A wide interest, if not a deep one, attaches to the general question as
to the existence of living beings, or at least the possibility of
organic existence, on planetary bodies other than our own. The question
has been examined in all ages, by the lights of the science peculiar to
each. With every important accession to our astronomical knowledge it
has been re-raised: every considerable discovery has given rise to some
new step or phase in the discussion, and in this way there has grown up
a somewhat extensive literature exclusively relating to mundane
plurality. It will readily be understood that the moon, from its
proximity to the earth, has from the first received a large, perhaps the
largest, share of attention from wanderers into this field of
speculation: and we might add greatly to the bulk of this volume by
merely reviewing some of the more curious and, in their way, instructive
conjectures specially relating to the moon as a world—to imaginary
journeys towards her, and to the beings conjectured to dwell upon and
within her. This, however, we feel there is no occasion to do, for it is
our purpose merely to point out the two or three almost conclusive
arguments against the possibility of any life, animal or vegetable,
having existence on our satellite.

We well know what are the requisite conditions of life on the earth; and
we can go no further for grounds of inference; for if we were to start
by assuming forms of life capable of existence under conditions widely
and essentially different from those pertaining to our planet, there
would be no need for discussing our subject further: we could revel in
conjectures, without a thought as to their extravagance. The only
legitimate phase of the question we can entertain is this:—can there be
on the moon any kind of living things analogous to any kind of living
things upon the earth? And this question, we think, admits only of a
negative answer. The lowest forms of vitality cannot exist without air,
moisture, and a moderate range of temperature. It may be true, as recent
experiments seem to show, that organic germs will retain their vitality
without either of the first, and with exposure to intense cold and to a
considerable degree of heat; and it is conceivable that the mere germs
of life may be present on the moon.[16] But this is not the case with
living organisms themselves. We have, in Chapter V., specially devoted
to the subject, cited the evidence from which we know that there can be
at the most, no more air on the moon than is left in the receiver of an
air-pump after the ordinary process of exhaustion. And with regard to
moisture, it could not exist in any but the vaporous state, and we know
that no appreciable amount of vapour can be discovered by any
observation (and some of them are crucial enough) that we are capable of
making. We may suppose it just within the verge of possibility that some
low forms of vegetation might exist upon the moon with a paucity of air
and moisture such as would be beyond even our most severe powers of
detection: but granting even this, we are met by the temperature
difficulty; for it is inconceivable that any plant-life could survive
exposure first to a degree of cold vastly surpassing that of our arctic
regions, and then in a short time (14 days) to a degree of heat capable
of melting the more fusible metals—the total range being equal, as we
have elsewhere shown, to perhaps 600 or 700 degrees of our thermometric

The higher forms of vegetation could not reasonably be expected to exist
under conditions which the lower forms could not survive. And as regards
the possibility of the existence of animal life in any form or condition
on the lunar surface, the reasons we have adduced in reference to the
non-existence of vegetable life bear still more strongly against the
possibility of the existence of the former. We know of no animal that
could live in what may be considered a vacuum and under such thermal
conditions as we have indicated.

[Illustration: PLATE XXI.

As to man, aëronautic experience teaches us that human life is
endangered when the atmosphere is still sufficiently dense to support 12
inches of mercury in the barometer tube; what then would be his
condition in a medium only sufficiently dense to sustain one-tenth of an
inch of the barometric column? We have evidence from the most delicate
tests that no atmosphere or vapour approaching even this degree of
attenuation exists around the moon’s surface.

Taking all these adverse conditions into consideration we are in every
respect justified in concluding that there is no possibility of animal
or vegetable life existing on the moon, and that our satellite must
therefore be regarded as a barren world.

