wly said.

"That ought to stand for the Grand Canyon," remarked the boy.

The keen ears of the Moqui caught the words, although they were almost
spoken in whispers, and only intended for Bob.

He nodded violently, and Frank somehow found himself wondering whether,
after all, the shrewd Indian might not be wanting to deceive him. He may
have conceived the idea that these two white boys were the enemies of
the queer old professor; and for that reason would be careful how he
betrayed the man who trusted him.

"Listen, Moqui," said Frank, putting on a serious manner, so as to
impress the other; "we are the friends of the little-old-man who has no
hair on top of his head. We want to see him, talk with him! It means
much good to him. He will be glad if you help us find him. Do you
understand that?"

The Indian's black eyes roved from one to the other of those bright
young faces. Apparently he would be foolish to suspect even for a minute
that the two lads could have any evil design in their minds.

Still, the crafty look on his brown face grew more intense.

"He has some good reason for refusing to accommodate us, I'm afraid,"
Bob said just then, as if he too had read the signs of that set
countenance.

"Why don't you answer me, Moqui?" Frank insisted, bent on knowing the
worst. "We are on the way now to find the man who gave you this letter
that talks. We have some good news for him. And you can help us if you
will only tell in what part of the Grand Canyon Echo Cave lies."

The Indian seemed to ponder. Evidently his mind worked slowly, when it
tried to grapple with secrets. But one thing he knew, and this must be
some solemn promise he had made the man of science, never under any
conditions to betray his hiding-place to a living soul.

"No can say; in canyon where picture rocks lie; that all," he finally
declared, and Frank knew Indians well enough to feel sure that no
torture could be painful enough to induce Havasupai to betray one he
believed his friend, and whose magic talking paper he carried inside his
shirt, to prove his good character.

"That settles it, Bob, I'm afraid," he remarked to his chum, who had
been listening eagerly to all that was being said. "You might try all
sorts of terrible things and he wouldn't whisper a word, even if he
believed all we told him."

"That's tough," observed Bob; "but anyhow, we've got something out of it
all, because we know now that the silly old professor must be hi