egan to take form, outlined by the trailing streaks of
gray. It began to be more definitely traced by interlinings. An aerial
lattice spread about a portion of a six-mile hemisphere. The top was
fifteen thousand feet above the rocket-ship, twenty-five thousand feet
from sea-level, as high as Mount Everest itself.

Tiny motes hovered even there, where the smallest of visible specks
was a ten-man cruiser. And one of the biggest of the aircraft came
gingerly up to the very inner edge of the lattice-work of fog and hung
motionless, holding itself aloft by powerful helicopter screws. Men
were working from a trailing stage--scientists examining the barrier
even hexynitrate would not break down.

* * * * *

Thorn set to work. He had come toilsomely to the neighborhood of the
rocket-ship because he would have to do visual signaling, and there
was no time to lose. The dome of force was transparent. The air fleet
would be trying to communicate through it with the Martians they
believed were in the rocket-ship. Sunlight reflected from a polished
canteen would attract attention instantly from a spot near the red
monster, while elsewhere it might not be observed for a long time.
But, trying every radio wave-band, and every system of visual
signaling, and watching and testing for a reply, Thorn's signal ought
to be picked up instantly.

He handed his pocket speech-light receptor to Sylva. It is standard
equipment for all flying personnel, so they may receive non-broadcast
orders from flight leaders. He pointed to a ten-man cruiser from
which shone the queer electric-blue glow of a speech-light.

"Listen in on that," he commanded. "I'm going to call them. Tell me
when they answer."

He began to flash dots and dashes in that quaintly archaic telegraph
alphabet Watch fliers are still required to learn. It was the Watch
code call, sent over and over again.

"They're trying to make the Martians understand," said Sylva
unsteadily with the speech-light receiver at her ear.

* * * * *

Flash--flash--flash.... Thorn kept on grimly. The canteen top was
slightly convex, so the sunlight-beam would spread. Accuracy was not
needed, therefore. He covered and uncovered it, and covered and
uncovered it....

"They answered!" said Sylva eagerly. "They said 'Thorn Hard report at
once!'"

There was a hissing, roaring noise over the hillside, where the red
rocket-ship lay. Thorn