"Come on, Ned," said Tom, after a moment or two of silent contemplation of Eradicate. "I don't know what this cheerful camouflager of mine is talking about, but we'll have to go to see, I suppose. You say you have shut some one up in Boomerang's stable, Rad?"
"Yes, sah, Massa Tom, dat's whut I's gone an done."
"And you say he's a German?"
"I don't know as to dat, Massa Tom, but he suah done eat sauerkraut 'mostest ebery meal. Dat's whut I call him—a Sauerkrauter! An' he suah was spyin'."
"How do you know that, Rad?"
"'Cause he done went from his own shop on annuder man's ticket into de secret shop, dat's whut he went an' done!"
"Do you mean to tell me, Rad," went on Tom, "that one of the workmen from another shop entered Number Thirteen on the pass issued in the name of one of the men regularly employed in my new shop?"
"Dat's whut he done, Massa Tom."
"How do you know?"
"'Cause I detected him doin' it. Yo'-all done made me a deteckertiff, an' I detected."
"Go on, Rad."
"Well, sah, Massa Tom, I seen dish yeah Dutchman git a ticket-pass offen one ob de reg'lar men. Den he went in de unlucky place an' stayed fo' a long time. When he come out I jest natchully nabbed him, dat's whut I done, an' I took him to Boomerang's stable."
"How'd you get him to go with you?" asked Ned, for the old colored man was feeble, and most of the men employed at Tom's plant were of a robust type.
"I done fooled him. I said as how I'd jest brought from town in mah mule cart some new sauerkraut, an' he could sample it if he liked. So he went wif me, an' when I got him to de stable I pushed him in and locked de door!"
"Come on!" cried Tom to his chum. "Rad may be right, after all, and one of my workmen may be a German spy, though I've tried to weed them all out.
"However, no matter about that, if he was employed in another shop, he had no right to go into Number Thirteen. That's a violation of rules. But if he's in Rad's ramshackle stable he can easily get out."
"No, sah, dat's whut he can't do!" insisted the colored man.
"Why not?" asked Tom.
"'Cause Boomerang's on guard, an' yo'-all knows how dat mule of mine can use his heels!"
"I know, Rad," went on Tom; "but this fellow will find a way of keeping out of their way. We must hurry."
"Oh, he's safe enough," declared the colored man. "I done tole Koku to stan' guard, too! Dat low-down white trash ob a giant is all right fo' guardin', but he ain't wuff shucks at detectin'!" said Eradicate, with pardonable pride. "By golly, maybe I's too old t' put on guard, but I kin detect, all right!"
"If this proves true, I'll begin to believe you can," replied Tom. "Hop along, Ned!"
Followed by the shuffling and chuckling negro, Tom and Ned went to the rather insecure stable where the mule Boomerang was kept. That is, the stable was insecure from the standpoint of a jail. But the sight of the giant Koku marching up and down in front of the place, armed with a big club, reassured Tom.
"Is he in there, Koku?" asked the young inventor.
"Yes, Master! He try once come out, but he approach his head very close my defense weapon and he go back again."
"I should think he would," laughed Ned, as he noted the giant's club.
"Well, Rad, let's have a look at your prisoner. Open the door, Koku," commanded Tom.
"Better look out," advised Ned. "He may be armed."
"We'll have to take a chance. Besides, I don't believe he is, or he'd have fired at Koku. There isn't much to fear with the giant ready for emergencies. Now we'll see who he is. I can't imagine one of my men turning traitor."
The door was opened and a rather miserable-looking man shuffled out. There was a bloody rag on his head, and he seemed to have made more of an effort to escape than Koku described, for he appeared to have suffered in the ensuing fight.
"Carl Schwen!" exclaimed Tom. "So it was you, was it?"
The German, for such he was, did not answer for a moment. He appeared downcast, and as if suffering. Then a change came over him. He straightened up, saluted as a soldier might have done, and a sneering look came into his face. It was succeeded by one of pride as the man exclaimed:
"Yes, it is I! And I tried to do what I tried to do for the Fatherland! I have failed. Now you will have me shot as a spy, I suppose!" he added bitterly.
Tom did not answer directly. He looked keenly at the man, and at last said:
"I am sorry to see this. I knew you were a German, Schwen, but I kept you employed at work that could not, by any possibility, be considered as used against your country. You are a good machinist, and I needed you. But if what I hear about you is true, it is the end."
