Chapter III: Part 3

The young inventor blushed at his indiscretion. He felt that the news of the search for the treasure had leaked out through him, though he was the one to get on the trail of it by seeing the article in the paper. Now he had nearly been guilty of another break. He realized that he must be more cautious. The captain saw his confusion, and said:

"I know how it is. You're eager to get under way. I don't blame you. I was the same myself when I was your age. But we'll soon be at your place, and then I'll tell you all I know. Sufficient now, to say that I believe I have located the wreck within a few miles. I got on the track of a sailor who had met one of the shipwrecked crew of the Boldero, and he gave me valuable information. Now tell me about the craft we are going in. A good deal depends on that."

Tom hardly knew what to answer. He recalled what Mr. Sharp had said about not wanting to tell Captain Weston, until the last moment, that they were going in a submarine, for fear the old seaman (for he was old in point of service though not in years) might not care to risk an under-water trip. Therefore Tom hesitated. Seeing it, Captain Weston remarked quietly:

"I mean, what type is your submarine? Does it go by compressed air, or water power?"

"How do you know it's a submarine?" asked the young inventor quickly, and in some confusion.

"Easy enough. When Mr. Berg thought he was pumping me, I was getting a lot of information from him. He told me about the submarine his firm was building, and, naturally, he mentioned yours. One thing led to another until I got a pretty good idea of your craft. What do you call it?"

"The Advance."

"Good name. I like it, if you don't mind speaking of it."

"We were afraid you wouldn't like it," commented Tom.

"What, the name?"

"No, the idea of going in a submarine."

"Oh," and Captain Weston laughed. "Well, it takes more than that to frighten me, if you'll excuse the expression. I've always had a hankering to go under the surface, after so many years spent on top. Once or twice I came near going under, whether I wanted to or not, in wrecks, but I think I prefer your way. Now, if you're all done, and don't mind me speaking of it, I think we'll start for your place. We must hustle, for Berg may yet get on our trail, even if he has got the wrong route," and he laughed again.

It was no small relief to Mr Swift and Mr. Sharp to learn that Captain Weston had no objections to a submarine, as they feared he might have. The captain, in his diffident manner, made friends at once with the treasure-hunters, and he and Mr. Damon struck up quite an acquaintance. Tom told of his meeting with the seaman, and the latter related, with much gusto, the story of how he had fooled Mr. Berg.

"Well, perhaps you'd like to come and take a look at the craft that is to be our home while we're beneath the water," suggested Mr. Swift and the sailor assenting, the aged inventor, with much pride, assisted by Tom, pointed out on the Advance the features of interest. Captain Weston gave hearty approval, making one or two minor suggestions, which were carried out.

"And so you launch her to-morrow," he concluded, when he had completed the inspection "Well, I hope it's a success, if I may be permitted to say so."

There were busy times around the machine shop next day. So much secrecy had been maintained that none of the residents, or visitors to the coast resort, were aware that in their midst was such a wonderful craft as the submarine. The last touches were put on the under-water ship; the ways, leading from the shop to the creek, were well greased, and all was in readiness for the launching. The tide would soon be at flood, and then the boat would slide down the timbers (at least, that was the hope of all), and would float in the element meant to receive her. It was decided that no one should be aboard when the launching took place, as there was an element of risk attached, since it was not known just how buoyant the craft was. It was expected she would float, until the filled tanks took her to the bottom, but there was no telling.

"It will be flood tide now in ten minutes," remarked Captain Weston quietly, looking at his watch. Then he took an observation through the telescope. "No hostile ships hanging in the offing," he reported. "All is favorable, if you don't mind me saying so," and he seemed afraid lest his remark might give offense.

"Get ready," ordered Mr. Swift. "Tom, see that the ropes are all clear," for it had been decided to ease the Advance down into the water by means of strong cables and windlasses, as the creek was so narrow that the submarine, if launched in the usual way, would poke her nose into the opposite mud bank and stick there.

"All clear," reported the young inventor.

"High tide!" exclaimed the captain a moment later, snapping shut his watch.

"Let go!" ordered Mr. Swift, and the various windlasses manned by the inventor, Tom and the others began to unwind their ropes. Slowly the ship slid along the greased ways. Slowly she approached the water. How anxiously they all watched her! Nearer and nearer her blunt nose, with the electric propulsion plate and the auxiliary propeller, came to the creek, the waters of which were quiet now, awaiting the turn of the tide.

Now little waves lapped the steel sides. It was the first contact of the Advance with her native element.

"Pay out the rope faster!" cried Mr. Swift.

The windlasses were turned more quickly. Foot by foot the craft slid along until, with a final rush, the stern left the ways and the submarine was afloat. Now would come the test. Would she ride on an even keel, or sink out of sight, or turn turtle? They all ran to the water's edge, Tom in the lead.

"Hurrah!" suddenly yelled the lad, trying to stand on his head. "She floats! She's a success! Come on! Let's get aboard!"

For, true enough, the Advance was riding like a duck on the water. She had been proportioned just right, and her lines were perfect. She rode as majestically as did any ship destined to sail on the surface, and not intended to do double duty.

"Come on, we must moor her to the pier," directed Mr. Sharp. "The tide will turn in a few minutes and take her out to sea."

