One kilometer. Two kilometers. Time out for food, still watching from the Con room. It was much more pleasant to eat in the boat than to depend on the recycled material provided by the armor. Charley felt the same, and while there seemed no possibility of cither’s ever tasting the other’s foods, a discussion of taste and of food preparation as an art form entertained both of them for some time. Both, as it happened, knew something of each other’s culinary customs; they had attended social gatherings at the School often enough. These were normally interspecies, and it was customary for guests to bring their own refreshments. Even beings with common temperature range and using the same body-fluid base, such as the usual ammonia, were seldom similar enough chemically to share each other’s foods. Demonstrations were not unusual—a Human consuming corn on the cob or lobster, or a Kantrick everting his stomach starfish style around an artistically prepared and decorated delicacy of nearly his own size. The typical student had learned to be tolerant and even casual about sights that would have revolted a less sophisticated member of his or her race. Charley and Molly were able to be critical on a reasonably artistic level.
The robot, disappointingly, had ceased to follow a straight line. After some eight kilometers of annoyingly slow travel, it was approaching one of the conical “volcanoes”—not directly, but working its way closer in rather erratic style.
“You know, if there are eddies around the lee side of that thing, the machine is just going to spend the rest of the term going around in circles,” Molly remarked as the hill loomed closer.
“Could that be—no, we’d have found it; or rather, we’d never have had any reason to wonder where it was.”
“We’d have wondered why it wasn’t traveling, after a while,” pointed out Molly.
“I admit it was an afterthought, but I did cover the eddy problem in the program” came Joe’s voice. “If the present chase leads you to one, watch what happens after three trips around the circle.”
“I apologize, Joe,” replied Molly.
“No need; I have already made sillier mistakes—or, at least, mistakes equally attributable to inexperience, I suppose.”
“How is your map growing?”
“Convincingly. I still have no suggestion as to what may have happened in your area, however, so please don’t lose track of the machine. I would hate to have to spare another from the pattern.”
“We’re watching. I won’t need sleep for a while yet, and Charley for a lot longer. By the way, Joe, how closely has the map pattern made by this robot and its slaves matched the first?”
“So far they are indistinguishable on the map scale. I am very encouraged that the same thing is likely to happen again.”
“Do you mean encouraged or hopeful?”
“I should have used the latter term, of course. Has the robot shown its response to an eddy yet?”
“Not yet. I think there may be one soon; we’re near a bill. But something occurred to me, Joe. Wouldn’t it be possible to get some sort of idea how constant Enigma’s wind patterns are, or at least whether they change with seasons, by comparing earlier pictures of the planet? Right now, for example, the south pole is having winter and is just about free of clouds; here it’s summer and almost solidly decked over. That’s not what I would expect—maybe Jenny mentioned that to you earlier; we noticed it from Classroom.”
“She did, but it gave me no ideas. I did secure a set of early pictures, but I…”
“They let you have them?” asked Charley.
“Yes. I have not yet made sense out of them, however. Some of the rest of you should try when you have time.”
“I think we’re getting to an eddy zone,” Molly cut in tactfully.
She was right, but the watching required some waiting, as well; it took the machine fully ten minutes to get around each swing of the eddy. Molly had to remind herself that the speed of the robot had nothing to do with the speed of the wind; the latter was registered on the map by the pressure sensors in the cylinder’s skin, the former was determined by the preset program. The boat had no equipment for measuring wind directly, and unless there was something like sand or precipitate blowing around visibly there was no way of judging air currents from inside.
Molly decided, well before the third traverse of the eddy pattern, to go out and judge for herself. Charley made only a halfhearted objection; he was rather impatient for something to happen himself, and would have suggested that he be the one to go out if he had not had so much private reason to follow Molly’s lead in most matters. He settled himself more alertly at his screen while the Human re-checked her armor.
Outside, she could barely feel the wind, light as she herself was. They had grounded the boat several hundred meters from the robot to avoid complicating the winds in the latter’s neighborhood, and by the time she had walked carefully to a point perhaps fifty meters from the cylinder, it had completed its third trip around the eddy. The response that Joe had built into it was immediate and obvious. Molly reported for the Nethneen’s information.
“The robot’s lifting straight up—the wind’s so light I can’t tell whether it’s holding station for the moment or still going against the current.”
“I set it to hold” came Joe’s voice. “Integrating all the velocity contributions during the lift into the map would have been more of a complication than it was worth.”
“How high should it go?”
“Nine or ten meters. Then if it follows more than an eighth of a circle around the same eddy course it will rise again, and so on until there is a significant difference.”
“It’s about ten meters up now. I think it’s drifting more nearly straight toward the hill than it was before.” Molly paused for perhaps a minute. “Yes, it’s definitely closer—it’s over the base of the cone now. Its course is changing, I think—yes—it was making a slanting climb; now it’s heading straight toward the top. I’ll follow it.”
“Better do it in the boat,” cautioned Charley.
“No need. I can go a lot faster than its set speed on foot. Fly over the hill if you like and see where it’s going. It looks like one of Carol’s ’volcanoes’.”
Molly moved as quickly as the gravity permitted to the base of the slope and started to climb after the robot. She promptly encountered the same difficulty that Carol had laced some hours before. The hill was of loose, sandy material at its angle of repose; the stuff slid down under her, refusing to support even her few kilograms of weight. Fine powder rose around her, cutting off her vision completely until it drifted slowly away from the hill in the negligible breeze.
“It’s a crater, all right,” Charley reported from overhead. It’s not quite like the ones we got involved with before. It looks as though the hill were a heap of sand on a flat table of rock. It seems to be a little deeper inside than it is high from without, but the sand doesn’t come together the way Carol’s did. There’s a definite hole that goes down into darkness where I can’t see. If there is gas coming out, that will explain what happened to the other robot; it must have followed its program into the hole.”
“But these aren’t real volcanoes. How could wind be coming out of a hole in the ground?” asked Joe. Molly had a flash of inspiration, remembering the wind Carol had noticed in her trap.
“My ice!” she called. With no more words, she retreated a score of meters from the hill and then “ran” toward it as rapidly as her negligible weight permitted. As she reached the slope she jumped toward the robot as hard as she could.
She flew over it, spinning awkwardly, and struck the slope almost flat on her back four or five meters above the drifting cylinder. The sand here was no more able to support her than that at the base had been, and she slipped downward. Her aim had been good, however, and she met the machine within a few seconds. There might have been time for another leap if she had missed, she reflected later; she was never sure whether she would have recovered her common sense in time not to make it.