"It is the end," said the man simply. "I tried and failed. If it had not been for Eradicate—Well, he's smarter than I gave him credit for, that's all!"
The man spoke very good English, with hardly a trace of German accent, but there was no doubt as to his character.
"What will you do with him, Tom?" asked Ned.
"I don't know. I'll have to do a little investigating first. But he must be locked up. Schwen," went on the young inventor, "I'm sorry about this, but I shall have to give you into the custody of a United States marshal. You are not a naturalized citizen, are you?"
The man muttered something in German to the effect that he was not naturalized and was glad of it.
"Then you come under the head of an enemy alien," decided Tom, who understood what was said, "and will have to be interned. I had hoped to avoid this, but it seems it cannot be. I am sorry to lose you, but there are more important matters. Now let's get at the bottom of this."
Schwen was, after a little delay, taken in charge by the proper officer, and then a search was made of his room, for, in common with some of the other workmen, he lived in a boarding house not far from the plant.
There, by a perusal of his papers, enough was revealed to show Tom the danger he had escaped.
"And yet I don't know that I have altogether escaped it," he said to Ned, as they talked it over. "There's no telling how long this spy work may have been going on. If he has discovered all the secrets of Shop Thirteen it may be a bad thing for the Allies and—"
"Look out!" warned Ned, with a laugh. "You'll be saying things you don't want to, Tom and not at all in keeping with your former silence."
"That's so," agreed the young inventor, with a sigh. "But if things go right I'll not have to keep silent much longer. I may be able to tell you everything."
"Don't tell me—tell Mary," advised his chum. "She feels your silence more than I do. I know how such things are."
"Well, I'll be able to tell her, too," decided Tom. "That is, if Schwen hasn't spoiled everything. Look here, Ned, these papers show he's been in correspondence with Blakeson and Grinder."
"What about, Tom?"
"I can't tell. The letters are evidently written in code, and I can't translate it offhand. But I'll make another attempt at it. And here's one from a person who signs himself Walter Simpson, but the writing is in German."
"Walter Simpson!" cried Ned. "That's my friend of the tree!"
"It is?" cried Tom. "Then things begin to fit themselves together. Simpson is a spy, and he was probably trying to communicate with Schwen. But the latter didn't get the information he wanted, or, if he did get it, he wasn't able to pass it on to the man in the tree. Eradicate nipped him just in time."
And, so it seemed, the colored man had done. By accident he had discovered that Schwen had prevailed on one of the workmen in Shop 13 to change passes with him. This enabled the German spy to gain admittance to the secret place, which Tom thought was so well guarded. The man who let Schwen take the pass was in the game, too, it appeared, and he was also placed under arrest. But he was a mere tool in the pay of the others, and had no chance to gain valuable information.
A hasty search of Shop 13 did not reveal anything missing, and it was surmised (for Schwen would not talk) that he had not found time to go about and get all that he was after.
Soon after Schwen's arrest the "Spy Tree," as Tom called it, was cut down.
"Eradicate certainly did better than I ever expected he would," declared Tom. "Well, if all goes well, there won't be so much need for secrecy after a day or so. We're going to give her a test, and then—"
"Give who a test?" asked Ned, with a smile.
"You'll soon see," answered Tom, with an answering grin. "I hereby invite you and Mr. Damon to come over to Shop Thirteen day after to-morrow night and then—Well, you'll see what you'll see."
With this Ned had to be content, and he waited anxiously for the appointed time to come.
"I surely will be glad when Tom is more like himself," he mused, as he left his chum. "And I guess Mary will be, too. I wonder if he's going to ask her to the exhibition?"
It developed that Tom had done so, a fact which Ned learned on the morning of the day set for the test.
"Come over about nine o'clock," Tom said to his chum. "I guess it will be dark enough then."
Meanwhile Schwen and Otto Kuhn, the other man involved, had been locked up, and all their papers given into the charge of the United States authorities. A closer guard than ever was kept over No. 13 shop, and some of the workmen, against whom there was a slight suspicion, were transferred.
"Well, we'll see what we shall see," mused Ned on the appointed evening, when a telephone message from Mr. Damon informed the young bank clerk that the eccentric man was coming to call for him before going on to the Swift place.
"What do you think it's all about, Mr. Damon?"
"I'm sure I don't know, Ned."
The two were at the home of the young bank clerk, preparing to start for the Swift place, it being nearly nine o'clock on the evening named by the youthful inventor.
