Curious as to the reason why Pax had isolated himself in this frozen wilderness, they next examined the high cliffs which shut in the valley on the west and against the almost perpendicular walls of which he had played the Lavender Ray. These cliffs proved, as Bennie had already suspected, to be a gigantic outcrop of pitchblende or black oxide of uranium. He estimated that nature had stored more uranium in but one of the abutments of this cliff than in all the known mines of the entire world. This radioactive mountain was the fulcrum by which this modern Archimedes had moved the earth. The vast amount of matter disintegrated by the Ray and thrown off into space with a velocity a thousandfold greater than the blast of a siege gun produced a back pressure or recoil against the face of the cliff, which thus became the "thrust block" of the force which had slowed down the period of the earth's rotation. * * * * * The day of the start dawned with a blazing sun. From the landing stage of the Ring Bennie could see stretching away to the east, west, and south, the interminable plains, dotted with firs, which had formed the natural barrier to the previous discovery of Pax's secret. Overhead the dome of the sky fitted the horizon like an enormous shell--a shell which, with a thrill, he realized that he could crack and escape from, like a fledgling ready for its first flight. And yet in this moment of triumph little Bennie Hooker felt the qualm which must inevitably come to those who take their lives in their hands. An hour and he would be either soaring Phoebus-like toward the south, or lying crushed and mangled within a tangled mass of wreckage. Even here in this desolate waste life seemed sweet, and he had much, so much to do. Wasn't it, after all, a crazy thing to try to navigate the complicated mechanism back to civilization? Yet something told him that unless he put his fate to the test now he would never return. He had the utmost confidence in Burke--he might never be able to secure his services again--no, it was now or never. He entered the air-lock, closing and bolting the door, and passed on into the chart room. At all events, he thought, they were no worse off than Pax when he had made his first trial flight, and they were working with a proven machine, tuned to its fullest efficiency, and one which apparently possessed automatic stability. Atterbury had gone to the condenser room and was waiting for the order to start, while Burke was making the final adjustment of the gyroscopes which would put the Ring on its predetermined course. He came through the door and joined Bennie. "Hooker," he said, "we're sure going to have some experience. If I can keep her from turning over, I think I can manage her. The trouble will come when we slant the tractor. I'm not sure how much depends on the atmospheric valve, and how much on me. Things may happen quickly. If we turn over we're done for."