He and Tom entered a small boat, and soon the submarine was tied to a small dock that had been built for the purpose.

"Now to try the engine," suggested Mr. Swift, who was almost trembling with eagerness; for the completion of the ship meant much to him.

"One moment," begged Captain Weston. "If you don't mind, I'll take an observation," he went on, and he swept the horizon with his telescope. "All clear," he reported. "I think we may go aboard and make a trial trip."

Little time was lost in entering the cabin and engine-room, Garret Jackson accompanying the party to aid with the machinery. It did not take long to start the motors, dynamos and the big gasolene engine that was the vital part of the craft. A little water was admitted to the tanks for ballast, since the food and other supplies were not yet on board. The Advance now floated with the deck aft of the conning tower showing about two feet above the surface of the creek. Mr. Swift and Tom entered the pilot house.

"Start the engines," ordered the aged inventor, "and we'll try my new system of positive and negative electrical propulsion."

There was a hum and whir in the body of the ship beneath the feet of Tom and his father. Captain Weston stood on the little deck near the conning tower.

"All ready?" asked the youth through the speaking tube to Mr. Sharp and Mr. Jackson in the engine-room.

"All ready," came the answer.

Tom threw over the connecting lever, while his father grasped the steering wheel. The Advance shot forward, moving swiftly along, about half submerged.

"She goes! She goes!" cried Tom.

"She certainly does, if I may be permitted to say so," was the calm contribution of Captain Weston. "I congratulate you."

Faster and faster went the new craft. Mr. Swift headed her toward the open sea, but stopped just before passing out of the creek, as he was not yet ready to venture into deep water.

"I want to test the auxiliary propellers," he said. After a little longer trial of the electric propulsion plates, which were found to work satisfactorily, sending the submarine up and down the creek at a fast rate, the screws, such as are used on most submarines, were put into gear. They did well, but were not equal to the plates, nor was so much expected of them.

"I am perfectly satisfied," announced Mr. Swift as he once more headed the boat to sea. "I think, Captain Weston, you had better go below now."

"Why so?"

"Because I am going to completely submerge the craft. Tom, close the conning tower door. Perhaps you will come in here with us, Captain Weston, though it will be rather a tight fit."

"Thank you, I will. I want to see how it feels to be in a pilot house under water."

Tom closed the water-tight door of the conning tower. Word was sent through the tube to the engine-room that a more severe test of the ship was about to be made. The craft was now outside the line of breakers and in the open sea.

"Is everything ready, Tom?" asked his father in a quiet voice.

"Everything," replied the lad nervously, for the anticipation of being about to sink below the surface was telling on them all, even on the calm, old sea captain.

"Then open the tanks and admit the water," ordered Mr. Swift.

His son turned a valve and adjusted some levers. There was a hissing sound, and the Advance began sinking. She was about to dive beneath the surface of the ocean, and those aboard her were destined to go through a terrible experience before she rose again.

Chapter Eleven

On the Ocean Bed

Lower and lower sank the submarine. There was a swirling and foaming of the water as she went down, caused by the air bubbles which the craft carried with her in her descent. Only the top of the conning tower was out of water now, the ocean having closed over the deck and the rounded back of the boat. Had any one been watching they would have imagined that an accident was taking place.

In the pilot house, with its thick glass windows, Tom, his father and Captain Weston looked over the surface of the ocean, which every minute was coming nearer and nearer to them.

"We'll be all under in a few seconds," spoke Tom in a solemn voice, as he listened to the water hissing into the tanks.

"Yes, and then we can see what sort of progress we will make," added Mr. Swift. "Everything is going fine, though," he went on cheerfully. "I believe I have a good boat."

"There is no doubt of it in my mind," remarked Captain Weston, and Tom felt a little disappointed that the sailor did not shout out some such expression as "Shiver my timbers!" or "Keel-haul the main braces, there, you lubber!" But Captain Weston was not that kind of a sailor, though his usually quiet demeanor could be quickly dropped on necessity, as Tom learned later.

A few minutes more and the waters closed over the top of the conning tower. The Advance was completely submerged. Through the thick glass windows of the pilot house the occupants looked out into the greenish water that swirled about them; but it could not enter. Then, as the boat went lower, the light from above gradually died out, and the semi-darkness gave place to gloom.

"Turn on the electrics and the searchlight, Tom," directed his father.

There was the click of a switch, and the conning tower was flooded with light. But as this had the effect of preventing the three from peering out into the water, just as one in a lighted room cannot look out into the night, Tom shut them off and switched on the great searchlight. This projected its powerful beams straight ahead and there, under the ocean, was a pathway of illumination for the treasure-seekers.

"Fine!" cried Captain Weston, with more enthusiasm than he had yet manifested. "That's great, if you don't mind me mentioning it. How deep are we?"

Tom glanced at a gage on the side of the pilot tower.

"Only about sixty feet," he answered.

"Then don't go any deeper!" cried the captain hastily. "I know these waters around here, and that's about all the depth you've got. You'll be on the bottom in a minute."

"I intend to get on the bottom after a while," said Mr. Swift, "but not here. I want to try for a greater distance under water before I come to rest on the ocean's bed. But I think we are deep enough for a test. Tom, close the tank intake pipes and we'll see how the Advance will progress when fully submerged."

