much attention.
All seemed to be overcome with grief. A terrible disaster, this loss
of the golden sphere must be!

They were out of the square and in one of the broad streets. The
fluted sides of the unpointed cones shone softly golden on all sides.
Alike in every respect were these dwellings of the people of Europa,
and strangely attractive in the light of the mother planet.

Not a word was spoken when they reached the abode of their guide. They
entered an elaborate hall and were whisked upward in an automatic
elevator. Detis ushered them into his apartment when they alighted. He
smiled gravely at their looks of wonder as they cast eyes on the maze
of apparatus before them. It was a laboratory rather than a living
room in which they stood.

Detis led them to an adjoining room where he bid them be seated. They
exchanged wondering glances as their host paced the floor vigorously
before speaking further.

"Friends," he finally blurted, "I hope you'll excuse my emotion but
the news you brought is a terrible blow to me as to all Europa. Carli,
our prince, beloved son of Cardos, was commander of the ship you
reported lost. We deeply mourn his loss."

* * * * *

Carr and Mado waited in respectful silence while their host made
effort to control his feelings.

"Now," he said, after a moment, "I can talk. You have many questions
to ask, I know. So have I. But first I must tell you that Carli's was
an expedition to your own worlds. A grave danger hangs over them and
he was sent to warn them. He has been lost. Our only space-ship
capable of making the journey also is lost. Six Martian years were
required to build it, so I fear the warning will never reach your
people. Already the time draws near."

"A grave danger?" asked Mado. "What sort of a danger?"

"War! Utter destruction! Conquest by the most warlike and ambitious
people in the solar system."

"Not the people of Europa?" asked Carr.

"Indeed not. There is another inhabited satellite of Jupiter, next
farthest from the mother planet. Ganymede, you call it. It is from
there that these conquerors are to set forth."

"Many of them?" inquired Mado.

"Two million or so. They're prepared to send an army of more than a
tenth of that number on the first expedition."

"A mere handful!" Carr was contemptuous.

"True, but they are armed with the most terrible of weapons. Your
people are utterly unprepared and, unless warned, will be dr