no caves in this rock."

He stopped at times for breath, and his wonder grew as he climbed and
the black mark took clearer form. At last he stood panting before it,
to stare deep into the utter blackness of a passageway beyond an
entrance of carved stone.

It was carved; there was no mistaking it! Here was a passage that
nature had never formed. He took a quick stride forward to see the
tool marks that showed on hard walls where symbols and figures of
strange design were carved. An intrusion of harder rock had formed a
roof, and they had cut in below--

"They!" He spoke the word aloud. Who were "they?"

* * * * *

He remembered the scientist who had stopped at the ranch some time
before, and he recalled enough of the talk of Aztec and Toltec and
Mayas to know that none of these old civilizations could explain the
things he saw.

"This goes way back beyond them--it must," he reasoned. And there were
pictures, long forgotten, that came to his mind to show him a vision
from the past--figures whose coppery faces shone dark above their
brilliant, colored robes--slaves, toiling and sweating to drive this
tunnel into solid rock. He was suddenly a-quiver with a feeling of the
presence of living things. His breath seemed stifled within him as he
stepped into the dark where a pencil of light from his pocket-flash
made the blackness more intense.

He tried to shake off the feeling, but an indefinable oppression was
heavy upon him; the weight of the uncounted centuries these walls had
seen filled him with strange forebodings.

His feet stumbled and scuffed over chips of stone; he steadied himself
against the wall at times as he followed the corridor that went down
and still down before him. It turned and twisted, then leveled off at
last, and Garry Connell drew himself up sharply with a quick-drawn
breath.

His flash was making a circle of light a dozen steps ahead, and showed
a litter of sharp stone fragments. And, scattered over them, a tangle
of bones shone white; one skull stood upright to stare mockingly from
hollow sockets. The sudden white of them was startling in the black
pit.

"Bones!" he said, and forced himself to disregard the echoes that
tried to shout him down; "just bones! And the old-timers that wore
them haven't been using them for thousands of years." He moved forward
with determined steps to the end of the passage that finished in solid
stone. He stopped abruptly. At