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was a change in the nature of the ground underfoot. Instead of the usual feldspar-rich granitic rock, heavily pitted with solution cavities, a darker, much smoother material became predominant. Neither of them had ever seen fresh lava, since Nick had brought back no specimens, and it took time for their feet to get used to it.

The rain was getting very close to the surface now. There was no difficulty in dodging drops, since there was more light coming from ahead than Altair gave at high noon; the trouble was that Nancy was not bothering to dodge them. Theoretically she was right enough; they weie still cloudy with oxygen bubbles, and her body heat turned them into perfectly breathable air, but it took a while for John to follow her example. Habits are as hard to break for Tenebrites as for human beings.

Gradually the slope of the dark rock began to increase. They were on a hill, and the light was close ahead, now. Rocks were silhouetted sharply against it, not more than a mile in front. Nancy stopped, not because of the rain but to take a final look around; and it was then that they both noticed something else.

In the first place, the raindrops were not falling straight; they were drifting horizontally as they descended, drifting in the same direction as the two were traveling. That was reasonable when one stopped to think; they had known about convection and advection currents almost as long as they could remember. It was the speed that was remarkable; the drops were heading toward the fire at a good two miles an hour. The air current that impelled them could actually be felt—and that was a major hurricane, for Tenebra. If the thing ahead was a fire, it was a bigger fire than Fagin's pupils had ever lighted or ever seen.

"If Swift lighted that, he must have touched off a whole map section," remarked John.

Nancy turned to him abruptly. "Johnny! Remember what happened last night, when Nick got the Teacher away from the caves? He did light fires over a good part Radiation; Evaporation; Advection 123

of a section! Do you suppose they could still be burning, and have spread like this?"

"I don't know." John stood still and thought for a moment or two. Then he referred to the map, easily legi-ble in the brilliant light. "I don't see how it could be," he said at length. "We're a lot closer to the caves than we were this morning, but not that close. Besides, the clear rain late at night should have put any fire out if there was no one to tend it."

"But if it were big enough, maybe it would stir up the air so there was always enough oxygen for it—feel this wind on our backs. Have you ever known anything like it?"

"No. Maybe you're right. We can go on and see, though; I still think it's more likely to be Swift. Are you still going to try that idea of yours?"

"Of course. It's all the better, with the wind carrying the drops as fast as this."

"I hope you're as right as you are reasonable." The two went on, somewhat more slowly since it was necessary to follow a rather tortuous path to keep their goal in sight among the drops. These were now reaching the surface in great numbers and remaining liquid, except for those parts most closely exposed to the body heat of the two travelers. It took a little longer than might have been expected, therefore, to get within two hundred yards of the rocks ahead, which from the absence of anything but light beyond them appeared to mark the top of the bill. At this point, Nancy decided that stealth was in order; so she brought the scary part of her plan into operation.

Finding an exceptionally large and still cloudy rain drop drifting downward at no great distance, she deliberately placed herself so as to be enveloped by it as it landed. Naturally, the bottom portion of the fifty-foot spheroid was obliterated at once by her body heat; but further descent of the drop finally hid her from view. The great, foggy blot of liquid began to follow the general pat-124 CLOSE TO CRITICAL

tern of activity of the others, moving slowly toward the light; and Nancy did her best to follow. This was not as easy as it might have been, even though the gas around her was perfectly breathable, since with no view of her surroundings it was nearly impossible to judge the rate of drift of the raindrop. The wind was some help, but not enough, and several times John could see her outline as she came too close to the edge of the volume of fog. He stayed where he was, not considering it cowardly to see how the experiment turned out before he tried it himself.

In one sense, the trial was a perfect success; that is, Nancy remained conscious as long as the drop lasted.

In another, however, there was something lacking. This lay in the failure of the drop to last long enough.

Suffering the assault of heat radiation both from Nancy within and the fire ahead, the thing abruptly faded out in a final surge of turbulence, leaving her in full view.

This turned out to be less of a catastrophe than it might have been. For three or four seconds after the vanishing of her concealment Nancy stood perfectly still; then she called out, making no effort to direct her voice away from the light ahead, "Johnny! Here, quick!"

Her companion leaped forward, taking a little but not much less care to dodge raindrops, and came to a halt at her side.

She had stopped perhaps five yards from the edge of a nearly vertical-sided pit, fully two miles across.

Her first few seconds of silence had been spent in telling herself how lucky she was that her shelter had not lasted a few seconds longer; then the blast of radiant heat coming from the floor of the crater, a scant hundred feet below, forced her to admit the matter was hardly one of luck. It could be seen from this vantage point that no raindrops at all approached the area except those which drifted up the slope of the hill from outside. The floor glowed visibly all over, and numerous patches were of almost dazzling brilliance. These last looked suspiciously like liquid, though

Radiation; Evaporation; Advection 125

the liquid possessed a remarkably sharp and well-defined surface.

Raeker, or even Easy, would have recognized a volcano at once; but the phenomenon was completely outside the experience and education of Fagin's pupils. Raeker had noted, in passing, Nick's earlier reference to the conical shape of the high hill he had reported; the geologists had also paid some attention to it, and even placed it on the list of things to be investigated more fully; but that was as far as matters had gone. Nick had said nothing to suggest that the thing was active—or rather, nothing the men had recognized as such evidence; he had mentioned wind. As a matter of fact, it had not been nearly so violent when he had passed, some three terrestrial months before. Only its size and shape had been worthy of note.

"You know," John remarked after some minutes of silence, "this would be a wonderful place for a village.

We wouldn't need to keep fires going."

"How about food?" countered Nancy. "The plants growing on this dark rock are different from the ones we're used to; maybe the cattle wouldn't eat them."

"That would be easy enough to find out—"

"Anyway, that's not the assignment just now. This light obviously isn't what we're looking for, though I admit it's interesting. We'd better get on with the job."

"It's raining," John pointed out, "and there was no suggestion that we should search through the night as well as by day. This would seem a perfect place to sleep, at least."

"That's true enough—" Nancy's agreement was interrupted suddenly. Some three hundred yards to their left, a segment of the pit's edge about fifty yards long and ten or fifteen deep cracked loose with a deafening roar and plunged downward. In that gravity even Tenebra's atmosphere was an ineffective brake, and a good ten or fifteen thousand tons of well-cemented volcanic detritus made its way effortlessly through the red-hot crust of nearly

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solid lava at the foot of the ledge. The results left no doubt about the liquid state of the hotter material—or would have left none had the two explorers still been watching. They weren't; they were on their way downhill in the direction from which they had come before the mass of rock was completely detached.

Even as he ran, John had time to feel lucky that the incident had waited to happen until Nancy had agreed with him about what a good camping spot the place was. Needless to say, he did not mention this aloud.

Even John was not bothering to dodge raindrops at the moment, much less talk on irrelevant subjects.

They covered nearly a mile down the slope before stopping. The light was still quite ample to permit reading the maps, and it took only a few minutes to convince them both that this was indeed the tall, conical hill which Nick had reported. With this settled, however, neither could quite decide what to do about it.

The natural urge was to return to the camp to report the phenomenon to Fagin; against this, however, lay the fact that they had another assignment to complete, which involved life and death.

"This can wait a day," John pointed out. "We can perfectly well camp right here, search our areas tomorrow, and then go back as was planned. We can't drop everything for one new discovery."

"I suppose not," agreed Nancy with some slight reluctance, "but we certainly can't camp here. There isn't enough fuel for a dozen hours on this black stone, to say nothing of the rest of the night; and the raindrops are starting to get clear."

"That I had noticed," replied John. "We'd better get going, then. Just a minute; there's enough here to make a torch. Let's get one started; we may be a little pressed for time later."

Nancy agreed with this observation, and ten minutes later they were on their way once more with John carry-Radiation; Evaporation; Advection 127

ing a glowing torch and Nancy the material for two more, all that the vegetation within convenient reach afforded. They headed toward a region which their maps showed as having slightly higher hills than usual, so as to avoid finding themselves in a lake bed before morning. Both were becoming a trifle uneasy, in spite of Nick's earlier success at all-night travel; but they were distracted once more before getting really worried.

Again a light showed ahead of them. It was harder to perceive, since the brilliance from behind was still great, but there was no doubt that a fire of some sort was on one of the hilltops ahead of them.

"Are you going to sneak up on this one the way you did on the other?" queried John.

Nancy glanced at the now dangerously clear raindrops and did not condescend to answer. Her companion had expected none, and after a moment asked a more sensible question.

"What about this torch? If we can see that fire, anyone near it can see us. Do you want to put it out?"

Nancy glanced upward—or rather, shifted her attention in that direction by a subtle alteration in the positions of her visual spines, which acted rather like a radio interferometer system, except that they were sensitive to much shorter wavelengths. "We'd better," she said. "There's plenty of light to dodge the drops."

John shrugged mentally and tossed the glowing piece of wood under a settling raindrop. The two slipped up toward the distant light.

It was an ordinary fire this time, they could see as they approached. Unfortunately, there was no one visible near it, and the vegetation was not dense enough to hide anyone of ordinary size unless he were deliberately seeking to use it for the purpose. This suggested possible trouble, and the two explorers circled the hill on which the blaze stood with the most extreme caution, looking for traces of whoever had been there in the past few hours. Not

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having the tracking skill of the cave dwellers, they found no signs of people. After two full circuits and some low-voiced discussion, they were forced to conclude that either whoever made the fire was still on the hill but remarkably well hidden, or else the fire itself had been started by something a trifle unusual.

