Phases In Chaos
(1991)*
Hal Clement

I. Above

	At the moment the berg tilted, taking everyone and everything off guard, Rekchellet was sketching busily. He was taking advantage of a clear, cold, dry, and probably brief wind from Darkside. It was not that there had been no notice; there had been tremors, and then a crackling roar, in plenty of time to provide warning if only they had been a little more specific. They seemed to come from all directions, offered no clue to their cause, and, in Rekchellet's own mind, left him and his fellows with no option but to get on with their business. When the ice dropped suddenly and sharply from underfoot it was a total surprise, and four beings and two objects could only react at their most basic levels.

	Venzeer and Rekchellet took to their wings instantly and unthinkingly, the recorder's pad and stylus dropping to the ice. The great balloon antenna had inertia enough to snap all four of its moorings, and being ballasted at slightly positive lift began to drift slowly upward. The supply carrier, left momentarily in the air by the dropping surface, drifted back down. Finding the ground no longer horizontal it began to move downhill, since this iceberg was clean enough to be slippery. Janice and Hugh Cedar, attached to the vehicle by what were meant to be safety lines, shared its brief fall and began to follow it unwillingly toward the nearby lake of meltwater.

	The carrier would of course float and the supplies inside its sausage-shaped bubble were individually sealed, so the situation was more annoying than threatening; but none of the beings took it calmly. They were much too startled.

	"Why weren't the brakes on, ground crawlers?" snapped one of the Crotonites. The woman was too busy hand-over-handing along her line toward the sliding vehicle to answer; Hugh, less concerned and less patient, retorted, "Get the balloon! We can have a court of inquiry later."

	The winged members of the team were already flapping after the fifty-meter antenna, which was obviously their business, and there were no more words for fully a minute. Janice reached her goal quickly enough, found the lever she wanted, and sent the spikes of the right steering runner jabbing into the substrate. Even in the local gravity enough momentum had built up to spray her with ice shavings as the carrier swerved toward her. By the time Hugh had reached the lever on his own side the vehicle had stopped. He pulled the handle anyway.

	"Get this one!" Rekchellet was a few meters up, as close to hovering as his wing design allowed, holding one of the mooring lines close to the balloon and letting the rest dangle toward the Erthumoi. Hugh seized the lower end, laced it though the lashing eye nearest him, and made fast.

	"Any more?" he called.

	"The others all broke near the top. You'll have to untie them from the ice anchors and toss an end up to us. It'll be hard to do knots if there's tension; leave the bottom free until we've finished."

	"All right," Janice answered. Like her husband she knew that the Crotonites would have felt insulted by such detailed instructions if they had been on the receiving end; less like him, she would never make an issue of it. The creatures couldn't help regarding nonflyers as fit only for menial tasks such as driving ground equipment. Fortunately, recapturing the balloon offered few problems since the wind had dropped. Neither species had reason to criticize the other. All four of the team members, however, were concentrating on the mooring job when the next rope broke.

	This was Hugh's safety line.

	Surface waves move slowly in weak gravity, but they do move. The sudden tilt of the giant iceberg had sent the lake sloshing away from the carrier and far up a funnel-shaped bay at its sunward end. Reflection of the reddish sun from the water and the ice would have kept the party from seeing clearly that way even if they had been looking. There was little ground friction; the ice had been melting for decades and its surface, while far from flat, had no sharp corners or really rough spots. Even the vegetation was sparse and loose on this part of the berg, so the returning wave lost energy very slowly.

	The water poured back into its former basin, continued up the near side, and reached the explorers from just to the right of the carrier's front before even the flyers noticed any danger. The woman was slammed violently into the vehicle. Hugh, standing farther away on the other side, was hurled to the end of his line; if this had held, he would have been crushed by a dozen metric tons of mass—over twenty-two-hundred kilograms of weight even on Habranha—as the bubble rolled over the spot where he had been. By that time, though, he was meters away.

	The Crotonites responded instantly and silently. Venzeer swooped and snatched up Janice as the rolling vehicle carried her over it. Her line was still attached, and for a moment it seemed that both might be drawn under the bubble. The physicist had seen the danger, however, and snatched a knife from his tool harness as he dived. A slash of the blade disposed of the risk.

	Rekchellet had more trouble. Hugh was a moving target at first, and a snow squall had replaced the calm of moments before, so the Crotonite's first two swoops missed. Then the man was stranded briefly as the wave reached its limit. His body was mixed up with bushes torn loose by the wave, but these seemed wet enough not to be much of an explosion risk—like the Crotonites themselves, the locally evolved life used azide ion as terrestrial beings used ATP. The flyer trusted the electrical insulation of his suit enough to take a chance, and with a screech of triumph lifted Hugh away before the backwash could catch him. Erthumoi were a heavy load even on Habranha, though, and the flyers settled as near as they dared to the water.

	The sloshing was becoming more circular, and no more waves reached the carrier. Some of the bushes stranded near it were smoldering, however, wet as they were, and the rescuers avoided them. Venzeer flew quickly to check the supplies, while Rekchellet began a search for his drawing equipment.

	Hugh paid no attention to them. Janice was lying where Venzeer had set her down, and the moment the man could get to his feet he made a single leap to her side.

	"Jan! Honey! Can you hear me? Are you all right?" There was no immediate answer, and he began checking for injuries as well as the bulk of her suit permitted. He could see that she was breathing, and the garment's status patch just below her throat assured him that her heart was beating. It also told him what medication was being applied. Apparently a bone was broken. Careful checking indicated that this was almost certainly not a limb, but left him to worry about skull and spine and to hope for mere ribs.

	Whatever it was would knit within fifteen minutes unless he overrode the suit's treatment. There seemed no reason to do this; there was no visible need for setting, and even if vertebrae were involved her spinal cord would almost certainly be safer if the surrounding bone healed before she was moved or tried to move herself. Hugh could not tell whether she was unconscious from medication or concussion; he could only wait, eyes alternating between face and patch, until she woke up or the treatment ended. He was interrupted before either happened.

	"Is she badly hurt?" Rekchellet settled to the ice, attaching the recovered sketch pad to his harness and leaving his wings spread for a few seconds to shed body heat. Most human beings would have taken for granted that he was merely concerned for the mission; Crotonites had a poor reputation for emotions like friendship and sympathy. Hugh, however, had acquired much of his wife's innate tendency to like people regardless of their shape, and he took the question at face value.

	"Too soon to say. Do you need me?"

	"I don't think so. I don't know whether any of the moorings broke again, but Venz seems to have fixed them to the sled if they did." The squall had ended; antenna and vehicle were visible once more. "If we'd done that in the first place, they'd probably never have broken, since the carrier didn't jerk down as fast as the ground."

	"Because it got left behind. We secured to the ice for steadiness, so the thing wouldn't move, which was our mistake. Are signals still coming?"

	"I guess so, if they are signals. Venz's been working the analyzer since he finished making fast. I haven't talked to him; I've been looking for this pad." Rekchellet had unclipped his drawing gear again and was recording Janice and her suit readings. "You're right," he added. "We should have brought equipment to make duplicate copies."

	"The flyer would have had to carry it, and then we'd have had to—"

	Rekchellet paid no attention to Hugh's interjection. "I was pretty worried for a few minutes, until I found this." He finished his sketch, clipped pad to harness, and brooded briefly. "I still think the pattern sounds like Habranha speech, but it's been coming from below, and I can't believe a sensible flying person would be underwater."

	"Or inside an ice—wait!" Hugh had seen his wife stir. A moment later she grimaced and opened her eyes. She looked at Hugh and the Crotonite briefly, obviously gathering her wits; then she gave a rather sour smile, and spoke.

	"My chest hurts. If it was you, I've told you before to take it easy. And how long have I been out? I see it's been snowing again."

	Hugh hadn't noticed the change in wind or even the advent of the squall until she spoke.

	"It wasn't," he assured her, not referring to the weather. "A wave knocked you against the carrier. Med tab says broken bone. I'm glad it's only a rib, if it is. Can you work your arms and legs? How does your head feel?" She moved all limbs cautiously, easing Hugh's worry about her spine. "All right; stay put until whatever else it is knits. It shouldn't be long; you've been out for minutes. Rek thinks the signals are still coming."

	This news, as intended, took Janice's mind off her discomfort. She spoke thoughtfully. "I still can't figure that out. The direction's been changing, but it's always generally down. No changes have tied in with weather shifts. The line goes through at least eight or ten kilometers of this iceberg. Maybe twice that, since we don't know the berg's shape below the water line. Then it presumably reaches clear ocean, and no telling how much farther it goes in that. Since the source seems to be moving it can't be someone buried in the ice—and no Habra I've met had a loud enough radio voice to get through even two kilos of the usual ground here."

	"They are competent technicians," Rekchellet pointed out. "They could use amplifiers. In fact, they do. They don't like to, of course, since they speak and hear by radio directly and amplified signals hurt them, but they have the skill." The Erthumoi knew this, like all aliens on Habranha who wanted to use radios and couldn't because of the native peculiarity. Hugh and Janice regarded it as more understandable than the Crotonite preference for preabstracted records—drawings—- over photographs, but kept to more immediate matters now.

	"What native words have you recognized in the patterns? Any real conversation?" asked Hugh slowly.

	"No. Just one word. 'Here. Here. Here.' With varying patterns sometimes following—never preceding—which neither of us could recognize."

	The Erthumoi looked at each other. "Could be an automatic transmitter on a deep-sea research device," Hugh said after a while. His wife nodded.

	"It fits. It also fits your notion that no sensible flyer would be underwater." She smiled at Rekchellet. "And with your inability to get them interested in star travel." She turned up her suit heat; the wind had suddenly become colder, though the air was still clear. "Their ocean is as much of a challenge as space, and of far more immediate importance to them."

	The Crotonite looked enthusiastic at the first part of her remark and appeared about to agree, but paused and took on what both watchers recognized as a thoughtful expression at the second.

	"I suppose so." His wings shifted uneasily, and he glanced toward the antenna a hundred meters away where his companion was still busy. Both human beings knew that Crotonites were divided on the matter of persuading or pressuring Habranha's natives to join the six known starfaring communities—the seventh was still in the province of archeologists. Some, like Venzeer, wanted another winged species to offset the influence of ground crawlers and swimmers on the patterns of interstellar trade and diplomacy. Others seemed to prefer the lonely splendor of being the only flying star travelers, or possibly were worried about competition for worlds suitable for winged intelligences. Husband and wife glanced briefly at each other and changed the subject.

