. I shouldn't be at all surprised if we found
something interesting on them. You know they're quite little worlds of
themselves. They're all bigger than our moon, except Europa. Ganymede,
in fact, is two-thirds bigger than Mercury, and if old Jupiter is still
in a state of fiery incandescence there's no reason why we shouldn't
find on Ganymede or one of the others the same state of things that
existed on our moon when the Earth was blazing hot."

"I shouldn't wonder," said Zaidie; "I've often heard my father say that
that was probably what happened. It's all very marvellous, isn't it?
death in one place, life in another, all beginnings and endings, and yet
no actual beginning or end of anything anywhere. That's eternity, I
suppose."

"It's just about as near as the finite intellect can get to it, I should
say," replied Redgrave. "But I don't think metaphysics are much in our
line. If you've finished we may as well go and have a look at the
realities."

"Which the metaphysicians," laughed Zaidie as she rose, "would tell you
are not realities at all, or only realities so far as you can think
about them. 'Thinks,' in short, instead of real things. But meanwhile
I've got the breakfast _things_ to put away, so you can go up on deck
and put the telescopes in order."

When she joined him a few minutes later in the deck-chamber the
three-quarter disc of Jupiter was rapidly approaching the full.

Its phases are invisible from the Earth owing to the enormous distance;
but from the deck of the _Astronef_ they had been plainly visible for
some days, and, since the huge planet turns on its axis in less than ten
hours, or with more than twice the speed of the Earth's rotation, the
phases followed each other very rapidly.

Thus at twelve o'clock noon by _Astronef_ time they might have seen a
gigantic rim of silver-blue overarching the whole vault of heaven in
front of them. By five o'clock it would be a hemisphere, and by five
minutes to ten the vast sphere would be once more shining full-orbed
upon them. By eight o'clock next morning they would find Jupiter "new"
again.

They were now falling very rapidly towards the huge planet, and, since
there is no up or down in Space, the nearer they got to it the more it
appeared to sink below them and become, as it were, the floor of the
Celestial Sphere. As the crescent approached the full they were able to
examine the mysterious bands as human observers had never examined them
befor