necessity for changing the direction of the glasses. After an
hour of this interesting work, however, as it was already late at
the longitude they had left on earth, and as they knew they had
many days in space before them, they prepared to go to bed. When
ready, they had only to pull down the shades; for, as apergy was
not applied to them, but only to the Callisto, they still looked
upon the floor as down, and closed the heavy curtains to have
night or darkness. They found that the side of the Callisto
turned constantly towards the sun was becoming very warm, the
double-toughened glass windows making it like a greenhouse; but
they consoled themselves with the thought that the sun's power on
them was hourly becoming less, and they felt sure the double
walls and thick upholstery would protect them almost anywhere
within the solar system from the intense cold of space.

"We could easily have arranged," said Ayrault, for night and day
on alternate sides of the Callisto by having strips of metal
arranged spirally on the outside as on the end of an arrow.
These would have started us turning as slowly as we like, since
we passed through the atmosphere at a comparatively low rate of
speed."

"I am afraid," said Cortlandt, "the motion, however slow, would
have made us dizzy. It would be confusing to see the heavens
turning about us, and it would interfere with using the glasses."

The base and one side of the Callisto had constant sunshine,
while the other side and the dome were in the blackest night.
This dome, on account of its shape, sky windows, and the
completeness with which it could be isolated, was an ideal