	"You think they could build something able to take deep sea pressures, then, don't you?" Hugh asked. "One can see why they'd want detailed information on current patterns. Continental drift really means something here, with the continent made of ice, hundreds of kilos of ocean depth, and Sunside to Darkside heat circulation." Neither he nor his wife was really familiar with Habranha, as they had been on the world only a few weeks. They had seen the ring-shaped continent of floating ice as they approached from space, and understood generally how it was continually melting away on its sunward side and being rebuilt on the other by icebergs drifting from the dark hemisphere. Like other aliens, and the natives themselves, they were not clear how a tide-locked planet could have such complex and variable weather, though there was a general belief that the complicated ocean circulation was somehow involved. Venzeer and Rekchellet, like other Crotonites, had been trying to learn something new and useful about Habranha to improve their own image with the natives; the Rocks had been hired as skilled help.

	"Of course they can." The translating equipment carried the Crotonite's snort of contempt clearly enough. "They mine silicate mud from the bottom, five hundred kilos down, for their farms; it takes irrigation with minerals to make the ice fertile. The technology for a solid automatic transmitter which wouldn't even have to resist depth pressure is trivial. Information about currents is important to them, and obviously they couldn't explore the depths personally. We're not very far from what they call the Solid Ocean which covers all Darkside and some of the sunlit hemisphere on the surface. The natives say there also seem to be glaciers extending for hundreds of kilometers from there out over the mud on the ocean bottom. We should be over that, if they're right. They couldn't mine around here even if it were conveniently close to the ring horizontally. So I like your suggestion of a research transmitter."

	Hugh, but not Janice, felt a touch of condescension in the speaker's tone. "It will be interesting to examine it if it surfaces, and it does seem to be coming up."

	"Maybe some of the locals will be coming to meet it," said the woman thoughtfully. "It could be surfacing automatically or being brought up for servicing and readout. Perhaps we should get over to the edge and see. Should you broadcast to let them know we're here? You can handle the local speech."

	Rekchellet gave an almost human shrug. "They know we're here. We certainly told them of our plans at Pwanpwan in enough detail, and being flyers they have a uniform culture so the word would have spread planetwide."

	If what we're doing is that important to them. Hugh kept the thought tactfully to himself.

	"If they meet the thing, we'll see them," the artist went on. "If they don't it will be a good opportunity to check their technology in more detail. They don't always seem willing to share with us."

	Janice frowned; she was never happy when her determined liking for people collided with evidence of their less admirable qualities. Her husband made it unnecessary for her to speak, however.

	"Jan! Your suit's stopped the medication. How does your chest feel?" She sat up slowly, stretched and bent her arms and legs, and took several deep breaths.

	"A little headache, but I guess I'm back in action. Let's go check the antenna again. I suppose Venz has been staying with the signals." She glanced toward the balloon.

	Rekchellet put away his sketching gear and answered as he took to the air. "Of course. Let's see if we can get some sort of distance for that source. It might be near enough now for interferometry ..." He left the thought unfinished and flapped away; the walkers followed toward sled and antenna at their own speed. They were less optimistic about distance measures through variably dirty ice and multiple thermal layers in open ocean, but there was always a chance; and keeping objections or doubts to oneself made for more peaceful team life. The Crotonites regarded themselves with some justice as directors of the group, though the junior members were developing some skill at slipping their own policy notions into cracks between the flyers' divergent aims toward the native population.

	Venzeer was growing enthusiastic as they got near enough to hear his translator. "It's really getting louder and the direction line more horizontal, and over toward the edge, too. I'm for flying over and seeing whatever it is; it's got to be surfacing. How about it, Rek? You'll have to record the thing when it comes up, anyway. The others can monitor signals while they drive. It's only five or six kilometers."

	"All right," the woman said quickly. "We can afford to be out of touch for a while." The group had no radios, of course, because of the natives, and neutrino receivers were too heavy to be carried personally by the flyers.

	The Crotonites winged sunward with no further words. Hugh and Janice checked the balloon moorings once more, boarded the carrier, and energized its fuser.

	They couldn't watch the antenna itself very well from where they sat, since the open platform which carried the flyers' seldom used controls was just above them. The woman, however, monitored its directional readings carefully.

	They had to drive slowly, partly because of a gathering haze and partly to minimize the heavy atmosphere's drag on the huge balloon. With the flyers gone even briefly, more broken mooring lines could compromise the whole project. It was also advisable for safety's sake to avoid any vegetation, since much native Habranhan life used azide ion instead of ATP. Hence, they didn't expect to reach the edge of the giant iceberg until long after the Crotonites. Probably they would have found and disassembled the signaling device long before the Erthumoi could do anything to prevent what even Janice considered an unethical maneuver. Even she was concerned enough to take advantage of the Crotonites' absence and make a quick report by neutrino beam to the Erthuma-crewed research vessel orbiting Habranha. If the flyers did cheat on the natives, at least someone would know.

	However, they got there in time for two reasons. The recent tilt had brought the sea much closer, or perhaps more correctly had brought the explorers closer to the sea. It was now only a little over one kilometer from where they started driving. Also, whatever was emitting the signals had not yet surfaced when they did arrive. Rekchellet was several hundred meters up, apparently sketching the new water line when the human explorers stopped the carrier. The Darkside wind had resumed and cleared the haze by this time, though another snow squall could be seen far to the left of sunward. As the vehicle stopped, the recorder planed to a landing beside them, stowing his equipment.

	"I've got it this time."

	"What do you mean?" asked Janice.

	"When I dropped the pad before, I didn't save quickly enough, and washing around bumped something, so I lost the last record. Most embarrassing. I won't let that happen again."

	Hugh was rather startled; it seemed odd for a Crotonite to confess an error not merely within Erthuma hearing but directly to an Erthuma. It seemed best not to emphasize the matter, however, so he merely asked about the signals. Venzeer, who had resumed station at the antenna the moment it had come in sight, reported, ignoring the fact that Janice had been checking them all along.

	Signal direction was still below horizontal, and now nearly constant; only the increasing strength implied that the source was still in motion. It was almost as though something were traveling along the slope of the ice-ocean interface toward them, rather than merely rising through the water.

	The surf was heavy, a fact neither surprising nor predictable on Habranha, so none of the team could get very close to the edge, and with the motionless sun in front of them this made watching difficult. Grendel, as the Erthuma explorers had named Habranha's red dwarf sun, glared less than twenty degrees above the horizon. By the time the berg joined the ring continent it would appear nearly twice as high, but it had hundreds of kilos yet to drift before this happened. All that could easily be seen offshore was that much vegetation had been torn loose by the tilt and was being washed toward them. Much of this had already burned; some was smoking as it rolled in the surf, and much yet submerged—not all Habranhan plant life floated—was presumably causing the heavy frothing at the surface. Even more, it could be guessed, was waiting for something to help it discharge electrically.

	The explorers watched the dazzling waves roll toward them, crest, and break. That part was familiar enough to all of them, but what followed was subtly different. The surf had no sand to move. The broken waves slid for hundreds of meters along hard, gently rising, smooth ice, losing energy very slowly as the water did its trivial work against Habranha's weak gravity. Nearly free of ripples as this part of the moving fluid was, it was still hard to see whether anything but seaweed was being carried by it. All four beings watched intently, each with some sort of idea what would show up.

	Probably, Hugh thought, it would be a featureless sphere, since the hypothetical instrument must be designed for hundreds of kilos depth. Rekchellet seemed to have dismissed this factor, apparently expecting solid-state apparatus, but the man was less certain.

	All were wrong. Something decidedly not a plant finally showed almost in front of them—no coincidence, since they had moved as close as the antenna could guide them to the path of the signal source—but for more than a minute few details could be made out as succeeding surges carried it closer and closer to shore.

	It was not a sphere, but something very irregular, and all four explorers inched closer with due care to avoid charged plants. The thing finally landed, and for a moment before the next surge arrived it was fully exposed. It was still too distant for clear Erthuma vision, but both the Crotonites gave whistles of surprise.

	Then it was almost covered by water once more and borne closer; and the next exposure left even the Erthumoi in no doubt, especially as the snow squall had moved in front of the sun.

	Many of the details were still obscured, but not by water. Clearly and unarguably it was a native Habranhan wearing some sort of armor and connected by a rope to a sausage-shaped pack. Even the wings were protected but free to spread and move. As the explorers watched, the being wriggled, straightened itself out, and began to crawl away from the next wash of oncoming sea. Hugh and Janice, already less startled by the arrival than amused by the probable Crotonite reaction to flyers underwater, dashed forward to help, and a few moments later the native was safe above the reach of the ocean. The radio speaker emitted a complex sound pattern, and the translator followed with interpreted Crotonite speech in Venzeer's voice.

	"You're—you're welcome. But what's a flyer doing underwater?"

	That was just what Hugh and his wife would have asked if they had been able to speak the native language and think of a wording inoffensive to the Crotonites. They listened eagerly for an answer, but heard only the incomprehensible gabble of Habranhan radio emission turned into sound.

	Maybe the Crotonites would translate, of course. The machines were set to interpret between Falgite, the native speech of the Erthumoi, and the language of whatever Crotonite planet the flyers had come from—neither Hugh nor Janice knew its name. This could, they suddenly realized, be awkward. Crotonites had been on Habranha much longer than any Erthuma group, and many of them could understand and speak with the natives without translation. Only conversion between radio and ordinary sound was needed. There was pretty certainly, Hugh thought ruefully, no translation system yet in existence between Habranhan and any Erthuma language. "Ground crawlers" had just discovered the place; Crotonites had known of it for at least several decades and possibly for several generations—different sources gave different answers to that question.

	He and Janice would have to make what sense they could out of the flyers' side of any conversation with this native, and hope they could stay close enough to get all of that.

	"Gabble." Presumably the native.

	Venzeer's voice replied, "Complex static."

	Hugh kicked himself metaphorically. The machine wouldn't handle whatever speech the Crotonites used talking to the natives, either. Of course. He looked at his wife, his raised eyebrow visible enough through the clear suit fabric. She gave an almost imperceptible shrug. She wouldn't want to be sneaky anyway, he reflected. Ask and ye shall receive.

	"Rek, could you tell us what's going on? Or could your translator cover native-to-you and then you-to-Falgite, so we can follow? I never expected a live native underwater, any more than you did." True enough, and also tactful.

	The Crotonites looked at each other briefly. Both Erthumoi were pretty sure of their thoughts; Hugh was more nearly right, it turned out. He became almost certain when the others hesitated before answering; if such translation had not been practical they would have said so at once. They must be wondering whether letting their surface-bound companions follow all conversation with the native was a good idea or not.

	One of them realized after a moment that the hesitation had betrayed them. It might have been Venzeer; at least, it was he who answered.

	"Y-yes. I think we can do that. We have a local translator cartridge for reference backup, though both of us handle the language pretty well. We can put that into one of our sets, and as long as we're in hearing distance of each other it should work out all right."

