Victor Appleton.......................................................................................................................................1

CHAPTER I. ON A LIVE WIRE ............................................................................................................1

CHAPTER II. "WE'LL TAKE A CHANCE!"........................................................................................6

CHAPTER III. PLANNING A BIG GUN..............................................................................................9

CHAPTER IV. KOKU'S BRAVE ACT ................................................................................................12

CHAPTER V. OFF TO SANDY HOOK..............................................................................................16

CHAPTER VI. TESTING THE WALLER GUN.................................................................................19

CHAPTER VII. THE IMPOSSIBLE OCCURS ....................................................................................23

CHAPTER VIII. A BIG PROBLEM .....................................................................................................26

CHAPTER IX. THE NEW POWDER..................................................................................................28

CHAPTER X. SOMETHING WRONG ................................................................................................31

CHAPTER XI. FAILURE AND SUCCESS.........................................................................................34

CHAPTER XII. A POWERFUL BLAST ..............................................................................................38

CHAPTER XIII. CASTING THE CANNON.......................................................................................41

CHAPTER XIV. A NIGHT INTRUDER ..............................................................................................45

CHAPTER XV. READY FOR THE TEST ...........................................................................................47

CHAPTER XVI. A WARNING ............................................................................................................51

CHAPTER XVII. THE BURSTING DAM ...........................................................................................54

CHAPTER XVIII. THE DOPED POWDER .........................................................................................59

CHAPTER XIX. BLOWING DOWN THE BARRIER ........................................................................62

CHAPTER XX. THE GOVERNMENT ACCEPTS.............................................................................64

CHAPTER XXI. OFF FOR PANAMA .................................................................................................67

CHAPTER XXII. AT GATUN LOCKS...............................................................................................71

CHAPTER XXIII. NEWS OF THE MINE...........................................................................................74

CHAPTER XXIV. THE LONGEST SHOT ..........................................................................................76

CHAPTER XXV. THE LONGLOST MINE......................................................................................81

"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 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 littleheardof island goes them one better."

"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 islandsomewhere down near Panama, you say

it isand try to locate the lost mine from which, some centuries ago, opals and other precious stones came. It

"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 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

"I've heard you talk the same way before, Alec," he replied. "None of your schemes ever amounted to

anything. You've been a fortunehunter all your life, nearly; and what have you gotten out of it? Just a bare

"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

"Yes, only to lose it because the missing heirs turned up, and took it away from you. You could have made

"Yes, I suppose I could; but this is going to be a successI 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, comedo! For the sake of old times. Don't you recall how you and I used to prospect together out in

"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 schemedo!"

"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!

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

"Spoil Tom Swift? You couldn't do it in a hundred years!" cried Mr. Damon, enthusiastically. "Bless my

"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 minehunt

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

"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

"Cannon it was, Mr. Swift," said Mr. Damon. "Tom has an idea that he can make the biggest cannon in the

"Well, then I guess there's no hope of my interesting him in my opal mine," said the fortunehunter, with

"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

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

"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

"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

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

"But not businessgood," declared Mr. Swift, and for some time the three argued the matter, Mr. Swift

"Why, what's the matter, Eradicate?" asked Mr. Swift, leaping to his feet, an example followed by the other

"I dunno, Massa Swift, but I looked up jest now, an' dere he be, in dat aircontraption 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

ashootin' outer de airship suffin' scandalous! It's jest spittin' fire, dat's what it's adoin', 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

"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

"Now doan't yo' go t' gittin' all excitedlaik," objected Eradicate Sampson, the aged colored man. "Remember

Mr. Swift ran from the room, followed by Mr. Damon and Mr. Peterson, while Eradicate trailed after them as

"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

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.

"Keep back! Don't come too close!" yelled the young inventor, as he clung to the seat of the aeroplane, that

"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!"

"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

"Yes, shut it off if you can!" Tom shouted back. "But be careful. Don't get shocked! Wow! I got a touch of it

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

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

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

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

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

"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

"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 themthey 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

"Heah dey be! Heah dey be!" cried Eradicate, as he produced a heavy pair from his pocket. "II couldn't

find de canopener fo' Mrs. Baggert, an' I jest got yo' pliers, Massa Tom. Oh, how glad I is dat I did. Here's

He handed them to the fortunehunter, 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

"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 rubbergloved 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

workshop 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

"Thanks, Mr. Peterson!" exclaimed the young inventor, as he left his seat and walked up to the

fortunehunter. "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

"I'm glad I could help you, Tom," spoke the other, warmly. "I was afraid that if you had to wait until they

"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.

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

"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 midway to the powerhouse, and retraced his steps. "Let's carry him into the house. Bless my

They lifted the inert form of our hero and walked toward the mansion with him, Mrs. Baggert, the

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 MotorCycle," and this machine was the means of his

becoming acquainted with Mr. Wakefield Damon, the odd gentleman who so often blessed things. On his

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

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 crafta regular skyracer. 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.

In the household, beside his father, himself and Mrs. Baggert, was Eradicate Sampson, an aged colored

manofallwork, 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

Mr. Damon was, with Ned Newton, Tom's chum, the warmest friend of the family, and was often at Tom's

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

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

"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.

"Nono," faintly murmured Tom, opening his eyes. "II've had enough of that, if you please! I'm all

"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

"An' ef he hadn't abeen there to cotch yo' all," put in Eradicate, "yo' all suah would hab hit de ground mighty

"That's two services he did for me today," said Tom, as he managed to sit up. "Cutting that wirewell, it

"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 overI

"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 rightsee," and he proved

"He's ail rightdon't come, doctor," said Mr. Damon into the telephone. "Bless my keyring!" he exclaimed,

"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

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

"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

"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

"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 farby 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."

Mr. Peterson was an old friend, and when he and Mr. Swift were young men they had prospected and

grubstaked together. But Mr. Swift soon gave that up to devote his time to his inventions, while Mr.

He was a good man, but somewhat visionary, and a bit inclined to "take chances"such as looking for lost

treasurerather than to devote himself to some steady employment. The result was that he led rather a

"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 goodbye, 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,

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

"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 younot that I

didn't beforebut 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, eitherthough I don't believe

"You won't throw it away in this case!" declared Mr. Peterson, eagerly. "I'm sure to find that mine; but it will

"Well, I'll supply it to the extent of ten thousand dollars," said Mr. Swift. "Tom, what do you think of it? Am

"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'twell, I would have supplied the money myselfthat's all," and he smiled at the

"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

"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

The two young menNed Newton being Tom's special chumwere talking together over Tom's latest

It was several days after Tom's accident in the airship, when he had been saved by the prompt action of Mr.

Peterson. That fortunehunter, 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

"Bless my watch chain!" exclaimed that odd gentleman. "I would like to go with you first rate. But I'm so

busyso 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 itahem!"

"Oh, well, perhaps I could get a few weeks off. But I'm not goingno, bless my check book, I must get back

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

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

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

"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 sixteeninch rifled

cannonthat 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

"And yet you are figuring on making a cannon with a muzzle thirty inches acrossalmost a yardand fifty

"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

"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

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 becomeif she is not alreadya worldpower. Now that canal has to be

protectedI mean against the possibility of war. For, though it may never come, and the chances are it never

"Uncle Sam has to be ready for it. There never was a more true saying than 'in time of peace prepare for war.'

"Once the Panama Canal is in operation, and the worldchanges incidental to it have been made, if it should

pass into the hands of some foreign countryas it very possibly might dothe United States would not only

"Now, then, to protect the canal, several things are necessary. Among them are big gunscannon that can

shoot a long distance for if a foreign nation should send some of their new dreadnaughts over

herevessels with guns that can shoot many mileswhere would the canal be once a bombardment was

opened? It would be ruined in a daythe immense lockgates 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

"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!"

"Yes, I'm going to invent a cannon that will make the longest shots on record. I'm going to make a

worldbeater gun; or, rather, I'm going to invent it, and have it made, for I guess it would tax this place to the

"I've been thinking of this for some time, Ned. I've been puttering around inventing new magnetos,

potatoparers and the like, but this is my latest hobby. The Panama Canal is a big thingone of the biggest

"And, listen: Uncle Sam thinks the same way. I understand that the best men in the serviceat West Point,

Annapolis and Sandy Hook, as well as elsewhereare 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

"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

talentssuch as they areto Uncle Sam. I'm going to make the biggest cannon in the worldthe one that

will shoot the farthest and knock into smithereens all the other big guns. That's the only way to protect the

"Somewhat, Tom. Since I gave up my place in the bank, and became a sort of handylad 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

"Right away. I'm making some plans now. I'm going down to Sandy Hook and witness the test of this new

"'Scuse me, Massa Tom," broke in Eradicate, as he put his head through the halfopened 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

'dangerousexplosivean' keep away fom de fire.' He want t' know what he all gwine t' do wif 'em, Massa

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

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

"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,

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

"Tom! Tom!" cried Ned, as he watched the disappearing figure of his chum. "Come back here! If there's

"I'm not running away!" flashed back Tom. "I'm going to get that powder out of the auto before it goes up! If

"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

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

"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

Ned had now reached the front door of the shop. He had a glimpse of the burning autoa small express

truck, well loaded with various packages. And, through the smoke, which from the odor must have been

"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

"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 tailboard. 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

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

"Nono water!" yelled Tom, who heard him. "Water will only make it worseit'll scatter the blazing

gasoline. The feed pipe from the tank must have burst. Throw on sandsand 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

"We've got to be lively, then, Ned!" gasped Tom. "This is getting hotter every minute! Where's that Koku?

Ned glanced around to see if he could catch a glimpse of the big man whom Tom had brought from Giant

"Let's have another try now, Ned!" suggested Tom, when a shift in the wind left the rear of the auto

"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

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

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

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

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

"Koku!" cried Tom. "Quick! Never mind the shovel! Get those powder boxes out of that cart before they go

"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

Then, carrying the box, which was now burning quite fiercely on one corner, over toward Tom and Ned, who

"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

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.

"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

"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 lastit 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

"Yes, and I'm mighty glad I'm here to sign for it," replied the young inventor. "Now, Koku, I guess you can

"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?"

"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.

"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

"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."

"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 onceto get instantaneous action. It must all

"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 jackstraws are piled up. In fact, some of the new powder looks

like jackstraws. Some, as this, for instance, looks like macaroni. Other is in cubes, and some in long

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

"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 explosionthat's all."

"Yesthat's all," remarked Ned, grimly, as he nervously watched the burning stick of powder. Tom let it

"You know what a little puff black gunpowder gives, if you burn some openly on the ground," went on Tom;

"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

"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

"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

"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

Tom was interrupted by the postman's whistle, and a little later Eradicate came in with the mail that had been

"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.

"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

"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 permitI guess I'll put it where it won't get lost," and

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

"What's the idea of this government test of the big gun, Tom?" asked Ned. "I got so excited about that

nearexplosion 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.

"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

"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.

"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

fortynine miles long, you know, and it will take many guns to cover the whole route, as well as to protect

"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

"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

"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

"Not very much. I have heard that it is not quite as large as the old sixteeninch 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.

"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

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

"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

paperfigured 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 middlesized

"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

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

"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 nitroglycerine, which was the basis of the powder. Dynamite will often produce a headache

This long, necklike strip of land on the New Jersey coast is, as most of you know, one of the principal

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 lifesaving 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

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

twentyone 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

"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

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

"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 breechblock 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 togglejointed arms, so that the muzzle

was above the bombproof 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

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

"Are these the proving grounds?" asked Tom. "This is the entrance to them," replied the soldier, bringing his

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

"No, it has to be countersigned by General Wailer. And, as he's on the proving grounds now, you can't see

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

"I can't leave my post," replied the sentry, shortly. "You'll have to come another time, when the General isn't

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

"I don't think so," replied the sentry. "And I'll have to ask you to leave this vicinity. No strangers are allowed

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 bombproof around the testing

"Just trying some of the big guns," explained the sentry, who was not a badnatured chap. He had to do his

duty. "You'd better move on," he suggested. "If anything happens the government isn't responsible, you

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

"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

"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

"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.

"Oh, that's all right, Flynn," said Captain Badger. "It isn't your fault, of course. I suppose there is no rule

"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

"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

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

"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 countersigned 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 smallcalibre 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

"Stand on your tiptoes, and open your mouth when you see a big cannon about to be fired," advised Captain

"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 earthe 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.

