"Hercules," he mused, and stared out at the great circle of the moon. "The crater of Hercules! Yes, that must be it. That dark area off to one side is the Lake of Dreams; below it is the Lake of Death. Atlas! Hercules! Suffering cats, what volcanoes they must have been!" "I don't like your names," objected O'Malley. "Lake of Death! That's not so good. And I don't see any lake, and the whole Moon is wrong side up, according to your map." Chet reached for the ball-control, moved it, and swung their ship in a slow, rotary motion. The result was an apparent revolution of the Moon. "There, it's right side up," Chet laughed; "that is, if you can tell me what direction is 'up' out here in space. And, as for the names, don't let them disturb you; they don't mean anything. Some old-timer with a little three-inch telescope probably named them. The darker areas looked like seas to them. Astronomers have known better for a long time; and you and I--we're darned sure of it now." * * * * * The great sea of shadow, a darker area within the shaded portion whose only light came from the Earth, was plainly a vast expanse of blackened rock. An immense depression, like the bottom of some earlier sea, it was heaved into corrugations that Chet knew would be mountain-high at close range. Marked with the orifices of what once had been volcanoes, the floor of that Lake of Death was hundreds of miles in extent. But as for seas and lakes, there was no sign of water in the whole, vast, desolate globe. An unlikely place, Chet admitted, for the beginning of their search, and yet--those flashes of light!--the S O S! They had been real! The bow blast had been roaring for over an hour; their strong deceleration made the forward part of the ship seem "down." And down it was, too, by reason of the pull of the great globe they were approaching. But the roaring exhaust up ahead was checking their speed; Chet measured and timed the apparent growth of the Moon-disk and nodded his satisfaction at their reduced speed. "This will stop us," he said. "I didn't know but we would have to swing off, shoot past, and return under control. But we're all right, and there is the place we are looking for--the big ring of Hercules, the level floor of rock inside it. And over at one side the smaller crater--" * * * * * He was gazing entranced at the mammoth circle that had been a volcano's throat--the very one he had seen flashed on the screen. He moved the control to open a side exhaust and change their direction of fall. He was still staring, with emotions too overwhelming for words, and Spud O'Malley was silent beside him, as the great ring spread out and became an up-thrust circle of torn, jagged mountains some thirty or more miles across and directly below.