	He began manipulating something attached to a harness strap.

	"Why is this fellow all alone so far from the ring and underwater besides? Has one of their mining subs had an accident? I thought they couldn't mine this close to Darkside, anyway." Hugh hit what he considered the key points first.

	"I don't know. We've been assuming that their mining equipment was automatic or remote controlled. The submarines we have seen are open frameworks apparently not designed to resist bottom pressure, but merely to survive it." The man nodded.

	"I haven't seen any myself, but they have practically no metals here and bottom pressure is around ten thousand atmospheres—my units, if the translator doesn't take that for granted. Unmanned machines that didn't need to protect any crew from pressure would seem obvious. This fellow, though, was underwater. I hope he's willing to tell us why."

	"So do I," Venzeer responded promptly. "Let's find out. There seem to be none of his fellows nearby. Maybe ..." He failed to finish the sentence. Rekchellet was already addressing the native again, and this time the Erthumoi could follow the conversation.

	"Did your submarine craft have some sort of accident?" Reasonably straightforward for a Crotonite, Hugh thought. The answer came through rather brokenly; two sequential translations had to involve delays from the differing sentence structures involved. Even one was usually a bit jerky.

	"We had no sub. It was not exactly an accident. Pert and I were riding a deep berg, charting currents, and it moved up to the deep-middle pressure boundary more quickly than we expected. The surface chose to blow off instead of pulverize, and a fragment killed Pert, I'm afraid; I haven't seen or heard her since. What was left of the berg was much less dense. I don't know whether from phase change or lost mud or both. Anyway, it came up quite rapidly, and I rode it. I nearly got crushed when it hit the bottom of this one. It shattered, and there was no single piece big enough to be worth following, so I came up to report."

	"How will you do that? Are some of your people nearby?"

	"Not likely. I'll just shed the armor, eat what I can of the supplies"—the native indicated the streamlined pack he had been towing—"and fly sunward to the ring. It won't matter where I hit it."

	"You'll leave your armor here?" The Crotonite made no pretense of hiding his surprise, or perhaps was hoping the translator would not carry it. Neither Hugh nor Janice could guess whether the feeling, obvious to them, had come through to the native.

	"Sure. I could never fly with it, and it's easy enough to replace. If your work carries you that way, you might carry it farther from the water; it'll be more likely to be available if anyone else should want it."

	"Fair enough." This time Rekchellet's voice showed no obvious emotion. "We can certainly carry it on our supply vehicle."

	"Good. I'll get along; the sooner I can get the current data home, the closer to real time we can figure." The native, showing not the slightest surprise or curiosity about the aliens, stripped off his protective garment. If either of the Erthuma watchers had known that much about their ancestral world, they would have been reminded of a dragonfly emerging from its pupal form, though the Habranhan body was much more flexible and had three pairs of wings rather than two. The head was large enough to make intelligence predictable, though it appeared rather small on the four-meter body. The four other limbs were much thicker for the being's overall size than those of any terrestrial insect. They ended in knoblike wrists which could serve as feet, though they would hardly have a good tread on ice, and from which half a dozen flexible tendrils could be extended for handling. Once out of the armor, the being moved to its pack, opened one end, and extended a proboscis into some invisible container inside. For several minutes it remained motionless, presumably eating or drinking. Then the wings firmed and extended as fluid was pumped into their veins and stiffened them. It turned to face the four aliens, still showing no surprise.

	"There's a good deal of diving juice here, and some food too, which could be useful to someone—not you folks, of course. If you wouldn't mind taking that along, too, and dropping it farther from the sea, it might be handy to someone a long way from home. Thanks." The wings began to beat rather slowly, somewhat out of phase with each other; if they had been connected by membrane, the latter would have rippled like the fins of a mania ray swimming, though the Erthuma watchers were reminded rather of a similar creature native to Falch.

	They considered this aspect for only a moment. The Crotonites rose with the native and accompanied it for several hundred meters on its way. Hugh didn't know whether to worry more about what they might do to him or what they might say to him. Janice refused to worry, and seemed justified; their winged companions presently peeled away and swung back toward the iceberg, leaving the native to dwindle in the distance and quickly disappear in Grendel's glare.

	Hugh was not surprised when the Crotonites settled beside the diving armor the being had left behind. After all, he and his wife were already there themselves; examining a suit which apparently could protect its wearer from thousands of atmospheres pressure seemed very much in order.

	The jointing was ingenious, but the material baffling. There seemed nothing particularly pressure resistant about it. The covering for the wings and other limbs was actually flexible. Close examination of a torn-off piece—torn off easily enough to compound the mystery—showed that body plates as well could easily be bent not only by Erthuma hands but by the less sturdy and efficient graspers of the Crotonites. There seemed no way the suit could defend its wearer from significant fluid pressure; and Habranhan bodies appeared frail even by Crotonite standards—large, of course, but far from rugged.

	Still the fellow had said, quite unambiguously as far as Hugh could remember, that he had been working much farther down than the thirty kilometers or so that marked the bottom of the ice mountain the foursome was riding. He had been talking about ice phase changes which the man was pretty sure implied thousands of atmospheres. How this went with flexible armor material was very unclear.

	"We'll have to take some of this stuff for analysis," Venzeer said firmly. "As far as I can tell, it's about like the polymers they make fences and weather guards out of, but there must be something different about it. Maybe—wait a minute, did any of you see water draining out of it as he took it off?"

	"Yes, now that you mention it," admitted the woman. "Not much, but there was some. I just assumed he'd loosened a joint or a valve for some reason before he got ashore, and some ocean had gotten in.

	"Could you—assume—why he'd do such a thing?"

	"There seemed too many possibilities to make a guess worth while."

	"Such as?"

	"Oh, personal comfort, if he'd been wearing it a long time. The urge to breathe fresh air. Freedom of motion. Thirst—can these people drink their ocean water?"

	"No. They don't mind the ammonia, but there's biological contamination; a lot of the azide ion most of the local life uses for energy storage—like us, though I've heard you use something else—is free in the ocean, I suppose from plankton decay." Venzeer furnished this information, giving his Erthuma listeners further pause for thought. Janice's rapid list of guesses had silenced Rekchellet for the moment, but he had not abandoned the thought underlying the earlier question. He made his way to the spot where the armor had first been shed and examined it and the ground closely, sketching busily from time to time.

	It was the usual ice, rendered milky by ultrafine silt trapped when it had frozen for the last time, possibly airborne dust which had blown to Darkside and mixed with the snow. There was some sign of recent local melting, in the form of a narrow line of the white sediment to seaward in a barely perceptible depression, but this might as well have been due to the native's body heat as to water leaking from the armor. The recorder brought his face to the ice and sniffed, mouth gaping—taste and smell were even less distinct for Crotonites than for Erthumoi. Hugh wondered privately how he would sketch an odor.

	"Hugh—Jan—come here and sniff. I don't know whether your sense of smell is any better than ours, but can you tell whether anything strange is here?"

	The walkers complied, and looked at each other uncertainly. "There's something," the woman admitted, "but I certainly don't recognize it. I've never noticed any particular smell to the Habras, but I'm not sure I've been close enough to one to have caught it if there were."

	"I have been, but they don't smell, as far as we're concerned." Venzeer spoke thoughtfully. "Anyway, there's something here, which probably came from his diving suit. Let's see if it smells."

	All sniffed or gaped at the armor. Janice shrugged. "I get it here, too, but don't see that that's any help. We still don't know if it's something chemical—I suppose that's what you have in mind—or perfectly normal for the occupant."

	Hugh cut in. "How would a chemical help? Make his flesh so hard it could resist ocean pressure? That doesn't make sense to me."

	"Nor to me," admitted the Crotonite. "It's just that the whole situation is strange, and I'd like to get all the strange items in one place if I can."

	"If you had asked me before I went, I could have told you all you wanted to know about the suit with no need to damage it."

	Human and Crotonite beings alike froze briefly at the words. Hugh, the only one standing instead of being bent over the armor, was the first to look up, but the others were almost as quick. There was little doubt about the owner of the voice. Sure enough, a six-winged body was flapping slowly a few meters overhead. With all the usual Erthuma tendency to blame someone else, especially a Crotonite if one were available, for an embarrassing situation, Hugh found himself hastily uttering an excuse for the entire company.

	"We hadn't thought there would be anything to ask. We didn't notice how flexible the material was until we picked it up; then we couldn't understand how it could protect anyone from depth pressure."

	Venzeer cut in with his own thoughts. "How did you know we were damaging it? Why did you come back?"

	"I heard a piece being torn off." The native glided down beside them.

	"But—oh. Of course." Janice cut her objection short. The armor was of polymer and certainly an electrical nonconductor—it would have to be, to protect its wearer from inadvertent contact with plants, even underwater. Tearing one part from another would set up enough potential difference to produce radio emissions, even if their own translators had not picked it up—which they might have done; neither Crotonite, as Rekchellet admitted later, would have noticed random static.

	The native seemed to accept the excuse, but appeared a little surprised at Hugh's words.

	"We don't try to resist the pressure. We—oh. When I mentioned diving fluid, you thought I meant ballast, I suppose."

	"We didn't even get that far," Janice admitted. "I don't think any of us even thought about those words. You even said it would be no use to us, didn't you?" The Habranhan's still inflated wings cocked upward in what even the Erthumoi knew was an affirmative gesture.

	"Oh!" Hugh said softly. "I get it. Ducking PV troubles by holding delta-V down. All liquid. All body cavities free of air bubbles. Something able to carry oxygen fast enough in solution or loose bonding. I've heard of that, though I don't think it's ever been done at home. Very long ago, maybe even back on Earth."

	"I hadn't," his wife said, "but I could see he meant something of the sort."

	"What are you talking about?" cut in Venzeer.

	"Most of the damage done to a living creature by pressure change results from the big volume change of gas. Liquid doesn't change volume very much with DP. If one goes up or down slowly enough to let body fluids—mostly water, for all of us—diffuse even a little through membranes and cell wall, there's no trouble. Even deep-sea creatures don't burst unless they have air bladders or unless they're brought up really fast. The Habranhans must have developed a fluid which they can use to soak their entire bodies, including the cavities normally used for oxygen exchange, and fill the space between body and armor. Then pressure doesn't mean anything."

	"But there are other dangers beside PV," her husband put in. "How about nitrogen narcosis?"

	"I don't know. We must have solved that one, too, if what you remember is right. And maybe these people aren't as subject to that; after all, they can stand some hydrogen cyanide in the air, as the Crotonites do."

	"Of course," Rekchellet muttered softly. "We're not crawlers, either." Janice ignored the interjection.