The hissing stopped, and then, wishing to see how the motors and other machinery would work, the aged inventor and his son, accompanied by Captain Weston, descended from the conning tower, by means of an inner stairway, to the interior of the ship. The submarine could be steered and managed from below or above. She was now floating about sixty-five feet below the surface of the bay.

"Well, how do you like it?" asked Tom of Mr. Damon, as he saw his friend in an easy chair in the living-room or main cabin of the craft, looking out of one of the plate-glass windows on the side.

"Bless my spectacles, it's the most wonderful thing I ever dreamed of!" cried the queer character, as he peered at the mass of water before him. "To think that I'm away down under the surface, and yet as dry as a bone. Bless my necktie, but it's great! What are we going to do now?"

"Go forward," replied the young inventor.

"Perhaps I had better make an observation," suggested Captain Weston, taking his telescope from under his arm, where he had carried it since entering the craft, and opening it. "We may run afoul of something, if you don't mind me mentioning such a disagreeable subject." Then, as he thought of the impossibility of using his glass under water, he closed it.

"I shall have little use for this here, I'm afraid," he remarked with a smile. "Well, there's some consolation. We're not likely to meet many ships in this part of the ocean. Other vessels are fond enough of remaining on the surface. I fancy we shall have the depths to ourselves, unless we meet a Government submarine, and they are hardly able to go as deep as we can. No, I guess we won't run into anything and I can put this glass away."

"Unless we run into Berg and his crowd," suggested Tom in a low voice.

"Ha! ha!" laughed Captain Weston, for he did not want Mr. Swift to worry over the unscrupulous agent. "No, I don't believe we'll meet them, Tom. I guess Berg is trying to work out the longitude and latitude I gave him. I wish I could see his face when he realizes that he's been deceived by that fake map."

"Well, I hope he doesn't discover it too soon and trail us," went on the lad. "But they're going to start the machinery now. I suppose you and I had better take charge of the steering of the craft. Dad will want to be in the engine-room."

"All right," replied the captain, and he moved forward with the lad to a small compartment, shut off from the living-room, that served as a pilot house when the conning tower was not used. The same levers, wheels and valves were there as up above, and the submarine could be managed as well from there as from the other place.

"Is everything all right?" asked Mr Swift as he went into the engine-room, where Garret Jackson and Mr. Sharp were busy with oil cans.

"Everything," replied the balloonist. "Are you going to start now?"

"Yes, we're deep enough for a speed trial. We'll go out to sea, however, and try for a lower depth record, as soon as there's enough water. Start the engine."

A moment later the powerful electric currents were flowing into the forward and aft plates, and the Advance began to gather way, forging through the water.

"Straight ahead, out to sea, Tom," called his father to him.

"Aye, aye, sir," responded the youth.

"Ha! Quite seaman-like, if you don't mind a reference to it," commented Captain Weston with a smile. "Mind your helm, boy, for you don't want to poke her nose into a mud bank, or run up on a shoal."

"Suppose you steer?" suggested the lad. "I'd rather take lessons for a while."

"All right. Perhaps it will be safer. I know these waters from the top, though I can't say as much for the bottom. However, I know where the shoals are."

The powerful searchlight was turned, so as to send its beams along the path which the submarine was to follow, and then, as she gathered speed, she shot ahead, gliding through the waters like a fish.

Mr. Damon divided his time between the forward pilot-room, the living-apartment, and the place where Mr. Swift, Garret Jackson and Mr. Sharp were working over the engines. Every few minutes he would bless some part of himself, his clothing, or the ship. Finally the old man settled down to look through the plate-glass windows in the main apartment.

On and on went the submarine. She behaved perfectly, and was under excellent control. Some times Tom, at the request of his father, would send her toward the surface by means of the deflecting rudder. Then she would dive to the bottom again. Once, as a test, she was sent obliquely to the surface, her tower just emerging, and then she darted downward again, like a porpoise that had come up to roll over, and suddenly concluded to seek the depths. In fact, had any one seen the maneuver they would have imagined the craft was a big fish disporting itself.

Captain Weston remained at Tom's side, giving him instructions, and watching the compass in order to direct the steering so as to avoid collisions. For an hour or more the craft was sent almost straight ahead at medium speed. Then Mr. Swift, joining his son and the captain, remarked:

"How about depth of water here, Captain Weston?"

"You've got more than a mile."

"Good! Then I'm going down to the bottom of the sea! Tom, fill the tanks still more.

"Aye, aye, sir," answered the lad gaily. "Now for a new experience!"

"And use the deflecting rudder, also," advised his father. "That will hasten matters."

Five minutes later there was a slight jar noticeable.

"Bless my soul! What's that?" cried Mr. Damon. "Have we hit something?"

"Yes," answered Tom with a smile.

"What, for gracious sake?"

"The bottom of the sea. We're on the bed of the ocean."

Chapter Twelve

For a Breath of Air

They could hardly realize it, yet the depth-gage told the story. It registered a distance below the surface of the ocean of five thousand seven hundred feet--a little over a mile. The Advance had actually come to rest on the bottom of the Atlantic.

