by Hal Clement
“I’ve been doing my best all along. It’s a nuisance having this crop up when we were so close to home plate. I just hope he doesn’t give us up as a bad job this close to the end; he still doesn’t believe everything we say, you know. I wish someone could explain that high-horizon illusion to his — and my — satisfaction; that might shake him out of the notion that his world is a bowl, and our claim to come from another is at least fifty percent superstition on our part.”
“You mean you don’t understand why it looks higher?” one of the meteorologists exclaimed in a shocked tone. “Not in detail, though I realize the air density has something to do with it.”
“But it’s simple enough—”
“Not for me.”
“It’s simple for anyone. You know how the layer of hot air just above a road on a sunny day bends sky light back upward at a slight angle, since the hot air is less dense and the light travels faster in it; you see the sky reflection and tend to interpret it as water. You get more extensive mirages sometimes even on Earth, but they’re all based on the same thing — a ‘lens’ or ‘prism’ of colder or hotter air refracts the light. It’s the same here, except the gravity is responsible; even hydrogen decreases rapidly in density as you go up from Mesklin’s surface. The low temperature helps, of course.”
“All right if you say so; I’m not a—” Lackland got no chance to finish his remark; Rosten cut in abruptly and grimly. “Just how fast does this density drop off with altitude?” The meteorologist drew a slide rule from his pocket and manipulated it silently for a moment. “Very roughly, assuming a mean temperature of minus one-sixty, it would drop to about one percent of its surface density at around fifteen or sixteen hundred feet.” A general stunned silence followed his words. “And — how far would it have dropped at — say—three hundred feet?” Rosten finally managed to get the question out. The answer came after a moment of silent lip movement. “Again very roughly, seventy or eighty percent — probably rather more.” Rosten drummed his fingers on the table for a minute or two, his eyes following their motions; then he looked around at the other faces. All were looking back at him silently. “I suppose no one can suggest a bright way out of this one; or does someone really hope that Barlennan’s people can live and work under an air pressure that compares to their normal one about as that at forty or fifty thousand feet does to ours?”
“I’m not sure.” Lackland frowned in concentration, and Rosten brightened a trifle. “There was some reference a long time ago to his staying under water — excuse me, under methane — for quite a while, and swimming considerable distances. You remember those river-dwellers must have moved the Bree by doing just that. If it’s the equivalent of holding breath or a storage system such as our whales use, it won’t do us any good; but if he can actually get a fair part of the hydrogen he needs from what’s in solution in Mesklin’s rivers and seas, there might be some hope.” Rosten thought for a moment longer. “All right. Get your little friend on the radio and find out all he knows himself about this ability of his. Rick, look up or find out somehow the solubility of hydrogen in methane at eight atmospheres pressure and temperatures between minus one forty-five and one eighty-five Centigrade. Dave, put that slide rule back in your pocket and get to a calculator; get as precise a value of the hydrogen density on that cliff top as physics, chemistry, math, and the gods of good weather men will let you. Incidentally, didn’t you say there was a drop of as much as three atmospheres in the center of some of those tropical hurricanes? Charlie, find out from Barlennan whether and how much he and his men felt that. Let?s go.? The conference broke up, its members scattering to their various tasks. Rosten remained in the screen room with Lackland, listening to his conversation with the Mesklinite far below. Barlennan agreed that he could swim below the surface for long periods without trouble; but he had no idea how he did it. He did not breathe anyway, and did not experience any feeling comparable to the human sense of strangulation when he submerged. If he stayed too long and was too active the effect was rather similar to sleepiness, as nearly as he could describe it; if he actually lost consciousness, however, it stopped there; he could be pulled out and revived as much later as anyone cared as long as he didn’t starve in the meantime. Evidently there was enough hydrogen in solution in Mesklin’s seas to keep him alive, but not for normal activity. Rosten brightened visibly. “There is no discomfort of the sort you suggest in the middle of the worst storms I have ever experienced,” the captain went on. “Certainly no one was too weak to hold on during that one which cast us on the island of the gliders — though we were in its center for only two or three minutes, of course. What is your trouble? I do not understand what all these questions are leading to.” Lackland looked to his chief for permission, and received a silent nod of affirmation. “We have found that the air on top of this cliff, where our rocket is standing, is very much thinner than at the bottom. We doubt seriously that it will be dense enough to keep you and your people going.”