"Bless my hat-rack!" went on the eccentric man, "but Tom isn't at all like himself of late. He's working on some invention, I know that, but it's all I do know. He hasn't given me a hint of it."
"Nor me, nor any of his friends," added Ned. "And he acts so oddly about enlisting—doesn't want even to speak of it. How he got exempted I don't know, but I do know one thing, and that is Tom Swift is for Uncle Sam first, last and always!"
"Oh, of course!" agreed Mr. Damon. "Well, we'll soon know, I guess. We'd better start, Ned."
"It's useless to try to guess what it is Tom is up to. He has kept his secret well. The nearest any one has come to it was when Harry figured out that Tom had a band of giant elephants which he was fitting with coats of steel armor to go against the Germans," observed Ned, when he and Mr. Damon were on their way.
"Well, that mightn't be so bad," agreed Mr. Damon. "But—um—elephants—and wild giant ones, too! Bless my circus ticket, Ned! do you think we'd better go in that case?"
"Oh, Tom hasn't anything like that!" laughed Ned. "That was only Harry's crazy notion after he saw something big and ungainly careening about the enclosed yard of Shop Thirteen. Hello, there go Mary Nestor and her father!" and Ned pointed to the opposite side of the street where the girl and Mr. Nestor could be seen in the light of a street lamp.
"They're going out to see Tom's secret," said Mr. Damon. "There's plenty of room in my car. Let's ask them to go with us."
"Surely," agreed Ned, and a moment later he and Mary were in the rear seat while Mr. Damon and Mr. Nestor were in the front, Mr. Damon at the wheel, and they were soon speeding down the road.
"I do hope everything will go all right," observed Mary.
"What do you mean?" asked Ned.
"I mean Tom is a little bit anxious about this test."
"Did he tell you what it was to be?"
"No; but when he called to invite father and me to be present he seemed worried. I guess it's a big thing, for he never has acted this way before—not talking about his work."
"That's right," assented Ned. "But the secret will soon be disclosed, I fancy. But how is it you aren't going to the dance with Lieutenant Martin? He told me you had half accepted for to-night."
"I had." And if it had been light enough Ned would have seen Mary blushing. "I was going with him. It's a dance for the benefit of the Red Cross to get money for comfort kits for the soldiers. But when Tom sent word that he'd like to have me present to-night, why—"
"Oh, I see!" broke in Ned, with a little laugh. "'Nough said!"
Mary's blushes were deeper, but the kindly night hid them.
Then they conversed on matters connected with the big war—the selling of Liberty Bonds, the Red Cross work and the Surgical Dressings Committee, in which Mary was the head of a junior league.
"Everybody in Shopton seems to be doing something to help win the war," said Mary, and as there was just then a lull in the talk between her father and Mr. Damon her words sounded clearly.
"Yes, everybody—that is, all but a few," said Mr. Nestor, "and they ought to get busy. There are some young fellows in this town that ought to be wearing khaki, and I don't mean you, Ned Newton. You're doing your bit, all right."
"And so is Tom Swift!" exclaimed Mr. Damon, as if there had been an implied accusation against the young inventor. "I heard, only to-day, that one of his inventions—a gas helmet that he planned—is in use on the Western front in Europe. Tom gave his patents to the government, and even made a lot of the helmets free to show other factories how to turn them out to advantage."
"He did?" cried Mr. Nestor.
"That's what he did. Talk about doing your bit—"
"I didn't know that," observed Mary's father slowly. "Do you suppose it's a test of another gas helmet that Tom has asked us out to see to-night?"
"I hardly think so," said Ned. "He wouldn't wait until after dark for that. This is something big, and Tom must intend to have it out in the open. He probably waited until after sunset so the neighbors wouldn't come out in flocks. There's been a lot of talk about what is going on in Shop Thirteen, especially since the arrest of the German spies, and the least hint that a test is under way would bring out a big crowd."
"I suppose so," agreed Mr. Nestor. "Well, I'm glad to know that Tom is doing something for Uncle Sam, even if it's only helping with gas helmets. Those Germans are barbarians, if ever there were any, and we've got to fight them the same way they fight us! That's the only way to end the war! Now if I had my way, I'd take every German I could lay my hands on—"
"Father, pretzels!" exclaimed Mary.
"Eh? What's that, my dear?"
"I said pretzels!"
"Oh!" and Mr. Nestor's voice lost its sharpness.