* * * * * * * *

After this disquisition upon lunar uninhabitability it may appear
somewhat inconsistent for us to attempt a description of the scenery of
the moon and some other effects that would be visible to a spectator,
and of which he would be otherwise sensible, during a day and a night
upon her surface. But we can offer the sufficient apology that an
imaginary sojourn of one complete lunar day and night upon the moon
affords an opportunity of marshalling before our readers some phenomena
that are proper to be noticed in a work of this character, and that have
necessarily been passed over in the series of chapters on consecutive
and special points that have gone before. It may be urged that, in
depicting the moon from such a standpoint as that now to be taken, we
are describing scenes that never have been such in the literal sense of
the word, since no eye has ever beheld them. Still we have this
justification—that we are invoking the conception of things that
actually exist; and that we are not, like some imaginary voyagers to the
moon, indulging in mere flights of fancy. Although it is impossible for
a habitant of this earth fully to realise existence upon the moon, it is
yet possible, indeed almost inevitable, for a thoughtful
telescopist—watching the moon night after night, observing the sun rise
upon a lunar scene, and noting the course of effects that follow till it
sets—it is almost inevitable, we say, for such an observer to identify
himself so far with the object of his scrutiny, as sometimes to become
in thought a lunar being. Seated in silence and in solitude at a
powerful telescope, abstracted from terrestrial influences, and gazing
upon the revealed details of some strikingly characteristic region of
the moon, it requires but a small effort of the imagination to suppose
one’s self actually upon the lunar globe, viewing some distant landscape
thereupon; and under these circumstances there is an irresistible
tendency in the mind to pass beyond the actually _visible_, and to fill
in with what it knows must exist those accessory features and phenomena
that are only hidden from us by distance and by our peculiar point of
view. Where the material eye is baffled, the clairvoyance of reason and
analogy comes to its aid.

Let us then endeavour to realize the strange consequences which the
position and conditions of the moon produce upon the aspect of a lunar
landscape in the course of a lunar day and night.

The moon’s day is a long one. From the time that the sun rises upon a
scene[17] till it sets, a period of 304 hours elapses, and of course
double this interval passes between one sunrise and the next. The
consequences of this slow march of the sun begin to show themselves from
the instant that he rises above the lunar horizon. Dawn, as we have it
on earth, can have no counterpart upon the moon. No atmosphere is there
to reflect the solar beams while the luminary is yet out of actual
sight, and only the glimmer of the zodiacal light heralds the approach
of day. From the black horizon the sun suddenly darts his bright
untempered beams upon the mountain tops, crowning them with dazzling
brilliance while their flanks and valleys are yet in utter darkness.
There is no blending of the night into day. And yet there is a growth of
illumination that in its early stages may be called a twilight, and
which is caused by the slow rise of the sun. Upon the earth, in central
latitudes, the average time occupied by the sun in rising, from the
first glint of his upper edge till the whole disc is in sight, is but
two minutes and a quarter. Upon the moon, however, this time is extended
to a few minutes short of an hour, and, therefore, during the first few
minutes a dim light will be shed by the small visible chord of the solar
disc, and this will give a proportionately modified degree of
illumination upon the prominent portion of the landscape, and impart to
it something of the weird aspect which so strikes an observer of a total
solar eclipse on earth when the scene is lit by the thin crescent of the
re-appearing sun. This impaired illumination constitutes the only dawn
that a lunar spectator could behold. And it must be of short duration;
for when, in the course of half an hour, the solar disc has risen half
into view the lighting would no doubt appear nearly as bright to the eye
as when the entire disc of the sun is above the horizon. In this lunar
sunrise, however, there is none of that gilding and glowing which makes
the phenomenon on earth so gorgeous. Those crimson sky-tints with which
we are familiar are due to the absorption of certain of the polychromous
rays of light by our atmosphere. The blue and violet components of the
solar beams are intercepted by our envelope of vapour, and only the red
portions are free to pass; while on the moon, as there is no atmosphere,
this selective absorption does not occur. If it did, an observer gazing
from the earth upon the regions of the moon upon which the sun is just
rising would see the surface tinted with rosy light. This, however, is
not the case; the faintest lunar features just catching the sun are seen
simply under white light diluted to a low degree of brightness. Only
upon rare occasions is the lunar scenery suffused with coloured
illumination, and these are when, as we shall presently have to
describe, the solar rays reach the moon after traversing the earth’s
atmosphere during an eclipse of the sun.

