ifficult a thing for most Earth folk.

Above him raced the long, light passenger fliers, plying, each in
its proper plane, between the numerous landing-stages for internal
passenger traffic. Landing-stages that tower high into the heavens
are for the great international passenger liners. Freighters have
other landing-stages at various lower levels, to within a couple
of hundred feet of the ground; nor dare any flier rise or drop from
one plane to another except in certain restricted districts where
horizontal traffic is forbidden.

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 slo