The Project Gutenberg EBook of The Green World, by Hal Clement This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org/license Title: The Green World Author: Hal Clement Release Date: February 25, 2020 [EBook #61509] Language: English Character set encoding: ASCII *** START OF THIS PROJECT GUTENBERG EBOOK THE GREEN WORLD *** Produced by Greg Weeks, Mary Meehan and the Online Distributed Proofreading Team at http://www.pgdp.net THE GREEN WORLD BY HAL CLEMENT The planet was an enigma—and its solution was death! [Transcriber's Note: This etext was produced from Worlds of If Science Fiction, May 1963. Extensive research did not uncover any evidence that the U.S. copyright on this publication was renewed.] I A zoo can be a rather depressing place, or it can be a lot of fun, or it can be so dull as to make the mind wander elsewhere in self-defense. In fairness to Emeraude, Robin Lampert had to concede that this one was not quite in the last group. He had been able to keep his attention on the exhibits. This was, in a way, surprising; for while a frontier town has a perfect right to construct and maintain a zoo if it wishes, one can hardly expect such a place to do a very good job. The present example was, it must be admitted, not too good. The exhibits were in fairly ordinary cages—barred for the larger creatures, glassed for the smaller ones. No particular attempt had been made to imitate natural surroundings. The place looked as artificial as bare concrete and iron could make it. To a person used to the luxuries provided their captive animals by the great cities of Earth and her sister planets, the environment might have been a gloomy one. Lampert did not feel that way. He had no particular standards of what a zoo should be, and he would probably have considered attempts at reproduction of natural habitat a distracting waste of time. He was not a biologist, and had only one reason for visiting the Emeraude zoo; the guide had insisted upon it. There was, of course, some justice in the demand. A man who was taking on the responsibility of caring for Lampert and his friends in the jungles of Viridis had a right to require that his charges know what they were facing. Lampert wanted to know, himself; so he had read conscientiously every placard on every cage he had been able to find. These had not been particularly informative, except in one or two cases. Most of the facts had been obvious from a look at the cages' inhabitants. Even a geophysicist could tell that the Felodon, for example, was carnivorous—after one of the creatures had bared a rather startling set of fangs by yawning in his face. The placard had told little more. Less, in fact, than McLaughlin had already said about the beasts. On the other hand, it had been distinctly informative to read that a small, salamanderlike thing in one of the glass-fronted cages was as poisonous as the most dangerous of Terrestrial snakes. There had been nothing in its appearance to betray the fact. It was at this point, in fact, that Lampert began really to awaken to what he was doing. He was aroused all the way by McLaughlin's explanation of a number which appeared on a good many of the placards. Lampert had noticed it already. The number was always, it seemed, different, though always in the same place, and bore signs of much repainting. It bore no relationship to any classification scheme that Lampert knew, and neither of the paleontologists could enlighten him. Eventually he turned to McLaughlin and asked—not expecting a useful answer, since the man was a guide rather than a naturalist. However, the tall man gave a faint smile and replied without hesitation. "That's just the number of human deaths known to have been caused by that animal this year." It did not comfort Lampert too greatly to learn that the year used was that of Viridis, some seventeen times as long as that of Earth. For the Felodon the number stood at twelve. This was not very much when compared to the annual losses from tigers in India during the nineteenth century. But this reflection was not particularly consoling. The human population of Viridis was so very small compared to that of India. Lampert examined the creature thoughtfully. It was of moderate size as carnivores went—some four feet long without the tail—and looked rather harmless as long as it kept its mouth shut. It was lying in the center of the cage, so it was difficult to judge the length of its legs. It showed no trace of the tendency displayed by many captive animals, of lying against a wall or in a corner when relaxed; and there was none of the restless pacing so characteristic of Earth's big cats under similar circumstances. It simply lay and stared back at Lampert, so steadily that he never was sure whether or not the cold eyes were provided with lids. "I never liked reptiles back home, but I think I like these creatures less." The voice of Mitsuitei, the little archaeologist, cut into Lampert's reverie. "Don't let Hans or Ndomi hear you mention them in the same breath with reptiles," he answered. "Well, I'm not fond of frogs, either." "I'm afraid that wouldn't make them much happier. These are not even amphibians." "They certainly are. I've been told that they lay eggs in water and have a tadpole stage—" "I should have said they aren't Amphibians with a capital A. That is, they don't belong to the order Amphibia, since they are not genetically related to the corresponding order on Earth, as far as we know. Sulewayo gets quite peeved at people who try to lump terrestrial and extraterrestrial creatures in the same order. I believe that whoever decides things for biologists has decreed that on Viridis the dominant order is to be called Amphibids. It's a quibble, if you like. But I can see why they insist on it." "Mph. So can I. Even now you sometimes run into people who go to great length to make you admit that there are pyramids both in Egypt and Mexico—and for that matter on Regulus Six—and infer from that that their makers had something in the way of common culture. I say these things are amphibians, without the Capital A, because they are at home both on land and in water. And a dictionary would back me up. I don't insist