This atmosphere of ours is the most influential element in beautifying
our terrestrial scenery, and the absence of such an appendage from the
moon is the great modifying cause that affects lunar scenery as compared
with that of the earth. We are accustomed to the sun with its dazzling
brightness—overpowering though it be—subdued and softened by our
vaporous screen. Upon the moon there is no such modification. The sun’s
intrinsic brilliancy is undiminished, its apparent distance is
shortened, and it gleams out in fierce splendour only to be realised,
and then imperfectly, by the conception of a gigantic electric light a
few feet from the eye. And the brightness is rendered the more striking
by the blackness of the surrounding sky. Since there is no atmosphere
there can be no sky-light, for there is nothing above the lunar world to
diffuse the solar beams; not a trace of that moisture which even in our
tropical skies scatters some of the sun’s light and gives a certain
degree of opacity or blueness, deep though it be, to the heavens by day.
Upon the moon, with no light-diffusing vapour, the sky must be as dark
or even darker than that with which we are familiar upon the finest of
moonless nights. And this blackness prevails in the full blaze of the
lunar noon-day sun. If the eye (upon the moon) could bear to gaze upon
the solar orb (which would be less possible than upon earth) or could it
be screened from the direct beams, as doubtless it could by intervening
objects, it would perceive the nebulous and other appendages which we
know as the corona, the zodiacal light, and the red solar protuberances:
or if these appendages could not be viewed with the sun above the
horizon they would certainly be seen in glorious perfection when the
luminary was about to rise or immediately after it had set.

And, notwithstanding the sun’s presence, the planets and stars would be
seen to shine more brilliantly than we see them on the clearest of
nights; the constellations would have the same configurations, though
they would be differently situated with respect to the celestial pole
about which they would appear to turn, for the axis of rotation of the
moon is directed towards a point in the constellation Draco. The stars
would never twinkle or change colour as they appear to us to do, for
scintillation or twinkling is a phenomenon of atmospheric origin, and
they would retain their full brightness, down even to the horizon, since
there would be no haze to diminish their light. The planets, and the
brighter stars at least, would be seen even when they were situated very
near to the sun. The planet Mercury, so seldom detected by terrestrial
gazers, would be almost constantly in view during the lunar day,
manifesting his close attendance on the central luminary by making only
short excursions of about two (lunar) days’ length, first on one side
and then on the other. Venus would be nearly as continuously visible,
though her wanderings would be more extensive on either side. The
zodiacal light also, which in our English latitude and climate is but
rarely seen and in more favourable climes appears only when the sun
itself is hidden beneath the horizon, would upon the moon be seen as a
constant accompaniment to the luminary throughout his daily course
across the lunar sky. The other planets would appear generally as they
do to us on earth, but, never being lost in daylight, their courses
among the stars could be traced with scarcely any interruption.

One planet, however, that adorns the sky of the lunar hemisphere which
is turned towards us deserves special mention from the conspicuous and
highly interesting appearance it must present. We allude to the earth.
To nearly one-half of the moon (that which we never see) this imposing
object can never be visible; but to the half that faces us the
terrestrial planet must appear almost fixed in the sky. A lunar
spectator in (what is to us) the centre of the disc, or about the region
north of the lunar mountains Ptolemy and Hipparchus, would have the
earth in his zenith. From regions upon the moon a little out of what is
to us the centre, a spectator would see the earth a little declining
from the zenith, and this declination would increase as the regions
corresponding to the (to us) apparent edge of the moon were approached,
till at the actual edge it would be seen only upon the horizon. From the
phenomena of libration (explained in Chap. VI.) the earth would appear
from nearly all parts of the lunar hemisphere to which it is visible at
all to describe a small circle in the sky. To an observer, however, upon
the (to us) marginal regions of the lunar globe, it would appear only
during a portion of the lunar day—being visible in fact only in that
part of its small circular path which happened to lie above the
observer’s horizon: in some regions only a portion of the terrestrial
disc would make its brief appearance. From the lunar hemisphere beyond
this marginal line the earth can never be seen at all.

The lunar spectator whose situation enabled him to view the earth would
see it as a moon; and a glorious moon indeed it must be. Its diameter
would be four times as great as that of the moon itself as seen by us,
and the area of its full disc 13 times as great. It would be seen to
pass through its phases, just as does our satellite, once in a lunar day
or a terrestrial month, and during that cycle of phases, since 29 of our
days would be occupied by it, the axial rotation would bring all the
features of its surface configuration into view so many times in
succession. But the greatest beauty of this noble moon would be seen
during the lunar night, in considering which we shall again allude to
it; for when it is full-moon to the earth it is new-earth to the moon.
At lunar midnight this globe of ours is fully illuminated; as morning
nears, the earth-moon wanes, its disc slowly passing through the gibbous
phases until at sunrise it would be just half-illuminated. During the
long forenoon it assumes a crescent which narrows and narrows till at
midday the sun is in line with the earth and the latter is invisible,
save perhaps by a thin line of light marking its upper or lower edge,
accordingly as the sun is apparently above or below it. In the lunar
afternoon an illuminated crescent appears upon the opposite side of the
terrestrial globe, and this widens and widens till it becomes a half
disc by lunar sunset and a full disc by lunar midnight.

