Channing led the girl by several yards by the time that they were within sight of the elevator. He waited for her, and then sent the car upward at a full throttle. Minutes passed, and they could feel that stomach-rising sensation that comes when gravity is lessened. Arden clasped her hands over her middle and hugged. She squirmed and giggled. "You've been up to the axis before," said Channing. "Take long, deep breaths." The car came to a stop with a slowing effect. A normal braking stop would have catapulted them against the ceiling. "Come on," he grinned at her, "here's where we make time!" Channing looked up at the little flight of stairs that led to the innermost level. He winked at Arden and jumped. He passed up through the opening easily. "Jump," he commanded. "Don't use the stairs." Arden jumped. She sailed upward, and as she passed through the opening, Channing caught her by one arm and stopped her flight. "At that speed you'd go right on across," he said. She looked up, and there about two hundred feet overhead she could see the opposite wall. Channing snapped on the lights. They were in a room two hundred feet in diameter and three hundred feet long. "We're at the center of the station," Channing informed her. "Beyond that bulkhead is the air lock. On the other side of the other bulkhead, we have the air plant, the storage spaces, and several rooms of machinery." "Come on," he said. He took her by the hand and with a kick he propelled himself along on a long, curving course to the opposite side of the inner cylinder. He gained the opposite bulkhead as well. "Now, that's what I call traveling," said Arden. "But my tummy goes _whoosh_, _whoosh_ every time we cross the center." Channing operated a heavy door. They went in through rooms full of machinery and into rooms stacked to the center with boxes; stacked from the wall to the center and then packed with springs. Near the axis of the cylinder, things weighed so little that packing was necessary to keep them from floating around. "I feel giddy," said Arden. "High in oxygen," said he. "The CO_{2}, drops to the bottom, being heavier. Then, too, the air is thinner up here because centrifugal force swings the whole out to the rim. Out there we are so used to 'down' that here, a half mile above--or to the center, rather--we have trouble in saying, technically, what we mean. Watch!" He left Arden standing and walked rapidly around the inside of the cylinder. Soon he was standing on the steel plates directly over her head. She looked up, and shook her head. "I know why," she called, "but it still makes me dizzy. Come down from up there or I'll be sick." Channing made a neat dive from his position above her head. He did it merely by jumping upward from his place toward her place, apparently hanging head down from the ceiling. He turned a neat flip-flop in the air and landed easily beside her. Immediately, for both of them, things became right-side-up again.