by Hal Clement
“Please keep this eye aimed at the rock, wherever we go.” The block spoke again.
“Right. Sherrer will see to it,” the captain responded, still without looking at the communicator. “We have you blocked up far enough to look over the rail already, and he’ll wedge the back up more if it’s needed.”
“Are you set to turn it too, or will it be easier to rotate the whole balloon?”
“Much easier, though it’ll cost a little lift. It will also make it unnecessary for you to look across the fire. Don’t worry yet, it should take half a day to burn down.”
“I never worry. I just wonder.” Jeanette Parkos, who had taken up Charles Lackland’s communication duties when health had forced him to return to Earth, was rich in comments like that. She had greatly improved Barlennan’s Spacelang in the last few thousand days, and to his surprise and in spite of her alien hearing and vocal limitations she already spoke Stennish much more fluently and clearly than her predecessor ever had.
“I’d appreciate a bit of down tilt whenever Sherrer can provide it,” she now suggested. “I can’t see up to the horizon, but I can’t see down enough for anything within a couple of miles, either. You’re a lot closer to the rock than that, according to the tracker readout, and I hope you’re closer still when it goes. I sometimes wish this thing had a wider field of view. Of course, I sometimes wish it could zoom closer too.”
Barlennan was not entirely sure that he shared the hope, though he wanted a good view himself. The Flyer was on Toorey, Mesklin’s inner moon. Her communicator would let her see what went on. The closer to the rock the better for her, but nothing could, presumably, happen to her at that distance. Barlennan lacked both the distance and the seeing equipment, and wasn’t sure which he missed more. The Flyers had assured him that there couldn’t possibly be enough energy in the propellant cell now being tested to lift the rock above it any significant distance, but the Flyers had been wrong before. He remembered vividly the Foucault pendulum fiasco; they had been certain it would give a convincing demonstration, this close to the pole, that Mesklin rather than the sky was doing the spinning. Unfortunately no one, native or alien, had been able to observe the six-inch pendulum’s plane of motion; its period was too short, and like any tuning fork its vibration had been damped out by the air a few seconds after it had been started.
They had all heard it, of course.
None of the Flyers seemed to remember that now. Barlennan had not seen an explosive in action since Lackland had used his tank’s gun so many thousands of days before, since the previous cell test had produced only the hoped-for fire fountain; but he had been told in detail how such substances were used elsewhere in the universe. These accounts, and a vivid memory of the effect of the shells Lackland had used, left him wondering why no one seemed to worry about the behavior of pieces of the rock.
Unlike Jeanette, Barlennan was a rather efficient worrier; he had not raised the question with her because he knew the aliens were extremely knowledgeable in spite of their occasional slips, and he still didn’t like to look ignorant. Answers beginning with “Of course” bothered him, especially in front of his crew, most of whom were now fairly fluent in the alien common language.
“Can you tell if it’s still burning, and how far it has to go?” the Flyer queried.
“ ’Fraid not. The fire doesn’t give any light to speak of by daylight. Too bad there’s no night now—though if there were, we’d have to plan pretty tightly so the fire would reach the cell by daylight and we could see what happens to the rock.”
“It might have helped, but since we couldn’t be sure just when the fuse would run out—well, it’s academic anyway. Even if you could control your landing point well enough you’d probably not have time to get there now, get out, cut the fuse, and start over. We’ll just wait and hope. Good work, Sher; I think I see the rock now, though I can’t be sure it’s the right one. It looks like the pictures we got before, but there are such a lot of them—rocks, I mean—this close to the edge of the plateau that I could be wrong. Too bad that fuse doesn’t smoke.”
Since cooking fires on Mesklin don’t normally smoke either and other kinds of fire are extremely rare, some minutes were used in explaining the last word; but someone remembered the Stennish for “fog” eventually, and there remained an unknowable length of suspense time when interpretation was managed. The earlier tests had given the Flyers some idea of the fuse burning rate, but the two had disagreed by over ten percent. Tension mounted, therefore, as the minutes passed.
Especially for the captain, as Bree Three was drifting toward the rock, keeping Sherrer busy and Barlennan worried. Their height should be great enough now to be pretty safe provided the aliens hadn’t overlooked anything important, but there was no way to be sure they hadn’t.
And, in fact, they had.
There was no flash; the cell salvaged from the rocket’s liftoff equipment had been worked as far under the giant boulder as the latter’s shape, the hardness of the packed ground, and Mesklinite psychology had allowed. A solid object several body lengths high and wide was not something a sane native wanted close to him, much less extending overhead, though the crew had gotten more or less used in the last hundred thousand days or so to the three-hundred-foot cliff edging the plateau. They were no longer, perhaps, wholly sane by their species’ standards.
This cell held a directional charge like the other, its individual macromolecules oriented to send all the exhaust in one direction, and had been aimed slightly downward and away from the rock this time. It therefore started by digging up an enormous cloud of dust. None of the aliens on Toorey was an explosives expert, and none had considered all the likely results of blocking what should have been a free stream of hot gas with several tons of dirt, dirt very solidly packed by Mesklin’s polar gravity.