that they're related to those of Earth —any more than a Mayan pyramid has anything but geometry in common with an Egyptian one." "But I've heard—" "I'm sure you have, but it's a sore subject. I'll be open-minded if you like and admit that some Egyptian may have been blown across the Atlantic and taught architecture to the Americans, but I don't regard it as proved. What was that remark of yours—'as far as we know'—in connection with the ancestry of the amphibids? That's being at least as open- minded as I was, I would say." "In a way, yes. I don't think anyone has seriously suggested that these things originated on Earth. However, a puzzle we're here to investigate still exists. How there could be life forms corresponding to those which took a good half billion years to evolve elsewhere, on a planet which by geophysical evidence hasn't been solid for forty million? Someone certainly has suggested that the world was stocked from outside. But certainly it hasn't been proved. I don't think anyone has tried very hard, either. And I certainly won't, on a planet with as much radioactivity as this one." "You think that would account for high-speed evolution?" Lampert shrugged his shoulders, and began to stroll toward the next cage. "Ask the paleontologists. My opinion doesn't carry much weight." Mitsuitei nodded, started to follow the geophysicist, and then turned back to stare once more at the carnivore lying a few feet away. It stared back unblinkingly. The visit to the zoo was one of several, which continued until Lampert, Mitsuitei and the two paleontologists were able to identify each of a dozen animals which were most concerned in the death rate of Viridis. Apparently McLaughlin was not the only guide who did this. The zoo was equipped to give a "final examination" in which any creature the guide desired could be seen on a television screen from viewpoints quite different from those obtained in front of the cages. McLaughlin proved hard to satisfy. Lampert did not blame him. He knew a lot about Viridis, of course. He had not only read of it in ordinary reference material, but had done much of the laboratory work on drill cores brought from the planet. His name had been one of those attached to the report giving the probable age of the planet's crust. At that time, however, the mental picture he held had been of continent distribution, rock strata, zones of diastrophic stress and the like. The question of the appearance, or even the existence, of plants, animals and people had simply never risen to conscious level in his mind. That had changed, shortly before his arrival. The tramp spacer which had brought him and his group to Viridis had had to orbit about the world in free fall for several hours while its obsolete drive elements "cooled," and the passengers had examined the planet. Lampert, oddly enough, had been as much impressed by the night side as by the sunlit hemisphere. The latter had shown, at twenty thousand kilometers, a fairly standard land and water pattern. The most unusual thing about it had been the almost perfect uniformity of the land coloration, a light green which bespoke, or at least implied, a virtually complete covering of vegetation. By the time the ship had circled to the dark side, however, it was much closer to the surface; and Lampert would have expected to make out luminous sparks and patches of towns and cities by the hundreds. He saw just two, and was not really sure of those. For the rest, the planet was a vast, gray-black circle occulting a portion of the Milky Way. It was not absolutely black, either. Its contrast with the background of the galaxy was diminished by the glow in the upper atmosphere arising from the recombination of water molecules dissociated during the day by Beta Librae's fierce ultraviolet light. The center of the circle was darker than the edges, where the line of sight penetrated through more of the luminous gas. But even this sight, unusual as it was, did not affect Lampert as much as the lack of city lights. He had done field work in lonely, wild places before, of course; but until now he had always had the feeling of being in an island of wilderness more or less surrounded by civilization. On Viridis it was the civilized spots which formed the islands. And very small islands they were. There was no known native intelligent race, and settlements of alien races such as the men from Earth were still few and far between. So Lampert was prepared for McLaughlin's care in readying the group for its trip. He was even glad of it, though he would probably not have admitted to being at all afraid of the venture. He would simply have said that it was nice to have a guide who took his responsibilities seriously. That of course, did not mean that Lampert was intending to disavow any of his own responsibilities. He, like McLaughlin, had been keeping a careful eye on the other members of the group, looking for the signs of impatience or ill temper which could be the seeds of serious trouble if the journey were prolonged. He had come to tentative conclusions about this during the flight from Earth, but was pleased to see that, apparently, men who could stand the enforced companionship of a tramp spacer were also able to retain their senses of humor in the steam-bath environment of Viridis. Sulewayo, of course, had seemed safe from the first. A man who has spent his formative years in the Congo rain forests where his ancestors had lived for generations was ideal for this world. His sense of humor was extremely durable. Lampert suspected that it might sometimes be a little too good. Mitsuitei, the archaeologist, had once or twice appeared to resent some of the young fellow's remarks, though not to an extent where Lampert had felt the need for introducing his own personality into the matter. Krendall, nearly twice Sulewayo's age, seemed to be a check on the younger man anyway; he was a member of the same profession, and Sulewayo would have been the first to admit his respect for Krendall's work in the field. Under the circumstances, Lampert felt that the group was well matched. Whether it would be able to do the job it had undertaken was another matter. The news