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 They waited, therefore, until the "Claw"—Lampert had recalled Beta Librae's Arabic name—had risen and the skyglow been replaced by its emerald brilliance; then the journey was resumed.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