It was four or five acres in extent, irregular in contour, and so filled with gases and vapors that one could not see the bottom, while the jagged boundary on the farther side came out to view only at intervals, when the obstructing smoke was swept aside.
Spiral columns of black vapor twisted swiftly upward from the fiery depths, sometimes side by side, and sometimes they would unite and climb toward the opening above, like a couple of huge serpents struggling together.

The air quivered and pulsated in certain portions, as if with fervid heat, and Ashman fancied once or twice that he caught glimpses of a vast mass of molten stuff, far down in the mountain, surging; seething and turning upon itself with terrific violence.

But the glare was so dazzling that it was like staring at the sun, and he was compelled to withdraw his gaze.
The opening above, through which all this vapor and gas effected its escape into the clear atmosphere outside, was of irregular outline and no more than twenty feet across.

It was at a great height above the spectators, and ought to have been visible many miles in every direction.
Now and then Ashman caught the odor of the sulphurous fumes rising from the naming depth, and he could not help reflecting that if the ascending vapors should swerve toward them only for a minute or two, they would be asphyxiated before they could get away; but he could not shrink, when his lovely companion stood so boldly by his side, unmoved by the impressive scene.
When he had become accustomed in a degree to the sight, the like of which he had never viewed before, he recalled that they could not occupy a more conspicuous position, in the event of being pursued by their enemies to the underground lake.
As we have explained, they were standing on the highest portion of the rocky wall, separating the burning mountain from the subterranean portion of the enchanted lake.

In this situation, they were in sight from every portion of the shore; any one entering by the tunnel, as they had done, would descry them almost at once, because of the vivid background against which their figures were thrown.
This fact led Ashman to turn to his love and suggest that they should leave the spot.