But Niltci shook his head vigorously and led on without a word. The rim cliff ended abruptly a little further on in a huge tower of stone, and, rounding it, they found themselves in a vast amphitheater, a mile deep, and a mile across a valley of illimitable depths to its opposite point. All around it the cliffs rose sheer. Surely they never came down here! Niltci had to acknowledge that much, himself, but instead of turning back to retrace their steps he grunted impetuously and led them on, following the rim into that enormous basin. “Aw, rats!--what’s the use, Niltci, you’re crazy!” exploded Sid, as both he and the Colonel balked at going any further. For answer the Indian boy pointed to a thin fissure that cleft the rim from top nearly to bottom, up near the head of the basin. It was about half a mile away. How Niltci could know that that crevice could be practicable for ascent, Sid could not conjecture, but the red men were wise in the ways of Nature, so he followed on, albeit incredulously. But he had no idea what impassable obstacle might await them to the south if they turned back. This, at least, looked possible! Arrived at it, they peered up to where the last of it ended in a broken, jagged path, showing where water had come down during the rains. For fifty feet this rose up the cliff,--an absurd trail for anything but a fly to attempt; then began the in-cutting of the fissure. Niltci started up it, amid a howl of protest from Sid and the Colonel. Like a creeping cat the Indian lad climbed steadily up until he had reached the fissure, where he turned with a whoop of triumph. “Wow! We can’t let him get away with that, Father!” chuckled Sid. “Shut your eyes and climb! Forget mother, forget your insurance, and all the rest of it--it’s the only way!--I’ll be right behind you.” The Colonel groaned, whimsically, and started up. Niltci came down again by some incredible feat of legerdemain--as they looked back upon that climb afterwards--and gave him a strong lift over the worst places, and so they all reached the bottom of the fissure. It was dark and gloomy, and it curved around a bend above, so that they had no idea how it was all going to turn out--most likely in some sheer wall, thought Sid. But the only way to get over these things was to go ahead and do them, so they climbed up into it. Part of the time Niltci was straddling both walls of it; part of the climb crawling up vertical ledges higher than his head. The curve mercifully hid from them the frightful depths below, should anyone fall. It grew better, once around it, cutting deeper and deeper into the rim wall and becoming less and less vertical. Masses of pine roots fringed it overhead, and finally their feet found a narrow bottom of yellow, crumbled rocks, which led up in a steep slant to the forest above.