Carefully following the marks, they led into a cross-crevice that took us under Rainy Chamber, and ends there by widening into a circular chamber of about fifty feet width in either direction, and rising to a height of nearly fifty feet in a fine dome.  Down the wall from near the top of the dome there appears to flow a beautiful waterfall showing a variety of colors in the straight lines, as if from refraction.  The fall is, of course, dripstone, and I knew we had found Niagara, although we had gone beyond the reach of the guide’s voice almost at the start.  A huge rock directly under the dome has received the falling drip until it represents a mountain cataract.  These deposits testify to the great age of the chamber they adorn, as they were necessarily not commenced until all heavy flow ceased, and in Crystal Cave the accumulation of dripstone is so slow that it is said six years’ observation can detect no increase whatever.

Several small passages at the floor level gave exit to the great volume of water that evidently at one time entered this crevice, from Rainy Chamber, by the route we followed, and being checked in its course the lower end of the crevice became filled, under pressure; and the low position of the outlets gave this water a whirling motion that in time excavated the dome-shaped room.

No part of Crystal Cave has ever been occupied by a river, but its fissures, opened by the violence of earth movements accompanying nearby volcanic disturbances, have been filled more than once by the inrush of waters which repeatedly submerged the whole Black Hills region.

Following again the marks which guided us into Niagara Room, we soon came within hailing distance of a voice expressive of profound relief; and as we crawled up the sloping passage, over-heated and breathless with the exertion, the guide assured us he was most truly thankful to see us again, as he had never in his life experienced so severe a scare as since it had occurred to him that we had gone beyond the limits of communication without a single match.

He also said I had been where no lady had ever gone before, and took satisfaction in the fact that many men have refused to make the venture with a guide.

Leaving this portion of the cave, by returning as we came, through Suicide Room, Starr Chamber, and Senate Chamber, we crawled along the rocks overhanging a narrow fissure, to reach a ladder at the end, by which we descended to another part of the Catacombs.  Here, after traveling a long distance over uneven floors covered with sharp crystals, as were all surfaces, through large, low rooms, and narrow, crooked passages, constantly assisting the difficult advance with our hands, like monkeys, we finally came to The Grotto, which is probably the most remarkable room in this very remarkable cave.  It is a large room, with much of the irregular ceiling so low that even the small nephew struck his head severely while turning