Still River

by Hal Clement

  “Another drop!” cut in Molly. “I’m falling behind. Who’d have thought we’d need bath towels in this operation?”

  “Can you wave your arms, or something, to make air current that will move them away?” asked Charley.

  “I’m trying. It works for the little ones, but I can’t see in all directions at once, and Carol’s helmet isn’t clear yet so she can’t either.”

  “But why can’t she see through ammonia?” Charley asked almost plaintively. “It’s transparent!”

  “It’s ripply!” snapped the Shervah.

  Charley once again was visualizing the Human’s battle with Enigma and wondering how many more tests there would be. Why had Molly put herself in the position where she, rather than one of the others, was having to take the physical action against the weird little world’s environment, instead of staying in the boat or the tent and letting the others act as well as think? Maybe the presumptive Faculty policy against letting students get into really dangerous situations was operating, but that couldn’t be the whole story. Carol was down there, too, facing the same risks, apparently.

  And why had Molly come up with the idea of using her armor’s heat pump to get rid of the ammonia, instead of letting Carol pass the test herself? The Kantrick, positive from the beginning that they were repeating a laboratory exercise that had been done thousands of times before, almost as certain that the Human was the Faculty member responsible for rating them, was beginning to have doubts about her as a teacher.

  Molly, at the moment, was not even a student. She was concerned with keeping the two of them alive, which seemed to mean finding the ideal time sharing between fending off more drops of ammonia and keeping the radiation from her armor’s heat pump directed at Carol’s helmet. Once the Shervah could see out, her side-placed, independently movable eyes could do a far better job than Molly’s stereoscopic equipment at watching all directions for more of the amoebalike blobs.

  Carol was waiting, and worrying. The robot was sealed against the ammonia, but had she done the job in time? She had been thrashing around thoughtlessly for a moment or two, and might have flung smaller drops of the stuff in any direction. The machine was safe enough in one sense—it had breakers that would shut down any part affected by short or sneak circuits. A fusion unit melt or blow was a possibility that not even laboratory experience brought to anyone’s mind; the devices were as ubiquitous to all their cultures, both in School and on their home planets, as ballpoint pens had been to the Human’s ancestors. They simply didn’t think of them as dangerous under ordinary conditions—Molly’s fear about the robot’s driving into the cave wall, earlier in her adventure, had been a special case, like a child falling while carrying a pen.

  Having power shut down at a time like this was not a pleasant prospect. Was liquid already spreading around inside? Would the device respond to its keys when she did manage to find a safe time to open the access port? Right now it was alternately stopping and resuming descent as drops moved into the path of its height sensor and out again. Each change in motion was a relief to the little Shervah. Neither motion meant safety from more collisions; stopped, they could be caught by the falling drops, and descending they were overtaking them; but changing motion meant the robot was functional. If only she could see!

  Feeling turned out to be enough. Another descent started, and this time the metal cylinder failed to stay upright. Feeble as the gravity was, Carol could tell which way she was hanging in her safety ropes. So could Molly.

  “Robot power is off,” reported the Human as calmly as she could. “We’re falling. Our terminal velocity seems to be faster than the smaller drops, but not as much faster as we were going down before. Maybe I can keep us clear of them long enough to get Carrie’s helmet dry now.”

  “Is that worth doing?” asked Jenny. “Sorry, I didn’t mean to sound quite that pessimistic. Any idea what you’re falling into? That must be a really gigantic cavern; you’ve been going down for minutes.”

  “That doesn’t mean too much here,” the Human replied. “If we can get the inside of this machine dry and find our way to where you and Charley are mapping, this will have been just another interesting datum. Trouble is, if we land in a lake or river, we may have to swim this thing to shore. I wonder whether the robot-Carol-Molly system averages out less dense than liquid ammonia. I certainly hope so. The last two parts certainly are, but I don’t know about this piece of metal.”