"Hurrah!" cried Tom. "Let's get on the diving suits, dad, and walk about on land under water for a change."

"No," said Mr. Swift soberly. "We will hardly have time for that now. Besides, the suits are not yet fitted with the automatic air-tanks, and we can't use them. There are still some things to do before we start on our treasure cruise. But I want to see how the plates are standing this pressure."

The Advance was made with a triple hull, the spaces between the layers of plates being filled with a secret material, capable of withstanding enormous pressure, as were also the plates themselves. Mr. Swift, aided by Mr. Jackson and Captain Weston, made a thorough examination, and found that not a drop of water had leaked in, nor was there the least sign that any of the plates had given way under the terrific strain.

"She's as tight as a drum, if you will allow me to make that comparison," remarked Captain Weston modestly. "I couldn't ask for a dryer ship."

"Well, let's take a look around by means the searchlight and the observation windows, and then we'll go back," suggested Mr. Swift. "It will take about two days to get the stores and provisions aboard and rig up the diving suits; then we will start for the sunken treasure."

There were several powerful searchlights on the Advance, so arranged that the bow, stern or either side could be illuminated independently. There were also observation windows near each light.

In turn the powerful rays were cast first at the bow and then aft. In the gleams could be seen the sandy bed of the ocean, covered with shells of various kinds. Great crabs walked around on their long, jointed legs, and Tom saw some lobsters that would have brought joy to the heart of a fisherman.

"Look at the big fish!" cried Mr. Damon suddenly, and he pointed to some dark, shadowy forms that swam up to the glass windows, evidently puzzled by the light.

"Porpoises," declared Captain Weston briefly, "a whole school of them."

The fish seemed suddenly to multiply, and soon those in the submarine felt curious tremors running through the whole craft.

"The fish are rubbing up against it," cried Tom. "They must think we came down here to allow them to scratch their backs on the steel plates."

For some time they remained on the bottom, watching the wonderful sight of the fishes that swam all about them.

"Well, I think we may as well rise," announced Mr. Swift, after they had been on the bottom about an hour, moving here and there. "We didn't bring any provisions, and I'm getting hungry, though I don't know how the others of you feel about it."

"Bless my dinner-plate, I could eat, too!" cried Mr. Damon. "Go up, by all means. We'll get enough of under-water travel once we start for the treasure."

"Send her up, Tom," called his father. "I want to make a few notes on some needed changes and improvements."

Tom entered the lower pilot house, and turned the valve that opened the tanks. He also pulled the lever that started the pumps, so that the water ballast would be more quickly emptied, as that would render the submarine buoyant, and she would quickly shoot to the surface. To the surprise of the lad, however, there followed no outrushing of the water. The Advance remained stationary on the ocean bed. Mr. Swift looked up from his notes.

"Didn't you hear me ask you to send her up, Tom?" he inquired mildly.

"I did, dad, but something seems to be the matter," was the reply.

"Matter? What do you mean?" and the aged inventor hastened to where his son and Captain Weston were at the wheels, valves and levers.

"Why, the tanks won't empty, and the pumps don't seem to work."

"Let me try," suggested Mr. Swift, and he pulled the various handles. There was no corresponding action of the machinery.

"That's odd," he remarked in a curious voice "Perhaps something has gone wrong with the connections. Go look in the engine-room, and ask Mr. Sharp if everything is all right there."

Tom made a quick trip, returning to report that the dynamos, motors and gas engine were running perfectly.

"Try to work the tank levers and pumps from the conning tower," suggested Captain Weston. "Sometimes I've known the steam steering gear to play tricks like that."

Tom hurried up the circular stairway into the tower. He pulled the levers and shifted the valves and wheels there. But there was no emptying of the water tanks. The weight and pressure of water in them still held the submarine on the bottom of the sea, more than a mile from the surface. The pumps in the engine-room were working at top speed, but there was evidently something wrong in the connections. Mr. Swift quickly came to this conclusion.

"We must repair it at once," he said. "Tom, come to the engine-room. You and I, with Mr. Jackson and Mr. Sharp, will soon have it in shape again."

"Is there any danger?" asked Mr. Damon in a perturbed voice. "Bless my soul, it's unlucky to have an accident on our trial trip."

"Oh, we must expect accidents," declared Mr. Swift with a smile. "This is nothing."

But it proved to be more difficult than he had imagined to re-establish the connection between the pumps and the tanks. The valves, too, had clogged or jammed, and as the pressure outside the ship was so great, the water would not run out of itself. It must be forced.

For an hour or more the inventor, his son and the others, worked away. They could accomplish nothing. Tom looked anxiously at his parent when the latter paused in his efforts.

"Don't worry," advised the aged inventor. "It's got to come right sooner or later."

Just then Mr. Damon, who had been wandering about the ship, entered the engine-room.

"Do you know," he said, "you ought to open a window, or something."

"Why, what's the matter?" asked Tom quickly, looking to see if the odd man was joking.

"Well, of course I don't exactly mean a window," explained Mr. Damon, "but we need fresh air."

"Fresh air!" There was a startled note in Mr. Swift's voice as he repeated the words.

"Yes, I can hardly breathe in the living-room, and it's not much better here."

