"If he doesn't move on soon I shall be compelled to ask him to go,"
said Frank in an annoyed tone to Harry. "I don't want to be
inhospitable, but we can't afford to have strangers hanging round
the camp, there is too much at stake."

Harry agreed with him and the two boys decided to tell the Portuguese
that evening as tactfully as possible that they were on a private
enterprise and could not accommodate strangers. This decision
arrived at, Frank turned to the steel strong box that was never out
of his sight and drew from it the precious map of the Moon Mountains.
Seated at the little camp-table--(the conversation just related had
taken place in the Boy Aviators' tent)--the two pored over the
document for hours. With dividers, compass and parallel rulers Frank,
who was a skilled navigator, laid out an aerial course that would
bring them, he calculated, unerringly to the spot marked by a red
cross where--so old Luther Barr declared--lay the ivory that was to
save Mr. Beasley from financial ruin and disgrace.

Frank laid his finger on the spot and exclaimed enthusiastically:

"There it is, Harry, and we are not so far from it now. In a few
days we shall know whether we are on a wild-goose chase or not."

"Why, no doubt has ever entered your head that the ivory is there?"
questioned Harry.

"Well, old fellow, you know there are others interested in this
ivory beside ourselves--Muley-Hassan for instance."