	"Cyanide ion, carbon monoxide, and molecular nitrogen have identical electronic structures. They only differ in polarity and net change. Anyone able to handle cyanide should have no trouble with nitrogen."

	"You're speculating," her husband pointed out.

	"Of course I am. There hasn't been time for a library check, but I'm going to get on the transmitter pronto. We've only just heard about all this from—what should we call you?" Janice tried to make it obvious from her attitude that she was addressing the native. Apparently he understood.

	"I am—" the rest was unreproducible static.

	"I'm sorry," Janice said as tactfully as she could. "That symbol does not convert to sound patterns we can make. Will a simple pattern such as William be unambiguous?"

	"It sounds like 'backward flyer,' but I can make allowances. I understand the difficulty. If William is convenient, I am William."

	"Bill would be even easier and quicker."

	"That has no meaning, but I can remember and produce it."

	"Thank you, Bill. Do you know why we are here—the four of us?"

	"I assumed you were making current studies and possibly other analyses of our ocean and atmosphere, just as we do. I had supposed formerly that there were probably others of your people making similar studies below the surface. I gather now that you have not started that yet."

	"We walking people haven't, and I doubt that the Crotonites have either. We would normally do such work with the aid of machines we call robots, and these would have to be very specialized. We have none so far on this planet. Venz? Rek? How about your people?"

	"We do not use such machines. We prefer to do our own work." Enough of Rekchellet's tone came through the translator to remind Hugh and his wife of the distrust of artificial intelligence shared by most of the non-human starfarers. The woman pressed the point, however; it was poor tact, but she wanted Bill to learn something about the Crotonites which they themselves were unlikely to have told to the natives.

	"But you haven't done any underwater exploring here, have you?"

	"Not here, nor anywhere else. We fly."

	"Of course. And one cannot fly underwater."

	Bill cut in at this point. "But one can. We do. It is how one gets around, outside the submarines. It is how I escaped being crushed by the rising ice mountain I was on, when it collided with yours."

	Venzeer cut in sharply. "You fly underwater?"

	"We call it swimming," Hugh said hastily. "I suppose Bill's people would use their wings, though." He regretted the second sentence even before he had finished, and silently cursed his inbuilt honesty. The Crotonites made no immediate answer, but looked thoughtfully at each other. There were several seconds of silence in which the thoughts of each of the five would have been of great interest to all the others.

	Venzeer's imagination was playing with the Habranhan's revelation: You could fly down there. Maybe it wasn't so bad, after all; maybe one could go down, share experience, even a new kind of flight, and get to know the natives better—realize why they seemed so indifferent to the opportunity of leaving their world and flying among the stars. Their ancestors must have done it; these people had not evolved on Habranha. Not only was there no linkage—the ring continent had no land animal life, let alone flying creatures—but these flyers didn't even use azide in their biochemistry, even though they were as electrical in many ways as the plants and the sea creatures. Neither did the plants they grew for food. They must be colonists. Maybe even—no, that would be too much to expect.

	The thought of flying in the deeps, though. That could be a real experience—but it would be so dark. No way to see any distance; just muddy, unlit water all around. It would be flying, of course. The native had said so. But there would be no clouds, no stars, nothing but hearing and touching to keep one in contact with the universe. The natives were flyers and knew what seeing meant better than any ground crawler, but they wouldn't miss it quite so much if it were gone. They had that Habranhan advantage—they could detect electric fields and impulses as well as see and hear ...

	And they could fly underwater, under hopelessly crushing pressures. Learning how they did it—finding the formula of their diving liquid—would be no help to Crotonites. Probably the simple creatures would supply it for the asking. No, they weren't that simple, they were flyers—though since the information would be no real use to the Crotonites, why should they worry about handing it out freely? But—just how different were Crotonite and Habranhan biochemistries, anyway? And if the liquid didn't work, couldn't one find materials which would really keep the pressure out? What were engineering researchers for? The idea of armor went naturally with ground crawlers, of course; no flyer would consider playing with that much weight just for protection. But the weight would mean little or nothing underwater; that was elementary physics. Much library inquiry was in order. There must be plenty of relevant information.

	Rekchellet dreamt along a different line. These things have a field we don't. They have a bigger world of their own to explore than anyone else has ever had. Not just surface and atmosphere, but a sixth of the radius below the surface. A third of the planet's volume in which things live and where things happen. Why should they care about space? Whether they're philosophers hunting knowledge for its own sake or pragmatists trying to keep alive, they have a universe of material for thought and work from now on. A few suggestions for new fields of activity at home, and we won't have to worry about them anywhere else in the galaxy for centuries. Even if they're the Seventh Race and used to travel the stars, they've changed. Of course, we'll have to know enough about their world—their universe—to command their respect. We'll have to be interested in their problems, not get them interested in ours.

	But how do we get down there? The native flyers aren't built the way we are, even chemically. Azide is poisonous to them. How could we develop anything like their diving liquid in a lifetime, or several? Not even the artificial brains the Erthumoi used could—

	He firmly stopped that line of thought. Still, flying in the deeps should be fun. New things to see and to draw. No doubt the Erthuma artificial eyes could be attached to some machine to look things over down there, but how could one abstract the essentials after a picture had been made? There would be far too much irrelevant material in the image.

	Janice didn't really worry about Crotonite attitudes; she took them for granted, often wrongly, but this was seldom brought home to her. Bill, however, was interesting. He was brave; regardless of the perfection of Habranhan diving technology, he had been risking his life. It might have been simple curiosity, or it might have been a sense of duty. That didn't matter. She could empathize with either. She could feel a call from Habranha's deep oceans, an utterly new environment. There would be strange life, currents even more complex than those in the air, and storms driven by icebergs calving upward and by heat absorbed or emitted as ice changed phase with depth and giant bergs either shattered to powder or changed density more sedately and rose or sank accordingly ... Bill's brief account had been enough to trigger the imagination of any chemist. There would be clouds and rains, both upward and downward, of silt scraped from Habranha's core by the Darkside glacier in its eternal grind sunward along the ocean bottom, silt incorporated in the ice and shed at different depths and different rates as the bergs melted, crumbled, or burst. There would be hot currents going downward because they were silt laden, cold ones rising because of their ammonia content, storms where they met and formed gels out of colloids. William had been down there and seen it all, and Hugh would want to hear her guesses and check them out ...

	There must be, in some library file, data on the diving liquid. Riding a merely floating iceberg and keeping track of even chaotic winds and snow squalls was suddenly boring. She was going to get the neutrino beam busy, and she didn't care how many planetary libraries would have to be probed. It wouldn't be hard to get Venzeer and Rekchellet interested in this new search.

	Hugh shared much of his wife's feelings, but didn't take the Crotonites for granted. Maybe Bill's words would persuade Venz or Rek or both actually to try something in the deep sea, something only remotely like flying, though it was hard to guess what the artist—Hugh wasn't sure he was really more than an illustrator and recorder—would find to employ his talents. That might be good; it could make the fellow realize that what you could see wasn't everything and that people who couldn't fly and comprehend the whole landscape at once weren't necessarily beneath notice. Whether the Habranhans took to space travel or not wasn't really important, though the man rather hoped they would; he had no intention of taking sides with either of the Crotonites and didn't much care whether the Seventh Race turned out to be Habranhans or never turned up at all. They were probably extinct, anyway. The natives could take care of their own futures, in space or ocean. It would be fun, though, to have both Venzeer and Rekchellet a couple of hundred kilos deep and learning to fly in water—never mind what verb the translator used. And one could get them arguing later with the single Cephallonian at Pwanpwan about the joys of swimming, and hearing them sneer at the inability of the water breather to "swim" in air. It would be a relief to give them someone, or something, besides "ground crawlers" to belittle.

	And it would be fun to see what the depths of Habranha were like. Jan would already have some guesses, he knew; that was one of the things so wonderful about her. Comparing prediction with fact was always fun. Of course, the process might kill you, but that made it more interesting. There must be information on that old diving juice somewhere. A few minutes, or hours at most, in touch with practically any Erthuma world's data bank should take care of that problem. That would be a highly worthwhile use of communicator and search program time. And it wouldn't take very long to apply the knowledge in any workshop. You might even do it with the sled's equipment—no, one would have to get back to Pwanpwan or up to the station. But one could do it. And maybe the atmospheric chaos on what should be a quiet, tide-locked planet did have its origin in the oceans.

	Bill, least cynical of the five except for Janice, was reviewing his initial surprise that the star travelers hadn't been into the deeps. He had taken for granted that his own planet, however unique and complex in detail, must be just another world to them, and that they had to have routines for studying planets. The thought that his home was unusual enough to make the routines inadequate was somehow pleasurable. There were things he and his colleagues could teach these strange, highly knowledgeable beings after all, in spite of the impression of their own superiority the winged aliens seemed so willing to share. He knew little about the wingless ones who had appeared more recently, but they too were star travelers, and no doubt felt superior because of that.

	Bill was one of the few of his species who knew about stars other than Grendel's companion sun Fafhir by more than hearsay. Most people stayed on, over, or under the ring-shaped continent on the daylight side of Habranha, which was continually adding to itself at about fifty degrees from the sun and melting away at about twenty, and this was in constant daylight. Fafnir was of course visible; its motions had provided the first observable no-fricton system, and had led to the development of physics, according to history. Other stars had been discovered only when researchers had learned how to travel briefly in the dark hemisphere; the nature of stars, until the arrival of the Crotonites, had been entirely speculative, and many Habranhans felt some doubt even now about their existence.

	A few scientists had been tempted by the thought of traveling beyond the atmosphere, but those who had tried it had returned very quickly and unhappily. One could see well enough out there; it was fascinating to have theories about the shape of the world and the continent so easily supported. One could not, however, feel anything. Whether this was because there was nothing near enough to feel or because the strange material of the flying craft blocked electric fields so effectively could not be said; either way, the experience was highly claustrophobic. It was known that the aliens lacked electrical senses—they even had to transform normal speech into something else; maybe this was why they weren't bothered by space travel. No one had been able to find out from the Crotonites; Bill wasn't sure whether other alien species had been asked. There was a new one who actually flew only in water, he had heard ...

	It would be interesting to accompany an alien group into the deeps, if they could be persuaded to go—and if they had the technology to go; presumably deep-juice wouldn't be any use to aliens—but maybe the stuff they made their ships out of could actually resist deep pressure ...

	He'd have to get back to the ring and ask some questions. It was unlikely, statistically, that there were enough aliens here to provide answers. No one knew everything.

	The thoughts, even though shared with reluctance, could lead to only one course of action.

