"down deep," advised captain weston, as he stood beside tom and mr. swift in the pilot house. "as far as you can manage her, and then forward. we'll take no more chances with these fellows."

"the only trouble is," replied the young inventor, "that the deeper we go the slower we have to travel. the water is so dense that it holds us back."

"well, there is no special need of hurrying now," went on the sailor. "no one is following you, and two or three days difference in reaching the wreck will not amount to anything."

"unless they repair their rudder, and take after us again," suggested mr. swift.

"they're not very likely to do that," was the captain's opinion. "it was more by luck than good management that they picked us up before. now, having to delay, as they will, to repair their steering gear, while we can go as deep as we please and speed ahead, it is practically impossible for them to catch up to us. no, i think we have nothing to fear from them."

but though danger from berg and his crowd was somewhat remote, perils of another sort were hovering around the treasure-seekers, and they were soon to experience them.

it was much different from sailing along in the airship, tom thought, for there was no blue sky and fleecy clouds to see, and they could not look down and observe, far below them, cities and villages. nor could they breathe the bracing atmosphere of the upper regions.

but if there was lack of the rarefied air of the clouds, there was no lack of fresh atmosphere. the big tanks carried a large supply, and whenever more was needed the oxygen machine would supply it.

as there was no need, however, of remaining under water for any great stretch of time, it was their practice to rise every day and renew the air supply, also to float along on the surface for a while, or speed along, with only the conning tower out, in order to afford a view, and to enable captain weston to take observations. but care was always exercised to make sure no ships were in sight when emerging on the surface, for the gold-seekers did not want to be hailed and questioned by inquisitive persons.

it was about four days after the disabling of the rival submarine, and the advance was speeding along about a mile and a half under water. tom was in the pilot house with captain weston, mr. damon was at his favorite pastime of looking out of the glass side windows into the ocean and its wonders, and mr. swift and the balloonist were, as usual, in the engine-room.

"how near do you calculate we are to the sunken wreck?" asked tom of his companion.

"well, at the calculation we made yesterday, we are within about a thousand miles of it now. we ought to reach it in about four more days, if we don't have any accidents."

"and how deep do you think it is?" went on the lad.

"well, i'm afraid it's pretty close to two miles, if not more. it's quite a depth, and of course impossible for ordinary divers to reach. but it will be possible in this submarine and in the strong diving suits your father has invented for us to get to it. yes, i don't anticipate much trouble in getting out the gold, once we reach the wreck of course—"

the captain's remark was not finished. from the engine-room there came a startled shout:

"tom! tom! your father is hurt! come here, quick!"

"take the wheel!" cried the lad to the captain. "i must go to my father." it was mr. sharp's voice he had heard.

racing to the engine-room, tom saw his parent doubled up over a dynamo, while to one side, his hand on a copper switch, stood mr. sharp.

"what's the matter?" shouted the lad.

"he's held there by a current of electricity," replied the balloonist. "the wires are crossed."

"why don't you shut off the current?" demanded the youth, as he prepared to pull his parent from the whirring machine. then he hesitated, for he feared he, too, would be glued fast by the terrible current, and so be unable to help mr. swift.

"i'm held fast here, too," replied the balloonist. "i started to cut out the current at this switch, but there's a short circuit somewhere, and i can't let go, either. quick, shut off all power at the main switchboard forward."

tom realized that this was the only thing to do. he ran forward and with a yank cut out all the electric wires. with a sigh of relief mr. sharp pulled his hands from the copper where he had been held fast as if by some powerful magnet, his muscles cramped by the current. fortunately the electricity was of low voltage, and he was not burned. the body of mr. swift toppled backward from the dynamo, as tom sprang to reach his father.

"he's dead!" he cried, as he saw the pale face and the closed eyes.

"no, only badly shocked, i hope," spoke mr. sharp. "but we must get him to the fresh air at once. start the tank pumps. we'll rise to the surface."

the youth needed no second bidding. once more turning on the electric current, he set the powerful pumps in motion and the submarine began to rise. then, aided by captain weston and mr. damon, the young inventor carried his father to a couch in the main cabin. mr. sharp took charge of the machinery.

restoratives were applied, and there was a flutter of the eyelids of the aged inventor.

"i think he'll come around all right," said the sailor kindly, as he saw tom's grief. "fresh air will be the thing for him. we'll be on the surface in a minute."

up shot the advance, while mr. sharp stood ready to open the conning tower as soon as it should be out of water. mr. swift seemed to be rapidly reviving. with a bound the submarine, forced upward from the great depth, fairly shot out of the water. there was a clanking sound as the aeronaut opened the airtight door of the tower, and a breath of fresh air came in.