"Why, there ought to be plenty of fresh air," went on the inventor. "It is renewed automatically."

Tom jumped up and looked at an indicator. He uttered a startled cry.

"The air hasn't been changed in the last hour!" he exclaimed. "It is bad. There's not enough oxygen in it. I notice it, now that I've stopped working. The gage indicates it, too. The automatic air-changer must have stopped working. I'll fix it."

He hurried to the machine which was depended on to supply fresh air to the submarine.

"Why, the air tanks are empty!" the young inventor cried. "We haven't any more air except what is in the ship now!"

"And we're rapidly breathing that up," added Captain Weston solemnly.

"Can't you make more?" cried Mr. Damon. "I thought you said you could make oxygen aboard the ship."

"We can," answered Mr. Swift, "but I did not bring along a supply of the necessary chemicals. I did not think we would be submerged long enough for that. But there should have been enough in the reserve tank to last several days. How about it, Tom?"

"It's all leaked out, or else it wasn't filled," was the despairing answer. "All the air we have is what's in the ship, and we can't make more."

The treasure-seekers looked at each other. It was an awful situation.

"Then the only thing to do is to fix the machinery and rise to the surface," said Mr. Sharp simply. "We can have all the air we want, then."

"Yes, but the machinery doesn't seem possible of being fixed," spoke Tom in a low voice.

"We must do it!" cried his father.

They set to work again with fierce energy, laboring for their very lives. They all knew that they could not long remain in the ship without oxygen. Nor could they desert it to go to the surface, for the moment they left the protection of the thick steel sides the terrible pressure of the water would kill them. Nor were the diving suits available. They must stay in the craft and die a miserable death--unless the machinery could be repaired and the Advance sent to the surface. The emergency expanding lifting tank was not yet in working order.

More frantically they toiled, trying every device that was suggested to the mechanical minds of Tom, his father, Mr. Sharp or Mr. Jackson, to make the pumps work. But something was wrong. More and more foul grew the air. They were fairly gasping now. It was difficult to breathe, to say nothing of working, in that atmosphere. The thought of their terrible position was in the minds of all.

"Oh, for one breath of fresh air!" cried Mr. Damon, who seemed to suffer more than any of the others. Grim death was hovering around them, imprisoned as they were on the ocean's bed, over a mile from the surface.

Chapter Thirteen

Off for the Treasure

Suddenly Tom, after a moment's pause, seized a wrench and began loosening some nuts.

"What are you doing?" asked his father faintly, for he was being weakened by the vitiated atmosphere.

"I'm going to take this valve apart," replied his son. "We haven't looked there for the trouble. Maybe it's out of order."

He attacked the valve with energy, but his hands soon lagged. The lack of oxygen was telling on him. He could no longer work quickly.

"I'll help," murmured Mr. Sharp thickly. He took a wrench, but no sooner had he loosened one nut than he toppled over. "I'm all in," he murmured feebly.

"Is he dead?" cried Mr. Damon, himself gasping.

"No, only fainted. But he soon will be dead, and so will all of us, if we don't get fresh air," remarked Captain Weston. "Lie down on the floor, every one. There is a little fairly good air there. It's heavier than the air we've breathed, and we can exist on it for a little longer. Poor Sharp was so used to breathing the rarified air of high altitudes that he can't stand this heavy atmosphere."

Mr. Damon was gasping worse than ever, and so was Mr. Swift. The balloonist lay an inert heap on the floor, with Captain Weston trying to force a few drops of stimulant down his throat.

With a fierce determination in his heart, but with fingers that almost refused to do his bidding, Tom once more sought to open the big valve. He felt sure the trouble was located there, as they had tried to locate it in every other place without avail.

"I'll help," said Mr. Jackson in a whisper. He, too, was hardly able to move.

More and more devoid of oxygen grew the air. It gave Tom a sense as if his head was filled, and ready to burst with every breath he drew. Still he struggled to loosen the nuts. There were but four more now, and he took off three while Mr. Jackson removed one. The young inventor lifted off the valve cover, though it felt like a ton weight to him. He gave a glance inside.

"Here's the trouble!" he murmured. "The valve's clogged. No wonder it wouldn't work. The pumps couldn't force the water out."

It was the work of only a minute to adjust the valve. Then Tom and the engineer managed to get the cover back on.

How they inserted the bolts and screwed the nuts in place they never could remember clearly afterward, but they managed it somehow, with shaking, trembling hands and eyes that grew more and more dim.

"Now start the pumps!" cried Tom faintly. "The tanks will be emptied, and we can get to the surface."

Mr. Sharp was still unconscious, nor was Mr. Swift able to help. He lay with his eyes closed. Garret Jackson, however, managed to crawl to the engine-room, and soon the clank of machinery told Tom that the pumps were in motion. The lad staggered to the pilot house and threw the levers over. An instant later there was the hissing of water as it rushed from the ballast tanks. The submarine shivered, as though disliking to leave the bottom of the sea, and then slowly rose. As the pumps worked more rapidly, and the sea was sent from the tank in great volumes, the boat fairly shot to the surface. Tom was ready to open the conning tower and let in fresh air as soon as the top was above the surface.

