"Bless my buttons!" cried Mr. Damon.
"Let's chase after him!" yelled Ned.
"Koku kin run de fastest oh any oh us," put in Eradicate. "Let him go."
"Hold on—wait a minute!" exclaimed Tom. "We want to know who that man is—and why we're going to chase after him. Koku, I guess it's up to you. Something has been going on here that I don't know anything about. Explain!"
"Well, it's no use to chase after him now," said Ned. "There he goes on his motor-cycle."
As he spoke the man, who, even from a rear view, presented all the characteristics of an army man, so straight was his carriage, leaped upon a motor-cycle that he pulled from the roadside bushes, and soon disappeared in a cloud of dust.
"No, he's gone," spoke Tom, half-regretfully. "But who was he, Koku? You seemed to know him. What was he doing out here, watching my test?"
"Me tell," said the giant, simply. "Little while after Master come back from where him say big gun all go smash, man come to shop when Master out one day. Him very nice man, and him say him know you, and want to help you make big cannon. I say, 'Master no be at home.' Man say him want to give master a little present of powder for use in new cannon. Master be much pleased, man say. Make powder better. I take, and I want Master to be pleased. I put stuff what man gave me in new powder. Man go away—he laugh—he say he be here today see what happen—I tell him you go to make test today. Man say Master be much surprised. That all I know."
Silence followed Koku's statement. To Ned and Mr. Damon it was not exactly clear, but Tom better understood his giant servant's queer talk.
"Is that what you mean, Koku?" asked the young inventor, after a pause. "Did some stranger come here one day when I was out, after I had made my new powder, and did he give you some 'dope' to put in it?"
"What you mean by 'dope'?"
"I mean any sort of stuff."
"Yes, man give me something like sugar, and I sprinkle it on new powder for to surprise Master."
"Well, you've done it, all right," said Tom, grimly. "Have you any of the stuff left?"
"I put all in iron box where Master keep new powder."
"Well, then some of it must be there yet. Probably it sifted through the excelsior-like grains of my new explosive, and we'll find it on the bottom of the powder-case. But enough stuck to the strands to spoil my test. I'll just take a reading of the gauges, and then we'll make an investigation."
Tom, with Ned to help him, made notes of how far the weight had risen in the tube, and took data of other points in the experiment.
"Pshaw!" exclaimed Tom. "There wasn't much more force to my new powder, doped as it apparently has been, than to the stuff I can buy in the open market. But I'm glad I know what the trouble is, for I can remedy it. Come on back to the shop. Koku, don't you ever do anything like this again," and Tom spoke severely.
"No, Master," answered the giant, humbly.
"Did you ever see this man before, Koku?"
"No, Master."
"What kind of a fellow was he?" asked Ned.
"Oh, him got whiskers on him face, and stand very straight, like stick bending backwards. Him look like a soldier, and him blink one eye more than the other."
Tom and Ned started and looked at one another.
"That description fits General Waller," said Ned, in a low voice to his chum.
"Yes, in a way; but it would be out of the question for the General to do such a thing. Besides, the man who ran away, and escaped on his motor-cycle, was larger than General Waller."
"It was hard to tell just what size he was at the distance," spoke Ned. "It doesn't seem as though he would try to spoil your experiments, though."
"Maybe he hoped to spoil my cannon," remarked Tom, with a laugh that had no mirth in it. "My cannon that isn't cast yet. He probably misunderstood Koku's story of the test, and had no idea it was only a miniature, experimental, gun.
"This will have to be looked into. I can't have strangers prowling about here, now that I am going to get to work on a new invention. Koku, I expect you, after this, not to let strangers approach unless I give the word. Eradicate, the same thing applies to you. You didn't see anything of this mysterious man; did you?"
"No, Massa 'Tom. De only s'picious man I see was mab own cousin sneakin' around mah chicken coop de odder night. I tooks mah ole shot gun, an' sa'ntered out dat way. Den in a little while dere wasn't no s'picious man any mo'."
"You didn't shoot him; did you, Rad?" cried Tom, quickly.
"No, Massa Tom—dat is, I didn't shoot on puppose laik. De gun jest natchelly went off by itself accidental-laik, an' it peppered him good an' proper."
"Why, Rad!" cried Ned. "You didn't tell us about this."
