“I was reminded on this excursion of what I have read of the Mammoth Caves; if only I had had a yellow flambeau instead of the pervading blue light, and a solid-looking boatman with an oar instead of a scuttle-faced Selenite working an engine at the back of the canoe, I could have imagined I had suddenly got back to earth. The rocks about us were very various, sometimes black, sometimes pale blue and veined, and once they flashed and glittered as though we had come into a mine of sapphires. And below one saw the ghostly phosphorescent fishes flash and vanish in the hardly less phosphorescent deep. Then, presently, a long ultramarine vista down the turgid stream of one of the channels of traffic, and a landing-stage, and then, perhaps, a glimpse up the enormous crowded shaft of one of the vertical ways.