"I'm afraid you'll be disappointed," went on the inventor. "In the first place most treasure ships are looted before they sink. And it would be very dangerous for any of us to venture to explore those hulks." "Why?" asked Jack. "Because they are rotten, and liable to fall to pieces any minute. If you happened to be in one at the time you would be caught in the wreckage and eventually drowned even though you had on a diving suit. Then, again, the ice here is constantly shifting about, and a sudden motion of the under-water floe might carry you hundreds of miles away. So we will not try to hunt for any fortunes on the sunken ships." With this the boys were forced to be content. They stood at the small windows looking at the skeletons of ships that lay on every side of the _Porpoise_. Some of the craft were big steamers, and others were small sailing vessels. A few had jagged holes in the hulls, showing how they had been damaged. A few stood upright, with sails all set, as if disaster had suddenly come upon them. "Well, what is the next move?" asked Andy after a pause. "Are we going to stay here?" "We are going to find the South Pole," spoke Mr. Henderson suddenly. "That is what I set out to do, and I am going to accomplish it if possible. We have had many accidents and a harder time in some respects than when we made our trip to the north in the air ship. But I am sure we shall succeed. Start the ship to the south, Washington." "But we may run into an iceberg," objected the old hunter, who was inclined to be cautious. "I think not," answered Mr. Henderson. "I believe we are on a sort of level plane between two vast upper and lower fields of ice. We can go freely in any direction excepting up or down." "How is that?" asked Mark. "I don't quite understand." "Because there is, I believe, a big sheet of ice above us, one, say several hundred feet thick. The same thing is below us, between us and the real bed of the ocean." "But suppose we have to go up to renew our air supply?" asked Jack. "We can't go," replied the inventor. "Then we will die." "Not necessarily. We will steam along until we come to a place where there is no ice above us." "But I thought you said there was nothing but ice above us now." "So there is, but I intend to head due south and there, I believe, we will find an open polar sea. If we do my theory will be proved and we will have made a great discovery." "Forward then!" exclaimed Jack. "Let us strike for the open sea." The _Porpoise_ began to move ahead. She steamed slowly, for Mr. Henderson realized that he was in dangerous waters. He took his position in the conning tower, and had Jack with him to assist in looking for any obstructions that they might unexpectedly meet. The big searchlight gave a fine illumination, for the ice above and below reflected back the beams, and what would otherwise have been a sea of darkness was made one of daylight.