st
the walls of the lofty, vaulted chamber in which the adventurers found
themselves, after traversing a narrow passage leading inward from the
causeway.

The walls of this chamber, which must have been fully thirty feet in
height at its greatest altitude, were formed of the soft rock, out of
which it had been excavated apparently uncounted ages before. They
were daubed with grotesque figures in faded, but still discernible,
colors. Most of these figures had to do with scenes of violence, and
in almost all of them the figure of what appeared to be an enormous
rattlesnake, with human head and arms, predominated.

Among the mural decorations were some that puzzled the professor
considerably. They were crude drawings of men in what appeared to be
intended for boats. The professor found these inexplicable. The very
idea of boats in that arid spot seemed absurdly out of place. Why,
then, should the mesa-dwellers have depicted them?

Light was furnished to the chamber by an irregularly shaped hole in the
roof above. Although there was plenty of illumination, it had yet been
some moments before the adventurers, coming out of the brilliant
sunlight outside, grew used enough to the gloom to make out their
surroundings. When they did so, the first words uttered were those of
the professor recorded above.

Like some queer, long-legged bird, the man of science, with a giant
magnifying glass held up to his eye, sped hither and thither on his
long, angular limbs, inspecting minutely the drawings and crude
attempts at decoration. Already he had out his tape-measure and
sketch-book, making observations and recording measurements.
Presently, however, he recalled himself from the first heat of his
enthusiasm.

"After all," he said, "we shall have plenty of time in which to explore
this chamber, which seems to have been used as a council hall. Let us
examine the remainder of this remarkable place."

"You may well call it that, perfusser," grunted Pete. "It's remarkable
fer the dust thet's in it, if nothing else. But what I'd like to
know," he added to himself, "is jes' whar the owners of them footsteps
vanished themselves to."

Which brings us to a remarkable discovery, made a few moments before
our party had entered the "Council Hall," as the professor called it.

As you may imagine, they had traced the footsteps with some care,
hoping to come upon a solution of the mystery of their origin. Picture
their astonishm