Behind him, from the direction of the lake, he heard a sudden clangor as of rock beating against metal. This endured only a short time. Then the solid ground beneath him shook slightly, and an appalling crash of trees and underbrush to the rear told him that the stone colossus was on his trail. He leaped to his feet and continued his great bounds over the sharply curved surface of the asteroid, banging against tree trunks, bruising himself against stones, falling in the darkness to rise again and flee as before in a mad attempt to distance the crashing sound of pursuit behind him. Then he felt himself writhing in thin air as his flying course took him over the edge of a cliff. Down, down he fell, to land in a dense bed of foliage far below. Something hit his head with terrific force. Pinwheels of light flashed before his eyes, to fade into velvety nothingness.... * * * * * Slowly, uncertainly he wavered back to consciousness. For a moment he was aware of nothing save that he was lying on some surface that was jagged and uncomfortable, and that it was broad daylight. He opened his eyes, and saw that he was reclining, across a springy bed formed of the top of a tree. Ahead of him loomed a cliff about a hundred feet high. Remembrance suddenly came to him. The unreasoning rush through the underbrush. The nightmare creature lumbering swiftly after him. The fall over the cliff into the top of this tree. With a cry, he sat up, expecting to see the stone giant nearby and poised to leap. But it was nowhere in sight; nor, listen as intently as he would, could he hear the sounds of its crashing path through the brush. Somehow, for the moment at least, he had been saved. Perhaps his disappearance over the cliff edge had thrown it off his track. He became aware of the fact that it was difficult for him to breathe. His lungs were heaving in a vain effort to suck in more oxygen, and his tongue felt thick as though he were being strangled. Then he saw that his oxygen concentrator had been knocked from his head when he fell, and was dangling from a limb several feet away. It was almost out of breathing range. Had it fallen on through the branches to the ground he would have died, in his unconsciousness, in the rarified atmosphere. He reached for it; settled the band around his head again. After once more listening and peering around to make sure the rock colossus was not about, he descended the tree that had saved his life, and began to walk in the direction he judged the lake to be. He would get into his Dart, cruise aloft out of harm's way, and perhaps think up some effective course of action. * * * * *