II. Below

	He'd been right, Venzeer thought. It was dark, and the lack of stars was frightening. The lack of orientation was worse. Normally one could fly in clouds with due attention, but that was when the clouds were suspended in air and one's weight and sense of speed meant something. Here, the effect of wing beats was different, and one couldn't beat them very fast anyway, and one couldn't sense speed through armor even if the impact sense had meant anything in water.

	He couldn't blame Rekchellet for spending most of his time in the living sphere of the Compromise. If he himself had had such a good excuse as the failure of the drawing pad to work underwater, he'd have used it. The fact there was little to draw was secondary; Rek was still busy making what records he could, though these were mostly words and figures from the instruments.

	From where he was, Venzeer could see the new supply carrier of course; even the thought of going out of sight of it aroused—not panic, of course. Just plain, rational fear. There was no obvious way of finding it again in the starless dark. No way of finding any direction—not even up or down—with any confidence.

	He could not quite see why the Erthumoi had wanted to name the vessel, since they had not bothered to name the sled, but he could agree with the name itself. It was a modified Habranhan mining sub, open to ocean pressure. Its hull was merely a polymer framework—metal was a laboratory curiosity to the Habras—to hold the mud tanks and engines. The natives had an interesting form of fusion-electric drive, the power conductors being extremely well shielded so as not to dazzle the crew's other senses. The shielding was a conducting polymer, the natural electrical senses of the natives had led to a bypassing of one problem a growing civilization might have faced on a continent of ice.

	The ship's frame members were tubular, filled with heat-exchange fluid which could be pumped where needed. The ice in Habranha's ocean depths had a sometimes inconveniently high melting point and could be found at surprising distances from Darkside.

	Bill, Hugh, and Janice had been willing to spend a month or more in diving fluid and full-recycling armor, but the Crotonites had had to improvise brute-force protection and couldn't stay in their suits continually. Hence the vessel now had two linked transparent pressure spheres near the center, replacing a pair of the original cargo tanks. One globe served as an air lock, the other as living space—very cramped living space, even at eight meters inside diameter, for anyone with wings. Even Rekchellet came out to fly around, without his pad, fairly often.

	When the craft was traveling faster than any of them could fly, which was most of the time, people stayed inside the openwork hull and held on. If they had to rest, they used a cargo tank. Venzeer and Hugh had suggested, during the mission planning, that some of these receptacles should be ballasted with mud to conserve power which would otherwise be needed to force the buoyant living space downward, but the natives had declined. Irrigation mud, which made their continental ice fertile enough to grow food, was too valuable. When the Crotonite research center at Pwanpwan provided a few hundred tons of copper, the Habras had offered to trade mud for the metal, but Venzeer had declined. The metal slugs were easier to handle. He kept the peace by suggesting that the copper might be donated to a Habranhan laboratory after the trip.

	This, of course, would be lengthy. Like the vehicle, the mission was a compromise between the needs and interests of the natives who had furnished the submarine and the alien researchers. The latter wanted not only to learn things about the planet but also in some cases to apply persuasion to its natives. Since not all the offworlders wanted to sell the same things, and none of them dared to say this openly, the final compromise was complex in detail and fully understood by few if any of the beings involved. It had, however, already brought the Compromise closer to the Solid Ocean of Darkside than the Habras had so far explored.

	This was not because they hadn't tried, Bill maintained, but because neither submarine nor free swimmer had ever, so far, returned from the region. There was no obvious reason for this; if anything, the undersea weather should be least violent there, since the descending vertical glacier was presumably quite pure water with no sediment and solute complications. He had told stories which confirmed Janice's picture of silt and "snow," violent currents in all directions, large icebergs and small, monsters and minibeasts. They had encountered some of these since leaving the ring continent, but this had all been out in the warmer ocean. Venzeer doubted much of the rest since Bill had not seemed the least worried about going along himself. The Crotonite had quickly come to suspect that the native was trying to frighten aliens away from exploring in and under the sea, where by his standards the world's wealth lay. This attitude was quite familiar to most Crotonites and not wholly unknown to the Erthumoi.

	Bill was visible now, swimming calmly a few meters away. The lights from the Compromise showed him in silhouette, his wings moving languidly as he followed a tortuous path around the slowly moving vessel. He claimed to be making observations when he did this, testing with his own strange senses the temperature, density, and solutes of the ambient ocean, measurements which would all be compromised if made too close to the ship and its drivers. He certainly made records of some sort after each sortie, but not even the Crotonites could read these, and Venzeer retained his doubts.

	Janice didn't, of course. She had before starting calmly asked William to tell her everything he observed from the beginning of the trip on, and he appeared to be cooperating. She had accepted the fact that the mission was dangerous, and was seriously trying to decide what the danger might be. She was willing to take chances, especially since Hugh was along, but had no wish to be taken by surprise. She wanted to know the local rules as well and as quickly as possible.

	While the information on the diving fluid was being sought, and later while the material was being manufactured, she had spent much communicator time getting library material on high-pressure phenomena, and memorizing a great deal of it. Of the five beings traveling in the middle of a bubble of light with, as far as they knew, over a hundred kilometers of crushing ocean in every direction, she was by far the most tense.

	Hugh had enough sense to be afraid, but was nowhere near panic. The diving fluid, it had turned out, had been known and used for years, though not on his own world, in pressures approaching those of their present surroundings. There had been no trouble finding out about its nature, methods of manufacture, or the practical problems of its use-—which included finding or inventing, and learning to use, some form of nonverbal communication code.

	No one, apparently, had ever had occasion to use it under Habranhan bottom conditions nearly four hundred kilometers farther down, but for the moment there was no plan to go to such depths.

	Rekchellet was the unhappiest. There was nothing to see except the craft he was riding and his fellow explorers. He had drawn all of these in as wide a range of situations as the surroundings afforded. He had records of ammonia content and temperature and suspended matter and even some information on currents, though these were as hard to check as gravity in free-fall. One did not draw this sort of thing, however; one wrote it.

	Worse, there was no way to get their exact position, so even a map was out of the question. The natives lacked inertial trackers, and there had been none available at Pwanpwan—not because none existed, but the Crotonites and others studying the motions of the ice which made up Habranha's ring-shaped continent had firmly refused to loan any to a high-risk expedition. Rekchellet knew he should have done the arguing instead of letting Janice try, but he was coming to regard her more and more as a being, not just a ground crawler.

	He had records, but all in numbers. He had tried graphing the information, thus turning it into pictures of a sort, but was disappointed by the results. Compromise was at the depth where water had its lowest freezing temperature, about twenty kelvins below what everyone in the group considered normal, so his graph suggested that they were moving into a cavern with ordinary ice above and a high-pressure form below. This wasn't really a map, though. It didn't mean they were actually in a cavern, still less that they were about to be crushed by falling or rising ice. For one thing, the ice above would float and that below would sink. The natives knew something about high-pressure ice phases. Even the Erthumoi, at least the female one, did. The glacier on the ocean bottom, crawling its way back toward Sunside after centuries of travel from the Darkside snow sheet down hundreds of kilometers of Solid Ocean column, was what Janice called ice five, and they were currently at the pressure boundary between ice one and ice three, a hundred and fifteen kilometers or so below atmosphere.

	The trouble was, one didn't know exactly. Pressure gages did not have four-digit accuracy in this range. Bill's senses didn't reach. Sonic measures were wholly unreliable because of the vast reflecting, scattering, and absorbing layers of silt and plankton and the labyrinth of thermal currents. The globe of light which let Rekchellet see a few score meters around the Compromise was a prison, and the transparent living shell where he spent most of his time was a closer one. Flying was necessary now and then, but wasn't much of a relief. It wasn't really flying—not when Erthumoi could do it even with their ridiculous limbs. The artificial flippers of negligible area they wore on their walking appendages didn't count. Rekchellet felt annoyed and frustrated.

	William was happy. He was doing something new and useful in a field he had enjoyed all his life. Like Hugh, he was intelligent enough to be afraid, but like the man he was able to face the danger philosophically. He was the calmest of the group, predictably; the situation was more familiar to him than to any of the others.

	He was therefore less alert than Janice. The only reason he perceived the menace first was because it affected something familiar to him.

	He noticed suddenly that it was harder to move his wings.

	At almost the same instant, he became aware of charge building up at the joints of his armor, except the wing hinges where there was constant motion. He was an experienced diver, and almost reflexively moved his handling limbs and bent his body to test the other joints. The growing charge disappeared at each one as it bent; he could sense the current which flowed briefly as charge neutralized. He also detected a faint grating sensation, as though some fine powder were in the joints. He wasted no more time but flapped hastily toward the Compromise, calling a warning.

	"Venzeer! Hugh! Janice! Come in quickly!"

	The Erthuma couple obeyed without question. Venzeer turned toward the craft, saw nothing wrong, and called, "What's the trouble? What have you spotted?"

	"Ice, I think. Do your wings move freely?"

	"They never have, down here. I don't feel anything worse than usual."

	"Come in anyway while we check. Rek, read the thermometer."

	The artist glanced at the instrument console and called out a figure which the Erthuma listeners heard as "two-forty-nine."

	Janice compared this with the phase figures she had memorized, and thought, That's two kelvins below pure water's freezing at this pressure. The water's a long way from pure, though; there should be a good deal of ammonia and lots of other solutes. There shouldn't be ice yet. She could not talk, of course, with diving fluid in her vocal cords, but keyed a terse "Why?" on her code transmitter.

	"Everyone get inside first, and we'll talk theory later," snapped the native. "If snowballs grow, we want to all be in the same one."

	"There is something fogging the hull," reported Rekchellet. "I can't see any of you clearly now. Venz, I can't see you at all. Where are you?"

	"Level, about sixty meters, almost straight behind. I'm coming in—but it is getting harder to move my wings. Better slow the ship or stop it till I get there."

	"All right. Hugh? William? Janice? Are you making it in all right?"

	"I'm here and inside, clamped on," came the native's voice.

	"Ten meters," keyed Hugh. "No trouble. Swimming easy."

	"Any seeing trouble?" asked Rekchellet.

	"Just bad light."

	"There's frost growing on the finer hull members," Bill announced. "I can't make out the type; the crystals are growing fast and aren't large enough to identify. All of you look around for parts of the ship which would be slow to cool; larger structural members, engine casings, and so on. If any of you can tell whether we're getting hexagonal frost or some other kind, let me know at once!"

	"Why?" tapped Hugh. "Why not find warmer water? Near glacier anyway?"

	"It matters—" The Habranhan's voice was interrupted.

	"I'm still ten meters away and can hardly move my wings at all," Venzeer cut in. "I seem to be heavier, too. It's all I can do to keep level with the ship. There's white stuff all over my wings, getting thicker as I watch."

