Along the close-cropped sward which paves the avenue ground fliers were moving in continuous lines in opposite directions. For the greater part they skimmed along the surface of the sward, soaring gracefully into the air at times to pass over a slower-going driver ahead, or at intersections, where the north and south traffic has the right of way and the east and west must rise above it. From private hangars upon many a roof top fliers were darting into the line of traffic. Gay farewells and parting admonitions mingled with the whirring of motors and the subdued noises of the city. Yet with all the swift movement and the countless thousands rushing hither and thither, the predominant suggestion was that of luxurious ease and soft noiselessness. Martians dislike harsh, discordant clamour. The only loud noises they can abide are the martial sounds of war, the clash of arms, the collision of two mighty dreadnoughts of the air. To them there is no sweeter music than this. At the intersection of two broad avenues Vas Kor descended from the street level to one of the great pneumatic stations of the city. Here he paid before a little wicket the fare to his destination with a couple of the dull, oval coins of Helium. Beyond the gatekeeper he came to a slowly moving line of what to Earthly eyes would have appeared to be conical-nosed, eight-foot projectiles for some giant gun. In slow procession the things moved in single file along a grooved track. A half dozen attendants assisted passengers to enter, or directed these carriers to their proper destination. Vas Kor approached one that was empty. Upon its nose was a dial and a pointer. He set the pointer for a certain station in Greater Helium, raised the arched lid of the thing, stepped in and lay down upon the upholstered bottom. An attendant closed the lid, which locked with a little click, and the carrier continued its slow way. Presently it switched itself automatically to another track, to enter, a moment later, one of the series of dark-mouthed tubes. The instant that its entire length was within the black aperture it sprang forward with the speed of a rifle ball. There was an instant of whizzing—a soft, though sudden, stop, and slowly the carrier emerged upon another platform, another attendant raised the lid and Vas Kor stepped out at the station beneath the centre of Greater Helium, seventy-five miles from the point at which he had embarked. Here he sought the street level, stepping immediately into a waiting ground flier. He spoke no word to the slave sitting in the driver’s seat. It was evident that he had been expected, and that the fellow had received his instructions before his coming.