“I think we can chance it now,” remarked Mr. Henderson, as he threw over several levers. “We’ll try, at any rate.” With a tremor the _Mermaid_ left the surface of the inner earth and went sailing upward toward the—well it wasn’t exactly the sky, but it was what corresponded to it in the new world, though there were no clouds and no blue depths such as the boys were used to. At all events the _Mermaid_ was flying again, and, as the adventurers felt themselves being lifted up they gave a spontaneous cheer at the success which had crowned their efforts. The ship went up several hundred feet, and then, the professor, having brought her to a stop, sent her ahead at a slow pace. He wanted to be sure all the apparatus was in good working order before he tried any speed. The _Mermaid_ responded readily. Straight as an arrow through the air she flew. “Well, this is almost as good as being on the regular earth!” exclaimed Jack. “It’s better,” put in Mark. “We haven’t seen half the wonders yet. Let’s open the floor shutter, and see how it looks down below.” He and Jack went to the room where there was an opening in the floor of the ship, covered by heavy glass. They slid back the steel shutter and there, down below them, was the strange new world they had come to, stretched out like some big map. They could see mountains, forests, plains, and rivers, the water sparkling in the colored light. Over green fields they flew, then across some stretches where only sand and rocks were to be seen. Faster and faster the ship went, as the professor found the machinery was once more in perfect order. Jack was idly watching the play of tinted lights over the surface of the ground. “I wonder what makes it,” he said. “I have tried to account for it in several ways,” said the professor, who had called Washington to the conning tower and come to join the boys. “I have had first one theory and then another, but the one I am almost sure is correct is that hidden volcanic fires cause the illumination. “I think they flare up and die away, and have become so regular that they produce the same effect as night and day with us. Probably the fires go out for lack of fuel, and when it is supplied they start up again. Perhaps it is a sort of gas that they burn.” “Well, it’s queer enough, whatever it is,” Jack remarked. “What strikes me as funny, though, is that we haven’t seen a single person since we came here. Surely this place must be inhabited.” Mark thought of the strange shadow he had seen, but said nothing. “I believe it is,” the professor answered. “We will probably come upon the inhabitants soon. I only hope they are a people who will do us no harm.” “If they tried any of their tricks we could mount up in our ship and escape them,” said Andy. “Provided they gave us the chance,” Mr. Henderson put in. “Well, we’ll not worry about that now.”