The proposition was put to McLaughlin as soon as the machine was landed. To Lampert's surprise, the guide gave a qualified approval.
"Remember," he concluded, "I don't know what lives on the cliffs. It's country I've never covered. All I'm saying is that no Viridian animal I know of could get there, except flying ones; and they're nothing to worry about, especially in the day-time. I'd like to go with you to look over the place when you take him up tomorrow, and strongly recommend that he carry a communicator as well as a weapon; but unless I see something you haven't mentioned when I do go, I would say it was all right...."
Once more the Felodon reached the river, but this time it did not cross. It was no longer heading straight for the helicopter. Hills had not altered its course, but the cliffs had. They formed a wall on its right which was too nearly vertical for its agility and strength. Even this barrier, however, had caused no visible hesitation or doubt. It had swerved, followed the base of the wall to the point where the river emerged and plunged in as promptly as it had done before. Few amphibians have ever lost the art of swimming when their larval gills vanished; the feeble current meant nothing to the Felodon.
It turned upstream and went on its way.
IV
Ndomi Sulewayo had pursued his occupation on terraces of Earth's Grand Canyon, on cliffsides of Fomalhaut Four's highest range and in badlands on the dimly lighted Antares Twelve. The physical hazards of his present position troubled him little. McLaughlin had agreed that the ledge where the paleontologist had been left was inaccessible to the larger carnivores, and had merely issued a final warning about poisonous "lizards." The primary danger, as nearly as Sulewayo could see, was that something might happen to the helicopter. He certainly could not rejoin the others on foot. He was facing a sheer wall some sixty feet high. A score of yards behind him the terrace ended in another straight drop of several hundred feet. A quarter of a mile on either side, the flat surface ended; to the west, by narrowing until the two walls became one; at the other end, it was cut off as far as he was concerned by a joint penetrating apparently the full depth of the canyon.
There were several other cracks in the wall facing him. Like those in the tributary canyon explored by Krendall and Mitsuitei, these were packed with volcanic detritus. This was hard to reconcile with the suggestion that erosion had been long at work. In such a case, the higher portions should have washed away long before the material found at the canyon bottom.
Examination at close range suggested a possible explanation. The tuff at this point was fairly well cemented. It seemed reasonable to suppose that the joints had been present before the mountains had started to rise; that a volcanic mud flow had filled them with detritus; that the new material had then been cemented by dissolved material coming from above. This would make the top levels of the tuff more resistant than those lower down, where the cementing minerals had not reached, and account for what had been seen so far.
The hypothesis also implied a plentiful supply of fossils. Volcanic mud flowing into a crack in the ground should carry plenty with it. Sulewayo set to work with a hammer, and was presently soaking with perspiration.