At his words there came the terrific vibration. The light of the dome died out, leaving them in utter darkness, and from its interior there rose the mounting scream that had frightened old Thomas away. From so close by it was hideous, devastating; and the two men clung to each other in fright, expecting momentarily that the earth would give way beneath their feet and precipitate them into some terrible depth from which there could be no return. Then the sound abruptly ceased and a gleam of light came from under the dome of silver. A crack appeared between its lower edge and the rocky floor of the cavern, and through this crack there shone a light of dazzling brilliancy--a warm light of rosy hue. Wider grew the opening until there was a full three feet between the floor and the bottom of the dome. Impelled by some irresistible force from within, the two men stumbled blindly to the opening, fell to the floor and rolled inside. There was a heavy thud and the dome had returned to its normal position, with Frank and Tommy prisoners within its spacious hollow. The warm light bathed them with fearful intensity for a moment, then faded to a rosy glow that dulled their senses and quieted their nerves. Morpheus claimed them. * * * * * When Frank awoke he found himself between silken covers, and for a moment he gazed thoughtfully at a high arched ceiling that was entirely unfamiliar. Then, remembering, he sprang from the downy bed to his feet. The room, the furnishings, his silken robe, everything was strange. His bed, he saw, was a high one, and the frame was of the same gleaming silver as the dome under which they had been trapped. The arched ceiling glowed softly with the same rosy hue as had the inner surface of the dome. A large pool of water invited him, the surface of the pool being no more than a foot below the point where it was built into the tile floor of the room. A large open doorway connected with a similar adjoining room, where he suspected Tommy had been taken. On his bare toes, he moved silently to the other room and saw that his guess had been correct. Tommy lay sleeping quietly beneath covers as soft as his own and amidst equal luxury of surroundings. "Well," he whispered, "this doesn't look as though we would come to any harm. And I might as well take a dive in that pool." Returning to his own room, he removed the silken garment with which he had been provided and was quietly immersed in the cool, invigorating water of the bath. His head cleared instantly. "Hi there!" called Tommy from the doorway. "Why didn't you wake me up? Where are we, anyway?"