“But that is only three hundred feet; why should it change that much in such a short distance?”
“It’s that gravity of yours; I’m afraid it would take too long to explain why, but on any world the air gets thinner as you go higher, and the more the gravity the faster that change. On your world the conditions are a trifle extreme.”
“But where is the air at what you would call normal for this world?”
“We assume at sea level; all our measures are usually made from that reference.” Barlennan was thoughtful for a little while. “That seems silly; I should think you’d want a level that stayed put to measure from. Our seas go up and down hundreds of feet each year — and I’ve never noticed any particular change in the air.”
“I don’t suppose you would, for several reasons; the principal one is that you would be at sea level as long as you were aboard the Bree, and therefore at the bottom of the atmosphere in any case. Perhaps it would help you to think of this as a question of what weight of air is above you and what weight below.”
“Then there is still a catch,” the captain replied. “Our cities do not follow the seas down; they are usually on the seacoast in spring and anywhere from two hundred miles to two thousand inland by fall. The slope of the land is very gentle, of course, but I am sure they are fully three hundred feet above sea level at that time.? Lackland and Rosten stared silently at each other for a moment; then the latter spoke. “But you’re a lot farther from the pole in your country — but no, that’s quibbling. Even if gravity were only a third as great you’d be experiencing tremendous pressure changes. Maybe we’ve been taking nova precautions for a red dwarf.” He paused for a moment, but the Mesklinite made no answer. “Would you be willing, then, Barlennan, to make at least an attempt to get up to the plateau? We certainly will not insist on your going on if it proves too hard on your physical make-up, but you already know its importance to us.”
“Of course I will; we’ve come this far, and have no real reason to suppose what’s coming will be any worse than what’s past. Also, I want …” He paused briefly, and went on in another vein. “Have you yet found any way of getting up there, or is your question still hypothetical?” Lackland resumed the human end of the conversation. “We have found what looks like a way, about eight hundred miles upstream from your present position. We can’t be sure you can climb it; it resembles a rock fall of very moderate slope, but we can’t tell from our distance how big the rocks may be. If you can’t get up there, though, I’m afraid you just can’t get up at all. The cliff seems to be vertical all around the plateau except for that one point.”
“Very well, we will head upstream. I don’t like the idea of climbing even small rocks here, but we’ll do our best. Perhaps you will be able to give suggestions when you can see the way through the vision sets.”
“It will take you a long time to get there, I’m afraid.”
“Not too long; for some reason there is a wind along the cliff in the direction we wish to go. It has not changed
in direction or strength since we arrived several score days ago. It is not as strong as the usual sea wind, but it will certainly pull the Bree against the current — if the river does not grow too much swifter.”
“This one does not grow too much narrower, at any rate, as far as you will be going. If it speeds up, it must be because it grows shallower. All we can say to that is that there was no sign of rapids on any of the pictures.”
“Very well, Charles. We will start when the hunting parties are all in.” One by one the parties came back to the ship, all with some food but none with anything interesting to report. The rolling country extended as far in all directions as anyone had gone; animals were small, streams scarce, and vegetation sparse except around the few springs. Morale was a trifle low, but it improved with the news that the Bree was about to travel again. The few articles of equipment that had been disembarked were quickly reloaded on the rafts, and the ship pushed out into the stream. For a moment she drifted seaward, while the sails were being set; then they filled with the strangely steady wind and she bore up against the current, forging slowly but steadily into unknown areas of the hugest planet man had yet attempted to explore.
