it was moving across them. The sun poured directly upon
it, making it appear full and showing all its features. There were
small unevennesses on the surface, apparently seventy or a hundred feet
high, which were the nearest approach to mountains, and they ran in
ridges or chains. There were also unmistakable signs of volcanic
action, the craters being large compared with the size of the planet,
but shallow. They saw no signs of water, and the blackness of the
shadows convinced them there was no air. They secured two
instantaneous photographs of the little satellite as the Callisto swept
by, and resumed their inspection of Mars. They noticed red and
brownish patches on the peaks that had that morning turned white, from
which they concluded that the show had begun to melt under the warm
spring sun. This strengthened the belief they had already formed, that
on account of its twenty-seven and a half degrees inclination the
changes in temperature on Mars must be great and sudden. So interested
were they with this, that they did not at first see a large and bright
body moving rapidly on a course that converged with theirs.

"We must be ready to repel boarders," said Bearwarden, observing it for
the first time and fixing his glass upon it. "That must be Phobos."

Not ten miles off they beheld Mars's inner moon, and though their own
speed caused them to overtake and rush by it like a whirlwind, the
satellite's rapid motion in its orbit, in a course temporarily almost
parallel with theirs, served to give them a chance the better to
examine it. Here the mountain ranges were considerably more
conspicuous than on Deimos, and there were boulders and loose stones
upon their slopes, which looked as if there might at some time have
been frost and water on its surface; but it was all dry now, neither
was there any air. The evidences of volcanic action were also plainly
visible, while a noticeable flattening at the poles showed that the
little body had once rotated rapidly on its axis, though whether it did
so still they had not time to ascertain. When abreast of it they were
less than two miles distant, and they secured several instantaneous
impressions, which they put aside to develop later. As the radius of
Phobos's circle was far shorter than that of the parabolic curve they
were making, it began to draw away, and was rapidly left behind.
Applying the full apergetic force to Mars and the larger moon, they
shot away lik