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 

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