Still River

by Hal Clement

  “I hope your circuitry is still protected. With those floating drops, you might wind up in worse trouble than we did,” Carol pointed out.

  “True. My claw light is working—I’ll fly away from the neighborhood right away—if I can. My front arm doesn’t work, and turning my body is awkward with a leg out of action, too, and I won’t be able to nip keys as well with the rear hand.”

  “Why not?” Molly couldn’t help asking. “Your front and rear look the same to me—I could never see why you cared which way you were going. Joe doesn’t seem to.”

  “Your right and left look the same to me, but you seem to prefer to use your right,” replied Charley. “Ouch! If we must talk, let’s stick to essentials. I’ll have to be careful moving; if that broken arm or leg shell cuts inner sac, it could be bad. There; I’m turned around. I’ve bent a piece of the hull sheeting to hold the light, since I can’t do that and nip keys with the same digits. I’m traveling. Down, judging by large-drop motion. I trust that is the end of this river; traveling without them may be slow, but I feel better that way from now on.”

  “You’re not going to wait for us, then?” Carol asked innocently.

  “I don’t think so. We don’t know this is your river, after all, and I wouldn’t be much help to you now if we did meet. If it is, maybe you’ll catch up to me; I won’t be going very fast. Jenny, I wouldn’t mind hearing now what you think I ran into that looked so much like water.”

  “As I said, two guesses and a combination. I’d vote for hydrogen peroxide, but it might have been hydrazine or a mixture of the two. The first is most likely to have been really concentrated in that reflux system; as I recall, hydrazine gets to a constant-boiling mixture with water while still pretty dilute. Also, if there had been hydrazine in the river, it would have reacted with the peroxide pretty completely as the lat-ter’s concentration got high.”

  “Joe!”

  “Yes, Molly.” The Nethneen didn’t need to have her thought specified. “That’s what could have gotten them, perhaps. Of course…”

  “We haven’t thought of everything!” All three women chanted this practically in unison, as it came to the Human’s ears. She assumed Carol and Jenny must actually have been slightly ahead of her, allowing for translator delay.

  “We’ve thought of enough.” It was Carol who continued. “There is a reasonable chance, approaching certainty, of higher-boiling things than water getting concentrated toward the bottom of this big condenser, and there’s a demonstrated certainty of explosives being around whether that’s how they originate or not. I say we still follow the river since it remains the best guide downward; it must have done a reasonable amount of erosion, after all, no matter how young the planet is. We treat it very respectfully, though. If we find it shrinking, we assume that little if any of it is water, and get even more careful. The main thing is we keep going down. So does Charley. As long as we can travel, and as long as we can tell which way is down, we travel down. Joe does not come to meet us unless something else happens and we get stopped; and if he does have to do that, Jenny, I strongly advise that you leave your lab, much as I hate to suggest it, and take his route to the big cave and be there to back him up.”

  “I agree. I admit I hope that does not become necessary.”

  “Don’t we all. But, Joe, you’d better send one of your little machines—maybe several for safety—back to your entrance and have them wait there so they can feed the model to Jenny’s mapper if she does have to come. You can treat them that independently, can’t you?”

  “Yes.” Molly wondered whether Joe was as relieved at being able to give that answer as she was at hearing it. “I will send back six. As far as I know, there was no danger to them along that path, but…”

  He stopped. This time no one made the obvious completion. Carol simply approved.

  “All right. Let’s move. I want a shampoo as much as Molly wanted her bath, but someone’s got to stay in shape to complete this tour.”

  Four hours.

  “I’m out of touch with them, of course, but the mappers should be back at the surface by now, Jenny.”

  “They are. My own computer has received and stored the model they were carrying. I am returning to the tent. I would return your machines to you if I could control them.”

  “Beam out five zeros, five ones, then five ones and five zeros on Band 2471. I still foresee a few things.”

  Twelve hours.

  “Molly, I think I do see the other side of this river.”

