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............