the top."

I smiled.

"That is the least of our troubles, Xodar," I replied. "I will
guarantee to scale the wall and take you with me, if you will help with
your knowledge of the customs here to appoint the best time for the
attempt, and guide me to the shaft that lets from the dome of this
abysmal sea to the light of God's pure air above."

"Night time is the best and offers the only slender chance we have, for
then men sleep, and only a dozing watch nods in the tops of the
battleships. No watch is kept upon the cruisers and smaller craft.
The watchers upon the larger vessels see to all about them. It is
night now."

"But," I exclaimed, "it is not dark! How can it be night, then?"

He smiled.

"You forget," he said, "that we are far below ground. The light of the
sun never penetrates here. There are no moons and no stars reflected
in the bosom of Omean. The phosphorescent light you now see pervading
this great subterranean vault emanates from the rocks that form its
dome; it is always thus upon Omean, just as the billows are always as
you see them--rolling, ever rolling over a windless sea.

"At the appointed hour of night upon the world above, the men whose
duties hold them here sleep, but the light is ever the same."

"It will make escape more difficult," I said, and then I shrugged my
shoulders; for what, pray, is the pleasure of doing an easy thing?

"Let us sleep on it to-night," said Xodar. "A plan may come with our
awakening."

So we threw ourselves upon the hard stone floor of our prison and slept
the sleep of tired men.

CHAPTER XI

WHEN HELL BROKE LOOSE

Early the next morning Xodar and I commenced work upon our plans for
escape. First I had him sketch upon the stone floor of our cell as
accurate a map of the south polar regions as was possible with the
crude instruments at our disposal--a buckle from my harness, and the
sharp edge of the wondrous gem I had taken from Sator Throg.

From this I computed the general direction of Helium and the distance
at which it lay from the opening which led to Omean.

Then I had him draw a map of Omean, indicating plainly the position of
Shador and of the opening in the dome which led to the outer world.

These I studied until they were indelibly imprinted in my memory. From
Xodar I learned the duties and customs of the guards who patrolled
Shador. It seemed that during the hours set aside for sleep only one
man was on duty at a time