The latter hypothesis would probably not have occurred to them had it not been for their recent experience with the volcano. There seemed no way, however, to decide between the possibilities by reason alone.

Closer investigation was in order and, with a constant expectation of hearing the sharp voice of Swift echoing about them, they set to it. Very carefully, exam-* ining every bush, they went up the slope.

The climb bore some resemblance to a scientific experiment, in that its completion eliminated both of the hypotheses and left them completely without ideas for a moment. It was only for a moment however; as the two loomed up beside the small fire, which had quite obviously been laid by intelligent hands, a shout sounded from the next hilltop, three hundred yards away.

"John! Nancy! Where did you come from?" The startled investigators recognized simultaneously the voice of Oliver and the fact that they had been a little hasty in eliminating possibilities; obviously they had missed a trail, since neither Oliver nor Dorothy could fly. Neither said anything about it aloud; each decided in private that the different vegetation of the area was responsible.

When Oliver and his companion came back to the fire from the separate hilltops to which they had taken on sighting John's torch, it quickly transpired that they, too, had seen the light of the volcano and had come to investigate it. Their adventures had been very similar to those of John and Nancy, except that neither of them had tried hiding in raindrops. Oliver and Dorothy had been an hour or so ahead of the others, and had found a good supply of fuel, so they were well set for the night.

"I'll bet Jim and Jane will be with us before the night's Radiation; Evaporation; Advection 129

over," remarked Nancy when both parties had completed thek exchange of information. "Their search areas were even closer to this place than yours, Oliver, and unless they went 'way off course coming across country they must have seen the big light, too."

"Maybe they thought it was better to stick to their assigned job," remarked John.

"Isn't investigating bright lights part of the job?" retorted his partner. "As for me, if they're not here in an hour or two I'm going to start worrying about them. This fire-hill couldn't possibly be missed or ignored, and you know it."

No one had a suitable answer for this, but no one was really impressed by the reasoning, since they had all spent some time in discussion before coming to check the mountain. At any rate, the hours passed without the predicted appearance. If Nancy was worrying, she failed to show it; certainly none of the others were.

It was a very quiet night, and there was nothing to worry about. The hours were passing, but that was normal; the light was getting brighter, but there was the peculiar hill to account for that; the rain was decreasing, but the hill might account for that, too. The fire was using up its fuel with unusual speed, but there was plenty of fuel. Doubtless the wind was responsible—none of them had ever experienced such a wind, and an air current one could actually feel would no doubt do many queer things. The four explorers stood by their fire and dozed, while the wind grew fiercer.

IX. DEDUCTION; EDUCATION; EXPERIMENTATION

"DADDY! Dr. Raeker! 'Mina's right; it's Nick!" Easy's voice was close to hysteria. The men glanced at each other, worried frowns on their faces. Rich gestured that Raeker should do the answering, but his expression pleaded eloquently for care. Raeker nodded, and closed his own microphone switch.

"Are you sure it's actually Nick, Easy?" he asked in as matter-of-fact a voice as he could manage. "He's supposed to have stayed at the camp, you know. There are six others actually searching, supposedly in pairs; do you see two of them, there?"

"No," replied Easy in a much calmer voice. Her father sank back in his chair with a thankful expression on his face. "There was only one, and I saw him just for a second. Wait—there he is again." Raeker wished he could see the girl's face, but she was shouting her messages from one of the observing chambers and was well out of pickup range of the vision transmitter. "I can still see only one of them, and he's mostly hidden in the bushes—just his head and shoulders, if you can call them that, sticking up. He's coming closer now. He must see the 'scaphe, though I can't tell where he's looking, or what he's looking with. I'm not sure whether he's the same size, but he certainly is the same shape. I don't see how you'd ever tell them apart."

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Deduction; Education; Experimentation 131

"It isn't easy," replied Raeker. "After a few years, you find there are differences in their scale and spine arrangements something like the differences in human faces. Maybe you can tell me what this one is wearing and carrying; that should be a lot easier to describe."

"All right. He has a sort of haversack slung over what would be his right hip if he had any hips; it's held by a strap running up around the other side of his body, over the arms on the left. The front of the sack has a knife hanging from it, and I think there's another on a sort of complex strap arrangement on the other side, but he's been working toward us at an angle and we haven't had a good look at that side. He's carrying four spears that look just like the ones Nick and his people had, and the more I see of him the more he looks like them."

"Does he have an axe, or anything looking like one?" asked Raeker.

"If he has, it's hanging from his straps at the left rear, where we can't see it."

"Then I'm afraid you're going to have to make good on your claim that you can get on all right with Swift's people. Mine carry only two spears, and the search teams took their axes with them. If that were one of our searchers he'd have an axe in one of his left hands, almost certainly. That means we'll have to change our plans a bit; we were hoping our folks would find you first. That's just luck; I suppose this is some hunter of Swift's. They'd hardly have had time to get an organized search going, even if he decided to run one on his own."

"Isn't it going to be a long time before any of your search teams get back to the camp?" asked Easy after some seconds of thought.

"I'm afraid so; over a week of our time. Swift's answer should be back to Nick before then, though."

"I wish the time didn't stretch out so on this darned four-days-for-one world. Didn't I hear you say you'd CLOSE TO CRITICAL

learned a little of Swift's language during the time he had the robot at his caves?"

"We did. Not very much, though; it's extremely hard for a human being to pronounce. We recorded a lot of it; we can give you the sounds, and as much as we could get of the meaning, if you think it will be any help. It'll help time to pass, anyway."

Easy's face appeared in the screen, wearing an impish expression.

"I'm sure it will be very helpful. Won't it, Daddy?"

Even Rich was grinning. "It will, Daughter. She'll learn any language she can pronounce nearly as fast as you can give it to her, Doctor." i i "Really? I've never heard her talk anything but English to her young friend there."

"What human being can pronounce Drommian? She understands it as well as I do, though."

"Well, I wouldn't bet very much that she could pronounce Tenebran, either. It's got some sort of pitch-inflected grammar, and a lot of the pitch is above human vocal range. Of course, she's young and female, but I'll bet she confines herself to understanding."

"You may be right. Hadn't we better get back to the matter in hand? What's that native doing now, Daughter?"

"He's walking around, thirty or forty yards from the 'scaphe, looking it over, I suppose. If he's seen us through the ports he hasn't shown any sign of it. He's still alone —I guess you're right, Dr. Raeker; I remember you sent your people out in pairs, and if anything had happened to one of a pair the other would surely report back to camp before going on with the search."

"I'm not sure you're right there, but I am certain it's one of Swift's people," replied Raeker. "Tell us when and if he does anything new."

"He is now. He's going out of sight the way he came. He definitely doesn't carry an axe; we've seen all sides of him now. He's getting hard to see; there's less of him Deduction; Education; Experimentation 133

visible above the bushes, and he's getting out of range of our lights. Now he's gone."

Raeker glanced at a clock, and did some rapid mental arithmetic. "It's about four hours to rainfall. Easy, did you say whether he was carrying a lighted torch, or fire in any form?"

"He definitely wasn't. He could have had matches, or flint and steel, or some such fire-making apparatus in his pouch, of course."

"Swift's people don't know about them. Nick's group makes fire by friction, with a bow-drill, but I'm sure the others haven't learned the trick yet. They certainly hadn't yesterday—that is, three or four ship's days ago. Anyway, the point I'm trying to get at is that if the one you saw had no fire, he was presumably within about four hours march, or not too much more, of Swift's main group; and , they'd almost have to be either at their caves or near the line between those caves and the point where Nick and the robot took to the river last night. He may be even closer, of course; you'd better keep your eyes open, and let us know immediately if the main body shows up. That . would give us a still closer estimate."

"I understand. We'll look out for them," replied Easy. "While we're watching, how about getting out those Ian- ; guage tapes you have? The sooner we start listening to them, the more good they'll probably do us."

Raeker agreed to this, and the next few hours passed without any particular incident. Nightfall, and then ram-fall, arrived without any further sign of natives; and when the drops grew clear the children stopped expecting them. They ate, and slept, and spent most of their waking hours trying to absorb what little Raeker had gleaned of Swift's language. Easy did very well at this, though she was not Ij quite the marvel her father had claimed.

A complication which no one had foreseen, though they certainly should have, manifested itself later in the evening. The bathyscaphe began to move again, as the river 134

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formed around it and increased in depth. The children were quite unable even to guess at the rate of motion, though they could see plants and other bits of landscape moving by hi the glare of their lights; the speed was far too irregular. Even if they could have reported anything more precise than "sometimes a fast walk, sometimes a creep, and sometimes not at all," they were not even sure when the motion had started. They had had their attention drawn to it by an unusually hard bump, and when they had looked outside the few features visible were already unfamiliar. They might have been drifting a minute or half an hour.

Raeker took some comfort from the event, though Easy had been slightly disposed to tears at first.

"This gives us one more chance of getting our own people to you ahead of Swift's," he pointed out. "The cave men will have the job of hunting for you all over again, while we are getting you more closely located all the tune."

"How is that?" asked Easy hi a rather unsteady voice. "You didn't know where we were before we started moving, we don't know which way we're moving, how fast, or when we started. I'd say we know less than we did last night, except you can't know less than nothing."