16: VALLEY OF WIND
Barlennan rather expected the riverbanks to become more barren as his ship ascended the stream, but if anything, the reverse was the case. Clumps of sprawling, octopuslike growths hugged the ground at either bank, except where the cliff on his left crowded the river too closely to leave them room. After the first hundred miles from the point where they had waited, several streams were seen emptying into the main course; and a number of the crewmen swore they saw animals slinking among the plants. The captain was tempted to land a hunting party and await its return, but two considerations decided him against it. One was the wind, which still blew steadily the way he wanted to go; the other was his desire to reach the end of the journey and examine the miraculous machine the Flyers had set down and lost on the polar wastes of his world. As the journey progressed, the captain grew more and more astonished at the wind; he had never before known it to blow steadily for more than a couple of hundred days in any direction. Now it was not merely maintaining direction but was turning to follow the curve of the cliff, so that it was always practically dead astern. He did not actually let the watch on deck relax completely, but he did not object when a man turned his attention away from his section of rigging for a day or so. He himself had lost count of the number of days since it had been necessary to trim sails. The river retained its width, as the Flyers had foretold; as they had also intimated was possible, it grew shallower and swifter. This should have slowed the Bree down, and actually did so; but not as much as it might have, for the wind began also to increase. Mile after mile went by, and day after day; and the meteorologists became frantic. Imperceptibly the sun crept higher in its circles about the sky, but much too slowly to convince those scientists that it was responsible for the increased wind force. It became evident to human beings and Mesklinites alike that something about the local physiography must be responsible; and at long last Barlennan became confident enough to stop briefly and land an exploring and hunting party, sure that the wind would still be there when he re-embarked. It was, and the miles flowed once more under the Bree’s rafts. Eight hundred miles, the Flyers had said. The current of the river made the log indication much more than that, but at last the break that had been foretold appeared in the wall of rock, far ahead of them. For a time the river flowed straight away from it, and they could see it in profile — a nearly straight slope, angling up at about twenty degrees, projecting from the bottom fifty feet of the cliff. As they approached, the course of the stream bent out away from the wall at last, and they could see that the slope was actually a fan-shaped spill radiating from a cleft less than fifty yards wide. The slope grew steeper within the cut, but might still be climbable; no one could tell until they were close enough to see what sort of debris composed the spill itself. The first near view was encouraging; where the river touched the foot of the slope, it could be seen to be composed of pebbles small even by the personal standards of the crew members. If they were not too loose, climbing should be easy. Now they were swinging around to a point directly in front of the opening, and as they did so the wind at last began to change. It angled outward from the cliff, and its speed increased unbelievably. A roar that had sounded as a faint murmur for the last several days in the ears of crewmen and Earthmen alike now began to swell sharply, and as the Bree came directly opposite the opening in the rock the source of the sound became apparent. A blast of wind struck the vessel, threatening to split the tough fabric of her sails and sending her angling across the stream away from the wall of rock. At the same instant the roar increased to almost explosive violence, and in the space of less than a minute the ship was struggling in a storm that vied with any she had encountered since leaving the equator. It lasted only moments; the sails had already been set to catch a quartering wind, and they put enough upstream motion into the ship’s path to carry her across the worst of it before she could run aground. Once out of it, Barlennan hastily turned his vessel to starboard and ran her across the short remaining distance to shore while he collected his wits. This accomplished, he did what was becoming a habit in unfamiliar situations; he called the Earthmen and asked for an explanation. They did not disappoint him; the voice of one of the weather men answered promptly, vibrant with the overtones the captain had learned to associate with human pleasure. “That accounts for it, Barl! It’s the bowl shape of that plateau! I should say that you’d find it easier to get along up there than we had believed. I can’t see why we didn’t think of it before!”
