Night supervened with the suddenness of a death which has been looked for, but which is at last a surprise. Shadow after shadow crept down the walls of the chasm, blurred its projections, darkened its faces, and crowded its recesses. The line of sky, seen through the jagged and sinuous opening above, changed slowly to gloom and then to blackness. There was no light in this rocky intestine of the earth except the red flicker of the camp-fire. It fought feebly with the powers of darkness; it sent tremulous despairing flashes athwart the swift ebony river; it reached out with momentary gleams to the nearer facades of precipice; it reeled, drooped, and shuddered as if in hopeless horror. Probably, since the world began, no other fire lighted by man had struggled against the gloom of this tremendous amphitheatre. The darknesses were astonished at it, but they were also uncomprehending and hostile. They refused to be dissipated, and they were victorious. After two hours a change came upon the scene. The moon rose, filled the upper air with its radiance, and bathed in silver the slopes of the mountains. The narrow belt of visible sky resembled a milky way. The light continued to descend and work miracles. Isolated turrets, domes, and pinnacles came out in gleaming relief against the dark-blue background of the heavens. The opposite crest of the cañon shone with a broad illumination. All the uncouth demons and monsters of the rocks awoke, glaring and blinking, to menace the voyagers in the depths below. The contrast between this supereminent brilliancy and the sullen obscurity of the subterranean river made the latter seem more than ever like Styx or Acheron. The travellers were awakened in the morning by the trumpetings of the cataract. They embarked and dropped down the stream, hugging the northern rampart and watching anxiously. Presently there was a clear sweep of a mile; the clamor now came straight up to them with redoubled vehemence; a ghost of spray arose and waved threateningly, as if forbidding further passage. It was the roar and smoke of an artillery which had thundered for ages, and would thunder for ages to come. It was a voice and signal which summoned reinforcements of waters, and in obedience to which the waters charged eternally.