Essentially, all the unit’s directional qualities were lost as its reaction products hit ground and were scattered randomly. It might as well have been a halfton-mass chemical bomb. The big rock did shatter. Being correct on this point did not please the captain as much as it might have; he watched tensely, knowing that if anything did go wrong there would be no time to give Hars a meaningful order.
None of the large fragments got far, and none could be seen in flight except near the tops of their trajectories, where they produced a hazy, discontinuous roof a foot or more thick and very little farther from the ground for a brief moment. Some of the much smaller stuff reached terminal velocity at other points, both upward and downward, and was visible very briefly to both Flyers and Mesklinites before hitting the surface again. Everything except for really fine dust had settled out before the sound wave reached the balloon.
This was least surprising to the natives. The quick-firing gun which had been used during the near-equatorial part of their earlier odyssey had accustomed them to the sound of explosions, but had given them no clue to the speed of pressure waves in air. Their own voices had a volume astonishing to the Flyers, and they were aware in principle that there was a delay between hooting and hearing, but they had never considered the fact quantitatively.
The real trouble was that the crew of the balloon had, at the recent briefing, been assured that nothing of this sort should happen with a directional charge; it was supposed to take several seconds to burn out, waste much less of its energy in sound, and eject its gases in essentially all one direction as the earlier one had done. That one had been aimed straight up; this had been supposed to dig.
Barlennan added another item to his mental file of Flyer fallibilities. It wasn’t really needed; the creatures had, carefully and often, made it clear that tested scientific beliefs were always tentative though usually more reliable than speculation. One could never, obviously, be sure that all the relevant data had been secured or properly considered.
“Hey! Look at that ripple!”
The alien voice was not that of Jeanette, but the captain understood it well enough. Ripples he knew about. Near the equator they
could be watched quite easily, though close to the poles they moved much too quickly to be visible.
He also did not expect them on solid ground, here or anywhere. The word “solid” was a concept which to him did not include waves, large or small. The phenomenon was very brief; it was lucky he had been looking in the right direction. It was a ripple, flickering across the ground from where much of the smashed rock still lay, in all directions. The quivering of each boulder it passed was quite visible, rapid as the passage was. He realized that the wave had started and gone under the balloon before he heard anything, but only later realized—when it was pointed out to him—that the disturbance must have traveled faster than sound. He didn’t bother to ask why even then.
The alien watchers on the satellite realized that the ripple must be a seismic wave, but none had a really good look at it just at first; it was out of the viewer field, close to the horizon as much of that was, in much less than a second. High-speed cameras had recorded it all, of course, but time was needed to play these records back, and there had not yet been time.
One of the Mesklinites, favored by a far wider field of vision, called attention to the real results of the blast.
“LOOK!” The word was a bellow in Stennish, which Jeanette didn’t bother to translate to her fellows.
“Show us! Let us look too!” she cried. “Where? What? Turn the lens!”
Sherrer was a little slow in responding, his attention being focused toward a spot at the edge of the cliff, half a mile from the balloon and from where the rock had been, and at right angles to the line of sight between these. Barlennan reached for the rotation valve lines, but the balloon was as usual slow in responding.
Starting at the point nearest the blast, the edge of the precipice was starting to crumble away and, of course, to disappear. Cracks nearly parallel to the cliff face and up to a meter from it were appearing. Others nearly perpendicular to them were also showing briefly; then the outer sides of the prisms they outlined were leaning slightly farther out and promptly vanishing. New cracks closer to the balloon than the new edge appeared immediately, outlining sections which were vanishing in turn. The disturbance was spreading in both directions from the point where it had started—the point where, Barlennan realized, the “ripple” must first have reached the cliff face.
His memory flashed to the rockfall, hundreds of miles away, where he and some of his crew had first climbed to the plateau tens of thousands of days before. That had not stretched very far along the cliff. Right now his people and vessel, the original Bree, were ten miles along the edge from this new point of collapse and should be safe—
If this one spread no farther than the other. Neither he nor any of the Flyers had been able to explain what had caused that other fall. A vertical cliff three hundred feet high and of any length at all near a Mesklin pole was unbelievable enough; the now well determined fact that it completely rimmed a continentsized area of the giant planet was worse.
The general layered appearance, which the Flyers claimed to mean sedimentary rock, was hard even for them to reconcile with an unbroken vertical cliff. There should be rock fragments—more reasonably rock powder—at the bottom. All along the bottom. Barlennan had often heard them arguing about whether the perfectly vertical joints in the cliff face implied that the plateau had been lifted or the surroundings lowered, but it had been another of the inconclusive debates which seldom held his attention for long.
