ill handle five thousand people
a minute. It is only very rarely, on such occasions as this, that they
are ever loaded to capacity. Some of the channels in the middle of the
city have as many as twenty tubes, so that it is always possible to go
from one end of the city to the other in less than ten minutes."

"Don't they ever jam?" asked Dorothy curiously. "I've been lost more
than once in the New York subway, and been in some perfectly frightful
jams, too--and they weren't moving ten thousand people a minute either."

"No jams ever have occurred. The tubes are perfectly smooth and
well-lighted, and all turns and intersections are rounded. The
controlling machines allow only so many persons to enter any tube--if
more should try to enter than can be carried comfortably, the surplus
passengers are slid off down a chute to the swim-ways, or sidewalks, and
may either wait a while or swim to the next intersection."

"That looks like quite a jam down there now." Seaton pointed to the
receiving pool, which was now one solid mass except for the space kept
clear by the six mighty streams of humanity-laden water.

"If the newcomers can't find room to come to the surface they'll swim
over to some other pool." Carfon shrugged indifferently. "My residence
is the fifth cubicle on the right side of this channel. Our custom
demands that you accept the hospitality of my home, if only for a moment
and only for a beaker of distilled water. Any ordinary visitor could be
received in my office, but you must enter my home."

Seaton steered the _Skylark_ carefully, surrounded as she was by a
tightly packed crowd of swimmers, to the indicated dwelling, and
anchored her so that one of the doors was close to a flight of steps
leading from the corner of the building down into the water. Carfon
stepped out, opened the door of his house, and preceded his guests
within. The room was large and square, and built of a synthetic,
non-corroding metal, as was the entire city. The walls were tastefully
decorated with striking geometrical designs in many-colored metal, and
upon the floor was a softly woven rug. Three doors leading into other
rooms could be seen, and strange pieces of furniture stood here and
there. In the center of the floor-space was a circular opening some four
feet in diameter, and there, only a few inches below the level of the
floor, was the surface of the ocean.

Carfon introduced his guests to his wife--a feminine replica of hims