“Think of what?” The Mesklinite did not actually snarl, but his puzzlement showed clearly to the crew members who heard him. “Think what a place like that could do in your gravity, climate, and atmosphere. Look: winter in the part of Mesklin you know — the southern hemisphere — coincides with the world’s passage of its closest point to the sun. That’s summer in the north, and the icecap boils off?that?s why you have such terrific and continual storms at that season. We already knew that. The condensing moisture?methane?whatever you want to call it?gives up its heat and warms the air in your hemisphere, even though you don?t see the sun for three or four months. The temperature probably goes up nearly to the boiling point of methane?around minus one forty-five at your surface pressure. Isn?t that so? Don?t you get a good deal warmer in winter?? “Yes,” admitted Barlennan. “Very well, then. The higher temperature means that your air doesn’t get thin so rapidly with altitude — you might say the whole atmosphere expands. It expands, and pours over the edge into that bowl you’re beside like water into a sinking soup plate. Then you pass the vernal equinox, the storms die out, and Mesklin starts moving away from the sun. You cool off — right? — and the atmosphere shrinks again; but the bowl has a lot caught inside, with its surface pressure now higher than at the corresponding level outside the bowl. A lot of it spills over, of course, and tends to flow away from the cliff at the bottom — but gets deflected to the left by the planet’s spin. That’s most of the wind that helped you along. The rest is this blast you just crossed, pouring out of the bowl at the only place it can, creating a partial vacuum on either side of the cleft, so that the wind tends to rush toward it from the sides. It’s simple!”
“Did you think of all that while I was crossing the wind belt?” asked Barlennan dryly. “Sure — came to me in a flash. That’s why I’m sure the air up there must be denser than we expected. See?”
“Frankly, no. However, if you are satisfied I’ll accept it for now. I’m gradually coming to trust the knowledge of you Flyers. However, theory or no theory, what does this mean to us practically? Climbing the slope in the teeth of that wind is not going to be any joke.”
“I’m afraid you’ll have to. It will probably die down eventually, but I imagine it will be some months before the bowl empties — perhaps a couple of Earthly years. I think, if it’s at all possible for you,
Barl, it would be worth attempting the climb without waiting.” Barlennan thought. At the Rim, of course, such a hurricane would pick up a Mesklinite bodily and drive him out of sight in seconds; but at the Rim such a wind could never form, since the air caught in the bowl would have only a tiny fraction of its present weight. That much even Barlennan now had clear. “We’ll go now,” he said abruptly to the radio, and turned to give orders to the crew. The Bree was guided across the stream — Barlennan had landed her on the side away from the plateau. There she was dragged well out of the river and her tie lines secured to stakes — there were no plants capable of taking the desired load growing this close to the landslide. Five sailors were selected to remain with the ship; the rest harnessed themselves, secured the draglines of their packs to the harness, and started at once for the slope. For some time they were not bothered by the wind; Barlennan had made the obvious approach, coming up the side of the fan of rubble. Its farthest parts, as they had already seen, were composed of relatively fine particles — sand and very small pebbles; as they climbed, the rock fragments grew constantly larger. All could understand the reason for this; the wind could carry the smallest pieces farthest, and all began to worry a trifle about the size of the rocks they would have to climb over in the cut itself. Only a few days were consumed in reaching the side of the wall’s opening. The wind was a little fresher here; a few yards on, it issued from behind the corner with a roar that made conversation ever harder as they approached. Occasional eddies struck them, giving a tiny taste of what was to come; but Barlennan halted for only a moment. Then, making sure that his pack was close behind him and securely attached to his harness, he gathered himself together and crawled into the full blast of the wind. The others followed without hesitation. Their worst fears failed to materialize; climbing individual boulders was not necessary. Such huge fragments were present, indeed, but the downhill side of each was nearly covered by a ramp of finer material that had been swept into the relatively sheltered area by the everlasting wind. The ramps overlapped to a great extent, and where they did not it was always possible to travel across the wind from one to another. Their way was tortuous, but they slowly climbed. They had to modify the original idea that the wind was not really dangerous. One sailor became hungry, paused in what he