Chief
made his way directly to the clay bank, and Harry, on the opposite bank,
sat down to watch him.

It will be remembered that in making their first experiments a
considerable amount of clay had been dug out, for use in making the
brick and the retorts required for the metallurgical processes. Chief
took out a considerable quantity, and after selecting the amount which
suited his fancy, sat down and ate it. Harry was almost disgusted at the
sight, and made his way back hurriedly.

The Professor and the others were waiting.

"What do you suppose he was after? Clay! And he ate it!"

This remarkable proceeding could hardly be credited by the boys.

"Ate it!" exclaimed George. "I think you must be mistaken."

Ralph looked at Tom, and immediately answered: "That is just what they
did with that stuff we saw that the first savages had; don't you
remember, Tom?"

"I never stopped to inquire; but I know they had something that looked
like clay mud. I wonder if that was eaten by them?"

"That is not so remarkable," observed the Professor. "It is a custom in
many parts of the world."

"Where?"

"In Eastern Asia, in Java, in the Himalaya Mountains, in northern
Europe, particularly the remote regions of Sweden, in Finland, as well
as in many parts of South America, particularly in Brazil, Peru and
Bolivia, and many instances are known of this habit among the savages of
the Pacific islands."

"Can they live on the clay for any length of time?"

"Humboldt, the great geologist, relates cases of tribes in South America
which live for at least three months at a time on this substance,
without any apparent ill effect, but from all the analyses made there
does not seem to be anything nutritious in it. I am not surprised that
Chief should have a knowledge of it."

Chief returned after an hour, apparently well satisfied with himself.

Since their return Harry and George had many times thought and talked
about the cave. They debated whether or not to advise the boys of its
existence, but could not satisfy themselves of the proper course to
pursue. They were not selfishly considering the entire possession of the
treasure. In fact they were too generous for that, but the boys would
know sooner or later, and it was a question whether to disclose it now
or later on. In this dilemma they called on the Professor.

"I know just how you feel about it," was the Professor's comment, "and I
am not competent to advise you. It is yo