130.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 p.r.o.nounce. 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 pa.s.s, 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 p.r.o.nounce 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 p.r.o.nounce Drommian? She understands it as well as I do, though."

"Well, I wouldn't bet very much that she could p.r.o.nounce Tenebran, either. It's got some sort of pitch-in- flected 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 pa.s.sed 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 CLOSE TO CRITICAL.

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 b.u.mp, 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 mov- ing, 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 offsh.o.r.e 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 cla.s.sical 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 b.u.t.ton. 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."

136 CLOSE TO CRITICAL.

"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 sh.e.l.l 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 pa.s.sed 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 ap- proaching 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 a.s.sumed for years, on rather inadequate data but without any contradicting evidence so far, that the stuff was oleum-princ.i.p.ally 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 br.i.m.m.i.n.g, 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.

138 CLOSE TO CRITICAL.

"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 140 CLOSE TO CRITICAL.

*-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 ash.o.r.e 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 c.o.c.ky. 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 amus.e.m.e.nt 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 sh.o.r.e, 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 sh.o.r.e 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.