"Steady, now!" he warned. "When you feel giddy, let me know, and we'll go back." The effect of the chasm, from the very edge of the rock, was terrifying. It was like nothing ever seen by human eyes. Peering down into the Grand Canyon of the Colorado would have been child's play beside it. For this was no question of looking down a half-mile, a mile, or even five, to some solid bottom. Bottom there was none--nothing save dull purple haze, shifting vapors, and an unearthly dim light which seemed to radiate upward as though the sun's rays, reflected, were striving to beat up again. "There must be miles and miles of air below us," said Stern, "to account for this curious light-effect. Air, of course, will eventually cut off the vision. Given a sufficiently thick layer, say a few hundred miles, it couldn't be seen through. So if there _is_ a bottom to this place, be it one hundred or even five hundred miles down, of course we couldn't see it. All we could see would be the air, which would give this sort of blue effect." "Yes; but in that case how can we see the sun, or the moon, or stars?" "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.