at such may be the case," I said,
"then here may we solve the mystery of the disappearance of Tardos
Mors, Jeddak of Helium, and Mors Kajak, his son, for no other spot
upon Barsoom has remained unexplored by the many expeditions and
the countless spies that have been searching for them for nearly
two years. The last word that came from them was that they sought
Carthoris, my own brave son, beyond the ice-barrier."

As we talked we had been approaching the entrance to the cave, and
as we crossed the threshold I ceased to wonder that the ancient
green enemies of the yellow men had been halted by the horrors of
that awful way.

The bones of dead men lay man high upon the broad floor of the first
cave, and over all was a putrid mush of decaying flesh, through
which the apts had beaten a hideous trail toward the entrance to
the second cave beyond.

The roof of this first apartment was low, like all that we traversed
subsequently, so that the foul odors were confined and condensed
to such an extent that they seemed to possess tangible substance.
One was almost tempted to draw his short-sword and hew his way
through in search of pure air beyond.

"Can man breathe this polluted air and live?" asked Thuvan Dihn,
choking.

"Not for long, I imagine," I replied; "so let us make haste. I
will go first, and you bring up the rear, with Woola between.
Come," and with the words I dashed forward, across the fetid mass
of putrefaction.

It was not until we had passed through seven caves of different sizes
and varying but little in the power and quality of their stenches
that we met with any physical opposition. Then, within the eighth
cave, we came upon a lair of apts.

A full score of the mighty beasts were disposed about the chamber.
Some were sleeping, while others tore at the fresh-killed carcasses
of new-brought prey, or fought among themselves in their love-making.

Here in the dim light of their subterranean home the value of
their great eyes was apparent, for these inner caves are shrouded
in perpetual gloom that is but little less than utter darkness.

To attempt to pass through the midst of that fierce herd seemed,
even to me, the height of folly, and so I proposed to Thuvan Dihn
that he return to the outer world with Woola, that the two might
find their way to civilization and come again with a sufficient
force to overcome not only the apts, but any further obstacles that
might lie between us and our goal.

"I