reports had spoken glibly of the expedition which was going to "solve the mysteries of Viridis once and for all." Lampert, like any other scientist, knew perfectly well that the solution of the present crop of mysteries about the planet would almost certainly be achieved only at the cost of creating an even greater number of new ones. Even the guide, who was admittedly no scientist, had expressed a similar opinion, though his was based on a general pessimism bred of familiarity with the planet. However, he had undertaken to get them to the sort of country they wanted; and from then on the problem solving was not his affair. The scientists, whatever may have been their feeling about matters of personal safety, were eager to start, which tended to cause rapid progress in McLaughlin's animal recognition school. Another factor tending toward the same result was that there was little in Emeraude for such men to do, except learn. The town was still small. It had a spaceport and airport, which furnished little entertainment, docks which could amuse for a while but not indefinitely, and warehouses which were completely uninteresting to geologists, paleontologists and archaeologists. There was no museum. The numerous specimens of mineral, animal, and vegetable matter collected on the planet invariably wound up on outbound spacecraft. The zoo, which the town maintained for purely practical reasons, was about the only thing that was left. In consequence, not many days passed before all four scientists were able to meet McLaughlin's requirements. Sulewayo was annoyed by the guide's addition of a short postgraduate course in edible flora and fauna, but admitted that the knowledge might well be useful. However, he made no secret of his satisfaction when McLaughlin finally announced that, as far as he was concerned, the journey could begin at any time. All four rechecked their equipment—that of Lampert was by far the bulkiest—and, everyone satisfied with the group's ability both to live and to work in the steam bath that was the world of Viridis, they watched the harbor on which Emeraude was located shrink and blend into the rest of the shoreline behind them. Within a few minutes only the restless surface of Green Bay was visible through the ever-present haze.... The jaws of the Felodon abruptly stopped moving and its forelegs straightened, bringing the fanged head up and away from the kill it had just made. If a man had been there he would neither have seen nor heard the disturbing factor, for a thunderstorm a few miles to the west was emitting an almost continuous growl and the towering trees shut out nearly all the sky. Nevertheless the beast appeared to sense something out of the ordinary. It twisted its short but supple neck ceaselessly, rocking its head from side to side to bring first one eye and tympanic membrane to bear on the jungle roof, then the other. Sometimes it froze motionless for a long moment, and a watcher would have sworn that its minute brain was struggling with a thought. If this were the case, the thought must have been both unusual and unpleasant, for under normal circumstances nothing short of overwhelming force would have driven a Felodon from its meal. Now, however, the hind legs slowly straightened and the creature came erect. For another moment it stood motionless, took a step or two away from the body, and stopped again. Abruptly, as though in defiance of some impulse, it turned back, lowered the murderously armed head and tore a huge mouthful of flesh from the carcass. Then, like a child leaving the cookie jar as its mother approaches, it leaped away into the underbrush, still swallowing. Its speed was high and it did not have far to go. The jungle thinned in a few hundred meters to the point where some sky became visible, and a short distance further the riotous plant growth vanished completely to give place to an open beach. Here the creature stopped and repeated its search of the hemisphere overhead. This time it found what it sought. Along the line of the beach, perhaps a kilometer out to sea, the thing came flying. It must have been utterly different from anything the Felodon could ever have seen, but no sign of fear appeared in the beast's demeanor. It stood on the beach, well away from the shelter of the jungle and certainly in full view from above, its head following the flying object and a fearful snarl—which might or might not have been its normal expression of hunger—giving its face an almost mammalian cast. This thing was larger by far than any flying creature the Felodon knew—incomparably larger than the Felodon itself. Its details were hard to make out through the hazy air, and would have meant little to the flesh-eater in any case. The most noticeable characteristic was the steady, whistling hum that proceeded from it. There was a suggestion of motion, too, which might have been wings or might not. Actually, the thing was little more than a dark dot against the purplish-blue sky. At the moment no sunlight was striking it directly, for it was in the shadow of the thunderhead. Perhaps this prevented the animal below from being bothered by another unusual feature it possessed, though even the appearance of this last characteristic produced no sign of fear when it finally came. This occurred shortly after the flying thing passed, while it was still quite close. It moved out of the shadow of the great cloud and, as the greenish sunlight struck it, the eyes of the watching creature were dazzled by a gleam of metal. This was certainly something it had never seen, for native metal on Viridis is just about as common as it was on Earth before men began to pry it out of its ores. Viridis has an oxygen-rich atmosphere and plenty of moisture, and pure aluminum or chromium just doesn't occur in that environment. Strange or not, however, the gleam did not appear to affect the Felodon's rudimentary sense of fear. For just an instant it paused as the flying thing hummed on into the northeast; just once it looked back toward the point in the jungle where it had left its kill—a point from which eloquent sounds were now coming, betraying the presence of carrion-eaters; just one step it took