"We don't know," granted Raeker, "but we can make a pretty intelligent guess. We judged that you were within a few hours' walk—say twenty-five or thirty miles—of the line between Swift's caves and our people's camp.

We are about as sure as we can be without having actually mapped the entire area that this region is in the watershed of the ocean Nick's people found. Therefore, you are being carried toward that sea, and I'll be greatly surprised if you don't wind up floating on it, if not tonight at least in the next night or two. That means that Nick will only have to search along the coast on land if you don't reach the ocean tonight, or look offshore for lights if you do. I shouldn't think you'd go far out to sea; the river will lose Deduction; Education; Experimentation 135

its push very quickly after getting there, and there's no wind to speak of on Tenebra."

Easy had brightened visibly as he spoke. Amina-dorneldo, also visible on the screen, had not made any change of expression detectable to the human watchers, but the girl had cast a glance or two his way and seemed to be satisfied with the effect of Raeker's words on him. Then a thought seemed to strike her, and she asked a rather pointed question.

"If we do get carried out on the sea, what do Nick's people or anyone else do about it?" she asked. "We'll be out of his reach, and out of Swift's reach, and you say there aren't any winds on this planet, though I don't see why."

"The pressure's so high that the atmosphere doesn't even come close to obeying the classical gas laws," replied Raeker—he was no physicist, but had had to answer the question quite a few times in the last decade and a half— "and the small percentage changes in temperature that do occur result in even smaller changes in volume, and therefore in density, and therefore in pressure. Little pressure difference means little wind. Even changing phase, from gas to liquid, makes so little change in density that the big raindrops just drift down like bubbles, in spite of the gravity."

"Thanks, I'll remember to make sense of that when I get back to school," said Easy. "You're probably right, but you haven't answered my question about how Nick was going to reach us if we went out to sea. Forgive me if I'm spoiling an attempt to change the subject."

Raeker laughed aloud, for the first time in some weeks.

"Good kid. No, I wasn't trying to change the subject; you just asked a question that every visitor for sixteen years has put to me, and I answer it without even thinking. You pushed a button. As far as your question goes, leave it to me. I'm going to talk to Nick first thing in the morning—he couldn't do anything right now."

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"All right," said Easy. "If you're that sure, I won't worry. Now how will we be able to tell when we reach the sea?"

"You'll float, the way you did in the lake, at least when some of the water boils off in the morning. I shouldn't be surprised if you were carried off the bottom even at night when the river reaches the sea, but I'm not certain of it. I don't know how completely or how far down the water dilutes the acid. Keep an eye on the landscape, and if you start to drift up from it let us know,"

"All right. That'll be easy."

But they were still on the bottom when the 'scaphe stopped moving. The human beings at both ends of the communication line had slept in the meantime, but there were still some hours before local daylight was due. Something had slowed the current so that it was no longer able to push the big shell along, and Raeker suspected that the children had reached the ocean, but he admitted there was no way to be certain until day. The intervening time was used up with language work again; there was nothing else to do.

Then the ship began to rise gently off the bottom. The motion was so gradual that it was a minute or two before either of the youngsters was positive it was taking place, and more than three hours passed before the bottom could no longer be seen. Even then they had not reached the surface, or the surface had not reached them, depending on one's viewpoint. It was definitely day by this time, however, and Raeker had lost practically all his doubt about the ship's location. The river had dried up much more quickly, the day before. He told Easy what he was going to do, suggested that she listen in, and then called Nick.

There was no immediate answer, and a glance around the screens showed that both Nick and Betsey were with the herd, half a mile away. He sent the robot rolling toward them, meanwhile repeating his call in more pene-Deduction; Education; Experimentation 137

trating tones. Both herders waved spears in token of understanding, and Nick began to trot toward the approaching machine. Raeker kept it coming, since he saw part of what he wanted at the foot of the hill.

Nick met him just before he reached it, and asked what had happened.

"I'll tell you in a few moments, Nick," he replied. "Could you go to the wagon and get a bucket, and then meet me at the pool down here?"

"Sure." Nick loped back up the hill. Raeker had not had the robot bring the bucket because of a long-established habit of not using the machine's moving parts, such as the handling equipment, more than could conveniently be helped.

The pool he had mentioned lay in the bottom of a circular hollow, as was usually the case. Also as usual, it filled only a small part of the hollow, representing all that was left when the nightly lake which did cover the spot boiled almost dry by day. He had assumed for years, on rather inadequate data but without any contradicting evidence so far, that the stuff was oleum—principally sulphuric acid with a heavy lacing of metal ions from the surrounding rocks which had been dissolved in the nightly rain, and an equilibrium amount of the atmospheric gases. He ran the robot through it to make sure of its depth— the slope of the rock sometimes changed rather abruptly at the "acid line," so judging by eye was insufficient—and then waited until Nick returned with the bucket.

"Is that thing tight, Nick? Will it hold liquid without leaking?" In reply, Nick pushed the leather container beneath the surface of the pool, drew it up brimming, and waited for the fluid on the outer surface to drain away. This happened quickly, since the "leather" was not wet by the oleum, and in a few seconds only a dozen or so hazily defined drops were clinging to the outer surface. Nick held the container up at the end of one arm for another minute or so, but nothing more fell.

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"I guess it's tight, all right," he said at length. "Why is it important? We'll never have to carry this stuff very far; there are pools of it everywhere."

"I'm not interested in keeping it in the bucket, Nick. Empty it again." The student obeyed. "Now set the bucket right side up in the pool, and let go of it—no, don't fill it." The transmission delay made this warning a trifle late; Nick emptied what had gotten into the container and started over. "That's right— on top of the pool. Now let go of it." Nick obeyed. The weight of the strap that served as a handle promptly tipped it over, and three or four gallons of oleum poured in. This weighted the bottom sufficiently to bring the edge to the pool's surface, and there the bucket remained. Nick was startled; he had taken for granted that the thing would plummet to the bottom.

"I'm afraid I've been a trifle negligent with your education," remarked Raeker, "though I suppose the rather ambiguous nature of most of this planet's liquid gives me some sort of excuse for leaving out Archimedes' Principle. Try it again, Nick, and this time put a couple of stones in the bucket first."

As might have been expected anywhere on Tenebra except the actively orogenic regions, there were no loose stones in the neighborhood; but by packing the bottom third of the container with broken-off shrubbery, Nick contrived to achieve the spirit of the Teacher's order. This time the bucket floated almost upright, and with a good deal of freeboard.

"See how much more you can put in it before it sinks," said Raeker. Nick obeyed, without asking for the meaning of the new verb; it was clear enough from context. To his unconcealed astonishment, it proved possible to fill the bucket with the brittle growths without actually forcing it under, though a ripple half an inch high would have accomplished this end—a fact Raeker at once proceeded to demonstrate. At his order, Nick splashed vigorously in the

Deduction; Education; Experimentation 139

pool with his feet; waves curled over the edge of the bucket, and it sank almost at once.

"Do you think it would be possible to make something on that general line, capable of keeping several people from sinking?" asked Raeker.

Nick wasn't sure. "Just on the face of things, I'd say yes," he replied, "but I don't really see why that works at all. If I knew, I could answer more sensibly. What use would it be if we had such a thing?"

Raeker took this opportunity to give a rapid explanation of Archimedes' Principle, plus an account of Easy's reports, mentioning the brief appearance of the cave scout and concluding with the probability that the bathyscaphe had reached the sea. Nick could see the rest of the situation for himself, and, characteristically, went a trifle overboard in his enthusiasm.

"I see!" he exclaimed. "The ship is in the ocean where no one can get at it, so you've showed us how to travel on the ocean itself. We could get out to the ship with this big bucket you want us to make, and pull the ship along with us to the other side, where Swift wouldn't bother us. It's a good idea. We'll start making the bucket as soon as the others come back—in fact, we can start collecting leather for it right now—"

"Hold up a minute, Nick. Crossing oceans, even oceans as small as Tenebra probably has, isn't something you do quite that casually. Also, there's another point to be considered. What if you were out in this—this bucket at night?"

Nick thought briefly. "Why couldn't we carry firewood and torches?"

"You could; but that's not the point. What happens to the ocean at night?"

"It conies up; but wouldn't the bucket go up with it?"

"I'm afraid not. In going up, the ocean decreases enormously in density, and I'm afraid that rather early in the evening you'd find it oozing over the side of your bucket

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•—and you saw what happened just now when the same thing occurred here in front of us."

"Yes," admitted Nick thoughtfully. He was silent for a time. Then he became enthusiastic again. "Wait a minute. The bucket sinks because liquid gets into it, and it is no longer lighter than the liquid it displaces—right?"

"That's right."

"Suppose, then, that instead of ,a bucket we have a closed bag of air? If it's tied shut the sea can't get in, no matter how much it rises."

"But if the sea becomes no more dense than the air?"

"At least when the water boils out of the sea in the morning the bag will float once more."

"All that is true only if your bag doesn't leak at all. I'd rather you didn't risk your lives by staying at sea during the night, though your idea of bags rather than buckets is a good one. It would be smart to make a ship of many bags tied together, so that if some of them do leak you will still float."

"That's plain enough. But why shouldn't we stay out at night? What if night falls before we get the ship across the ocean."

"You won't cross the ocean. You'll work on it during the daytime, and come ashore again at night."

"But how about Swift?"

