When approaching inferior conjunction--i.e., passing between the earth
and sun--Venus appears, with a telescope, in the shape of a very thin
crescent. Professor Lyman watched this crescent, becoming narrower day
after day as it approached the sun, and noticed that its extremities
gradually extended themselves beyond the limits of a semicircle, bending
to meet one another on the opposite side of the invisible disk of the
planet, until, at length, they did meet, and he beheld a complete ring
of silvery light, all that remained visible of the planet Venus! The
ring was, of course, the illuminated atmosphere of the planet refracting
the sunlight on all sides around the opaque globe.

In 1874 M. Flammarion witnessed the same phenomenon in similar
circumstances. One may well envy those who have had the good fortune to
behold this spectacle--to actually see, as it were, the air that the
inhabitants of another world are breathing and making resonant with all
the multitudinous sounds and voices that accompany intelligent life. But
perhaps some readers will prefer to think that even though an atmosphere
is there, there is no one to breathe it.

[Illustration: VENUS'S ATMOSPHERE SEEN AS A RING OF LIGHT.]

As the visibility of Venus's atmosphere is unparalleled elsewhere in the
solar system, it may be worth while to give a graphic illustration of
it. In the accompanying figure the planet is represented at three
successive points in its advance toward inferior conjunction. As it
approaches conjunction it slowly draws nearer the earth, and its
apparent diameter consequently increases. At _A_ a large part of the
luminous crescent is composed of the planet's surface reflecting the
sunshine; at _B_ the ratio of the reflecting surface to the illuminated