	"Never mind the crystals report," the native responded instantly. "It's middle ice. We'll have to go up to get rid of it, but not too far or we'll have low ice instead. It's growing on the ship, too. Rekchellet, steer back so we can pick up Venzeer and get him aboard before he sinks out of reach. I'm not near the main controls. If we have to follow him down the ice will get thicker and heavier as the pressure rises, and we may not be able to get out ourselves."

	"But I can't see out, now. How do I pick him up?"

	"No ice on us. We'll help." It was Hugh's coder again. "What goes on? You sound informed, but never warned us."

	"First things first. Rek, shift to slow ahead, and turn—left is better. Good. Nose up a little; you're starting a dive—not very steeply, but any is too much unless we really have to go down after Venz. That's good. Hugh, I can't sense very far now either; frost is forming on the lights, and charge on the body is confusing. Are you near him yet?"

	"Here, holding wing—"

	"I have the other," Janice cut in. "Keep turning. There. Straight. Straight. A little right. Straight. Tiny down. We're sinking. Almost—farther—there. I have hold of frame. Wings frozen open, further aft to get inside. Wait. Now. Safe."

	"You're inside? All right. Rekchellet, work us upward, very slowly. With luck, which means if we aren't too close to Solid Ocean, that will get rid of the frost. Just start the maneuver; I'll be forward in a moment and will take over control."

	"Why up? What happened? Explain!" Hugh sounded emphatic even by code. Bill answered with apparent calm.

	"I'm not sure I'm right. I said we'd need luck. There are several kinds of ice. I have control now, Rek. What we find on and near the surface is less dense than liquid water, so it floats. That's ordinary land. I should say it floats if it doesn't have too much mud in it, and it's land if it has enough. At middle depths we find another kind, and very far down a third. The last kind is very hard to melt at the greatest depths, and both are denser than liquid water.

	"We are near the depth boundary between the first two kinds, and I needed to know which was forming so I could tell whether we needed to go up or down. If it had been high ice and we had gone up, the decreasing pressure would have raised its melting point and we would have accumulated more and more, and finally reached the surface, or more likely hit the bottom of the surface pack, in the middle of a fair-sized iceberg with no way to get out, since we wouldn't have been able to move. Us, not just the ship. If it had been middle ice, and we had gone down, the increase of pressure would have raised its melting point and again we would have formed the center of a large berg, this time on the bottom or on the deep ice shelf, if it exits. It ought to, since ice gets 'way out toward the ring on the bottom. Before we got there, the change of the stuff around us to deep ice would have torn ship and us apart as the volume changed in different places at different times.

	"When Venzeer said he was being dragged down, I judged it was middle ice, so I am sending us up. The decreasing pressure should lower the melting point and free us fairly soon."

	"Unless we overshoot," Hugh suggested. "Phase boundary. Right?"

	"Quite right," Bill replied calmly. "I thought it was Janice who had all that information."

	"She has the numbers. I'm like Rek—just pictures."

	Janice's code tone came in. "Ice seems to be going."

	Venzeer confirmed this with glee. "I can see my wing tips again."

	"Can you move wings?" Hugh asked, practically.

	"Not yet. Better keep hold of me." The Crotonite had a grip of sorts on a part of the ship with his handling nippers, which had not been as solidly immobilized as the great wings, but his rescuers had been carefully supporting him against the currents which rippled through the openwork hull of the Compromise.

	"Don't worry," Janice assured him. "You're thawing. Why no ice on Hugh and me?"

	"Your armor's at higher temperature," Bill pointed out. "I don't suppose you generate as much body heat as we flyers, but with no wings you have a lot less surface area for dumping it."

	Of course. Simple physics, thought Hugh to himself. Much simpler than the phase behavior of water. Aloud he coded, "Jan, how about solvents? Ammonia practically everywhere—"

	"Not here," Bill interrupted. "I've never known such pure water outside a lab. There's some life, but even the microbes must be hungry. What do we do now? I've backtracked our course for a kilometer or so, and it's a little warmer, so we should be rid of the ice pretty soon—I should think you could see out now, Rek."

	"There's nothing to see but the rest of the ship, but you seem to be right. I never got a sight of Venz with his wings frozen. How do we get a record?"

	"You could come out and take a look before he loosens up, if you think it's that important. The Erthumoi were never bothered, so it's safe enough."

	"I saw. I'll make a sketch for you later," tapped Janice.

	Bill remained concerned with their main task. "If we can't get any farther and still make measurements, what becomes of the mission?"

	"Plenty of power," Hugh pointed out. "Warm ship?"

	"My first thought is that it would invalidate any measurements we made," the Habra responded slowly.

	"Not much more than our mere presence does. Our bodies were losing heat to the ocean, too," Venzeer pointed out. "Mine, especially. We need use only just enough heat to keep the frost off."

	"But that will leave a trail of warmed water behind us as we go along. It takes very little temperature change to start convective instability. That's why computing weather even in air is so hard."

	"In air," Hugh emphasized. "PV small in liquid. Expansion a lot less. Density change—"

	"You may be right, but we get more violent storms in the deeps than in atmosphere," Bill pointed out. "And this might be just the thing to start them. I'm willing to try it if the rest of you are, though. Just be sure we keep track of how much energy goes into the heaters. Computing a storm pattern is hard enough even with all the data."

	"Computation impossible," Janice keyed. "Situation chaotic."

	"Nothing's basically impossible," replied the native, "but I grant it's far beyond our present abilities."

	"Impossible," the woman repeated. "Meteorology should have given you folks chaos theory. Maybe bowling alleys needed too. But let's go. Solid Ocean should be near."

	"Why?" asked Rekchellet. "We don't have any surface data. The upper glacier extends a lot farther into Sunside than the Solid Ocean—after all, the latter's just a theory we're testing—but no one knows how much, and even if we did we don't know how far we've come under the upper ice pack. I know there's a sonic reflection from what seems to be a more or less vertical surface somewhere ahead, but I wouldn't guarantee whether it's one kilo or fifty, or even that it's solid. What's the basis of your guess?"

	"Water purity. Bill said it. Should be fresh melt."

	"That sounds reasonable," the native agreed. "We winged folk had better stay near or in the ship. You others don't ice up so easily and can fly ahead, making measurements as you go. Don't get very far, though. Instabilities may always be possible to calculate, whatever your chaos theory says, but I certainly can't always do them in my head, and I'm not at all sure I'll be able to sense them. I got caught only a few minutes ago, remember."

	"But you weren't thinking about that!" objected Rekchellet.

	"I should have been. The point is that this is research, and if we knew what was likely to happen there'd be no point in being here at all. Be very careful, wingless people. I know you can fly here but can't believe those limbs are really efficient. I would advise using safety lines; we have them aboard, you know."

	"How long?" asked Hugh.

	"About two hundred meters. You wouldn't want to get even that far, since the ship's light won't suffice for clear sight at such a distance and that's your only useful sense."

	"We have lights," Hugh pointed out.

	"By all means. Use them. But I'd still use the lines and let them dictate how far you got. Here—make fast."

	Man and wife obeyed, since they were sensible beings. The Compromise resumed her cruise away from Under the Sun at very low speed, the Erthumoi swimming ahead. Bill was still in the control cage guiding the vessel. Rekchellet carefully saved each sketch he made of the team members blurring out of sight ahead and slightly to each side—if they had gone straight ahead, the mud tanks forward of the living sphere and controls would have hidden them from everyone's sight, though perhaps not from the Habra's electrical senses. All the Crotonite could see were portions of the two safety lines, which had been made fast not to the bow but to frame members close to the pressure spheres.

	The advance party stayed in code touch as well; sound, even the code, carried well through the water, and all the suits except Bill's had impedance-matching coatings to handle the interface problem. The native had his own sound-to-radio transformer, and had learned the code during the weeks the Compromise was being rebuilt. For some time, the only words from the advance scouts were the routine "nothing new." Bill stated with equal regularity that the water was still very pure.

	Then Janice's code came back off schedule. "Turbulence! Watch it, Hugh and Bill. Almost snapped my line."

	"Nothing here," came her husband's response. "You did—no. Just local I—" His code ceased.

	"Why local?" came Janice.

	"Don't know. Maybe—" The Crotonites were irritated by the confused symbols, though they realized the cause. Bill forestalled any complaints they might have uttered.

	"Not time to theorize yet!" called the native. "Come back toward the ship. Stay only ten meters or so ahead, so you can give me warning but will be able to come in quickly and hold on if something bigger hits."

	"Can't you sense them?" asked Hugh. "No. The water's too clean and featureless—I could spot something distorting the heat ripples of your suits when the eddies hit you, but no sooner. Stay close. I'm feeling turbulence with the ship, now."

	"Me, too," asserted Rekchellet. "It's good. I haven't flown a cumulus cloud in months."

	"It won't be good if it puts too much bending stress on the ship," the native replied grimly. "I'm feeling it more now. You Erthumoi get aboard fast. I've been in lots worse storms than this seems to be so far, but not with crew outside—and then I could usually tell what was coming." Janice and Hugh obeyed without question. The Habra went on, "I assume we still go ahead. Rek, get everything you can tell from your instruments on record. Never mind drawing, you can write. Just keep notes, and save them. We're—"

	"Jan! Slack!" the man's code interrupted the pilot's orders. "Bill! Sharp right!"

	Hugh and his wife had obeyed the original command to pull back toward the Compromise, and had been some twenty meters ahead. The woman was about as far to the left of the vessel's bow; Hugh on the other side. Something had suddenly become visible: a white, very thin and twisting tornadolike funnel reaching from the darkness ahead. Before this actually got to them, something snatched Janice forward, to the right, and somewhat downward. Hugh reached for her, but she passed a dozen meters beyond his grasp. Both had coiled their lines as they came in, but the woman had been slower, and had been startled by the sudden jerk of the current. Some loops of her coil escaped her grasp.

	As her husband entered the eddy and was swept after her, he felt his own lifeline tighten, and let it slide gently through one gloved hand to avoid too sharp a jerk when the slack was used up. His swim fins sent him forward two meters—four—six, with his own line uncoiling again behind him; then he could reach hers. He seized it and began swinging his arm to wind the cord around it as many times as possible. She was still looping it up at the outer end.

	The real jerk came first on the section between them, but both reacted properly, letting the arms which held the rope extend slowly to ease the shock. For the moment everything seemed safe; they were fast to each other, and both were attached to the Compromise.

	They began drawing together, hand over hand, along Janice's lifeline. This prevented Hugh from paying proper attention to his own, and before they reached each other the latter tightened abruptly. He instantly eased his grip on it, but in the momentary inattention it had wound about his left ankle. The polymer ridge around the joint—none of the armor was of metal, because of the Habranhan sensory problems—was not really sharp, but quite sharp enough. Now only Janice's rope connected them to the ship.