"That's my way of quieting father down when he gets too strenuous in his talk about the war," explained Mary. "We agreed that whenever he got excited I was to say 'pretzels' to him, and that would make him remember. We made up our little scheme after he got into an argument with a man on the train and was carried past his station."
"That's right," admitted Mr. Nestor, with a laugh. "But that fellow was the most obstinate, pig-headed Dutchman that ever tackled a plate of pig's knuckles and sauerkraut, and if he had the least grain of common sense he'd—"
"Pretzels!" cried Mary.
"Eh? Oh, yes, my dear. I was forgetting again."
There was a moment of merriment, and then, after the talk had run for a while in other and safer channels, Mr. Damon made the announcement:
"I think we're about there. We'll be at Tom's place when we make the turn and—"
He was interrupted by a low, heavy rumbling.
"What's that?" asked Mr. Nestor.
"It's getting louder—the noise," remarked Mary. "It sounds as if some big body were approaching down the road—the tramp of many feet. Can it be that troops are marching away?"
"Bless my spark plug!" suddenly cried Mr. Damon. "Look!"
They gazed ahead, and there, seen in the glare of the automobile headlights, was an immense, dark body approaching them from across a level field. The rumble and roar became more pronounced and the ground shook as though from an earthquake.
A glaring light shone out from the ponderous moving body, and above the roar and rattle a voice called:
"Out out of the way! We've lost control! Look out!"
"Bless my steering wheel!" gasped Mr. Damon, "that was Tom Swift's voice! But what is he doing in that—thing?"
"It must be his new invention!" exclaimed Ned.
"What is it?" asked Mr. Nestor.
"A giant," ventured Ned. "It's a giant machine of some sort and—"
"And it's running away!" cried Mr. Damon, as he quickly steered his car to one side—and not a moment too soon! An instant later in a cloud of dust, and with a rumble and a roar as of a dozen express trains fused into one, the runaway giant—of what nature they could only guess—flashed and lumbered by, Tom Swift leaning from an opening in the thick steel side, and shouting something to his friends.
"What was it?" gasped Mary, and, to her surprise, she found herself close to Ned, clutching his arm.
"I have an idea, but I'd rather let Tom tell you," he answered.
"But where's it going?" asked Mr. Nestor. "What in the world does Tom Swift mean by inviting us out here to witness a test, and then nearly running us down under a Juggernaut?"
"Oh, there must be some mistake, I'm sure," returned his daughter. "Tom didn't intend this."
"But, bless my insurance policy, look at that thing go! What in the world is it?" cried Mr. Damon.
The "thing" was certainly going. It had careened from the road, tilted itself down into a ditch and gone on across the fields, lights shooting from it in eccentric fashion.
"Maybe we'd better take after it," suggested Mr. Nestor. "If Tom is—"
"There, it's stopping!" cried Ned. "Come on!"
He sprang from the automobile, helped Mary to get out, and then the two, followed by Mr. Damon and Mr. Nestor, made their way across the fields toward the big object where it had come to a stop, the rumbling and roaring ceasing.
Before the little party reached the strange machine—the "runaway giant," as they dubbed it in their excitement—a bright light flashed from it, a light that illuminated their path right up to the monster. And in the glare of this light they saw Tom Swift stepping out through a steel door in the side of the affair.
"Are you all right?" he called to his friends, as they approached.
"All right, as nearly as we can be when we've been almost scared to death, Tom," said Mr. Nestor.
"I'm surely sorry for what happened," Tom answered, with a relieved laugh. "Part of the steering gear broke and I had to guide it by operating the two motors alternately. It can be worked that way, but it takes a little practice to become expert."
"I should say so!" cried Mr. Damon. "But what in the world does it all mean, Tom Swift? You invite us out to see something—"
"And there she is!" interrupted the young inventor. "You saw her a little before I meant you to, and not under exactly the circumstances I had planned. But there she is!" And he turned as though introducing the metallic monster to his friends.
"What is she, Tom?" asked Ned. "Name it!"
"My latest invention, or rather the invention of my father and myself," answered Tom, and his voice showed the love and reverence he felt for his parent. "Perhaps I should say adaptation instead of invention," Tom went on, "since that is what it is. But, at any rate, it's my latest—dad's and mine—and it's the newest, biggest, most improved and powerful fighting tank that's been turned out of any shop, as far as I can learn.
"Ladies—I mean lady and gentlemen—allow me to present to you War Tank A, and may she rumble till the pride of the Boche is brought low and humble!" cried Tom.
