Sidelights on Astronomy and Kindred Fields of Popular Science | Page 8

these questions science cannot as yet give a positive answer,
except in the case of the moon. Our satellite is so near us that we can
see it has no atmosphere and no water, and therefore cannot be the
abode of life like ours. The contrast of its eternal deadness with the
active life around us is great indeed. Here we have weather of so many
kinds that we never tire of talking about it. But on the moon there is no
weather at all. On our globe so many things are constantly happening
that our thousands of daily journals cannot begin to record them. But
on the dreary, rocky wastes of the moon nothing ever happens. So far
as we can determine, every stone that lies loose on its surface has lain
there through untold ages, unchanged and unmoved.
We cannot speak so confidently of the planets. The most powerful
telescopes yet made, the most powerful we can ever hope to make,

would scarcely shows us mountains, or lakes, rivers, or fields at a
distance of fifty millions of miles. Much less would they show us any
works of man. Pointed at the two nearest planets, Venus and Mars, they
whet our curiosity more than they gratify it. Especially is this the case
with Venus. Ever since the telescope was invented observers have tried
to find the time of rotation of this planet on its axis. Some have reached
one conclusion, some another, while the wisest have only doubted. The
great Herschel claimed that the planet was so enveloped in vapor or
clouds that no permanent features could be seen on its surface. The best
equipped recent observers think they see faint, shadowy patches, which
remain the same from day to day, and which show that the planet
always presents the same face to the sun, as the moon does to the earth.
Others do not accept this conclusion as proved, believing that these
patches may be nothing more than variations of light, shade, and color
caused by the reflection of the sun's light at various angles from
different parts of the planet.
There is also some mystery about the atmosphere of this planet. When
Venus passes nearly between us and the sun, her dark hemisphere is
turned towards us, her bright one being always towards the sun. But she
is not exactly on a line with the sun except on the very rare occasions of
a transit across the sun's disk. Hence, on ordinary occasions, when she
seems very near on a line with the sun, we see a very small part of the
illuminated hemisphere, which now presents the form of a very thin
crescent like the new moon. And this crescent is supposed to be a little
broader than it would be if only half the planet were illuminated, and to
encircle rather more than half the planet. Now, this is just the effect that
would be produced by an atmosphere refracting the sun's light around
the edge of the illuminated hemisphere.
The difficulty of observations of this kind is such that the conclusion
may be open to doubt. What is seen during transits of Venus over the
sun's disk leads to more certain, but yet very puzzling, conclusions. The
writer will describe what he saw at the Cape of Good Hope during the
transit of December 5, 1882. As the dark planet impinged on the bright
sun, it of course cut out a round notch from the edge of the sun. At first,
when this notch was small, nothing could be seen of the outline of that

part of the planet which was outside the sun. But when half the planet
was on the sun, the outline of the part still off the sun was marked by a
slender arc of light. A curious fact was that this arc did not at first span
the whole outline of the planet, but only showed at one or two points.
In a few moments another part of the outline appeared, and then
another, until, at last, the arc of light extended around the complete
outline. All this seems to show that while the planet has an atmosphere,
it is not transparent like ours, but is so filled with mist and clouds that
the sun is seen through it only as if shining in a fog.
Not many years ago the planet Mars, which is the next one outside of
us, was supposed to have a surface like that of our earth. Some parts
were of a dark greenish gray hue; these were supposed to be seas and
oceans. Other parts had a bright, warm tint; these were supposed to be
the continents. During the last twenty years much has been learned as
to how this planet looks, and the