"But don't get the idea I climbed down over an icy slope on a rope. I simply sat down and let myself slide. Smooth? There wasn't a crevice or a projection until I reached the bottom and picked myself up." Charley nodded. "I had to lift off my helmet for a minute, to shake off the ice. That's when I shouted and heard the echoes come rolling back. "I'd clamped the helmet back on, and was adjusting my oxygen intake when I happened to glance down at my big, square feet." Charley chuckled. "I've got outsized feet even when I'm as bare as a baby. But I was wearing heavy moon-shoes, and the prints I'd left in the snow were eight inches across! "There was a straight line of prints, as big and square as my own, leading out across the valley--prints I couldn't possibly have made. I'd stumbled around a bit, of course. But I hadn't budged two yards from the base of the slope. "The oddest thing about that single trail of prints was the fact that it started right where I was standing! "An icy wind seemed to blow through me. On the moon you don't slide down a steep slope and land right where someone else has been standing. Not if you're in your right mind, you don't. The moon isn't that thickly populated. "I was badly shaken, I can tell you! But I didn't sit down and brood over it. When you go into a huddle with yourself on the moon you're apt to wind up looking like an ice-carved replica of Rodin's Thinker. "I simply shaded my helmet with my palm, to cut down the starshine, and stared across the valley. The valley was about a mile wide, and as smooth as a skating rink over most of its surface. But about halfway across a big mound of blue-gray sandstone broke the monotony by looming up on the frozen plain like an African termite's nest. * * * * * "Maybe you've seen some pictures of those big nests in travel books. They were usually photographed with seven-foot natives standing beside 'em, to make you realize what insects could accomplish. Old travel books, of course, because Africa is just one big stone highway now. "Those nests were huge, weren't they? If my memory doesn't betray me--some of those nests were twelve feet tall. "Uh ... Uh. But this mound would have dwarfed twenty termite nests in a valley of giants--all tumbled together and piled up in a skyward direction. "As near as I could make out the footprints ran right up to the base of the mound, and stopped there. "Well ... you can be sure I didn't just stand in my own prints goggling up at the stars. I followed that impossible trail--straight out into the valley as fast as I could clump. "It took me about ten minutes to reach the mound. Once or twice I stumbled and almost went sprawling. But whenever I felt the plain slipping out from under me I shot a quick glance at the mound and its sheer massiveness steadied me.