The Moon Colony, discovered in 1976, when Kramer, of Baltimore, first proved the practicability of mixing neon with the inert new gas, leucon, and so conquering gravitation, had proved to be just what it had been suspected of being--a desiccated, airless desolation. Nevertheless, within the depths of the craters a certain amount of the Moon's ancient atmosphere still lingered, sufficient to sustain life for the queer troglodytes, with enormous lung-boxes, who survived there, browsing like beasts upon the stunted, aloe-like vegetation. Half man, half ape, and very much unlike either, these vestiges of a species on a ruined globe had proved tractable and amenable to discipline. They had become the laborers of the convict settlement that had sprung up on the Moon. Thither all those who had opposed the establishment of the World Federation, together with all persons convicted for the fourth time of a felony, had been transported, to superintend the efforts of these dumb, unhuman Moon dwellers. For it had been discovered that the Moon craters were extraordinarily rich in gold, and gold was still the medium of exchange on Earth. To supplement the vestigial atmosphere, huge stations had been set up, which extracted the oxygen from the subterranean waters five miles below the Moon's crust, and recombined it with the nitrogen with which the surface layer was impregnated, thus creating an atmosphere which was pumped to the workers. Then a curious discovery had been made. It was impossible for human beings to exist without the addition of those elements existing in the air in minute quantities--neon, krypton, and argon. And the ships that brought the gold bars back from the Moon had conveyed these gaseous elements there. * * * * * The droning of the sixteen atomic motors grew louder, and mingled with the hum of gyroscopes. The ladder was drawn up and the port hole sealed. On the enclosed bridge Nat threw the switch of durobronze that released the non-conducting shutter which gave play to the sixteen great magnets. Swiftly the great ship shot forward into the air. The droning of the motors became a shrill whine, and then, growing too shrill for human ears to follow it, gave place to silence. Nat set the speed lever to five hundred miles an hour, the utmost that had been found possible in passing through the earth's atmosphere, owing to the resistance, which tended to heat the vessel and damage the delicate atomic engines. As soon as the ether was reached, the speed would be increased to ten or twelve thousand. That meant a twenty-two hour run to the Moon Colony--about the time usually taken.