Before he could gather himself up, Harry followed, and he too sprawled at full length, neither receiving any injury, and both assuming the perpendicular almost at the same moment. The fear of Little Rifle was that by plunging through the feathery sheet, and temporarily breaking it, they had dissolved it altogether, and failing to reunite, it would leave not only the rock upon which they stood, but themselves, in full view of the Blackfeet, as soon as they should descend the rocks and place themselves below the falls. But the screen instantly resumed its normal place, and spread over them like a fan of the thinnest glass, shutting them in, but permitting them to look through upon the outer world. Its transparency, or rather its texture, however, was not like that of a perfect window-pane, but it was faulty, abounding with tremulous nebulæ here and there that gave a fanciful, grotesque imagery to the objects upon which the eye rested, and that as a consequence, made the picture of themselves equally untrue to nature. Still, although they had reasonably increased their chances of eluding the Blackfeet, they were in danger, so long as they maintained their present position, and both cast about to discover what their facilities were in the way of a further retreat. The result was better than they dared to hope. The sheet of water that poured over their heads was fully a hundred feet in width, and the black, slippery rock stretched clean across beneath it, with a width varying from ten to a dozen feet. The instant Little Rifle discovered this gratifying fact, he began picking his way carefully along, closely followed by Harry. When they had reached the center, they paused by a common instinct, feeling that they could not increase their chance of safety by going further; and here, as they stood side by side, they looked upon the scene with emotions of wonder, amazement and awe. Above them, to a great height, the black, dripping rocks extended like the jagged irregular roof of some cavern, gradually making their way outward, until they formed the ledge over which the entire river swept in its resistless majesty. It may be said indeed that they stood in a cavern, one side of which was composed of the wet, inky rocks, and the other was the volume of water, converging both in front and back of them, so that the open space resembled a cone in shape. Looking upward the mighty mass of water had a deep emerald tinge, like melted glass, and through its translucent depth, the sunlight could only partially penetrate, so that they were enshrouded in a sort of misty twilight. To the left, as they picked their way along the ledge, this volume was white, foamy and impenetrable to the eye, and looking down, the boiling, tumbling, roaring, seething battle of the water was of such an appalling nature as to make the strongest man shiver and draw back with affright, as though he had caught a glimpse of the Plutonian regions.