"It's raining," Raeker said simply. "The lake is probably sulphuric acid, I suppose fairly dilute by this time of night, and is enough warmer than the air so the water evaporates before it strikes. There wouldn't be any waves; there's no wind. Three knots is a wild hurricane on Tenebra."
"With all that heat energy running around?" Rich was startled.
"Yes. There's nothing for it to work on - I use the word in its physical sense. There isn't enough change in volume when the atmosphere changes temperature, or even changes state, to create the pressure differences you need for high winds. Tenebra is about the calmest place you'll find inside any atmosphere in the galaxy." "Does that jibe with your remarks about earthquakes a while ago?" It was a measure of Aminadabarlee's revived confidence that he could talk of something besides the stupidity of human beings.
"No, it doesn't," admitted Raeker, "and I'll have to admit, Easy, that there is a possibility that you will encounter some waves if you float there long enough. However, you won't be able to call them weather, and they won't carry you to any more interesting places. I'm afraid you've seen about all you can expect to, young lady; you may as well come up and be properly rescued."
"All right. Only I'd like to know just what's going to make this thing float, and whether the trip up will be as rough as the one down was."
"It won't. You'll go up vertically, and much more slowly. You're going to ride a balloon. The atmosphere there is mostly water, with enough ions loose to make it a decent conductor. The largest part of your hull is divided into cells, and each cell further divided in two by a flexible membrane. Right now, those membranes are squeezed flat against one wall of each cell by atmospheric pressure. When you start the electrolysis units, some of the water will be decomposed; the oxygen will be piped outside the hull, but the hydrogen will be released on the other side of the membranes and gradually drive the air out of the cells. The old bathyscaphe used the same idea, only it didn't need the membranes to keep the two fluids from diffusing into each other."
"I see. How long will it take to make enougft gas to lift us?"
"I can't tell; we don't know the conductivity of the atmosphere. Once you start things going, there's a bank of ammeters above the switches for each individual cell; if you'll give me their reading after things start, I'll try to calculate it for you."
"All right. Where are the - Oh, here; you labeled them decently. Upper right, a bank of twelve toggles, with a gang bar and a master?"
"That's it. You can see the meters above them. Close the lot, hit the master, and give the readings."
"All right." The thin arm reached up and out of the field of vision, and everyone could hear the switches click. Easy pulled her hand back to her lap, settled back into the chair under her three hundred pounds of weight, eyed the dials one after another, and said, "The readings are all zero. What do I do now?"
V. PEREGRINATION; CONSIDERATION; ESTIVATION
NICK had chosen a fire on the landward side of the hill, so he was the first to have to consider the sea-level problem. In the home valley, of course, the water at night had never gotten more than thirty or forty feet deep; slow as the runoff was, enough always escaped at the valley foot to keep the village itself dry. He knew, from Fagin's lectures, that the water which flowed away must eventually reach something like a sea or lake; but not even Fagin had stopped to think of what would happen then - naturally enough; the surface of Earth's oceans compared to the volume of an average day's rainfall doesn't correspond to much of a sea-level rise, to put it mildly.
On Tenebra, the situation is a trifle different. There is no single giant sea basin, only the very moderate-sized lake beds, which are even less permanent than those of Earth. What this difference could mean in terms of "sea" level might possibly have been calculated in advance, but not by any of Nick's people. At first, there was nothing to worry about. The great, cloudy drops drifted into sight from far above, settled downward, and faded out as the radiation from the fires warmed them a trifle. Then they came lower, and lower, until they were actually below the level of the hilltop on all sides.
Once a sharp quake struck and lasted for half a minute or more, but when Nick saw that the spit of land joining the hill to the shore was still there, he put this from his mind. Something much more unusual was starting to happen. At home, raindrops which touched the ground after the latter had been cooled down for the night flattened into great, foggy half-globes and drifted around until a fire obliterated them; here they behaved differently. Drops striking the surface of the sea vanished instantly and by Nick's standards, violently. The difference in pressure and temperature made the reaction between oleum and water much less noticeable than it would be in an Earthly laboratory, but it was still quite appreciable. After each such encounter, it could be seen that further raindrops falling on the same area faded out a little higher than usual for a few minutes; Nick judged correctly that some heat was being released by the reaction.