"Well, I were 'shamed ob mah cousin, so I was. Anyhow, I only had salt an' pepper in de gun—'stid ob shot. I 'spect mah cousin am pretty well seasoned now. But dat's de only s'picious folks I see, 'ceptin' maybe a peddler what wanted t' gib me a dish pan fo' a pair ob ole shoes; only I didn't hab any."
"There are altogether too many strangers coming about here," went on Tom. "It must be stopped, if I have to string charged electric wires about the shops as I once did."
They hurried back to the shop where the new powder was kept, and Tom at once investigated it. Taking the steel box from where it was stored he carefully removed the several handfuls of excelsior-like explosive. On the bottom of the box, and with some of it clinging to some of the powder threads, was a sort of white powder. It had a peculiar odor.
"Ha!" cried Tom, as soon as he saw it. "I know what that is. It's a new form of gun-cotton, very powerful. Whoever gave it to Koku to put on my powder hoped to blow to atoms any cannon in which it might be used. There's enough here to do a lot of damage."
"How is it that it didn't blow your test cylinder to bits?" asked Ned.
"For the reason that the stuff I use in my powder and this new gun-cotton neutralized one another," the young inventor explained. "One weakened the other, instead of making a stronger combination. A chemical change took place, and lucky for us it did. It was just like a man taking an over-dose of poison—it defeated itself. That's why my experiment was a failure. Now to put this stuff where it can do no harm. Is this what that man gave you, Koku?"
"That's it, Master."
There came a tap on the door of the private room, and instinctively everyone started. Then came the voice of Eradicate, saying:
"Dere's a army gen'men out here to see you. Massa Tom; but I ain't gwine t' let him in lessen as how you says so."
"An army gentleman!" repeated Tom.
"Yais, sah! He say he General Waller, an' he come on a motor-cycle."
"General Waller!" exclaimed Tom. "What can he want out here?"
"And on a motor-cycle, too!" added Ned. "Tom, what's going on, anyhow?"
The young inventor shook his head.
"I don't know," he replied; "but I suppose I had better see him. Here, Koku, put this powder away, and then go outside. Mr. Damon, you'll stay; won't you?"
"If you need me, Tom. Bless my finger nails! But there seems to be something wrong here."
"Show him in, Rad!" called Tom.
"Massa Gen'l Herodotus Waller!" exclaimed the colored man in pompous tones, as he opened the door for the officer, clad in khaki, whom Tom had last seen at Sandy Hook.
"Ah, how do you do, Mr. Swift!" exclaimed General Waller, extending his hand. "I got your letter inviting me to a test of your new explosive. I hope I am not too late."
Tom stared at him in amazement.
"You—you got my letter!" stammered Tom, holding out his hand for a missive which the General extended. "I—I don't exactly understand. My letter?"
"Yes, certainly," went on the officer. "It was very kind of you to remember me after—well, to be perfectly frank with you, I did resent, a little, your remarks about my unfortunate gun. But I see you are of a forgiving spirit."
"But I didn't write you any letter!" exclaimed Tom, feeling more and more puzzled.
"You did not? What is this?" and the General unfolded a paper. Tom glanced over it. Plainly it was a request for the General to be present at the test on that day, and it was signed with Tom Swift's name.
But as soon as the young inventor saw it, he knew that it was a forgery.
"I never sent that letter!" he exclaimed. "Look, it is not at all like my handwriting," and he took up some papers from a near-by table and quickly compared some of his writing with that in the letter. The difference was obvious.
"Then who did send it?" asked General Waller. "If someone has been playing a joke on me it will not be well for him!" and he drew himself up pompously.
"If a joke has been played—and it certainly seems so," spoke Tom, "I had no hand in it. And did you come all the way from Sandy Hook because of this letter?"
"No, I am visiting friends in Waterford," said the officer, naming the town where Mr. Damon lived. "My cousin is Mr. Pierce Watkins."
"Bless my doorbell!" exclaimed Mr. Damon, "I know him! He lives just around the corner from me. Bless my very thumb prints!"
General Waller stared at Mr. Damon in some amazement, and resumed:
"Owing to the unfortunate accident to my gun, and to some slight injuries I sustained, I found my health somewhat impaired. I obtained a furlough, and came to visit my cousin. The doctor recommended open air exercise, and so I brought with me my motor-cycle, as I am fond of that means of locomotion."
"I used to be," murmured Mr. Damon; "but I gave it up."
