Not for long did the young inventor endeavor to break his way out of the water-ballast tank by striking the heavy sides of it. Tom realized that this was worse than useless. He listened intently, but could hear nothing. Even the retreating footsteps of Andy Foger were inaudible.
"This certainly is a pickle!" exclaimed Tom aloud. "I can't understand how he ever got here. He must have traced us after we went to Shopton in the airship the last time. Then he sneaked in here. Probably he saw me enter, but how could he know enough to work the worm gear and close the door? Andy has had some experience with machinery, though, and one of the vaults in the bank where his father is a director closed just like this tank. That's very likely how he learned about it. But I've got to do something else besides thinking of that sneak, Andy. I've got to get out of here. Let's see if I can work the gear from inside."
Before he started, almost, Tom knew that it would be impossible. The tank was made to close from the interior of the submarine, and the heavy door, built to withstand the pressure of tons of water, could not be forced except by the proper means.
"No use trying that," concluded the lad, after a tiring attempt to force back the sliding door with his hands. "I've got to call for help."
He shouted until the vibrations in the confined space made his ears ring, and the mere exertion of raising his voice to the highest pitch made his heart beat quickly. Yet there came no response. He hardly expected that there would be any, for with his father and Mr. Sharp away, the engineer absent on an errand, and Mrs. Baggert in the house some distance off, there was no one to hear his calls for help, even if they had been capable of penetrating farther than the extent of the shed, where the under-water craft had been constructed.
"I've got to wait until some of them come out here," thought Tom. "They'll be sure to release me and make a search. Then it will be easy enough to call to them and tell them where I am, once they are inside the shed. But—" He paused, for a horrible fear came over him. "Suppose they should come—too late?" The tank was airtight. There was enough air in it to last for some time, but, sooner or later, it would no longer support life. Already, Tom thought, it seemed oppressive, though probably that was his imagination.
"I must get out!" he repeated frantically. "I'll die in here soon."
Again he tried to shove back the steel door. Then he repeated his cries until he was weary. No one answered him. He fancied once he could hear footsteps in the shed, and thought, perhaps, it was Andy, come back to gloat over him. Then Tom knew the red-haired coward would not dare venture back. We must do Andy the justice to say that he never realized that he was endangering Tom's life. The bully had no idea the tank was airtight when he closed it. He had seen Tom enter and a sudden whim came to him to revenge himself.
But that did not help the young inventor any. There was no doubt about it now—the air was becoming close. Tom had been imprisoned nearly two hours, and as he was a healthy, strong lad, he required plenty of oxygen. There was certainly less than there had been in the tank. His head began to buzz, and there was a ringing in his ears.
Once more he fell upon his knees, and his fingers sought the small projections of the gear on the inside of the door. He could no more budge the mechanism than a child could open a burglar-proof vault.
"It's no use," he moaned, and he sprawled at full length on the floor of the tank, for there the air was purer. As he did so his fingers touched something. He started as they closed around the handle of a big monkey wrench. It was one he had brought into the place with him. Imbued with new hope he struck a match and lighted his lantern, which he had allowed to go out as it burned up too much of the oxygen. By the gleam of it he looked to see if there were any bolts or nuts he could loosen with the wrench, in order to slide the door back. It needed but a glance to show him the futility of this.
"It's no go," he murmured, and he let the wrench fall to the floor. There was a ringing, clanging sound, and as it smote his ears Tom sprang up with an exclamation.
"That's the thing!" he cried. "I wonder I didn't think of it before. I can signal for help by pounding on the sides of the tank with the wrench. The blows will carry a good deal farther than my voice would." Every one knows how far the noise of a boiler shop, with hammers falling on steel plates, can be heard; much farther than can a human voice.
Tom began a lusty tattoo on the metal sides of the tank. At first he merely rattled out blow after blow, and then, as another thought came to him, he adopted a certain plan. Some time previous, when he and Mr. Sharp had planned their trip in the air, the two had adopted a code of signals. As it was difficult in a high wind to shout from one end of the airship to the other, the young inventor would sometimes pound on the pipe which ran from the pilot house of the Red Cloud to the engine-room. By a combination of numbers, simple messages could be conveyed. The code included a call for help. Forty-seven was the number, but there had never been any occasion to use it.
Tom remembered this now. At once he ceased his indiscriminate hammering, and began to beat out regularly—one, two, three, four—then a pause, and seven blows would be given. Over and over again he rang out this number—forty seven—the call for help.