in that direction. Then it turned away as abruptly as it had from the meal a few minutes before. With the same purposeful air it had displayed on the way out of the jungle it headed down the beach in the direction taken by the flying piece of metal. Though the animal's speed was high, the humming soon faded out ahead of it. However, this did not seem to cause any inconvenience; the Felodon moved on, with a gait that might have been called a fast walk or a slow run, never hesitating, never pausing. It remained silent. Smaller creatures which might have given it a wide berth had they heard the hunting call now sprang away almost from underfoot. It paid them no heed, but continued on its way while the green sun settled into the jungle behind and to its left. The fact that its recent kill was now little more than a skeleton did not seem to bother it. Perhaps it had forgotten. II The humming was a little more noticeable in the helicopter cabin, but not much. John McLaughlin, sprawled as comfortably as his two meters of height would permit in its confines, had noticed the sound only at first; and after remarking to himself that they seemed to be building better ion turbines since he had left Earth, had permitted his thoughts to wander in other directions. These did not concern Felodons; the interest there was not, at the moment, mutual. The rather crowded cabin offered material enough for consideration. McLaughlin was not a scientist by training, but neither was he the sort of guide that might have been found in Yukon or Amazon territory a few centuries back. He did not despise people merely because they were, by his standards, greenhorns. He knew that each of the other men now sharing this cabin with him was an expert in his own field, even though none of them, in spite of his training, would have been able to survive for more than a day in the jungles of Viridis. After all, why should they have learned such an art? There were other things worth learning, and one could always hire McLaughlin if a need to visit the jungles developed. Since this particular party had done just that, they were evidently a fairly practical crew. They were not talking very much, which from the guide's viewpoint was an additional point in their favor. They already knew what they planned to do, and saw no point in repeating what had already been said. Of course, if they should fail to find the area they were seeking, there would be talk—all of it aimed at McLaughlin; but he had no fear on that score. There were few enough mountains on Viridis, and of those few by far the greater number were volcanic cinder cones. When these scientists had specified a region of tilted-block or folded mountains, the guide had been more than dubious at first. It had taken him time to recall that there was a small area meeting these specifications less than fifteen hundred miles from the spaceport at Emeraude. He was not himself a geologist, but pictures and diagrams had been used freely in explaining to him just what was wanted, and he was quite certain that the party would be satisfied with what he had to offer. A slight rocking in the hitherto steady motion of the helicopter roused him from this line of reverie. They were already several hours from Emeraude, and McLaughlin realized that he should have been paying more attention to the course. He straightened up in his seat and looked out. To the left and ahead was a huge thunderhead, whose satellite air currents had probably caused the variation on the helicopter's flight path. More important, there was land in sight. McLaughlin knew that the long flight across Green Bay was over. He waited, however, before saying anything. He had given the pilot full instructions as to the route before take-off, and he wanted to see whether those had been clear enough. Apparently they had. Without asking questions or even looking back at the guide, Lampert swung the aircraft from its northerly heading onto one which paralleled the shoreline, a turn of about forty-five degrees to the right, and the helicopter resumed its steady flight. McLaughlin did not relax. From now on the route was a little more difficult to follow, and there were not too many more hours of daylight. The shadowless night glow which made vision relatively easy after sunset did not lend itself to aerial navigation over a very poorly mapped world. He kept his eyes on the shoreline, watching for the landmarks he had not seen for many months—and then not from above. He did not see the Felodon which became so intensely interested in the helicopter. If he had, he would have attached little importance to the creature's presence, and he could not possibly have seen its actions in sufficient detail to catch any peculiarities in them. No one else saw the beast, either. The change in course had roused most of the party from whatever lines of thought they had been pursuing, as it had McLaughlin, and most of them were looking out the windows; but they were interested in what lay ahead, not below. Sometime soon the relative monotony of jungle and swamp should be relieved by rising ground, indicating the nearness of the mountains they sought; and the helicopter's flight altitude of some two thousand feet was low enough to permit any significant rise of terrain to be visible. Sulewayo, the younger paleontologist, made a remark to that effect, which passed without comment. Real conversation did not start for some minutes. "As I understand it, we have one more course change before we see the mountains. Isn't there a river we have to follow for a time, String?" Lampert asked the question without looking back. "That's right," McLaughlin replied. "It runs into Green Bay from almost straight north, and about a hundred miles inland makes a turn to the east. That's general direction. It winds a lot." "It would, in country as nearly peneplaned as this," muttered Lampert under his breath. "The mountains you want start about sixty airline miles from the big bend. If you trust your gyro compass enough, you can head for them directly from the river mouth. If you have any doubt about being able to hold a line, though, follow the river. I doubt that there are any good landmarks