He hauled the unconscious child in first, and then Jack gave Mark a hand. As if by magic all the whales had disappeared and the sea was quiet again. In a few minutes the rescuers and the rescued one went back again on the _Porpoise_, where Professor Henderson soon brought Nellie around again. Beyond the shock and wetting neither she nor Mark was harmed. It was Jack's watch on deck that night. He had the tour from eight until twelve o'clock and when, about ten, every one but himself had retired, he took his position in the door of the conning tower and prepared to pass the time as best he could. The ship was moving along at half speed, and, as the automatic steering attachment was working Jack had little to do. He sat looking at the stars that twinkled in the sky, the blazing Southern Cross showing among the constellations, when he heard a slight noise near the companionway. He looked in that direction and, to his horror, he saw the ghostly white shape that had, on previous occasions, caused him and the others fright. At first the boy resolved to shut himself up in the tower and wait until the uncanny thing had disappeared. Then his courage came back and he thought he would try to solve the mystery. He argued that if the weird white object was human and could witness his movements the best thing to do would be to try and creep upon it unobserved. On the contrary, if the ghost was some natural phenomenon, or a supernatural agent, all he could do would be of no avail. So he decided the best thing to do would be to crawl upon the thing, keeping as near to the deck as possible and trying to hide himself. With this in view he put on a long rain coat that hung in the conning tower, and then, like a snake, commenced to wiggle his way toward the middle of the platform where the white object still stood. Nearer and nearer to it Jack came. His heart was beating fast and he was much frightened, but he nerved himself to continue. As he came closer he could see that the object looked more and more like a man, completely robed in white garments. Jack was now within ten feet of the strange object. It was a man, he was sure of it, but whether a present or former inhabitant of the earth he could not decide. Jack's hair was beginning to raise. A cold shiver ran down his spine as the white thing lifted an arm and seemed to point directly at him. At the same time it groaned in a deep tone. Jack let out a yell that could be heard all over the ship. He made a spring for the object, determined to discover what it was or die. At that instant the whole ship seemed to rise in the air. It left the water and began moving skyward. Right out of the waves the _Porpoise_ was lifted until the big screw was clear of the water and it was churning around in the tunnel without any resistance, racing at top speed now that it had no water to thrust against. Then the ghost seemed to vanish into thin air, and Jack felt himself falling down the hatchway. CHAPTER XX