"If Mr. Sharp only comes back he will hear that, even in the house," thought poor Tom "Maybe Garret or Mrs. Baggert will hear it, too, but they won't know what it means. They'll think I'm just working on the submarine."
It seemed several hours to Tom that he pounded out that cry for aid, but, as he afterward learned, it was only a little over an hour. Signal after signal he sent vibrating from the steel sides of the tank. When one arm tired he would use the other. He grew weary, his head was aching, and there was a ringing in his ears; a ringing that seemed as if ten thousand bells were jangling out their peals, and he could barely distinguish his own pounding.
Signal after signal he sounded. It was becoming like a dream to him, when suddenly, as he paused for a rest, he heard his name called faintly, as if far away.
"Tom! Tom! Where are you?"
It was the voice of Mr. Sharp. Then followed the tones of the aged inventor.
"My poor boy! Tom, are you still alive?"
"Yes, dad! In the starboard tank!" the lad gasped out, and then he lost his senses. When he revived he was lying on a pile of bagging in the submarine shop, and his father and the aeronaut were bending over him.
"Are you all right, Tom?" asked Mr. Swift.
"Yes—I—I guess so," was the hesitating answer. "Yes," the lad added, as the fresh air cleared his head. "I'll be all right pretty soon. Have you seen Andy Foger?"
"Did he shut you in there?" demanded Mr. Swift.
Tom nodded.
"I'll have him arrested!" declared Mr. Swift. "I'll go to town as soon as you're in good shape again and notify the police."
"No, don't," pleaded Tom. "I'll take care of Andy myself. I don't really believe he knew how serious it was. I'll settle with him later, though."
"Well, it came mighty near being serious," remarked Mr. Sharp grimly. "Your father and I came back a little sooner than we expected, and as soon as I got near the house I heard your signal. I knew what it was in a moment. There were Mrs. Baggert and Garret talking away, and when I asked them why they didn't answer your call they said they thought you were merely tinkering with the machinery. But I knew better. It's the first time we ever had a use for 'forty-seven,' Tom."
"And I hope it will be the last," replied the young inventor with a faint smile. "But I'd like to know what Andy Foger is doing in this neighborhood."
Tom was soon himself again and able to go to the house, where he found Mrs. Baggert brewing a big basin of catnip tea, under the impression that it would in some way be good for him. She could not forgive herself for not having answered his signal, and as for Mr. Jackson, he had started for a doctor as soon as he learned that Tom was shut up in the tank. The services of the medical man were canceled by telephone, as there was no need for him, and the engineer came back to the house.
Tom was fully himself the next day, and aided his father and Mr. Sharp in putting the finishing touches to the Advance. It was found that some alteration was required in the auxiliary propellers, and this, much to the regret of the young inventor, would necessitate postponing the trial a few days.
"But we'll have her in the water next Friday," promised Mr. Swift.
"Aren't you superstitious about Friday?" asked the balloonist.
"Not a bit of it," replied the aged inventor. "Tom," he added, "I wish you would go in the house and get me the roll of blueprints you'll find on my desk."
As the lad neared the cottage he saw, standing in front of the place, a small automobile. A man had just descended from it, and it needed but a glance to show that he was Mr. Addison Berg.
"Ah, good morning, Mr. Swift," greeted Mr. Berg. "I wish to see your father, but as I don't wish to lay myself open to suspicions by entering the shop, perhaps you will ask him to step here."
"Certainly," answered the lad, wondering why the agent had returned. Getting the blueprints, and asking Mr. Berg to sit down on the porch, Tom delivered the message.
"You come back with me, Tom," said his father. "I want you to be a witness to what he says. I'm not going to get into trouble with these people."
Mr. Berg came to the point at once.
"Mr. Swift," he said, "I wish you would reconsider your determination not to enter the Government trials. I'd like to see you compete. So would my firm."
"There is no use going over that again," replied the aged inventor. "I have another object in view now than trying for the Government prize. What it is I can't say, but it may develop in time—if we are successful," and he looked at his son, smiling the while.
Mr. Berg tried to argue, but it was of no avail. Then he changed his manner, and said:
"Well, since you won't, you won't, I suppose. I'll go back and report to my firm. Have you anything special to do this morning?" he went on to Tom.