"I'll take care of him. Don't you plan to keep the agreement we offered to make with him?"

Nick thought for a moment. "I suppose so, if he really agrees. If that was one of his scouts who found the ship last night, maybe he just decided to find it for himself."

"I still think that find was sheer chance. If it should turn out that you're right, we'll solve that one when we face it. Easy is willing to face Swift, she says. Right, young lady?"

"Certainly."

"Do you like Swift?" Nick asked her in some surprise. "I can't forget that he killed two of my friends."

Deduction; Education; Experimentation 141

"I've never met him," Easy pointed out. "I admit it was bad for him to attack your village that way, but probably he couldn't think of any other way to get what he wanted. If you're smart, Nick, I'll bet you could have him doing just what you want—and make him think it's his own idea all the time."

"I never heard of such a thing!" exclaimed Nick.

"Well, listen in if Swift finds us again," replied the girl, with a confident tone that surprised even her father. "You'll learn something."

Rich signed to Raeker to cut off his transmitter for a moment, and made a comment. "I hope that young squirt isn't getting too cocky. I admit she's giving Nick just what I've given her on and off all her life; I just hope she's up to it if the occasion arises. That Swift isn't human, or Drommian either!"

Raeker shrugged. "I'm hoping she won't have to try. In the meantime, I'd much rather have her confident than scared senseless."

"I suppose you're right." Rich looked at the screen, where his daughter's confident expression glowed as she enlarged on her theme to the surprised and still doubtful Nick. Raeker listened with amusement for a while, but finally suggested tactfully that she tell him something about boat-building; Nick knew even less about that than he did about diplomacy, and was more likely to need the information. Easy was perfectly willing to change the subject as long as she could keep talking.

Presently 'Mina, who had kept faithfully to his watchman's duties at one of the windows, called to her with the information that he thought he could see the surface. Easy broke off and left the control room hastily, calling back after a moment that her young friend seemed to be right. It was not until the upper observation windows of the bathyscaphe had actually emerged into the "air" that Raeker remembered something; he had missed an opportunity to check on the mysterious sea life originally 142 CLOSE TO CRITICAL

reported by Nick. Aminadorneldo had made no mention of any such creatures during his last period of watch, but Raeker didn't know the young Drommian well enough to feel sure he'd have reported them without special instructions. This was obviously not the time to ask; Easy's eager tongue was busy with more up-to-date reports.

"We're farther out to sea than you thought we would be, Dr. Raeker," she called. "I can just barely see the shore, at the very limit of our hottest lights. I can't make out any details, really; but I think maybe there are some points, or maybe islands, sticking out our way."

"Can 'Mina see anything more?"

"He says not," came Easy's answer after a brief pause. "He doesn't seem to see quite as well as I do, anyway, I've noticed."

"I see. I suppose you can't tell whether you're moving or not."

"The ocean is perfectly smooth, and there aren't any waves around us. There's nothing to tell by. The only things to see are those big jellyfish things floating in the air. They're moving slowly in different directions, more of them toward shore than away from it, I think. Let me watch them for a minute." It was considerably more than a minute before she could make up her mind that the first impression had been right. Even then she admitted willingly enough that this was not evidence of the bathyscaphe's motion.

"All right," said Raeker when this had been settled. "Just keep an occasional eye on the ocean to make sure nothing happens, and give advice to Nick as long as he'll listen to you. He'll do what he and Betsey can about it, but that won't be much before the others get back. They'll probably be gone until tomorrow night, Tenebra time— between five and six days on your clock."

"All right, Doctor. We'll be fine. It's rather fun watching those flying jellyfish." Raeker opened his mike switch and settled back thoughtfully, and with some satisfaction.

Deduction; Education; Experimentation 143

Everything seemed to be progressing properly; perhaps somewhat more slowly than he would have liked, but as rapidly as could reasonably be hoped. This feeling must have showed on his face, for his thoughts were read quite accurately.

"Pleased with yourself, I take it, Man!" The speaker did not need to introduce himself. Raeker endeavored to control both his features and his feelings, with questionable success.

"Not exactly, Councillor—"

"Why not exactly?" shrilled Aminadabarlee. "Why should you feel any remote sense of satisfaction? Have you accomplished anything at all?"

"I think so," Raeker answered in some surprise. "We know very nearly where your boy is, and we should have a rescue team out there in a week or ten days—"

"A week or ten days! And then you'll have to give the team members degrees in electrical engineering, and then hope the wiring of that ridiculous craft hasn't corroded beyond repair in the interval. How long do you think the actual rescue will take?"

"I'm afraid I couldn't hazard a guess," Raeker answered as mildly as he could. "As you point out so clearly, we don't know how much damage may have been done to wiring exposed by the inspection ports. I realize that it is hard to wait, but they've been getting on all right for a month now—"

"How stupid can even a human being get?" asked the Drommian of the world at large. "You were talking to the ground just now, and heard as clearly as I did the human child's remark that my son didn't see as well as she did."

"I heard it, but I'm afraid the significance escaped me," admitted the man.

"Drommian eyesight is as good and acute as that of human beings, if not better, and my son's has always been normal for his age. If he can't see as well as the human with him, something's wrong; and my guess is that the low

144 CLOSE TO CRITICAL

oxygen concentration is affecting him. I gather your engineers made no particular provision for altering that factor of the vessel's environment."

"They probably didn't, since the crew was to be human," admitted Raeker. "I did not recognize the emergency, I must admit, Councillor; I'll try to find means of speeding up the operation—for example, I can probably get pictures of the wiring exposed by the ports from the engineers, and have Nick briefed on what to look for while he's waiting for the others. My relief is due in half an hour; as a matter of fact, he'd probably be willing to come now if I called him. Have you been able to get medical advice from Dromm yet? I understand a human doctor arrived a few hours ago, and has been finding out what he can about the diet available on the bathyscaphe."

"Eta Cassiopeia is half a parsec farther from here, and I did not get a message off quite so quickly,"

admitted the Drommian. "One should be here shortly, however."

Raeker felt that he had made a smart move in forcing the nonhuman to make such an admission; unfortunately, admitting mistakes under pressure does not improve the temper of the average human being, and Aminadabarlee's race was quite human in this respect. He could not be insultingly superior for the moment; even his standards prevented that; but the required repression of choler was a good deal more dangerous to peace than his usual superciliousness. He retired to his own room—which the "incompetent"

human engineers had at least set up with a decent atmosphere—and brooded darkly. There were many more message torpedoes. ._

With the Drommian gone, Raeker decided not to bring his relief on too early; but as soon as the fellow did show up, he made his way to the engineering section and outlined the proposal he had made on the spur of the moment to Aminadabarlee. Sakiiro and his colleagues agreed that it was worth trying, and they all settled down with their blueprints to decide what would be the best things to tell Deduction; Education; Experimentation 145

Nick and the easiest way to get the information across.

They spent some hours at this. Then Raeker went to eat, and back to his own room to sleep for a few hours. When he reappeared in the observation room, his relief rose gladly.

"Easy has something to report," he Said, "but she wants to tell you personally." Raeker raised his eyebrows, dived into his station, and energized the microphone.

"I'm here, Easy," he said. "What's happened?"

"I thought I'd better tell you, since you're the one who said we'd stay put," the girl responded at once.

"We've been drifting closer to shore for five or six hours now."

Raeker smiled. "Are you sure the shore isn't just getting closer to you?" he asked. "Remember, the sea level had a long way to go down even after you got to the surface."

"I'm quite sure. We've been able to keep our eyes on one piece of shore, and the sea has stayed right by it while we got closer. It has a feature which makes it easy to recognize, though we weren't able to make out very clearly just what the feature was until now."

"What is it?" asked Raeker, seeing that he was expected to.

Easy looked at him with the expression children reserve for adults who have made a bad mistake.

"It's a crowd of about fifty natives," she said.

X. COMPREHENSION; CONSTRUCTION; INUNDATION

NICK, for the hundredth time, looked toward the ocean and fumed. He couldn't see it, of course; to be out of its reach by night the camp had had to be placed well out of its sight by day, but he knew it was there.

He wanted to see it, though; not only to see it but to ride on it. To explore it. To map it. That last idea presented a problem which occupied his mind for some time before he dropped it. Fagin would know the answer; in the meantime there was a boat to be built. That was the real annoyance. Nothing, really, could be done about that until the search teams got back. While it didn't actually take all of his and Betsey's time to watch the herd and gather firewood, neither could do any very effective hunting with those jobs in the background; and the boat was very obviously going to take a lot of skins.

Nick wasn't sure just how many, and to his surprise

Fagin had refused to offer even a guess. This was actually

reasonable, since Raeker, who was not a physicist, was

ignorant of the precise densities of Tenebra's oceans and

atmosphere, the volume of the average leather sack which

might be used in the proposed boat, and even the weight

- of his pupils. He had told Nick to find out for himself, a

.A. remark which he had made quite frequently during the process of educating his agents.

Even this, however, called for a little hunting, since it 146

Comprehension; Construction; Inundation 147

seemed a poor idea to sacrifice one of the herd to the experiment. Betsey was now scouring the surrounding valleys in the hope of finding something big enough to serve—the floaters of the vicinity had already learned to leave herd and herders alone, and those killed or grounded in the process had long since been disposed of by scavengers. Besides, their skins were much too frail to make good leather.

