apparently are not interested in the satellites, and it
is no doubt due to their unintentional assistance that we have survived
as long as we have."

In the cavern at last, the three men boarded the Callistonian
space-plane and were shot up the crater's shaft. The voyage to
Callisto was uneventful, even uninteresting save at its termination.
The _Bzarvk_, coated every inch as it was with a dull, dead black,
completely absorptive outer coating, entered the thin layer of
Callisto's atmosphere in darkest night, with all rockets dead, with not
a light showing, and with no apparatus of any kind functioning. Utterly
invisible and undetectable, she dove downward, and not until she was
well below the crater's rim did the forward rockets burst into furious
life. Then the Terrestrials understood another reason for the immense
depth of those shafts other than that of protection from the detectors
of the enemy--all that distance was necessary to overcome the velocity
of their free fall without employing a negative acceleration greater
than the frail Callistonian bodies could endure. From the cavern at the
foot of the shaft, a regulation tunnel extended to the Callistonian city
of Zbardk. Portal and city were very like Wruszk, upon distant Europa,
and soon the terrestrial captain and pilot were in conference with the
Council of Callisto.

* * * * *

Months of Earthly time dragged slowly past, months during which King and
Breckenridge studied intensively the offensive and defensive systems
of Callisto without finding any particular in which they could improve
them to any considerable degree. Captain Czuv and his warplane still
survived, and it was while the Callistonian commander was visiting his
terrestrial guests, that King voiced the discontent that had long
affected both men.

"We're both tired of doing nothing, Czuv. We have been of little real
benefit, and we have decided that your ideas of us are all wrong. We are
convinced that our personal horsepower can be of vastly more use to you
than our brain-power, which doesn't amount to much. Your whole present
policy is one of hiding and sniping. I think that I know why, but I want
to be sure. Your vessels carry lots of fuel--why can the hexans outrun
you?" Thus did King put his problem.

"They can stand enormously higher accelerations than we can. The very
strongest of us loses consciousness at an acceleration of twenty-five
meters per second p