"Well, I can always find something to keep me busy," replied the lad, "but as for anything special—"
"I thought perhaps you'd like to go for a trip in my auto," interrupted Mr. Berg. "I had asked a young man who is stopping at the same hotel where I am to accompany me, but he has unexpectedly left, and I don't like to go alone. His name was—let me see. I have a wretched memory for names, but it was something like Roger or Moger."
"Foger!" cried Tom. "Was it Andy Foger?"
"Yes, that was it. Why, do you know him?" asked Mr. Berg in some surprise.
"I should say so," replied Tom. "He was the cause of what might have resulted in something serious for me," and the lad explained about being imprisoned in the tank.
"You don't tell me!" cried Mr. Berg. "I had no idea he was that kind of a lad. You see, his father is one of the directors of the firm by whom I am employed. Andy came from home to spend a few weeks at the seaside, and stopped at the same hotel that I did. He went off yesterday afternoon, and I haven't seen him since, though he promised to go for a ride with me. He must have come over here and entered your shop unobserved. I remember now he asked me where the submarine was being built that was going to compete with our firm's, and I told him. I didn't think he was that kind of a lad. Well, since he's probably gone back home, perhaps you will come for a ride with me, Tom."
"I'm afraid I can't go, thank you," answered the lad. "We are very busy getting our submarine in shape for a trial. But I can imagine why Andy left so hurriedly. He probably learned that a doctor had been summoned for me, though, as it happened, I didn't need one. But Andy probably got frightened at what he had done, and left. I'll make him more sorry, when I meet him."
"Don't blame you a bit," commented Mr. Berg. "Well, I must be getting back."
He hastened out to his auto, while Tom and his father watched the agent.
"Tom, never trust that man," advised the aged inventor solemnly.
"Just what I was about to remark," said his son. "Well, let's get back to work. Queer that he should come here again, and it's queer about Andy Foger."
Father and son returned to the machine shop, while Mr. Berg puffed away in his auto. A little later, Tom having occasion to go to a building near the boundary line of the cottage property which his father had hired for the season, saw, through the hedge that bordered it, an automobile standing in the road. A second glance showed him that it was Mr. Berg's machine. Something had gone wrong with it, and the agent had alighted to make an adjustment.
The young inventor was close to the man, though the latter was unaware of his presence.
"Hang it all!" Tom heard Mr. Berg exclaim to himself. "I wonder what they can be up to? They won't enter the Government contests, and they won't say why. I believe they're up to some game, and I've got to find out what it is. I wonder if I couldn't use this Foger chap?"
"He seems to have it in for this Tom Swift," Mr. Berg went on, still talking to himself, though not so low but that Tom could hear him. "I think I'll try it. I'll get Andy Foger to sneak around and find out what the game is. He'll do it, I know."
By this time the auto was in working order again, and the agent took his seat and started off.
"So that's how matters lie, eh?" thought Tom. "Well, Mr. Berg, we'll be doubly on the lookout for you after this. As for Andy Foger, I think I'll make him wish he'd never locked me in that tank. So you expect to find out our 'game,' eh, Mr. Berg? Well, when you do know it, I think it will astonish you. I only hope you don't learn what it is until we get at that sunken treasure, though."
But alas for Tom's hopes. Mr. Berg did learn of the object of the treasure-seekers, and sought to defeat them, as we shall learn as our story proceeds.
When the young inventor informed his father what he had overheard Mr. Berg saying, the aged inventor was not as much worried as his son anticipated.
"All we'll have to do, Tom," he said, "is to keep quiet about where we are going. Once we have the Advance afloat, and try her out, we can start on our voyage for the South American Coast and search for the sunken treasure. When we begin our voyage under water I defy any one to tell where we are going, or what our plans are. No, I don't believe we need worry about Mr. Berg, though he probably means mischief."
"Well, I'm going to keep my eyes open for him and Andy Foger," declared Tom.
The days that followed were filled with work. Not only were there many unexpected things to do about the submarine, but Mr. Sharp was kept busy making inquiries about the sunken treasure ship. These inquiries had to be made carefully, as the adventurers did not want their plans talked of, and nothing circulates more quickly than rumors of an expedition after treasure of any kind.
"What about the old sea captain you were going to get to go with us?" asked Mr. Swift of the balloonist one afternoon. "Have you succeeded in finding one yet?"