"Hurray! That's what I say!" cheered Ned.
"That's what I have been at work on lately. I'll give you a little history of it, and then you may come inside and have a ride home."
"In that?" cried Mr. Damon.
"Yes. I can't promise to move as speedily as your car, but I can make better time than the British tanks. They go about six miles an hour, I understand, and I've got mine geared to ten. That's one improvement dad and I have made."
"Ride in that!" cried Mr. Nestor. "Tom, I like you, and I'm glad to see I've been mistaken about you. You have been doing your bit, after all; but—"
"Oh, I've only begun!" laughed Tom Swift.
"Well, no matter about that. However much I like you," went on Mr. Nestor, "I'd as soon ride on the wings of a thunderbolt as in Tank A, Tom Swift."
"Oh, it isn't as bad as that!" laughed the young scientist. "But neither is it a limousine. However, come inside, anyhow, and I'll tell you something about it. Then I guess we can guide it back. The men are repairing the break."
The visitors entered the great craft through the door by which Tom had emerged. At first all they saw was a small compartment, with walls of heavy steel, some shelves of the same and a seat which folded up against the wall made of like powerful material.
"This is supposed to be the captain's room, where he stays when he directs matters." Tom explained. "The machinery is below and beyond here."
"How'd you come to evolve this?" asked Ned. "I haven't seen half enough of the outside, to say nothing of the inside."
"You'll have time enough," Tom said. "This is my first completed tank. There are some improvements to be made before we send it to the other side to be copied.
"Then they'll make them in England as well as here, and from here we'll ship them in sections."
"I don't see how you ever thought of it!" exclaimed the girl, in wonder.
"Well, I didn't all at once," Tom answered, with a laugh. "It came by degrees. I first got the idea when I heard of the British tanks.
"When I had read how they went into action and what they accomplished against the barbed wire entanglements, and how they crossed the trenches, I concluded that a bigger tank, one capable of more speed, say ten or twelve miles an hour, and one that could cross bigger excavations—the English tanks up to this time can cross a ditch of twelve feet—I thought that, with one made on such specifications, more effective work could be done against the Germans."
"And will yours do that?" asked Ned. "I mean will it do ten miles an hour, and straddle over a wider ditch than twelve feet?"
"It'll do both," promptly answered Tom. "We did a little better than eleven miles an hour a while ago when I yelled to you to get out of the way just now. It's true we weren't under good control, but the speed had nothing to do with that. And as for going over a big ditch, I think we straddled one about fourteen feet across back there, and we can do better when I get my grippers to working."
"Grippers!" exclaimed Mary.
"What kind of trench slang is that, Tom Swift?" asked Mr. Damon.
"Well, that's a new idea I'm going to try out It's something like this," and while from a distant part of the interior of Tank A came the sound of hammering, the young inventor rapidly drew a rough pencil sketch.
It showed the tank in outline, much as appear the pictures of tanks already in service—the former simile of two wedge-shaped pieces of metal put together broad end to broad end, still holding good. From one end of the tank, as Tom drew it, there extended two long arms of latticed steel construction.
"The idea is," said Tom, "to lay these down in front of the tank, by means of cams and levers operated from inside. If we get to a ditch which we can't climb down into and out again, or bridge with the belt caterpillar wheels, we'll use the grippers. They'll be laid down, taking a grip on the far side of the trench, and we'll slide across on them."
"And leave them there?" asked Mr. Damon.
"No, we won't leave them. We'll pick them up after we have passed over them and use them in front again as we need them. A couple of extra pairs of grippers may be carried for emergencies, but I plan to use the same ones over and over again."
"But what makes it go?" asked Mary. "I don't want all the details, Tom," she said, with a smile, "but I'd like to know what makes your tank move."
"I'll be able to show you in a little while," he answered. "But it may be enough now if I tell you that the main power consists of two big gasolene engines, one on either side. They can be geared to operate together or separately. And these engines turn the endless belts made of broad, steel plates, on which the tank travels. The belts pass along the outer edges of the tank longitudinally, and go around cogged wheels at either end of the blunt noses.
"When both belts travel at the same rate of speed the tank goes in a straight line, though it can be steered from side to side by means of a trailer wheel in the rear. Making one belt—one set of caterpillar wheels, you know—go faster than the other will make the tank travel to one side or the other, the turn being in the direction of the slowest moving belt. In this way we can steer when the trailer wheels are broken."