thought was shelter, and attempted to take a piece of food from his pack; an eddy around his sheltering rock, caused probably by his very presence which disturbed the equilibrium attained after months and years of steady wind, caught in the open container. It acted like a parachute, snatched its unfortunate owner out of his shelter and down the slope. He was gone from sight in a cloud of freshly disturbed sand in moments, and his fellows looked away. A six-inch fall under this gravity could kill; there would be many such falls before their comrade reached the bottom. If by chance there were not, his own hundreds of pounds of weight would be scraped against the rocks hard enough and fast enough to accomplish the same end. The survivors dug their feet in a little farther, and gave up all thought of eating before they reached the top. Time after time the sun crossed ahead of them, shining down the cleft. Time after time it appeared behind, blazing into the opening from the opposite direction. Each time the rocks about them lighted up under its direct impact they were a little farther up the long hill; each time, they began at last to feel, the wind was just a little less furious as it roared past their long bodies. The cleft was visibly wider, and the slope gentler. Now they could see the cliff opening out forward and to each side; at last the way ahead of them became practically horizontal and they could see the broad regions of the upper plateau ahead. The wind was still strong, but no longer deadly; and as Barlennan led the way to the left it decreased still further. It was not sharply defined here as it was below; it fed into the cleft from all directions, but from that very fact its strength decreased rapidly as they left the cut behind them. At long last they felt safe in stopping, and all immediately opened their packs and enjoyed a meal for the first time in some three hundred days?a long fast even for Mesklinites. With hunger attended to, Barlennan began to look over the country ahead. He had stopped his group to one side of the cut, almost at the edge of the plateau, and the ground sloped down away from him around nearly half the compass. It was discouraging ground. The rocks were larger, and would have to be traveled around — climbing any of them was unthinkable. Even keeping to one direction among them would be impossible; no one could see more than a few yards in any direction once the rocks surrounded him, and the sun was utterly useless as a means of guidance. It would be necessary to keep close to the edge (but not too close; Barlennan repressed an inward shudder). The problem of finding the rocket when they reached its neighborhood would have to be solved on the spot; the Flyers would surely be able to help there. The next problem was food. There was enough in the packs for a long time — probably for the eight hundred miles back to the point above the Bree’s old halting place; but there would have to be some means of replenishing the supply, for it would never last the round trip or maintain them at the rocket for any length of time. For a moment Barlennan could not see his way through this problem; then a solution slowly grew on him. He thought it over from every angle and finally decided it was the best that could be managed. Once settled on details, he called Dondragmer. The mate had brought up the rear on the arduous climb, taking without complaint the bits of sand loosened by the others which had been hurled cruelly against him by the wind. He seemed none the worse for the experience, however; he could have matched the great Hars for endurance, if not for strength. He listened now to the captain’s orders without any show of emotion, though they must have disappointed him deeply in at least one way. With his duties clear, he called together the members of his watch who were present, and added to them half the sailors of the captain’s watch. Packs were redistributed; all the food was given to the relatively small group remaining with Barlennan, and all the rope except for a single piece long enough to loop through the harnesses of Dondragmer’s entire company. They had learned from experience — experience they had no intention of repeating. These preliminaries attended to, the mate wasted no time; he turned and led his group toward the slope they had just ascended with such effort, and presently the tail of the roped-together procession vanished into the dip that led to the cleft. Barlennan turned to the others. “We will have to ration food strictly from now on. We will not attempt to travel rapidly; it would do us no good. The Bree should get back to the old stopping place well before us, but they will have some preparations to make before they can help us. You two who have radios, don’t let anything happen to them; they’re the only things that will let us find out when we’re near the ship — unless someone wants to volunteer to look over the edge every so often. Incidentally, that may be necessary anyway; but I’ll do it if it is.”