With a bound the Advance reached the top. Tom frantically worked the worm gear that opened the tower. In rushed the fresh, life-giving air, and the treasure-hunters filled their lungs with it.

And it was only just in time, for Mr. Sharp was almost gone. He quickly revived, as did the others, when they could breathe as much as they wished of the glorious oxygen.

"That was a close call," commented Mr. Swift. "We'll not go below again until I have provided for all emergencies. I should have seen to the air tanks and the expanding one before going below. We'll sail home on the surface now."

The submarine was put about and headed for her dock. On the way she passed a small steamer, and the passengers looked down in wonder at the strange craft.

When the Advance reached the secluded creek where she had been launched, her passengers had fully recovered from their terrible experience, though the nerves of Mr. Swift and Mr. Damon were not at ease for some days thereafter.

"I should never have made a submerged test without making sure that we had a reserve supply of air," remarked the aged inventor. "I will not be caught that way again. But I can't understand how the pump valve got out of order."

"Maybe some one tampered with it," suggested Mr. Damon. "Could Andy Foger, any of the Happy Harry gang, or the rival gold-seekers have done it?"

"I hardly think so," answered Tom. "The place has been too carefully guarded since Berg and Andy once sneaked in. I think it was just an accident, but I have thought of a plan whereby such accidents can be avoided in the future. It needs a simple device."

"Better patent it," suggested Mr. Sharp with a smile.

"Maybe I will," replied the young inventor. "But not now. We haven't time, if we intend to get fitted out for our trip."

"No; I should say the sooner we started the better," remarked Captain Weston. "That is, if you don't mind me speaking about it," he added gently, and the others smiled, for his diffident comments were only a matter of habit.

The first act of the adventurers, after tying the submarine at the dock, was to proceed with the loading of the food and supplies. Tom and Mr. Damon looked to this, while Mr. Swift and Mr. Sharp made some necessary changes to the machinery. The next day the young inventor attached his device to the pump valve, and the loading of the craft was continued.

All was in readiness for the gold-seeking expedition a week later. Captain Weston had carefully charted the route they were to follow, and it was decided to move along on the surface for the first day, so as to get well out to sea before submerging the craft. Then it would sink below the surface, and run along under the water until the wreck was reached, rising at times, as needed, to renew the air supply.

With sufficient stores and provisions aboard to last several months, if necessary, though they did not expect to be gone more than sixty days at most, the adventurers arose early one morning and went down to the dock. Mr. Jackson was not to accompany them. He did not care about a submarine trip, he said, and Mr. Swift desired him to remain at the seaside cottage and guard the shops, which contained much valuable machinery. The airship was also left there.

"Well, are we all ready?" asked Mr. Swift of the little party of gold-seekers, as they were about to enter the conning tower hatchway of the submarine.

"All ready, dad," responded his son.

"Then let's get aboard," proposed Captain Weston. "But first let me take an observation."

He swept the horizon with his telescope, and Tom noticed that the sailor kept it fixed on one particular spot for some time.

"Did you see anything?" asked the lad.

"Well, there is a boat lying off there," was the answer. "And some one is observing us through a glass. But I don't believe it matters. Probably they're only trying to see what sort of an odd fish we are."

"All aboard, then," ordered Mr. Swift, and they went into the submarine. Tom and his father, with Captain Weston, remained in the conning tower. The signal was given, the electricity flowed into the forward and aft plates, and the Advance shot ahead on the surface.

The sailor raised his telescope once more and peered through a window in the tower. He uttered an exclamation.

"What's the matter?" asked Tom.

"That other ship--a small steamer--is weighing anchor and seems to be heading this way," was the reply.

"Maybe it's some one hired by Berg to follow us and trace our movements," suggested Tom.

"If it is we'll fool them," added his father. "Just keep an eye on them, captain, and I think we can show them a trick or two in a few minutes."

Faster shot the Advance through the water. She had started on her way to get the gold from the sunken wreck, but already enemies were on the trail of the adventurers, for the ship the sailor had noticed was steaming after them.

Chapter Fourteen

In the Diving Suits

There was no doubt that the steamer was coming after the submarine. Several observations Captain Weston made confirmed this, and he reported the fact to Mr. Swift.

"Well, we'll change our plans, then," said the inventor. "Instead of sailing on the surface we'll go below. But first let them get near so they may have the benefit of seeing what we do. Tom, go below, please, and tell Mr. Sharp to get every thing in readiness for a quick descent. We'll slow up a bit now, and let them get nearer to us."

The speed of the submarine was reduced, and in a short time the strange steamer had overhauled her, coming to within hailing distance.

Mr. Swift signaled for the machinery to stop and the submarine came to a halt on the surface, bobbing about like a half-submerged bottle. The inventor opened a bull's-eye in the tower, and called to a man on the bridge of the steamer:

"What are you following us for?"

"Following you?" repeated the man, for the strange vessel had also come to a stop. "We're not following you."

"It looks like it," replied Mr. Swift. "You'd better give it up."

"I guess the waters are free," was the quick retort. "We'll follow you if we like."

"Will you? Then come on!" cried the inventor as he quickly closed the heavy glass window and pulled a lever. An instant later the submarine began to sink, and Mr. Swift could not help laughing as, just before the tower went under water, he had a glimpse of the astonished face of the man on the bridge. The latter had evidently not expected such a move as that.