"And what does your tank do except travel along, not minding a hail of bullets?" asked Mr. Nestor.
"Well," answered Tom, "it can do anything any other tank can do, and then some more. It can demolish a good-sized house or heavy wall, break down big trees, and chew up barbed-wire fences as if they were toothpicks. I'll show you all that in due time. Just now, if the repairs are finished, we can get back on the road—"
At that moment a door leading into the compartment where Tom and his friends were talking opened, and one of the workmen said:
"A man outside asking to see you, Mr. Swift."
"Pardon me, but I won't keep you a moment," interrupted a suave voice. "I happened to observe your tank, and I took the liberty of entering to see—"
"Simpson!" cried Ned Newton, as he recognized the man who had been up the tree. "It's that spy, Simpson, Tom!"
Such surprise showed both on the face of Ned Newton and that of the man who called himself Walter Simpson that it would be hard to say which was in the greater degree. For a moment the newcomer stood as if he had received all electric shock, and was incapable of motion. Then, as the echoes of Ned's voice died away and the young bank clerk, being the first to recover from the shock, made a motion toward the unwelcome and uninvited intruder, Simpson exclaimed.
"I will not bother now. Some other time will do as well."
Then, with a haste that could be called nothing less than precipitate, he made a turn and fairly shot out of the door by which he had entered the tank.
"There he goes!" cried Mr. Damon. "Bless my speedometer, but there he goes!"
"I'll stop him!" cried Ned. "We've got to find out more about him! I'll get him, Tom!"
Tom Swift was not one to let a friend rush alone into what might be danger. He realized immediately what his chum meant when he called out the identity of the intruder, and, wishing to clear up some of the mystery of which he became aware when Schwen was arrested and the paper showing a correspondence with this Simpson were found, Tom darted out to try to assist in the capture.
"He went this way!" cried Ned, who was visible in the glare of the searchlight that still played its powerful beams over the stern of the tank, if such an ungainly machine can be said to have a bow and stern. "Over this way!"
"I'm with you!" cried Tom. "See if you can pick up that man who just ran out of here!" he cried to the operator of the searchlight in the elevated observation section of what corresponded to the conning tower of a submarine. This was a sort of lookout box on top of the tank, containing, among other machines, the searchlight. "Pick him up!" cried Tom.
The operator flashed the intense white beam, like a finger of light, around in eccentric circles, but though this brought into vivid relief the configuration of the field and road near which the tank was stalled, it showed no running fugitive. Tom and Ned were observed—shadows of black in the glare—by Mary and her friends in the tank, but there was no one else.
"Come on!" cried Ned. "We can find him, Tom!"
But this was easier said than done. Even though they were aided by the bright light, they caught no glimpse of the man who called himself Simpson.
"Guess he got away," said Tom, when he and Ned had circled about and investigated many clumps of bushes, trees, stumps and other barriers that might conceal the fugitive.
"I guess so," agreed Ned. "Unless he's hiding in what we might call a shell crater."
"Hardly that," and Tom smiled. "Though if all goes well the men who operate this tank later may be searching for men in real shell holes."
"Is this one going to the other side?" asked Ned, as the two walked back toward the tank.
"I hope it will be the first of my new machines on the Western front," Tom answered. "But I've still got to perfect it in some details and then take it apart. After that, if it comes up to expectations, we'll begin making them in quantities."
"Did you get him?" asked Mr. Damon eagerly, as the two young men came back to join Mary and her friends.
"No, he got away," Tom answered.
"Did he try to blow up the tank?" asked Mr. Nestor, who had an abnormal fear of explosives. "Was he a German spy?"
"I think he's that, all right," said Ned grimly. "As to his endeavoring to blow up Tom's tank, I believe him capable of it, though he didn't try it to-night—unless he's planted a time bomb somewhere about, Tom."
"Hardly, I guess," answered the young inventor. "He didn't have a chance to do that. Anyhow we won't remain here long. Now, Ned, what about this chap? Is he really the one you saw up in the tree?"
"I not only saw him but I felt him," answered Ned, with a rueful look at his fingers. "He stepped right on me. And when he came inside the tank to-night I knew him at once. I guess he was as surprised to see me as I was to see him."
"But what was his object?" asked Mr. Nestor.
