We set off around just outside the white metal wall. The snow and ice was irregularly banked against it, but the wall itself was smooth and unbroken. We had limped along for some two miles, or more than halfway around the amazing lake of light. I had begun to doubt that we would find anything. Then we came to a square metal tower, ten feet on a side, that rose just outside the silvery wall, to a level with its top. The ice was low here; the tower rose twenty feet above its unequal surface. We found metal flanges riveted to its side, like the steps of a ladder. They were most inconveniently placed, nearly four feet apart; but we were able to climb them, and to look down the shaft. It was a straight-sided pit, evidently some hundreds of feet deep. We could see a tiny square of light at the bottom, very far away. The flanges ran down the side forming the rungs of a ladder that gave access to whatever lay at the bottom. Without hesitation, Ray climbed over the side and started down. I followed him, feeling a great relief in getting out of the freezing wind. Ray had the rifle and ammunition strapped to his back, along with a few other articles; and I had a small pack. We had abandoned the sledge, with the useless stove and the most of our instruments. Our food was all gone. The metal flanges were fully four feet apart, and it was not easy to scramble down from one to another; certainly not easy for one who was cold, hungry, thirsty, worn out with a week of exhausting marches, and suffering the torture of frozen feet. "You know, this thing was not built by men," Ray observed. "Not built by men? What do you mean?" "Men would have put the steps closer together. Jim, I'm afraid we are up against something--well--that we aren't used to." "If men didn't build this, what did?" I was astounded. "Search me! This continent has been cut off from the rest of the world for geologic ages. Such life as has been found here is not common to the rest of the earth. It is not impossible that some form of life, isolated here, has developed intelligence and acquired the power to erect that cone of light--and to burn the wing off a metal airplane." My thoughts whirled madly as we clambered down the shaft. * * * * * It must have taken us an hour to reach the bottom. I did not count the steps, but it must have been at least a thousand feet. The air grew rapidly warmer as we descended. We both took off most of our heavy fur garments, and left them hanging on the rungs. I was rather nervous. I felt the nearness of an intelligent, hostile power. I had a great fear that the owners of those steps would use them to find us, and then crush us ruthlessly as they had brought down Meriden's plane.