"Yes; I am in communication with a man I think will be just the person for us. His name is Captain Alden Weston, and he has sailed all over the world. He has also taken part in more than one revolution, and, in fact, is a soldier of fortune. I do not know him personally, but a friend of mine knows him, and says he will serve us faithfully. I have written to him, and he will be here in a few days."
"That's good. Now about the location of the wreck itself. Have you been able to learn any more details?"
"Well, not many. You see, the Boldero was abandoned in a storm, and the captain did not take very careful observations. As nearly as it can be figured out the treasure ship went to the bottom in latitude forty-five degrees south, and longitude twenty-seven east from Washington. That's a pretty indefinite location, but I hope, once we get off the Uruguay coast, we can better it. We can anchor or lay outside the harbor, and in the small boat we carry go ashore and possibly gain more details. For it was at Montevideo that the shipwrecked passengers and sailors landed."
"Does Captain Weston know our object?" inquired Tom.
"No, and I don't propose to tell him until we are ready to start," replied Mr. Sharp. "I don't know just how he'll consider a submarine trip after treasure, but if I spring it on him suddenly he's less likely to back out. Oh, I think he'll go."
Somewhat unexpectedly the next day it was discovered that certain tools and appliances were needed for the submarine, and they had been left in the house at Shopton, where Eradicate Sampson was in charge as caretaker during the absence of Mr. Swift and his son and the housekeeper.
"Well, I suppose we'll have to go back after them," remarked Tom. "We'll take the airship, dad, and make a two-days' trip of it. Is there anything else you want?"
"Well, you might bring a bundle of papers you'll find in the lower right hand drawer of my desk. They contain some memoranda I need."
Tom and Mr. Sharp had become so used to traveling in the airship that it seemed no novelty to them, though they attracted much attention wherever they went. They soon had the Red Cloud in readiness for a flight, and rising in the air above the shop that contained the powerful submarine, a craft utterly different in type from the aeroplane, the nose of the airship was pointed toward Shopton.
They made a good flight and landed near the big shed where the bird of the air was kept. It was early evening when they got to the Swift homestead, and Eradicate Sampson was glad to see them.
Eradicate was a good cook, and soon had a meal ready for the travelers. Then, while Mr. Sharp selected the tools and other things needed, and put them in the airship ready for the start back the next morning, Tom concluded he would take a stroll into Shopton, to see if he could see his friend, Ned Newton. It was early evening, and the close of a beautiful day, a sharp shower in the morning having cooled the air.
Tom was greeted by a number of acquaintances as he strolled along, for, since the episode of the bank robbery, when he had so unexpectedly returned with the thieves and the cash, the lad was better known than ever.
"I guess Ned must be home," thought our hero as he looked in vain for his chum among the throng on the streets. "I've got time to take a stroll down to his house."
Tom was about to cross the street when he was startled by the sound of an automobile horn loudly blown just at his side. Then a voice called:
"Hey, there! Git out of the way if you don't want to be run over!"
He looked up, and saw a car careening along. At the wheel was the red-haired bully, Andy Foger, and in the tonneau were Sam Snedecker and Pete Bailey.
"Git out of the way," added Sam, and he grinned maliciously at Tom.
The latter stepped back, well out of the path of the car, which was not moving very fast. Just in front of Tom was a puddle of muddy water. There was no necessity for Andy steering into it, but he saw his opportunity, and a moment later one of the big pneumatic tires had plunged into the dirty fluid, spattering it all over Tom, some even going as high as his face.
"Ha! ha!" laughed Andy. "Maybe you'll get out of my way next time, Tom Swift."
The young inventor was almost speechless from righteous anger. He wiped the mud from his face, glanced down at his clothes, which were all but ruined, and called out:
"Hold on there, Andy Foger! I want to see you!" for he thought of the time when Andy had shut him in the tank.
"Ta! ta!" shouted Pete Bailey.
"See you later," added Sam.
"Better go home and take a bath, and then sail away in your submarine," went on Andy. "I'll bet it will sink."
Before Tom could reply the auto had turned a corner. Disgusted and angry, he tried to sop up some of the muddy water with his handkerchief. While thus engaged he heard his name called, and looked up to see Ned Newton.
"What's the matter? Fall down?" asked his chum.
"Andy Foger," replied Tom.