otherwise. Of course, I've only seen the area from the surface and close to the river, but I'd be very surprised if there was anything around but the swamp-and-jungle mess we're over now." "So would I. We'll stay in sight of the river, but edge as far east as visibility lets us." The guide approved this plan with a nod, and the conversation lapsed for several minutes. The silence was finally broken once more by Sulewayo. "I hope these hills we're looking for have something of interest. This planet is the most monotonous I've seen yet. Where it isn't jungle it's swamp; and the only difference between the two is that the jungle grows higher trees." McLaughlin's face crinkled into something like a smile, and he sat up once more. "There's one other difference," he remarked. "What's that?" "In the jungle, dressed and equipped as you now are, you might live as long as a day. In the swamp, five minutes would be an optimistic estimate." Sulewayo looked down at the shorts and boots which constituted his costume, and shrugged. "I admit the point, but I don't expect to go out this way. What I actually wear and carry, beside my professional equipment, is up to you. Also, I was referring to appearances. Beta Lyrae Nine looked almost as dull as this world from above, and I'll bet it was as least as deadly when you reached the surface." McLaughlin had never visited New Sheol, and admitted it, but it took more than that to stop Sulewayo. "Actually, I was hoping that these hills didn't turn out to be so covered with soil that any fossils would be yards underground at the best. Do you recall any places where the rock strata themselves were exposed—steep cliffs, or deep stream gullies, perhaps?" "Definitely yes. The big river cuts right across the range, or else starts in it. It comes out from a canyon like that of the Colorado on Earth, though a lot less spectacular. Actually I don't know anything about the country more than a couple of miles up that canyon. I was stopped on the river by rapids, and couldn't get my amphib out on either side. For the most part there simply wasn't any shore, just cliff." "Quite a current, I suppose?" Lampert cut in. "Actually, not very much. I went swimming in worse, on Earth." "That hardly ties in with steep cliffs and a river cutting through a mountain range." McLaughlin shrugged. "You're the geologist. Look it over for yourself. Maybe you'll just have to add it to the list of things you don't understand about Viridis." "Fair enough." The pilot-commander-geophysicist nodded. "I did not mean to imply that you were not reporting accurately; but the situation you have described would be a trifle queer on more planets than Earth, I assure you. Still, with luck your cliffs will show fossils. Maybe we'll solve one problem in exchange for another. Life could be worse." "Just hope we don't solve the first one by proving that certain geophysicists have been talking through their hats," the hitherto silent Krendall remarked. "Eh?" "What would you do if we found a chunk of, say, pegmatite with radioactive inclusions that checked out at half a billion years instead of the thirty-odd million you lads have been giving us as a time scale for this mudball?" "I should check very carefully under what circumstances and in what location you found it. If necessary, I would admit that the problem had disappeared. Half a billion years would account reasonably well for the evolutionary status of this planet's life forms, though actually it took Earth a good deal longer to reach a corresponding condition. Frankly, however, I do not expect any such find. We spotted our borings rather carefully, and should have taken pretty representative samples." "I'm sure you did. If your results are right, it just means that the problem belongs to Hans and me—and String here had better find us a lot of fossils." "You'll have to find your own bones," McLaughlin replied. "I'm taking you to the sort of ground you want. A fossil would have to show its teeth in my face before I'd recognize it—and then I'd probably shoot before I realized it was dead." "All right," Sulewayo chuckled. "You take care of the quick, and Krendall and I will worry about the dead. Dr. Lampert can figure out how old the fossils are if we find any, and Take can look for stone axes." "Or automobiles, or pieces of space-drive tubes, or other artifacts," Mitsuitei answered the implied dig. "I plan to sit back and loaf, unless and until one of you lads turns up a skull that could have held more than half an ounce of brain. I am going to be very unscientific. I believe that there is nothing on this planet for an archeologist to do, and I am not going to work myself into a lather to prove myself wrong." "You've formed an opinion rather early in the game," Lampert remarked. "After all, remarkably little of this world has been explored. Why should there not be traces of occupation in unknown areas such as we are about to visit?" "Because, while most of the planet remains unexplored, a very large number of places which should have furnished traces of habitation have failed to do so. We've surveyed many spots which were, or are, ideal for cities based on ocean commerce, or market centers for what could be farm areas, or spaceports. After a while you get to a point where such finds can be predicted with some certainty. As I said, I am far from certain, and it would be most unreasonable to say I was; but in the area we are seeking, I see no reason to expect anything of interest to my profession." Lampert shrugged and brought his full attention back to the controls. The sun was slowly sinking, bringing into bolder relief the irregularities of the ground as their shadows lengthened. However, these irregularities were still few, and the jungle roof was for the most part evenly illuminated. As McLaughlin had expected, there was nothing that could be used as a landmark. In its own way, the forest was as featureless as the ocean. The pilot kept his gaze riveted ahead, in expectation of the river which the guide had told them to expect; and presently he saw it. Reflecting the color of the faintly purplish sky, it stood out fairly well against the gray-green of the