  “Are we flowing or falling right now?”

  “Flowing, more or less. Just a minute while I swing us over that way. Yes, there is an opposite bank; the whole thing is less than a kilometer wide.”

  “How big is the cave we’re in now?”

  “No idea. I can’t see roof or walls, no matter what I do with my lights.”

  “Anything ahead?”

  “Just more river, right now.”

  Fifteen hours.

  “There’s not much in this machine close enough to its original shape to measure the fall distance with, but gravity is less than ten. The real problem is finding a place where wind isn’t blowing, so I can let something fall, now that this robot doesn’t have a hull any more.”

  “We’ve been having some wind troubles, too, Charley,” replied Carol. “We never did have a hull, but now an occasional big drop is being lifted off this river and carried back upstream, and I don’t always see it coming as soon as I should. Since there isn’t much left of the river now, I’m really afraid of hitting the drops. You at least had some protection and a little distance when yours went off.”

  “Still flow, or some straight fall?”

  “Two straight-down sessions since we last checked in, but nothing like your terminal region. The very small drops got blown back up, but the big stuff kept falling.”

  Twenty-two hours.

  “Joe.” Charley’s voice was little more than a whisper, but it went out on the general channel. Joe acknowledged. “I think the passage walls around me are different. I never saw the mud you and the others were talking about, but 1 have seen mud. Maybe I’m getting there. Keep your radar hot.”

  “We’re still rock, but the river is practically gone,” Carol came in. “I think I see it disappearing over another fall ahead. I’d almost bet it won’t reach the bottom. I wonder if we’ve joined your path.”

  “There’ll be no easy way to tell,” answered the Kantrick. “I haven’t had many very good looks at the route I’ve been following since then; I’ve simply done my best to go upwind. Even if I’d seen it all, I couldn’t remember the details well enough to give you a helpful description.”

  “I know. Don’t worry. We’d never be really sure anyway. The real worry is the explosive river; once we’re away from that we’ll just use the wind, too.”

  “Why did you follow the river if you feel it’s so dangerous?” asked Jenny.

  “Speed. Almost certainly the quickest way downhill. I want to get Molly to help as fast as possible. I’ll be less scared once we’re past it, but no less worried. There—I was right. We’re into another kame from somewhere near the top, and the stream is falling. Slowly. Very slowly. There aren’t any really small drops any more; the waterfall, or peroxidefall, or whatever it is just comes gradually apart and big shimmery blobs of liquid spread out through the cave. Over toward the side they fall a little faster—some of them faster than I’ve seen anything but us go downward for a long time. Maybe eddies—downdrafts. I have to keep alert, but they’re not too hard to dodge. I hope the bottom isn’t too far down, though.”

  “Joe, I can’t see very well. Another eye seems to be quitting, and my head hurts. I can’t see the mud walls any more, and I don’t want to run into them—I remember what happened to you, and I could never dig what’s left of this machine out if I got buried—my light doesn’t show anything—Joe, what can I do?”

  “Don’t do anything, Charley. You’re on my model, a hundred and eigh
ty-four kilometers from my mapper. I’ll be with you in fourteen minutes. Just stop where you are.”

  “How about Molly and Carol? They’re still somewhere in that rock sponge. How can we find them?”

  “They’re doing a pretty good job of finding themselves. Relax.”

  “It hurts.”

  “Do you have any pain-killers in your armor kit?” “Sure.”

  “Then get something out, and tell me how to use it. I’ll be there. You needn’t worry about the others.”

  Twenty minutes later Charley was tranquilized, and Joe reported the fact to the rest.

  “Good. I ’m on the way,” replied Jenny. “One of us can take him back to the boat as soon as I get there—I’ve left it on the surface just outside your antarctic entrance, to save time. I’d say you should start back with him right now, but we don’t know when the others will come through, and someone should be waiting to spot them.”

  “You may as well start back, Joe.” Carol’s voice came quietly. “We won’t be out very quickly.”

