"Well, that crack extends four-fifths of the way up to the top; and far enough to reach the place where we noticed all those dark marks, which we believed must be windows of the many rooms or houses of the cliff dwellers. Get that, Bob?"
"Sure I do, Frank, and after your explanation I can see what you're aiming at. But where does that ragged crevice start from down here, do you think?"
Frank stepped forward. Just as if he had it all figured out, he bent down, and with his hand drew aside the bushes that grew against the base of the cliff.
"Well, I declare, there it is for a fact!" exclaimed Bob, as he saw a rough opening before him, which came almost together five feet from the ground, leaving only a dark, uneven, slanting line that crawled up the face of the cliff like the photograph of a zigzag bolt of lightning taken with a snapshot camera.
"There you are," said Frank, with a broad smile. "Unless all signs fail, here's the entrance to the mysterious Echo Cave. We have been more than lucky to find it with so little trouble."
"Just to think of it," remarked Bob, as he bent over to look up into the gap as well as he was able; "here's where the queer old Professor has been hiding for all this time, and no one any the wiser. But Frank, however in the wide world do you suppose he found out the way to get up there?"
"We would have found it sooner or later, even if Charley Moi had not seen the old Indian moving along," replied Frank, with the confidence of one who knows what he is talking about.
"Y—yes, I reckon we would, after you'd prowled around a little, and had some chance to look the ground over. Then you believe he must have found the presence of those windows looking out of the cliff just like we did; by using a powerful glass? And, thinking that here was the very place for him to hide and study, he set about looking for the road up, and found it, very likely."
"He did it by using common sense, and applying all he knew about the ways of these people of the long ago," replied Frank. "And you can see that if he chose, he could have thrown that bottle out of one of the openings up there, so that it would drop in the passing current of the Colorado, to be carried down-stream until somebody saw it; and finding the message to my father, sent or carried it to Circle Ranch."
"Well," observed Bob, with a gleam in his eye, "now that we've found a way to get up to Echo Cave, have we the nerve to start in?"[Contents]