Читать книгу The Continental Monthly, Vol. 6, No 4, August, 1864 - Various - Страница 7

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.