"That's enough," retorted Ned. "I can guess the rest. We'll have to tar and feather him some day, and ride him out of town on a rail. I'd kick him myself, only his father is a director in the bank where I work, and I'd be fired if I did. Can't afford any such pleasure. But some day I'll give Andy a good trouncing, and then resign before they can discharge me. But I'll be looking for another job before I do that. Come on to my house, Tom, and I'll help you clean up."
Tom was a little more presentable when he left his chum's residence, after spending the evening there, but he was still burning for revenge against Andy and his cronies. He had half a notion to go to Andy's house and tell Mr. Foger how nearly serious the bully's prank at the submarine had been, but he concluded that Mr. Foger could only uphold his son. "No, I'll settle with him myself," decided Tom.
Bidding Eradicate keep a watchful eye about the house, and leaving word for Mr. Damon to be sure to come to the coast if he again called at the Shopton house, Tom and Mr. Sharp prepared to make their return trip early the next morning.
The gas tank was filled and the Red Cloud arose in the air. Then, with the propellers moving at moderate speed, the nose of the craft was pointed toward the New Jersey coast.
A few miles out from Shopton, finding there was a contrary wind in the upper regions where they were traveling, Mr. Sharp descended several hundred feet. They were moving over a sparsely settled part of the country, and looking down, Tom saw, speeding along a highway, an automobile.
"I wonder who's in it?" he remarked, taking down a telescope and peering over the window ledge of the cabin. The next moment he uttered a startled exclamation.
"Andy Foger, Sam Snedecker and Pete Bailey!" he cried. "Oh, I wish I had a bucket of water to empty on them."
"I know a better way to get even with them than that," said Mr. Sharp.
"How?" asked Tom eagerly.
"I'll show you," replied the balloonist. "It's a trick I once played on a fellow who did me an injury. Here, you steer for a minute until I get the thing fixed, then I'll take charge."
Mr. Sharp went to the storeroom and came back with a long, stout rope and a small anchor of four prongs. It was carried to be used in emergencies, but so far had never been called into requisition. Fastening the grapple to the cable, the balloonist said:
"Now, Tom, they haven't seen you. You stand in the stern and pay out the rope. I'll steer the airship, and what I want you to do is to catch the anchor in the rear of their car. Then I'll show you some fun."
Tom followed instructions. Slowly he lowered the rope with the dangling grapple. The airship was also sent down, as the cable was not quite long enough to reach the earth from the height at which they were. The engine was run at slow speed, so that the noise would not attract the attention of the three cronies who were speeding along, all unconscious of the craft in the air over their heads. The Red Cloud was moving in the same direction as was the automobile.
The anchor was now close to the rear of Andy's car. Suddenly it caught on the tonneau and Tom called that fact to Mr. Sharp.
"Fasten the rope at the cleat," directed the balloonist.
Tom did so, and a moment later the aeronaut sent the airship up by turning more gas into the container. At the same time he reversed the engine and the Red Cloud began pulling the touring car backward, also lifting the rear wheels clear from the earth.
A startled cry from the occupants of the machine told Tom and his friend that Andy and his cronies were aware something was wrong. A moment later Andy, looking up, saw the airship hovering in the air above him. Then he saw the rope fast to his auto. The airship was not rising now, or the auto would have been turned over, but it was slowly pulling it backward, in spite of the fact that the motor of the car was still going.
"Here! You let go of me!" cried Andy. "I'll have you arrested if you damage my car."
"Come up here and cut the rope," called Tom leaning over and looking down. He could enjoy the bully's discomfiture. As for Sam and Pete, they were much frightened, and cowered down on the floor of the tonneau.
"Maybe you'll shut me in the tank again and splash mud on me!" shouted Tom.
The rear wheels of the auto were lifted still higher from the ground, as Mr. Sharp turned on a little more gas. Andy was not proof against this.
"Oh! oh!" he cried. "Please let me down, Tom. I'm awful sorry for what I did! I'll never do it again! Please, please let me down! Don't! You'll tip me over!"
He had shut off his motor now, and was frantically clinging to the steering wheel.
"Do you admit that you're a sneak and a coward?" asked Tom, "rubbing it in."
"Yes, yes! Oh, please let me down!"
"Shall we?" asked Tom of Mr. Sharp.
"Yes," replied the balloonist. "We can afford to lose the rope and anchor for the sake of turning the tables. Cut the cable."
Tom saw what was intended. Using a little hatchet, he severed the rope with a single blow. With a crash that could be heard up in the air where the Red Cloud hovered, the rear wheels of the auto dropped to the ground. Then came two loud reports.
