“We have plenty of air, at all events,” said the professor as he took a deep breath. “I was afraid of that, but it seems there was no need. The air appears to be as good and fresh as that on the surface of the earth, only there is a curious property to it. It makes one feel larger. I imagine it must be thinner than the air of the earth, which is a rather strange thing, since the higher one goes the more rarefied the air becomes, and the lower, the more dense. Still we can not apply natural philosophy to conditions under the earth. All the usual theories may be upset. However, we should be content to take things as we find them, and be glad we were not dashed to pieces when the ship was caught in the terrible current.” “What do you suppose caused the awful heat, and then made it go away again?” asked Jack. “I can only make a guess at it,” Mr. Henderson answered. “There are many strange things we will come across if we stay here long, I believe. As for the fire I think we must have passed a sort of interior volcano.” “But what sort of a place do you think we have come to, Professor?” asked Mark. “It is hard to say,” the scientist replied. “We are certainly somewhere within the earth. Our gage tells us it is five hundred miles. That may or may not be correct, but I believe we are several hundred miles under the crust, at all events. As to what sort of a place it is, you can see for yourselves.” “But how is it we can breathe here, and things can grow?” asked Bill, who was beginning to lose his fright at the thought of being practically buried alive. “I do not know what makes such things possible,” Mr. Henderson replied, “but that there is air here is a certainty. I can hardly believe it is drawn from the surface of the earth, down the big hole, and I am inclined to think this place of the under-world has an atmosphere of its own, and one which produces different effects than does our own.” “They certainly have larger flowers than we have,” said Mark. “See how big they grow, and what strong colors they have.” He pointed to the port, against which some of the blooms were nodding in the wind that had sprung up, for, in spite of the many differences, the under-world was in some respects like the upper one. “Probably the difference in the atmosphere accounts for that,” the professor said. “It enables things to grow larger. And, by the way, Mark, that reminds me of something you said about seeing some horrible monster fleeing from the ship. Did you dream that?” “I did see something horrible, Professor,” he answered. “I’m not positive what it was, but I’ll tell you as nearly as I can what it was like.” Thereupon Mark detailed what he had seen. “But how could anything, least of all some big monster, be concealed in the storeroom, and we not know anything about it?” asked Mr. Henderson. “I thought you did know something of it,” replied Mark.