“The river stayed about the same size all the way down,” the sailors reported. “It wasn’t being fed from anywhere, And it didn’t seem to be evaporating. It wound among the stones a lot, when it got down to where they were. Then we began to run into the funniest obstructions. There would be a sort of dam of ice, with the stream running around one end or the other of it. Half as cable or so farther on there’ be another dam, with just the same thing happening. It was as though some of it froze when it met the ice among the stones, but only the beginning part. The water that followed stayed liquid and went on around the dam until it found some ice. The dams would build up to maybe half a body length high before the following water would find its way around. We reached the last one, where it was still happening, just a few minutes ago. We’d seen the bright cloud rising over the ship before that, and wondered whether we ought to come back in case something was wrong; but we decided to carry out orders at least until the river started l to lead us away from the Kwembly again.”
“Good,” said the captain. “You’re sure the stream wasn’t getting any bigger?”
“So far as we could judge, no.”
“All right. Maybe we have more time than I thought, and it isn’t a forerunner of the same thing that brought us here. I wish I understood why the liquid was freezing in that funny way, though.”
“We’d better check with the human beings,” suggested Borndender, who had no ideas on the matter either, but preferred not to put the fact too bluntly.
“Right. And they’ll want measurements and analyses. I suppose you didn’t bring a sample of that river,” he said, rather than asked, the newcomers.
“No, sire. We had nothing to carry it in.”
“All right. Born, get containers and bring some back; analyze it as well as quickly as you can. One of these men will guide you. I’ll go back to the bridge and bring the humans up to date. The rest of you get tools and start chipping ice so we can use the main lock.”
Dondragmer closed the conversation by starting to climb the ice crusted hull. He waved toward the bridge as he went, assuming that he was being watched and perhaps even recognized.
Benj and McDevitt had managed to keep track of him, though neither found it easy to tell Mesklinites apart, and were waiting eagerly when he reached the bridge to hear what he had to say. Benj in particular had grown even more tense since the search under the cruiser had been interrupted; perhaps the helmsmen had not been there after all — perhaps they had been among the newcomers who had arrived to interrupt the search — perhaps — perhaps…
McDevitt was a patient man by nature and liked the youngster, but even he was getting irritated by the time Dondragmer’s voice reached the station.
The report fascinated the meteorologist, though it was no consolation to his young companion. Benj wanted to interrupt with a question about Beetchermarlf, but knew it would be futile; and when the captain’s account ended, McDevitt immediately began to talk.
“This is not much more than a guess, Captain,” he began, “Though perhaps you scientists will be able to stiffen it when he analyzes those samples. It seems possible that the pool around would was originally an ammonia-water solution — we had evidence of that before — which froze, not because the temperature went down, but because it lost much of its ammonia and its freezing point went up. The fog around you just before the whole trouble started, back on the snowfield, was ammonia, your scientists reported; I’m guessing that it came form the colder areas far to the west. Its droplets began to react with the water ice, and melted it partly by forming an eutectic and partly by releasing heat — you were afraid of something of that sort even before it happened, as I remember. That started your first flood. When the ammonia cloud passed on into Low Alpha the solution around you began to lose ammonia by evaporation, and finally the mixture which was left below its freezing point. I’m guessing that the fog encountered by Stakendee is more ammonia, and provided the material for the rivulet he found. As it meets the water ice near you they dissolve mutually until the mixture is too dilute in ammonia to be liquid any more — this forms the dam your men described, and the liquid ammonia still coming has to find a way around. I would suggest that if you can find a way to divert that stream over to your ship, and if there proves to be enough of it, your melting-out problem would be solved.” Benj, listening in spite of his mood, thought of wax flowing from a guttering candle and freezing first on one front and then another. He wondered wheter the computers would handle the two situations alike, if ammonia and heat were handled the same way in the two problems.
“You mean I shouldn’t worry about a possible flood?” Dondragmer’s voice finally returned.
“I’m guessing not,” replied McDevitt. “If I’m right about this picture, and we’ve been talking it over a lot up here, the fog that Stakendee met should have passed over the snow plain you from — or what’s left of it — and if it were going to cause another flood that should have reached you by now. I suspect the snow, which was high enough to spill into the pass you were washed through, was all used up on the first flood, and that’s why you were finally left stranded where you are. If the new fog hasn’t reached you yet by the way, I think I know the reason.
The place where Stakendee met it is a few feet higher than you are, and air flowing form the west is coming downhill. With Dhrawn’s gravity and that air composition there’d be a terrific foehn effect — adiabatic heating as the pressure rises — and the stuff is probably evaporating just as it gets to the place where Stakendee met it.”
Dondragmer took a while to digest this. For a few seconds after the normal delay time, McDevitt wondered wheter he had made himself clear; then another question came through.
“But if the ammonia fog were simply evaporating, the gas would still be there, and must be in the air around us now. Why isn’t it melting the ice just as effectively as though ii were in liquid drops? Is some physical law operating which I missed in the College?”
“I’m not sure where state and concentration would make all that much difference, just from memory,” admitted the meteorologist. “When Borndender gets the new data up here I’ll feed the whole works into the machine to see wheter this guess of our s is ignoring too many facts. On the basis of what I have now, I still think it’s a reasonable one, but I admit it has its fuzzy aspects. There are just too many variables; with only water they are practically infinite, if you’ll forgive a loose use of the word, and with water and ammonia together the number is squared, if not worse.
“To shift from abstract to concrete, I can see Stakendee’s screen and he’s still going along beside that streamlet in the fog; he hasn’t reached the source, but I haven’t seen any other watercourses feeding in from either side. It’s only a couple of your body-lengths wide, and has stayed about the same all along.”
“That’s a relief,” came the eventual response. I suppose if a real flood were coming that river would be some indication. Very well, I’ll report again as soon as Borndender has his information. Please keep watching Stakendee. I’m going outside again to checked under the hull; I was interrupted before.” The meteorologist had wanted to say more, but was silenced by the realization that Dondragmer would not be there to hear his words by the time they arrived. He may also have been feeling some sympathy for Benj.
They watched eagerly, the man almost as concerned as the boy, for the red-and-blank inchworm to appear on the side of the hull within range of the pickup. It was not visible all the way to the ground, since Dondragmer had to go forward directly under the bride and out of the field of view; but they saw him again near the point where the rope which had been used to get him out a few minutes earlier was still snubbed around one of Borndender’s bending posts.