"But if it were a canyon, why should blue sky show down there at an angle of forty-five degrees?"
"I'll have to think that out, later," he replied. "Directly under us, you see all seems deep purple. That's another fact to consider. I tell you, Beatrice, there's more to be figured out here than can be done in half an hour.
"As I see it, some vast catastrophe must have rent the earth, a thousand or fifteen hundred years ago, as a result of which everybody was killed except you and me. We're standing now on the edge of the scar left by that explosion, or whatever it was. How deep or how wide that scar is, I don't know. Everything depends on our finding out, or at least on our guessing it with some degree of accuracy."
"How so?"
"Because, don't you see, this chasm stands between us and Chicago and the West, and all our hopes of finding human life there. And--"
"Why not coast south along the edge here, and see if we can't run across some ruined city or other where we can refill the tanks?"
"I'll think it over," the engineer answered. "In the meantime we can camp down here a couple of days or so, and rest; and I can make some calculations with a pendulum and so on."
"And if you decide there's probably another side to this gulf, what then?"
"We cross," he said; then for a while stood silent, musing as he peered down into the bottomless abyss that stretched there hungrily beneath their narrow observation-rock.
"We cross, that's all!"