"Both tires busted!" commented Mr. Sharp dryly, and Tom, looking down, saw the trio of lads ruefully contemplating the collapsed rubber of the rear wheels. The tables had been effectually turned on Andy Foger. His auto was disabled, and the airship, with a graceful sweep, mounted higher and higher, continuing on its way to the coast.
"Well, I guess they've had their lesson," remarked Tom, as he took an observation through the telescope and saw Andy and his cronies hard at work trying to repair the ruptured tires. "That certainly was a corking good trick."
"Yes," admitted Mr. Sharp modestly. "I once did something similar, only it was a horse and wagon instead of an auto. But let's try for another speed record. The conditions are just right."
They arrived at the coast much sooner than they had dared to hope, the Red Cloud proving herself a veritable wonder.
The remainder of that day, and part of the next, was spent in working on the submarine.
"We'll launch her day after to-morrow," declared Mr. Swift enthusiastically. "Then to see whether my calculations are right or wrong."
"It won't be your fault if it doesn't work," said his son. "You certainly have done your best."
"And so have you and Mr. Sharp and the others, for that matter. Well, I have no doubt but that everything will be all right, Tom."
"There!" exclaimed Mr. Sharp the next morning, as he was adjusting a certain gage. "I knew I'd forget something. That special brand of lubricating oil. I meant to bring it from Shopton, and I didn't."
"Maybe I can get it in Atlantis," suggested Tom, naming the coast city nearest to them. "I'll take a walk over. It isn't far."
"Will you? I'll be glad to have you," resumed the balloonist. "A gallon will be all we'll need."
Tom was soon on his way. He had to walk, as the roads were too poor to permit him to use the motor-cycle, and the airship attracted too much attention to use on a short trip. He was strolling along, when from the other side of a row of sand dunes, that lined the uncertain road to Atlantis, he heard some one speaking. At first the tones were not distinct, but as the lad drew nearer to the voice he heard an exclamation.
"Bless my gold-headed cane! I believe I'm lost. He said it was out this way somewhere, but I don't see anything of it. If I had that Eradicate Sampson here now I'd—bless my shoelaces I don't know what I would do to him."
"Mr. Damon! Mr. Damon!" cried Tom. "Is that you?"
"Me? Of course it's me! Who else would it be?" answered the voice. "But who are you. Why, bless my liver! If it isn't Tom Swift!" he cried. "Oh, but I'm glad to see you! I was afraid I was shipwrecked! Bless my gaiters, how are you, anyhow? How is your father? How is Mr. Sharp, and all the rest of them?"
"Pretty well. And you?"
"Me? Oh, I'm all right; only a trifle nervous. I called at your house in Shopton yesterday, and Eradicate told me, as well as he could, where you were located. I had nothing to do, so I thought I'd take a run down here. But what's this I hear about you? Are you going on a voyage?"
"Yes."
"In the air? May I go along again? I certainly enjoyed my other trip in the Red Cloud. That is, all but the fire and being shot at. May I go?"
"We're going on a different sort of trip this time," said the youth.
"Where?"
"Under water."
"Under water? Bless my sponge bath! You don't mean it!"
"Yes. Dad has completed the submarine he was working on when we were off in the airship, and it will be launched the day after to-morrow."
"Oh, that's so. I'd forgotten about it. He's going to try for the Government prize, isn't he? But tell me more about it. Bless my scarf-pin, but I'm glad I met you! Going into town, I take it. Well, I just came from there, but I'll walk back with you. Do you think—is there any possibility—that I could go with you? Of course, I don't want to crowd you, but—"
"Oh, there'll be plenty of room," replied the young inventor. "In fact, more room than we had in the airship. We were talking only the other day about the possibility of you going with us, but we didn't think you'd risk it."
"Risk it? Bless my liver! Of course I'll risk it! It can't be as bad as sailing in the air. You can't fall, that's certain."
"No; but maybe you can't rise," remarked Tom grimly.
"Oh, we won't think of that. Of course, I'd like to go. I fully expected to be killed in the Red Cloud, but as I wasn't. I'm ready to take a chance in the water. On the whole, I think I prefer to be buried at sea, anyhow. Now, then, will you take me?"
"I think I can safely promise," answered Tom with a smile at his friend's enthusiasm.
