"A collier, I would say," was her father's calm reply. "Rather a large one, too. _Cyclops_, possibly. She disappeared some years ago, en route from the Barbados to Norfolk. Or possibly it is any one of a dozen other steel vessels that have vanished from these seas in recent times. The area of the Sargasso, my dear, is known as 'The Port of Missing Ships.'" "But couldn't we drop down and make sure which ship it is?" she pleaded, voicing the very thought Larry had been struggling to suppress. At the professor's reply, however, he was glad he had kept quiet. "We could, of course," was his gentle though firm rebuke, "but if we stopped to solve the mystery of every sunken ship we shall probably see during this cruise, we would have time for nothing else. Nevertheless, my dear, you may take a short memorandum of the location and circumstances, in the present instance." Whereupon he dictated briefly, while Larry devoted his attention once more to the central square. * * * * * Suddenly, beyond a dark pit that seemed to reach down into the very bowels of the earth, rose an abrupt plateau--and on one of its nearer elevations, almost directly under then, loomed a monumental four-sided mound. "Say--hold on!" called Larry. "Look at that, Professor! Isn't that a building of some kind?" Martin Stevens looked up, glanced skeptically toward the panel. But one glimpse at what that central square revealed, and his skepticism vanished. "A building?" he cried in triumph. "A building indeed! It is a pyramid, young man!" "Good Lord!" "Oh, daddy! Really?" "Beyond a doubt! And look--there are two other similar structures, only smaller!" Struggling for calm, he turned to Captain Petersen, who had taken his eyes from the forward square and was peering down as well upon those singular mounds. "Stop! Descend!" was his exultant command. "This is my proof! We have discovered Antillia!" * * * * * Swiftly the _Nereid_ dropped to that submerged plateau. In five minutes, her keel was resting evenly on the smooth sand beside the largest of the three pyramids. Professor Stevens then announced that he would make a preliminary investigation of the site at once. "For, otherwise, I for one would be quite unable to sleep tonight!" declared the graybeard, with a boyish chuckle. He added that Diane would accompany him. At this latter announcement, Larry's heart sank. He had hoped against hope that he might be invited along with them. But once again his champion came to his aid. "We really ought to let Mr. Hunter come with us, daddy, don't you think?" she urged, noting his disappointment. "After all, it was he who made the discovery." "Very true," said her father, "but I had not thought it necessary for anyone to accompany us. In the event anyone does, Captain Petersen should have that honor." But this honor the captain declined.