jungle, once they were close enough to penetrate the ever-present haze. With McLaughlin nodding silent approval, Lampert swung the helicopter to the left and proceeded more nearly straight north, angling gradually toward the river. Now the jungle took on a little more feature, though still nothing that could be used for guidance. At fairly frequent intervals a glint of water became visible through the trees directly below them. Evidently numerous tributaries were feeding into the larger stream; but none of these could be seen from any distance. For the most part they were so narrow that the trees growing on each side met above them. "I should think that one could cover a great deal of that territory in a boat," remarked Mitsuitei, after nearly half an hour in the new direction. "You'd need an amphib," replied the guide. "A boat is all right for the main stream, but all that stuff coming in from the sides is so shallow that you'd never make progress with anything else. I've tried most of them in my own croc. Every time I've had to crawl rather than float before I was a mile from the river." "How is the ground? Swamp?" "No, it's fairly solid for the most part. It doesn't show very well yet even with the sun as low as it is, but the general ground level is pushing up slowly all along here. We'll be in sight of your mountains before too long." This declaration brought all members of the group to the windows, all five pairs of eyes covering the quadrant of vision below and ahead. The meandering river was now on their left, but just visible through the haze ahead of them was the eastward turn McLaughlin had predicted. Lampert headed a little more to the right in an attempt to cut the final corner, but the helicopter reached the winding purplish band before their goal came in sight in spite of this effort. The flyer hummed on. The bars of sunlight admitted by the side ports had been nearly horizontal when the turn to the east cut them off. They were only slightly more so when McLaughlin gave a satisfied grunt, and nodded forward. The others followed his gaze. Straight ahead, little could be seen because of the "bright spot" familiar to every flyer—the shadowless area directly opposite the sun, centered on the aircraft's own shadow. To either side, however, the promised hills rose out of the jungle to heights exceeding the present flight altitude of the helicopter. Presumably the canyon from which the river was supposed to emerge lay in their path. So, at any rate, Lampert remarked; and McLaughlin confirmed him. "I'd cruise pretty slowly from here on," the guide added. "There are a number of hills on this side of the range. Even if you're not worried about running into one of them, you may want to examine them for exposed rocks." "Mightn't it be better to find a spot to park before the sun goes down?" countered the pilot. "It might. What I said still holds, though. You haven't much chance finding one inside the canyon without quite a long search, and it will be best to stay this side of the range until sunrise. Remember my trouble in finding a beach for the amphib while I was inside." "All right. Can we land in jungle, though?" "Not unless you want to fold the blades in flight and drop the last twenty to fifty feet. Hunt for a fairly high hill. They're usually somewhat bare on top, and you'll at least have room for the rotors to swing. If you don't like that, or can't find a suitable hilltop, land on the river and tie up to the shore—but again, don't try that in the canyon. You're unlikely to find anything to tie up to." "This machine has good lights, I suppose you realize—but then, you know the planet. As far as I'm concerned, what you say goes. Are the chances of a hill equally good on either side of the river?" "Maybe a little better to the north. The ground looked higher that way when I came out of the canyon." Lampert obediently eased the flyer's course a trifle to the left, and everyone aboard watched the ground as it began to rise toward them. At first the "hills" were merely low mounds, as jungle-covered as the level ground; but very quickly these gave way to higher, steeper rises on whose tops the larger trees grew very sparsely. One of these was quickly selected after a brief, questioning glance from Lampert to the guide, and the helicopter began to descend. "We'd better take what we have now." McLaughlin amplified the nod with which he had answered the pilot. "This belt of hills is pretty narrow, and we'd be into the main range in another minute or two." "Do you know whether the other side is as abrupt, or whether—" Lampert's question was cut short by an exclamation from Mitsuitei. "Rob! Hold it a moment!" Lampert was a good pilot; the increase in rotor-blade pitch under his deft fingers brought the helicopter's descent to as nearly an instant halt as was possible to anything airborne. Not until he had also checked horizontal drift did he look in the direction the archaeologist was indicating. By then, everyone else had seen what had attracted Mitsuitei's attention. Between the hill on which Lampert had intended to land and the river were several lower eminences. These were now almost directly south of the helicopter, and every detail upon them was shown in exaggerated relief by shadows stretching to the east. It was one of these hills which Mitsuitei was examining with the utmost care. It was covered with jungle, like the rest; but a curious regularity was visible. The trees appeared, at this distance, to be of the usual species; but some of them towered over their fellows by a good thirty or forty feet. This in itself was not odd. The whole jungle was studded with such projections. However, on this hill the taller trees seemed to have been planted in orderly rows. Five solid lines of them were visible, extending roughly north and south so that their long shadows made them stand out sharply. They were separated from each other by perhaps a quarter of a mile. Running at right angles to them were other, less outstanding rows of vegetation. Lampert was not quite sure that these were not the product of his own imagination, since the trees which formed them rose little if any above the general level. The whole