The sun in his daily course passes at various distances, sometimes above
and sometimes below, the nearly stationary earth. Obviously it will at
times pass actually behind it, and then the lunar spectator would behold
the sublime spectacle of a total solar eclipse, and that under
circumstances which render the phenomenon far more imposing than its
counterpart can appear from the earth; for whereas, when we see the moon
eclipse the sun, the nearly similar (apparent) diameters of the two
bodies renders the duration of totality extremely short—at most 7
minutes—a lunar spectator, the earth appearing to him four times the
diameter of the sun, and he and the earth being relatively stationary,
would enjoy a view of the totality extending over several hours. During
the passage of the solar disc behind that of the earth, a beautiful
succession of luminous phenomena would be observed to follow from the
refractions and dispersions which the sunbeams would suffer in passing
tangentially through those parts of our atmospheric envelope which lie
in their course; those, for instance, on the margin of the earth, as
seen from the moon. As the sun passed behind the earth, the latter would
be encircled upon the in-going side with a beautiful line of golden
light, deepening in places to glowing crimson, due to the absorption,
already spoken of, of all but the red and orange rays of the sun’s light
by the vapours of our atmosphere. As the eclipse proceeded and totality
came on, this ruddy glow would extend itself nearly, if not all, around
the black earth, and so bright would it be, that the whole lunar
landscape covered by the earth’s shadow would be illuminated with faint
crimson light,[18] save, perhaps, in some parts of the far distance,
upon which the earth had not yet cast its shadow, or off which the
shadow had passed. Although the crimson light would preponderate, it
would not appear bright and red alike all around the earth’s periphery.
The circle of light would be, in fact, _the ring of twilight_ round our
globe, and it would only appear red in those places where the atmosphere
chanced to be in that condition favourable for producing what on earth
we know as red sunset and sunrise. We know that the sun, even in clear
sky, does not always set and rise with the beautiful red glow, which may
be determined by merely local causes, and will therefore vary in
different parts of the earth. Now a lunar spectator watching the sun
eclipsed by the earth, would see, during totality and at a _coup d’œil_,
every point around our world upon which the sun is setting on one side
and rising upon the other. To every part of the earth around what is
then the margin, as seen from the moon, the sun is upon the horizon,
shining through a great thickness of atmosphere, reddening it, and being
reddened by it wherever the vaporous conditions conduce to that
colouration. And at all parts where these conditions obtain, the lunar
eclipse-observer would see the ring of light around the black
earth-globe brilliantly crimsoned; at other parts it would have other
shades of red and yellow, and the whole effect would be to make the
grand earth-ball, hanging in the lunar sky, like a dark sphere in a
circle of glittering gold and rubies.

During the early stages of the eclipse, this chaplet of
brilliant-coloured lights would be brightest upon the side of the
_disappearing_ sun; at the time of central eclipse the radiance
(supposing the sun to pass centrally behind the earth) would be equally
distributed, and during the later stages it would preponderate upon the
side of the _reappearing_ sun. We have endeavoured to give a pictorial
realization of this phenomenon and of the effect of the eclipse upon the
lunar landscape, but such a picture cannot but fall very, very far short
of the reality. (See Plate XXII.)

