These and many other questions perplexed the travelers, but most of all they sought to know the breadth of the vast gap and to determine if it had, as they hoped, another side, or if it were indeed the edge of an enormous mass split bodily off the earth. Stern believed he had an answer to this problem on the afternoon of the second day. For many hours he had hung his pendulums over the cliff, noted deflections, taken triangulations, and covered the surface of the smooth stone with X's, Y's, Z's, sines and cosines and abstruse formulae--all scrawled with charcoal, his only means of writing. At last he finished the final equation, and, with a smile of triumph and relief, got to his feet again. Back to the girl, who was cooking over an odorous fire of cedar, he made his way, rejoicing. "I've got it!" he shouted gladly. "Making reasonable allowances for depth, I've got it!" "Got what?" "The probable width!" "Oh!" And she stood gazing at him in admiration, beautiful and strong and graceful. "You mean to say--" "I'm giving the chasm a hundred miles' depth. That's more than anybody could believe possible--twice as much. On that assumption, my tests show the distance to the other side--and there is another side, by the way!--can't be over--" "Five hundred miles?" "Nonsense! Not over one hundred to one-fifty. I'm going on a liberal allowance for error, too. It may not be over seventy-five. The--" "But if that's as far as it is, why can't we see the other side?" "With all that chemicalized vapor rising constantly? Who knows what elements may be in it? Or what polarization may be taking place?" "Polarization?" "I mean, what deflection and alteration of light? No wonder we can't see! But we can fly! And we're going to, what's more!" "Going to make a try for Chicago, then?" she asked, her eyes lighting up joyfully at thought of the adventure. "To-morrow morning, sure!" "But the alcohol?" "We've still got what we started with from Detroit, minus only what we've burned reaching this place. And we reckoned when we set out that it would far more than be enough. Oh, that part of it's all right!" "Well, you know best," she answered. "I trust you in all things, Allan. But now just look at this roast partridge; come, dear, let to-morrow take care of itself. It's supper-time now!" After the meal they went to the flat rock and sat for an hour while the sun went down beyond the void. Its disappearance seemed to substantiate the polarization theory. There was no sudden obliteration of the disk by a horizon. Rather the sun faded away, redder and duller; then slowly losing form and so becoming a mere blur of crimson, which in turn grew purple and so gradually died away to nothing.