And always the great stern-blast roared; muffled by the insulated walls, its unceasing thunder came at last to be unheard. To the pilot there was neither sound nor motion. His directional sights were unswervingly upon that distant star ahead. Seemingly they were suspended, helpless and inert, in a black void. But for the occasional glowing masses of strange living substance that flashed past in this ocean of space, he must almost have believed they were motionless--a dead ship in a dead, black night. But the luminous things flashed and were gone--and their coming, strangely, was from astern; they flicked past and vanished up ahead. And, by this, Chet knew that their tremendous momentum was unchecked. Though he was using the great stern blast to slow the ship, it was driving stern-first into outer space. Nor, for twenty hours, was there a change, more than a slackening of the breathless speed with which the lights went past. Twenty hours--and then Chet knew that they were in all truth hung motionless, and he prayed that his figures that told him this were correct.... More timeless minutes, an agony of waiting--and a dimly-glowing mass that was ahead approached their bow, swung off and vanished far astern. And, with its going, Chet knew that the return trip was begun. He gave Harkness the celestial bearing marks and relinquished the helm. "Full speed ahead as you are," he ordered; "then at nineteen-forty on W.S. time, we'll cut it and ease on bow repulsion to the limit." And, despite the strangeness of their surroundings, the ceaseless, murmuring roar of the exhaust, the weird world outside, where endless space was waiting for man's exploration--despite the deadly menace that threatened, Chet dropped his head upon his outflung arms and slept. * * * * * To his sleep-drugged brain it was scarcely a moment until a hand was dragging at his shoulder. "Forty-seven hours!" the voice of Schwartzmann was saying. And: "Some navigating!" Harkness was exclaiming in flattering amazement. "Wake up, Chet! Wake up! The Dark Moon's in sight. You've hit it on the nose, old man: she isn't three points off the sights!" The bow-blast was roaring full on. Ahead of them Chet's sleepy eyes found a circle of violet; and he rubbed his eyes savagely that he might take his bearings on Sun and Earth. As it had been before, the Earth was a giant half-moon; like a mirror-sphere it shot to them across the vast distance the reflected glory of the sun. But the globe ahead was a ghostly world. Its black disk was lost in the utter blackness of space. It was a circle, marked only by the absence of star-points and by the halo of violet glow that edged it about. Chet cut down the repelling blast. He let the circle enlarge, then swung the ship end for end in mid-space that the more powerful stern exhaust might be ready to counteract the gravitational pull of the new world.