“Why not?” Molly couldn’t help asking. “Your front and rear look the same to me—I could never see why you cared which way you were going. Joe doesn’t seem to.”
“Your right and left look the same to me, but you seem to prefer to use your right,” replied Charley. “Ouch! If we must talk, let’s stick to essentials. I’ll have to be careful moving; if that broken arm or leg shell cuts inner sac, it could be bad. There; I’m turned around. I’ve bent a piece of the hull sheeting to hold the light, since I can’t do that and nip keys with the same digits. I’m traveling. Down, judging by large-drop motion. I trust that is the end of this river; traveling without them may be slow, but I feel better that way from now on.”
“You’re not going to wait for us, then?” Carol asked innocently.
“I don’t think so. We don’t know this is your river, after all, and I wouldn’t be much help to you now if we did meet. If it is, maybe you’ll catch up to me; I won’t be going very fast. Jenny, I wouldn’t mind hearing now what you think I ran into that looked so much like water.”
“As I said, two guesses and a combination. I’d vote for hydrogen peroxide, but it might have been hydrazine or a mixture of the two. The first is most likely to have been really concentrated in that reflux system; as I recall, hydrazine gets to a constant-boiling mixture with water while still pretty dilute. Also, if there had been hydrazine in the river, it would have reacted with the peroxide pretty completely as the lat-ter’s concentration got high.”
“Joe!”
“Yes, Molly.” The Nethneen didn’t need to have her thought specified. “That’s what could have gotten them, perhaps. Of course…”
“We haven’t thought of everything!” All three women chanted this practically in unison, as it came to the Human’s ears. She assumed Carol and Jenny must actually have been slightly ahead of her, allowing for translator delay.
“We’ve thought of enough.” It was Carol who continued. “There is a reasonable chance, approaching certainty, of higher-boiling things than water getting concentrated toward the bottom of this big condenser, and there’s a demonstrated certainty of explosives being around whether that’s how they originate or not. I say we still follow the river since it remains the best guide downward; it must have done a reasonable amount of erosion, after all, no matter how young the planet is. We treat it very respectfully, though. If we find it shrinking, we assume that little if any of it is water, and get even more careful. The main thing is we keep going down. So does Charley. As long as we can travel, and as long as we can tell which way is down, we travel down. Joe does not come to meet us unless something else happens and we get stopped; and if he does have to do that, Jenny, I strongly advise that you leave your lab, much as I hate to suggest it, and take his route to the big cave and be there to back him up.”
“I agree. I admit I hope that does not become necessary.”
“Don’t we all. But, Joe, you’d better send one of your little machines—maybe several for safety—back to your entrance and have them wait there so they can feed the model to Jenny’s mapper if she does have to come. You can treat them that independently, can’t you?”
“Yes.” Molly wondered whether Joe was as relieved at being able to give that answer as she was at hearing it. “I will send back six. As far as I know, there was no danger to them along that path, but…”
He stopped. This time no one made the obvious completion. Carol simply approved.
“All right. Let’s move. I want a shampoo as much as Molly wanted her bath, but someone’s got to stay in shape to complete this tour.”
Four hours.
“I’m out of touch with them, of course, but the mappers should be back at the surface by now, Jenny.”
“They are. My own computer has received and stored the model they were carrying. I am returning to the tent. I would return your machines to you if I could control them.”
“Beam out five zeros, five ones, then five ones and five zeros on Band 2471. I still foresee a few things.”
Twelve hours.
“Molly, I think I do see the other side of this river.”
“Are we flowing or falling right now?”
“Flowing, more or less. Just a minute while I swing us over that way. Yes, there is an opposite bank; the whole thing is less than a kilometer wide.”
“How big is the cave we’re in now?”
“No idea. I can’t see roof or walls, no matter what I do with my lights.”
“Anything ahead?”
“Just more river, right now.”
Fifteen hours.
“There’s not much in this machine close enough to its original shape to measure the fall distance with, but gravity is less than ten. The real problem is finding a place where wind isn’t blowing, so I can let something fall, now that this robot doesn’t have a hull any more.”
“We’ve been having some wind troubles, too, Charley,” replied Carol. “We never did have a hull, but now an occasional big drop is being lifted off this river and carried back upstream, and I don’t always see it coming as soon as I should. Since there isn’t much left of the river now, I’m really afraid of hitting the drops. You at least had some protection and a little distance when yours went off.”
“Still flow, or some straight fall?”
“Two straight-down sessions since we last checked in, but nothing like your terminal region. The very small drops got blown back up, but the big stuff kept falling.”
Twenty-two hours.
“Joe.” Charley’s voice was little more than a whisper, but it went out on the general channel. Joe acknowledged. “I think the passage walls around me are different. I never saw the mud you and the others were talking about, but 1 have seen mud. Maybe I’m getting there. Keep your radar hot.”
“We’re still rock, but the river is practically gone,” Carol came in. “I think I see it disappearing over another fall ahead. I’d almost bet it won’t reach the bottom. I wonder if we’ve joined your path.”
“There’ll be no easy way to tell,” answered the Kantrick. “I haven’t had many very good looks at the route I’ve been following since then; I’ve simply done my best to go upwind. Even if I’d seen it all, I couldn’t remember the details well enough to give you a helpful description.”
“I know. Don’t worry. We’d never be really sure anyway. The real worry is the explosive river; once we’re away from that we’ll just use the wind, too.”
“Why did you follow the river if you feel it’s so dangerous?” asked Jenny.
“Speed. Almost certainly the quickest way downhill. I want to get Molly to help as fast as possible. I’ll be less scared once we’re past it, but no less worried. There—I was right. We’re into another kame from somewhere near the top, and the stream is falling. Slowly. Very slowly. There aren’t any really small drops any more; the waterfall, or peroxidefall, or whatever it is just comes gradually apart and big shimmery blobs of liquid spread out through the cave. Over toward the side they fall a little faster—some of them faster than I’ve seen anything but us go downward for a long time. Maybe eddies—downdrafts. I have to keep alert, but they’re not too hard to dodge. I hope the bottom isn’t too far down, though.”
“Joe, I can’t see very well. Another eye seems to be quitting, and my head hurts. I can’t see the mud walls any more, and I don’t want to run into them—I remember what happened to you, and I could never dig what’s left of this machine out if I got buried—my light doesn’t show anything—Joe, what can I do?”