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.

At the stopover, the incident wasn’t mentioned again, but the Major drew me aside just as I was settling down for sleep. “Peter, I’m worried,” he said slowly.

“McIvers? Don’t worry. He’s not as reckless as he seems—just impatient. We are over a hundred miles behind schedule and we’re moving awfully slow. We only made forty miles this last drive.”

The Major shook his head. “I don’t mean McIvers. I mean the kid.”

“Jack? What about him?”

“Take a look.”

Stone was shaking. He was over near the tractor—away from the rest of us—and he was lying on his back, but he wasn’t asleep. His whole body was shaking, convulsively. I saw him grip an outcropping of rock hard.

I walked over and sat down beside him. “Get your water all right?” I said.

He didn’t answer. He just kept on shaking.

“Hey, boy,” I said. “What’s the trouble?”

“It’s hot,” he said, choking out the words.

“Sure it’s hot, but don’t let it throw you. We’re in really good shape.”

“We’re not,” he snapped. “We’re in rotten shape, if you ask me. We’re not going to make it, do you know that? That crazy fool’s going to kill us for sure—” All of a sudden, he was bawling like a baby. “I’m scared—I shouldn’t be here—I’m scared. What am I trying to prove by coming out here, for God’s sake? I’m some kind of hero or something? I tell you I’m scared—”

“Look,” I said. “Mikuta’s scared, I’m scared. So what? We’ll make it, don’t worry. And nobody’s trying to be a hero.”

“Nobody but Hero Stone,” he said bitterly. He shook himself and gave a tight little laugh. “Some hero, eh?”

“We’ll make it,” I said.

“Sure,” he said finally. “Sorry. I’ll be okay.”

I rolled over, but waited until he was good and quiet. Then I tried to sleep, but I didn’t sleep too well. I kept thinking about that ledge. I’d known from the look of it what it was; a zinc slough of the sort Sanderson had warned us about, a wide sheet of almost pure zinc that had been thrown up white-hot from below, quite recently, just waiting for oxygen or sulfur to rot it through.

I knew enough about zinc to know that at these temperatures it gets brittle as glass. Take a chance like McIvers had taken and the whole sheet could snap like a dry pine board. And it wasn’t McIvers’ fault that it hadn’t.

Five hours later, we were back at the wheel. We were hardly moving at all. The ragged surface was almost impassable—great jutting rocks peppered the plateau; ledges crumbled the moment my tires touched them; long, open canyons turned into lead-mires or sulfur pits.

A dozen times I climbed out of the Bug to prod out an uncertain area with my boots and pikestaff. Whenever I did, McIvers piled out behind me, running ahead like a schoolboy at the fair, then climbing back again red-faced and panting, while we moved the machines ahead another mile or two.

Time was pressing us now and McIvers wouldn’t let me forget it. We had made only about three hundred twenty miles in six driving periods, so we were about a hundred miles or even more behind schedule.

“We’re not going to make it,” McIvers would complain angrily. “That Sun’s going to be out to aphelion by the time we hit the Center—”

“Sorry, but I can’t take it any faster,” I told him. I was getting good and mad. I knew what he wanted, but didn’t dare let him have it. I was scared enough pushing the Bug out on those ledges, even knowing that at least I was making the decisions. Put him in the lead and we wouldn’t last for eight hours. Our nerves wouldn’t take it, at any rate, even if the machines would.

Jack Stone looked up from the aluminum chart sheets. “Another hundred miles and we should hit a good stretch,” he said. “Maybe we can make up distance there for a couple of days.”

The Major agreed, but McIvers couldn’t hold his impatience. He kept staring up at the Sun as if he had a personal grudge against it and stamped back and forth under the sunshield. “That’ll be just fine,” he said. “If we ever get that far, that is.”

We dropped it there, but the Major stopped me as we climbed aboard for the next run. “That guy’s going to blow wide open if we don’t move faster, Peter. I don’t want him in the lead, no matter what happens. He’s right though, about the need to make better time. Keep your head, but crowd your luck a little, okay?”

“I’ll try,” I said. It was asking the impossible and Mikuta knew it. We were on a long downward slope that shifted and buckled all around us, as though there were a molten