Ranged among the mechanisms, that lined the flier's interior, were the cabinets that held our stores and special equipment. Among these were ample stores of food in thermos-cans, kept hot thus and obviating all necessity of cooking, the tanks of compressed water, and the extra liquid-oxygen tanks. Also attached to hooks on the walls were the four space-walkers that had been constructed for us to enable us to venture outside of the flier into airless space, if necessary. These space-walkers were cylindrical metal structures seven feet or more in height and three in diameter, tapering at the top to a smooth dome in which were small vision-windows. Each held a small generator of force-vibrations, and an equally small air-renovator. There were two hollow metal jointed arms that extended from the upper part, and on entering the cylinder and closing its base-door one thrust his own arms inside those hollow metal ones. They ended in great pincer-claws that could be actuated by one's own hands inside, while the space-walker itself was moved through the void by its generated force-vibrations being shot out from a small ray-opening in the cylinder's bottom. Standing inside the hollow, ball-like polyhedron of the flier, therefore, its mechanisms and equipment extended all about and above and beneath one, attached rigidly in every case to the flier's inner surface. That equipment, those mechanisms, indeed, had taxed all the powers of the great World Government laboratories to provide in the short time that was ours, but by a miracle of effort it had been done. And now, as we four gazed up toward the great gleaming faceted thing, resting beside us there in its framework of metal girders, we knew that there remained only the last of the four great generators to be completed, and that in two days more, as Randall had said, that too would be completed and installed and the space-flier would be ready for its final tests and for the start of our great trip. Looking up at the great thing towering there beside us in the waning afternoon sunlight, I was struck with a sudden realization of the stupendousness of the task that we had set ourselves; of the thing that lay before us. "To go out in that from Earth to Neptune--_to Neptune!_--it seems impossible," I said. Marlin nodded, his hand on my shoulder. "It seems strange enough," he assented, "but to Neptune in three more days we're going, Hunt. For no other chance is there to save Earth from the doom marching upon it." "But _can_ we save it?" I exclaimed. "Can we four really hope to contend against beings who, whatever their nature, have power enough to reach across the solar system and speed our spinning sun on to its doom and ours?" Marlin looked gravely at me, and at Whitely and Randall beside me. "A chance there is--must be," he said solemnly, "even though little time now remains to us. And with that chance--with Earth's chance--in our hands, we must strike out to the last with all our power for Earth!"