It was a grueling eight hours and we slept poorly. Back in the Bug again, we moved still more slowly—edging out on a broad flat plateau, dodging a network of gaping surface cracks—winding back and forth in an effort to keep the machines on solid rock. I couldn’t see far ahead, because of the yellow haze rising from the cracks, so I was almost on top of it when I saw a sharp cut ahead where the surface dropped six feet beyond a deep crack. I let out a shout to halt the others; then I edged my Bug forward, peering at the cleft. It was deep and wide. I moved fifty yards to the left, then back to the right. There was only one place that looked like a possible crossing; a long, narrow ledge of gray stuff that lay down across a section of the fault like a ramp. Even as I watched it, I could feel the surface crust under the Bug trembling and saw the ledge shift over a few feet. The Major’s voice sounded in my ears. “How about it, Peter?” “I don’t know. This crust is on roller skates,” I called back. “How about that ledge?” I hesitated. “I’m scared of it, Major. Let’s backtrack and try to find a way around.” There was a roar of disgust in my earphones and McIvers’ Bug suddenly lurched forward. It rolled down past me, picked up speed, with McIvers hunched behind the wheel like a race driver. He was heading past me straight for the gray ledge. My shout caught in my throat; I heard the Major take a huge breath and roar: “Mac! _stop that thing_, you fool!” and then McIvers’ Bug was out on the ledge, lumbering across like a juggernaut. The ledge jolted as the tires struck it; for a horrible moment, it seemed to be sliding out from under the machine. And then the Bug was across in a cloud of dust, and I heard McIvers’ voice in my ears, shouting in glee. “Come on, you slowpokes. It’ll hold you!” Something unprintable came through the earphones as the Major drew up alongside me and moved his Bug out on the ledge slowly and over to the other side. Then he said, “Take it slow, Peter. Then give Jack a hand with the sledges.” His voice sounded tight as a wire. Ten minutes later, we were on the other side of the cleft. The Major checked the whole column; then he turned on McIvers angrily. “One more trick like that,” he said, “and I’ll strap you to a rock and leave you. Do you understand me? _One more time_—” McIvers’ voice was heavy with protest. “Good Lord, if we leave it up to Claney, he’ll have us out here forever! Any blind fool could see that that ledge would hold.” “_I_ saw it moving,” I shot back at him. “All right, all right, so you’ve got good eyes. Why all the fuss? We got across, didn’t we? But I say we’ve got to have a little nerve and use it once in a while if we’re ever going to get across this lousy hotbox.” “We need to use a little judgment, too,” the Major snapped. “All right, let’s roll. But if you think I was joking, you just try me out once.” He let it soak in for a minute. Then he geared his Bug on around to my flank again.