And next as to the all-important question of atmosphere. In what
precedes, the presence of an atmosphere has been assumed, and,
fortunately, there is very convincing evidence, both visual and
spectroscopic, that Venus is well and abundantly supplied with air, by
which it is not meant that Venus's air is precisely like the mixture of
oxygen and nitrogen, with a few other gases, which we breathe and call
by that name. In fact, there are excellent reasons for thinking that the
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.
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