"That's not fire," Edmund responded earnestly. "But what it is I confess I can't imagine. We'll find out, however, for I haven't come all this distance to be scared off." And here I must try to explain a very curious thing which had puzzled our senses, though not our understanding (because Edmund had promptly explained it), throughout the voyage, and that was--levitation. On our first day out from the earth, we began to notice the remarkable ease with which we handled things, and the strange tendency we had to bump into one another because we seemed to be all the time employing more strength than was necessary and almost to be able to walk on air. Jack declared that he felt as if his head had become a toy balloon. "It's the lack of weight," said Edmund. "Every time we double our distance from the earth we lose another three quarters of our weight. If I had thought to bring along a spring dynamometer, I could have shown you, Jack, that when we were 4,000 miles above the earth's surface the 200 good pounds with which you depress the scales at home had diminished to 50, and that when we had passed about 150,000 miles into space you weighed no more than a couple of ounces. From that point on, it has been the attraction of the sun to which we have owed whatever weight we had, and the floor of the car has been toward the sun, because, at that distance from the earth, the latter ceases to exercise the master force, and the pull of the sun becomes greater than the earth's. But as we approach Venus the latter begins to restore our weight, and when we arrive on her surface we shall weigh about four fifths as much as when we started from the earth." "But I don't look as if I had lost any avoirdupois," said Jack, glancing at his round limbs. "And when you give us a fling I seem to strike pretty hard, though in other respects I confess I do feel a good deal like an angel." "Ah," said Edmund, laughing, "that's the _inertia of mass_. Your mass is the same, although your weight has almost disappeared. Weight depends upon the distance from the attracting body, but mass is independent of everything." "Do you mean to say that angels are massive?" "They may be as massive as they like provided they keep well away from great centers of gravitation." "But Venus is such a center--then there can't be any angels there." "I hope to find something better than angels," was Edmund's smiling reply. Now, as we drew near to Venus, the truth of Edmund's statements became apparent. We felt that our weight was returning, and our muscular activity sinking back to the normal again. We imagined that every minute we could feel our feet pressing more heavily upon the floor. Our approach was so rapid that the immense black circle grew visibly minute by minute. Soon it was so large that we could no longer see its boundaries through the peephole in the floor.