The little square of white light below grew larger. Finally I saw Ray swing off and stand on his feet in a flood of white radiance below me. The air was warm, moist, laden with a subtle unfamiliar fragrance that suggested growing things. Then I stood beside Ray. We stood on the bare stone floor of a huge cavern. It must have been of volcanic origin. The walls glistened with the sparkling smoothness of volcanic glass. It was a huge space. The black roof was a hundred feet high, or more; the cave was some hundreds of feet wide. And it sloped away from us into dim distance as though leading into huger cavities below. The light that shone upon us came from an amazing thing--a fall of liquid fire. From the roof plunged a sheer torrent of white brilliantly luminous fluid, falling a hundred feet into a shimmering pool of moon-flame. Shining opalescent mists swirled about it, and the ceaseless roar of it filled the cave with sound. It seemed that a stream of the phosphorescent stuff ran off down the cave from the pool, to light the lower caverns. "Very clever!" said Ray. "They make the stuff up there at the cone and run it in here to see by." "This warm air feels mighty good," I remarked, pulling off another garment. Ray sniffed the air. "A curious odor. Smells like something growing. Where anything is growing there ought to be something to eat. Let's see what we can find." Only black obsidian covered the floor about us. Cautiously we skirted the overflowing pool of white fire, and followed down the stream of it that flowed toward the inner cavern. We had gone but a few hundred yards when suddenly Ray stopped me with a hand on my arm. "Lie flat!" he hissed. "Quick!" He dived behind a huge mass of fire-born granite. I flung myself down beside him. "Something is coming up the trail by the shining river. And it isn't a man! It's between us and the light; we should be able to see it." * * * * * Soon I heard a curious scraping sound, and a little tinkle of metal. I caught a whiff of a powerful odor--a strange, fishy odor--so strong that it almost knocked me down. The thing that made the scraping and the tinkle and the smell came into view. The sight of it sickened me with horror. It was far larger than a man; its body was heavy as a horse's, but nearer the ground. In form it suggested a huge crab, though it was not very much like any crustacean I had ever seen. It was mostly red in color, and covered with a huge scarlet shell. It had five pairs of limbs. The two forward pairs had pinchers, seemingly used as hands; it scraped along on the other three pairs. Yard-long antennae, slender and luminously green, wavered above a grotesque head. The many facets of compound eyes stood on the end of foot-long stalks.