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

"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

"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 longmuch longer in proportion than guns of greater

"He is," answered Captain Badger. "Some of us think he is going to use too much, but he says it is impossible

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

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

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 breechloading 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 powderhundreds of pounds of itand then it is necessary to

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

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

waythe projectile or the block. In most cases the projectile gracefully bows, so to speak, and skips out of

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

"I'm afraid, General, that you are using too much of that strong powder," Tom heard one officer say to the

"Nonsense, Colonel Washburn. I tell you it is impossible to burst my gunimpossible, sir! I have allowed

for every emergency, and calculated every strain. I have a margin of safety equal to fifty per cent."

"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

"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

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

"Sir! Do you know what you are saying? How did you come in here, anyhow? I thought no civilians were to

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

"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 yearTom and his big searchlight. Mr. Swift, General Waller,"

"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

"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

There were murmurs throughout the throng about the big gun, as the officer approached Tom Swift and

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

"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

"II haven't had the pleasure of meeting Mr. Swift before," said the gun inventor, stiffly. "I did not

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

"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

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

"I don't know that I will need anyas 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

"Very good, sir," spoke the officer in immediate charge of the matter, as he saluted. Soon from the aerials

I might explain that near the spot where the projectile was expected to fall into the seaabout fifteen miles

from Sandy Hookseveral 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

"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 breechblock 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 bombproof, whence they would watch the effect of the fire, and note the

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

"He would beif it exploded," spoke Tom, for his officer friends had joined their colleagues, most of whom

"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 breechblock 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

"Oh, yesmuch," 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

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 bombproof, within which were gathered his

"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

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

How it happened was never accurately known, as the soldier declared positivelyafter he came out of the

hospitalthat he had not pressed the button. The theory was that the wires had become crossed, making a

But suddenly, while Tom, Ned and General Waller were still some distance away from the bombproof,

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

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 bombproof. Even as Tom struggled to his

feet, intending to run to safety in fear of other explosions, he realized what had happened.

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

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

"Look out!" Tom yelled, instinctively, as he staggered toward the bombproof, 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

Tom Swift bent anxiously over the prostrate form of his chum. A big piece of the burst gun had fallen close

to Nedso close, in fact, that Tom, who saw it as he neared the entrance to the bomb proof, shuddered as

"Nono, I guess not," he answered, slowly. "II guess I'm as much scared as hurt, Tom. It was the wind

"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 Nedso 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

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

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

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.

"Nothat is to say, I don't think so. But what happened? Did they fire some other gun in our direction by

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

"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 underportion 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

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

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

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

"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

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 bombproof. 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

"Well, Tom, what do you think of it?" asked Ned, who had now fully recovered from the shock. The two

"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

"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

"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,

"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,

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

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

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

"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

"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 youa mere youthto hope to rival men

who have made this problem a lifestudyit 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."

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

"Why, it looks more like excelsior than anything else," went on the odd man, gingerly taking up some

"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 hima 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

"For," he said, "there is no use having a big gun unless you can fire it. And the gun I am planning will need

"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

"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

"Nono, Tom, I'll stick!" exclaimed the eccentric man. "I'll not promise not to hide behind the fence, or

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,

The powder was in gelatin form, being made with nitroglycerine 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

"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

"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 weightsay 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

"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 hundredpound

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."

"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

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

"That's what General Waller said about his gun; but it burst, just the same," declared Ned. "Poor man, I felt

"I guess he wasa bitthough 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

The steel chamber that was to receive the hundredpound steel block had been prepared in advance, as had

"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

"Me do!" exclaimed Koku the giant, gently pushing Tom to one side. Then the big man, with one hand, raised

the hundredpound 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,

"Huh! I could hab lifted dat weight when I was a young feller!" exclaimed Eradicate, who was, it is needless

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.

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

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

He pressed the electric button, there was a flash, a dull, muffled report and, for a moment, something black

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

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

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

"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. Lookhim go!" and he pointed toward a figure

"Hold onwait a minute!" exclaimed Tom. "We want to know who that man isand 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

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

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 motorcycle that he pulled from the roadside bushes, and soon

"No, he's gone," spoke Tom, halfregretfully. "But who was he, Koku? You seemed to know him. What was

"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 awayhe 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.

Silence followed Koku's statement. To Ned and Mr. Damon it was not exactly clear, but Tom better

"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?"

"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?"

"Well, then some of it must be there yet. Probably it sifted through the excelsiorlike grains of my new

explosive, and we'll find it on the bottom of the powdercase. 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

"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.

"Oh, him got whiskers on him face, and stand very straight, like stick bending backwards. Him look like a

"Yes, in a way; but it would be out of the question for the General to do such a thing. Besides, the man who

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

"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,

"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

"No, Massa Tomdat is, I didn't shoot on puppose laik. De gun jest natchelly went off by itself

"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

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 excelsiorlike explosive. On

the bottom of the box, and with some of it clinging to some of the powder threads, was a sort of white

"Ha!" cried Tom, as soon as he saw it. "I know what that is. It's a new form of guncotton, 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.

"For the reason that the stuff I use in my powder and this new guncotton 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 overdose of poisonit defeated

itself. That's why my experiment was a failure. Now to put this stuff where it can do no harm. Is this what

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

"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

"I don't know," he replied; "but I suppose I had better see him. Here. Koku, put this powder away, and then

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

"Massa Gen'l Herodotus Waller!" exclaimed the colored man in pompous tones, as he opened the door for the

"Ah, how do you do, Mr. Swift!" exclaimed General Waller, extending his hand. "I got your letter inviting

"Youyou got my letter!" stammered Tom, holding out his hand for a missive which the General extended.

"Yes, certainly," went on the officer. "It was very kind of you to remember me afterwell, 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

"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.

"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

"Then who did send it?" asked General Waller. "If someone has been playing a joke on me it will not be well

"If a joke has been playedand it certainly seems so," spoke Tom, "I had no hand in it. And did you come

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

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

"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 motorcycle, as I am fond of that means of locomotion."

"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 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

"I should say that was written in a sort of German hand; would you not also?" he asked of Mr. Damon.

At the mention of the word "German" Koku, the giant, who had entered the room, to be stared at in

"German man give me stuff for to put in your powder. I 'member now, he talk like Hans who make our

Quickly Tom told of the visit of an unknown man who had prevailed on the simpleminded giant to "dope"

Tom's new powder under the impression that he was doing his master a favor. Then the flight of the spy on a

"We have a German gardener," went on Tom, "and Koku now recalls that our mysterious visitor had the same

"Let me see," murmured General Waller. "In the first place your test failsyou learn, then, that your powder

has been tampered withyou see a man riding away in haste after having, in all likelihood, spied on your

workyour giant servant recalls the visit of a mysterious man, and, when the word 'German' is pronounced

in his hearing he recalls that his visitor was of that nationality. So far so good.

"I come to this vicinity for my health. That fact, as are all such regarding officers, was doubtless published in

the Army and Navy Journal, so it might easily become known to almost anyone. I receive a letter which I

think is from Tom Swift, asking me to attend the test. As the distance is short I go, only to find that the letter

"It is part of my training, I suppose," remarked the officer. "But it strikes me that if we find your German spy,

Tom, we will find the man who played the joke on me. And if I do find him well, I think I shall know how

to deal with him," and General Waller assumed his characteristic haughty attitude.

"I believe you are right, General," spoke Tom. "Though why any German would want to prevent my

experiments, or even damage my property, and possibly injure my friends, I cannot understand."

"I am sorry you have had your trouble for nothing," went on Tom. "And, if you are in this vicinity when I

conduct my next test, I shall be glad to have you come. I will send word by Mr. Damon, and then there will

"Thank you, Tom, I shall be glad to come I do not know how long I shall remain in this vicinity. If I knew

where to look for the German I would make a careful search. As it is, I shall turn this letter over to the United

States Secret Service, and see what its agents can do. And, Tom, if you are annoyed again, let me know. You

are a sort of rival, so to speak, but, after all, we are both working to serve Uncle Sam. I'll do my best to

"Thank you, sir," replied Tom. "On my part, I shall keep a good lookout. It will be a bold spy who gets near

my shop after this. I'm going to put up my highlycharged protecting electric wires again. We were just

talking about them when you came in. Would you like to look about here, General?"

"No, but I am working on the plans. I want first to decide on the kind of explosive I am to use, so I can make

"A wise idea. I think there is where I made my mistake. I did not figure carefully enough on the strength of

material. The internal pressure of the powder I used, as well as the muzzle velocity of my projectile, were

both greater than they should have been. Take a lesson from my failure. But I am going to start on another

General Waller was much interested in going about Tom's shop, and expressed his surprise at the many

inventions he saw. While ordnance matters, big guns and high explosives were his hobby, nevertheless the

"Oh, by keeping at it," was the modest answer. "Then my good friends hereNed and Mr. Damonhelp

"Bless my check book!" exclaimed the odd gentleman. "It is very little help I give, Tom."

General Waller soon took his departure, promising to call again, to see Tom's test if one were held. He also

repeated his determination to set the Secret Service men at work to discover the mysterious German.

"It would seem so," remarked Ned. "That man doped Tom's powder, hoping to make it so powerful that it

would blow up everything. Then he sends word to the General to be present. If there had been a blowup he

"Well, we'll see if we can ferret him out!" spoke the officer as he took his leave.

"I wonder if we could trace that man who rode away on the motorcycle?" said Ned.

"We'll try," decided Tom, energetically, and in the electric runabout, that had once performed such a service

to his father's bank, the young inventor and his chum were soon traversing the road taken by the spy. They

got some traces of himthat is, several persons had seen him passbut that was all. So they had to record

"I wonder if the General himself could have sent that letter?" mused Ned, as they returned home.

"He might have," went on Ned, coolly. "You see, Tom, he admits that he was jealous of you. Now what is

there to prevent him from hiring someone to dope your powder, and then, to divert suspicion from himself,

"But if he did thatwhich I don't believewhy would he come when there was danger, in case his trick

"Ah, but you notice he didn't arrive until after danger of an explosion had passed," commented Ned.

"Well, maybe not," replied Ned. "But it's worth thinking about. I believe if General Waller could prevent you

The days that followed were busy ones for Tom. He worked on the powder problem from morning to night,

scoring many failures and only a few successes. But he did not give up, and in the meanwhile drew tentative

One evening, after a hard day's work, he went to the library where his father was reading.

"Tom," said Mr. Swift, "do you remember that old fortune hunter, Alec Peterson, who wanted me to go into

"No, he writes to say he reached the island safely, and has been working some time. He hasn't had any

"That's just like him," murmured Tom. "Well, Dad, if you lose the ten thousand dollars I guess I'll have to

"Look out with that box, Koku! Handle it as though it contained a dozen eggs of the extinct great auk, worth

"Eradicate! Don't you dare stumble while you're carrying that tube. If you do, you'll never do it again!"

Thus Eradicate answered the young inventor, while the giant, Koku, who was carrying a heavy case, nodded

It was one afternoon, about two weeks after Tom had made his first test of the new powder. Now, after much

hard work, and following many other tests, some of which were more or less successful, he had reached the

point where he believed he was on the threshold of success. He had succeeded in making a new explosive

that, in the preliminary tests, in which only a small quantity was used, gave promise of being more powerful

than any Tom had ever experimented withhis own or the product of some other inventor.

And his experiments had not always been harmless. Once he came within a narrow margin of blowing up the

shop and himself with it, and on another occasion some of the slowburning powder, failing to explode, had

Only for the prompt action of Koku, Tom might have been seriously injured. As it was he lost some valuable

But he had gone on his way, surmounting failure after failure, until now he was ready for the supreme test.

This was to be the explosion of a large quantity of the powder in a specially prepared steel tube of great

thickness. It was like a miniature cannon, but, unlike the first small one, where the test had failed, this one

would carry a special projectile, that would be aimed at an armor plate set up on a big hill.

Tom's hope was that this big blast would show such pressure in foottons, and give such muzzle velocity to

the projectile, and at the same time such penetrating power, that he would be justified in taking it as the basis

The preliminaries had been completed. The special steel tube had been constructed, and mounted on a heavy

carriage in a distant part of the Swift grounds. A section of armor plate, a foot and a half in thickness, had

been set up at the proper distance. A new projectile, with a hard, penetrating point, had been madea sort of

Now the young inventor and his friends were on their way to the scene of the test, taking the powder and

other necessaries, including the primers, with them. Tom, Ned and Mr. Damon had some of the gauges to

"So General Waller won't be here?" remarked Ned, as they walked along, Tom keeping a watchful eye on

"No," was the reply. "He has gone back to Sandy Hook. He wrote that his health was better, and that he

"I guess he's afraid you'll beat him out, Tom," laughed Ned. "You take my advice, and look out for General

"I'se lookin' out, Massa Tom. Golly, I don't laik dis yeah job at all! II guess I'd better be gittin' at dat

"Never you mind about the whitewashing, Rad. You just stick around here for a while. I may need you to sit

"Sit on a cannon, Massa Tom! Say, looky heah now! You jest take dese primary things from dish yeah coon.

