nd movability to this ship of the stratosphere. How many
there were of them there was no way of knowing. They had guessed two
hundred. There might have been a thousand. It scarcely mattered.

Sitsumi's face was set in a firm mask. He, of all the "lords of the
stratosphere," seemed to possess endless courage. His example fired the
three.

"What do you plan?" asked Wang Li.

Jeter and Eyer listened with all their ears.

"We have only one weapon in this unexpected emergency," said Sitsumi
quietly. "We cannot direct the ray upward or laterally: it is not so
constructed. But we can attack with the space ship itself! And remember
that so long as our outer rind remains intact and hard we are invisible
to attackers."

Jeter and Eyer exchanged glances.

"If only we could find the way to break or soften that outer rind," said
Jeter.

"What can we do?" asked Eyer. "If it is impervious to the cold of these
heights; if it is so strong that it is impervious to the tremendous
pressure inside the globe--which must be kept at a certain degree to
maintain human life--what can we do? We tried bullets. We might as well
have used peas and pea-shooters. If our friends try bombs they will
still be unsuccessful. If only we could somehow open up the outer rind
or soften it, so that our friends could see the inner globe and reach it
with their bombs!"

Jeter's face was now dead white. His eyes were aglow with excitement.

"Tema," he whispered, "Tema, that's their vulnerability! That's what
they fear! They're scared that the outer rind may be broken--which would
spell destruction to the space ship and everybody in it."

"Including us," replied Eyer, "but, anyway--well, what's the odds? We're
only two--and with this thing destroyed the nightmare will end. Of
course there should be some way to raid the Lake Baikal area and destroy
any other ships in the making, besides ferreting out the secret of the
invisible substance and the elements of the gravity inverter. If we
somehow survive, and this ship is destroyed, that's the next thing to
do."

Jeter nodded and signaled Eyer to cease whispering.

* * * * *

They devoted their attention now to the six planes. They were coming up
in battle formation. They were in plain view and through the telescopes
it could be seen that each was armed with bombs of some kind. Useless
against the invisible space ship as matters now stood; but what would
those bombs do to