umor, he was
treating his friends like annoying strangers.

"You can't land in Canada," Bill ventured, as they pulled up at the
gate of the airport.

"Like hell I can't! You watch my smoke, and let any bloody Canuck up
there try and stop me!"

He was lifting a small black case from the luggage carrier of the car
as he replied. Bart silenced the airman with a look.

* * * * *

When they had taken off and were well under way, Van opened his black
case and set a vacuum-tube apparatus in operation. They were nearing
the fringe of the glowing sea of red that was the vast blanket of moon
weed. It now extended to within a few miles of Baltimore and stretched
northward as far as the eye could see.

"It was a cinch," Van was explaining. "When I first saw that the
growth slowed up under the arc-lights at Tomkins Cove it gave me the
glimmering of an idea. Then, on the following day, when we learned
that the weed spread more slowly in sunlight, I was convinced. The
stuff is dormant on the moon, you know."

"Why?" Bart asked breathlessly.

"Because there is no atmosphere surrounding the moon, and the sun's
rays are not filtered before they reach its surface as they are here.
The invisible rays, ultra-violet and such, are present in full
proportion. And the moon weed can not flourish when subjected to light
of the higher frequencies. It died out when the moon lost its
atmosphere, and only revived on being brought to earth--probably a
million times more prolific in our dense and damp atmosphere and rich
soil. The thing's a cinch to dope out."

"Yeah!" Bart commented drily. Van was now talking and he could have
bitten off his tongue for interrupting him.

This machine of Van's was a generator of invisible light in the
ultra-indigo range, Van explained. You couldn't see its powerful beam,
but they had proved in the laboratory that it was certain doom to the
moon weed. They had grown the stuff from seed in steel cages, and
played with it until they were all satisfied. Now would come the final
test. Ten thousand planes were being equipped with the new generator,
which was merely an adaptation of standard directional television
transmitters, and to-night these would start out to fight the weed. It
was a cinch!

* * * * *

Beneath them the red cauldron seethed and tossed as they sped
northward; the crimson blanket of death that was steadily covering the
country.