strongest arguments for regarding Venus as a world much like ours is
based upon its remarkable similarity to the earth in size and mass,
because thus we are assured that the force of gravity is practically the
same upon the two planets, and the force of gravity governs numberless
physical phenomena of essential importance to both animal and vegetable
life. The mean diameter of the earth is 7,918 miles; that of Venus is
7,700 miles. The difference is so slight that if the two planets were
suspended side by side in the sky, at such a distance that their disks
resembled that of the full moon, the eye would notice no inequality
between them.

The mean density of Venus is about nine tenths of that of the earth, and
the force of gravity upon its surface is in the ratio of about 85 to 100
as compared to its force on the surface of the earth. A man removed to
Venus would, consequently, find himself perceptibly lighter than he was
at home, and would be able to exert his strength with considerably
greater effect than on his own planet. But the difference would amount
only to an agreeable variation from accustomed conditions, and would not
be productive of fundamental changes in the order of nature.

Being, like Mercury, nearer to the sun than the earth is, Venus also is
visible to us only in the morning or the evening sky. But her distance
from the sun, slightly exceeding 67,000,000 miles, is nearly double that
of Mercury, so that, when favorably situated, she becomes a very
conspicuous object, and, instead of being known almost exclusively by
astronomers, she is, perhaps, the most popular and most admired of all
the members of the planetary system, especially when she appears in the
charming rôle of the "evening star." As she emerges periodically from
the blinding glare of the sun's immediate neighborhood and begins to
soar, bright as an electric balloon, in the twilight, she commands all