tom felt such a relief at hearing of captain weston's ruse that his appetite, sharpened by an early breakfast and the sea air, came to him with a rush, and he had a second morning meal with the odd sea captain, who chuckled heartily when he thought of how mr. berg had been deceived.

"yes," resumed captain weston, over his bacon and eggs, "i sized him up for a slick article as soon as i laid eyes on him. but he evidently misjudged me, if i may be permitted that term. oh, well, we may meet again, after we secure the treasure, and then i can show him the real map of the location of the wreck."

"then you have it?" inquired the lad eagerly.

captain weston nodded, before hiding his face behind a large cup of coffee; his third, by the way.

"let me see it?" asked tom quickly. the captain set down his cup. he looked carefully about the hotel dining-room. there were several guests, who, like himself, were having a late breakfast.

"it's a good plan," the sailor said slowly, "when you're going into unknown waters, and don't want to leave a wake for the other fellow to follow, to keep your charts locked up. if it's all the same to you," he added diffidently, "i'd rather wait until we get to where your father and mr. sharp are before displaying the real map. i've no objection to showing you the one mr. berg saw," and again he chuckled.

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.