"That's to be expected," said the Doctor. "But we're a third the way down, just the same; that's the main thing." He glanced up the rocky, precipitous wall behind them. "We've come down a thousand feet, at least. The valley must be three thousand feet deep or more now."
"Say, how deep does it get before it stops?" inquired the Very Young Man.
The Doctor smiled at him quietly. "Rogers's note put it about twelve thousand," he answered. "It should reach that depth and stop about"—he hesitated a moment, calculating—"about two o'clock," he finished.
"Some climb," commented the Very Young Man. "We could do this a lot better than we're doing it, I think."
For some time they sat in silence. From where they sat the valley had all the appearance of a rocky, barren cañon of their own world above, as it might have looked on the late afternoon of a cloudless summer day. A gentle breeze was blowing, and in the sky overhead they could still see the huge light that for them was the sun.
"The weather is certainly great down here anyway," observed the Very Young Man, "that's one consolation."
The Big Business Man had replaced his shoes, taken a swallow of water, and risen to his feet, preparing to start downward again, when suddenly they all noticed a curious swaying motion, as though the earth were moving under them.
"Now what?" ejaculated the Very Young Man, standing up abruptly, with his feet spread wide apart.
The ground seemed pressing against his feet as if he were weighted down with a heavy load. And he felt a little also as though in a moving train with a side thrust to guard against. The sun was no longer visible, and the valley was plunged in the semidarkness of twilight. A strong wind sprang up, sweeping down upon them from above.
The Very Young Man and the Big Business Man looked puzzled; the Doctor alone of the three seemed to understand what was happening.