of grim ferocity.

As we advanced we found a well-proportioned tunnel cut from the
solid cliff. Its walls rose some twenty feet above the floor,
which was about five feet in width. The roof was arched. We had
no means of making a light, and so groped our way slowly into the
ever-increasing darkness, Tars Tarkas keeping in touch with one
wall while I felt along the other, while, to prevent our wandering
into diverging branches and becoming separated or lost in some
intricate and labyrinthine maze, we clasped hands.

How far we traversed the tunnel in this manner I do not know,
but presently we came to an obstruction which blocked our further
progress. It seemed more like a partition than a sudden ending of
the cave, for it was constructed not of the material of the cliff,
but of something which felt like very hard wood.

Silently I groped over its surface with my hands, and presently
was rewarded by the feel of the button which as commonly denotes
a door on Mars as does a door knob on Earth.

Gently pressing it, I had the satisfaction of feeling the door slowly
give before me, and in another instant we were looking into a dimly
lighted apartment, which, so far as we could see, was unoccupied.

Without more ado I swung the door wide open and, followed by the
huge Thark, stepped into the chamber. As we stood for a moment in
silence gazing about the room a slight noise behind caused me to
turn quickly, when, to my astonishment, I saw the door close with
a sharp click as though by an unseen hand.