	She made contact with him seconds later, and played their remaining line as carefully as possible. Her husband concentrated on keeping hold of her armor and not interfering with her work. He would have liked to tie them together with his own length of rope but was unwilling to let go of her even with one hand. The eddy calmed briefly, and she hauled them closer to the sub. Bill could sense their location vaguely and helped, swinging the Compromise's bow to the right and downward. They were almost in reach of a firm hold when another swirl hit the ship itself.

	The bow lurched away again. Janice reacted quickly enough to save the line, and began hauling in once more. Then she realized that Hugh had lost his grip—actually, he had let go to grasp the hull himself—so she released her own coils of rope, and began kicking herself frantically toward him. Turbulence sent him out of reach time and again, sometimes one way, sometimes another; up, down, left, right, and all imaginable combinations. He too was swimming with all his strength, but the eddies seemed deliberately trying to keep them apart.

	Bill was working, too, with all his piloting skill, to keep the Compromise near and bring it nearer. He uttered a burst of incomprehensible radio sounds at one point when chance brought the hull actually within reach of Hugh and the Habra thought the danger was over, only to see the man ignore the opportunity and continue trying to reach his wife. Intelligible words followed via Crotonite translator.

	"You idiot! She's still tied to the hull! She doesn't need rescuing!"

	But Hugh wasn't completely out of his mind. A few seconds later he managed to grasp Janice's safety line, and instead of hauling himself toward her, went hand over hand along it to the hull. Here he slipped inside between a couple of the stringers, hooked both legs around other sections of tubing, and only then began carefully taking up the line's slack. This accomplished, he began playing her in carefully, never letting the cord suffer any sharp jerk. Bill helped by maneuvering the Compromise toward her until she was only a few meters away. Then, afraid of overrunning and colliding too hard, he neutralized his controls. The Erthuma couple drew toward each other along the last meters of line until hand-to-hand contact was possible. A moment later both were safely aboard, or as safely as the open hull structure permitted. Hugh didn't really relax until both were inside the mud tank they considered their own.

	William's voice remained calm. "Go ahead, I take it?"

	"Certainly, but no scouts," Janice tapped. Her husband wondered whether he should add any remarks about speed, but decided to leave that to the Habra's judgment. The Compromise got under way, trembling and shivering as she plowed into one region of turbulence after another. It might be a mild storm by the native's standards, but Janice was wondering what motion sickness could do to a Erthuma body soaked in diving fluid. She and her husband, helmets just above their tank rim, looked ahead as well as they could. There was little to see but occasional swirls of white dust as ice formed briefly in higher or lower pressure parts of the eddies. Sometimes the whiteness vanished as quickly as it formed; sometimes growing clouds of whiteness drifted upward or downward depending on the density of the ice which had formed. Janice wondered if their native friend really thought this sort of thing could ever be calculated. She also wondered when they would reach the Solid Ocean—and how hard.

	It was Rekchellet, looking out hopefully, who saw the bottom first an hour or more later, and might have sketched it before calling a warning if it had not been so featureless.

	"Slow your descent, William," he called. "The keel will touch in a few seconds."

	"We're flying level, as far as I can tell," returned the Habra. "I don't see—oh. You're right. I didn't sense it. Too much static in the turbulence. We're not going fast enough to hurt anything if—"

	Technically the native was right; the average speed of the Compromise was not great, though much greater than when Hugh and Janice had been swimming ahead. The turbulence, however, had fore-and-aft as well as vertical and lateral components, and as William spoke, the ship received a strong forward boost. The impact with the up-slanting bottom was not great enough to provide much of a jolt, especially as the bottom proved to be loose and powdery; the damage was indirect.

	A vast cloud of white material billowed up around them, cutting off all sight and blocking even Bill's senses with random static charges. Rekchellet, the only one not in near-zero buoyancy, felt his surroundings tilt as the Compromise came to a halt and then began gently rolling downhill toward what had been the left of their heading. Only the small size—eight meters internal diameter—of the pressure sphere allowed him to reach his controls as the ship went over on its back. The first roll dumped Hugh and Janice out of their tank, the second jarred Venzeer from his hold. He got another brief grip at an outer stringer, but let go as he realized he might be caught under the hull as it continued its slow and majestic downhill rolling. More white stuff swirled up as the frame members dug into the sloping bottom. The Crotonite, picking a moment when his flying senses told him that upward motion was changing to downward so he was presumably on top, slipped outside and flapped gently a few meters upward to get clear. The cloud around him darkened as the ship and its lights rolled away.

	He started to follow the slowly fading luminosity. Then it occurred to him that going to one side might get him out of the stirred-up material and let him see better. This worked, after a fashion; he found himself able to see the cloud itself, and the brighter comet head that was presumably the Compromise, now well down the slope. Backtracking uphill by eye, he saw the hollow which might have been the point of impact. Near this he perceived two much smaller blurs of light, apparently revealed by currents which had swept the silt aside. He was an experienced explorer; he checked in before doing anything.

	"Rek? Bill? Hugh? Jan? I'm outside. I see what I'd guess is the ship if it's still rolling downhill, and two other lights. Am I right about the ship, and should I get back to it now or investigate the other lights?"

	"Investigate, please." The human code came clearly. "Ship is rolling. We fell out. We're the lights." Venzeer knew that the personal mud tanks were open on top; the report was not really surprising.

	"All right. I'll keep you in sight. Head downhill if you can travel. It might be best if I stay where I can see you and the ship both, if it doesn't stop moving soon. Bill? Rek? Are you out of control, or can you stop and come back?"

	"I'm not sure about control," the Habra's voice came back. "I think we've stopped rolling, and I'll test."

	At the same moment the Erthuma code, Janice's tone this time, sounded. "Not sure of down. Armor neutral. Can see ship so far. Flying toward it." No effort had been made by the group to distinguish between the words for swimming and flying; even the Erthumoi had come to regard the difference as a quibble.

	Venzeer could now see the Compromise clearly, two or three hundred meters away. The fine sediment had stopped rising; presumably the rolling had stopped—

	Then he realized that the vessel was no longer on the bottom. It took him perhaps a second to guess the cause; the Erthuma report was plenty of clue. He called urgently. "Bill! Rek! You're going up! You must have lost the ballast when the ship rolled over!"

	"Tanks covered," came Hugh's code.

	"I guess whoever designed the covers didn't allow for copper's density, or somebody skimped the work. The slugs probably broke through after a few rolls. Bill or Rek! Do you have control?"

	"No," came the native's calm voice. "Most of the fan tubes seem to be clogged. I'm turning on all the heat I can give; maybe that will work. If it's mud, though, we'll have to go out with portable water jets and wash them clear."

	"How could there be mud here?" asked Rekchellet. "You said the fine stuff settles from the sunward side of the ring, over two thousand kilos from here."

	"A lot of it's extremely fine, and the currents in a five-hundred-kilo deep ocean can distribute stuff pretty evenly," replied Bill. "I'm hoping it's just ice, though."

	"How could ice be so finely powdered underwater?"

	"Never mind theory!" Venzeer snapped in his turn. "You're going up, and will be out of sight soon. Should I come after you, or stay with the ground types?"

	"Stay with us." The code message was immediate enough to seem emphatic. Venzeer felt a brief surge of indignation at getting an order from a wingless person, but the "person" part of the designation did mean something now.

	"Why? You have lights. We can come back for you, if the ship gets back at all. I may be needed to help clear out the fans."

	"Find ballast first. Never will if we don't mark it now. Stay where ship started up. Keep your light on." It was the woman's code tone. Her husband's followed.

	"Bill, run all fans you can. No matter how they point. Warm up surroundings."

	"I understand," replied the native. "You think it's ice." There was no interrogation in his tone.

	"Reasonable hope," replied Janice.

	"Why?"

	"Not at bottom. Probably shelf of middle ice. Hill pushed up into lower pressure, slowly changed to high ice. Micro crystals, loose, growing as you take them up. Not really sediment. Grew in place."

	"Could be," agreed the Habra. "But I hope we don't have crystals growing in the fan ducts."

	"Set jammed fans at lowest speed," Hugh suggested. "Engines will heat. May help."

	"If they don't burn out. I'll have to watch that. But it's worth trying."

	"Shielding good conductor. Ice should hold surroundings at local melting point."

	"Janice," Venzeer cut in, "I'm about where the ship started up. My lights don't show any of the ballast slugs."

	"Maybe powder settled on them. Could still be partly middle ice. Stay on the bottom. Don't risk being moved by currents, unless you can see a fixed mark."

	"Right. Can you see my light?"

	"Yes. Be there soon," Hugh replied. "Ship left trail. May not need light."

	"But do keep it on," added his wife.

	"If there's a track, the ballast should be somewhere along it," pointed out Venzeer.

	"We hope so, too."

	There was silence for a time, broken finally by Rekchellet. "Bill! It looks on my board as though a main fan has burned out."

	"I'm afraid you're right. It was jammed, and must have been too big for the heat to get far enough fast enough, even packed with ice. The other main one is running, and I'll be more careful with the steering ones. I'm trying to keep us bow down, so the one that's running will keep us from rising too fast, but I'm afraid the ice is still gaining on us. Can you still hear us, Venzeer? Erthumoi?"

	"Yes. You can't be very far up. I can't see your lights any more, though. Can you, Hugh or Janice?" The notion that Erthuma eyesight could ever be in any way superior to that of a Crotonite would never have reached Venzeer's consciousness a few weeks earlier.

	"No. Not for some time," replied Janice. "We've been looking down, anyway. Hugh, white lumps about the right size." The other three waited tensely.

	"We have two slugs," Hugh finally reported. "White dust on them. We've cleared them, we could carry them, but will wait till we find the others. Jan, leave your light here. We'll tie together again."

	"All right."

	"If all between us and you, Venz, should make a big pile. We can probably find them. You still want to help with ship?"

	"How would I find it? I'm committed to the ballast team now, it seems to me."

	"True. My mistake. Come toward our lights searching."

	"All right." This time his resentment of the order was only fleeting. After all, code was awkward, and requests took more words, and it was the most reasonable thing to do anyway. Venzeer quickly began to find slabs of copper.

	Some indefinite distance above, the Habra spoke to his remaining companion. "Rek, you take over. Keep bow down—you can tell which way is down even with the globe iced up, can't you?"

	"Easily. I have air in here. Down is where I settle."

	"All right. I'm taking a water jet outside. I'll use a safety line, of course, but be sure the lights stay on."

	"Right. Keep talking, so I know nothing's happened to you. I have full heat in the tubes, too."

	"I know. The hull isn't icing. It's too bad we can't heat your pressure sphere."

	"I'm warm enough."

	"I mean on the outside, so you could see."

	"Oh. That doesn't matter now as long as I can tell which way is down."

