explanation: the space behind them, whatever it was, where the methane had been going was at last being filled up. Barlennan had been learning, however; he told himself firmly that there might be other explanations. He put the question before the others, more as a distraction than in hope of alternatives. He got none, but distractions were still useful even with the hoods; there was still a lot, no one could guess how much, of Mesklin overhead. It was also getting somewhat cooler, they could feel, though the slush underfoot was still slush and still provided very poor traction. And they were getting hungrier all the time. That in itself made travel more and more difficult. Chemically, evolution in an energy-demanding environment had given them the equivalent of a very large human glycogen reservoir for their size, but even that had its limits. They were nearing those limits. The juice tank was now very dilute; they had not bothered to close the valve. This made the taste more bearable when they finally gave up and tried it. However, there is little to be gained by adding more catalyst, even just the right catalyst which this was not, when the supply of reactant is nearly gone. No one felt any less hungry than before, and the cook/flight engineer, whose digestive equipment might have been affected by his earlier experiments, was extremely uncomfortable for a time. He was quite unable to crawl or swim, and the party had to wait where it was. Another roar and shudder of settling rocks enabled him to find some strength, and they moved on. The current was nearly gone, and they were guided now by the tracker, much more slowly even than before. The captain made the next report hoot by himself, hoping that its relative weakness would give the listeners a suggestion of their plight. It didn’t work; the sailor on watch below the surface who had been doing the answering didn’t notice the difference. There was a good reason for this, it was realized later. The captain was now much closer to the searchers. However, the rumbling echoes of his voice still lasted about as long as ever and hid the volume difference. He himself failed to notice any change in the answer; he blamed it later on the distraction caused by hunger. Hars, more than any of the others, hated to feel his energy going. He also hated to fail, and he still felt responsible for the tracker he was carrying. He probably had the least idea of any of the four why the echo problem should be less in air than in methane, but he had reached a point where anything seemed worth trying. They had done all their calling under methane, for obvious reasons; sound traveled better there, as everyone knew. On the other hand, one grew tired more quickly there, though Hars didn’t know why. One was lighter below the surface, obviously, but for some reason had more endurance above. “Hydrogen concentration” was not even words to him. But if there were anything to climb out on, he knew he would feel better. He began to mutter aloud. Just mutter. He would have done something else if he had been leading, but the captain was in front. The others could hear, of course, and Barlennan began to worry. Sherrer’s lack of balance had been serious enough; Hars was by far the most powerful of the group, even now. If he were to panic, it might make the final difference. Especially with them roped together. After a little thought, he spoke to the sailor. “Hars, what’s the matter?” The pilot was actually embarrassed. “Well, Captain, I was wondering whether we could find a slope and get up in air for a little while. We could do with some rest, and it would be better than under methane. I didn’t realize I was thinking out loud.” Bartlennan thought quickly. Shortage of air — hydrogen — at this point was not actually as serious as shortage of food, but it was certainly much more uncomfortable. It didn’t much matter where they were if one of the rock settlings took place near them. They were as likely to be found in one place as another, after all; and if they really couldn’t get out from under— “All right. Change the setup. Hars and I will travel side by side, a rope length apart. Sherrer will be at my right, Karondrasee at Hars’ left. It will be harder to keep the line straight, but we’ll be more likely to find an upslope.” It took some time to rearrange the safety lines, but they were slightly rested when it was done and they were advancing in the new formation. It was harder to travel, however, since they could not be as much help to each other. Even the captain was ready to call a halt where they were when the rope connecting Karondrasee and Hars dragged on the bottom. There was some sort of bulge. Hope of a sort began to rise as they examined and found a continuing slope. A solid one, of rock. The hope was mostly for comfort, not rescue, but the comfort was that of fresh air. They crowded together and began to creep upward. The slope was very shallow, and not difficult to climb even in their conditions; and for a while all feared that it might not reach the surface. Fortunately, all but Hars had to stop for rest before they reached surface. With the four huddled together to rest, there was enough slack to let the pilot crawl a little ahead of the others, and in less than five body lengths he broke the surface. With his encouragement and help, the other three also emerged into air, and relaxed gratefully. Nearly starved, they were really in no state for rest to do them much good, but they could still enjoy the sensation. Even Barlennan waited much longer than he should have before issuing the order to go on. His mind and conscience argued against giving up, but he knew that more time in air would not really help. Another rock shudder emphasized this, but still he hesitated. Lying still felt so good— So he had not yet spoken, and not yet decided to, when airborne sounds reached them. Voices. Not really understandable yet, but obviously broken up into words this time. The four hooted in unison, reflexively. Shorter wave lengths don’t diffract so badly, and sound waves are much shorter in air. The only real question then was whether Dondragmer’s people would climb down or Barlennan’s climb up, and that was easy to settle. The distance wasn’t great; the mate’s party could see how close they were to river level, but the captain’s group lacked the needed strength. The members of the net above were out in daylight, able to look down at the spaces below, where they would descend into unknowable depths. Well, not really unknowable; the captain and the others obviously weren’t very far down, but the word was down. But they could climb down. The mate, still attached to four safety lines, descended with food, and after half a dozen false turns managed to deliver it. Then, one at a time, rested and fed, each with three lines firmly attached to him, the balloonists were partly hauled and partly climbed up to the web. A sailor brought the lines back down for the next rescue, and another one for the next, and when one descended for the last time, he and Barlennan used two ropes apiece to get back to daylight. There had been some debate about the communicator and the tracker. The former had been hauled up ahead of the captain on a pair of carefully fastened lines, but the inertial equipment had gone up even earlier, still fastened to Hars. It remained attached to him until everyone had crossed the river to the other communicator; he refused to abandon the duty until the whole group, except the ones still at the rocket, was together. The Flyers understood, they thought. They certainly didn’t complain. All Barlennan could overhear and understand was another of their theoretical arguments. “Look, there’s only one explanation. We know that rock is sedimentary—”
“Know?”
“Well, it’s pretty obvious. One of the layers of the plateau, just below the foot of the cliff, has to be ammonia. That’s mineral there. A lot of it was melted by the falling rock, and the Mesklinites smelled it—”
“Smelled something like it.”
“What else could that be?”
“How do I know? I’m not a Mesklinite.” A third voice cut in. “The two of you are just gabbling. We haven’t seen a layer that looked like ammonia — it’d be white, like ice.”
“It would be ice.”
“All right, but we haven’t seen any.”
“It’s underground at river level.”
“But how could—?”
“That’s what I’m saying! We’ve got to check — I mean, Barlennan’s people have to check—”
“How? They don’t have drills, or shovels, or picks, and you can’t expect a Mesklinite to go tunneling, do you?” The captain had never heard this verb, but context suggested its meaning, rather too clearly. “Why not? Barlennan’s had lots of time underground now, and he’s still all right.”
“How do you know he is?” The captain started to tune out, as usual. Just another of the theory-based wrangles among Flyers, which of course might lead to something later. Then he saw what the something probably would be. The Flyers were very persuasive beings— Any being with muscles and a nervous system complex enough to consider alternatives consciously can shudder. Dondragmer was obviously listening, too.
