"I'll be able to tell more about it when I see how they operate when they are flying. That black streak under water ... well, I must see it out of the water, and then...." But here General Munson ended, for the aero-sub which they were especially watching had got into action against the dreadnought. The aero-sub was motionless and submerged just off the port bow of the dreadnought. The three men inside the aero-sub were working swiftly and efficiently with the complicated but minute machinery in the nose of their transport. "It can be controlled, then, this ray," said Munson, interrupting himself. "Watch!" * * * * * From the nose of the aero-sub leaped, like a streak of black lightning, that ebon agency of death. It struck the prow of the battleship--and the prow, as far aft as the well-deck, simply vanished from sight, disintegrated! It was as though it had never been, and for a second, so swiftly had it happened, the water of the ocean held the impression that portion of the warship had made--as an explosive leaves a crater in the soil of earth! Then a drumming roar as the sea rushed in to claim its own. The roaring, as of a Niagara, as the waters claimed the ship, rushing down passageways into the hold, possessing the warship with all the invincible, speedy might of the sea. Mingled with this roaring was the shivering, vibratory sound which Prester Kleig had experienced in his half-dream. The sound was so intense that it fairly rocked the Secret Room to its furthermost cranny. For a second the dreadnought, wounded to death, seemed to shudder, to hesitate, then to move backward as though wincing from her death blow. It was the pound of the inrushing waters which did it. Then up came the stern of the mighty ship, as she started her last long plunge into the depths. But attention had swung to another warship, on the starboard beam of which another aero-sub had taken up position. Again the ebon streak of death from her blunt nose, smashing in and through the warship, directly amidships, cutting her in twain as though the black streak had been a pair of shears, the warship a strip of tissue paper. Up went the prow and the stern of this one, and together, the water separating the two parts as it rushed into the gap, the broken warship went down to its final resting place. * * * * * Abruptly Professor Maniel swung back to the American planes which had come back to investigate the activities of the aero-subs, and on the screen, in the midst of the battle formation into which the pilots had swept to hurriedly, the Secret Agents could see the faces of those pilots.... White as chalk with fear, mouths open in gasping unbelief. One man, a pale-faced youth, was the first to recover. He stared around at his compatriots, and plainly through the sound apparatus in the Secret Room came his swift radio signals. "Attack! Who will follow me against these people?"