"Light from above only has to pierce forty or fifty miles of really dense air. Above that height it's excessively rarified. While down below earth-level, of course, it would get more and more dense all the time, till at the bottom of a five-hundred-mile drop the density and pressure would be tremendous."
Beatrice made no answer. The spectacle she was gazing at filled her with solemn thoughts. Jagged, rent and riven, the rock extended downward. Here vast and broken ledges ran along its flanks--red, yellow, black, all seared and burned and vitrified as by the fire of Hell; there huge masses, up-piled, seemed about to fall into the abyss.
A quarter-mile to southward, a rivulet had found its way over a projecting ledge. Spraying and silvery it fell, till, dissipated by the up-draft from the abyss, it dissolved in mist.
The ledge on which they were lying extended downward perhaps three hundred yards, then sloped backward, leaving sheer empty space beneath them. They seemed to be poised in mid-heaven. It was totally unlike the sensation on a mountain-top, or even floating among the clouds; for a moment it seemed to Stern that he was looking up toward an unfathomable, infinite dome above him.
He shuddered, despite his cool and scientific spirit of observation.
"Some chemical action going on somewhere down there," said he, half to divert his own attention from his thoughts. "Smell that sulphur? If this place wasn't once the scene of volcanic activities, I'm no judge!"
A moderate yet very steady wind blew upward from the chasm, freighted with a scent of sulphur and some other substance new to Stern.
Beatrice, all at once overcome by sudden giddiness, drew back and hid her face in both hands.
"No bottom to it--no end!" she said in a scared tone. "Here's the end of the world, right here, and beyond this very rock--nothing!"
Stern, puzzled, shook his head.
"That's really impossible, absurd and ridiculous, of course," he answered. "There must be something beyond. The way this stone falls proves that."
He pitched a two-pound lump of granite far out into the air. It fell vertically, whirling, and vanished with the speed of a meteor.
"If a whole side of the earth had split off, and what we see down below there were really sky, of course the earth's center of gravity would have shifted," he explained, "and that rock would have fallen in toward the cliff below us, not straight down."
"How can you be sure it doesn't fall that way after the impulse you gave it has been lost?"
"I shall have to make some close scientific tests here, lasting a day or two, before I'm positive; but my impression is that this, after all, is only a canyon--a split in the surface--rather than an actual end of the crust."