The two were approaching the city, having walked along as they talked. There were still some sand dunes near the road, and they kept on the side of these, nearest the beach, where they could watch the breakers.
"But you haven't told me where you are going," went on Mr. Damon, after blessing a few dozen objects. "Where do the Government trials take place?"
"Well," replied the lad, "to be frank with you, we have abandoned our intention of trying for the Government prize."
"Not going to try for it? Bless my slippers! Why not? Isn't fifty thousand dollars worth striving for? And, with the kind of a submarine you say you have, you ought to be able to win."
"Yes, probably we could win," admitted the young inventor, "but we are going to try for a better prize."
"A better one? I don't understand."
"Sunken treasure," explained Tom. "There's a ship sunk off the coast of Uruguay, with three hundred thousand dollars in gold bullion aboard. Dad and I are going to try to recover that in our submarine. We're going to start day after to-morrow, and, if you like, you may go along."
"Go along! Of course I'll go along!" cried the eccentric man. "But I never heard of such a thing. Sunken treasure! Three hundred thousand dollars in gold! My, what a lot of money! And to go after it in a submarine! It's as good as a story!"
"Yes, we hope to recover all the treasure," said the lad. "We ought to be able to claim at least half of it."
"Bless my pocketbook!" cried Mr. Damon, but Tom did not hear him. At that instant his attention was attracted by seeing two men emerge from behind the sand dune near which he and Mr. Damon had halted momentarily, when the youth explained about the treasure. The man looked sharply at Tom. A moment later the first man was joined by another, and at the sight of him our hero could not repress an exclamation of alarm. For the second man was none other than Addison Berg.
The latter glanced quickly at Tom, and then, with a hasty word to his companion, the two swung around and made off in the opposite direction to that in which they had been walking.
"What's the matter?" asked Mr. Damon, seeing the young inventor was strangely affected.
"That—that man," stammered the lad.
"You don't mean to tell me that was one the Happy Harry gang, do you?"
"No. But one, or both of those men, may prove to be worse. That second man was Addison Berg, and he's agent for a firm of submarine boat builders who are rivals of dad's. Berg has been trying to find out why we abandoned our intention of competing for the Government prize."
"I hope you didn't tell him."
"I didn't intend to," replied Tom, smiling grimly, "but I'm afraid I have, however. He certainly overheard what I said. I spoke too loud. Yes, he must have heard me. That's why he hurried off so."
"Possibly no harm is done. You didn't give the location of the sunken ship."
"No; but I guess from what I said it will be easy enough to find. Well, if we're going to have a fight for the possession of that sunken gold, I'm ready for it. The Advance is well equipped for a battle. I must tell dad of this. It's my fault."
"And partly mine, for asking you such leading questions in a public place," declared Mr. Damon. "Bless my coat-tails, but I'm sorry! Maybe, after all, those men were so interested in what they themselves were saying that they didn't understand what you said."
But if there had been any doubts on this score they would have been dissolved had Tom and his friend been able to see the actions of Mr. Berg and his companion a little later. The plans of the treasure-hunters had been revealed to their ears.
While Tom and Mr. Damon continued on to Atlantis after the oil, the young inventor lamenting from time to time that his remarks about the real destination of the Advance had been overheard by Mr. Berg, the latter and his companion were hastening back along the path that ran on one side of the sand dunes.
"What's your hurry?" asked Mr. Maxwell, who was with the submarine agent. "You turned around as if you were shot when you saw that man and the lad. There didn't appear to be any cause for such a hurry. From what I could hear they were talking about a submarine. You're in the same business. You might be friends."
"Yes, we might," admitted Mr. Berg with a peculiar smile; "but, unless I'm very much mistaken, we're going to be rivals."
"Rivals? What do you mean?"
"I can't tell you now. Perhaps I may later. But if you don't mind, walk a little faster, please. I want to get to a long-distance telephone."
"What for?"
"I have just overheard something that I wish to communicate to my employers, Bentley & Eagert."
"Overheard something? I don't see what it could be, unless that lad—"
"You'll learn in good time," went on the submarine agent. "But I must telephone at once."
A little later the two men had reached a trolley line that ran into Atlantis, and they arrived at the city before Mr. Damon and Tom got there, as the latter had to go by a circuitous route. Mr. Berg lost no time in calling up his firm by telephone.
"I have had another talk with Mr. Swift," he reported to Mr. Bentley, who came to the instrument in Philadelphia.