"Why, what's the matter, Rad? Surely you're not afraid; are you?" and Tom winked at Ned.

"No, Massa Tom, I'se not prezactly 'skeered, but I done jest 'membered dat I didn't gib mah mule Boomerang

any oats t'day, an' he's suahly gwine t' be desprit mad at me fo' forgettin' dat. I I'd better go!"

"Nonsense, Rad! I was only fooling. You can go as soon as we get to my private proving grounds, if you like.

But you'll have to carry those primers, for all the rest of us have our hands full. Only be careful of 'em!"

They kept on, and it was noticed that Mr. Damon gave nervous glances from time to time in the direction of

Koku, who was carrying the box of powder. The giant himself, however, did not seem to know the meaning

of fear. He carried the box, which contained enough explosive to blow them all into fragments, with as much

"Now you can go, Rad," announced Tom, when they reached the lonely field where, pointing toward a big

"Good, Massa Tom!" cried the colored man, and from the way in which he hurried off no one would ever

"Say, that stuff looks just like Swiss cheese," remarked Ned, as Tom opened the box of explosive. It would be

incorrect to call it powder, for it had no more the appearance of gunpowder, or any other "powder," than, as

And, indeed, the powerful stuff bore a decided resemblance to that peculiar product of the dairy. It was in

"The idea is," Tom explained, "to make a quickburning explosive. I want the concussion to be scattered

through it all at once. It is set off by concussion, you see," he went on. "A sort of cartridge is buried in the

middle of it, after it has been inserted in the cannon breech. The cartridge is exploded by a primer, which

responds to an electric current. The thin plates, with holes corresponding to the centre hole in a big grain of

the hexagonal powder, will, I hope, cause the stuff to burn quickly, and give a tremendous pressure. Now

Even Tom was a little nervous as he prepared for this latest test. But he was not nervous enough to drop any

of those queer, cheeselike slabs. For, though he knew that a considerable percussion was needed to set them

off, it would not do to take chances. High explosives do not always act alike, even under the same given

conditions. What might with perfect safety be done at one time, could not be repeated at another. Tom knew

The powder, as I shall occasionally call it for the sake of convenience, though it was not such in the strict

sense of the wordthe powder was put in the small cannon, together with the primer. Then the wires were

"But we won't attach the battery until the last moment," Tom said. "I don't want a premature explosion."

The projectile was also put in, and Tom once more looked to see that the armor plate was in place. Then he

adjusted the various gauges to get readings of the power and energy created by his new explosive.

"Well, I guess we're all ready," he announced to his friends. "I'll hook on the battery now, and we'll get off

behind that other hill. I had Koku make a sort of cave therea miniature bombproof, that will shelter us."

"Do you think the blast will be powerful enough to make it necessary?" asked Mr. Damon.

"It will, if this larger quantity of explosive acts anything like the small samples I set off," replied the young

The electric wires were carried behind the protecting hill, whither they all retired.

His thumb pressed the electric button, and instantly the ground shook with the tremor of a mighty blast, while

a deafening sound reared about them. The earth trembled, and there was a big sheet of flame, seen even in the

"Come on!" yelled Ned. "We'll see how this experiment came out!" and he started to run from beneath the

"Some of that powder may not have exploded," went on the young inventor. "From the sound made I should

say the gun burst, and, if it did, that gelatin is bound to be scattered about. There may be a mass of it burning

loose somewhere, and it may go off. It ought not to, if my theory about it being harmless in the open is

Anxiously they lingered, the echoes of the blast still in their ears, and a peculiar smell in their nostrils.

"But there's no smoke," said Mr. Damon. "Bless my spyglass! I always thought there was smoke at an

"This is a sort of smokeless powder," explained Tom. "It throws off a slight vapor when it is ignited, but not

He dropped the pushbutton connected with the igniting battery, and, followed by the others, raced to the

A great hole had been torn in the hillside, and another where the improvised gun had stood. The gun itself

"Burst to pieces I guess," replied Tom. "I was afraid that charge was a bit too heavy."

"No, here it is!" shouted Mr. Damon, circling off to one side. "It's been torn from the carriage, and partly

It was as he had said. The terrific blast had sheared the gun from its temporary carriage, thrown it into the air,

and it had come down to bury itself in the soft ground. The carriage had torn loose from the concrete base,

"Is the gun shattered?" asked Tom, anxious to know how the weapon had fared. It was, in a sense, a sort of

"The breech is cracked a little," answered Mr. Damon, who was examining it; "but otherwise it doesn't seem

"Good cried Tom. "Another steel jacket will remedy that defect. I guess I'm on the right road at last. But now

"Dinner plate not here," spoke Koku, who could not understand how there could be two kind of plates in the

world. "Dinner plate gone, but big hole here, and he indicated one in the side of the hill.

"I expect that is where the armor plate is," said Tom, trying not to laugh at the mistake of his giant servant.

"Take a look in there, Koku, and, if you can get hold of it, pull it out for us. I'm afraid the piece of

Koku disappeared into the miniature cave that had been torn in the side of the bill. It was barely large enough

to allow him to go in. But Tom knew none other of them could hope to loosen the piece of steel, imbedded as

Presently they heard Koku grunting and groaning. He seemed to be having quite a struggle.

Then came a shout, as though in anger Koku had dared the buried plate to defy him. There was a shower of

earth at the mouth of the cave, and the giant staggered out with the heavy piece of armor plate. At the sight of

"Look!" he shouted. "My projectile went part way through and then carried the plate with it into the side of

It was as he had said. The projectile, driven with almost irresistible force, had bitten its way through the

armor plate, but a projection at the base of the shell had prevented it from completely passing through. Then,

with the energy almost unabated, the projectile had torn the plate loose and hurled it, together with its own

body, into the solid earth of the hillside. There, as Koku held them up, they could all see the shell imbedded

in the plate, the point sticking out on the other side, as a boy might spear an apple with a sharp stick.

"It sure is," agreed Ned. "Tom, my boy, I guess you can now make the longest shots on record."

"I can as soon as I get my giant cannon, perhaps," admitted the young inventor. "I think I have solved the

An examination of the gauges, which, being attached to the cannon and plate by electric wires, were not

damaged when the blast came, showed that Tom's wildest hopes had been confirmed. He had the most

powerful explosive ever madeor at least as far as he had any knowledge, and he had had samples of all the

Concerning Tom's powder, or explosive, I will only say that he kept the formula of it secret from all save his

father. All that he would admit, when the government experts asked him about it, later, was that the base was

not nitroglycerine, but that this entered into it. He agreed, however, in case his gun was accepted by the

But Tom's work was only half done. It was one thing to have a powerful explosive, but there must be some

means of utilizing it safelysome cannon in which it could be fired to send a projectile farther than any

Tom figured and planned, far into the night, for many weeks after that. He had to begin all over again,

working from the basis of the power of his new explosive. And he had many new problems to figure out.

But finally he had constructedon papera gun that was to his liking. The most exhaustive figuring proved

that it had a margin of safety that would obviate all danger of its bursting, even with an accidental

"No; it would be out of the question for me. I haven't the facilities. I'm going to give the contract to the

But even the great facilities of the steel corporation proved almost inadequate for Tom's giant cannon. When

he showed the drawings, on which he had already secured a patent, the manager balked.

"Oh, yes, you can!" declared Tom, who had inspected the plant. "I'll show you how."

"Why, we haven't a mould big enough for the central core," was another objection.

"Then we'll make one," declared Tom "We'll dig a pit in the earth, and after it is properly lined we can make

"Of course it can!" cried Tom. "Do you think you can shrink on the jackets, and rifle the central tube?"

"Oh, yes, we can do that. The initial cast was what stumped me. But we'll go ahead now."

"And you can wind the breech with wire, and braze it on; can't you?" persisted Tom.

"That, in combination with a steeljacketed one. I'm going to take no chances with 'Swiftite'!" laughed Tom,

for so he had named his new explosive, in honor of his father, who had helped him with the formula.

I am not going to tire my readers with the details leading up to the casting of Tom's big cannon. Sufficient to

say that the general plan, in brief, was this: A hole would be dug in the earth, in the center of the largest

casting shopa hole as deep as the gun was to be long. This was about one hundred feet, though the gun,

when finished, would be somewhat shorter than this. An allowance was to be made for cutting.

In the center of this hole would be a small "core" made of asbestos and concrete mixed. Around this would be

poured the molten steel from great caldrons. It would flow into the hole. The sides of earthlined with

fireclaywould hold it in, and the middle core would make a hole throughout the length of the central part

of the gun. Afterward this hole would be bored and rifled to the proper calibre.

After this central part was done, steel jackets or sleeves would be put on, redhot, and allowed to shrink.

Then would come a winding of wire, to further strengthen the tube, and then more sleeves or jackets. In this

As the greatest pressure would come at the breech, or in the powder chamber there, the gun would be thickest

It took many weary weeks to get ready for the first cast, but finally Tom received word that it was to be

made, and with Ned, and Mr. Damon, he proceeded to the plant of the steel concern.

There was some delay, but finally the manager gave the word. Tom and his friends, standing on a high

gallery, watched the tapping of the combined furnaces that were to let the molten steel into the caldrons.

There were several of these, and their melted contents were to be poured into the mould at the same time.

Out gushed the liquid steel, giving off a myriad of sparks. The workers, as well as the visitors, had to wear

"Hoist away!" cried the manager, and the electric cranes started off with the caldrons of liquid fire, weighing

"Pour!" came the command, and into the pit in the earth splashed the melted steel that was to form the big

cannon. From each caldron there issued a stream of liquid metal of intense heat. There were numerous

"So far so good!" exclaimed the manager, with a sigh of relief as the last of the melted stuff ran into the

mould. "Now, when it cools, which won't be for some days, we'll see what we have."

"I hope it contains no flaws," spoke Tom, "That is the worst of big gunsyou never can tell when a flaw will

Tom was interrupted by the sound of a dispute at one of the outer doors of the shop.

"But I tell you I must go inI belong here in!" a voice cried. It had a German accent, and at the sound of it

"Oh, a crazy German. He belongs in one of the other shops, and I guess he's mixed up. He thinks he belongs

"That is right," remarked the manager. "I gave orders, at your request," he said to Tom, "that no one but the

men in this part of the plant were to be present at the casting. I cant understand what that fellow wanted."

"Tom, aren't you going to try to get a look at that German?" whispered Ned, as he and his chum came down

from the elevated gallery at the conclusion of the cast. "I mean the one who tried to get in!"

"I'd like to, Ned, but I don't want to arouse any suspicion," replied Tom. "I've got to stay here a while yet, and

arrange about shrinking on the jackets, after the core is rifled. I don't see how"

"I'll slip out and see if I can get a peep at him," went on Ned. "If it's like the one Koku described, we'll know

"I will," promised Tom's chum. So, while the young inventor was busy arranging details with the steel

manager, Ned slipped out of a side door of the casting shop, and looked about the yard. He saw a little group

"I dell you dot is my shop!" one of the men was heard to exclaima man whom the others appeared to

"And I tell you, Baudermann, that you're mistaken!" insisted one, evidently a foreman. "I told you to work in

the brazing department. What do you want to try to force your way into the heavy casting department for?

Especially when we're doing one of the biggest jobs that we ever handledmaking the new Swift cannon."

"Oh, iss dot vot vas going on in dere?" asked the man addressed as Baudermann. "Shure den, I makes a

misdake. I ask your pardon, Herr Blackwell. I to mine own apartment will go. But I dinks my foreman sends

me to dot place," and he indicated the casting shop from which he had just been barred.

"All right!" exclaimed the foreman. "Don't make that mistake again, or I'll dock you for lost time."

"Only just a twisted German employee, I guess," thought Ned, as he was about to turn back. "I was mistaken.

He passed by the group of men, who, laughing and jeering at the German, were showing him where to go. He

But as Ned passed he got one look at the man's face. Instead of a stupid countenance, for one instant he had a

glimpse of the sharpest, brightest eyes he had ever looked into. And they were hard, cruel eyes, too, with a

glint of daring in them. And, as Ned glanced at his figure, he thought he detected a trace of military

stiffnessnone of the stoopshouldered slouch that is always the mark of a moulder. The fellow's hands,

too, though black and grimy, showed evidences of care under the dirt, and Ned was sure his uncouth language

"I'd like to know more about you," murmured Ned, but the man, with one sharp glance at him, passed on,

"Nothing very definite, but I'm sure there was something back of it all, Tom. I wouldn't be surprised but what

that fellow whoever he waswhatever his object washoped to get in to see the casting; either to get

There was nothing more to be done at present, and, as it would take several days for the big mass of metal to

There Tom busied himself over many things. Ned helping him, and Mr. Damon lending an occasional hand.

