Then began a search that lasted nearly a week. Back and forth they cruised, around in great circles, with the powerful searchlight focused to disclose the sunken treasure ship. Once Tom, who was observing the path of light in the depths from the conning tower, thought he had seen the remains of the Boldero, for a misty shape loomed up in front of the submarine, and he signaled for a quick stop. It was a wreck, but it had been on the ocean bed for a score of years, and only a few timbers remained of what had been a great ship. Much disappointed, Tom rang for full speed ahead again, and the current was sent into the great electric plates that pulled and pushed the submarine forward.
For two days more nothing happened. They searched around under the green waters, on the alert for the first sign, but they saw nothing. Great fish swam about them, sometimes racing with the Advance. The adventurers beheld great ocean caverns, and skirted immense rocks, where dwelt monsters of the deep. Once a great octopus tried to do battle with the submarine and crush it in its snaky arms, but Tom saw the great white body, with saucer-shaped eyes, in the path of light and rammed him with the steel point. The creature died after a struggle.
They were beginning to despair when a full week had passed and they were seemingly as far from the wreck as ever. They went to the surface to enable Captain Weston to take another observation. It only confirmed the other, and showed that they were in the right vicinity. But it was like looking for a needle in a haystack, almost, to find the sunken ship in that depth of water.
"Well, we'll try again," said Mr. Swift, as they sank once more beneath the surface.
It was toward evening, on the second day after this, that Tom, who was on duty in the conning tower, saw a black shape looming up in front of the submarine, the searchlight revealing it to him far enough away so that he could steer to avoid it. He thought at first that it was a great rock, for they were moving along near the bottom, but the peculiar shape of it soon convinced him that this could not be. It came more plainly into view as the submarine approached it more slowly, then suddenly, out of the depths in the illumination from the searchlight, the young inventor saw the steel sides of a steamer. His heart gave a great thump, but he would not call out yet, fearing that it might be some other vessel than the one containing the treasure.
He steered the Advance so as to circle it. As he swept past the bows he saw in big letters near the sharp prow the word, Boldero.
"The wreck! The wreck!" he cried, his voice ringing through the craft from end to end. "We've found the wreck at last!"
"Are you sure?" cried his father, hurrying to his son, Captain Weston following.
"Positive," answered the lad. The submarine was slowing up now, and Tom sent her around on the other side. They had a good view of the sunken ship. It seemed to be intact, no gaping holes in her sides, for only her plates had started, allowing her to sink gradually.
"At last," murmured Mr. Swift. "Can it be possible we are about to get the treasure?"