  Jenny was probably the most aware of the grotesque aspect of the situation, in spite of the fact that she could see it only by imagination. Her native world’s gravity was nearly twice that of Earth, and the mental picture of her two friends carrying on a more or less reasonable conversation while falling through darkness toward some point they could not sec and whose distance below they couldn’t guess seemed dreamlike in some ways and irresponsible in others. Like most intelligent beings, she had a sense of humor. She had time to reflect how lucky it was that her normal expression of it was not audible and would not be carried by the translators; lucky, since the present situation wasn’t really funny and a laugh like Molly’s or a buzz like Joe’s would be most inappropriate. Her friends might be dead in the next few seconds.

  She controlled the body-ripple that would have corresponded to a giggle had another Rimmore seen it, and listened tensely. Falling took so long here!

  “Good going, Molly! I can see!” came Carol’s voice after what seemed minutes of silence.

  “What’s around you?” asked Charley.

  “Large drops of juice, against a dark background. What else? We’re still falling. Mol, we’re going to hit that one; can we—good! I don’t know if you moved it or moved us. Too bad we don’t have a Parkemm here; your arms don’t really make good wings, and mine are worse.”

  “The last time you wanted to fly was on Sink, when you were beginning to wonder whether our suits were going to keep us warm after all.”

  “Well, we practically did. The gravity was only a tenth of what it is here, and we could keep ourselves in the air—well, off the surface—nearly all the time by jumping. The main point was to keep out of contact with the ground.”

  “But even in that gravity a Parkemm couldn’t have flown. A trace of helium won’t…”

  “Watch it—there’s another drop! Anyway you’re quibbling.”

  “I can’t keep this up. I’m afraid we’re going to have to put up with being wet—Lord, we certainly are! Look down there, if that’s really down!”

  “It’s the way we seem to be going. It…”

  “What is it?”

  “Just listen, Charley. We’ll report when we have time, and until then infer what you can from what we say to each other. I’d say it was too bumpy to be a lake, but with these big drops merging into it and taking awhile to settle, maybe it’s just because I expect a wave on a lake to go away at a decent speed.”

  “It’s too big to be called a puddle. I hope it doesn’t rate as an ocean,” replied Molly. “Here we go. Any bets on whether we float?”

  “Not with my credit. I don’t think there’d be room for an ocean in a cave, even with this gravity. Will you hold my hand? My brain trusts these ropes, but the rest of me doesn’t, quite.”

  “Right. And hold the robot, too. You need it more than you need me.”

  “That’s another point where my brain and the rest of me don’t agree. We’re not floating, are we?”

  “We’re not at any surface yet. I’d like to have seen our splash from outside; just a slow-motion replay of an ordinary one wouldn’t cover the surface tension effects. There, that seems to be surface, a few meters that way.” Molly pointed with her light.

  “We can see all right now, Charley,” Carol remarked rather savagely.

  “How far?”

  “Hard to tell.” Molly took over. “Tens of meters, I’d say. There’s nothing by which to judge the distance; we’re just hanging here. Come on, Carol, let’s see if we can swim effectively enough to drag this thing
to the surface, if that is the surface.”

  “It must be. The bubbles that came under with us seem to be heading that way, though they aren’t in much of a hurry. If it is, we’re traveling; the bumps we saw from above are gone—we must be away from where the spray is falling.” The women fell silent and concentrated on swimming, which is not easy in armor. Molly was good at it under more normal circumstances, and the Shervah caught on quickly watching her. The metal cylinder was certainly denser than the liquid, but Molly found herself able to drag it upward by herself even before her friend was able to offer effective help. Newton’s third law, the inertial aspect of swimming, enjoyed considerable advantage in Enigma’s gravity even if Archimedes’ Principle didn’t. Even so, it took some minutes for their helmets to break the surface.

  “Nothing to report,” Molly said after sweeping her light around. “I assume there’s a current because we seem to be away from the fall already, but if this is a river we can’t see any bank, we can’t see any sides or top to the cave, and we don’t know which way or how fast we’re going. So much for finding your mapped areas.”

  “Then Jenny and I map southward and try to find your ammoniafall,” replied Charley promptly.