"can you walk, dad, or shall we carry you?" asked tom solicitously.

"oh, i—i'm feeling better now," was the inventor's reply. "i'll soon be all right when i get out on deck. my foot slipped as i was adjusting a wire that had gotten out of order, and i fell so that i received a large part of the current. i'm glad i was not burned. was mr. sharp hurt? i saw him run to the switch, just before i lost consciousness."

"no, i'm all right," answered the balloonist. "but allow us to get you out to the fresh air. you'll feel much better then."

mr. swift managed to walk slowly to the ladder leading to the conning tower, and thence to the deck. the others followed him. as all emerged from the submarine they uttered a cry of astonishment.

there, not one hundred yards away, was a great warship, flying a flag which, in a moment, tom recognized as that of brazil. the cruiser was lying off a small island, and all about were small boats, filled with natives, who seemed to be bringing supplies from land to the ship. at the unexpected sight of the submarine, bobbing up from the bottom of the ocean, the natives uttered cries of fright. the attention of those on the warship was attracted, and the bridge and rails were lined with curious officers and men.

"it's a good thing we didn't come up under that ship," observed tom. "they would have thought we were trying to torpedo her. do you feel better, dad?" he asked, his wonder over the sight of the big vessel temporarily eclipsed in his anxiety for his parent.

"oh, yes, much better. i'm all right now. but i wish we hadn't disclosed ourselves to these people. they may demand to know where we are going, and brazil is too near uruguay to make it safe to tell our errand. they may guess it, however, from having read of the wreck, and our departure."

"oh, i guess it will be all right," replied captain weston. "we can tell them we are on a pleasure trip. that's true enough. it would give us great pleasure to find that gold."

"there's a boat, with some officers in it, to judge by the amount of gold lace on them, putting off from the ship," remarked mr. sharp.

"ha! yes! evidently they intend to pay us a formal visit," observed mr. damon. "bless my gaiters, though. i'm not dressed to receive company. i think i'll put on my dress suit."

"it's too late," advised tom. "they'll be here in a minute."

urged on by the lusty arms of the brazilian sailors, the boat, containing several officers, neared the floating submarine rapidly.

"ahoy there!" called an officer in the bow, his accent betraying his unfamiliarity with the english language. "what craft are you?"

"submarine, advance, from new jersey," replied tom. "who are you?"

"brazilian cruiser san paulo," was the reply. "where are you bound?" went on the officer.

"on pleasure," answered captain weston quickly. "but why do you ask? we are an american ship, sailing under american colors. is this brazilian territory?"

"this island is—yes," came back the answer, and by this time the small boat was at the side of the submarine. before the adventurers could have protested, had they a desire to do so, there were a number of officers and the crew of the san paulo on the small deck.

with a flourish, the officer who had done the questioning drew his sword. waving it in the air with a dramatic gesture, he exclaimed:

"you're our prisoners! resist and my men shall cut you down like dogs! seize them, men!"

the sailors sprang forward, each one stationing himself at the side of one of our friends, and grasping an arm.

"what does this mean?" cried captain weston indignantly. "if this is a joke, you're carrying it too far. if you're in earnest, let me warn you against interfering with americans!"

"we know what we are doing," was the answer from the officer.

the sailor who had hold of captain weston endeavored to secure a tighter grip. the captain turned suddenly, and seizing the man about the waist, with an exercise of tremendous strength hurled him over his head and into the sea, the man making a great splash.

"that's the way i'll treat any one else who dares lay a hand on me!" shouted the captain, who was transformed from a mild-mannered individual into an angry, modern giant. there was a gasp of astonishment at his feat, as the ducked sailor crawled back into the small boat. and he did not again venture on the deck of the submarine.

"seize them, men!" cried the gold-laced officer again, and this time he and his fellows, including the crew, crowded so closely around tom and his friends that they could do nothing. even captain weston found it impossible to offer any resistance, for three men grabbed hold of him but his spirit was still a fighting one, and he struggled desperately but uselessly.

"how dare you do this?" he cried.

"yes," added tom, "what right have you to interfere with us?"

"every right," declared the gold-laced officer.

"you are in brazilian territory, and i arrest you."

"what for?" demanded mr. sharp.

"because your ship is an american submarine, and we have received word that you intend to damage our shipping, and may try to torpedo our warships. i believe you tried to disable us a little while ago, but failed. we consider that an act of war and you will be treated accordingly. take them on board the san paulo," the officer went on, turning to his aides. "we'll try them by court-marital here. some of you remain and guard this submarine. we will teach these filibustering americans a lesson."