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 They waited, therefore, until the "Claw"—Lampert had recalled Beta Librae's Arabic name—had risen and the skyglow been replaced by its emerald brilliance; then the journey was resumed.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 look like land animals. Every one of them could swim under water from a point out of sight in either direction to where you are standing; and if you think he would have to come up at least once to judge your position, guess again. I don't know how they do it, and neither does anyone else; but a Felodon could submerge around the bend up there, come up behind the helicopter out of sight of any one of us and be waiting when we marched around the machine. Therefore, go armed at all times. I know you want to cover a lot of ground, and can't stick in one party; but I insist that you do not go anywhere alone. Take at least one companion. Preferably one who is not a member of your own field. If you two paleontologists are together, for example, it seems more than likely that you'll be found with your heads in the same hole in the rock. When one of you has to dig, make sure the other has his neck on a swivel. I know this will slow your work, but not as much as if the work had to wait for a new investigating team from Emeraude—or from Earth.

"You've seen most of the dangerous animals in the zoo at Emeraude, so I won't waste time describing them. Just remember that you won't always hear them coming. You'll have to use your eyes.

"All right, Dr. Lampert. You're the boss, as far as the scientific work goes. Who does what, and where?"

The geophysicist gave no sign of having detected the humor in the guide's remark, but began speaking at once.

"I should say that the main canyon upstream and the side one in the same direction should be covered first. We've already used up a good deal of today, and would waste more breaking out the boats. Ndomi and I will go up the main stream; Hans and Take can take the other. Don't hurry. If anything looks good, take the time to investigate it on the spot. Of course, if it is obviously a major job, just mark it and go on. There's no sense in one man's trying to exhume a six-foot lizard skull.

"Since this region must have been sea when the limestone was deposited, there's not much chance of land animals. However, we want as complete a chronological series as possible, so do the best you can on this level. We'll try for higher formations later. There should be plenty farther upriver, if this block is tilted the way it seems to be.

"String, perhaps you'd better go with Take and Hans. Set out when you're ready. Be back in—" he glanced automatically at the narrow strip of purplish-blue sky, then at his watch—"four hours; then we'll compare notes. After that we can either concentrate on one place or the other, or break out the boats and cross the streams, as indicated."

Twenty minutes later the parties were out of sight of each other and the helicopter. Lampert had spent the first few minutes of the walk wondering whether he had been too obvious in arranging for both the guide and Krendall to accompany the little archaeologist; but he quickly convinced himself that McLaughlin's speech had covered the arrangements pretty well.

In any case, he would probably have been distracted soon enough. The cliffs were interesting. Limestone, evidently, as expected—but rather dense, at that; maybe some barium replacing the calcium? or was the gravity different enough to destroy his judgement for such a small fragment? Probably not. He was actually using inertia more than weight in making his estimate. Anyway, the stuff was certainly a carbonate. It frothed satisfyingly under a drop of acid from Lampert's kit.

And there were fossils. Sulewayo's form was bent over a spot on the cliff face, examining minutely; but Lam............