  “Which we probably won’t stay anywhere near.”

  “Can you suggest anything better, Carrie?”

  “No. Sorry, Charley. And maybe this will still be a river you can follow.” Molly looked at her companion in some surprise, but her helmet was pulled below the surface by the robot at that moment and she missed whatever expression was on the Shervah’s face. It took her half a minute to get up again, and some seconds more for the liquid to drain sufficiently from her faceplate to permit clear vision.

  She decided that tact was more important than satisfaction of curiosity. So was survival.

  “Carrie, we don’t float. We can’t stay up forever on muscle power. I hate to suggest it, but I think we drift to wherever we’re going along the bottom of this brook.”

  “Why go anywhere?” asked Charley. “The robot isn’t dragging you; why not wait for us to find you? It will no doubt take quite a while, but your armor will keep you alive.”

  “Of course. I’d gotten so committed to the value of keeping going that I’d forgotten we didn’t have to!” exclaimed Molly. “We’ll just wait! When you find the river, Charley, you can follow it down to the fall and over, and we can’t possibly be very far from its foot. If we let ourselves sink to the bottom, we can probably stay put; and when you and Jenny get down here, you’ll be able to see our lights even if we are underwater—I mean…”

  “Sorry.” The Shervah’s voice was softer and more apologetic than any of them had ever heard it. “We can’t wait here.”

  Chapter Eighteen

  Of Course There’s Inflow

  “I don’t think I can take the temperature,” the Shervah explained. “I waded in that first brook for a while, and my feet were freezing even through the armor. If temperature gets too low, my air starts to condense.”

  “That’s right; nitrosyl chloride has an awfully steep vapor pressure curve. Ail right, we’ll have to find shore somehow, or think of a way to dry out the inside of the robot and get it going again while we’re still swimming—that doesn’t seem awfully practical, somehow. But wait a minute—the temperature is a lot colder for me than for you, and your armor should insulate as well as mine. I’m perfectly comfortable—well, as far as that’s concerned, anyway. I’d give a lot to get out of this suit and wallow in hot water. Are you really getting cold?”

  “Not yet. I’m reporting what happened earlier. My feet nearly froze while I was wading.”

  “Did you measure the actual temperature of the brook?” “No.”

  “Then the temperature of this puddle won’t tell us whether you’re really in trouble, but we’d better get it on general principles.”

  Molly was somewhat mystified by the situation. As she had said, the ambient temperature was much worse for Human than for Shervah, and the small humanoid’s suit protection should be at least as good as Molly’s. Indeed, it must be; a vivid picture from fairly recent memory and more recent conversation preempted her thoughts for a moment. It was of a black, airless sky, dominated by half a dozen blazing O-type suns all within three or four parsecs. Much less impressive, though bright by Solar system standards at some seven hundred astronomical units, hung Fire and Smoke, the binary dwarves that formed the main mass of the School planetary system. None of their individual planets was noticeable at this distance. The foreground was a landscape of grayish, dirty methane ice, like the surface of Pluto. Molly and Carol had been together, just as they were now, with an assigned experiment. They had just reached Sink, the outermost common planet of the School suns, with its ten-Kelvin environment that was needed for their work, and this time it had been Molly who was uneasy. “Come on!” Carol had been saying. “It’s safe enough. There’s no gas to conduct; you can only lose heat to the ground, and there isn’t much contact area even for you. Don’t worry; I’ve been here before!”

  Here on Enigma they did not have vacuum around them; maybe that made the difference in the Shervah’s mind. Molly would have to be the support.

  She attempted to bring her set of wrist instruments in front of her helmet while swimming hard enough to keep from being sunk any further by the robot. She was not very successful and was a couple of meters below the surface by the time she had a reading. Its value surprised her enough to take all her attention, and the two went down even further as she called the others.

  “Joe! Charley! The temperature is up about ten Kelvins from the value I reported in that upper cavern. Either we’ve come down an awfully long way, or something is carrying heat to this liquid. Do you check with that, Carrie?”