And now for a time let us turn attention from the lunar sky to the
scenery of the lunar landscape. Let us, in imagination, take our stand
high upon the eastern side of the rampart of one of the great craters.
Height, it must be remarked, is more essential on the moon to command
extent of view than upon the earth, for on account of the comparative
smallness of the lunar sphere the dip of the horizon is very rapid. Such
height, however, would be attained without great exercise of muscular
power, since equal amounts of climbing energy would, from the smallness
of lunar gravity, take a man six times as high on the moon as on the
earth. Let us choose, for instance, the hill-side of Copernicus. The day
begins by a sudden transition. The faint looming of objects under the
united illumination of the half-full earth and the zodiacal light is the
lunar precursor of day-break. Suddenly the highest mountain peaks
receive the direct rays of a portion of the sun’s disc as it emerges
from below the horizon. The brilliant lighting of these summits serves
but to increase, by contrast, the prevailing darkness, for they seem to
float like islands of light in a sea of gloom. At a rate of motion
twenty-eight times slower than we are accustomed to, the light tardily
creeps down the mountain-sides, and in the course of about twelve hours
the whole of the circular rampart of the great crater below us, and
towards the east, shines out in brilliant light, unsoftened by a trace
of mountain-mist. But on the opposite side, looking into the crater,
nothing but blackness is to be seen. As hour succeeds hour, the sunbeams
reach peak after peak of the circular rampart in slow succession, till
at length the circle is complete and the vast crater-rim, 50 miles in
diameter, glistens like a silver-margined abyss of darkness. By-and-by,
in the centre, appears a group of bright peaks or bosses. These are the
now illuminated summits of the central cones, and the development of the
great mountain cluster they form henceforth becomes an imposing feature
of the scene. From our high standpoint, and looking backwards to the
sunny side of our cosmorama, we glance over a vast region of the wildest
volcanic desolation. Craters from five miles diameter downwards crowd
together in countless numbers, so that the surface, as far as the eye
can reach, looks veritably frothed over with them. Nearer the base of
the rampart on which we stand, extensive mountain chains run to north
and to south, casting long shadows towards us; and away to southward run
several great chasms a mile wide and of appalling blackness and depth.
Nearer still, almost beneath us, crag rises on crag and precipice upon
precipice, mingled with craters and yawning pits, towering pinnacles of
rock and piles of scoria and volcanic _débris_. But we behold no sign of
existing or vestige of past organic life. No heaths or mosses soften the
sharp edges and hard surfaces: no tints of cryptogamous or lichenous
vegetation give a complexion of life to the hard fire-worn countenance
of the scene. The whole landscape, as far as the eye can reach, is a
realization of a fearful dream of desolation and lifelessness—not a
dream of death, for that implies evidence of preexisting life, but a
vision of a world upon which the light of life has never dawned.

[Illustration: PLATE XXII.

Looking again, after some hours’ interval, into the great crateral
amphitheatre, we see that the rays of the morning sun have crept down
the distant side of the rampart, opposite to that on which we stand, and
lighted up its vast landslipped terraces into a series of seeming
hill-circles with all the rude and rugged features of a terrestrial
mountain view, and none of the beauties save those of desolate grandeur.
The plateau of the crater is half in shadow 10,000 feet below, with its
grand group of cones, now fully in sight, rising from its centre.
Although these last are twenty miles away and the base of the opposite
rampart fully double that distance, we have no means of judging their
remoteness, for in the absence of an atmosphere there can be no aërial
perspective, and distant objects appear as brilliant and distinct as
those which are close to the observer. Not the brightness only, but the
various colours also of the distant objects are preserved in their full
intensity; for colour we may fairly assume there must be. Mineral
chlorates and sublimates will give vivid tints to certain parts of the
landscape surface, and there must be all the more sombre colours which
are common to mineral matters that have been subjected to fiery
influence. All these tints will shine and glow with their greater or
less intrinsic lustres, since they have not been deteriorated by
atmospheric agencies, and far and near they will appear clear alike,
since there is no aërial medium to veil them or tarnish their pristine

In the lunar landscape, in the line of sight, there are no means of
estimating distances; only from an eminence, where the intervening
ground can be seen, is it possible to realize _magnitude_ in a lunar
cosmorama and comprehend the dimensions of the objects it includes.