There was no serious doubt that Betsey would find a skin, of course, but Nick wished she'd be quicker about it. Patience was not one of his strong points, as even Easy had already noticed.

He was a little mollified when she came; she had brought not only the kill, but the skin already removed and scaled—a job which Nick didn't mind doing himself, but it was at least that much less tune spent before the actual experiment. Betsey had kept in mind the purpose to which the skin was to be put, and had removed it with a minimum of cutting; but some work was still needed to make a reasonably liquid-tight sack. It took a while to prepare the glue, though not so long for it to dry—strictly speaking, the stuff didn't dry at all, but formed at once a reasonably tenacious bond between layers of materials such as leaves or skin. Eventually the thing was completed to their satisfaction and carried down to the pool where the bucket had floated a few hours before.

Nick tossed it in and was not in the least surprised to see that it, too, floated; that was not the point of the experiment. For that, he waded hi himself and tried to climb onto the half-submerged sack.

The results didn't strike either Nick or Betsey as exactly funny, but when Raeker heard the story later he regretted deeply not having watched the experiment. Nick had a naturally good sense of balance, having spent his life on a high-gravity world where the ground underfoot was frequently quite unstable; but in matching reflexes with the bobbing sack of air he was badly outclassed. The 148 CLOSE TO CRITICAL

thing refused to stay under him, no matter what ingenious patterns he devised for his eight limbs to enable them to control it. Time and again he splashed helplessly into the pool, which fortunately came only up to his middle. A ten-year-old trying to sit on a floating beach ball would have gone through similar antics.

It was some time before anything constructive came of the experiment, since each time Nick fell into the pool he became that much more annoyed and determined to succeed in the balancing act. Only after many tries did he pause and devote some really constructive thought to the problem. Then, since he was not particularly stupid and did have some understanding of the forces involved— Raeker felt he had not been a complete failure as a teacher —he finally developed a solution. At his instruction, Betsey waded into the pool to the other side of the sack and reached across it to hold hands with him. Then, carefully acting simultaneously, they eased the weight from their feet. They managed to keep close enough together to get all the members concerned off the bottom of the pool for a moment, but this unfortunately demonstrated rather clearly that the sack was not able to support both of them.

Getting their crests back into the air, they waded ashore, Nick bringing the bag with him. "I still don't know how many of these we're going to need, but it's obviously a lot," he remarked. "I suppose six of us will go, and two stay with the herd, the way the Teacher arranged it this time. I guess the best we can do until the others get back is hunt and make more of these things."

"There's another problem," Betsey pointed out. "We're going to have quite a time doing whatever job it is Fagin wants done while trying to stand on one or more of these sacks. We'd better pay some attention to stability as well as support."

"That's true enough," Nick said. "Maybe now that we've done some experimenting, the Teacher will be will-Comprehension; Construction; Inundation 149

ing to give us a little more information. If he doesn't, there's that other person whose voice he sends us—

the one he says is in this ship we're to look for— By the way, Bets, I've had an idea. You know, he's been explaining lately about the way voices can be sent from one place to another by machines. Maybe Fagin isn't really with us at all; maybe that's just a machine that brings his voice to us. What do you think of that?"

"Interesting, and I suppose possible; but what difference does it make?"

"It's information; and Fagin himself always says that the more you know the better off you are. I suppose we don't really know this, but it's something worth keeping in mind until evidence comes in."

"Now that you've thought of it, maybe he'll tell iis if we ask him," Betsey pointed out. "He usually answers questions, except when he thinks it's for the good of our education to work out the answers ourselves; and how could we check on this one experimentally—except by taking the Teacher apart?"

"That's a point. Right now, though, the really important thing is to get this boat designed and built. Let's stick to that question for a while; we can sneak the other one hi when there's less chance of getting a lecture about letting our minds wander."

"All right." This conversation had brought them to the top of the hill where the robot was standing, among the belongings of the village. Here they reported in detail the results of their experiment. Fagin heard them through in silence.

"Good work," he said at the end. "You've learned something, if not everything. Your question about stability is a good one. I would suggest that you build a wooden frame—oh, about the size and structure of one wall of a hut, but lying on the ground. Then the sacks can be fastened to the corners; any time one corner gets lower

150

CLOSE TO CRITICAL

than the others, the buoyant force on it will increase, so the whole thing ought to be fairly stable."

"But wood sinks. How can you make a boat out of it?"

"Just count it as part of the weight the sacks—let's call those floats, by the way—have'to carry. You'll need even more floats, but don't let it worry you. I'd suggest that the two of you start the frame now; you might be able to finish it by yourselves, since there's plenty of wood. Then you can start fastening floats to it whenever you can get hold of any; you make a few kills defending "the herd every day, so you should make some progress.

"While you're doing that, you might lend your minds to another problem. The bathyscaphe is not staying at sea, but is drifting toward the shore."

"But that's no problem; it solves our problems. We'll just have to travel south along the shore until we find it.s You had already decided it must be south of us, you said."

"Quite true. The problem is the fact that Swift, with most of his tribe, seems to be standing on the shore waiting for it. Strictly speaking, Easy hasn't recognized Swift, partly because she can't tell one of you from another yet and partly because they aren't close enough, but it's hard to imagine who else it could be. This raises the question of whether Swift is accepting our offer, or proposes to keep the bathyscaphe and those in it for his own purposes. I suppose it's a little early to expect an answer from him; but if we don't get one some time today, I think we'll have to assume we're on our own and act accordingly."

"How?"

"That is the problem I suggest you attack right now. I suspect that whatever solution you reach, you'll find the boat will figure in it; so go ahead with it, as far as you can."

The Teacher fell silent, and his students fell to work. As Fagin had said, there was plenty of wood around, since the camp had not been there very long. Much of it, of course, was unsuitable for any sort of construction, Comprehension; Construction; Inundation 151

having the brittleness of so many Tenebran plants; but a few varieties had branches or stems both long and reasonably springy, and the two were able to locate in an hour what they hoped would be enough of these.

The actual cutting of them with their stone blades took rather longer, and binding them into a framework whose strength satisfied all concerned took longest of all. When completed, it was a rectangle of some fifteen by twenty feet, made of about three dozen rods of wood which an Earth-man would probably have described as saplings, lashed at right angles to each other to form a reasonably solid grillwork. Thinking of it as a floor, neither Nick nor Betsey was particularly happy; the spaces were quite large enough to let their feet through, and the said feet were even less prehensile than those of a human being. They decided, however, that this was an inconvenience rather than a serious weakness, and shifted their attention to the problem of getting floats.

All this was reported to the Teacher, who approved. The approval was more casual than the two realized, for at the moment Raeker's attention was otherwise occupied. The bathyscaphe had now drifted within fifty yards of the shore and had there run aground, according to Easy. She had offered neither observation nor opinion as to the cause of the drift, and none of the scientists who had taken so many reels of data about the planet had been able to do any better. Easy herself did not seem bothered; she was now engaged in language practice across the narrow span of liquid that kept the bathyscaphe out of Swift's reach.

Raeker lacked even the minor comfort of being able to hear the conversation. The microphones of the outside speakers were, somewhat sensibly, located by the observation ports, so that the girl had taken up her station where she would have to shout to be heard in the Vindemiatrix. She did not bother to shout; most of the time she didn't even think of Raeker or, to be embarrassingly frank, of her father. She had not been inter-152 CLOSE TO CRITICAL

ested in the biology, geology, or the virtually nonexistent climatology of Tenebra; her interest in the rescue operation, while profound and personal, had reached the point where she could only wait for information which was always the same; but here were people, and people she could talk to—at least, after a fashion. Therefore, she talked, and only occasionally could anyone above get her attention long enough to learn anything.

She did find out that Swift was one of those present on the nearby shore, and Raeker duly relayed this information to Nick; but when questions were asked such as whether Swift planned to follow the suggestion he must by now have received via Nick's ex-prisoner, or how he had been able to find the bathyscaphe so quickly, no satisfactory answer was forthcoming. Raeker couldn't decide whether the trouble was Easy's incomplete mastery of the language, her lack of interest in the questions themselves, or a deliberate vagueness on Swift's part. The whole situation was irritating to a man who had exercised fairly adequate control over affairs on Tenebra for some years past; at the moment a majority of his agents were out of contact, what might be called the forces of rebellion were operating freely, and the only human being on the planet was neglecting work for gossip. Of course, his viewpoint may have been slightly narrow.

Things looked up toward the middle of the Tenebran afternoon. Jim and Jane returned, long before they had been expected, to increase the strength of the shipbuilding crew. They reported unusually easy travel and high speed, so they had reached their first search area on the initial day's travel, examined it, and been able to cover the other and return in something like half the expected time. They had found nothing in their own areas. They had seen a light to the south, but judged that John and Nancy would cover it, and had decided to stick to their own itinerary and get the desired report in. It was quite impossible, of course, for them to read any expression

Comprehension; Construction; Inundation 153

from the robot, and Raeker managed to keep his feelings out of his voice, so they never suspected that their report was hi any way unsatisfactory. For a short tune, Raeker toyed with the thought of sending them out again to check the light; but then he reflected that in the first place John and Nancy would, as Jim said, have done so, and in the second place the 'scaphe had effectively been located, and he decided the pair were of more use getting leather. The lack of initiative they had displayed tended to support this conclusion. He spoke accordingly, and the two promptly took their spears up again and went hunting.

"One point may have struck you, Nick," Raeker said after they had gone.

