An involuntary thrill of pride ran through me even as we shot in toward those great cloud-masses that encircled Neptune. Neptune! The sun's farthest world, and we four had reached it, had shot across the awful gulf that none had ever thought to span! Marlin, beside me, was gazing forward into the great cloud-layers now with the astronomical curiosity of all his career gleaming in his gray eyes, as we approached this farthest of our solar system's worlds. Whitely was contemplating it with his usual cool detachment, but thoughtfully. Randall's face was as eager with interest as my own must have been, and when, a little later, there came a low mounting roar of sound around our flashing space-flier, the roar of an atmosphere through which we were rushing, he uttered a low exclamation, swiftly manipulated our outside air-tester, and then turned to us. "An atmosphere to Neptune, surely enough!" he exclaimed. "About twice the pressure of Earth's, even this far out, and the air-tester shows a large percentage of water-vapor and rather larger amount of oxygen. Otherwise it seems much the same as Earth's." Marlin nodded. "We should be able to move in that," he said, "but the greater gravitation of Neptune will probably be such as to make it necessary to keep inside the space-walkers." But now the space-flier was hurtling into the outer vapor-layers, that swirled about us in white mist-masses in the pale light that came to us from the tiny, distant sun. Onward and downward through those vapor-layers, through the cloud-belts about the great planet, our space-flier shot, while we four gazed ahead and downward, now with excitement keyed to an utter tenseness. Then with sudden stunning surprise, for we had thought those cloud-layers of immense thickness, our space-flier shot out and down from them, shot down into clear air, clear atmosphere. And as it did so, from the four of us came simultaneous cries. For there in the pale, dim unEarthly light there stretched far away beneath us the surface of the planet that for so long had been our goal on our great race to save Earth from doom, the surface of great Neptune! CHAPTER VI Into Neptune's Mysteries "Metal, over all Neptune's surface!" "A metal-covered world!"