"I am going to try the same experiment we attempted on the volcanic island," was the reply. "Only, this time, I am afraid we shall have to complete it to the end. There is little likelihood of the ice falling apart." "Then you are going to blow it up?" went on Jack. "That's what I hope to do," the inventor went on. "I see no other way, and, though there is a risk, it is not so great a one as to wait to be crushed in the ice as it freezes more solidly." Under the directions of Mr. Henderson they got out the diving suits. The professor, the two boys and Andy put them on. The dynamite, in specially prepared water-proof packages, with long fuses was laid in readiness close to the door of the diving chamber. Into the cell, the four who were to make the perilous journey under the ice, took their places. The water was slowly admitted, and then, with the electric lights in their helmets throwing out powerful gleams, they started forward as the outer door swung open. It was well they had all taken the precautions to don thick undergarments and clothing, for, even through the heavy rubber diving suits, the terrible cold of the southern polar sea struck a chill to their very bones. As the professor had said, the ship was caught between the upper and lower parts of the iceberg. On either side, ahead and to the rear there was open water. Beneath their feet there was a floor of ice. It was as if they and the ship had been placed between two great sheets of the frozen matter. Their progress was slow, for the water hampered their movements and each one had some of the dynamite to carry. The footing, too, was insecure, for the icy bed of the ocean was slippery. As they were huddled together, the professor in the lead, and their lamps making a faint illumination in the darkness, they suddenly became aware of a great shadow over them. They looked up, and their hearts nearly ceased beating as they saw a gigantic sperm whale right over them, and between the ice. The terrible animal had observed them also, and, food being scarce in those frigid regions, had evidently made up its mind to dine on some choice morsels. The whale was nearly as large again as the submarine, and to the frightened voyagers seemed more immense than a house. With slow motions of the flukes the animal placed itself right over the boys and men, ready to rush at and take them into its terrible maw. Old Andy, who alone seemed to retain his presence of mind, stepped to the front. The professor and the boys wondered what he was going to do. Then Andy held up one of the electric guns.