"What is that, Teacher?"

"They saw the light to the south of their search area. That suggests strongly that the shore of this sea bends westward as it is followed south; and since the caves of Swift lie in the same direction, it is fairly likely that they are closer to the shore than we realized. This may account for Swift's finding the ship so quickly."

"It may," admitted Nick.

"You sound dubious. Where is the hole hi the reasoning?"

"It's just that I hunted with Swift's people for a good many days, and covered a lot of territory around his caves in the process, without either encountering the sea myself or hearing it mentioned by any of his people. It seems hard to believe that the lights of your missing ship could be seen a hundred miles, and something like that would be necessary to reconcile both sets of facts."

"Hmph. That's a point I should have considered. That light may call for more investigation, after all. Well, we'll know more when John and Nancy come hi."

"We should," agreed Nick. "Whether we actually will remains to be seen. I'm going to get back to fastening this float we've just glued onto the frame. I'm a lot surer that something constructive will come from that." He went

154 CLOSE TO CRITICAL

off to do as he had said, and Raeker devoted himself to listening. Thinking seemed unprofitable at the moment.

With two more hunters, the raft progressed more rapidly than anyone had expected. The region of the new camp was not, of course, as badly hunted out as had been the neighborhood of the old village, and skins came in about as fast as they could be processed. Float after float was fastened in place, each corner being supplied in turn to keep the balance—Nick and Betsey were very careful about that. By the late afternoon so many had been attached that it was less a matter of keeping track of which corner came next than of finding a spot not already occupied—the frame was virtually paved with the things. No one attempted to calculate the result of its stability. If anyone thought of such a problem, he undoubtedly postponed it as something more easily determined empirically.

The work was not, of course, completely uninterrupted. People had to eat, there was the need to gather firewood for the night, and the herd to be guarded. This last, of course, frequently helped in the "shipyard" by providing leather without the need of hunting, but sometimes the fighting involved was less profitable. Several times the creatures attacking the herd were floaters, to everyone's surprise.

These creatures were reasonably intelligent, or at least learned rapidly as a rule to avoid dangerous situations.

They were also rather slow-flying things—resembling, as Easy had said, the medusae of her home world in their manner of motion—so that after a fairly short time in any one spot, when a reasonable number of them had been killed, the survivors learned to leave the herd alone. Nick and his friends had believed this end accomplished for the present camp; but in the late afternoon no less than four of the creatures had to be faced by the herders in not much over an hour. The situation was both unusual and quite painful: while a competent spearsman could count surely enough on grounding such a-creature, it was Comprehension; Construction; Inundation 155

nearly impossible to do so without suffering from its tentacles, whose length and poisonous nature went far to offset their owner's slow flight.

The attention of all four members of the group was naturally drawn to this peculiar state of affairs, and even the work on the raft was suspended while the problem was discussed. It was natural enough that an occasional floater should drift into the area from elsewhere, but four in an hour was stretching coincidence. The group's crests scanned the heavens in an effort to find an explanation, but the gentle air current toward the southwest was still too feeble at this distance from the volcano even to be felt, much less seen. The sky of Tenebra during the daytime is much too featureless to permit easy detection of something like a slow, general movement of the floaters; and the individual movement of the creatures didn't help. Consequently, the existence of the wind was not discovered until rainfall.

By this time, the raft seemed to be done, in that it was hard to see where any more floats could be attached. No one knew, of course, how many people it would support; it was planned to carry it to the ocean when the others returned, and determined this by experiment.

When the evening fires were lighted, however, it was quickly seen that the rain was not coming straight down. It was the same phenomenon that John and Nancy had observed the night before, complicated by the lack of an obvious cause. After some discussion, Nick decided to light three extra fires on the northeast side of the usual defenses, compensating for the extra fuel consumption by letting an equal number on the opposite side of the outer ring burn out. A little later he let go even more on the southwest, since no drops at all came from that direction even after the convection currents of the camp were well established. He reported the matter to Fagin.

"I know," replied the Teacher. "The same thing is happening where the ship is down, according to Easy.

The

156 CLOSE TO CRITICAL

drops are slanting very noticeably inland. I wish she had some means of telling direction; we could find out whether the coast is actually sloping east where she is, or the rain actually moving in a slightly different direction. Either fact, if we know it, could be useful."

"I suppose she can't feel any wind?" asked Nick.

"Not inside the ship. Can you?"

"A little, now that the motion of the drops proves there must be some. I felt more around those fires I lighted when we getting away from the caves, but that's the only time. I think it's getting stronger, too."

"Let me know if you become more certain of that," replied Raeker. "We'll keep you informed of anything from the other end which may have a bearing on the phenomenon." Raeker's use of "we" was apt; the observation and communication rooms were filling with geologists, engineers, and other scientists. The news that Tenebra was putting on its first really mysterious act in a decade and a half had spread rapidly through the big ship, and hypotheses were flying thick and fast.

Easy was giving a fascinating, and fascinated, description of events around the bathyscaphe; for while she and her companion had by now seen plenty of the nightly rainfall, they were for the first time at a place where they could actually observe its effect on sea level. The shore was in sight, and the way the sea bulged up away from it as water joined the oleum was like nothing either child had ever seen. Looking downhill at the nearby shore was rather disconcerting; and it continued, for as the bathyscaphe rose with the rising sea level it was borne easily inland with the bulging surface. This continued until the density of the sea fell too low to float the ship; and even then an occasional bump intimated that its motion had not stopped entirely.

"I can't see anything more, Dad," Easy called at last. "We might as well stop reporting. I'm getting sleepy, anyway. You can wake us up if you need to."

Comprehension; Construction; Inundation 157

"All right, Easy." Rich made the answer for Raeker and the other listeners. "There's nothing much going on at Nick's camp right now except the wind, and that seems more surprising than critical." The girl appeared briefly on the screen, smiled good night at them, and vanished; Aminadorneldo's narrow face followed, and that station had signed off for the night.

Attention naturally shifted to the observation room, where the surface of Tenebra could actually be seen.

Nothing much was happening, however. The robot was standing as usual in the middle of the rather unbalanced fire circle, with the four natives spaced around it—not evenly, tonight; three of them were rather close together on the northeast side and the fourth paced a beat that covered the remaining three-quarters of the circle. It was easy to see the reason with a few minutes' observation; for every fire snuffed out on the single man's beat, a full dozen went on the northeast. Someone was continually having to lope forward with a torch to relight one or two of the outer guard flames on that side. Occasionally even an inner fire would be caught, as a second drop blew too soon through the space left unguarded by the effect of a first. There seemed no actual danger, however; none of the natives themselves had been overcome, and their manner betrayed no particular excitement.

While Raeker had been eating, his assistant had had one of the pupils pace off a course which he compared with the robot's length, and then by timing the passage of a raindrop along it clocked the wind at nearly two miles an hour, which as far as anyone knew was a record; the information was spread among the scientists, but none of them could either explain the phenomenon or venture a prediction of its likely effects. It was an off-duty crewman, relaxing for a few minutes at the door of the observation chamber, who asked a question on the latter subject.

"How far from the sea is that camp?" he queried.

158 CLOSE TO CRITICAL

"About two miles from the daytime coast line."

"How about the night one?"

"The sea reaches the valley just below that hill."

"Is that margin enough?"

"Certainly. The amount of rainfall doesn't vary from one year to the next. The ground moves, of course, but not without letting you know."

"Granting all that, what will this wind do to the shore line? With the sea not much denser than the air, the way it is late at night, I should think even this measly two-mile hurricane might make quite a difference."

Raeker looked startled for a moment; then he glanced around at the others in the room. Their faces showed that this thought had not occurred to any of them, but that most— the ones, he noted, most entitled to opinions—felt there was something to it. So did Raeker himself, and the more he thought of it the more worried he became. His expression was perfectly plain to Rich, who had lost none of his acuteness in the last month of worry.

"Think you'd better move them back while there's time, Doctor?" he asked.

"I'm not sure. It isn't possible to move the whole camp with just the four of them, and I hate to leave any of their stuff to be washed away. After all, they're fifty feet higher on that hill than the sea came before."

"Is fifty feet much, to that sea?"

"I don't know. I can't decide." The expression on Rich's face was hard to interpret; after all, he had spent his life in a profession where decisions were made whenever they had to be, with the consequences accepted as might be necessary.

"You'll have to do something, I should think," he said. "You'll lose everything if the sea gets them while they're there."

"Yes, but—"

"But nothing! Look there!" It was the same crewman who had raised the wind question who cut into the ex-Comprehension; Construction; Inundation 159

change. His eyes were fixed on the screen which looked seaward, and both Raeker and Rich knew what he had seen in the split second before they were looking for themselves. They were quite right.

Hours before they were normally due, the oily tongues of the sea were creeping into sight around the bases of the eastern hills. For perhaps a second no words were uttered; then Raeker proceeded to destroy the image the diplomat had been forming of him—that of a slow-thinking, rather impractical, indecisive

"typical scientist." With the safety of project and pupils in obvious and immediate danger, he planned and spoke rapidly enough.

"Nick! All of you! Take one second to look east, then get to work. Make sure that all the written material, maps especially, is wrapped securely and fastened to the raft. Make them firm, but leave enough rope to fasten yourselves to it as well. You and the maps are top priority, and don't forget it.. With those as safe as possible, do the best you can at securing your weapons to yourselves or the raft. Hop to it!"