"After his machine climbed a tree," Tom explained, with a smile, remembering how he had originally met Mr. Damon, and bought the damaged machine from him, as told in the first volume of this series.
"So, when I got your letter," continued the General, "I naturally jumped on my machine and came over. Now I find that it is all a hoax."
"I am very sorry, I assure you," said Tom. "We did have a sort of test today; but it was a failure, owing to the fact that someone tampered with my powder. From what you tell me, I am inclined to the belief that the same person may have sent you that letter. Let me look at it again," he requested.
Carefully he scanned it.
"I should say that was written in a sort of German hand; would you not also?" he asked of Mr. Damon.
"I would, Tom."
"A German!" exclaimed General Waller.
At the mention of the word "German" Koku, the giant, who had entered the room, to be stared at in amazement by the officer, exclaimed:
"That he, Master! That he!"
"What do you mean?" inquired Tom.
"German man give me stuff for to put in your powder. I 'member now, he talk like Hans who make our garden here; and he say 'yah' just the same like. That man German sure."
"What does this mean?" inquired the officer.
Quickly Tom told of the visit of an unknown man who had prevailed on the simple-minded 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 motor-cycle, just as the experiment failed, was related.
"We have a German gardener," went on Tom, "and Koku now recalls that our mysterious visitor had the same sort of speech. This ought to give us a clue."
"Let me see," murmured General Waller. "In the first place your test fails—you learn, then, that your powder has been tampered with—you see a man riding away in haste after having, in all likelihood, spied on your work—your 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 has been forged, presumably by a German.
"Question: Can the same German be the agent in both cases?"
"Bless my arithmetic! how concisely you put it!" exclaimed Mr. Damon.
"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."
"Nor can I," spoke the officer.
"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 be no chance of a mistake."
"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 protect you."
"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 highly-charged protecting electric wires again. We were just talking about them when you came in. Would you like to look about here, General?"
"I would, indeed, Tom. Have you made your big gun yet?"
"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 my gun strong enough to stand it."
"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 gun soon, and—Tom Swift—I am going to try to beat you!"
"All right, General," answered Tom, genially. "May the best gun win!"
"Bless my powder box!" cried Mr. Damon. "That's the way to talk."
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 airships were a source of wonder to him.
"How do you do it, Tom?" he asked.
"Oh, by keeping at it," was the modest answer. "Then my good friends here—Ned and Mr. Damon—help me."
"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.
"I can't imagine who would want to injure you or me, Tom Swift," he said.
"Do you think they wanted to injure you, General?" asked Mr. Damon.
"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 blow-up he would have gone with it."
"Bless my gaiters, yes!" exclaimed Mr. Damon.
"Well, we'll see if we can ferret him out!" spoke the officer as he took his leave.
Tom, Ned and the others talked the matter over at some length.
"I wonder if we could trace that man who rode away on the motor-cycle?" 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 him—that is, several persons had seen him pass—but that was all. So they had to record one failure at least.
"I wonder if the General himself could have sent that letter?" mused Ned, as they returned home.
"What! To himself?" cried Tom, in amazement.
"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, faking up a letter and inviting himself to the blowout."
"But if he did that—which I don't believe—why would he come when there was danger, in case his trick worked, of the whole place being blown to kingdom come."
"Ah, but you notice he didn't arrive until after danger of an explosion had passed," commented Ned.
"Oh, pshaw!" cried Tom. "I don't take any stock in that theory."
"Well, maybe not," replied Ned. "But it's worth thinking about. I believe if General Waller could prevent you from inventing your big gun, he would."
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 plans for the big gun.
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 that opal mine scheme?"
"Yes, Dad. What about him? Has he found it?"
"No, he writes to say he reached the island safely, and has been working some time. He hasn't had any success yet in locating the mine; but he hopes to find it in a week or so."
"That's just like him," murmured Tom. "Well, Dad, if you lose the ten thousand dollars I guess I'll have to make it up to you, for it was on my account that you made the investment."
"Well, you're worth it, Tom," replied his father, with a smile.
"Look out with that box, Koku! Handle it as though it contained a dozen eggs of the extinct great auk, worth about a thousand dollars apiece.
"Eradicate! Don't you dare stumble while you're carrying that tube. If you do, you'll never do it again!"
"By golly, Massa Tom! I—I's gwine t' walk on mah tiptoes all de way!"
