"I thought, perhaps, you were thinking of it," he replied. "Why?" "Because you said it was high time we were in the ice belt again!" I started. "And how far have we come?" I asked. "From where?" He looked carefully at his register and made a calculation. He then said: "We are now one thousand three hundred and eighty miles from Von Broekhuysen’s Island, and about one thousand one hundred and thirty miles north of the North Pole—if you can imagine such a thing—I mean that we have advanced upon a straight line for this distance; and as you see, we have met neither ice, snow, nor cold weather yet!" I looked above. The great disk of light was still bright in the heavens; I thought a little nearer the zenith than before. Unless there had been some gross miscalculation in our speed we had got to face a physical problem of the most stupendous nature. A problem so appalling that I began to dread the explanation as much as I had recently sought it. "Yes," I answered in a weak voice, "there is certainly neither ice nor snow here!" "Nor cold!" added Torrence. "Nor cold!" I admitted. "Nor undue heat!" he continued. "Certainly not. The temperature has been perfect." "And the air has a vitality unknown to us in the old world," he pursued. "I grant every word you say. This may be a dream, but it is a paradise!" "It is not a dream!" cried Torrence; "it is another world; a world within our own. Yonder disk of light in the sky is the opening at the pole through which we have sailed. The earth is a hollow globe, with an opening at each pole, through which the sunlight always enters. For six months it comes through the northern opening, and for six months through the southern. But the change is gradual. With the advent of the southern day, the disk is in the south, fading imperceptibly as the northern light supplants it, and _vice versa_. The great aurora borealis which illumines the Arctic regions of our world is simply the sunlight pouring through from the southern hemisphere, or the light which enters the earth at the South Pole, discharging itself at the north. For ages our world was believed to be flat; but time and study proved the fallacy. In the days of Hipparchus and Ptolemy, and for centuries after it was believed that the sun revolved around the earth; what a stupendous change in man’s knowledge when the opposite was found to be the case. From the days of Columbus to our own—with a few notable exceptions—the world was supposed to be filled with amass of molten material; but within recent years facts observed in the boiling of water have compelled men to abandon that theory and substitute that of a world solid to the core. One by one the theories which have stood on the bed rock of science and been held as irrefutable by the wisdom of the age, have crumbled to pieces, and been supplanted by others; and now the faith in a solid earth is to be shattered, for you and I know that it is hollow—light and inhabited.