A question floated back from Nick; the transmission lag made it uncertain whether or not he had availed himself of the proffered observation time.

"How about the cattle? Without them—" Raeker cut in without waiting for the end.

"Never mind the cattle! There's a big difference between what's nice to do and what's possible to do! Don't even think about anything else until you've taken care of yourselves, the maps, and your weapons!"

Nick's three companions had started to work without argument; the urgency in the Teacher's voice drove Nick himself to follow suit in silence, and a tense period of waiting ensued in the observation room. The distant watchers sat breathless as the work and the ocean raced each other—a race more deadly than any of them had even seen run on an Earthly track.

Raeker noticed that the streams of oleum were much

160 CLOSE TO CRITICAL x higher in the center than at the edges, rather like greatly magnified trickles of water on waxed paper, even though they still showed a fairly distinct surface; evidently the sea had already been heavily diluted by the rain. That meant there was no point in expecting the raft to float. Its air-filled sacks were nearly half as dense as the straight acid; with this diluted stuff their buoyancy would be negligible.

He was almost wrong, as it turned out. The sea oozed up around the hill, snuffing the fires almost at a single blow, and for an instant blurred the picture transmitted from the robot's eyes as it covered the camp.

Then the screens cleared, and showed the limp figures of the four natives on a structure that just barely scraped what had now become the bottom of the ocean. It moved, but only a few inches at a time; and Raeker gloomily sent the robot following along.

XI. ORGANIZATION; REVELATION; DECLARATION

NIGHTS—Tenebran nights, that is—were hard on the Drommian, Aminadabarlee. They were even harder on any men who had dealings with him while they lasted. Seeing people engaged in work that had no direct bearing on the rescue of his son, and watching them for two Earthly days at a stretch, was hard for him to bear, even though he knew perfectly well that nothing could be done while the agents on the ground were immobilized or

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actually unconscious. This made no difference to his emotions; somebody, or everybody, should be doing something, his glands told him. He was rapidly, and quite unavoidably, coming to regard human beings as the most cold-blooded and uncooperative race in the galaxy. This was in spite of the skilled efforts of Rich, who had plenty to keep him professionally busy.

So far the great nonhuman had not descended to physical violence, but more than one man was carefully keeping out of his way. These were the ones least familiar with Drommians—so far. Raeker had noted that the number was increasing.

Raeker himself wasn't worrying; he wasn't the sort. Besides, he was occupied enough to keep his mind off Dromm and its impulsive natives. The robot, fortunately, had had no fighting to do, since nothing in the form of animal life had approached the raft and its helpless pas* sengers, or had even been sighted by the carefully watching robot. This was a relief in one way, though Raeker was professionally disappointed. He had wanted to learn something of the creatures who were responsible for the loss of his students' herd a few nights before, and who could apparently live in a remarkably small oxygen concentration. Still, the four tied to the raft were fairly safe, though no one dared let them drift far from the robot; a constant watch was necessary.

As the night wore on, the vagrant currents which had been shifting raft and occupants became fewer, and so much weaker that they were no longer able to move the assembly, whose effective weight must have been only a few pounds. The man in control of the robot found it possible to leave the machine motionless for longer and longer periods; in fact, at one point Raeker almost went to sleep in the control chair. He was aroused from a doze by the shrill voice of the Drommian, however—"And Earth-men expect people to work with them!" in what even a man could recognize as a contemptuous tone—and did 162 CLOSE TO CRITICAL

not repeat the slip. It didn't matter; the raft's passengers were drifting unharmed when day arrived. This period was the hardest, as far as standing guard was concerned; as the water began to boil back out of the sea, the latter's density increased, and the raft began to float. It was extremely fortunate that there were by then no currents at all; raft and passengers went straight up. Unfortunately, but somewhat naturally, it turned upside down as it went, so that for a couple of hours the robot operator had the annoyance of seeing the natives hanging from the underside of the floating platform while they very gradually led the surface of the ocean back toward the ground. They had drifted away from the hilltop during the night, and eventually wound up floating in a relatively small pool in one of the nearby hollows. When it finally became evident that the pool would shrink no farther, the robot had to take action.

Fortunately, the oleum was shallow—so shallow that the raft was supported more by the bodies under it than by its own buoyancy. Raeker guided the machine through the liquid, pushing the four unconscious natives ahead of it to the other side. The raft naturally came along, but eventually the rather untidy heap was dripping at the edge of the oleum pool, with the foundation members struggling gradually back to consciousness.

By this time the bathyscaphe was also out of the sea. Like the raft, it had wound up in a pool at the bottom of a valley; unlike it, there was no question of its floating. The pool was too shallow. As a result, Easy and her friend found themselves in their pressure-tight castle fully equipped with a moat, which effectively prevented Swift and his crew from reaching them.

For Swift was there. He turned up within an hour of the time the pool had finished shrinking, in spite of the considerable distance the bathyscaphe must have drifted during the night. It was out of sight of the sea, Easy reported; the wind that had been moving everything else

Organization; Revelation; Declaration 163

inland had brought the ship along. It didn't bother her; she said that they were getting along splendidly with Swift, and didn't seem too worried when told about Nick's reverses of the night. Rich lost his temper for the first time when he learned that Raeker had carelessly told the child about the destruction of the camp, and didn't regain it until the girl's voice made it perfectly clear that the story hadn't affected her morale.

Raeker himself was thinking less about her than about his rescue operation, at the moment; that was why he had been so careless with his words. Nick and Betsey, Jim and Jane were all safe; the maps had remained attached to the raft, and so had most of the weapons. However, it was going to take a little while to find just where they were, short as the distance they had drifted probably was; and when they did find the camp site, it seemed rather unlikely that they would find much else. The herd would be gone, or nearly so; the wagon—who could tell? A similar period under an Earthly ocean would write it off completely, even in the off chance that it could be found. Here, there was no saying, but Raeker was not optimistic.

Finding the site of last night's fire proved easier than expected. The wind proved to be a clue, when it finally occurred to someone—Jim, rather to Raeker's surprise. He and Jane, of course, had bucked it all the way back from their search areas, though they had not attached any meaning to it at the time; now it served to restore the "sense of direction" which for Tenebrans as for humans was a compound of memory and the understanding of elementary natural phenomena. Once they knew the direction of the sea, there was no more trouble; there was no question that they had drifted pretty straight inland. The wagon and the remains of the watch fires were found in an hour. Raeker was really startled to find it and its contents intact; the mere fact that the two-mile hurricane had changed from gas to scarcely denser liquid had made no difference to most of the solid objects in its path.

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"I think we can save a little time," he said at length, when the status of the group's belongings had been determined. "We can go back to the sea now, carrying the boat with us. We'll leave the cart, with a written message for the others; they can either follow us or start moving camp, depending on what seems best at the tune they get back. We'll test out the boat, and search as far south along the coast as tune permits today."

"What do you mean by that?" asked Nick. "Do we search until dark, or until there's only enough time to get back here before dark?"

"Until nearly dark," Raeker replied promptly. "We'll go south until we decide it's far enough, and then go straight inland from wherever we are so as to get away from the ocean hi time."

"Then the others had better move camp no matter what time they get back, and head south with the cart.

We're going to have a food problem, and so are they, with the herd gone."

"Gone? I thought I saw quite a few, with Jim and Jane rounding them up."

"That's true, they're not all gone; but they're down to where we can't afford to eat any until a few more hatch. We couldn't even find scales of the others, this time."

"You couldn't? And I didn't see any creatures traveling around while you were hi the sea, either. It seems to me that your missing cattle are more likely to have strayed than been stolen."

"That may be, but they're gone hi any case, as far as we're concerned. If all four of us are heading for the sea right away to test this boat, we won't be able to look for them."

Raeker thought rapidly. Loss of the herd would be a serious blow to his community; remote-control education cannot, by itself, transform a group of people from nomadic hunters into a settled and organized culture with leisure time for intellectual activity. Without the herd Organization; Revelation; Declaration 165

Raeker's pupils would have to spend virtually all their time finding food. Still, they would live; and unless Easy and her companion were collected pretty soon they probably wouldn't. The question really, then, was not whether any could be spared from the cattle-hunt but whether one or two or all would be more useful in testing the boat and, if the test were successful, subsequently searching for the bathyscaphe from it.

Certainly two people were less likely to sink the thing than four. On the other hand, four could presumably drive it faster—Raeker suddenly recalled that neither he nor Nick had given any thought to the method of propulsion the raft was to have. He supposed paddles or something of that nature would be about the only possible means; the thought of trying to teach Nick the art of sailing on a world where the winds were usually nonexistent and the nearest qualified teacher sixteen light years away seemed impractical. With muscle power as the drive agent, though, the more muscles the better.

"All of you will come to the sea. We'll consider the herd problem later. If the boat won't carry all of you, the extra ones can come back and hunt for cattle. This search is important."

"All right." Nick sounded more casual than he actually felt; all his life, as a result of Raeker's own teaching, he had felt that the safety of the herd was one of the most important considerations of all. If this search were still more so, it must really mean something to the Teacher; he wished he could feel that it meant as much to him. He didn't argue, but he wondered and worried.

