Below them, the surface of the moon shone like a desolate ruin in the midst of a sandy desert. Rhoda could see the entire plain which had been the scene of her adventure, and her heart beat strangely as she picked out the pinnacle and the ridge where she had given herself up for lost. Thirty or forty miles to the north, Copernicus raised its glistening cone. Again the hollows of its surrounding craters, the crevasses, the valleys glowed with weird, phosphorescent colors--reddish, sapphire, and green. The moon began to lose its metallic hardness and to gain a mellow luster that was almost friendly. Each moment, new beauties revealed themselves--vast concentric mountain chains gleaming like jewels; strange gulfs, dried-up seas, former islands, and archipelagoes; odd, luminous streaks or furrows, shining as if with snow; patches of grayish yellow, like autumn forests; great peaks, twenty thousand feet in height, their circumferences geometrically perfect, concentric circles with a dazzling world of soft, ineffable beauty--our moon! And how swiftly it was dropping away! "We're high enough up now, I think," said Bennie. "Navigate her around to the other side, where we can get our bearings." Burke slanted the tractor gradually, while Bennie watched the surface below them with a field-glass. This maneuver had to be executed with some care, for the atmospheric valve, which controlled the angle of the helium blast and insured the horizontal flight of the Ring at a fixed elevation over the surface of the earth, could not be used over the moon, devoid as it was of atmosphere. Everything had to be controlled by hand, as in the case of the first aeroplanes. "Better keep her rising a little all the time," directed Bennie, watching a crater intently. "We can't judge our elevation when we get over the dark part, and it would be bad if we had to descend without knowing what it was. That's about right. Hold her there! Now give her a touch more of the vertical force. There! The crater is getting a little smaller." The glowing surface of the moon was now sliding rapidly along below them as they circled around it. Over the Mare Tranquillitatis they passed, its gray lava-beds glistening in the sunlight like black glass or obsidian. So rapid was the play of light on its uneven crust that the surface itself seemed in motion--like water rippling in the moonlight. Then came a rough region of jumbled rocks, and beyond, in the distance, the great, gray basin of the Mare Crisium opened before them. They were now nearing the line along the lunar surface at which the sun was setting, as they could tell from the long shadows of the volcanic cones beneath them, and presently there appeared on the distant horizon a wall of blackness, where the illuminated surface ended abruptly on the inky background of the sky. Nearer and nearer came the dark curtain, studded along the edge with countless brilliant spots and points of light.