The moon, in consequence of its orbital revolution, having no connecting
axial motion, has always presented but one side to the earth, so that in
process of forming a crust, from its incipient molten state, it became,
by the constant attraction of the earth upon one side, elongated toward
our globe, now generally admitted to be by calculation about thirty
miles, and proved by photographs, which also show an elongation. The
necessary consequence of this constant attraction upon one side, has
been not only to intensify volcanic action there, by the continued
effect of gravitation, so long as its interior remained in a molten
state, but from the same reasoning, to confine all such volcanic action
exclusively to this side of the moon. Thus we have the reason for the
violently disrupted state which that luminary presents to the telescopic
observer, exceeding any analogy to be found upon our globe, as the
earth's axial motion has prevented any similar concentrated action upon
any particular part of its surface, either from solar or lunar
attraction. Another marked effect of the elongation of the moon toward
the earth has been to elevate its visible side high above its atmosphere
(which would have enveloped it as a round body), and in consequence into
an intensely cold region, producing congelation, in the form of frost
and snow, which necessarily envelop its entire visible surface. These
effects took place while yet the crust was thin and frequently disrupted
by volcanic action, and wherever such action took place, the fiery
matter ejected necessarily dissolved the contiguous masses of frost and
snow, and these floods of water, as soon as they receded from the fiery
element, were immediately converted into lengthened ridges of ice,
diverging from the mountain summits like streams of lava. Hence many of
the apparent lava streams are but ridges of ice, and in consequence,
depending upon the angle of reflection (determined by the age of the
moon, which is but its relative position between the sun and earth), all
observers are struck with the brilliancy of the reflected light from
many of those long lines of ridges.
The general surface of the moon presents to the telescopic observer just
that drear, cold, and chalk-like aspect, which our snow-clad mountains
exhibit when the angle of reflection is similar to that in which we
behold the lunar surface. In consequence, its mild light is due to the
myriads of sparkling crystals, which diffusively reflect the rays of the
sun.
As an attentive observer of the moon, I have been much puzzled to know
why none of the hosts of observers, or scientific treatises, have taken
this rational view of such necessary condition of the moon, deduced from
the main facts of its original formation, here named and generally
conceded. In the place of which, we still have stereotyped, in many late
editions on astronomy, the names and localities of numerous seas and
lakes, which advancing knowledge should long since have discarded.
Besides the above conclusions, which necessitate a snowy covering to the
moon, none of the planets exhibit that drear white, except the poles of
Mars, which are admitted to be snow by all astronomers, as we see them
come and go with the appropriate seasons of that planet; whereas the
continents of Mars appear dark, as analogously they do upon our earth,
under the same solar effulgence. The analogy of sunlight, when reflected
from our lofty mountains (at say thirty or forty miles distant) not
covered with snow, viewed under the most favorable circumstances of
brilliant light and the best angle of reflection, with no more of
intervening atmosphere, always present sombre tints; whether viewed with
the unaided eye or through a telescope. Such analogy clearly proves that
no objects short of an absolute white could present such an appearance
as light does upon lunar objects, viewed with high powers, in which the
same drear white remains, without any greater concentration of light (as
we can see objects in the moon whose diameter is five hundred feet) than
is presented to our unaided eye from our own mountain masses. In viewing
the moon with high powers, there is, in fact, a much greater amount of
visible atmosphere intervening than can possibly apply in beholding
objects on our earth, at even a few miles' distance, since if we look at
lunar objects with a power of one thousand times, our atmosphere is thus
magnified a thousand times also.
The main physical features of the visible half of the moon, with a good
telescopic power, present an enormously elevated table land, traversed,
here and there, with slightly elevated long ridges, and the general
surface largely pitted with almost innumerable deep cusps or valleys, of
every size, from a quarter of a mile to full thirty miles in diameter;
generally circular and surrounded with elevated ridges, some rising to
lofty jagged summits above the surrounding plain. These ridges, on their
inner sides, show separate terraces and mural precipices, while their
outer slopes display deeply scarred ravines and long spurs at their
bases. These cusps, or deep valleys, are the craters of extinct
volcanoes, and in their centres have generally one or two isolated
sub-mountain peaks, occasionally with divided summits, which were the
centres of expiring volcanic action, similar to those that exist in our
own volcanic regions. Besides which the Lunar Apennines, so called,
present to the eye a long range of mountains with serrated summits, on
one side gradually sloped, with terraces, spurs, and ravines, and the
other side mostly precipitous, casting long shadows, which clearly
define the forms of their summits--all these objects presenting the same
dead white everywhere.
Doubtless the farther side of the moon, which has not been subject to
the same elongating or elevating process, nor the above-named causes for
volcanic disruption, presents a climate and vegetation fitted for the
abode of sentient beings. This side alone presenting an aspect of
extreme desolation, far surpassing our polar regions.
It is generally stated in astronomical works, that shadows projected
from lunar objects are intensely black, owing, it is stated, to there
being no reflecting atmosphere; whereas in my long-continued habit of
observation, those shadows appear no more black than those on our earth,
when they fall on contrasting snowy surfaces. The reason for which, in
the absence of a lunar atmosphere, to render light diffusive, is the
brilliant reflection from snow crystals, upon all contiguous objects,
which lie in an angle to receive the same, and in consequence I have
often observed the forms of objects not directly illuminated by the sun.
The occasional apparent retention of a star on the limb of the moon,
just before or after an occultation, seen by some observers, and thus
evidencing the existence of some atmosphere, is doubtless due to the
slight oscillations of the moon, by which we see a trifle more than half
of that body, during which the atmosphere of its opposite side slightly
impinges upon this.