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.

Scarcely had Vas Kor taken his seat when the flier went quickly into the fast-moving procession, turning presently from the broad and crowded avenue into a less congested street. Presently it left the thronged district behind to enter a section of small shops, where it stopped before the entrance to one which bore the sign of a dealer in foreign silks.

Vas Kor entered the low-ceiling room. A man at the far end motioned him toward an inner apartment, giving no further sign of recognition until he had passed in after the caller and closed the door.

Then he faced his visitor, saluting deferentially.

"Most noble--" he commenced, but Vas Kor silenced him with a gesture.

"No formalities," he said. "We must forget that I am aught other than your slave. If all has been as carefully carried out as it has been planned, we have no time to waste. Instead we should be upon our way to the slave market. Are you ready?"

The merchant nodded, and, turning to a great chest, produced the unemblazoned trappings of a slave. These Vas Kor immediately donned. Then the two passed from the shop through a rear door, traversed a winding alley to an avenue beyond, where they entered a flier which awaited them.

Five minutes later the merchant was leading his slave to the public market, where a great concourse of people filled the great open space in the centre of which stood the slave block.

The crowds were enormous to-day, for Carthoris, Prince of Helium, was to be the principal bidder.

One by one the masters mounted the rostrum beside the slave block upon which stood their chattels. Briefly and clearly each recounted the virtues of his particular offering.

When all were done, the major-domo of the Prince of Helium recalled to the block such as had favourably impressed him. For such he had made a fair offer.

There was little haggling as to price, and none at all when Vas