hilltop, however, suggested something to every man who saw it. The archaeologist was the first to give voice to the impression. "That was a city!" No one answered. Some of the scientists must have thought that he was jumping from one opinion to its direct opposite on the strength of some rather feeble evidence; but the thought went unvoiced. They simply looked—except for Sulewayo, who moved to turn a camera on the scene. "Rob! Can we land there? Now?" Lampert had anticipated this question, but could have answered it without hesitation in any case. "Sure—if you don't mind using String's method of folding the blades and falling in." The archaeologist turned to the guide. "Will it be hard to get there on foot from this hill we're heading for?" McLaughlin shrugged. "From two hours to a day, depending on undergrowth." "We have torches. We can burn our way if the vegetation is dense." "Half a day, then. You'll still have to let the steam clear pretty often. There's little wind below the trees, and the air is saturated." "Well, that place will be worth more than a day of anyone's time. Maybe tomorrow we can—" "Hold up a moment, Take!" Lampert cut in, before Mitsuitei could develop his plan further. "If you take String out to that hill before take-off tomorrow, what do the rest of us do for the day—or week—before you get back? What we'd better do is note this place, go on to the canyon, set up camp, get the fossil hunting going, and after our routine is set up and we know the more common dangers of the neighborhood, perhaps we can spare McLaughlin for a day or two so that you can look over your city—if that's what it is." Lampert's last few words banished the hurt expression from the little man's face. "What do you mean—if? What else could make a pattern like that? It must have been streets." "Or a joint system in the rock below, trapping enough water—or draining enough off—to permit superior growth along the joint lines. Or a system of tilted strata doing the same thing—" "If it's the latter, it's just the sort of thing you want, too. It should bring fossils near the surface." The pilot nodded slowly. "You do make it sound more attractive. Still, I think we'd better follow the original plan, except that I may come with you myself when we do get around to looking that hill over." He turned back to the controls and resumed their descent. Mitsuitei subsided once more to his seat. The archaeologist realized the wisdom of Lampert's decision, but did not particularly enjoy the enforced wait. His face showed the fact, until Sulewayo opened the camera he had been using and passed him the sheaf of prints on which the "city" appeared. As the young paleontologist had expected, these so occupied the little man's attention that he did not even notice the landing. The helicopter settled to the hilltop which Lampert had chosen, in the center of a quadrangle of trees growing just far enough apart to give clearance to the rotors. The sun was nearly gone. It had vanished in the haze as they dropped below flight altitude. McLaughlin knew that in all too short a time it would be as dark as Viridis ever became. The nights could be dangerous. There was quite enough light to deceive a man into thinking he could see clearly, and an inexperienced wanderer might not realize until too late that details were not really distinct and that there was no clue to direction in the shadowless glow. McLaughlin himself could use the moons, but he doubted that any other member of the party could do so. They—or their motions—took knowing. He was pleased to note that there was no general rush to the door as the great blades whistled gently to a stop. The scientists turned to him, but remained where they were. No words were spoken, but Lampert's relinquishment of command was evident. McLaughlin unfolded his length from the seat. "There are two choices," he said. "We can sleep in the 'copter, or outside. The first will be a trifle cramped, but the second will require either a double circle of charged wire or two armed guards on constant watch. With no offense meant, I doubt that anyone but myself in this group could qualify as a night guard." "Why a double circle of wire?" asked Lampert. "The wire will stop only an animal in control of its motion when it makes contact. If a Felodon were to spring from a little distance, it might not like the wire—but it could hardly stop until it reached the ground, and there should then be a similar barrier ahead of it." "We could use a lethal voltage." "Even if you want to take the risk—what is lethal to a Felodon will be equally so to a man—you'll have the insulation problem. There's always a darned good chance of rain before morning, and—" "We might as well stay inside, then. We have the electric equipment, but it will take quite a while to set it up; and it hardly seems worth the trouble for a one-night stand. As you say, it will be a little crowded here. But we've all slept under worse conditions. Would anyone rather set up the fence?" There was no answer to this question. At Lampert's direction a meal was served and eaten. Then the scientists settled down for the night, some to sleep at once, others to review plans or recheck equipment. Mitsuitei occupied himself with making careful measurements of the photographs he had been given; he was the last asleep.... Scores of miles to the southwest, the Felodon reached the river. It was no longer on the coast; some time since it had swerved inland. A casual compass check would have revealed that it was still heading straight for the now grounded helicopter. Even McLaughlin could not have told what led the creature on, familiar as he was with the animals of Viridis; but no one who had watched the thing since the flying machine had passed could have doubted its goal. Actually, it was now on the same bank of the river as the helicopter; but whatever guided it pointed across the great stream. Without hesitating, the amphibid plunged into the water. III The men were awake well before sunrise. The human body takes a long, long time to accustom its physiological cycle to a change in something as fundamental as the length of day. But they did not attempt to resume flight