Bob spoke gloomily, as though the unsuccessful search was beginning to pall upon him a little. Boys' natures differ so much; and while the young Kentuckian had many fine qualities that his chum admired, still he was not so persistent as Frank. Nothing could ever daunt the boy from Circle Ranch. Difficulties, he believed, were only thrown in his way to bring out the better parts of his nature. The more a fellow found himself "up against it," as Frank called meeting trouble half-way, the stronger became his character. "Oh! well, now, Bob, I wouldn't say that," he answered the complaint of his chum. "Just think what tremendous progress we've been making right along. And if the very worst comes, didn't Charley Moi say that it was only a week now before he must get another stock of things to eat, and won't he have to wait at the place of meeting, for the 'learned sahib' to appear, and take them from him, as he has done so often? Why, we can be in hiding nearby, and meet the professor, even against his will." "That's so," Bob admitted, the argument proving a clincher; "and I reckon I'm a silly clown to think anything else." "No, you're only tired, after a pretty tough day, that's all," Frank declared. "When you've had a rest you'll feel better. I'm more used to this sort of thing than you are, old fellow; but all the same we must admit that we're getting the greatest view ever of this old canyon." "That's so, Frank, and it's worth all the climbing and sliding, too. But every time we've discovered signs of any of those old deserted homes of the cliff dwellers, why, we find they've been visited time and again by curious folks hoping to discover some treasure, or keepsakes of the extinct people. No chance for the old professor to hide away there." "But pretty soon we're going to discover a new batch of those caves in the face of the rock, something unknown to all other searchers. We'll find it by the aid of this same glass; and because we're looking for it, high up. In all these other cases you see, Bob, there were shelves of rock above shelves; and new ladders have been made by the guides, so that anybody with nerve could climb up and up. Now these ladders give the thing away. And I've somehow got the notion in my head that in the case of the rock dwellings where the professor is hiding himself, there is no outward sign in the shape of ladders." "But in that case, Frank, how under the sun could the old fellows ever get up to their dens, which you said must be near the top of a high cliff?" "Well, that's something we're going to find out later on, you see," replied the other, serenely. "Perhaps they had some way of lowering themselves from the top by means of a rope, or a stout, wide grape vine. Then, again, there may be some cleft in the rock farther away, that no one would notice; but which was used as a trail, running up into the cliff, and to the rock houses."