row."

"None this side," announced the searchers after a lengthy quest.

"Try the other," ordered Frank.

They did so and after a few minutes of careful scrutiny Harry
shouted that they had found a row of small holes pierced in the rock
just below where Frank stood.

"Then we have solved the mystery of the voice," exclaimed Frank.

"What do you mean?" demanded Harry.

"That it is nothing more or less than an arrangement of holes
through which, when the wind blows in a stiff puff, air is forced
with violence enough to cause the cry that disturbed us so much last
night," was the reply.

This indeed was the solution, and had the boys known it there are
many such rocks in Africa, carved out by some forgotten race, and
the weird cries that the vent-holes give out in the wind doubtless
acted as a powerful "fetish" to keep away troublesome enemies.

"No wonder the niggers down below don't come near the Moon
Mountains," said Harry, as they all buckled over the simple
explanation of the phenomenon that had caused them so much alarm.
"I wouldn't care to, myself, unless I knew just what made that cry."

"It certainly was as depressing as anything I ever heard," said