Thus Eradicate answered the young inventor, while the giant, Koku, who was carrying a heavy case, nodded his head to show that he understood the danger of his task.
"So you think you've got the right stuff this time, Tom?" asked Ned Newton.
"I'm allowing myself to hope so, Ned."
"Bless my woodpile!" cried Mr. Damon. "I—I really think I'm getting nervous."
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 with—his 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 slow-burning powder, failing to explode, had set ablaze a shack in which he was working.
Only for the prompt action of Koku, Tom might have been seriously injured. As it was he lost some valuable patterns and papers.
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 foot-tons, 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 of his explosive, and using it in the big gun he intended to make.
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 made—a sort of miniature of the one Tom hoped to use in his giant cannon.
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 register the energy expended by the improvised cannon. There were charts to be filled in, and other details to be looked after.
"So General Waller won't be here?" remarked Ned, as they walked along, Tom keeping a watchful eye on Koku.
"No," was the reply. "He has gone back to Sandy Hook. He wrote that his health was better, and that he wanted to resume work on a new type of gun."
"I guess he's afraid you'll beat him out, Tom," laughed Ned. "You take my advice, and look out for General Waller."
"Nonsense! I say, Rad! Look out with those primers!"
"I'se lookin' out, Massa Tom. Golly, I don't laik dis yeah job at all! I—I guess I'd better be gittin' at dat whitewashin', Massa Tom. Dat back fence suah needs a coat mighty bad."
"Never you mind about the whitewashing, Rad. You just stick around here for a while. I may need you to sit on the cannon to hold it down."
"Sit on a cannon, Massa Tom! Say, looky heah now! You jest take dese primary things from dish yeah coon. I—I'se got t' go!"
"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!"
"I—I will, Massa Tom."
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 composure as though it contained loaves of bread.
"Now you can go, Rad," announced Tom, when they reached the lonely field where, pointing toward a big hill, was the little cannon.
"Good, Massa Tom!" cried the colored man, and from the way in which he hurried off no one would ever suspect him of having rheumatic joints.
"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 Ned said, swiss cheese.
And, indeed, the powerful stuff bore a decided resemblance to that peculiar product of the dairy. It was in thin sheets, with holes pierced through it here and there, irregularly.
"The idea is," Tom explained, "to make a quick-burning 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 we'll put some in the steel tube, and see what happens."
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, cheese-like 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 this, and was very careful.
The powder, as I shall occasionally call it for the sake of convenience, though it was not such in the strict sense of the word—the powder was put in the small cannon, together with the primer. Then the wires were attached to it, and extended off for some distance.
"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 there—a miniature bomb-proof, 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 inventor.
The electric wires were carried behind the protecting hill, whither they all retired.
"Here she goes!" exclaimed Tom, after a pause.
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 powerful sunlight.
"Something happened, anyhow!" yelled Tom above the reverberating echoes.
"Come on!" yelled Ned. "We'll see how this experiment came out!" and he started to run from beneath the shelter of the hill.
"Hold on!" shouted Tom, laying a restraining hand on his chum's shoulder.
"Why, what's the matter?" asked Ned in surprise.
"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 correct, but the trouble is that it's only a theory. Wait a few seconds."
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 explosion."
"This is a sort of smokeless powder," explained Tom. "It throws off a slight vapor when it is ignited, but not much. I guess it's safe to go out now. Come on!"
He dropped the pushbutton connected with the igniting battery, and, followed by the others, raced to the scene of the experiment. A curious sight met their eyes.
A great hole had been torn in the hillside, and another where the improvised gun had stood. The gun itself seemed to have disappeared.
"Why—why—where is it?" asked Ned.
"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 buried in the ground," and he indicated a third excavation in the earth.
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, and was tossed off in another direction.
"Is the gun shattered?" asked Tom, anxious to know how the weapon had fared. It was, in a sense, a sort of small model of the giant cannon he intended to have cast.
"The breech is cracked a little," answered Mr. Damon, who was examining it; "but otherwise it doesn't seem to be much damaged."
"Good," cried Tom. "Another steel jacket will remedy that defect. I guess I'm on the right road at last. But now to see what became of that armor plate."
"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 nickel-steel armor proved too much for my projectile. But we'll have a look."
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 it must be in the solid earth.
Presently they heard Koku grunting and groaning. He seemed to be having quite a struggle.