  “Why not?”

  “I didn’t want to report until Charley was taken care of, since he seemed so worried about us, but there’s a problem here. We’ve been all over the lower part of this cavern, and I mean all over it. It’s covered with mud, some of it fairly wet—drops must have been reaching the bottom, and sticking, and soaking in fairly recently, though I haven’t seen any do it since we got here. The wind is coming through at pretty high speed, but through hundreds of small vents all over the floor. None of them is big enough for our robot to get through—few of them are big enough for me, even if I were to leave Molly. We could go back—I guess we’ll have to go back—and look for another downward track, but we’re not going to be there very quickly.”

  “Wait. Don’t start back yet; we’ll try to think of something else.”

  “I wasn’t going to. I’m awfully tired.”

  “All right, rest. We have some work here and will be back with you soon.”

  But Carol did not rest. She drove the robot slowly and carefully twice around the perimeter of the cavern, a few meters above the surface of the mud. Not finding what she wanted, she repeated the maneuver fifteen meters higher. This time she located four openings that might conceivably lead to additional tunnels. Explaining to Molly what she was doing, she parked the robot at the mouth of each in turn and explored it briefly by herself. She was not exactly on foot, though her status was not yet quite free fall.

  Two of the passages seemed to go on indefinitely; she followed each for a hundred meters or so before returning. One of the others went horizontally for some fifteen meters and reached a dead end, the barrier closing it formed apparently of hardened mud. The last of the four slanted sharply downward and also came to an early end, but for some reason was entirely free of sediment.

  Carol sternly suppressed the urge to stop everything and try to figure out how this could have happened; she did not even look for small drains or wind vents. After some thought she brought the robot to the mouth of the last passage, helped Molly untie herself, and guided her inside. For the moment she left the machine at its mouth.

  “Stay here, and sleep if you can,” she said briefly. “I have something to try out. I’ll be back soon. Call if you’re worried; I won’t be far.”

  “All right.” Molly did not like to ask for details; her work and friendship with Joe had instilled a good deal of the Nethneen courtesy code into her. In any case, she was quite willing to sleep. Nothing could happen while they weren’t traveling, of course.

  The Shervah half floated, half walked out toward the center of the cavern. The mud floor, pierced with the wind vents that repeatedly tried to pick her up when fatigue made her careless, was nearly three kilometers across. Again she was tempted to stop to figure out the feedback mechanism that must have existed to cause the vents to form so uniformly. Something to do with drying rates? The way in which the liquid returned—no, Carol. Stick to business.

  The nearly nonexistent gravity both helped and threatened to spoil her plan. She had a digging tool of sorts: her sampling hammer, an ordinary geological pick. She approached one of the vents, as nearly at the cavern center as she could judge, and began swinging.

  Her cut was a nearly circular groove over a meter across, wide enough for her small hands to work to some depth. She was hoping that the surface of the mud would be harder than that lower down, and was relieved to find that this was the case. When she thought the groove was deep enough, she worked both hands and the hammer down one side and pried.

  A small part of the edge cracked out, giving her a fragment of hardened mud massing perhaps five or six kilograms. This was not what she wanted, and she tried again, digging deeper before she pried. This time the entire circle lifted, though it broke in two before she had it quite out where she wanted it. She accepted that. There was one more test.

  She carried one of the pieces over to the nearby vent and used it as a cap, circulation overspeeding and breathing stopped as she waited to see whether the wind would lift it against the feeble gravity.

  It stayed. She gave her grotesque equivalent of a smile and began digging again.

  Three and a half hours later, nearly exhausted, she had twenty-five of the mud caps or reasonably large fragments of mud caps each lying beside a vent.