No guess at what might have caused that local fall had ever come close to explaining why it had stayed local; it was easy to imagine something like a careless footfall’s (whose?) starting the break—but what could possibly have kept it from dominoing both ways the whole ten- or twelve-thousand-mile circumference of the continent? And for that matter, what had studded so many thousands of square miles of the plateau’s outer edge with boulders up to truck size, most of them lying on the surface rather than even partially buried? No one on Toorey was in the least surprised that Mesklin showed tectonic activity, and no one was too surprised that this differed in detail from anything familiar to human, Drommian, and the other researchers’ experience.
The edges of the plateau which had been seen, only a small fraction of its total circumference, did appear to be sedimentary rock, but this did nothing to make theorizing simpler.
Would the same unknown cause, or any other, operate to stop the spread of this fall? Were his crew members safe? The original Bree was ashore on the far side of the river, a little farther from the base of the cliff than the scarp itself was high. Many of those below would be away from the ship, farther still from the cliff, hunting, and presumably safe. Others, though, might well be fishing, since the river was a major source of food.
There was nothing Barlennan could do. The Flyers were still calling for attention. There was nothing they could possibly do either, but they deserved to watch. Barlennan was a responsible and reasonably fair-minded adult, and never thought of blaming them for what was happening.
The slow swiveling of the balloon finally brought the lens to face the cliff edge, not at the nearest point but well to the right, where the unaffected edge itself could still be seen. The captain stopped the rotation there. The new edge was now much closer to the balloon and—
And its growth was slowing? Surely it was slowing?
Barlennan’s people, after many thousands of days piling dirt and rocks around the alien rocket in the course of business, had a very clear concept of angle of repose. The collapse couldn’t possibly extend much farther back from the original edge than it was now getting, the captain told himself. The whole plateau would never crumble to fragments, obviously. At least, it hadn’t the other time.
But that was not the immediate problem. How far along would the disintegration extend? How safe were his other men? And how would he get his people and the stuff the Flyers wanted to recover physically, such as the inertial tracker, back to the equator if his original ship were lost? Taking the balloon across thousands of miles of ocean was ridiculous; it could carry fuel to heat its air for only a few days, in spite of Karondrasee’s endless research into different juices with maybe more effective enzymes. It could not carry the whole crew, even if the stuff wanted by the Flyers were all left behind.
“We’ve warned Dondragmer.” Jeanette’s voice caught the captains’s attention at this point in his thoughts. “No one is on the cliff side of the river. A dozen are away hunting. The ones still at the ship are getting as far from the river and the cliff as quickly as they can carry the radio.”
“Can they carry it while keeping it pointed so you can see what happens to the cliff, and tell me?” asked Barlennan.
“Don said he’d try.” That was enough for anyone who knew the mate.
“Can you see from it right now?”
“Yes. It’s pointed along the cliff in the direction the fall will come from, but the view isn’t too steady.”
“North” and “South” were not useful words this close to the pole, though the latter had been located very exactly long before.
“I’d suggest there can’t be any danger farther than, say, three times the river’s width away from the cliff foot. When they get that far, maybe they could put the set down occasionally to give us a steadier look and better pictures.”
“Maybe. But leave that decision to Dondragmer.”
“Of course. But you still have two cameras besides that one; maybe he could leave it—”
“We’ve been using all three. Dondragmer decides. I know what I’d do with my present knowledge, but he’s there.”
“All right.” There were beings, most of them non-human, on Toorey who might have argued further, but Jeanette Parkos was not one of them. She was very conscious of who was in charge on the surface, and as chief communicator realized clearly who would be blamed if any major disagreement should develop with the Mesklinites. “We’ll report to you as well as we can when the collapse gets in sight from where Dondragmer is, if it does.”
�
��Good. I’m still hoping it won’t. That other one we climbed to get up here—”
“The other one is much narrower than this one is already. Whatever caused it can’t have been as energetic.”
Another alien voice cut in. “That’s silly! Practically all the energy involved now is coming from falling rock. You have a chain reaction.”
“But that must have been true for the other fall, too!”
Barlennan turned his attention back to the still spreading collapse. He had learned long ago the futility of listening to Flyers arguing theoretical points when anything was actually going on. They got too far behind real time much too quickly. No doubt it was because they were too far away to feel personally involved. The captain was not; he turned his eyes back to the explosion site.
At least, nothing more was flying through the air. Their own climb had ceased, according to the tracker and his own eyes; the balloon had reached its ceiling, which was low because of the rapid decrease of air density with altitude. Hars’ efforts were now focused on keeping its height constant; altitude control was highly unstable. Even a slight dip caused a decrease in balloon volume, and hence a decrease in lift, which tended to make the dip deeper. It was like the hollow boat’s behavior, so many gravities to the north. Hars had developed a high skill at handling this problem; it had been he who had conceived the deflectors which gave quick control over how much hot air was actually entering the bag, and eliminated much of the control lag involved in merely feeding fuel or sprinkling meat juice on the fire.
“It’s coming.” The human voice sounded less excited than the captain felt was appropriate, but Jeanette was not, of course, in danger herself. One should make allowances.
“How close?”
“It’s just come around the point about three miles upstream.”
“How far is the debris spreading out into the river?”
