The entrance had evidently been closed till very lately by a large column of ice, and we passed over the débris, between rock portals and on a floor of solid grey ice, into a triangular cave of any height the imagination might choose to fix. The entire floor of the cave was of ice, giving the impression of infinite thickness and firmness. A little water stood on it, near the threshold, so limpid that we could not see where it commenced. The base of this triangular floor we found to be 17 feet, and its altitude 30 feet; and though these dimensions may seem comparatively small, the whole effect of the thick mass of ice on which we stood, with the cascades of ice in the corners, and the ice-figures on the walls, and the three sides of the cave passing up into sheer darkness, was exceedingly striking, situated, as it all was, so deep down in the bowels of the earth. The original entrance to the fissure, at the top of the _cheminée_, was, as has been said, at the base of lofty rocks, and we had descended very considerably from the entrance; so that, even without the strange light thrown upon the matter by the small hole overhead, through which we had seen the day struggling to force its way into the cavern, we should have been sure that we were now at an immense distance below the surface. One corner of the cave was occupied by a broad and solid-looking cascade, while another corner showed the opening of a very narrow fissure, curved like one of the shell-shaped crevasses of a glacier. Into this fissure the ice-floor streamed; and Rosset held my coat-tails while I made a few steps down the stream, when the fall became too rapid for further voluntary progress. I let down a stone for 18 feet, when it stuck fast, and would move neither one way nor the other. The upper wall of this fissure was clothed with moss-like ice, and ice of the prismatic structure,--with here and there large scythe-blades, as it were, attached by the sharp edge to the rock, and lying vertically with the heel outwards. One of these was 11 inches deep, from the heel to the rock, and only one-eighth of an inch thick at the thickest part.