Still River

by Hal Clement

  The Rimmore grated strong approval, and no one else objected. Four hours later Jenny was happily burdened with bottom samples from every lake within twenty kilometers—some of them had been over fifty meters deep—and Joe’s tendrils were empty.

  The raspy voice was more enthusiastic than Molly had ever heard its owner before. “Look at this stuff! Clay minerals—a real likelihood of protolife compounds on their surfaces! I was hoping for a chance to do some structures. A lot of this sparkly stuff—it must really catch your eyes, Molly—you know, I have some ideas about that. It could be prelife stuff, too; remember the Dendender, and the Pahrveng, and—oh, at least a dozen others you sometimes meet at the School. They all look metallic, but its really carbon compounds with free electron channels in their structures that make them shiny and gives them real electric conductivity in their nervous systems. Some of them can handle this temperature range. I’ll have to get at that stuff I thought was free metal. And look at this slime! Beautiful! Docs somebody want to look it over with a simple microscope—I’ll bet it won’t take chemistry to tell the story here!”

  “But who walked off with Joe’s robot?” asked Charley. “You mean what happened to it?” “Of course.”

  “I don’t know. If it’s in any of those lakes, it’s sunk into the mud. It was dense enough for that, wasn’t it, Joe?”

  “Yes, in principle. I don’t know how long it would take in this gravity. I’ll have to rig up some sort of metal detector and look for it under the mud, I suppose.”

  “I’ve thought of a way to narrow the search,” Molly put in rather diffidently.

  “How?” Again several voices sounded together.

  “It would mean interrupting part of your mapping project. You could start another robot at the same place the first one was and watch to see where it went.”

  “We don’t know that the air currents haven’t changed. It’s been hours now, and that storm that blew me away when we first landed certainly wasn’t permanent.”

  “I realize that. I still think it’s worth trying. Even if the second robot doesn’t go to the same place, it will be investigating currents in the area where the first vanished; and that would seem to me to be worth doing in any case.”

  “It would mean staying here, away from the tent and the main work.”

  “Not for all of us. We could take turns—or just one of us budget a few hours, since that’s all it took the first one to vanish. You could stay at the tent and watch your map grow—maybe other information would appear there that would help—and Jenny of course must get back to her chemistry; but Charley or I could stay here for a while, and Carol might enjoy it—except she might forget to watch the robot if the landscape got too interesting.”

  “Wouldn’t that interfere with your work?” asked Joe.

  “I don’t think so. Much of my thinking is going to depend on what Jenny’s analyses tell me. I’m sort of hung up until I can either find ice or get some evidence that it’s just not here. Charley has been working along with me, unless that new idea that he won’t describe is a branch-off. I’ll be glad to ride herd on a robot for a few hours. Which one do you think would be best to pull out of your pattern?”

  A little more than three hours later, the boat settled back to the ground at the starting site of the lost machine. Joe, after some vacillation, had decided which of the robots to pull from his pattern, and the group had collected it and its slaves. This had taken most of the time, as the slaves were by now scattered over a fairly large area.

  The device was placed precisely where its predecessor had been, Carol’s memory serving as the final check, and Joe made sure that the original programming was still set up. None of them could be sure whether the local wind was just as it had been before; Carol had not been outside to feel it. Since no one had been present when the first one had started to move, only the original instrument log could have been used as a check; and, as Charley remarked—no one else bothered to—if that had been to a large enough scale, the present reenactment would not have been necessary anyway.

  Possibly.

  “All right, it’s ready,” said Molly as Joe closed the access plate of the metal cylinder and stepped away. “Charley, you take the others back to the tent and then come back to keep an eye on me. It shouldn’t take you very long, maybe three quarters of an hour. It was much longer than that before we lost track of the other one, so there’s no need to worry about me. My batteries are charged, emergency chemical cells loaded—I’d be all right for days if I had to. Don’t worry, just get the others back to their work.”

  Charley, rather to her surprise, made no objection, and she watched the two-hundred-meter torpedo lift from the rock and vanish into the bright dust clouds.

  She did not keep her eyes fixed on the robot, though she watched with some interest as the slaves detached themselves from its top and drifted upward. She knew the master would not start its motion until they had all reached their planned altitudes, so she spent some minutes looking over the ground in the hope of finding some evidence of the ice he so badly needed for her theory—no, she corrected herself, her hypothesis; at the present rate she would have to be very lucky for it to graduate to theory status.

  Still, there had to be ice somewhere; the surface material Jenny had analyzed up to this point was far above Enigma’s average density. More and more it seemed likely that the stuff was inside; that Enigma, like a middle-aged comet, had lost much of its outer ice and concentrated the silicate to a real crust. If all the surface had been sand, or salt, or dust, this would be easy to believe; but rock? She found an exposed patch of the dark, hard stuff and examined it as closely as she could by eye. She had ordinary tools, and chipped off a few more pieces with laser and hammer; but there was nothing about them, or the flare as they vaporized under the laser beam, to suggest that these were any different from the earlier ones. Sodium, of course, as any human eye could tell, but that ubiquitous element was not very informative.