"He must have some connection with my old enemy, Blakeson," answered Tom, "and we know he's mixed up with Schwen. From the looks of him I should say that this Simpson, as he calls himself, is the directing head of the whole business. He looks to be the moneyed man, and the brains of the plotters. Blakeson is smart, in a mechanical way, and Schwen is one of the best machinists I've ever employed. But this Simpson strikes me as being the slick one of the trio."
"But what made him come here, and what did he want?" asked Mary. "Dear me! it's like one of those moving picture plots, only I never saw one with a tank in it before—I mean a tank like yours, Tom."
"Yes, it is a bit like moving picture—especially chasing Simpson by searchlight," agreed the young inventor. "As to what he wanted, I suppose he came to spy out some of my secret inventions—dad's and mine. He's probably been hiding and sneaking around the works ever since we arrested Schwen. Some of my men have reported seeing strangers about, but I have kept Shop Thirteen well guarded.
"However, this fellow may have been waiting outside, and he may have followed the tank when we started off a little while ago for the night test. Then, when he saw our mishap and noticed that we were stalled, he came in, boldly enough, thinking, I suppose, that, as I had never seen him, he would take a chance on getting as much information as he could in a hurry."
"But he didn't count on Ned's being here!" chuckled Mr. Damon.
"No; that's where he slipped a cog," remarked Mr. Nestor. "Well, Tom, I like your tank, what I've seen of her, but it's getting late and I think Mary and I had better be getting back home."
"We'll be ready to start in a little while," Tom said, after a brief consultation with one of his men. "Still, perhaps it would be just as well if you didn't ride back with me. She may go all right, and then, again, she may not. And as it's dark, and we're in a rough part of the field, you might be a bit shaken up. Not that the tank minds it!" the young inventor hastened to add "She's got to do her bit over worse places than this—much worse—but I want to get her in a little better working shape first. So if you don't mind, Mary, I'll postpone your initial trip."
"Oh, I don't mind, Tom! I'm so glad you've made this! I want to see the war ended, and I think machines like this will help."
"I'll ride back with you, Tom, if you don't mind," put in Ned. "I guess a little shaking up won't hurt me."
"All right—stick. We're going to start very soon."
"Well, I'm coming over to-morrow to have a look at it by daylight," said Mr. Damon, as he started toward his car.
"So am I," added Mary. "Please call for me, Mr. Damon."
"I will," he promised.
Mr. Nestor, his daughter, and Mr. Damon went back to the automobile, while Ned remained with Tom. In a little while those in the car heard once more the rumbling and roaring sound and felt the earth tremble. Then, with a flashing of lights, the big, ungainly shape of the tank lifted herself out of the little ditch in which she had come to a halt, and began to climb back to the road.
Ned Newton stood beside Tom in the control tower of the great tank as she started on her homeward way.
"Isn't it wonderful!" murmured Mary, as she saw Tank A lumbering along toward the road. "Oh, and to think that human beings made that. To think that Tom should know how to build such a wonderful machine!"
"And run it, too, Mary! That's the point! Make it run!" cried her father. "I tell you, that Tom Swift is a wonder!"
"Bless my dictionary, he sure is!" agreed Mr. Damon.
Along the road, back toward the shop whence it had emerged, rumbled the tank. The noise brought to their doors inhabitants along the country thoroughfare, and some of them were frightened when they saw Tom Swift's latest war machine, the details of which they could only guess at in the darkness.
"She'll butt over a house if it gets in her path, knock down trees, chew up barbed-wire, and climb down into ravines and out again, and go over a good-sized stream without a whimper," said Tom, as he steered the great machine.
There was little chance then for Ned to see much of the inside mechanism of the tank. He observed that Tom, standing in the forward tower, steered it very easily by a small wheel or by a lever, alternately, and that he communicated with the engine room by means of electric signals.
"And she steers by electricity, too," Tom told his friend. "That was one difficulty with the first tanks. They had to be steered by brute force, so to speak, and it was a terrific strain on the man in the tower. Now I can guide this in two ways: by the electric mechanism which swings the trailer wheels to either side, or by varying the speed of the two motors that work the caterpillar belts. So if one breaks down, I have the other."
"Got any guns aboard her—I mean machine guns?" asked Ned.
"Not yet. But I'm going to install some. I wanted to get the tank in proper working order first. The guns are only incidental, though of course they're vitally necessary when she goes into action. I've got 'em all ready to put in. But first I'm going to try the grippers."
"Oh, you mean the gap-bridgers?" asked Ned.
"That's it," answered Tom. "Look out, we're going over a rough spot now."