Lower and lower in the water went the craft, until it was about two hundred feet below the surface. Then Mr. Swift left the conning tower, descended to the main part of the ship, and asked Tom and Captain Weston to take charge of the pilot house.

"Send her ahead, Tom," his father said. "That fellow up above is rubbing his eyes yet, wondering where we are, I suppose."

Forward shot the Advance under water, the powerful electrical plates pulling and pushing her on the way to secure the sunken gold.

All that morning a fairly moderate rate of speed was maintained, as it was thought best not to run the new machinery too fast.

Dinner was eaten about a quarter of a mile below the surface, but no one inside the submarine would ever have known it. Electric lights made the place as brilliant as could be desired, and the food, which Tom and Mr. Damon prepared, was equal to any that could have been served on land. After the meal they opened the shutters over the windows in the sides of the craft, and looked at the myriads of fishes swimming past, as the creatures were disclosed in the glare of the searchlight.

That night they were several hundred miles on their journey, for the craft was speedy, and leaving Tom and Captain Weston to take the first watch, the others went to bed.

"Bless my soul, but it does seem odd, though, to go to bed under water, like a fish," remarked Mr. Damon. "If my wife knew this she would worry to death. She thinks I'm off automobiling. But this isn't half as dangerous as riding in a car that's always getting out of order. A submarine for mine, every time."

"Wait until we get to the end of this trip," advised Tom. "I guess you'll find almost as many things can happen in a submarine as can in an auto," and future events were to prove the young inventor to be right.

Everything worked well that night, and the ship made good progress. They rose to the surface the next morning to make sure of their position, and to get fresh air, though they did not really need the latter, as the reserve supply had not been drawn on, and was sufficient for several days, now that the oxygen machine had been put in running order.

On the second day the ship was sent to the bottom and halted there, as Mr. Swift wished to try the new diving suits. These were made of a new, light, but very strong metal to withstand the pressure of a great depth.

Tom, Mr. Sharp and Captain Weston donned the suits, the others agreeing to wait until they saw how the first trial resulted. Then, too, it was necessary for some one acquainted with the machinery to remain in the ship to operate the door and water chamber through which the divers had to pass to get out.

The usual plan, with some changes, was followed in letting the three out of the boat, and on to the bottom of the sea. They entered a chamber in the side of the submarine, water was gradually admitted until it equaled in pressure that outside, then an outer door was opened by means of levers, and they could step out.

It was a curious sensation to Tom and the others to feel that they were actually walking along the bed of the ocean. All around them was the water, and as they turned on the small electric lights in their helmets, which lights were fed by storage batteries fastened to the diving suits, they saw the fish, big and little, swarm up to them, doubtless astonished at the odd creatures which had entered their domain. On the sand of the bottom, and in and out among the shells and rocks, crawled great spider crabs, big eels and other odd creatures seldom seen on the surface of the water. The three divers found no difficulty in breathing, as there were air tanks fastened to their shoulders, and a constant supply of oxygen was fed through pipes into the helmets. The pressure of water did not bother them, and after the first sensation Tom began to enjoy the novelty of it. At first the inability to speak to his companions seemed odd, but he soon got so he could make signs and motions, and be understood.

They walked about for some time, and once the lad came upon a part of a wrecked vessel buried deep in the sand. There was no telling what ship it was, nor how long it had been there, and after silently viewing it, they continued on.

"It was great!" were the first words Tom uttered when he and the others were once more inside the submarine and had removed the suits. "If we can only walk around the wreck of the Boldero that way, we'll have all the gold out of her in no time. There are no life-lines nor air-hose to bother with in these diving suits."

"They certainly are a success," conceded Mr. Sharp.

"Bless my topknot!" cried Mr. Damon. "I'll try it next time. I've always wanted to be a diver, and now I have the chance."

The trip was resumed after the diving chamber had been closed, and on the third day Captain Weston announced, after a look at his chart, that they were nearing the Bahama Islands.

"We'll have to be careful not to run into any of the small keys," he said, that being the name for the many little points of land, hardly large enough to be dignified by the name of island. "We must keep a constant lookout."

Fortune favored them, though once, when Tom was steering, he narrowly avoided ramming a coral reef with the submarine. The searchlight showed it to him just in time, and he sheered off with a thumping in his heart.

The course was changed from south to east, so as to get ready to swing out of the way of the big shoulder of South America where Brazil takes up so much room, and as they went farther and farther toward the equator, they noticed that the waters teemed more and more with fish, some beautiful, some ugly and fear-inspiring, and some such monsters that it made one shudder to look at them, even through the thick glass of the bulls-eye windows.

Chapter Fifteen

At the Tropical Island

It was on the evening of the fourth day later that Captain Weston, who was steering the craft, suddenly called out:

"Land ho!"

"Where away?" inquired Tom quickly, for he had read that this was the proper response to make.

"Dead ahead," answered the sailor with a smile. "Shall we make for it, if I may be allowed the question?"

"What land is it likely to be?" Mr. Swift wanted to know.