  “Yes. I still don’t know whether it’s warm enough so I can stop worrying, though.”

  “I’d think you’d be feeling cold already if your armor’s heaters weren’t handling the situation. I know ammonia doesn’t have the heat capacity of water, but…”

  “But if this were liquid water, I wouldn’t be worried about the cold.”

  “Is your armor refrigerating or heating right now?” “Heating.”

  “Which was it doing when you were freezing your feet?”

  “I don’t remember—didn’t notice. I suppose it was heating, but now that I think of it, maybe it was just trying to hold an average. I don’t know much about its heat distribution system or its internal sensing…”

  “You should have made the armor yourself,” pointed out Charley. Carol, for once, had no answer; the criticism was completely right, and she knew it. The suit was part of her field equipment, and she should have known all there was to be known about it.

  “Tell the rest of us if you feel the slightest bit cold or your air pressure seems to be dropping,” advised Molly. “We’ll look for dry land, but maybe we needn’t be as frantic about it as we thought. Let’s get back to the surface and try to see if we’re getting anywhere.”

  But the surface came back to them. They might have been falling for several seconds—perhaps half a minute—before either of them realized that surface was all around them; they were once more inside a large drop rather than a whole river. They must have gone over another fall. Molly reported the fact, resignedly, to the three so far above.

  “We’re trying to swim out of it, but the stuff is wet and sticks to us. It’s huge, too—the biggest by far of any we’ve seen yet.”

  “Are your heads through the surface so you can see out?” asked Joe.

  “We’re sticking out,” Carol replied, “but there’s too much stuff on our helmets to let us see. Why is it important? There’d be nothing but more drops of river floating down around us.”

  “Different size drops, and different density objects like you and the robot, should fall at different rates—there is air, remember. I was wondering whether you were in front of most of the stream or behind it.”

  “I don’t see how we could be anywh
ere but middle” was Molly’s contribution. “What we need is to get to one side and dry out this piece of hardware. That’s worth the effort of getting out of the drop for, though. Come on, Carrie—we’ll give some momentum to the robot as long as it’s in the liquid, and as it’s about to emerge we’ll try to get out ourselves. With luck, we’ll be clear long enough for me to dry off your helmet again, and you’ll have a chance to tell whether there is any direction that will get us clear of this stuff. I suppose we’re in another cave.”

  “That’s what I was taking for granted,” agreed Joe.

  “All right.” Charley was practically authoritative. “You two try to get dry, and Jenny and I will get back to mapping. Now we look for any river, I’d say, and follow it down. Sooner or later we get to the same lake, or ocean, or something.”

  “One more delay,” Joe said firmly.

  “What?” grated the Rimmore.

  “One more piece of apparatus for your mappers, and never mind remarks about whether I should have thought of it earlier. Come back here while we install radar units in your machines. Right now you have to explore any cavern you find visually and might still miss some connecting passages. This way you’ll get every open space you enter, logged in detail the moment you’re into it, and your computers will maintain a complete three-dimensional image set that you can display for your own convenience to help you see where you’ve been, how to get back, or where other things are—if you get a broad enough total picture. Head back here; I’ll have the units ready for you when you arrive.”

  Not even Charley argued.

  Twenty hours later, Molly woke. There had been no particular stimulus; there was still darkness except for her lights and Carol’s, and at the moment not even translator voices. They were far enough from the river, for the moment, so that it was nearly inaudible, not that it made much noise anyway. The hours they had spent trying to win free of the falling drops when they were falling and to work their way out of eddies and other currents when they were flowing had been the main reason she had had to sleep. They had finally struggled to the bank at a point where the stream was practically horizontal, and carried themselves and the robot far enough from the weirdly writhing current to feel safe from it; there, even Carol had collapsed. The Shervah was still lying motionless; for the first time in Molly’s recollection, her eyes were actually closed. For a moment the Human heart almost stopped as she missed the robot; then she saw it parked on the rock a couple of meters away. Was it dry yet and the energy converter that was their life usable?