e
those of his comrades who fought near by would rush to cover his escape.

The therns on their side would hasten to rescue the girl, and in an
instant the two would be swallowed in the vortex of a maelstrom of
yelling devils, hacking and hewing at one another, like fiends
incarnate.

But always, it seemed, were the black pirates of Barsoom victorious,
and the girl, brought miraculously unharmed through the conflict, borne
away into the outer darkness upon the deck of a swift flier.

Fighting similar to that which surrounded us could be heard in both
directions as far as sound carried, and Thuvia told me that the attacks
of the black pirates were usually made simultaneously along the entire
ribbon-like domain of the therns, which circles the Valley Dor on the
outer slopes of the Mountains of Otz.

As the fighting receded from our position for a moment, Thuvia turned
toward me with a question.

"Do you understand now, O Prince," she said, "why a million warriors
guard the domains of the Holy Therns by day and by night?"

"The scene you are witnessing now is but a repetition of what I have
seen enacted a score of times during the fifteen years I have been a
prisoner here. From time immemorial the black pirates of Barsoom have
preyed upon the Holy Therns.

"Yet they never carry their expeditions to a point, as one might
readily believe it was in their power to do, where the extermination of
the race of therns is threatened. It is as though they but utilized
the race as playthings, with which they satisfy their ferocious lust
for fighting; and from whom they collect toll in arms and ammunition
and in prisoners."

"Why don't they jump in and destroy these fliers?" I asked. "That
would soon put a stop to the attacks, or at least the blacks would
scarce be so bold. Why, see how perfectly unguarded they leave their
craft, as though they were lying safe in their own hangars at home."

"The therns do not dare. They tried it once, ages ago, but the next
night and for a whole moon thereafter a thousand great black
battleships circled the Mountains of Otz, pouring tons of projectiles
upon the temples, the gardens, and the courts, until every thern who
was not killed was driven for safety into the subterranean galleries.

"The therns know that they live at all only by the sufferance of the
black men. They were near to extermination that once and they will not
venture risking it again."

As she ceased talking a new