The four of them were able to carry the boat easily enough, though bucking the wind made matters a little awkward—the wind was even stronger today, Nick decided. In a way, that was good; a last backward glance at the deserted remnants of the herd showed that a huge floater was being swept past them by the savage current and, in spite of all its efforts, could not beat its way back 166 CLOSE TO CRITICAL

to the relatively helpless creatures. Nick pointed this out to his companions, and they all felt a little better.

The two miles to the sea were covered fairly rapidly, and no formalities were wasted in testing the boat. It was carried out into waist-deep oleum and set down, and the four promptly climbed aboard.

It supported them—just. The floats were completely submerged, and the framework virtually so. The difficulty was not one of keeping on the surface, but of keeping more or less level. The four were all of almost the same age, but they did differ slightly in weight. One side of the raft persisted in settling deeper whenever they stopped moving; each tune this happened they all, naturally, made a scramble for the rising portion, and each time they inevitably overcontrolled so that the raft rocked and tipped precariously first one way and then the other. It took several minutes and much misdirected action and speech before they learned the trick; then they took longer still to learn the use of the paddles Fagin had told them how to make. The robot itself was not too much use; if it stayed ashore its operators couldn't see things on the raft very clearly, and it it crawled into the sea to any point near the vessel it couldn't make itself heard—the boundary between oleum and air was sharp enough to reflect sound waves pretty completely.

"Why do you have them looking at all?" Aminadabar-lee asked acidly at this point. "The robot can travel along the shore as fast as they can paddle that ridiculous craft, and the bathyscaphe isn't at sea anyway. If you think those pupils are going to be of any use, why not have them walk with the machine?"

"Because, while all you say is true, the kids are inaccessible to the natives unless a boat is present. It doesn't seem likely that we'd save time by having Nick and his friends search on foot, and then have to go all the way back for the boat when they found the 'scaphe."

"I see," said the Drommian. Raeker cast a quick glance Organization; Revelation; Declaration 167

at him. The fellow was being unusually agreeable, all things considered; but the man had no time to ponder possible reasons. Nick and his companions were still too much hi need of watching. He spoke over his shoulder, however, remembering Rich's injunction about being as courteous as possible to the big weasel. "There's one thing that might help a great deal, though. You've been talking to your son all along, just as Councillor Rich and I have been talking to Easy; do you suppose he'd be the better for something constructive to do down there?"

"What?"

"Well, if he's as good at picking up languages as Easy was supposed to be, maybe he'd do a better job than she at rinding something out from the cave dwellers. Swift quite obviously knows where both our camp and the bathyscaphe are; it would be most helpful if someone could worm a set of directions out of him for getting from the one to the other."

The Drommian's face was unreadable to Raeker, but his voice suggested what from him was high approval.

"That's the first sensible remark I've heard from a human being in the last five weeks," he said. "I'll explain to Aminadorneldo what to do. There's no point in expecting the human girl to do it herself, or to help him." The diplomat must be credited with what for him was the ultimate in tact, courtesy, and self-control—he had restrained himself from remarking that no human being could be expected to be helpful in a situation calling for intelligence.

He decided to go to the communication room in person, instead of working from Raeker's station—the relay system was efficient, but located in a corner which was rather inconvenient to him for anatomical reasons. Unfortunately, when he reached the other compartment it was even worse; the place was crowded with human beings. Rearing the front half of his long body upward he was able to see over them without any trouble, and discovered

168 CLOSE TO CRITICAL

that the screen of the set tied in with the bathyscaphe was imaging the face of the human child. His own son was also visible, very much in the background, but only the human voice was audible—as usual, he reflected. The men were listening intently to her, and Aminadabarlee quite unthhikingly stopped to do the same before ordering the interfering creatures out of the way.

"No matter how we ask the question, we always get the same answer," she was saying. "At first, he seemed surprised that we didn't know; he's gotten over that now, but still says that Nick and Fagin told him where we were."

"No matter how often you say that, it sounds silly to me," retorted one of the scientists. "Are you sure it's not language trouble?"

"Perfectly sure." Easy showed no indignation, if she felt any at the question. "You wanted to know how he found us so easily, and that's what I asked him. He claims he was given the information he needed by Nick, who had it from the robot, and that's what I told you. I don't remember exactly what was said to that prisoner when Nick's people had him; but you'd better play back the transcript and see what you can get out of it. Either the prisoner himself was able to figure it out from what Nick said to him, or Swift was able to do it from the prisoner's repetition. The first seems to make more sense, to me." There were few flies on Easy Rich. Aminadabarlee wouldn't have agreed with that, of course; her admission that she couldn't remember exactly what had been said in a conversation she had overheard lowered her considerably in his estimation. However, even he couldn't understand, any better than the listening scientists, what the cave dwellers had been able to learn from a brief description of country they had admittedly never seen.

Then an idea occurred to him, and he dropped back to the horizontal position for a few moments to think.

This might really do some good; he almost felt guilty at the

Organization; Revelation; Declaration 169

thought that he'd left all the serious planning in this matter to the human beings. If they'd only keep quiet for a minute or two and let him get his idea straight— But they didn't. They kept on calling excited remarks and questions to the child so far away.

"Wait a minute!" It was a geophysicist who suddenly came up with a point. Aminadabarlee thought, but he didn't pay enough attention to be really sure. "This may be a little far-fetched; but a lot of fairly primitive peoples on Earth and other places get pretty darned good climate predictors—our ancestors knew when spring was coming, you know, and built places like Stonehenge."

"What's the connection?" Several voices asked this question, though not all in the same words.

"This planet has no weather, in our sense of the word; but its geomorphology goes on at a time-rate which almost puts it in the climate class. I just remembered that Nick's prisoner was told that the bathyscaphe stayed on one lake, motionless, for several days, and only then started to drift down a river to the sea. If we're right about Tene-bran weather, that must have been a brand-new river! That information was enough for any native—at least for any one who hadn't been cut off from the history or folklore or whatever the Tenebran equivalent may be of his race. They may never have been right on the scene of that river, but it was close enough to their regular stamping grounds so they could tell where it must lie."

"I'm going to check the lab alcohol," commented one listener. The remark put the proponent of the new idea on his mettle.

"Easy!" he called. "You heard what I just suggested. Ask Swift if it's not true that he knows when things like new rivers and rising hills are going to happen. Ask him how he dares to live in caves in a cliff—

which as far as \ any of us can see is apt to be knocked down by a quake 1 any day!"

j

"All right," the girl said calmly. Her face vanished from I 170 CLOSE TO CRITICAL

the screen. Aminadabarlee was too furious to notice that she had gone. How dare these little monsters take his very own ideas right out of his mind, and claim them for their own? He hadn't quite worked out the details of his notion, but it was going to be the same as the one the human scientist had broached; he was sure of that. Of course, maybe it was a bit far-fetched—of course it was, now that he thought of it a little more carefully. The whole idea was the sheerest speculation, and it was a pity that the girl had been sent to waste time on it. He'd go in and show its weaknesses to his son, and suggest a more fruitful modification, as soon as he worked out its details—only then did he notice that Aminadorneldo had also disappeared from the view screen; he must have gone with the human girl. Well, that was all right; there was a little more thinking to be done, anyway. He kept at it for fifteen or twenty minutes, scarcely noticing the human conversation around him, until the children reappeared. They reported without preamble and without apparent excitement.

"You seem to be right," Easy said. "They seem surprised that anyone wouldn't know when a place was going to become active in quakes, or when a lake was going to spill, and in what direction. They know it so well themselves that they have a good deal of trouble telling me what they use for signs." The geophysicist and his colleagues looked at each other almost prayerfully.

"Don't let them stop trying!" the first one said earnestly. "Get down everything they say and relay it to us, whether you understand it or not. And we were going to use Raeker's students to learn the crustal dynamics of this planet!"

This irrelevance was the last straw, as far as Aminadabarlee was concerned. Without regard to rules of courtesy, either human or Drommian, he plowed into the communications room, his streamlined form dividing the human occupants as a ship divides water. He brought up in front of the screen and, looking past Easy's imaged face

Organization; Revelation; Declaration 171

as though the girl were not there, he burst into an ear-hurting babble of his own language, directed at his son. None of the men interrupted; the creature's size and the ten-clawed limbs would have given most of them ideas of caution even if they had known nothing of Drommians. As it was, Councillor Rich had spread some very impressive bits of information through the complement of the Vindemiatrix, so ideas weren't necessary.

The shrill sounds were punctuated by others from the speaker; apparently the son was trying to get an occasional word into the conversation. He failed, however; the older being's speech only stopped when he appeared to have run out of words to say. Then it was not Aminadorneldo who answered.

It was Easy, and she answered in her own language, since even her vocal cords couldn't handle Drommian speech.

"We've already told him, sir. Dr. Raeker asked me to let you know when you showed up; you had just left his room when we got the information to him, and I didn't see you until just now. He's told Nick, and the boat should be as close as they can bring it on the sea well before night. They'll start to bring it inland then; Swift says they should be able to see our lights from the sea, so the robot has started back to the camp to meet the others and start them on the way here."

The Drommian seemed stunned, but remembered enough of his manners to shift languages.

"You had already asked Swift to tell the way from the camp to where you are?" he asked rather lamely.

"Oh, yes. 'Mina thought of it some time ago. I should have told Dr. Raeker or one of you sooner." The news that it had been his son's idea calmed Aminadabarlee considerably; privately, most of the men in the room wondered how much truth the girl was speaking. They knew the effective age of the young Drommian, and they were coming to know Easy.

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