	"Surely you want to draw."

	"Just describe things to me, and I'll do my best."

	The descriptions were heard with interest, though faintly, by Venzeer, though not by his companions far below; sound travels well in water, and Crotonites can use their wing membranes for additional sound reception.

	The news, however, was not encouraging. Compromise was still rising, however slowly. Each kilometer of elevation dropped the pressure some eighteen atmospheres and raised the melting point of high ice almost a fifth of a kelvin. Ice crystals formed preferentially on other ice crystals, and the heat crystallization released was carried away too quickly to impede the resulting growth usefully. High ice is less dense than liquid water, so Compromise was becoming more buoyant minute by minute. If she reached a level where the tube heaters could not keep her main frame clear, a large snowball would hit the underside of the ice shelf some time in the next day or two.

	Of course, it might hit a solute-rich region and start melting again. Unfortunately, the Habras had no charts of the currents this close to Darkside, and there was no way to guess the chances of this. Neither Bill nor Rekchellet thought for an instant of counting on it; they had the explorer's willingness to take a chance, but were neither compulsive gamblers nor pathological optimists.

	Rekchellet had had plenty of practice with the controls, if not quite as much as Bill, and he did everything he could think of to get useful work out of such jets as were clear. Now and then the native was able to get another steering unit into action, but there was nothing he could do about the lost main unit. He had known this at first glance; not only was its engine burned out, but also when he had cut the power the unit had cooled down below local freezing temperature rather quickly. Water had frozen inside, and high ice expands when it freezes ...

	If only they had even a few of the ballast slugs. They hadn't; William had checked inside the tanks with the smashed tops, though almost sure it was a waste of time.

	He had gotten three steering units back into operation and was working on a fourth when his light showed what he had feared and expected. One of the thinner tubes of the ship's structure was turning white. For a moment he didn't dare look at others of the same size; maybe it was only a local blockage of heat-exchange fluid. But hope, especially a forlorn hope, wasn't enough. He had to know. He swept his light around. It wasn't.

	"Rek, I'm afraid we're out of luck. The ship itself is starting to ice."

	"And I can't get any more out the big fan we have. The other is hopeless, you say."

	"Right."

	"What will happen if I feed it power anyway? There'll be heat, at least, I'd say."

	"At least. I'd prefer not to risk shorting a fuser."

	"What do we have to lose?"

	"The ability to think of anything else, mainly."

	"Will your thoughts be heavy enough? We need weight or power. These pressure spheres—I suppose they changed things enough so your experience isn't—by Planner!"

	"What? Rek, have you—"

	"I've been as stupid as if I'd never had wings. Think, ground it! The air lock sphere is evacuated, the way I left it when I last came inside. Stay clear while I let water in! Eight meters inside diameter—over a hundred tonnes—there. Which way are we going now? I must be twins. How could I be so stupid all by myself?"

	"It was regular procedure. Our standard trim assumed both spheres empty."

	"I was still stupid. We're not in a standard situation. Have we stopped rising?"

	"Yes. Definitely. We're going back down, slowly, but we're going. All we have to do is find the others."

	"That shouldn't be hard. You can hear us, can't you, Venz?"

	"Yes, barely," came the answer. "Can you tell which direction our voices are coming from?"

	"Not very well. Generally up. Water carries sound too fast; we get direction by knowing which wing the sound waves hit first. I don't see how I can guide you; I don't know which way the ship is pointing when you talk. You'll have to find me."

	"But I can't get any direction either, from inside the sphere."

	"Then when you reach the bottom—pardon me, Janice, the shelf—you'll have to come outside and listen. Then you can give steering directions to Bill—for that matter, you can just have him follow you."

	"But how do I get outside? I'd have to evacuate the lock sphere again, and we'd start going up."

	"You'll just have to be quick."

	"I suppose so."

	"Then our troubles are over," Venzeer gloated. "As long as you don't go deaf before you get to the bottom."

	"My wings are as good as yours," retorted the illustrator. "Have you found all the ballast down there?"

	"We haven't counted very carefully," Hugh responded, not worrying how the code added to the suspense of his hearers. "There were five thousand hundred-kilo ingots of copper in the tanks, as I recall. Venz found a real hill of the things before we got back together. The few Jan and I had turned up were just strays; I don't think they mean much, but we've toted them back to the main pile. Just keep driving down. You can't have gone very far sideways."

	This proved an optimistic guess. The sub had gone out of range of even the Compromise's lights; she struck sharply on the solid surface of the shelf without having been spotted by the watchers below. It seemed to be dark, hard, semitransparent ice, level as far as Bill could tell, very different from the hillside the Compromise had originally struck. There was much vegetation, some of which was disintegrating, bubbling furiously, where crushed by the sub's arrival. Presumably azide and enzymes, released and allowed to meet by the rupture of cell walls and organelles, were reacting to give free nitrogen—one of the known contributing causes of storms elsewhere in the ocean. The bubbles vanished almost instantly as the gas cooled and went into solution in two thousand atmospheres of pressure.

	Rekchellet could not see any of this, since his sphere was still frosted, and Bill didn't notice; it was nothing unusual to him. Venzeer heard the rushing, boiling sound briefly, and then the ship's thrusters when he listened more carefully.

	"Are you down?" he called.

	"Yes," replied Rekchellet. "You can't see our lights, I assume. I'll get outside. Bill, I'll have to evacuate the lock, so you probably can't keep us on the bottom for the next minute or two."

	"No matter."

	Even the Erthumoi could hear the sea rushing into the lock sphere, but in their armor could make no guess at the sound's direction. Venzeer was pretty sure of it, and indicated to the others which way they should look.

	"I'm outside," the recorder called finally. "Make some kind of noise."

	Venzeer began talking. Hugh picked up one of the copper slugs and let it fall on another. Rekchellet was able to hear both sounds, but reported that the second was much clearer.

	"Can you tell the direction?" asked his practical companion. There was a pause; Hugh, without instructions, continued his metal-on-metal broadcast.

	"This way, I think, Bill." Rekchellet swam slowly away from the sub.

	"What do you mean, you think?" cried Venzeer.

	"I can't get rid of the feeling you may be behind me instead of in front. I keep feeling sure first you're one way, then the other."

	"Can you feel or see any currents?" asked Janice.

	"Sure. The plants show those. If I stop swimming, I'm carried past them. They lean, too."

	"Do we seem to be up or downstream from you."

	"Up."

	"That makes sense. You would have been carried down while you were out of sight."

	Rekchellet was impressed by this point; Bill was not. "You can't expect currents to hold direction for any time," the native pointed out. Janice had already made her point about the chaotic nature of Habranha's weather and was not ready to dispute the voice of experience, but her husband offered what seemed to be the only sensible advice.

	"Keep on the way you are, and let us know if the currents change. I'll keep tapping."

	For fully half an hour the journey continued. To Bill's admitted surprise, the current remained steady. Travel was slow, much slower than Rekchellet could have flown, because Bill had a great deal of difficulty steering the sub; most of its main drive had to be used to keep it near the bottom even with the lock full of water; and since the thruster itself was fixed in the hull, the Compromise had to travel almost nose down. Once, Rekchellet reported that the guiding sound was getting weaker, but after some discussion it was decided that this represented Hugh getting tired and dropping the ingot from a lower height. He and his wife standardized the dropping distance and took turns at the muscle work, and Rekchellet and the submarine continued their original direction.

	Venzeer and his companions strained their eyes in the direction the Crotonite had first claimed to hear the sub's thruster, until Hugh noticed that this was also the direction from which the current was coming, and after some hesitation mentioned the fact. Thereafter they divided their attention both ways until a faint glow became visible—downcurrent. No one discussed the directional ambiguity of sound, even though one Crotonite had been right. Tact was still the order of the day.

	"Told you my wings were good enough," was the only remark made. This was by the recorder as Bill brought the submarine to a halt as close to the pile of ingots as he could. Venzeer said nothing.

	But Rekchellet's wings were not good enough for something else. Neither were Venzeer's or Bill's. None of them could lift one of the ingots alone, and the various rope slings which were improvised to let the Crotonites work together proved very awkward. A hundred-kilogram mass of copper, underwater in Habranhan gravity, weighs just over fifteen kilograms. A few hundred pieces of copper were moved by the flyers, but the rest were carried from pile to tanks by the wingless members of the team. A fifteen-kilogram weight means something to a pair of Erthuma legs when swim fins are involved, but with the structure of a Habranhan submarine there is no need to swim. One can climb very easily.

	It was several days' work, and man and wife were rather exhausted at the end of the job. They didn't argue very hard when Bill pointed out regretfully that there was no way of getting to the Solid Ocean on one main thruster. They'd just have to try again.

	They also refrained from making any remarks about relative flying skills. Janice still liked the Crotonites, and even her husband admitted that the flyers had put up well with the display of their personal inadequacy, though they couldn't have been very happy about it. Or, as Hugh remarked in an afterthought, really appreciative of what the Erthumoi had done for them.

	"Why should they be?" asked his wife. "The ground crawlers were saving their own lives, too."

-

III. Between

	Hugh still considered them ungrateful, and so he even tried to convince his wife, until they were back in atmosphere and could talk normally again. A day after getting rid of the diving fluid, revived by appropriate relaxation, they met with Bill and the Crotonites for a planning session on the next trip. Hugh fully expected the latter to say they didn't want Erthumoi along. He knew such a reaction would be illogical, but he still regarded Crotonites as illogical beings; after all, they had a low opinion of people who couldn't fly, didn't they?

	Venzeer and his companion greeted them cordially, however, making the man wonder what they were hiding. The discussion lasted several hours and involved redesign of the covers for the ballast tanks, methods of fastening the individual ingots in place, and other perfectly reasonable matters. Venzeer even suggested that some progress might be expected in development of a diving fluid for Crotonites. It was agreed, however, that this was not something they should wait for.

	The meeting ended with many points settled, and agreement that it would be resumed the next day. As they parted, Rekchellet handed Janice a sheet of record film.

	"I thought this was worth saving," he remarked.

	The Erthuma couple looked at the picture, obviously a record from Rekchellet's drawing pad. For a moment, there seemed nothing special about it; it was a well-done sketch of two Erthumoi, with Hugh's and Janice's faces easily recognizable. It was not a record of anything they remembered from the trip, though the background included the Compromise and some flying figures which might have been William and the Crotonites. The Erthumoi figures, however, looked a little strange; they were wearing cloaklike garments which neither remembered having used on either journey, even that on the iceberg, or any other time since reaching Habranha.

	Janice was first to see that Rekchellet was an artist, not just an illustrator.

	The garments weren't cloaks. They weren't even garments. He had portrayed the Erthumoi with wings.

The End