  She glanced up at the robot. It had started to move, so she suspended her planetological research for the moment. The metal cylinder drifted along, into the wind as planned, its base a few centimeters from the ground, much more slowly than a comfortable walk. She amused herself by marking its path with her own footprints whenever it passed over anything soft enough, and by the time Charley came back with the boat she had decided that the wind was fairly steady. While she could locate the foggily visible sun at times—the combination of filters and eyeshades that even she had to use to protect skin and eyesight from the tiny, blazing disc had startled her friends considerably—she was at a latitude where it was above the horizon all day and was in no position to judge absolute direction.

  The situation was getting rather boring by the time the boat settled down near her again. She was, for once, as glad to see Charley as he was presumably relieved to see her.

  “Let’s establish some direction around here!” was her greeting. “Will you get the inertial system to line up the boat’s long axis with the local meridian? I feel lost not knowing which way is north.”

  “No problem,” replied the Kantrick. “Are you sure you’ll feel any less lost when you do, though? You don’t know what there may be in any direction, whether the latter is named or not.”

  “Maybe not, but I’d feel happier knowing whether I’m walking azimuth twenty or three hundred twenty. I admit it would also be nicer to know where I’ve been—well, I do; I was at Joe’s Station Fifteen—and where I’m going, but knowing which way is some help. Don’t be so individual, Charley. Haven’t you ever tackled an idle problem when you were bored?”

  “I prefer to find an important one. However ...” The craft lifted, swung slowly, and settled once more. “To within a grad or so, the axis is pointing along a great circle through the planet’s poles of rotation, with the bow toward the nearer one.”

  “Good. Thanks. By my convention, that’s north—it’s northern hemisphere summer. The robot is drifting toward azimuth sixty-fi
ve or so, not that my line of footprints is very precise. What can we do now to keep busy? It didn’t occur to me that this job would be simple snail-watching. If this thing is going to disappear, I wish it would get about it.”

  Charley was of course able to infer something about snails from the context, but giving him more details killed a little time. Molly was rather amused at part of his reaction; he was not quite sure whether to add the words in question to his translator’s vocabulary, vast as the memory capacity of the equipment was. He wasn’t convinced that they were worth the space. The Human had calculated long before that she could add words as fast as she was likely to be able to talk for the rest of her life without reaching the storage limit of the fifty or so cubic centimeters of doped synthetic diamond at her throat. This was one reason she had deliberately made the attempt to program the device to handle tone inflections—or whatever Nethneen, Rimmore, and the other team members used instead of tones—as well as formal symbols.

  She spent some time at this now, chatting idly with Charley, trying to read likely emotions into his answers and assigning different tonal values to them. She had no real confidence in the result, but it was fun.

  One kilometer. Two kilometers. Time out for food, still watching from the Con room. It was much more pleasant to eat in the boat than to depend on the recycled material provided by the armor. Charley felt the same, and while there seemed no possibility of cither’s ever tasting the other’s foods, a discussion of taste and of food preparation as an art form entertained both of them for some time. Both, as it happened, knew something of each other’s culinary customs; they had attended social gatherings at the School often enough. These were normally interspecies, and it was customary for guests to bring their own refreshments. Even beings with common temperature range and using the same body-fluid base, such as the usual ammonia, were seldom similar enough chemically to share each other’s foods. Demonstrations were not unusual—a Human consuming corn on the cob or lobster, or a Kantrick everting his stomach starfish style around an artistically prepared and decorated delicacy of nearly his own size. The typical student had learned to be tolerant and even casual about sights that would have revolted a less sophisticated member of his or her race. Charley and Molly were able to be critical on a reasonably artistic level.

  The robot, disappointingly, had ceased to follow a straight line. After some eight kilometers of annoyingly slow travel, it was approaching one of the conical “volcanoes”—not directly, but working its way closer in rather erratic style.

  “You know, if there are eddies around the lee side of that thing, the machine is just going to spend the rest of the term going around in circles,” Molly remarked as the hill loomed closer.

  “Could that be—no, we’d have found it; or rather, we’d never have had any reason to wonder where it was.”

  “We’d have wondered why it wasn’t traveling, after a while,” pointed out Molly.

  “I admit it was an afterthought, but I did cover the eddy problem in the program” came Joe’s voice. “If the present chase leads you to one, watch what happens after three trips around the circle.”

  “I apologize, Joe,” replied Molly.

  “No need; I have already made sillier mistakes—or, at least, mistakes equally attributable to inexperience, I suppose.”

  “How is your map growing?”

  “Convincingly. I still have no suggestion as to what may have happened in your area, however, so please don’t lose track of the machine. I would hate to have to spare another from the pattern.”

  “We’re watching. I won’t need sleep for a while yet, and Charley for a lot longer. By the way, Joe, how closely has the map pattern made by this robot and its slaves matched the first?”

  “So far they are indistinguishable on the map scale. I am very encouraged that the same thing is likely to happen again.”

  “Do you mean encouraged or hopeful?”

  “I should have used the latter term, of course. Has the robot shown its response to an eddy yet?”

