by Hal Clement
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 en
ough 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.”
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 as quickly as he could he pushed the material into the widening space. “That’s all,” he reported when he had done his best, and the students relaxed again. So did the pile of snow. LaVerne, optimistic by nature, felt sure that the tank had not settled quite back to its original position, and kept trying; but after an hour which left him more exhausted than he had ever felt in his three Earth years on Mesklin, he had to admit that the idea was qualitatively sound but quantitatively inadequate.
During those days, the student who was trying to climb the slope had made little progress. Once he had gotten nearly a third of the way before sliding most of the way back in a smother of white dust; four or five times he had lost the fight in the first yard or two. The rest of his attempts came between those limits.
But it finally became evident that the man’s air was not going to be the real limiting factor. Destigmet pointed out another one to him. “Some time ago, Doctor, one of your fellows taught us about a fact he claimed was very basic—the Law of Conservation of Energy. If I have the terminology right, we can apply very large forces by your standards, but as that law should tell you, there is a limit to the amount of work we can do without food. None of us expected to need food in this class, and we brought none with us.”
One of the others cut in. “Won’t people from the College start looking for us anyway? This class should have been over days ago.”
LaVerne frowned invisibly behind the blood-stained face plate, which he had no means of cleaning. “They’ll be looking, but finding us will be another story,” he said. “They’d expect to see the tank miles away on the smooth surface of the peninsula. When they don’t, they’ll think we got swept into the sea, or went off to the forest country for some reason. They won’t look over this area closely enough to find the hole we left, I suspect. It’s possible we’ll get out of this with their help, but don’t count on it.”
Estnerdole suddenly became excited. “Why not build a tower we can climb, with the water ice from the cliff? We can chip it out easily enough without tools, or even melt it out with the snow—no, that wouldn’t leave us any to work with, but—” His voice trailed off as more difficulties became apparent to him.
LaVerne was pessimistic, too, after the just-completed practical demonstration of how much material would be needed even to prop up the tank. Then he brightened. “We could use the ice to get this machine upright—big chunks of it would be more practical and easier to move than the snow. Of course, even that doesn’t get us any closer to getting out of here; the tank certainly isn’t going to climb this sandhill even if I get into it. If only—” He paused, and the ensuing silence stretched out for long seconds. Even with the man hidden in his armor, the listeners got the impression that something had happened. Then he spoke again, and his tone confirmed the suspicion. “Thanks, Es. That does it. Start digging ice, gentlemen. We’ll be out of here in a couple of hours!”
Actually, it took less than three days.
“You look bothered,” remarked Thomasian, LaVerne’s department head. “Delayed shock from your narrow escape, or what?”
“It wasn’t that narrow,” replied the teacher. “I had hours of air still in the suit when the spinner picked us up, and we could have worked the tank upright to get at more if I had needed it. You’d have searched the area closely enough to find that hole sooner or later.”
“Later would probably have been too late—and the really narrow squeak I was thinking of was the fall. Fifteen meters under three gees—sooner you than me. If it hadn’t been for that snow bank, we’d have had to cut you out of the flattened remains of that tank—not that it would have been worth doing. Of course any of your students should have been able to think of tossing pieces of water ice over the slope, especially after you’d discussed with them why the cuesta was so deeply undercut. So should you, for that matter—”
“Hogback,” LaVerne responded almost automatically. “Sure, all sorts of ideas are obvious afterward. At the time, I wasn’t quite sure that this one would work, even if I did sound as enthusiastic as I could and even though I did have experience to go by. Still, I was afraid it would simply melt holes in the slope; but it went fine. The liquid formed where the two ices met just soaked into the surrounding snow, spreading out and diluting the water ice until the mixture’s m
elting point came up to the local temperature again—and froze into a continuous mass. It was hard enough for Estnerdole to climb out and go for help in less than an hour, I’d guess; I didn’t actually time it.”
“What was the experience you could go by? And if it was so easy and safe, what’s bothering you?”
“The same thing. A teaching problem. They claim that Mesklinite psychology is enough like ours for teaching techniques to be about the same, effectively. They expect us to—er—‘relate’ new facts to known experience.”
“Of course. So?”
“So the experience in question should obviously be one familiar to the students, not just the teacher. What sparked this idea for me was the memory of sugar getting lumpy in the bowl when it gets damp. You know, I’m just a little shaky on the local biochemistry, chief—tell me: what do Mesklinites use for coffee, and what do they put in it?”
1974
MISTAKEN FOR GRANTED
The stars said die . . . and they only seemed to lie!
I
PEOPLE can usually get used to the weightlessness of space flight during the days or weeks it takes to cross from one world to another. In a long orbit it is easy to convince oneself that one’s ship is not about to fall onto anything, even though the sensation of weightlessness is that of endless falling. There simply is nothing visible nearby to hit. Of course, travelers have had nervous breakdowns in spaceships too badly designed to let them see out.