Koku was very useful, for often his great strength did what the combined efforts of Tom and his friends could

As for Eradicate, he "puttered around," doing all he could, which was not much, for he was getting old. Still

Tom would not think of discharging him, and it was pitiful to see the old colored man try to do things for the

young inventortasks that were beyond his strength. But if Koku offered to help, Eradicate would draw

"Git away fom heah! I guess dish yeah coon ain't forgot how t' wait on Massa Tom. Go 'way, giant. I ain't so

big as yo'all, but I know de English language, which is mo' 'n yo' all does. Go on an' lemme be!"

"Well, Ned," remarked Tom one day, after the visit of the postman, "I have a letter from the steel people.

They are going to take the gun out of the mould tomorrow, and start to rifle it. We'll take a run down in the

airship, and see how it looks. I must take those drawings, too, that show the new plan of shrinking on the

Tom and Ned occupied adjoining and connecting apartments, for, of late, Ned had taken up his residence

with his chum. It was shortly after midnight that Ned was awakened by hearing someone prowling about his

room. At first he thought it was Tom, for the shorter way to the bath lay through Ned's apartment, but when

the lad caught the flash of a pocket electric torch he knew it could not be Tom.

Tom Swift acted promptly, for he realized the necessity. The events that had hedged him about since he had

begun work on his giant cannon made him suspicious. He did not quite know whom to suspect, nor the

reasons for their actions, but he had been on the alert for several days, and was now ready to act.

The instant Ned answered as he did, and warned Tom, the young inventor slid his hand under his pillow and

pressed an auxiliary electric switch he had concealed there. In a moment the rooms were flooded with a

bright light, and the two lads had a momentary glimpse of an intruder making a dive for the window.

"What do you want?" demanded Tom, instinctively. But the intruder did not stay to answer.

Instead, he made a dive for the casement. It was one story above the ground, but this did not cause him any

hesitation. It was summer, and the window was open, though a wire mosquito net barred the aperture. This

As Ned and Tom leaped from their beds, Ned catching up the heavy, empty water pitcher as a weapon, and

Tom an old Indian war club that served as one of the ornaments of his room, the fellow, with one kick, burst

Then, clambering out on the sill, he dropped from sight, the boys hearing him land with a thud on the turf

below. It was no great leap, though the fall must have jarred him considerably, for the boys heard him grunt,

"Quick!" cried Ned. "Ring the bell for Koku, Ned. I want to capture this fellow if possible."

There was an electric bell from Tom's room to the apartment of his big servant, and a speaking tube as well.

While Ned was pressing the button, and hastily telling the giant what had happened, urging him to get in

pursuit of the intruder, Tom had taken from his bureau a powerful, portable, electric flash lamp, of the same

variety as that used by the wouldbe thief. Only Tom's was provided with a tungsten filament, which gave a

And in this glare the young inventor saw, speeding away over the lawn, the form of a big man.

"So I see. Koku will be right on the job. I told him not to dress. Can you make out who the fellow is?"

"No, his back is toward us. But he's limping, all right. I guess that jump jarred him up a bit. Where is Koku?"

"There he goes now!" exclaimed Ned, as a figure leaped from the side door of the housea gigantic figure,

"Let's go out and lend a hand!" suggested Ned, looking at the water pitcher as though wondering what he had

"I'm with you," agreed Tom. "Only I want to get into something a little more substantial than my pajamas."

As the two lads hurriedly slipped on some clothing they heard the voice of Mr. Swift calling:

"Nothing much," was the reassuring answer. "It was a near happening, only Ned woke up in time. Someone

"A burglar! Good land a massy!" cried Eradicate, who had also gotten up to see what the excitement was

"Koku? Huh, he nebber cotch anybody. I'se got t' git out dere mahse'f! Koku? Hu! I s'pects it's dat no'count

cousin ob mine, arter mah chickens ag'in! I'll lambaste dat coon when I gits him, so I will. I'll cotch him for

yo'all, Massa Tom," and, muttering to himself, the aged colored man endeavored to assume the activity of

"Hark!" exclaimed Ned, as he and Tom were about ready to take part in the chase. "What's that noise, Tom?"

"It's the same chap!" interrupted Tom. "No use trying to chase him on that speedy machine. He's a mile away

from here by now. He must have had it in waiting, ready for use. But come on, anyhow."

It was as Tom had suspected. The deadly, charged wires, that formed a protecting cordon about his shops,

had been cut, and that by an experienced hand, probably by someone wearing rubber gloves, who must have

come prepared for that very purpose. During the night the current was supplied to the wires from a storage

battery, through an intensifying coil, so that the charge was only a little less deadly than when coming direct

"It does, but wait until we get inside and look around. I'm glad I took my gunplans to the house with me."

But a quick survey of the shop did not reveal any damage done, nor had anything been taken, as far as Tom

could tell. The office of his main shop was pretty well upset, and it looked as though the intruder had made a

"It was the gunplans he was after, all right," decided Tom. "And I believe it was the same fellow who has

"I don't know who he is, but he evidently wants my plans. Probably he's a disappointed inventor, who has

been trying to make a gun himself, and can't. He wants some of my ideas, but he isn't going to get them.

Well, we may as well get back to bed, after I connect these wires again. I must think up a plan to conceal

While Tom and Ned were engaged on this, Koku came back, much out of breath, to report:

"Hu! Ef I had de fust chanst at him, I'd a cotched dat coon suab!" declared Eradicate, following the giant.

"That's all right, Rad," consoled Tom. "You did your best. Now we'll all get to bed. I don't believe he'll come

Tom and Ned were up at the first sign of daylight, for they wanted to go to the steel works, some miles away,

in time to see the cannon taken out of the mould, and preparations made for boring the rifle channels. They

"Some of my men are as interested in this as you are," he said to the young inventor. "A number of them

declare that the cast will be a failure, while some think it will be a success."

"I think it will be all right, if my plans were followed," said Tom. "However, we'll see. By the way, what

"Why, it's rather queer about him. The foreman of the shop where he was detailed, saw that he was an

experienced man, in spite of his seemingly stupid ways, and he was going to promote him, only he never

"I mean the day after the cast of the gun was made he disappeared, and never came back."

"Oh!" exclaimed Tom. He said nothing more, but he believed that he understood the man's actions. Failing to

obtain the desired information, or perhaps failing to spoil the cast, he realized that his chances were at an end

With great care the gun was hoisted from the mould. More eyes than Tom's anxiously regarded it as it came

"Bless my buttonhook!" cried Mr. Damon, who had gone with the lads. "It's a monster; isn't it?"

"Oh, wait until you see it with the jackets on exclaimed Ned, who had viewed the completed drawings. "Then

The great piece of hollow steel tubing was lifted to the boring lathe. Then Tom and the manager examined it

"And that was the hardest part of the work," went on the manager of the steel plant. "I can almost guarantee

And, as far as the rifling was concerned, this was true. I will not weary you with the details of how the great

core of Tom Swift's giant cannon was bored. Sufficient to say that, after some annoying delays, caused by

breaks in the machinery, which had never before been used on such a gigantic piece of work, the rifling was

done. After the jackets had been shrunk on, it would be rifled again, to make it true in case of any shrinkage.

Then came the almost Herculean task of shrinking on the great redhot steel jackets and wirewindings, that

would add strength to the great cannon. To do this the central core was set up on end, and the jackets, having

been heated in an immense furnace, were hoisted by a great crane over the core, and lowered on it as one

It took weeks of hard work to do this, and Tom and Ned, with Mr. Damon occasionally for company,

remained almost constantly at the plant. But finally the cannon was completed, the rifling was done over

"You cannon is completed, Mr. Swift. I want to congratulate you on it. Never have we done such a

stupendous piece of work. Only for your plans we could not have finished it. It was too big a problem for us.

Your cannon is completed, but, of course, it will have to be mounted. What about the carriage?"

"I have plans for that," replied Tom; "but for the present I am going to put it on a temporary one. I want to

test the gun now. It looks all right, but whether it will shoot accurately, and for a greater distance than any

"That is what we must decide. I don't want to take it too far from here. Perhaps you can select a place where it

"Oh, I'm not altogether sure that it will go that distance," interrupted Tom, with a smile; "but I'm going to try

"Then I must get back and arrange for my powder supply," went on the young inventor. "We'll soon test my

"Bless my eardrums!" cried Mr. Damon. "I hope nothing bursts. For if that goes up, Tom Swift"

"I'm not making it to burst," put in Tom, with a smile. "Don't worry. Now, Ned, back to Shopton to get ready

"And it doesn't seem to show any signs of letting up," remarked Tom. "It's been at it nearly a week now, and

"Bless my rubber boots! it's just got to stop some time," declared Mr. Damon. "Don't worry, Tom."

"But I don't like this delay. I have heard that General Waller has perfected a new gunand it's a fine one,

from all accounts. He has the proving grounds at Sandy Hook to test his on, and I'm handicapped here. He

"Oh, I hope not, Tom!" exclaimed Ned. "I'm going to see what the weather reports say," and he went to hunt

It was several weeks after the completion of Tom's giant cannon. In the meanwhile the gun had been moved

by the steel company to a littleinhabited part of New York State, some miles from the plant. The gun had

been mounted on an improvised carriage, and now Tom and his friends were waiting anxiously for a chance

The work was not complete, for the steel company employees had been hampered by the rain. Never before,

it seemed, had there been so much water coming down from the clouds. Nearly every day was misty, with

gradations from mere drizzles to heavy downpours. There were occasional clear stretches, however, and

A few more days of clear weather would be needed before the gun could be fastened securely to the carriage,

and then Tom could fire one of the great projectiles that had been cast for it. Not until then would he know

Meanwhile nothing more had been heard or seen of the spy. He appeared to have given up his attempts to

The place of the test, as I have said, was in a deserted spot. On one side of a great valley the gun was being

set up. Its muzzle pointed up the valley, toward the side of a mountain, into which the gigantic projectile

could plow its way without doing any damage. Tom was going to fire two kinds of cannon ballsa solid

The gun was so mounted that the muzzle could be elevated or depressed, or swung from side to side. In this

way the range could be varied. Tom estimated that the greatest possible range would be thirty miles. It could

not be more than that, he decided, and he hoped it would not be much less. This extreme range could be

attained by elevating the gun to exactly the proper pitch. Of course, any shorter range could, within certain

The gun was pointed slantingly up the valley, and there was ample room to attain the thirtymile range

At the head of the valley, some miles from where the giant cannon was mounted, was an immense dam, built

recently by a water company for impounding a stream and furnishing a supply of drinking water for a distant

city. At the other end of the valley was the thriving village of Preston. A railroad ran there, and it was to

Preston station that Tom's big gun had been sent, to be transported afterward, on specially made trucks,

Tom had been obliged to buy a piece of land on which to build the temporary carriage, and also contract for a

large slice of the opposite mountain, as a target against which to fire his projectiles.

The valley, as I have said, was desolate. It was thickly wooded in spots, and in the centre, near the big dam,

which held back the waters of an immense artificial lake, was a great hill, evidently a relic of some glacial

Tom, Ned, Mr. Damon, with Koku, and some of the employees of the steel company, had hired a deserted

farmhouse not far from the place where the gun was being mounted. In this they lived, while Tom directed

"The paper says 'clear' tomorrow," read Ned, on his return. "'Clear, with freshening winds.'"

"That means rain, with no wind at all," declared Tom, with a sigh. "Well, it can't be helped. As Mr. Damon

"Bless my overshoes!" exclaimed the odd gentleman. "It always has cleared; hasn't it?"

There came a slackening in the showers, and Tom and Ned, donning raincoats, went out to see how the work

was progressing. They found the men from the steel concern busy at the great piece of engineering.

"We could finish it in two days if this rain would only let up," replied the man.

"If it doesn't, there's likely to be trouble up above," went on the foreman, nodding in the direction of the great

"They evidently didn't count on one like this. They've got the engineer who built it up there, and they're doing

their best to strengthen it. I also heard that they're preparing to dynamite it to open breeches here and there in

"You don't mean it! Say, if it does go out with a rush it will wipe out the village."

