And she turned and stepped to the middle of the street, where Billie
had already marked a large number of flying-machines. In fact, the
space from curb to curb was practically filled with them, all neatly
parked.

Without exception they were ornithopters; that is, machines built on
the bird-wing principle, sustaining themselves by a flapping motion
rather than by air-pressure due to a propeller. Their size varied
from one-seater affairs of very small size to craft large enough to
hold a score. Most were gaudily painted.

The surgeon's own machine was a two-seater, small but powerful in
design. She stepped up a short ladder into a comfortable cockpit,
provided with a folding top, which at that time was laid back out of
the way. She proceeded to adjust various levers and hand-wheels,
glanced at certain dials, touched a button, and immediately the
craft took flight, its wings beating the air with a dull leathery
rhythm which drowned out the faint clanking of the machinery.

A moment later the flier was high above the street. To Billie's
disappointment, the surgeon did not glance down enough to tell the
architect whether the street belonged to a city of any size.
Instead, her agent drove carefully through the traffic, which Billie
would have called dangerously dense. She remembered that she had
seen nothing but aircraft in that street; no automobiles at all.

And then the flier was rushing through the air at a lively rate.
Billie caught quick glimpses of innumerable machines, few of which
were moving in the same direction as the surgeon's.