. He probably misunderstood Koku's story of the test, and had no idea it was only a miniature, experimental, gun.

"This will have to be looked into. I can't have strangers prowling about here, now that I am going to get to work on a new invention. Koku, I expect you, after this, not to let strangers approach unless I give the word. Eradicate, the same thing applies to you. You didn't see anything of this mysterious man; did you?"

"No, Massa 'Tom. De only s'picious man I see was mab own cousin sneakin' around mah chicken coop de odder night. I tooks mah ole shot gun, an' sa'ntered out dat way. Den in a little while dere wasn't no s'picious man any mo'."

"You didn't shoot him; did you, Rad?" cried Tom, quickly.

"No, Massa Tom—dat is, I didn't shoot on puppose laik. De gun jest natchelly went off by itself accidental-laik, an' it peppered him good an' proper."

"Why, Rad!" cried Ned. "You didn't tell us about this."

"Well, I were 'shamed ob mah cousin, so I was. Anyhow, I only had salt an' pepper in de gun—'stid ob shot. I 'spect mah cousin am pretty well seasoned now. But dat's de only s'picious folks I see, 'ceptin' maybe a peddler what wanted t' gib me a dish pan fo' a pair ob ole shoes; only I didn't hab any."

"There are altogether too many strangers coming about here," went on Tom. "It must be stopped, if I have to string charged electric wires about the shops as I once did."

They hurried back to the shop where the new powder was kept, and Tom at once investigated it. Taking the steel box from where it was stored he carefully removed the several handfuls of excelsior-like explosive. On the bottom of the box, and with some of it clinging to some of the powder threads, was a sort of white powder. It had a peculiar odor.

"Ha!" cried Tom, as soon as he saw it. "I know what that is. It's a new form of gun-cotton, very powerful. Whoever gave it to Koku to put on my powder hoped to blow to atoms any cannon in which it might be used. There's enough here to do a lot of damage."

"How is it that it didn't blow your test cylinder to bits?" asked Ned.

"For the reason that the stuff I use in my powder and this new gun-cotton neutralized one another," the young inventor explained. "One weakened the other, instead of making a stronger combination. A chemical change took place, and lucky for us it did. It was just like a man taking an over-dose of poison—it defeated itself. That's why my experiment was a failure. Now to put this stuff where it can do no harm. Is this what that man gave you, Koku?"

"That's it, Master."

There came a tap on the door of the private room, and instinctively everyone started. Then came the voice of Eradicate, saying:

"Dere's a army gen'men out here to see you. Massa Tom; but I ain't gwine t' let him in lessen as how you says so."

"An army gentleman!" repeated Tom.

"Yais, sah! He say he General Waller, an' he come on a motor-cycle."

"General Waller!" exclaimed Tom. "What can he want out here?"

"And on a motor-cycle, too!" added Ned. "Tom, what's going on, anyhow?"

The young inventor shook his head.

"I don't know," he replied; "but I suppose I had better see him. Here. Koku, put this powder away, and then go outside. Mr. Damon, you'll stay; won't you?"

"If you need me, Tom. Bless my finger nails! But there seems to be something wrong here."

"Show him in, Rad!" called Tom.

"Massa Gen'l Herodotus Waller!" exclaimed the colored man in pompous tones, as he opened the door for the officer, clad in khaki, whom Tom had last seen at Sandy Hook.

"Ah, how do you do, Mr. Swift!" exclaimed General Waller, extending his hand. "I got your letter inviting me to a test of your new explosive. I hope I am not too late."

Tom stared at him in amazement.



CHAPTER XI

FAILURE AND SUCCESS

"You—you got my letter!" stammered Tom, holding out his hand for a missive which the General extended. "I—I don't exactly understand. My letter?"

"Yes, certainly," went on the officer. "It was very kind of you to remember me after—well, to be perfectly frank with you, I did resent, a little, your remarks about my unfortunate gun. But I see you are of a forgiving spirit."

"But I didn't write you any letter!" exclaimed Tom, feeling more and more puzzled.

"You did not? What is this?" and the General unfolded a paper. Tom glanced over it. Plainly it was a request for the General to be present at the test on that day, and it was signed with Tom Swift's name.

But as soon as the young inventor saw it, he knew that it was a forgery.

"I never sent that letter!" he exclaimed. "Look, it is not at all like my handwriting," and he took up some papers from a near-by table and quickly compared some of his writing with that in the letter. The difference was obvious.

"Then who did send it?" asked General Waller. "If someone has been playing a joke on me it will not be well for him!" and he drew himself up pompously.

"If a joke has been played—and it certainly seems so," spoke Tom, "I had no hand in it. And did you come all the way from Sandy Hook because of this letter?"

"No, I am visiting friends in Waterford," said the officer, naming the town where Mr. Damon lived. "My cousin is Mr. Pierce Watkins."

"Bless my doorbell!" exclaimed Mr. Damon, "I know him! He lives just around the corner from me. Bless my very thumb prints!"

General Waller stared at Mr. Damon in some amazement, and resumed:

"Owing to the unfortunate accident to my gun, and to some slight injuries I sustained, I found my health somewhat impaired. I obtained a furlough, and came to visit my cousin. The doctor recommended open air exercise, and so I brought with me my motor-cycle, as I am fond of that means of locomotion."

"I used to be," murmured Mr. Damon; "but I gave it up."

"After his machine climbed a tree," Tom explained, with a smile, remembering how he had originally met Mr. Damon, and bought the damaged machine from him, as told in the first volume of this series.

"So, when I got your letter," continued the General, "I naturally jumped on my machine and came over. Now I find that it is all a hoax."

"I am very sorry, I assure you," said Tom. "We did have a sort of test today; but it was a failure, owing to the fact that someone tampered with my powder. From what you tell me, I am inclined to the belief that the same person may have sent you that letter. Let me look at it again," he requested.