"Yes, but it can't hurt us," went on the foreman. "We're too high up on the side of the hill. Even if the dam did

burst, if the course of the water could be changed, to send it down that other valley, it would do no harm, for

It was near this hill that Tom intended to direct his projectiles, and on the other side of it was another valley,

As the foreman had said, if the waters (in case the dam burst) could be turned into this transverse valley, the

"But it would take considerable digging to open a way through that side of the mountain, into the other

"Yes," said Tom, and then he gave the matter no further thought, for something came up that needed his

"Have you your explosive here?" asked the foreman of the young inventor the next day, when the weather

"Yes, some of it," said Tom. "I have another supply in a safe place in the village. I didn't want to bring too

much here until the gun was to be fired. I can easily get it if we need it. Jove! I wish it would clear. I want to

get out in my Humming Bird, but I can't if this keeps up." Tom had brought one of his speedy little airships

The following day the clouds broke a little, and on the next the sun shone. Then the work on the gun went on

"Well, I think we can try a shot tomorrow!" announced Tom with delight on the evening of the first clear day,

"Yes, the gun is all in place," went on the young inventor. "Of course, it's only a temporary carriage, and not

the disappearing one I shall eventually use. But it will do. I'm going to try a shot tomorrow. Everything is in

There came a knock on the door of the room Tom had fitted up as an office in the old farmhouse.

"If it is, we'll be ready for him," murmured his chum. "Show him in, Koku, and you come in too."

But the man who entered at once disarmed suspicion. He was evidently a workman from the dam above, and

"Why? Because our dam is going to burst within a few hours. I've been sent to warn the folks in town in time

to let them take to the hills. You'd better move your outfit. The dam can't last twentyfour hours longer!"

"I sure do!" went on the man who had brought the startling news. "And the folks down below aren't going to

have any more time than they need to get out of the way. They'll have to lose some of their goods, I reckon.

But I thought I'd stop on my way down and warn you. You'd better be getting a hustle on."

"No danger!" cried the man. "Say, when that water begins to sweepdown here nothing on earth can stop it.

That big gun of yours, heavy as it is, will be swept away like a straw, I knowI saw the Johnstown flood!"

"But we're so high up on the side of the hill, that the water won't come here," put in Ned. "We had that all

figured out when we heard the dam was weak. We're not in any danger; do you think so, Tom?"

"Well, I hardly do, or I would not have set the gun where I did. Tell me," he went on to the man, "is there any

"There is, but the openings are not enough with such a flood as this. The engineers never counted on so much

rain. It's beyond any they ever had here. You see, there was a small creek that we dammed up to make our

lake. Some of the water from the spillway flows into that now, but its channel won't hold a hundredth part of

"You'd better move, I tell you. The dam is slowly weakening. We've done all we can to save it, but that's out

of the question. The only thing to do is to run while there's time. We've tried to make additional openings, but

we daren't make any more, or the wall will be so weakened that it will go out in less than twenty four hours.

"You've had your warning, now profit by it!" he added. "I'm going to tell those poor souls down in the valley

"If the dam bursts and the water could only be turned over into the transverse valley, this one would be safe,"

"Yes, but it can't be done!" the messenger exclaimed. "Our engineers thought of that, but it would take a

"Yes, you have," agreed Tom, "and if any damage comes to us it will be our own fault. But I don't believe

"It may not, but, if it does, we'll be safe. I have had a look at the water, and there's no chance for it to rise

here, even if the whole dam went out at once, which is not likely. Don't worry. We'll be all right."

"Bless my checkbook!" cried Mr. Damon. "But what about those poor people in the valley?"

"They will have time to flee, and save their lives," spoke the young inventor; "but they may lose their homes.

They can sue the water company for damages, though. Now don't do any more worrying, but get to bed, and

be ready for the test tomorrow. And the first thing I do I'm going to have a little flight in the Humming Bird

to get my nerves in trim. This long rain has gotten me in poor shape. Koku, you must be on the alert tonight. I

Certainly the next day, bright and sunshiny as it broke, had in it little of impending disaster. The weather was

fine after the longcontinued rains, and the whole valley seemed peaceful and quiet. At the far end could be

seen the great dam, with water pouring over it in a thin sheet, forming a small stream that trickled down the

But, through great pipes that led to the drinking system, though they were unseen, thundered immense

streams of solid water, reducing by as much as the engineers were able the pressure on the concrete wall.

Tom and Ned, in the Humming Bird, took a flight out to the dam shortly after breakfast, when the steel men

were putting a few finishing touches to the gun carriage, ready for the test that was to take place about noon.

"It doesn't look as though it would burst," observed Ned, as the aircraft hovered over the big artificial lake.

"No," agreed Tom. "But I suppose the engineers want to be on the safe side in case of damage suits. I want to

take a look at the place where the other valley comes up to this at right angles."

He steered his powerful little craft in that direction, and circled low over the spot.

"A bursting projectile, about where that big white stone is, would do the trick," murmured Tom.

"Oh, I guess I was talking to myself," admitted Tom, with a laugh. "I may not have to do it, Ned."

"Well, you're talking in riddles today, all right, Tom. When you get ready to put me wise, please do."

"I will. Now we'll get back, and fire our first long shot. I do hope I make a record."

There was much to be done, in spite of the fact that the foreman of the steel workers assured Tom that all was

in readiness. It was some time that afternoon when word was given for those who wished to retire to an

improvised bombproof. Word had previously been sent down the valley so that no one, unless he was

looking for trouble, need be in the vicinity of the gun, nor near where the shots were to land.

Through powerful glasses Tom and Ned surveyed the distant mountain that was to be the target. Several great

squares of white cloth had been put at different bare spots to make the finding of the range easy.

"I guess we're ready now," announced the young inventor, a bit nervously. "Bring up the powder, Koku."

"Me bring," exclaimed the giant, calmly, as he went to the bombproof where the powerful explosive was

The great projectile was in readiness to be slung into the breech by means of the hoisting apparatus, for it

weighed close to two tons. It was carefully inserted under Tom's supervision. It carried no bursting charge,

for Tom's first shot was merely to establish the extreme range that his cannon would shoot.

"Now the powder," called the young inventor. To avoid accidents Koku handled this himself, the hoisting

apparatus being dispensed with. Tom figured out that five hundred pounds of his new, powerful explosive

would be about the right amount to use, and this quantity, divided into several packages to make the handling

"Bless my doormat!" cried Mr. Damon, who stood near, looking nervously on. "Don't drop any of that."

Tom was busily engaged in figuring on a bit of paper, and Ned, who looked over his shoulder, saw a

complicated compilation that looked to he a combination of geometry, algebra, differential calculus and other

"I'm trying to confirm my own theories by means of figures, to see if I can really reach that farthest target."

"We'll see," replied Tom, quietly. "Put in the primer, Ned; and, Koku, close the breech and slot it home."

"Now," said Tom, "this thing may be all right, and it may not. The only thing that can cause an accident will

be a flaw in the steel. No one can guard against that. So, in order to be on the safe side, we will all go into the

They all agreed that this was good advice, and soon the steel men and Tom's friends were gathered in a sort

of cave that had been hollowed out in the side of the hill, and at an angle from the big gun.

"If it does burstwhich I hope it won't," said Tom, "the pieces will fly in straight lines, so we will be safe

"I want you to note the registered muzzle velocity. Mr. Damon, you will please read the pressure gauge. After

I press the button I'm going to watch the landing of the projectile through the telescope."

The gun had been pointed, as I have said, at the farthest targetone thirty miles away, telescope sights on

There was a tense moment; Tom's thumb pressed home the electric button, and then came the explosion.

It seemed for a moment as if everyone was lifted from his feet. They had all stood on their tiptoes, and

opened their mouths to lessen the shock, but even then it was terrific. The very ground shookfrom the roof

of their cave small stones and gravel rattled down on their heads. Their eardrums were numbed from the

shock. And the noise that filled the valley seemed like a thousand thunderbolts merged into one.

Tom rushed from the bombproof, dropping the electric button. He caught sight of his gun, resting undisturbed

"Hurray!" he cried in delight. "She stood the charge all right. And look! look!" he cried, as he pointed the

glasses toward the distant hillside. "There goes my projectile as straight as an arrow. There! By Caesar, Ned!

It landed within three feet of the target! Oh, you beauty!" he yelled at his giant cannon. "You did all I hoped

you would! Thirty miles, Ned! Think of that! A two ton projectile being shot thirty miles!"

"It's great, Tom!" yelled his chum, clapping him on the back, and capering about. "It's the longest shot on

"It certainly is," declared the foreman of the steel workers, who had helped in casting many big guns. "No

"Bless my armor plate!" gasped Mr. Damon. "What attacking ship against the Panama Canal could float after

"Not one," declared Tom; "especially after I put a bursting charge into the projectile. We'll try that next."

By means of compressed air the gases and some particles of the unexploded powder were blown out of the

big cannon. Then it was loaded again, the projectile this time carrying a bursting charge of another explosive

Once more they retired to the bombproof, and again the great gun was fired. Once more the ground shook,

Then, as they looked toward the distant hillside, they saw a shower of earth and great rocks rise up. It was

like a sand geyser. Then, when this settled back again, there was left a gaping hole in the side of the

The last shot did not go quite as far as the first, but it was because a different kind of projectile was used.

Tom was perfectly satisfied, however. Several more trials were given the gun, and each one confirmed the

The muzzle velocity and the pressure were equal to Tom's highest hopes. He knew, now, that he had hit on

just the right mixture of powder, and that his gun was correctly proportioned. It showed not the slightest

"Now we'll try another bursting shell," he said, after a rest, during which some records were made. "Then

we'll call it a day's work. Koku, bring up some more powder. I'll use a little heavier charge this time."

It was while the gun was being loaded that a horseman was seen riding wildly down the valley. He was

"It looks as though he was coming to give us a warning," suggested the steel foreman.

He looked at the horseman anxiously. The rider came nearer and nearer, wildly waving his flag. He seemed to

be shouting something, but his words could not be made out. Finally he came near enough to be heard.

"The dam! The dam!" he cried. "It's bursting. Your shots have hastened it. The cracks are widening. You'd

"I was afraid of this!" murmured Tom. "But, since our shots have hastened the disaster, maybe we can avert

"I'll show you. All hands come here and we'll shift this gun. I want it to point at that big white stone!" and he

indicated an immense boulder, well up the valley, near the place where the two great gulches joined.

"What are you going to do, Tom?" cried Ned, as he, with the others, worked the hand gear that shifted the big

gun. When it was permanently mounted electricity would accomplish this work. "What's your game, Tom?"

"Don't you remember, Ned? When we were talking about the chance of the dam bursting, I said if the current

of suddenly released water could be turned into the other valley, the people below us would be saved."

"Well, that's what I'm going to do. I'm going to fire a bursting shell at the point where the two valleys come

"If we can turn enough of the water into the other valley, where no one lives, and where it can escape into the

big river there, the amount that will flow down this valley will be so small that only a little damage will be

"That's right!" declared the steel foreman, as he caught Tom's idea. "It's the only way it could be done, too,

for there won't be time to make the necessary excavation any other way. Is the gun swung around far enough,

"No, a little more toward me," answered Tom, as he peered through the telescope sights. "There, that will do.

Now to get the proper elevation," and he began to work the other apparatus, having estimated the range as

In a few seconds the giant cannon was properly trained on the white rock. Meanwhile the horseman, with his

red flag, had continued on down the valley. In spite of his warning of the night before, it developed that a

number had disregarded it, and had remained in their homes. Most of the inhabitants, however, had fled to the

hills, to stay in tents, or with such neighbors as could accommodate them. Some lingered to move their

It was to see that the town was deserted by these latestayers that the messenger rode, crying his warning as

"The projectile!" cried Tom, as he saw that all was in readiness. "Lively now! I can see the top of the dam

The projectile, with a heavy charge of bursting powder, was slung into the breech of the gun.

"Now the powder, Koku!" called Tom. "Be quick; but not so fast that you drop any of it."

"Me fetch," responded the giant, as he hastened toward the small cave where the explosive was kept. As the

big man brought the first lot, and Ned was about to insert it in the breech of the gun, behind the projectile,

"Just let me have a look at that. It's some that I first made, and I want to be sure it hasn't gone stale."

Critically he looked at the powerful explosive. As he did so a change came over his face.

"By Jove!" muttered Tom. "There's been some trick played here!" and he set off on a run toward the

"The powder has been doped!" yelled Tom. "Something has been put in it to make it nonexplosive. It's no

good. It wouldn't send that shell a thousand yards, and it's got to go five miles to do any good. My plan won't

"I don't know. There must have been some spy at work. Quick, run and ask the foreman if any of his men are

missing. I'll see if there's enough of the good powder left to break down the barrier!"

