In the rock where the fissure ends at Révaillon is an opening like a vast yawning mouth, the roof of which forms an almost perfect dome. Adown this a stream trickles towards the end of summer, but plunges madly and with a frightful roar in winter and spring. The steep sides of the narrow ravine are densely wooded, and the light is very dim at the bottom when the sun is not overhead. I made my first attempt to descend the dark passage in the early summer, but there was too much water, and I was soon obliged to retreat. One afternoon in October I returned with a companion, and we took with us a rope and plenty of candles. We carried the rope in view of possible difficulties in the shape of rocks inside the cavern, for it should be borne in mind that in _gouffres_ of this character the stream frequently descends by a series of cascades. The weather was very sultry, and the sky towards the west was of a slaty blue. A fierce storm was threatening, but we paid no attention to it--a mistake which others bent on exploring caverns where streams still flow should be warned against. There is probably no force in nature more terrible, or which makes a man's helplessness more miserably felt, than water suddenly rushing towards him when he is underground.
The sun was still shining, however, when we reached the Gouffre de Révaillon and descended into the ravine over roots of trees coiling upon the moss like snakes, some arching upward as if about to spring at the throat of those who disturbed the elfish solitude. At our coming there rose from the great rock such a multitude of jackdaws that for some seconds they darkened the air. With harsh screams the birds soared higher and higher above their fortress, which they had possessed for ages in perfect security. We reached the bed of the stream, where scattered threads of water tinkled as they fell over huge blocks into little pools below, and then went whispering on their way towards the darkness. At the botton of a long slant of greenish slimy stone, patched here and there with moss, I stopped a few minutes, feeling that I could not grasp without an effort the deep gloom and grandeur of my surroundings. The jackdaws had all flown away, and there was no sound now but the tinkle and gurgle of the water. Great snails crawled upon the tufts of rank grass wet with the autumnal dews that the sun had failed to dry, and upon the glistening hart's-tongue ferns, and they looked just the kind of snails that witches would collect to make a hell-broth. Dark ivy hung down from the rocks, and under the vaulted entrance of the cavern was a clump of elders, very sinister-looking, and giving forth when touched an evil narcotic odour. Near these forlorn shrubs was a solitary plant of angelica, now woebegone, its fringed leaves drooping, waiting for the rising water to wash it into the darkness. There were willow-herbs still in bloom, but the crane's-bill struggled with the gloom farther than any other flowering plant, and its bright little purple lamps shone in the very mouth of Night. Gnats there were too, spinning in the semi-darkness, now sinking, now rising, keeping together, a merry band of musicians, each with a small flute, piping perhaps to the little goblins that swung on spiders' webs, and slept upon the fronds of the ferns.