And with no air there can be no diffusion of light. As a consequence, no
illumination reaches those parts of the scene which do not receive the
direct solar rays, save the feeble amount reflected from contiguous
illuminated objects, and a small quantity shed by the crescent earth.
The shadows have an awful blackness. As we stand upon our chosen point
of observation, we see on the lighted side of the rampart almost
dazzling brightness, while beneath us, on the side away from the sun,
there is a region many miles in area impenetrable to the sight, for
there is no object within it receiving sufficient light to render it
discernible; and all around us, far and near, there is the violent
contrast between intense brightness of insolated parts and deep gloom of
those in equally intense shadow. The black though starlit sky helps the
violence of this contrast, for the bright mountains in the distance
around us stand forth upon a background formed by the darkness of
interplanetary space. The visible effects of these conditions must be in
every sense unearthly and truly terrible. The hard, harsh glowing light
and pitchy shadows; the absence of all the conditions that give
tenderness to an earthly landscape; the black noonday sky, with the
glaring sun ghastly in its brightness; the entire absence of vestiges of
any life save that of the long since expired volcanoes—all these
conspire to make up a scene of dreary, desolate grandeur that is
scarcely conceivable by an earthly habitant, and that the description we
have attempted but insufficiently pourtrays.

A legitimate extension of the imagination leads us to impressions of
lunar conditions upon other senses than that of sight, to which we have
hitherto confined our fancy. We are met at the outset with a difficulty
in this extension; for it is impossible to conceive the sensations which
the absence of an atmosphere would produce upon the most important of
our bodily functions. If we would attempt the task we must conjure up
feelings of suffocation, of which the thoughts are, however, too
horrible to be dwelt upon; we must therefore maintain the delusion that
we can exist without air, and attempt to realize some of the less
discomforting effects of the absence of this medium. Most notable among
these are the untempered heat of the direct solar rays, and the
influence thereof upon the surface material upon which we suppose
ourselves to stand. During a period of over three hundred hours the sun
pours down his beams with unmitigated ferocity upon a soil never
sheltered by a cloud or cooled by a shower, till that soil is heated, as
we have shown, to a temperature equal nearly to that of melting lead;
and this scorching influence is felt by everything upon which the sun
shines on the lunar globe. But while regions directly insolated are thus
heated, those parts turned from the sun would remain intensely cold, and
that scorching in sunshine and freezing in shade with which mountaineers
on the earth are familiar would be experienced in a terribly exaggerated
degree. Among the consequences, already alluded to, of the alternations
of temperature to which the moon’s crust is thus exposed, are doubtless
more or less considerable expansions and contractions of the surface
material, and we may conceive that a cracking and crumbling of the more
brittle constituents would ensue, together with a grating of contiguous
but disconnected masses, and an occasional dislocation of them. We refer
again to these phenomena to remark that if an atmospheric medium existed
they would be attended with noisy manifestations. There are abundant
causes for grating and crackling sounds, and such are the only sources
of noise upon the moon, where there is no life to raise a hum, no wind
to murmur, no ocean to boom and foam, and no brook to plash. Yet even
these crust-cracking commotions, though they might be felt by the
vibrations of the ground, would not manifest themselves audibly, for
without air there can be no communication between the grating or
cracking body and the nerves of hearing. Dead silence reigns on the
moon: a thousand cannons might be fired and a thousand drums beaten upon
that airless world, but no sound could come from them: lips might quiver
and tongues essay to speak, but no action of theirs could break the
utter silence of the lunar scene.

At a rate twenty-eight times slower than upon earth, the shadows shorten
till the sun attains his meridian height, and then, from the tropical
region upon which we have in imagination stood, nothing is to be seen on
any side, save towards the black sky, but dazzling light. The relief of
afternoon shadow comes but tardily, and the darkness drags its slow
length along the valleys and creeps sluggishly up the mountain-sides
till, in a hundred hours or more, the time of sunset approaches. This
phenomenon is but daybreak reversed, and is unaccompanied by any of the
gorgeous sky tints that make the kindred event so enrapturing on earth.
The sun declines towards the dark horizon without losing one jot of its
brilliancy, and darts the full intensity of its heat upon all it shines
on to the last. Its disc touches the horizon, and in half an hour dips
half-way beneath it, its intrinsic brightness and colour remaining
unchanged. The brief interval of twilight occurs, as in the morning,
when only a small chord of the disc is visible, and the long shadows now
sharpen as the area of light that casts them decreases. For a while the
zodiacal light vies with the earth-moon high in the heavens in
illuminating the scene; but in a few hours this solar appendage passes
out of view, and our world becomes the queen of the lunar night.