He had been watching this phenomenon for some time, interrupted twice by the need to relight his fire when a particularly close drop smothered it, when he noticed that the hill was not an island. This startled him a trifle, and he turned all his attention to the matter. The quake hadn't done it; he particularly recalled seeing the tombolo intact after the shaking was done. It didn't take him too long to conclude that if the land wasn't sinking, the sea must be rising; and a few minutes' close watch of the shore line proved that something of that sort was happening. He called the others, to tell them of what he had seen, and after a few minutes they agreed that the same thing was happening on all sides of the hill.
"How far will it come, Nick?" Betsey's voice was understandably anxious.
"I don't see how it can get this high," Nick answered. "After all, it hasn't risen as much as the water in our own valley would have by this time of night, and this hill is nearly as high as the village. We're safe enough."
It got a little harder to stick to this belief as the hours passed and the sea grew higher. They could see the pools on shore swell and overflow into the main body; as time went on, more than one great river formed, carrying runoff from no one knew what drainage area. Some of the rivers were frightening, their centers as high or higher than the hill itself before they spread out and merged with the sea. By this time the violence of water-meeting-acid had subsided; the sea, at least near the shore, was pretty dilute.
Of course, "near the shore" might be too casual a statement. No one on the hilltop could tell for certain just where the shore was now. The route they had followed was deep under the acid sea, and the only evidence that dry land existed was the rivers which still came into view above sea level.
The island that had been a hill shrank steadily. The cattle seemed unperturbed, but were driven inside the ring of fires. Then this had to be drawn in - or rather, others had to be built closer to the hilltop; and at last people and animals huddled together behind a single ring of glowing heat, while the sea bulged upward at their feeble protection. The raindrops were clear now; they had fallen from high enough levels to lose their suspended oxygen, and inevitably the last fires succumbed. Their heat had for many minutes past been maintaining a hollow in the surface of the sea; and as they cooled, the ocean reclaimed its own. Seconds after the last spark died every living being on the hilltop was unconscious, and a minute later only a turbulent dimple in the surface of the sea showed where the slightly warmer hilltop was covered. Nick's last thought was to the effect that at least they were safe from animals; they would be uncovered long before anything could get at them.
Apparently he wasn't quite right. When they woke up the next morning and brushed the thin frost of quartz crystals from their scales, all the people were there, but the herd seemed to have diminished. A count confirmed this; ten cattle were gone, with only a few scales left behind. It was fortunate that the animals were of a species whose scale armor was quite frail, and which depended more on its breeding powers to survive; otherwise the meat-eaters who had come in the night might have made a different choice. The realization that things lived in the sea came as a distinct shock to the entire party. They knew just about enough physical science to wonder where any such creature got its oxygen.
But the new situation called for new plans.
"There seems to be a catch in the idea of telling Fagin just to hunt along the seashore until he finds us," Nick commented after breakfast. "The seashore doesn't stay put too well. Also, we can't afford to stay near it, if we're going to lose eight or ten per cent of our animals every night."
"What we'll have to do is some more mapping," commented Jim. "It would be nice to find a place protected by sea but which doesn't get submerged every night."
"You know," remarked Nancy in a thoughtful tone, "one could find a rather useful employment for this place right here, if the proper people could be persuaded to visit it." Everyone pondered this thought for a time, and the tone of the meeting gradually brightened. This did sound promising. Idea after idea was proposed, discussed, rejected, or modified; and two hours later a definite - really definite - course of action had been planned.
None of it could be carried out, of course, until it was possible to get off the island, and this was not for a dozen hours after sunrise. Once the tombolo appeared, however, everyone went into furious activity. The herd - what was left of it - was driven ashore and on inland by Betsey and Oliver. Nick, making sure he had his axe and fire-making equipment, started inland as well, but in a more southerly direction. The other five fanned out from the base of the peninsula and began mapping the countryside for all they were worth. They were to determine as closely as possible how much of the area was submerged by the sea at its highest and make their report no later than the second night following. The group was then to pick a more suitable campsite to the north of the previous night's unfortunate choice. They were to settle at this point, and send a pair of people each morning to the base of the peninsula until either Nick returned or ten days had passed; in the latter event, they were to think of something else.
