The Cold Equations by Tom Godwin, edited by Eric Flint

ordinary bows," he complained, "the unicorns would be popping up to charge us from all directions."
    "Don't fret," Humbolt consoled him. "This fall, when we come back, they will be."
    They reached the mountain and stopped near its foot where a creek came down, its water high and muddy with melting snows. There they hunted until they had obtained all the meat they could carry. They would see no more game when they went up the mountain's canyons. A poisonous weed replaced most of the grass in all the canyons and the animals of Ragnarok had learned long before to shun the mountain.
    They found the canyon that Craig and his men had tried to explore and started up it. It was there that Craig had discovered the quartz and mica and so far as he had been able to tell the head of that canyon would be the lowest of all the passes over the mountain.
    The canyon went up the mountain diagonally so that the climb was not steep although it was constant. They began to see mica and quartz crystals in the creek bed and at noon on the second day they passed the last stunted tree. Nothing grew higher than that point but the thorny poison weeds and they were scarce.
    The air was noticeably thinner there and their burdens heavier. A short distance beyond they came to a small rock monument; Craig's turn-back point.
    The next day they found the quartz crystals in place. A mile farther was the vein the mica had come from. Of the other minerals Craig had hoped to find, however, there were only traces.
    The fourth day was an eternity of struggling up the now-steeper canyon under loads that seemed to weigh hundreds of pounds; forcing their protesting legs to carry them fifty steps at a time, at the end of which they would stop to rest while their lungs labored to suck in the thin air in quick, panting breaths.
    It would have been much easier to have gone around the mountain. But the Chasm was supposed to be like a huge cavity scooped out of the plateau beyond the mountain, rimmed with sheer cliffs a mile high. Only on the side next to the mountain was there a slope leading down into it.
    They stopped for the night where the creek ended in a small spring. There the snow still clung to the canyon's walls and there the canyon curved, offering them the promise of the summit just around the bend as it had been doing all day.
    The sun was hot and bright the next morning as they made their slow way on again. The canyon straightened, the steep walls of it flattening out to make a pair of ragged shoulders with a saddle between them.
    They climbed to the summit of the saddle and there, suddenly before them, was the other side of the world—and the Chasm.
    Far below them was a plateau, stretching endlessly like the one they had left behind them. But the chasm dominated all else. It was a gigantic, sheer-walled valley, a hundred miles long by forty miles wide, sunk deep in the plateau with the tops of its mile-high walls level with the floor of the plateau. The mountain under them dropped swiftly away, sloping down and down to the level of the plateau and then on, down and down again, to the bottom of the chasm that was so deep its floor was half hidden by the morning shadows.
    "My God!" Barber said. "It must be over three miles under us to the bottom, on the vertical. Ten miles of thirty-three percent grade—if we go down we'll never get out again."
    "You can turn back here if you want to," Humbolt said.
    "Turn back?" Barber's red whiskers seemed to bristle. "Who in hell said anything about turning back?"
    "Nobody," Humbolt said, smiling a little at Barber's quick flash of anger.
    He studied the chasm, wishing that they could have some way of cutting the quartz crystals and making binoculars. It was a long way to look with the naked eye . . . 
    Here and there the chasm thrust out arms into the plateau. All the arms were short, however, and even at their heads the cliffs were vertical. The morning shadows prevented a clear view of much of the chasm and he