"On this small radio phone. A pair of receivers tuned to the right wave-length are in my diving helmet, and I will be able to hear you although I can't reply. I won't be gone long: I have only a small air tank, large enough to keep me going for thirty minutes. Now help me into my suit and keep a sharp watch. A timely warning may save my life if anything happens." With Carnes' assistance, Dr. Bird donned a deep-sea diving outfit and screwed down the helmet. He crawled through the inner door into the lock and lifted the inner door into place. Carnes fastened the door with nuts and the Doctor opened a pair of valves in the outer door and filled the lock with water. He removed the outer door; and, taking in one hand a steel-shod twelve-foot pike with a hook on the end, and in the other a waterproof flashlight, he sallied forth. As he left the shell he paused for a moment, and then returned and picked up the heavy wrench with which he had removed the nuts holding the outer door into place. He fastened the tool to the belt of his suit. Then, with a wave of his hand toward the detective, he approached the hulk. The hole in the side was too high for him to reach, but he hooked the end of his pike in one of the joints of the _Arethusa's_ plates and climbed slowly and painfully up the side of the vessel. As he disappeared into the hull, Carnes realized with a sudden start that he had been watching his friend and neglecting the duty imposed on him of keeping a sharp watch. He turned quickly to the floodlights and searched the sea bottom. * * * * * Nothing appeared, and the minutes moved as slowly as hours should. Carnes felt that he had been submerged alone for weeks, and his nerves grew so tense that he felt that he would scream in another instant. A sudden thought sobered him like a dash of cold water. If he screamed, Dr. Bird would take it for an alarm signal and possibly be afraid to emerge from the vessel. His watch showed him that the Doctor had been gone for twenty-five minutes and he moved slowly to the radio transmitter. "Dr. Bird," he said slowly and distinctly, "you have been gone nearly thirty minutes. Nothing alarming has appeared but I will feel better when I see you coming back." He glued his eyes on the opening in the ship's side and waited. Five minutes passed, and then ten, with no signs of the Doctor. Carnes moved again to the receiver. "It has been over half an hour. Doctor," he cried in a pleading voice. "If you are all right, for God's sake show yourself. I am frantic with worry."