And they did. Ned was greatly shaken up, and fairly tossed from side to side of the steering tower. For the tank contained no springs, except such as were installed around the most delicate machinery, and it was like riding in a dump cart over a very rough road.
"However, that's part of the game," Tom observed.
Tank A reached her "harbor" safely—in other words, the machine shop enclosed by the high fence, inside of which she had been built.
Tom and Ned made some inquiries of Koku and Eradicate as to whether or not there had been any unusual sights or sounds about the place. They feared Simpson might have come to the shop to try to get possession of important drawings or data.
But all had been quiet, Koku reported. Nor had Eradicate seen or heard anything out of the ordinary.
"Then I guess we'll lock up and turn in," decided Tom. "Come over to-morrow, Ned."
"I will," promised the young bank clerk. "I want to see more of what makes the wheels go round." And he laughed at his own ingenuousness.
The next day Tom showed his friends as much as they cared to see about the workings of the tank. They inspected the powerful gasolene engines, saw how they worked the endless belts made of plates of jointed steel, which, running over sprocket wheels, really gave the tank its power by providing great tractive force.
Any self-propelled vehicle depends for its power, either to move itself or to push or to pull, on its tractive force—that is, the grip it can get on the ground.
In the case of a bicycle little tractive power is needed, and this is provided by the rubber tires, which grip the ground. A locomotive depends for its tractive power on its weight pressing on its driving wheels, and the more driving wheels there are and the heavier the locomotive, the more it can pull, though in that case speed is lost. This is why freight locomotives are so heavy and have so many large driving wheels. They pull the engine along, and the cars also, by their weight pressing on the rails.
The endless steel belts of a tank are, the same as the wheels of a locomotive. And the belts, being very broad, which gives them a large surface with which to press on the ground, and the tank being very heavy, great power to advance is thus obtained, though at the sacrifice of speed. However, Tom Swift had made his tank so that it would do about ten miles and more an hour, nearly double the progress obtained up to that time by the British machines.
His visitors saw the great motors, they inspected the compact but not very attractive living quarters of the crew, for provision had to be made for the men to stay in the tank if, perchance, it became stalled in No Man's Land, surrounded by the enemy.
The tank was powerfully armored and would be armed. There were a number of machine guns to be installed, quick-firers of various types, and in addition the tank could carry a number of riflemen.
It was upon the crushing power of the tank, though, that most reliance was placed. Thus it could lead the way for an infantry advance through the enemy's lines, making nothing of barbed wire that would take an artillery fire of several days to cut to pieces.
"And now, Ned," said Tom, about a week after the night test of the tank, "I'm going to try what she'll do in bridging a gap."
"Have you got her in shape again?"
"Yes, everything is all right. I've taken out the weak part in the steering gear that nearly caused us to run you down, and we're safe in that respect now. And I've got the grippers made. It only remains to see whether they're strong enough to bear the weight of my little baby," and Tom affectionately patted the steel sides of Tank A.
While his men were getting the machine ready for a test out on the road, and for a journey across a small stream not far away, Tom told his chum about conceiving the idea for the tank and carrying it out secretly with the aid of his father and certain workmen.
"That's the reason the government exempted me from enlisting," Tom said. "They wanted me to finish this tank. I didn't exactly want to, but I considered it my 'bit.' After this I'm going into the army, Ned."
"Glad to hear it, old man. Maybe by that time I'll have this Liberty Bond work finished, and I'll go with you. We'll have great times together! Have you heard anything more of Simpson, Blakeson and Scoundrels?" And Ned laughed as he named this "firm."
"No," answered Tom. "I guess we scared off that slick German spy."
Once more the tank lumbered out along the road. It was a mighty engine of war, and inside her rode Tom and Ned. Mary and her father had been invited, but the girl could not quite get her courage to the point of accepting, nor did Mr. Nestor care to go. Mr. Damon, however, as might be guessed, was there.
"Bless my monkey wrench, Tom!" cried the eccentric man, as he noted their advance over some rough ground, "are you really going to make this machine cross Tinkle Creek on a bridge of steel you carry with you?"
"I'm going to try, Mr. Damon."
A little later, after a successful test up and down a small gully, Tank A arrived at the edge of Tinkle Creek, a small stream about twenty feet wide, not far from Tom's home. At the point selected for the test the banks were high and steep.
"If she bridges that gap she'll do anything," murmured Ned, as the tank came to a stop on the edge.