until the green star was once more in the sky. Mitsuitei put forth a tentative suggestion that the interval be spent in a visit to the "city" site he had seen the night before, but McLaughlin vetoed it. "Going on foot through the jungle at night is a fool's game, though I admit people sometimes get away with it. I could get you there, but even if we turned around and came back immediately there'd be a lot of time wasted. Dr. Lampert went over all that last night. Look, that hill of yours is right by the river. After we're set up in the main camp, it will be relatively easy to drop down to it. We have collapsible boats. Unless we camp above the rapids, you won't even have to fly. Even if we're farther upstream and do have to use the 'copter, the trip will take only a few minutes." Mitsuitei had agreed, though with evident reluctance. No one else had any desire to go out; there was not enough rock exposed on the hilltop to excite the paleontologists, the hill itself presented nothing unusual to Lampert's geophysical eye, and McLaughlin was in no hurry to get to work. They waited, therefore, until the "Claw"—Lampert had recalled Beta Librae's Arabic name—had risen and the skyglow been replaced by its emerald brilliance; then the journey was resumed. It took, as McLaughlin had said the night before, only a few minutes. The hill where they had slept was less than five miles from the face of the mountain range. Only the haze of the night before had prevented their seeing it. The river emerged from a canyon some fifteen hundred feet in depth, a couple of miles to the south of their eastward course line. Lampert, in hopes that the usual haze might not be too evident at this hour, climbed above the level of the cliff top to get an idea of the mountain range as a whole; but he was disappointed. For nearly an hour he cruised over the area, now several thousand feet above the western cliffs and then well below them. It slowly became evident that the range represented a single block, which had been tilted upward on the west side. The opposite slopes were very gentle, merging so gradually into the general peneplain level of the continent that it was impossible to say decisively just where the range ended. The river did originate somewhere beyond the range, cutting entirely through it, and as the guide had said, its current was not particularly swift. Lampert had much explaining to do. After all, water should have drained toward the low side of the block. "It seems evident," he summed up his ideas as they hovered once more over the western cliffs, "that the river was here before this particular bit of block tilting occurred. This planet does have some diastrophic forces left in its crust, in spite of its generally smooth nature. Apparently this just represents the end of a long period of rest, such as the earth has had several times. As a matter of fact, I have no business calling it the end of such a period; it might be fifty million years before the world will be generally mountainous again." "Why do you say again, Rob?" asked Krendall. "According to findings of your own colleagues, this planet has hardly been solid for forty million years. Could it be this flat now if it had ever been markedly mountainous in that time?" "Good point. I don't know, but would be inclined to doubt it. Well, we'll cancel the 'again' if it will make you happy. In any case the block forming this range came up slowly enough so that even this river, with its relatively low cutting power, was able to keep pace with it and not be deflected. Probably—" he glanced at Mitsuitei—"the rock of which it is made will turn out to be quite strongly jointed. It looks rather that way from above—the river course, I mean. A lot of right angle, or what were once right angle, bends." "We'd better go down and look for a camp along the river somewhere," put in Mitsuitei. "Let's start at the cliff end. Then we may wind up reasonably close to that hill—and I still want to look it over, joints or no joints." "Fair enough." Lampert eased the helicopter once more downward until they were only a few hundred feet above the jungle, moved along the cliff face until they reached the canyon, and, very cautiously, entered. His caution proved unnecessary. The air currents in no way resembled the treacherous hodge-podge he had expected, at least not over the center of the river. A steady wind was blowing into the canyon mouth, but did not seem to be eddying very much even at the numerous bends. To the archeologist's annoyance, two sets of rapids were passed before a place was reached where the bank was wide enough for a camp site. At this point a fairly large side canyon entered the main one from the north. Where its central stream joined the main river a gravelly area several acres in extent offered itself for the purposes of the scientists. Lampert brought the helicopter down on this surface. The surroundings looked promising; the cliffs facing both canyons looked reasonably accessible on foot for some distance, at least along their bases. Climbing appeared to be impracticable for the most part, as the rock walls rose sheer except for the occasional joints which Lampert had predicted; but the material was certainly sedimentary, and everyone but the guide tumbled out of the flyer with a glow in his eyes which promised a speedy scattering of the party. With some difficulty, McLaughlin got them together. A site, some twenty yards square, was selected against one of the cliffs and fenced off. The big, prefabricated sheet-metal "tent" was erected and its tiny conditioning unit installed; sleeping and cooking gear were placed inside. That completed, geologist's hammers appeared as though by magic; and McLaughlin realized that he had better do some explaining before he lost a scientist or two. Once more he called them together. "All right, gentlemen. I admit the necessary camp work has been done, and there should be nothing to keep you from your projects. Still, there are some things you had better understand. "Having canyon walls on all sides does not make this place safe. Every carnivore and poison lizard on this planet could get to us by way of the river—even the ones which...