He thrust out his hand. I shook it and we walked on silently. We had now gone more than a hundred yards when the scarlet forest thinned, and we walked out on a level stretch of bare white sand. The clear space was perhaps a mile long and half as wide. Along the western side rose a dark precipitous cliff, like that over which the silver fall plunged, with a line of red brush along the top. At the foot was a great sloping bank of talus, scattered with gigantic boulders. The cliff and the lofty crimson forest that rimmed the open space on the other three sides, seemed to reach into the dusky purple of obscurity of the low-hanging sky. Spaced irregularly about the center of the flat were perhaps a dozen low circular metal structures--evidently the mouths of great white metal tubes projecting from the earth. From five of them dense clouds of purple vapor were pouring. * * * * * The Sacrifice We left the shelter of the jungle and quickly approached the nearest of the wells. The metal curbing was about four feet high, around a circular pit some 20 feet in diameter. We leaned over and looked into it. The tube was lit faintly for a few feet down the walls, but we saw no light toward the bottom of the tube. A faint humming sound came up out of the darkness, and I felt a strong current of air flowing down the tube. It was altogether stranger and more terrible than I had anticipated. I doubt that I could have found the courage to descend. "Is the rope long enough?" I whispered. "Yes," he replied in a cautious undertone. "On the day I discovered the place I dropped a pebble in the well and timed its fall with my watch. The depth is just over five hundred feet." I put the end of the cord over the metal rim and paid it out until only enough was left to hitch around my body. With a smile of forced cheerfulness, Austen looked to his pack, knocked out the pipe, and put it in his pocket. "Winfield, my boy, I hope to see you soon again," he said. "It may take only an hour or two to lay my mine and return to the shaft. But of course I know nothing of what I am to encounter. You wait and hold the rope, and if I need to send you any message I will jerk it three times, and you can pull it up. The note will tell when to put it down again for me to climb out. Good-by, my boy. You--"