"Oh, some small tropical island," replied the seafaring man. "It isn't down on the charts. Probably it's too small to note. I should say it was a coral island, but we may be able to find a spring of fresh water there, and some fruit."

"Then we'll land there," decided the inventor. "We can use some fresh water, though our distilling and ice apparatus does very well."

They made the island just at dusk, and anchored in a little lagoon, where there was a good depth of water.

"Now for shore!" cried Tom, as the submarine swung around on the chain. "It looks like a fine place. I hope there are cocoanuts and oranges here. Shall I get out the electric launch, dad?"

"Yes, you may, and we'll all go ashore. It will do us good to stretch our legs a bit."

Carried in a sort of pocket on the deck of the submarine was a small electric boat, capable of holding six. It could be slid from the pocket, or depression, into the water without the use of davits, and, with Mr. Sharp to aid him, Tom soon had the little craft afloat. The batteries were already charged, and just as the sun was going down the gold-seekers entered the launch and were soon on shore.

They found a good spring of water close at hand, and Tom's wish regarding the cocoanuts was realized, though there were no oranges. The lad took several of the delicious nuts, and breaking them open poured the milk into a collapsible cup he carried, drinking it eagerly. The others followed his example, and pronounced it the best beverage they had tasted in a long time.

The island was a typical tropical one, not very large, and it did not appear to have been often visited by man. There were no animals to be seen, but myriads of birds flew here and there amid the trees, the trailing vines and streamers of moss.

"Let's spend a day here to-morrow and explore it," proposed Tom, and his father nodded an assent. They went back to the submarine as night was beginning to gather, and in the cabin, after supper, talked over the happenings of their trip so far.

"Do you think we'll have any trouble getting the gold out of the wrecked vessel?" asked Tom of Captain Weston, after a pause.

"Well, it's hard to say. I couldn't learn just how the wreck lays, whether it's on a sandy or a rocky bottom. If the latter, it won't be so hard, but if the sand has worked in and partly covered it, we'll have some difficulties, if I may be permitted to say so. However, don't borrow trouble. We're not there yet, though at the rate we're traveling it won't be long before we arrive."

No watch was set that night, as it was not considered necessary. Tom was the first to arise in the morning, and he went out on the deck for a breath of fresh air before breakfast.

He looked off at the beautiful little island, and as his eye took in all of the little lagoon where the submarine was anchored he uttered a startled cry.

And well he might, for, not a hundred yards away, and nearer to the island than was the Advance, floated another craft--another craft, almost similar in shape and size to the one built by the Swifts. Tom rubbed his eyes to make sure he was not seeing double. No, there could be no mistake about it. There was another submarine at the tropical island.

As he looked, some one emerged from the conning tower of the second craft. The figure seemed strangely familiar. Tom knew in a moment who it was--Addison Berg. The agent saw the lad, too, and taking off his cap and making a mocking bow, he called out:

"Good morning! Have you got the gold yet?"

Tom did not know what to answer. Seeing the other submarine, at an island where he had supposed they would not be disturbed, was disconcerting enough, but to be greeted by Berg was altogether too much, Tom thought. His fears that the rival boat builders would follow had not been without foundation.

"Rather surprised to see us, aren't you?" went on Mr. Berg, smiling.

"Rather," admitted Tom, choking over the word.

"Thought you'd be," continued Berg. "We didn't expect to meet you so soon, but we're glad we did. I don't altogether like hunting for sunken treasure, with such indefinite directions as I have."

"You--are going to--" stammered Tom, and then he concluded it would be best not to say anything. But his talk had been heard inside the submarine. His father came to the foot of the conning tower stairway.

"To whom are you speaking, Tom?" he asked.

"They're here, dad," was the youth's answer.

"Here? Who are here?"

"Berg and his employers. They've followed us, dad."

Chapter Sixteen

"We'll Race You For It"

Mr. Swift hurried up on deck. He was accompanied by Captain Weston. At the sight of Tom's father, Mr. Berg, who had been joined by two other men, called out:

"You see we also concluded to give up the trial for the Government prize, Mr. Swift. We decided there was more money in something else. But we still will have a good chance to try the merits of our respective boats. We hurried and got ours fitted up almost as soon as you did yours, and I think we have the better craft."

"I don't care to enter into any competition with you," said Mr. Swift coldly.

"Ah, but I'm afraid you'll have to, whether you want to or not," was the insolent reply.

"What's that? Do you mean to force this matter upon me?"

"I'm afraid I'll have to--my employers and I, that is. You see, we managed to pick up your trail after you left the Jersey coast, having an idea where you were bound, and we don't intend to lose you now."

"Do you mean to follow us?" asked Captain Weston softly.

"Well, you can put it that way if you like," answered one of the two men with Mr. Berg.

"I forbid it!" cried Mr. Swift hotly. "You have no right to sneak after us."

"I guess the ocean is free," continued the rascally agent.

"Why do you persist in keeping after us?" inquired the aged inventor, thinking it well to ascertain, if possible, just how much the men knew.

"Because we're after that treasure as well as you," was the bold reply. "You have no exclusive right to it. The sunken ship is awaiting the first comer, and whoever gets there first can take the gold from the wreck. We intend to be there first, but we'll be fair with you."

"Fair? What do you mean?" demanded Tom.