Estnerdole gave a hoot of relief, and followed it with words. “Dr. LaVerne! How can we help you?”
For several seconds there was no answer, but the tank wavered even more alarmingly. Then the door opened, and the giant figure of the armored alien appeared in the opening. It tottered a moment, then fell outward into the snow. The tank rocked away as the man’s weight left it, swung forward again in a way which would have brought Estnerdole’s heart to his mouth if he had possessed a heart, and then stopped once more.
The Mesklinites swarmed forward with the common intent of dragging the human being away from the dangerous neighborhood, but before they reached him he started crawling under his own power. His voice came haltingly from his helmet speaker. “Stay back—all of you—I can make it—you couldn’t move me in this stuff anyway.”
Estnerdole and two of the others kept coming; with Mesklinites as with other intelligent races, some customs override selfish caution. The three tiny figures swarmed around the struggling monster, trying to speed its faltering trip away from the danger zone, but they promptly found that the teacher had been right; they couldn’t help. It was not that the five hundred kilograms of weight were too much for them—any one of them could have lifted that. The trouble was the footing. A Mesklinite’s legs end in insectlike claws, except for the nippers on the fore and aft pairs; the claws provide excellent traction on the wooden deck of a ship or the hard-packed soil which covers much of Mesklin. But a sand dune or a heap of ammonia snow is a different matter. The students’ efforts to push the huge bulk of their teacher simply drove their own bodies into the loose fluff.
LaVerne was only partly aware of their presence. He had more or less recovered from the shock of his fall, and had seen enough to evaluate the situation fairly well; but he was not really in full possession of his faculties. He knew he was on a sloping surface of loose material, and that the tank was rather likely to roll over on him at any moment; his whole attention was focused on getting out of the way. The warning to the students had been little more than reflexive, like their own move to help him, and he did not follow up the order. He simply crawled as well as the situation permitted. A human observer might have had trouble deciding whether his mode of progress should have been called crawling or swimming, but he did make progress. He never was sure whether it took him five seconds or a whole minute, but presently he found himself on smooth, solid rock with the white slope safely behind him. He relaxed with a sigh, and only slowly became aware of the dozen caterpillarlike figures around him.
With an effort he managed to lever himself to a sitting position. His students waited silently. He took in the nearly buried tank, the cliff in the opposite direction, the rock roof above with sunlight slanting through the jagged hole, and the darkness which swallowed the seemingly endless cavern to
east and west. The Mesklinites were reasonably familiar with human facial expression and tried to read his, but they could make out little in the poor light through the face plate, which was partly obscured by blood from his nose. They waited for him to speak, and were not surprised when his first words formed pertinent questions. “How long did it take you to do that digging job? How long has that fellow been trying to climb the hill?”
Destigmet answered, “Only a few days; we didn’t keep close count.”
“Hmph. He hasn’t gotten very far. I’m reminded of an animal on my own world which traps its prey in pits rather like this—loose stuff at its angle of repose. Climbing such a surface is nearly impossible. What will he do if he gets to the top? That hole is twenty of your body lengths away from the bank.”
“But, Doctor!” pointed out Estnerdole, “the stone itself is not very thick. If we can reach the top, we know the stone comes to an end only a short distance to the south. We can dig our way out from under the edge easily enough.”
“True enough. All right, the rest of you might as well try climbing too. So, for that matter, might I; if I get out on the surface I can call for help instead of having to send a runner.”
“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
yards—let’s see; it looks as through it would land right side up; then onto its right side, then the top, then the left—that should bring it right to my feet. If there’s one more quarter-turn left in it, I’m flat.
LaVeme wondered later how he was able to analyze the matter so calmly as the mass of metal came whispering down on him in its envelope of dusty snow.
Actually it scarcely rolled at all, coming to rest with an ear-shattering clang on its right side. The man had a good heart—he would never have been allowed to serve on Mesklin otherwise—and was able to switch his attention back to his students almost at once; but the switch did his heart little more good than the juggernauting tank had. The Mesklinites were invisible.
For a moment, real fear struck him—intelligent fear based on foresight, not just panic. If those people were gone, he would most certainly not get back to the College. Then little white fountains of dust began to erupt from various points near the bottom of the slope, and one after another the Mesklinites emerged. None of them had been buried deeply enough to matter. All was well.
Except that there seemed no way to get out of the cave.
Ideas flowed from all directions, since the Mesklinites were an imaginative lot; but none of these seemed very practical. Estnerdole suggested that the cave be explored in the east-west directions, on the chance that there might be a more usable way out. The objection to this was that not even the Mesklinites could see in the total darkness which obtained away from the area sunlit from their entry hole. Destigmet proposed cutting climbing notches in the cliff of water ice and reaching the top that way; unfortunately, ice met stone many yards from the hole, and there was no reason to hope that even the natives, insectlike as they appeared to human beings, could possibly crawl inverted along the stone ceiling. LaVerne, conditioned by a childhood on Earth, thought briefly of packing the snow to make a more reliable support and with it actually constructing steps up the slope. Fortunately for his reputation with the Mesklinites, he remembered in time that ammonia, unlike water, is denser in the solid than in the liquid phase. It does not, therefore, tend to melt under pressure; trying to make even a
snowball out of the powdery stuff which had trapped them would be like trying to do it with a handful of sand.
“All I can suggest,” he said at last, “is for some or all of you to start climbing again—maybe farther apart this time, so one person’s avalanche doesn’t involve everyone else. At least the tank won’t be a problem any more. It will be slow, but if even one of you can get to the top, he can go back to the College and get help. I can last here for days, with the air supplies in the tank, so there’s no emergency.”
“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.”