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.