  “Not yet. I think there may be one soon; we’re near a bill. But something occurred to me, Joe. Wouldn’t it be possible to get some sort of idea how constant Enigma’s wind patterns are, or at least whether they change with seasons, by comparing earlier pictures of the planet? Right now, for example, the south pole is having winter and is just about free of clouds; here it’s summer and almost solidly decked over. That’s not what I would expect—maybe Jenny mentioned that to you earlier; we noticed it from Classroom.”

  “She did, but it gave me no ideas. I did secure a set of early pictures, but I…”

  “They let you have them?” asked Charley.

  “Yes. I have not yet made sense out of them, however. Some of the rest of you should try when you have time.”

  “I think we’re getting to an eddy zone,” Molly cut in tactfully.

  She was right, but the watching required some waiting, as well; it took the machine fully ten minutes to get around each swing of the eddy. Molly had to remind herself that the speed of the robot had nothing to do with the speed of the wind; the latter was registered on the map by the pressure sensors in the cylinder’s skin, the former was determined by the preset program. The boat had no equipment for measuring wind directly, and unless there was something like sand or precipitate blowing around visibly there was no way of judging air currents from inside.

  Molly decided, well before the third traverse of the eddy pattern, to go out and judge for herself. Charley made only a halfhearted objection; he was rather impatient for something to happen himself, and would have suggested that he be the one to go out if he had not had so much private reason to follow Molly’s lead in most matters. He settled himself more alertly at his screen while the Human re-checked her armor.

  Outside, she could barely feel the wind, light as she herself was. They had grounded the boat several hundred meters from the robot to avoid complicating the winds in the latter’s neighborhood, and by the time she had walked carefully to a point perhaps fifty meters from the cylinder, it had completed its third trip around the eddy. The response that Joe had built into it was immediate and obvious. Molly reported for the Nethneen’s information.

  “The robot’s lifting straight up—the wind’s so light I can’t tell whether it’s holding station for the moment or still going against the current.”

  “I set it to hold” came Joe’s voice. “Integrating all the velocity contributions during the lift into the map would have been more of a complication than it was worth.”

  “How high should it go?”

  “Nine or ten meters. Then if it follows more than an eighth of a circle around the same eddy course it will rise again, and so on until there is a significant difference.”

  “It’s about ten meters up now. I think it’s drifting more nearly straight toward the hill than it was before.” Molly paused for perhaps a minute. “Yes, it’s definitely closer—it’s over the base of the cone now. Its course is changing, I think—yes—it was making a slanting climb; now it’s heading straight toward the top. I’ll follow it.”

  “Better do it in the boat,” cautioned Charley.

  “No need. I can go a lot faster than its set speed on foot. Fly over the hill if you like and see where it’s going. It looks like one of Carol’s ’volcanoes’.”

  Molly moved as quickly as the gravity permitted to the base of the slope and started to climb after the robot. She promptly encountered the same difficulty that Carol had laced some hours before. The hill was of loose, sandy material at its angle of repose; the stuff slid down under her, refusing to support even her few kilograms of weight. Fine powder rose around her, cutting off her vision completely until it drifted slowly away from the hill in the negligible breeze.

  “It’s a crater, all right,” Charley reported from overhead. It’s not quite like the ones we got involved with before. It looks as though the hill were a heap of sand on a flat table of rock. It seems to be a little deeper inside than
it is high from without, but the sand doesn’t come together the way Carol’s did. There’s a definite hole that goes down into darkness where I can’t see. If there is gas coming out, that will explain what happened to the other robot; it must have followed its program into the hole.”

  “But these aren’t real volcanoes. How could wind be coming out of a hole in the ground?” asked Joe. Molly had a flash of inspiration, remembering the wind Carol had noticed in her trap.

  “My ice!” she called. With no more words, she retreated a score of meters from the hill and then “ran” toward it as rapidly as her negligible weight permitted. As she reached the slope she jumped toward the robot as hard as she could.

  She flew over it, spinning awkwardly, and struck the slope almost flat on her back four or five meters above the drifting cylinder. The sand here was no more able to support her than that at the base had been, and she slipped downward. Her aim had been good, however, and she met the machine within a few seconds. There might have been time for another leap if she had missed, she reflected later; she was never sure whether she would have recovered her common sense in time not to make it.

  “Molly! What are you up to?” cried Charley.

  “I’m getting a look at that hole in the ground, and I’m getting gas samples out of it?” she replied firmly. “Besides, if the robot tries to go out of sight, shouldn’t we stop it?”

  “How?” came the pointed query in at least two voices. The Human thought as quickly as she could.

  “If I block its pressure sensors except on one side, won’t it suppose that way is upwind?”

  “No,” replied Joe. “The actual sensors are inside, fed by microscopic openings in the shell. You couldn’t block them all without wrapping the whole machine in something. You probably can’t even see them. If a few are totally blocked, the controller will assume that that’s what’s happened and omit them accordingly from the wind calculation. How do you suppose Carol and I were able to ride one awhile ago, without upsetting its guidance?”