At this sunset time the earth, nearly in the zenith of us, will be at
its half-illuminated phase, and even then it will shed more light than
we receive upon the brightest of moonlight nights. As the night
proceeds, the earth-phase will increase through the gibbous stages until
at midnight it will be “full,” and our orb will be seen in its entire
beauty. It will perform at least one of its twenty-four-hourly rotations
during the time that it appears quite full, and the whole of its surface
features will in that time pass before the lunar spectator’s eye. At
times the northern pole will be turned towards our view, at times the
southern; and its polar ice-caps will appear as bright white spots,
marking its axis of rotation. If our lunar sojourn were prolonged we
should observe the northern ice-cap creep downwards to lower latitudes
(during our winter) and retreat again (during our summer); and this
variation would be perceptible in a less degree at the southern pole, on
account of the watery area surrounding it. The seas would appear (so far
as can be inferred) of pale blue-green tint; the continents
parti-coloured: and the tinted spots would vary with the changing
terrestrial seasons, as these are indicated by the positions and
magnitudes of the polar ice-caps. The permanent markings would be ever
undergoing apparent modification by the variations of the white
cloud-belts that encircle the terrestrial sphere. Of the nature of these
variations meteorological science is not as yet in a position to speak:
it would indeed be vastly to the benefit of that science if a view of
the distribution of clouds and vapours over the earth’s surface, as
comprehensive as that we are imagining, could really be obtained.

It might happen at “full-earth,” that a black spot with a fainter
penumbral fringe would appear on one side of the illuminated disc and
pass somewhat rapidly across it. This would occur when the moon passed
exactly between the sun and the earth, and the shadow of the moon was
cast upon the terrestrial disc. We need hardly say that these
shadow-transits would occur upon those astronomically important
occasions when an eclipse of the sun is beheld from the earth.

The other features of the sky during the long lunar night would not
differ greatly from those to which we alluded in speaking of its day
aspects. The stars would be the more brightly visible, from the greater
power of the eye-pupil to open in the absence of the glaring sun, and on
this account the milky-way would be very conspicuous and the brighter
nebulæ would come into view. The constellations would mark the night by
their positions, or the hours might be told off (in periods of
twenty-four each) by the successive reappearances of surface features on
certain parts of the terrestrial disc. The planets in opposition to the
sun would now be seen, and a comet might appear to vary the monotony of
the long lunar night. But a meteor would never flash across the sky,
though dark meteoric particles and masses would continually bombard the
lunar surface, sometimes singly, sometimes in showers. And these would
fall with a compound force due to their initial velocity added to that
of the moon’s attraction. As there is no atmosphere to consume the
meteors by frictional heat or break by its resistance the velocity of
their descent, they must strike the moon with a force to which that of a
cannon-ball striking a target is feeble indeed. A position on the moon
would be an unenviable stand-point from this cause alone.

The lunar landscape by night needs little description: it would be lit
by the earth-moon sufficiently to allow salient features, even at a
distance, to be easily made out, for its moon (_i.e._ the earth) has
thirteen times the light-reflecting area that our’s has. But the night
illumination will change in intensity, since the earth-moon varies from
half-full to full, and again to half-full, between sunset and the next
sunrise. The direction of the light, and hence the positions of the
shadows, will scarcely alter on account of the apparent fixity of the
earth in the lunar sky. A slight degree of warmth might possibly be felt
with the reflected earth-light; but it would be insufficient to mollify
the intensity of the prevailing cold. The heat accumulated by the ground
during the three hundred hours’ sunshine radiates rapidly into space,
there being no atmospheric coat to retain it, and a cooling process
ensues that goes on till, all warmth having rapidly departed, the
previously parched soil assumes a temperature approaching that of
celestial space itself, and which has been, as we have stated, estimated
at about 200° below the Fahrenheit zero. If moisture existed upon the
moon, its night-side would be bound in a grip of frost to which our
Arctic regions would be comparatively tropical. But since there is no
water, the aspect of the lunar scenery remains unmodified by effects of
changing temperature.

Such, then, are the most prominent effects that would manifest
themselves to the visual and other senses of a being transported to the
moon. The picture is not on the whole a pleasant one, but it is
instructive; and our rendering of it, imperfect though it be, may serve
to suggest other inferences that cannot but add to the interest which
always attaches to the contemplation of natural scenes and phenomena
from points of view different from those which we ordinarily occupy.

