atmosphere of Venus differs from the earth's quite as much as some of
her other characteristics differ from those of our planet. But, however
it may vary from ours in constitution, the atmosphere of Venus contains
water vapor, and is exceedingly abundant. Listen to Professor Young:

"Its [Venus's] atmosphere is probably from one and a half to two times
as extensive and as dense as our own, and the spectroscope shows
evidence of the presence of water vapor in it."

And Prof. William C. Pickering, basing his statement on the result of
observations at the mountain observatory of Arequipa, says: "We may feel
reasonably certain that at the planet's [Venus's] surface the density of
its atmosphere is many times that of our own."

We do not have to depend upon the spectroscope for evidence that Venus
has a dense atmosphere, for we can, in a manner, _see_ her atmosphere,
in consequence of its refractive action upon the sunlight that strikes
into it near the edge of the planet's globe. This illumination of
Venus's atmosphere is witnessed both when she is nearly between the sun
and the earth, and when, being exactly between them, she appears in
silhouette against the solar disk. During a transit of this kind, in
1882, many observers, and the present writer was one, saw a bright
atmospheric bow edging a part of the circumference of Venus when the
planet was moving upon the face of the sun--a most beautiful and
impressive spectacle.

Even more curious is an observation made in 1866 by Prof. C.S. Lyman, of
Yale College, who, when Venus was very near the sun, saw her atmosphere
_in the form of a luminous ring_. A little fuller explanation of this
appearance may be of interest.