How it first became ignited is, of course, impossible to say -- probably, I should think, from some spontaneous explosion of mephitic gases.
As soon as we had got some things together and shaken ourselves together a little, we set to work to make out where we were now.
I have said that there was light above, and on examination we found that it came from the sky.

Our river that was, Sir Henry said, a literal realization of the wild vision of the poet {Endnote 10}, was no longer underground, but was running on its darksome way, not now through 'caverns measureless to man', but between two frightful cliffs which cannot have been less than two thousand feet high.

So high were they, indeed, that though the sky was above us, where we were was dense gloom -- not darkness indeed, but the gloom of a room closely shuttered in the daytime.
Up on either side rose the great straight cliffs, grim and forbidding, till the eye grew dizzy with trying to measure their sheer height.
The little space of sky that marked where they ended lay like a thread of blue upon their soaring blackness, which was unrelieved by any tree or creeper.

Here and there, however, grew ghostly patches of a long grey lichen, hanging motionless to the rock as the white beard to the chin of a dead man.

It seemed as though only the dregs or heavier part of the light had sunk to the bottom of this awful place.