that inclination is not essential, we have
astronomical proof. Venus's axis is inclined to the plane of her orbit
seventy-five degrees, so that the arctic circle comes within fifteen
degrees of the equator, and the tropics also extend to latitude
seventy-five degrees, or within fifteen degrees of the poles, producing
great extremes of heat and cold.

"Venus is made still more difficult of habitation by the fact that she
rotates on her axis in the same time that she revolves about the sun,
in the same way that the moon does about the earth, so that one side
must be perpetually frozen while the other is parched.

"In Uranus we see the axis tilted still further, so that the arctic
circle descends to the equator. The most varied climate must therefore
prevail during its year, whose length exceeds eighty-one of ours.

"The axis of Mars is inclined about twenty-eight and two thirds degrees
to the plane of its orbit; consequently its seasons must be very
similar to ours, the extremes of heat and cold being somewhat greater.

"In Jupiter we have an illustration of a planet whose axis is almost at
right angles to the plane of its orbit, being inclined but about a
degree and a half. The hypothetical inhabitants of this majestic
planet must therefore have perpetual summer at the equator, eternal
winter at the poles, and in the temperate regions everlasting spring.
On account of the straightness of the axis, however, even the polar
inhabitants--if there are any--are not oppressed by a six months'
night, for all except those at the VERY pole have a sunrise and a
sunset every ten hours--the exact day being nine hours, fifty five
minutes, and twenty-eight seconds. The warmth of the tropics is also
tempered by the high winds that must result from the rapid whirl on its
axis, every object at the equator being carried around by this at the
rate of 27,600 miles an hour, or over three thousand miles farther than
the earth's equator moves in twenty-four hours.

"The inclination of the axis of our own planet has also frequently
considerably exceeded that of Mars, and again has been but little
greater than Jupiter's at least, this is by all odds the most
reasonable explanation of the numerous Glacial periods through which
our globe has passed, and of the recurring mild spells, probably
lasting thousands of years, in which elephants, mastodons, and other
semi-tropical vertebrates roamed in Siberia, some of which died so
recently that