All was dark, and even the glow behind was fading away; nor could I make any conjecture whatever as to the size of the channel.

At the opening it had been contracted and narrow; but here it might have expanded itself to miles, and its vaulted top might reach almost to the summit of the lofty mountains.

While sight thus failed me, sound was equally unavailing, for it was always the same--a sustained and unintermittent roar, a low, droning sound, deep and terrible, with no variations of dashing breakers or rushing rapids or falling cataracts.

Vague thoughts of final escape came and went; but in such a situation hope could not be sustained.

The thick darkness oppressed the soul; and at length even the glow of the distant volcanoes, which had been gradually diminishing, grew dimmer and fainter, and finally faded out altogether.