Calling to Woola to follow me I stepped out upon the ledge. The
great, savage brute, agile as a cat, crept after me.

As he passed through the boat that had been occupied by Thurid and
the therns he emitted a single low growl, and when he came beside
me upon the ledge and my hand rested upon his neck I felt his short
mane bristling with anger. I think he sensed telepathically the
recent presence of an enemy, for I had made no effort to impart to
him the nature of our quest or the status of those we tracked.

This omission I now made haste to correct, and, after the manner
of green Martians with their beasts, I let him know partially by
the weird and uncanny telepathy of Barsoom and partly by word of
mouth that we were upon the trail of those who had recently occupied
the boat through which we had just passed.

A soft purr, like that of a great cat, indicated that Woola
understood, and then, with a word to him to follow, I turned to
the right along the ledge, but scarcely had I done so than I felt
his mighty fangs tugging at my leathern harness.

As I turned to discover the cause of his act he continued to pull
me steadily in the opposite direction, nor would he desist until
I had turned about and indicated that I would follow him voluntarily.

Never had I known him to be in error in a matter of tracking, so
it was with a feeling of entire security that I moved cautiously in
the huge beast's wake. Through Cimmerian darkness he moved along
the narrow ledge beside the boiling rapids.