"You are right, my boy. A planet it surely is," he said to Jack. "But why have we never seen it before?" demanded Mark. "For a very good reason," returned the professor, solemnly. "We were never in a position before to behold that planet, save on two occasions." "Then we have seen it twice before?" asked the puzzled Jack. "On two occasions we have been enabled to stand off, as it were, and look at that planet as though we were inhabitants of another world--when we went to the moon, and when we went to Mars." "What do you mean, Professor?" cried Mark. "It's the earth!" exclaimed Jack Darrow. "It's the earth! We have left the earth--is that it, Professor?" The old scientist nodded. Phineas Roebach snorted his disbelief, while Washington White gave vent to his trouble of mind most characteristically: "Goodness gracious gollyation! De fat am suah in de fiah now! We'se done los' de earf an' Buttsy an' me will nebber see our happy home no mo'." "Oh, Professor! how could we have left the earth?" demanded Mark. "See! we are standing upon it now; at least, this glacier is an ice-river of Alaska, and Alaska has not been wiped off the map!" "But that is exactly what has happened to it," said the professor, earnestly. "At least, a part of Alaska--we do not know how much of that territory, or how much other territory with it--is no longer a part of the sphere called the earth." Phineas Roebach looked at the old scientist as though he thought the latter had taken leave of his senses. But Jack Darrow leaped to the right conclusion. "You mean, sir, that the earthquake and the volcanic eruption have torn away some great fragment of the world, and we are on it?" "That is what I mean." "We are floating in space, then--an entirely new world? And _that_ is the old world shining there in the sky?" "That is what has happened, Jack," declared Professor Henderson, with solemnity. "I suspected it when we first felt the lightness of the atmosphere. I was convinced when I found the ether envelope of this new world--this island in the air, as it were--was so thin. My calculations regarding the rising of the moon, and the outlines of objects upon the great globe hanging yonder, prove to my mind conclusively that the awful cataclysm we endured, when we all completely lost consciousness, was the time when the eruption occurred, and we, with this great fragment of the earth, were blown out into space." "It can't be! it can't be!" shouted Phineas Roebach. "We've lost our heads, perhaps; but we haven't lost our hold on the earth. It's nonsense!"