“Rest first,” advised Destigmet. “You can’t be in very good condition yet. You must have been hurt some, if the state of your face plate means anything.”
“All right. I want to think, anyway.” Near-silence fell while the rest of the students began to climb. Two or three, starting just below the stranded tank, had little trouble getting as far as the vehicle; but from there on it was a different matter. The creatures were tiny, some fifteen inches long with split-cylinder bodies an inch and a half in diameter. They were light; their half-pound masses weighed less than a kilogram at Mesklin’s equator. Even that weight, however, sank their tiny legs full-length into the snow. The motion of the short limbs could be inferred from the clouds of white dust which sprayed backward from the small bodies. A hollow formed around each slender form, with material sifting down into it from the front and sides. Behind, it built up into something approaching a level surface, and slowly — very slowly — the Mesklinites followed their fellow uphill. Sometimes one would speed up briefly as he encountered a slightly more firmly packed area; almost as often he would slide back a body length or two, spraying frantic clouds of white dust, before resuming forward motion. Every few seconds a pile of snow behind one of them would collapse and slide downhill, spreading its material out until a new approach to the angle of repose was attained. Minutes — long minutes — passed. Those who had used the tank as a starting point were four or five yards up the slope, not too far behind the one who had started so long before. The rest, whose slipping had started at a lower level, had made little visible progress. The little fans and rivulets of sliding snow, first behind one and then another of the dozen red-and-black figures, were as hypnotic as the patterns in a bonfire; LaVerne had to wrench his attention away from them, suddenly realizing that he had more serious jobs than being a spectator. Slowly and painfully he hoisted himself to his feet. He could manage this at all only with the aid of ingenious lever- and-ratchet systems in the joints of his armor which let him concentrate on one part of the job at a time, and rest frequently without losing what he had gained. Once up, he turned slowly around, clarifying the mental picture he had already developed of the space they had fallen into. It was not too hard to infer how the cavern must have formed. As he had guessed, the layer of water ice under the sandstone had been bared by erosion at the top of the fold which formed the peninsula. The stone must have worn virtually to a knife edge; no wonder it had failed to support the tank’s weight once the underlying ice had gone. Ice was hard enough at Mesklin temperatures to stand mechanical erosion reasonably well, of course, but there was another factor operating here. Each year, as the giant world swung past periastron and the northern hemisphere began its summer, storms started sweeping ammonia snow from the virtually worldwide northern “ice” cap across the equator. This naturally buffered the local temperature near the freezing point of ammonia, which the Mesklinite student scientists had selected as the arbitrary control point for temperature in the scales they were developing. Once the protecting silica had eroded away, the solid ammonia encountered the equally solid water, and liquid resulted. Not only was some heat generated, but the solutions of the two had considerably lower freezing points than either compound alone — a fact which the present crop of students had all faced in their most elementary courses. The ice layer had melted, or dissolved, if one preferred to think of it that way, for fifty or sixty yards back from the edge of the protecting stone. Later in the season when the ammonia had evaporated, this would show a beautiful overhanging ledge extending probably for miles east and west. With luck, LaVerne would be able to see it; since the College had been set up less than half a Mesklin year before, no one had had the chance yet. LaVerne was not so much a scientist as a teacher. Still, he knew enough physical chemistry to wonder about the age of the peninsula — how long it would take the weight of overlying rock to squeeze the ice to the top of the fold and empty the filling from the sandwich. Maybe it had been going on for years already, and if they stayed in the cavern they could measure the creep of the south wall toward them. Maybe— A hoot that was almost deafening even through his helmet jerked his wandering mind back to the current realities. He knew about Mesklinite voices, of course, but no human being ever got used to their more extreme volumes. He turned as quickly as he could from the ice cliff to the slope which his students had been trying to climb. By the time he really got his eyes focused on the scene, the key events had happened; but it was obvious enough what they had been. The snow being kicked downhill by the climbers had been piling up against the tank. The earlier digging had left the vehicle almost without support on its downhill side, and what any thoughtful witness would have predicted had finally occurred. By the time LaVerne completed his turn, the machine was well into a full roll downhill toward him, and almost completely hidden inside a developing avalanche. The hoot, coming from several Mesklinites at once, had been stimulated by their discovery that they were involved in the slide; its upper edge was propagating rapidly toward the top of the slope and was already above the highest of the climbers. The man had little thought for his students just then. The rolling tank was heading straight toward him, and he could not possibly move fast enough to get out of its way. He was several yards from the bottom of the slope, but that might not be far enough. It all depended on whether the tank would reach the stone with enough energy to roll those few
“I’m afraid there is, Doctor,” pointed out Estnerdole. “You can’t get into the tank. It’s lying on its right side, with the door underneath. Unless there is some outside connection you can reach to replenish the oxygen in your armor, you are rather limited in your supply.” The man was silent for several seconds, except for a brief muttering which the students could not make out clearly. “You’re right, Es,” he said at last. “It is an emergency after all, for me. Do you suppose you people are strong enough to turn the tank right side up?” The Mesklinites were somewhat doubtful, but clustered around to try. LaVerne, who shared the exaggerated idea of Mesklinite physical strength which was so common among human beings, was not surprised when the vehicle stirred under their efforts; indeed, he was disappointed when it lofted only a few millimeters. After some seconds it settled back where it had been, and one of the students reappeared from the narrow space underneath. “We can move it, but that’s all. We’d have to get this side up several body lengths before it would rock over the right way, and there’s nothing to stand on.” Destigmet wriggled into view behind the speaker. “I can think of only two things to do, and you’ve already suggested one of them,” he said. “The first is for someone to start climbing again. The other is for us to lift the tank once more, while you pack snow under it to hold it up and let us get a fresh purchase. Maybe we can work it up that way before you run out of air.”
“All right,” agreed LaVerne. “It would be better if I had something to serve as a shovel, but let’s get at it. I’m using oxygen just standing here worrying.” For a while it looked possible, if not really hopeful. Carrying the dusty snow in his armored hands proved impractical, but he found that he could do fairly well pushing a mass of it ahead of him as he crawled — and crawling was far easier than trying to walk. Essentially, he was sweeping rather than carrying. He managed to get what would have been several shovelfuls, if he had had a shovel, against the space at the edge of the tank where the Mesklinites had disappeared once more. At his call they strained upward again, and