Nick himself had the task of contacting Fagin. He alone of the group was just a trifle unclear on how he was to accomplish his job. Tentatively, he planned to approach the cave village at night, and play by ear thereafter. If Swift's people had gotten into the habit of moving around at night with torches, things would be difficult. If not, it might be easy - except that his own approach would then be very noticeable. Well, he'd have to see.
The journey was normal, with enough fights to keep him in food, and he approached the cliff on the evening of the second day. He had circled far around to the west in order to come on the place from the cliff top; but even so he halted at a safe distance until almost dark. There was no telling where hunting parties might be encountered, since there was a path up the cliffs in nearly constant use by them. As darkness fell, however, Nick felt safe in assuming that all such groups would be back at their caves; and checking his fire-lighting equipment once more, he cautiously approached the cliff top. He listened at the edge for some time before venturing to push his crest over, but no informative sounds filtered up and he finally took the chance. The cliff was some three hundred fifty feet high at that point, as he well knew; and he realized that even a single spine would be quite visible from below by daylight. It might be somewhat safer now, since no fires appeared to have been lighted yet.
When he finally did look, there was nothing to see.
There were no fires, and it was much too dark for him to see anything without them.
He drew back again to think. He was sure the village and its inhabitants lay below, and was morally certain that Fagin was with them. Why they had no fires going was hard to understand, but facts were facts. Perhaps it would be safe to try to sneak up to the village in the dark - but the rain would come soon, and that would be that.
Then he had another idea, found some small wood, and went to work with his fire-making tools, a drill and spindle made from tough wood. He rather expected some response from below when he got a small blaze going, since it lighted up the sky more effectively than daylight; but nothing happened until he executed the next portion of the idea, by tossing a burning stick over the edge of the cliff. Then everything happened at once.
The light showed Fagin, standing motionless fifty yards from the foot of the cliff. It showed an otherwise empty expanse of rock and vegetation; the people were in their caves, as usual. That, however, was only temporary.
With the arrival of the fire, a rattle of voices erupted from the caves. Evidently, if they ever slept, they weren't doing it yet. After a moment Swift's tones made themselves heard above the others. "Get it! Get wood to it! Don't just stand there as if you were wet already!" A crowd of figures emerged from the rock and converged on the glowing twig; then they spread out again, as though they had all realized at once that no one had any wood and it would be necessary to find some. Plants were wrenched up from the ground by a hundred different hands and carried, or sometimes thrown, toward the spark. Nick was far more amused than surprised when it went out without anyone's succeeding in lighting anything from it, and was only academically curious as to whether it had burned out of its own or been smothered by its would-be rescuers. His attention was not allowed to dwell on the problem for long; Swift's voice rose again over the disappointed babble. "There's a glow on top of the cliff, and that's where the fire came from! Someone up there still has some; come and get it!" As usual, obedience was prompt and unquestioning, and the crowd headed toward the trail up the cliff. Nick was a trifle surprised; it was close to rainfall time and the cave dwellers were carrying no fire. Something drastic must have happened, for them to overcome their lifelong habit of keeping to the caves at night. However, it was hardly the time to speculate on that subject; the cave men were seeking fire, and Nick happened to have all that there was around at the moment. It took him about five seconds to dream up the rest of his idea. He lighted a stick at his small blaze and started toward the head of the trail from below, lighting all the plants he could reach as he went. When he reached the trail he tossed aside the nearly spent torch he had been using, made himself another which he hoped was small enough to shield with his body, and headed on along the cliff top. If the cave men were satisfied to take some fire, well enough; if they wanted him too, perhaps they'd look along the fire trail he had laid, which would lead them in the wrong direction. He wasn't really hopeful about this, knowing their skill at tracking, but anything seemed worth trying once.