  She swept her light around to make sure she knew the direction to the robot and Molly, and began placing the caps, one after another, as quickly as she could, over wind vents. In ten minutes or less, there was an area at the center of the cave free of updraft, and a quick glance upward warned her that gravity was doing what she had hoped. The drops—School grant they were peroxide, but she hadn’t dared make the obvious test—were settling in the center. She got out of their way quickly, but stopped near the edge of the plugged area to watch the results of her work in detail.

  Her tiny fists clenched as the first of the blobs of liquid touched the warm mud. It stuck, and began to soak in, and slowly she relaxed. More drops were coming, and slowly she retreated toward the robot and her blinded friend.

  Long before she got there, the supply of liquid was exceeding the capillary capacity of the mud, but hydrogen bonding was doing its work. The drops that touched the surface, or touched other drops on the surface, stuck, and a growing, pulsing dome of liquid was swelling where the wind had been stopped.

  Satisfied, Carol made her way back to the side cave in a few careful leaps.

  “All right, Molly? Get any sleep?”

  “Some. What have you been up to?”

  “You’ll see in a moment.”

  “See?”

  “Quite possibly. Joe, you still there?” “Yes. Jenny has not reached the hollow yet.” “All right. Your computer is set to detect any change in the surface, didn’t you say?” “Yes.”

  “Your mappers are covering as much of the polar mud cap as possible?” “Yes.”

  “All right. I’m going to give a quick countdown. At zero, start timing and start watching your model for changes. There may be more than one, and at more than one time, so if you see something don’t stop watching. Are you ready?”

  “Yes.”

  “All right, give me a few seconds to get our machine as far inside this hole as possible. That isn’t very far, but we may need the shelter. There. Where’s my light? I can sic the liquid—yes, clearly enough. Here comes the count. Four. Three. Two. One. Zero.” Carol’s testing laser unloaded.

  Even Molly saw the flash through her closed lids and from deep in the tunnel. The ground shock took over a second to reach them and was not very energetic; the mud, as Carol had hoped, transmitted the wave very poorly. The sound, arriving slightly later, was much worse, but their armor held.

  “I took a seismology course once,” the Shervah remarked complacently. “How about it, Joe?” There was a pause.

  “Most of the mud cap is moving. The area is spreading out…”

  “Gravdh! Did you spot where it started?”

  “
Oh, yes. About forty-five kilometers northwest of where Charley emerged. You couldn’t have been on the same river, I guess. And now there’s more. Four sites near the starting point are changing further—there is material erupting from several of the tunnel mouths.”

  “I hadn’t counted on that. I suppose there was enough mud knocked loose all the way along the tunnels to supply the material, but I didn’t expect it to travel far upwind. It couldn’t have. Surely it’s already blowing back toward the tunnels?” Again there was a pause.

  “Yes, it seems to be.”

  “All right. Actually, that’s very lucky. I was expecting the seismic jolt would zero the area where you could resume your mapping with a really good chance of meeting us, but I didn’t think there was going to be quite such a perfect guide to where we are. It’s just as well. I’m afraid our robot is out of action from the blast wave; you’ll have to come and get us. Just follow any of the four passages that erupted, and don’t worry about getting buried. There can’t be anything left in them that your mapper could possibly knock loose. We’ll be waiting for you out in the open, once we’ve gotten around the remains of this machine. It’s kind of jammed into our shelter, but your radar should spot it all right. Be sure you map the route, so Jenny can follow you if she has to. She shouldn’t, of course, but ...”

  Nobody said it.

  Chapter Twenty-Five

  Datum Five: Molly and Others

  Molly walked comfortably into the chatter room. Buzz was straddling her neck and bouncing violently, but she didn’t mind; real weight, even the three-quarters gravity of Topaz, was heavenly just now. The light was dim but adequate; Fire had set some hours before, but its distant companion provided much more illumination than Earth’s full moon. Carol was a good hostess; the space had been tented, and the air had enough oxygen for her Human and Rimmore guests. The Shervah herself wore a transparent breathing suit that permitted her freshly washed fur to show to full advantage. The Humans were similarly protected from the cold.