Ned was away like a shot, while the others, not knowing what to make of the strange conduct of the two lads,

looked on in wonder. Tom raced toward the cave where the powder was stored, Koku following him.

They gazed to where he pointed. In several places the concrete spillway had crumbled down to a ragged edge,

showing that the solid wall was giving way. The amount of water flowing over the dam was greater now. The

creek was steadily rising. Down the valley the horseman with the red flag was but a speck in the distance.

"What can I do? What can I do?" murmured Tom. "If all the powder there is left has been doped, I can't save

Ned had reached the foreman, who, with his helpers, was standing about the big gun.

"Schlichter went yesterday," said the timekeeper. "I thought he was in quite a hurry to get his money, too."

"Schlichter gone!" exclaimed the foreman. "He was no good anyhow. I think he was a sort of Anarchist;

always against the government, the way he talked. So he has left; eh? But what's the matter, Ned?"

"Something wrong with the powder. Tom can't shoot the cannon and turn aside the water to save the town.

Some of his enemies have been at work. Schlichter leaving at this time, and in such hurry, makes it look

"It sure does! And, now I recall it, I saw him yesterday near your powder magazine. I called him down for it,

for I knew Tom Swift had given orders that only his own party was to go near it. So the powder is doped;

"Yes, one man has disappeared. Oh, Tom, we've got to fail after all! We can't save the town!"

"I mean that I have another supply of good powder in the village. I secreted some there, you remember I told

you. If I can go get that, and get back here in time, I can break down the barrier with one shot, and save

"But you never can make the trip there and back in time, with the powder, Tom. It's impossible. The dam

"I can't? Well, I'm going to make a big try, Ned. You stay on the job here. Have everything ready so that

when I get back with the new explosive, which I hope hasn't been tampered with, I can shove it into the

"Where are you going?" gasped his chum. "You can never run to Preston and back in time."

"I don't intend to. I'm going in my airship. Koku, never mind bringing the rest of the powder from the cave.

It's no good. Run out the Humming Bird. I'm going to drive her to the limit. I've just got to get that powder

"Bless my timetable!" gasped Mr. Damon. "That's the only way it can be done. Lucky Tom brought the

The young inventor, pausing only to get some cans for the explosive, and some straps with which to fasten

The motor was adjusted; Koku whirled the propeller blades. There was a staccato succession of explosions, a

rushing, roaring sound, and then the craft rose like a bird, and Tom circled about, making a straight course for

the distant town, while below him the creek rose higher and higher as the dam continued to crumble away.

"Not a thing, Mr. Damon. Waithold onno! It's only a bird," and the lad lowered the glasses with which

he had been sweeping the sky. looking for his chum returning in his airship with the powder.

"He'd better hurry," murmured the foreman. "That dam can't last much longer. The water is rising fast. When

"Bless my insurance policy!" cried Mr. Damon. "Don't say such things, my friend."

"But they're true!" insisted the man. "You can see for yourself that the cracks in the dam are getting larger. It

will be a big flood when it does come. And I'm not altogether sure that we're safe up here," he added, as he

looked down the sides of the hill to where the creek was now rapidly becoming a raging torrent.

"I don't want to be a calamity howler," went on the foreman; "but we've got to face this thing. We'd better get

ready to vamoose if Tom Swift doesn't reach here in time to fire that shotand he doesn't seem to be in

Once more Ned swept the sky with his glasses. The roar of the water below them could be plainly heard now.

"I wish I could get hold of that rascally German," muttered the foreman. "I'd give him more than a piece of

my mind. It will be his fault if the town is destroyed, for Tom's plan would have saved it. I wonder who he

"Some spy," declared Ned. "We've been having trouble right along, you know, and this is part of the game. I

have some suspicions, but Tom doesn't agree with me. Certainly the fellow, whatever his object, has made

"Look, Ned!" cried Mr. Damon. "Is that a bird; or is it Tom?" and he pointed to a speck in the sky. Ned

"Thank Heaven for that!" exclaimed Mr. Damon, fervently, forgetting to bless anything on this occasion. "If

"He's driving her to the limit!" cried Ned, still watching his chum through the glass. "He's coming!"

"He'll need to," murmured the foreman, grimly. "That dam can't last ten minutes more. Look at the people

He pointed to the north, and a confused mass of small black objectsmen, women and children, doubtless,

who had lingered in spite of the other warningcould be seen clambering up the sides of the valley.

"Everything," answered Ned, whom Tom had instructed in all the essentials. "As soon as he lands we'll jam

"I hope he doesn't land too hard, with all that explosive on board," murmured the foreman.

They looked up. The distant throb of the monoplane's motor could now be heard above the roar of the

swollen waters. Tom could be seen in his seat, and beside him, in the other, was a large package.

Nearer and nearer came the monoplane. It began to descend, very gently, for well Tom Swift knew the danger

He described a circle in the air to check his speed. Then, gently as a bird, he made a landing not far from the

gun, the craft running easily over one of the few level places on the side of the hill. Tom yanked on the brake,

and the ironshod pieces of wood dug into the ground, checking the progress of the monoplane on its bicycle

"I don't know," spoke Tom. "I didn't have time to look. I just rushed up to where I had stored it, got some out

and came back with the motor at full speed. Ran into an airpocket, too, and I thought it was all up with me

when I began to fall. But I managed to get out of it. Say, we're going to have it nip and tuck here to save the

"That's what!" agreed the foreman, as he helped Koku take the cans of explosive.

"Wait until I look at it," suggested Tom, as he opened one. His trained eye and touch soon told him that this

"It's all right!" he shouted. "Into the gun with it, and we'll see what happens."

It was the work of only a few moments to put in the charge. Then, once more, the breechblock was slotted

Tom Swift took one last look through the telescope sights of his giant cannon. He changed the range slightly

by means of the hand and wormscrew gear, and then, with the others, ran to the shelter of the cave. For,

though the gun had stood the previous tests well, Tom had used a heavier charge this time, both in the firing

"All ready?" asked the young inventor, as he looked around at his friends gathered in the cave.

Tom hesitated a moment, then, as his fingers stiffened to press the electric button there sounded to the ears of

Tom pressed the button. Once again was that awful tremor of the earththe racking shakethe terrific

"All right!" shouted Tom. "The gun held together. It's safe to go out. We'll see what happened!"

They all rushed from the shelter of the cave. Before them was an aweinspiring sight. A great wall of water

was coming down the valley, from a large opening in the centre of the dam. It seemed to leap forward like a

Tom declared afterward that he saw his projectile strike the barrier that separated one valley from the other,

but none of the others had eyessight as keen as thisand perhaps Tom was in error.

But there was no doubt that they all saw what followed. They heard a distant report as the great projectile

burst. Then a wall of earth seemed to rise up in front of the advancing wall of water. High into the air great

For a moment it was as though that wall of water hesitated, not deciding whether to continue on down the

populated valley, or to swing over into the other gash where it could do comparatively little harm. It was a

Then, as Tom's great shot had, by means of the exploding projectile, torn down the barrier, the water chose

the more direct and shorter path. With a mighty roar, like a distant Niagara, it swept into the new channel the

young inventor had made. Into the transverse valley it tumbled and tossed in muddy billows of foam, and

"Whew! Let me sit down somewhere and get my breath!" gasped Tom, when it was all over.

"I should think you would want a bit of quiet," replied Ned. "You've been on the jump since early morning."

"Bless my diningroom table!" cried Mr. Damon. "I should say so! I'll go tell the cook to get us all a good

mealwe need it," for a competent cook had been installed in the old farmhouse where Tom and his party

"But you did the trick, Tom, old man!" exclaimed Ned, fervently, as he looked down the valley and saw the

receding water. For, with the opening of the channel into the other valley the flood, at no time particularly

"Oh, I don't know," spoke Tom, modestly. "It just happened so. There was one minute, though, after I got to

the place in Preston where I had stored the powder, that I didn't know whether I would succeed or not."

"Why, in my hurry and excitement I forgot the key to the underground storeroom where I had put the

explosive. I knew there was no time to get another, so I took a chance and burst in the door with an axe I

"I should say you did take a chance!" declared Ned, who knew how "freaky" the high explosive was, and how

"But it came out all right," went on Tom. "I bundled it into the other seat of my Humming Bird, and started

"Nearly all," replied Tom. "The last of them were hurrying away as I left. And it shows how scared they

were, they didn't pay any attention to me and my flying machine, though I'll wager some of them never saw

"Well, they don't need to be scared any more," put in Mr. Damon "You saved their homes for them, Tom."

"I'd like to get hold of the fellow who doped my powder; that's what I'd like to do," murmured the young

inventor. "Ned, we'll have to be doubly watchful from now on. But I must take a look at my gun. That last

But the giant cannon was as perfect as the day it was turned out of the shop. Not even the extra charge of the

"That's fine!" cried Tom, as he looked at every part. "As soon as this flood is over we'll try some more

The great gun was covered with tarpaulins to protect it from the weather, and then all retired to the house for

a bountiful meal. Late that afternoon nearly all signs of the flood had disappeared, save that along the edges

of the creek was much driftwood, showing the height to which the creek had risen. But it would have gone

The water from the impounded lake continued to pour down into the cross valley, and did some damage, but

nothing like what would have followed its advent into Preston. The few inhabitants of the gulch into which

the young inventor had directed the flood had had warning, and had fled in time. In Preston, some few houses

The following day some of the officers of the water company paid a visit to Tom, to thank him for what he

had done. But for him they would have been responsible for great property damage, and loss of life might

They intended to rebuild the dam, they said, on a new principle, making it much stronger.

"And," said the president, "we will have an emergency outlet gate into that valley you so providentially

opened for us, Mr. Swift. Then, in time of great rain, we can let the water out slowly as we need to."

Tom's chief anxiety, now, was to bring his perfected gun to the notice of the United States Government

officials. To have them accept it, he knew he must give it a test before the ordnance board, and before the

He ordered several new projectiles, some of a different type from those heretofore used, and leaving Koku

and Ned in charge of the gun, went back to Shopton to superintend the manufacture of an additional supply of

Then, with a plentiful supply of ammunition and projectiles, Tom resumed his practice in the lonely valley.

He had, in the meanwhile, sent requests to the proper government officials to come and witness the tests.

At first he met with no success, and he learned, incidentally, that General Waller had built a new gun, the

But, in a way, fortune favored our hero. For when General Waller tested his new gun, though it did not burst,

it did not come up to expectations, and its range was not as great as some of the weapons already in use.

Then, too, Captain Badger acted as Tom's friend at court. He "pulled wires" to good advantage, and at last the

government sent word that one of the ordnance officers would be present on a certain day to witness the tests.

"I wish the whole board had come," said Tom. "Probably they have only sent a young fellow, just out of West

"But I'm going to give him the surprise of his life; and if he doesn't report favorably, and insist on the whole

Tom made his preparations carefully, and certainly Captain Waydell, the young officer who came to

represent Uncle Sam, was impressed. Tom sent shell after shell, heavily charged, against the side of the

mountain. Great holes and gashes were torn in the earth. The gun even exceeded the range of thirty miles.

And the heaviest armor plate that could be procured was to the projectiles of the giant cannon like cheese to a

"It's great, Mr. Swift! Great!" declared the young captain. "I shall strongly recommend that the entire board

see this test." And when Tom let him fire the gun himself the young man was more than delighted.

He was as good as his word, and a week later the entire ordnance board, from the youngest member to the

grave and grizzled veterans, were present to witness the test of Tom's giant cannon.

It is needless to say that it was successful. Tom and Ned, not to mention Mr. Damon, Koku and every loyal

member of the steel working gang, saw to it that there was no hitch. The solid shots were regarded with

wonder, and when the explosive one was sent against the hillside, making a geyser of earth, the enthusiasm

"We shall certainly recommend your gun, Mr. Swift," declared the Chief of Staff. "It does just what we want

it to do, and we have no doubt that Congress will appropriate the money for several with which to fortify the

"The gun is most wonderful," spoke a voice with a German accent. "It is surprising!"

Tom and Ned both started. They saw an officer, evidently a foreigner, resplendent in gold trimmings, and

"Yes, General von Brunderger," agreed the chief, "it is a most timely invention. Mr. Swift, allow me to

present you to General von Brunderger, of the German army, who is here learning how Uncle Sam does

Tom bowed and shook hands. He glanced sharply at the German, but was sure he had never seen him before.

Then all the board, and General von Brunderger, who, it appeared, was present as an invited guest, examined

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

The young inventor did not have long to wait. In about two weeks, during which time he and Ned perfected

several little matters about the cannon, there came an officiallooking document.

