When they got back they found Murgatroyd pacing up and down the floor of the deck-chamber, looking about him with serious eyes, but betraying no other visible sign of anxiety.

The _Astronef_ was at once his home and his idol, and, as Redgrave had said, even his own direct orders would hardly have induced him to leave her even in a world in which there was not a living human being to dispute possession of her.
When they had resumed their ordinary clothing the _Astronef_ rose from the surface of the plain, crossed the encircling wall at the height of a few hundred feet, and made her way at a speed of about fifty miles an hour towards the regions of the South Pole.
Behind them to the north-west they could see from their elevation of nearly thirty thousand feet the vast expanse of the Sea of Clouds.
Dotted here and there were the shining points and ridges of light marking the peaks and crater-walls which the rays of the rising sun had already touched.

Before them and to the right and left rose a vast maze of ragged, splintery peaks and huge ramparts of mountain-walls enclosing plains so far below their summits that the light of neither sun nor earth ever reached them.
By directing the force exerted by what might now be called the propelling part of the engines against the mountain masses which they crossed to right and left and behind, Redgrave was able to take a zigzag course that carried them over many of the walled plains which were wholly or partially lit up by the sun, and in nearly all of the deepest their telescopes revealed something like what they had found within the crater of Tycho.

At length, pointing to a gigantic circle of white light fringing an abyss of utter darkness, he said: "There is Newton, the greatest mystery of the moon.

Those inner walls are twenty-four thousand feet high; that means that the bottom, which has never been seen by human eyes, is about five thousand feet below the surface of the moon.