rives all its motion from the initial effort, and
consequently slows down as it rises against the earth's attraction,
until it begins again to quicken under the gravitation of the moon.
Hence his voyage to our satellite occupied four days. As we could
maintain the velocity of the car, however, we should accomplish the
distance in thirteen hours at a speed of five miles a second, and more
or less in proportion."

_G_. "About as long as the journey from London to Aberdeen by rail. What
about Mars or Venus?"

_I_. "At the same speed we should cover the 36,000,000 miles to these
planets in 2,000 hours, or 84 days, that is, about three months. With a
speed of ten miles a second, which is not impossible, we could reach
them in six weeks."

_G_. "One could scarcely go round the world in the same time. But,
having got to a planet, how are you going to land on it? Are you not
afraid you will be dissipated like a meteorite by the intense heat of
friction with the planet's atmosphere, or else be smashed to atoms by
the shock?"

_I_. "We might steer by the stars to a point on the planet's orbit,
mathematically fixed in advance, and wait there until it comes up. The
atmosphere of the approaching planet would act as a kind of buffer, and
the fall of the car could be further checked by our means of recoil, and
also by a large parachute. We should probably be able to descend quite
slowly to the surface in this way without damage; but in case of peril,
we could have small parachutes in readiness as life-buoys, and leap from
the car when it was nearing the ground."

_G_. "I presume you are taking into account the velocity of the planet
in its orbit? That of the earth is 18 miles a second, or a hundred times
faster than a rifle bullet; that of Venus, which is nearer the sun, is a
few miles more; and that of Mars, which is further from the sun, is
rather less."

_I_. "For that reason the more distant planets would be preferable to
land on. Uranus, for instance, has an orbital velocity of four miles a
second, and his gravity is about three-fourths that of the earth.
Moreover, his axis lies almost exactly on the plane of the ecliptic, so
that we could choose a waiting place on his orbit where the line of his
axis lay in the direction of his motion, and simply descend on one of
his poles, at which the stationary atmosphere would not whirl the car,
and where we might also profit by an ascending current of air. The
attraction of the sun