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

"The government accepts my gun!" exclaimed the young inventor. "It will purchase a number as soon as they

can be made. We are to take one to Panama, where it will be set up. Hurray, Ned, my boy! Now for Panama!"

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

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

"Indeed, and you did more than that. If it hadn't been for you, Mr. Damon and Koku we'd never have gotten

off as soon as we did. The government is the limit for doing things, sometimes."

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

This conversation took place on board one of Uncle Sam's warships, which the President had designated to

The big gun had been lashed to the deck of the vessel, and was well protected from the weather. In the hold

the parts of the disappearing carriage, which Tom had at last succeeded in having made, were securely

stowed. In another part of the warship were the big projectiles, some arranged to be fired as solid shots, and

others with a bursting charge. There was also a good supply of the powerful explosive, and Tom had taken

extraordinary precautions so that it could not be tampered with. Koku had been detailed as a sort of guard

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

"But I don't believe there is any danger," went on the young inventor. "I spoke about what had happened, and

the ordnance board took extra precautions to see that none but men and officers who could be implicitly

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

"I don't know what to say. Certainly I can't see why anyone connected with Uncle Sam would want to throw

cold water on a plan to fortify the canal, even if an outsider has invented the gunI mean someone like

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

It must not be supposed that to get the big gun aboard the vessel, arrange for a new supply of the explosive,

and for many of the great projectiles, had been easy work. It was a task that taxed the skill and strength of

There had been wearying delays, especially in the matter of making the disappearing carriage. At times it

seemed as if the required projectiles would never be finished. The powder, too, gave trouble, for sometimes

But Tom never gave up, even when it seemed that some of the failures were purposely made. Ned declared

that there was a conspiracy against his chum, but Tom could not see it that way. It was due to a combination

But finally the gun had been put aboard the ship, having been transported from the proving ground in the

valley, and they were now en route to Panama. There the giant cannon was to be set up, and tried again. If it

came up to expectations it was to be finally adopted as the official gun for the protection of the big canal, and

"And I'm confident that it will make good," said the young inventor to his chum, as they paced the deck of the

vessel. "In fact, I'm so sure I have practically engaged the Universal Steel Company to hold itself in readiness

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

"It certainly is a giant cannon," remarked Ned, as he paused to look at the prostrate monster, lashed to the

deck, with its wrappings of tarpaulins. "It looks bigger here than it did when you fired the shot that saved the

"Yes, I suppose it does, by contrast. But let's go down and see how the powder and shells are standing the

trip. I told the captain to have them securely lashed, so if we struck rough weather, and the vessel rolled, they

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

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

The two chums found that every precaution had been taken in regard to the projectiles and powder. Koku was

on guard, the giant regarding the boxes of explosive with a calm but determined eye. It would not be well for

"Am dere anyt'ing I kin do fo' yo'all, Massa Tom?" inquired Eradicate, as the young inventor and Ned

prepared to go on deck again. The aged colored man had insisted on coming as a sort of personal bodyguard

to Tom, and the latter had not the heart to refuse him. Eradicate was desperately jealous of the giant.

"Huh!" Eradicate had said, "anybody kin sit an' look at a lot ob dem powder boxes; but 'tain't everybody what

It was planned to proceed directly to Colon, the eastern terminus of the canal, from New York, stopping at

Santiago to transact some government business there. The big gun was to be mounted on a barbette near the

Gatun locks, pointing out to sea, and the trial shots would be fired over the water.

Eventually the gun would be so mounted as to swing in a circle,, so as to command the land as well as the

water; and, in fact, if the government decided to adopt Tom's giant cannon as the official protective arm of

the canal, they would all be so mounted. For, of course, it might be possible for land as well as sea forces to

The first few days of the voyage were pleasant enough. The weather was fine, and Tom was kept busy

explaining to many of the officers aboard the ship the principles of his gun, powder and projectiles. Members

of the ordnance board, who had been detailed to witness the test, were also much interested as Tom modestly

At Santiago de Cuba, when Tom and Ned were standing near the gangway, watching the officers returning

from shore leave, for the ship was to proceed soon, after a two days' stay, the young inventor started as he

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

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

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

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

"Ah, my good friend, Tom Swift!" exclaimed General von Brunderger, genially, as he grasped the hands of

Tom and Ned. "I am glad to see you both again." He seemed to mean it, though he had not been especially

cordial to them at the first gun test. "Take my grip below," he said in German to the man, "and, Rudolph, find

Lieutenant Blake and inform him that I am on board. I have been invited to go to Panama by Lieutenant

Blake," he added to Tom. "I have never seen the big ditch that you wonderful Americans have so nearly

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

"Ah, so you were successful, then?" and his voice expressed surprise. "I had not heard. And the big gun; is he

here?" Though speaking very good English, von Brunderger occasionally lapsed into the idioms of his

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

Ned declared afterward that the German started as Tom asked this question, but if he did the young inventor

"I go but to see the big ditch before the water is let in," he replied. "And since your gun is to have a test I

shall be glad to witness that. You see, I am commissioned by my Kaiser to learn all that you Americans will

allow me to in reference to your ways of doing thingsin the army, the navy and in the pursuit of peace.

After all, preparation for war is the best means of securing peace. Your officers have been more than kind and

I have taken advantage of the offer to go to Panama. Lieutenant Blake said the ship would stop here, and, as I

"I don't see anything to be worried about," declared Tom. "It's true that a German once tried to make trouble

for me, but this von Brunderger is all right, as far as I can learn. He has the highest references, and is an

accredited representative of the Kaiser. You are too suspicious, Ned, just as you were in the case of General

From Santiago, swinging around the island of Jamaica, the warship took her way, with the big gun, to Colon.

The storm broke without any unusual preliminaries, but quickly increased to a hurricane, and when night fell

it saw the big ship rolling and tossing in a tempestuous sea. Torn was anxious about his big gun, but the

Tom and Ned had seen little of the German officer that day, nor, in fact, since he came aboard. He kept much

in the quarters of the other officers, and the report was current that he was a "jolly good fellow."

Rather anxious as to the outcome of the storm, Tom turned in late that night, not expecting to sleep much, for

there were many unusual noises. But he did drop off into a doze, only to be awakened about an hour later by

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

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

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

It was the officer of the deck giving orders to a number of marines and sailors as Tom hastily clad, leaped on

deck, followed by his chum. The warship was pitching and tossing worse than ever in the heaving billows,

and the men were engaged in making fast the giant cannon, which, as Tom had surmised, had torn loose from

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

The breech of the gun appeared to be the end that had come loose, while the muzzle still held fast. And this

immense mass of steel was swinging about, eluding the efforts of the ship's officers and crew to capture it.

And it seemed only a question of time when the muzzle would tear loose, too. Then, free on deck, the giant

cannon would roll through the frail bulwarks, and plunge. into the depths of the sea.

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

"That's what we're trying to do," answered the other. "We did get the bight of a cable over the breech, but the

men could not hold it, even though they took a couple of turns around the bitts."

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

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

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

Koku stared uncomprehendingly for a moment, while the loosened gun continued to thump and pound on the

deck as though it would burst through. Then it filtered through the dull brain of honest Koku what was

"I go," he said, and he hurried up the companionway, while Ned, eager to be with Tom, took up the less

Once more, with the giant strength of Koku to aid in the work, the task of lashing the gun again to the deck

was undertaken. A bight of steel cable was gotten around the breech, and then passed to a big bitt, or

stanchion, bolted to the deck. Koku, working on the heaving deck, amid the hurricane, took a turn around the

There came a roll of the ship that threatened to send the gun sliding against the stanchion, but Koku braced

himself. His arms, great bunches of muscles, strained and fairly cracked with the strain. The wire rope

seemed to give. Then, as the ship rolled the other way, the strain eased. Koku, aided by the cable, and by the

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

For a moment the ship was on a level keel, and taking advantage of this, when the weight of the gun would be

neutral, another cable was passed around it. Then it was a comparatively easy matter to put on more lashings

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

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

"I thought it would surely go overboard," went on Tom. "Only for Koku it would have. Those fellows

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

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

But they did manage to get some rest by morning, at which time the hurricane seemed to have blown itself

out. The day saw the sea gradually calm down, and the big cannon was made additionally secure against a

possible recurrence of the accident. But a few days more and it would be safe at Colon.

Tom and Ned had gone on deck soon after breakfast to look at the cannon. All about were pieces of the

broken cables, that had been cast aside when the new lashings were put on. Ned picked up one end,

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

"I mean that they were partly filed, or cut throughthen the storm and the pressure of the gun did the rest.

He held out the piece of wire rope. There, on the end, could be seen several strands cleanly severed, as

"By Jove!" murmured Tom. He looked about the deck. There was no one near the big gun. "Ned," whispered

his chum, "there's something wrong here. It's more of that conspiracy to defeat my aims. Don't say anything

"The scoundrels!" exclaimed Ned. "I wish we knew who they were. General Waller isn't aboard, and what

other of the officers has a gun of his own that he would rather see accepted by the government than yours?"

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

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

"Oh, Ned means that some of the cables look as though they had been cut," hastily put in Tom, nudging his

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

"Or else filed," went on Tom easily, with a warning glance at Ned. "But I dare say they were old cables, that

had been used on other work, and may have become frayed. Everything is safe now, though. New cables

"I am glad to hear it. It would be aerah, a national calamity to lose so valuable a gun, and the opening of

the canal so near at hand. I am glad that your invention is safe, Herr Swift," and he smiled genially at Tom

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

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

But no further accidents occurred. There were no more storms, no attempt was made to meddle with Tom's

powder, and in due season the ship arrived at Colon, and after much labor the great gun, its carriage, the

shells and the powder were taken to the barbette at the Gatun locks, designed to admit vessels from the

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

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

"Oh, yes, I think so. Besides, I've added a few more inches to the lift of the disappearing carriage, and it will

"Just get hold of that small derrick, Koku, and lift up one of the projectiles. I want to see if they come in the

The giant was soon engaged in winding up the rope of an improvised hoist that stood about in the position the

permanent one was to go. From the interior of the barbette, which was, in effect, a bombproof structure,

there was lifted one of the big projectiles destined to be hurled from Tom Swift's giant cannon.

"Yes, I think that will do," decided the young inventor, as he watched Koku. "Now, Mr. Damon, if you will

kindly oversee this part of the work, I'll see if we can't get that motor in better shape. It didn't work worth a

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

"Heah am dem chicken sandwiches, an' some hot coffee fo' yo' all. I done knowed yo' alt wouldn't hab no

"That's mighty good of you, Rad," spoke Tom, with a laugh. "I was getting pretty hungry; but I didn't want to

stop until I had things moving in better shape. Come on, Ned, let's knock off for a few minutes and take a

As they sat about the place where the gun was being mounted, munching sandwiches and drinking the coffee

which the aged colored man had so thoughtfully provided, Eradicate said, with a chuckle:

"By gar! Dey can't git erlong wifout dish yeah coon, arter all! Ha! ha! Dat cocoanut giant he mighty good

when it comes t' fastening big guns down so dey won't blow away, but when it comes t' eatin' dey has t'

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

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

They had landed from the warship several days before, and from then on there had been hard work and plenty

of it. Tom was here, there and everywhere, directing matters so that his gun would be favorably placed.

Some preliminary work had been done before they arrived in the way of preparing a place to mount the gun,

and this work was now proceeding. The officers of the ordnance department were in actual charge, but they

"It will be some days before you can actually fire your gun; will it not?" asked Ned of his chum, as they

"Yesa week at least, I expect. It is taking longer to set up the carriage than I thought. But it will be an

improvement over the solid one we formerly used. That was fine, Rad," he concluded as the colored man

went back to the shack of which he had taken possession for himself and his cooking operations. It adjoined

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

Tom, though he had many suspicions about the cut cables that had nearly been the cause of his gun sliding

The German officer, with his body servant, who seldom spoke, had landed at Colon, and was proceeding to

make himself at home with the officers and men who were building the canal. Occasionally he paid a visit to

Tom and Ned, where they were engaged about the big gun. He always seemed pleasant, and interested in

their labors, asking many question, but that was all, and our hero began to feel that perhaps he was wrong in

As for Ned, he veered uncertainly from one suspicion to another. At one time he declared that von

Brunderger and General Waller were in a conspiracy to upset Tom's plans. Again he would accuse the

German alone, until Tom laughingly bade him attend more to work and less to theories.

Slowly the work progressed. The gun was mounted after much labor, and then arrangements began to be

made for the test. A series of shots were to be fired out to sea, and the proper precautions were to be taken to

"Though if you intend to send a projectile thirty miles," said one of the officers, "I'm afraid there may be

some danger, after all. Are you sure you have a range of thirty miles, Mr. Swift?"