"Can you get it, Koku?" asked Tom. "Or shall I send for picks and shovels."
"Me get, Master," was the muffled answer.
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 it Tom uttered a cry.
"Look!" he shouted. "My projectile went part way through and then carried the plate with it into the side of the hill. Talk about a powerful explosive! I've struck it, all right!"
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.
"Bless my spectacle case!" cried Mr. Damon. "This is the greatest ever!"
"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 problem of the explosive. Now to work on the cannon."
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 made—or at least as far as he had any knowledge, and he had had samples of all the best makes.
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 nitro-glycerine, but that this entered into it. He agreed, however, in case his gun was accepted by the government, to disclose the secret to the ordnance officers.
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 safely—some cannon in which it could be fired to send a projectile farther than any cannon had ever sent one. And to do this much work was necessary.
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 constructed—on paper—a 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 over-charge.
"And the next thing is to get the gun cast," said Tom to Ned one day.
"Are you going to do it in your shops?" his chum asked.
"No; it would be out of the question for me. I haven't the facilities. I'm going to give the contract to the Universal Steel Company. We'll pay them a visit in a day or two."
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.
"We can't cast that gun here!" he said.
"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 the cast there."
"I never thought of that!" exclaimed the manager. "Perhaps it can be done."
"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.
"Yes, I think so. Are you going to have a wire-wound gun?"
"That, in combination with a steel-jacketed 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.
"It must be mighty powerful," exclaimed the manager.
"It is," said Tom, simply.
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 shop—a 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 earth—lined with fire-clay—would 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, red-hot, and allowed to shrink. Then would come a winding of wire, to further strengthen the tube, and then more sleeves or jackets. In this way the gun would be made very strong.
As the greatest pressure would come at the breech, or in the powder chamber there, the gun would be thickest at this point, decreasing in size to the muzzle.
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 violet-tinted glasses to protect their eyes from the glare.
"Hoist away!" cried the manager, and the electric cranes started off with the caldrons of liquid fire, weighing many tons.
"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 explosions as the air bubbles burst—explosions almost like a battery in action.
"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 guns—you never can tell when a flaw will develop. But I hope—"
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 in—I belong here in!" a voice cried. It had a German accent, and at the sound of it Tom and Ned looked at each other.
"Who is there?" asked the manager sharply of the foreman..
"Oh, a crazy German. He belongs in one of the other shops, and I guess he's mixed up. He thinks he belongs here. I sent him about his business."
"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 can't understand what that fellow wanted."
"I think I can," murmured Tom, to himself.
"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 that he's still after you."
"All right, Ned. Do as you like, only be cautious."
"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 of workmen surrounding a man who appeared to be angry.
"I dell you dot is my shop!" one of the men was heard to exclaim—a man whom the others appeared to dragging away with main force.
"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 handled—making 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 probably didn't understand where he was sent."
He passed by the group of men, who, laughing and jeering at the German, were showing him where to go. He seemed to be a new hand in the works.
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 stiffness—none of the stoop-shouldered 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 was assumed.
"I'd like to know more about you," murmured Ned, but the man, with one sharp glance at him, passed on, seemingly to his own department of the works.
"Well, what was it?" asked Tom, as his chum rejoined him.
"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 was—whatever his object was—hoped to get in to see the casting; either to get some idea about your new gun, or to do some desperate deed to spoil it."
"Do you think that, Ned?"
"I sure do. You've got to be on your guard, Tom."
"I will. But I wonder what object anyone could have in spoiling my gun?"
"So as to make his own cannon stand in a better light."
"Still thinking of General Waller, are you?"
"I am, Tom."
There was nothing more to be done at present, and, as it would take several days for the big mass of metal to properly cool, Tom, Ned and Mr. Damon returned to Shopton.
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 not accomplish.
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 inventor—tasks that were beyond his strength. But if Koku offered to help, Eradicate would draw himself up, and exclaim:
"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!"
Koku, good naturedly, gave place, for he, too, felt for Eradicate.
"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 jackets. I guess I'll keep them in my room, so I won't forget them."
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.
"Who's there?" cried Ned sharply, sitting up in bed.
Instantly the light went out, and there was silence.
"Who's there?" cried Ned again.
This time he thought he heard a stealthy footstep.
"What is it?" called Tom from his chamber.
"Someone is in here!" exclaimed Ned. "Look out, Tom!"