"Well, what does he say?" was the impatient question. "I can't understand his not wanting to try for the Government prize. It is astonishing. You said you were going to discover the reason, Mr. Berg, but you haven't done so."
"I have."
"What is it?"
"Well, the reason Mr. Swift and his son don't care to try for the fifty thousand dollar prize is that they are after one of three hundred thousand dollars."
"Three hundred thousand dollars!" cried Mr. Bentley. "What government is going to offer such a prize as that for submarines, when they are getting almost as common as airships? We ought to have a try for that ourselves. What government is it?"
"No government at all. But I think we ought to have a try for it, Mr. Bentley."
"Explain."
"Well, I have just learned, most accidentally, that the Swifts are going after sunken treasure—three hundred thousand dollars in gold bullion."
"Sunken treasure? Where?
"I don't know exactly, but off the coast of Uruguay," and Mr. Berg rapidly related what he had overheard Tom tell Mr. Damon. Mr. Bentley was much excited and impatient for more details, but his agent could not give them to him.
"Well," concluded the senior member of the firm of submarine boat builders, "if the Swifts are going after treasure, so can we. Come to Philadelphia at once, Mr. Berg, and we'll talk this matter over. There is no time to lose. We can afford to forego the Government prize for the chance of getting a much larger one. We have as much right to search for the sunken gold as the Swifts have. Come here at once, and we will make our plans."
"All right," agreed the agent with a smile as he hung up the receiver. "I guess," he murmured to himself, "that you won't be so high and mighty with me after this, Tom Swift. We'll see who has the best boat, after all. We'll have a contest and a competition, but not for a government prize. It will be for the sunken gold."
It was easy to see that Mr. Berg was much pleased with himself.
Meanwhile, Tom and Mr. Damon had reached Atlantis, and had purchased the oil. They started back, but Tom took a street leading toward the center of the place, instead of striking for the beach path, along which they had come.
"Where are you going?" asked Mr. Damon.
"I want to see if that Andy Foger has come back here," replied the lad, and he told of having been shut in the tank by the bully.
"I've never properly punished him for that trick," he went on, "though we did manage to burst his auto tires. I'm curious to know how he knew enough to turn that gear and shut the tank door. He must have been loitering near the shop, seen me go in the submarine alone, watched his chance and sneaked in after me. But I'd like to get a complete explanation, and if I once got hold of Andy I could make him talk," and Tom clenched his fist in a manner that augured no good for the squint-eyed lad. "He was stopping at the same hotel with Mr. Berg, and he hurried away after the trick he played on me. I next saw him in Shopton, but I thought perhaps he might have come back here. I'm going to inquire at the hotel," he added.
Andy's name was not on the register since his hasty flight, however, and Tom, after inquiring from the clerk and learning that Mr. Berg was still a guest at the hostelry, rejoined Mr. Damon.
"Bless my hat!" exclaimed that eccentric individual as they started back to the lonely beach where the submarine was awaiting her advent into the water. "The more I think of the trip I'm going to take, the more I like it."
"I hope you will," remarked Tom. "It will be a new experience for all of us. There's only one thing worrying me, and that is about Mr. Berg having overheard what I said."
"Oh, don't worry about that. Can't we slip away and leave no trace in the water?"
"I hope so, but I must tell dad and Mr. Sharp about what happened."
The aged inventor was not a little alarmed at what his son related, but he agreed with Mr. Damon, whom he heartily welcomed, that little was to be apprehended from Berg and his employers.
"They know we're after a sunken wreck, but that's all they do know," said Tom's father. "We are only waiting for the arrival of Captain Alden Weston, and then we will go. Even if Bentley & Eagert make a try for the treasure we'll have the start of them, and this will be a case of first come, first served. Don't worry, Tom. I'm glad you're going, Mr. Damon. Come, I will show you our submarine."
As father and son, with their guest, were going to the machine shop, Mr. Sharp met them. He had a letter in his hand.
"Good news!" the balloonist cried. "Captain Weston will be with us to-morrow. He will arrive at the Beach Hotel in Atlantis, and wants one of us to meet him there. He has considerable information about the wreck."
"The Beach Hotel," murmured Tom. "That is where Mr. Berg is stopping. I hope he doesn't worm any of our secret from Captain Weston," and it was with a feeling of uneasiness that the young inventor continued after his father and Mr. Damon to where the submarine was.