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

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

A few days before the date set for the test one of the sentinels, who had been detailed to keep

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

"Yes, let him come up," directed the young inventor. "Do you hear that, Ned?" he called. "Our

"I hope he has, for dad's sake," went on Tom. "Hello, Mr. Peterson!" he called, as he noticed the old

"I heard you were down here," said the many not answering the question directly, "and as I had to run over

from my island for some supplies I thought I'd stop and see you. How are you?" and he shook hands.

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

"Well, Mr. Peterson," remarked Tom, after a pause, "I'm sure I hope you will succeed in your quest. You

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

"Off in that direction," responded the fortunehunter, pointing to the northeast. "It's a little farther from here

than I thought it was at firstabout thirty miles. But I have a little second hand steam launch that my

pardners and I use. I'll come for you, take you over and bring you back any time you say."

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

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

"Well, goodbye, and good luck to you," called Tom, as the fortunehunter started away.

"I don't believe so," he answered. "Alec has always been that wayalways visionaryalways just about to

"Yes, I suppose so; but, in a way, dad can stand it. And if I make good on this gun test, ten thousand dollars

won't look very big to me. I guess dad gave it to Alec from a sort of sentimental feeling, anyhow."

"That's it, Ned. It was a sort of reward, in a way, and I guess dad won't be brokenhearted if Alec doesn't

succeed. Only, of course, he'll feel badly for Alec himself. Poor old man! he won't be able to do much more

prospecting. Well, Ned, let's get to work on that ammunition hoist. It still jams a little on the ways, and I want

it to work smoothly. There's no use having a hitcheven a small onewhen the big bugs assemble to see

The two youths labored for some time, being helped, of course, by the workmen provided by the government,

There were many little details to look after, not the least of which was the patrolling of the stretch of ocean

over which the great projectiles would soar in reaching the faroff targets at which Tom had planned to

shoot. No ships were to be allowed to cross the thirtymile mark while the firing was in progress. So, also,

But at last all seemed in readiness. The gun had been tried again and again on its carriage. The projectiles

were all in readiness, and the terribly powerful ammunition had been stored below the gun in a bombproof

Because the gun had been fired so many times with a charge of powder heavier than was ordinarily called for,

and had stood the strain well, Tom had no fear of standing reasonably close to it to press the button of the

The German officer was occasionally seen about the place where the gun was mounted, but he appeared to

take only an ordinary interest in it. Tom began to feel more than ever that perhaps his suspicions were

Some officials high in government affairs had arrived at Colon in anticipation of the test, which, to Tom's

delight, had attracted more attention than he anticipated. At the same time he was a bit nervous.

Plans had been made for a ship to be stationed near the zone of fire, to report by wireless the character of

each shot, the distance it traveled, and how near it came to the target. The messages would be received at a

station near the barbette, and at once reported to Tom, so that he would know how the test was progressing.

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

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

The gun was found all right, in its great tarpaulin cover, and Tom had the latter taken off that he might go

over every bit of mechanism. He made a few slight changes, and then got ready for the final trials.

On an improvised platform, not too near the giant cannon, had gathered the ordnance board, the specially

invited guests, a number of officers and workers in the canal zone, and one or two representatives of foreign

governments. Von Brunderger was there, but his "familiar," as Ned had come to call the stolid German

Tom took some little time to explain, modestly enough, the working of his gun. A number of questions were

asked, and then it was announced that the first shot, with only a practice charge of powder, would be fired.

"Careful with that projectile now. That's it, slip it in carefully. A little farther forward. That's better. Now the

powderKoku, are you down there?" and Tom called down the tube into the ammunition chamber.

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

"Now, gentlemen," said Tom, "this is not a shot for distance. It is merely to try the gun and get it warmed up,

Many were astonished by the great report, but Tom and the others, who were used to the service charges,

hardly noticed this one. Yet when the wireless report came in, giving the range as over fourteen thousand

"Over eight miles!" declared one grizzled officer; "and that with only a practice charge. What will happen

Tom soon showed them. Quickly he called for another projectile, and it was inserted in the gun. Then the

powder began to come up the hoist. Meanwhile the young inventor had assured himself that the gun was all

This time, when Tom pressed the button there was such a tremendous concussion that several, who were not

prepared for it, were knocked back against their neighbors or sent toppling off their chairs or benches. And as

for the report, it was so deafening that for a long time after it many could not hear well.

But Tom, and those who knew the awful power of the big cannon, wore specially prepared eardrum

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

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

Again came that terrific report, that trembling of the ground, that concussion, that blast of air as it rushed in to

"I think you must have gone the limit this time, Tom!" yelled Ned, as he turned on the compressed air to blow

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

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

"I think I can do better than that," declared Tom, after looking at the various recording gauges, and noting the

elevation of the gun. "I think I can get a little flatter trajectory, and that will give a greater distance. I'm going

"Yes, and the heaviest shell we havethe one with the bursting charge. I'll fire that, and see what happens.

Tell the zoneship to be on the lookout," he said to the wireless operator, giving a brief statement of what he

"Well, not so much. I'm sure my cannon will stand it. Come on now, help me depress the muzzle just a trifle,"

and by means of the electric current the big gun was raised at the breech a few inches.

As is well known, cannon shots do not go in straight lines. They leave the muzzle, curve upward and come

down on another curve. It is this curve described by the projectile that is called the trajectory. The upward

curve, as you all know, is caused by the force of the powder, and the downward by the force of gravitation

acting on the shot as soon as it reaches its zenith. Were it not for this force the projectiles could be fired in

straight lines. But, as it is, the cannon has to be elevated to send the shot up a bit, or it would fall short of its

Consequently, the flatter the trajectory the farther it will go. Tom's object, then, was to flatten the trajectory,

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

The young inventor was not a little nervous as he prepared to press the button this time. It was a heavier

charge than any used that day, though the same quantity had been fired on other occasions with safety. But he

Coincident with the pressure of Tom's fingers there seemed to be a veritable earthquake. The ground swayed

and rocked, and a number of the spectators staggered back. It was like the blast of a hundred thunderbolts.

The gun shook as it recoiled from the shock, but the wonderful disappearing carriage, fitted with coiled,

Following the awful report, the terrific recoil and the howl of the wind as it rushed into the vacuum created,

there was an intense silence. The projectile had been seen by some as a dark speck, rushing through the air

like a meteor. Then the wireless operator could be seen writing down a message, the telephonelike receivers

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

As he ceased speaking there came from underneath the great gun the sound of confused shouts. Tom and Ned

"What is it, Koku?" yelled Tom, springing to the speaking tube connecting with the powder magazine, at the

same time keeping an eye on the wireless operator. Tom was torn between two anxieties.

"Someone here, Master!" cried the giant. "Him try to fix powder. Ah, I fix you!" and with a savage snarl the

giant, in the concrete chamber below, could be heard to attack someone who cried out gutturally in German:

"Come on, Ned!" cried Tom, making a dash for the stairs that led into the magazine. There was confusion all

about, but through it all the wireless operator continued to write down the message coming to him through

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

As he reached it, a door leading to the outer air flew open, and out rushed a man, badly torn as to his clothes,

and scratched and bleeding as to his face. On he ran, across the space back of the barbette, toward the lower

"Him sneak in herehave some of that stuff you call 'dope.' I sent up powder, and I come back here to see

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

They raced outside to behold a curious sight. Straight toward von Brunderger rushed the man as if in a frenzy

of fear. He called out something in German to his master, and the latter's face went first red, then white. He

was observed to look about quickly, as though in alarm, and then, with a shout at his servant, the German

officer rushed from the stand, and the two disappeared in the direction of the barracks.

"Give it up," answered Tom, "except that Koku spoiled their trick, whatever it was. It looks as if this was the

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

"The longest shot on record!" cried the man. "Thirtythree miles, and it struck, exploded, and blew the top

There was a silence after the inspiring words of the operator, and then it seemed that everyone began to talk

at once. The recordbreaking shot, the effect of it and the struggle that had taken place in the powder room,

together with the flight of von Brunderger and his servant, gave many subjects for excited conversation.

"I've got to get at the bottom of this!" cried Tom, making his way through the press of officials to where the

wireless operator stood. "Just repeat that," requested Tom, and they all gave place for him, waiting for the

"Thirtythree miles!" murmured Tom. "That is better than I dared to hope. But what's that about blowing the

"That's what you did, with that explosive shell, Mr. Swift. The operator on the firingzone ship saw the top

fly off when the shell struck. The ship was about half a mile away, and when they heard that shell coming the

officers thought it was all up with them. But, instead, it passed over them and demolished the top of the

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

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

"I don't understand it myself," replied the young inventor. "It appeared that someone went into the

But Herr von Brunderger was not to be found, nor was his man in evidence. They had fled, and when a search

was made of their rooms, damaging evidence was found. Before a board of investigating officers Koku told

his story, after the gun tests had been declared off for the day, they having been most satisfactory.

The German officer's servant, it appeared, had managed to gain entrance to the ammunition chamber by

means of a false key to the outer door. There were two entrances, the other being from the top of the platform

where the cannon rested. Koku had seen him about to throw something into one of the ammunition cases, and

had grappled with him. There was a fight, and, in spite of the giant's strength, the man had slipped away,

An investigation of some of the powder showed that it had been covered with a chemical that would have

made it explode prematurely when placed in the gun. It would probably have wrecked the cannon by blowing

out the breech block, and might have done serious damage to life as well as property.

They found the answer among his papers. He had been a German officer of high rank, but had been dismissed

from the secret service of his country for bad conduct. Then, it appeared, he thought of the plan of doing

some damage to a foreign country in order to get back in the good graces of his Fatherland.

He forged documents of introduction and authority, and was received with courtesy by the United States

officials. In some way he heard of Tom's gun, and that it was likely to be so successful that it would be

adopted by the United States government. This he wanted to prevent, and he went to great lengths to

accomplish this. It was he, or an agent of his, who forged the letter of invitation to General Waller, and who

Later he tried other means, sending a midnight visitor to Tom's house and even going to the length of filing

the cables in the storm, so the gun would roll off the warship into the sea. All this was found set down in his

papers, for he kept a record of what he had done in order to prove his case to his own government. It was his

That he would be restored to favor had he succeeded, was an open question, though with Germany's

friendliness toward the United States it is probable that his acts would have been repudiated. But he was

Failing in many attempts he resolved on a last one. He sent his servant to the ammunition room to "dope" the

powder, hoping that, at the next shot, the gun would be mined. Perhaps he hoped to disable Tom. But the plot

failed, and the conspirators escaped. They were never heard of again, probably leaving Panama under

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

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

"Bless my pillow sham!" cried Mr. Damon. "I think I can get a good night's sleep now. So they have formally

"Yes. The last tests I gave them, showing how easily it could be manipulated, convinced them. It will be one

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

"Before we go," suggested Ned, "let's go take a look at that island from which Tom blew the top. It must be

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

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

"That was my island!" exclaimed Mr. Peterson. "The mine was in that mountain, but an earthquake had

covered it. I should never have found it but for you. That shot you accidentally fired ripped the mountain

apart. My men and I were fortunately at the base of it then, but we sure thought our time had come when that

shell struck. It went right over our heads. But it did the business, all right, and opened up the old mine. Tom,

your father won't lose his money, we'll all be rich. Oh, that was a lucky shot! I knew it was your cannon that

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

"You must come and see the mineyour mine, Tom, for it never would have been rediscovered had it not

It did not take Tom long to do this. His type of cannon was formally accepted as a defense for the Panama

Canal, and he received a fine contract to allow that type to be used by the government. His powder and

Then, one day, he and Ned, with Koku and Mr. Damon, visited the scene of the great shot. As Mr. Peterson

had said, the whole top of the mountain had been blown off by the explosive shell, opening up the old mine.

While it was not quite as rich as Mr. Peterson had glowingly painted, still there was a fortune in it, and Mr.

"And now for the good old U. S. A.!" cried Tom, as they got ready to go back home. "I'm going to take a long

rest, and the only thing I'm going to invent for the next six months is a new potato slicer." But whether Tom

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

"I'll take care ob himI'll take care ob Massa Tom," put in Eradicate, as he cast a quick look at Koku.

"Giants am all right fo' cannon wuk, but when it comes t' comforts Massa Tom gwine t' 'pend on ole

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

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

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

"Yes, it went farther than I thought it would," replied Tom. And now, as they are taking a closing meal at

Panama, ready to return to the United States, we will take leave of Tom Swift and his friends.