Apart from the recondite functions of the moon considered as one of the
interdependent members of the solar family, into which it would be
beyond our purpose to inquire, there are certain means by which it
subserves human interests and ministers to the wants of civilized man to
which we deem it desirable to call attention, especially as some of them
are not so self-apparent as to have attracted popular attention.

The most generally appreciated because the most evident of the uses of
the moon is that of a luminary. Popular regard for it is usually
confined to its service in that character, and in that character poets
and painters have never tired in their efforts to glorify it. And
obviously this service as a “lesser light” is sufficiently prominent to
excite our warmest admiration. But moonlight is, from the very
conditions of its production, of such a changeable and fugitive nature,
and it affords after all so partial and imperfect an alleviation of
night’s darkness, that we are fain to regard the light-giving office of
the moon as one of secondary importance. Far more valuable to mankind in
general, so estimable as to lead us to place it foremost in our category
of lunar offices, is the duty which the moon performs in the character
of a sanitary agent. We can conceive no direful consequences that would
follow from a withdrawal of the moon’s mere light; but it is easy to
imagine what highly dangerous results would ensue if the moon ceased to
produce the tides of the ocean. Motion and activity in the elements of
the terraqueous globe appear to be among the prime conditions in
creation. Rest and stagnation are fraught with mischief. While the sun
keeps the atmosphere in constant and healthy circulation through the
agency of the winds, the moon performs an analogous service to the
waters of the sea and the rivers that flow into them. It is as the chief
producer of the tides—for we must not forget that the sun exercises
_its_ tidal influences, though in much lesser degree—that we ought to
place the highest value on the services of the moon: but for its aid as
a mighty scavenger, our shores, where rivers terminate, would become
stagnant deltas of fatal corruption. Twice (to speak generally) a day,
however, the organic matter which rivers deposit in a decomposing state
at their embouchures is swept away by the tidal wave; and thus, thanks
to the moon, a source of direful pestilence is prevented from arising.
Rivers themselves are providentially cleansed by the same means, where
they are polluted by bordering towns and cities which, from the nature
of things, are sure to arise on river banks; and it seems to be also in
the nature of things that the river traversing a city must become its
main sewer. The foul additions may be carried down by the stream in its
natural course towards the ocean, but where the river is large there
will be a decrease in velocity of the current near the mouth or where it
joins the sea, thus causing partial stagnation and consequent deposition
of the deleterient matters. All this, however, is removed, and its
inconceivable evils are averted by our mighty and ever active “sanitary
commissioner,” the moon. We can scarcely doubt that a healthy influence
of less obvious degree is exerted in the wide ocean itself; but,
considering merely human interests, we cannot suppress the conviction
that man is more widely and immediately benefited by this purifying
office of the moon than by any other.

But the sanitary service is not the only one that the moon performs
through the agency of the tides. There is the work of tidal transport to
be considered. Upon tidal rivers and on certain coasts, notwithstanding
wind and the use of steam, a very large proportion of the heavy
merchandize is transported by that slow but powerful “tug” the
flood-tide; and a similar service, for which, however, the moon is not
to be entirely credited, is done by the down-flow of the ebb-tide. Large
ships and heavily-laden rafts and barges are quietly taken in tow by
this unobtrusive prime mover, and moved from the river’s mouth to the
far-up city, and from wharf to wharf along its banks; and a vast amount
of mechanical work is thus gratuitously performed which, if it had to be
provided by artificial means, would represent an amount of money value
which for such a city as London would have to be counted by thousands,
possibly millions, of pounds yearly. For this service we owe the moon
the gratitude that we ought to feel for a direct pecuniary benefactor.

In the existing state of civilization and prosperity, we do not,
however, utilize the power of the tides nearly to the extent of their
capabilities. Our coal mines, rich with “the light of other days”—for
coal was long ago declared by Stevenson to be “bottled sunshine”—at
present furnish us with so abundant a supply of power-generating
material that in our eagerness to use it upon all possible occasions we
are losing sight, or putting out of mind, many other valuable prime
movers, and amongst them that of the rise and fall of the waters, which
can be immediately converted into any form of mechanical power by the
aid of tide-mills. Such mills may be found in existence here and there,
but for the present they are generally out-rivalled by the steam-engine
with all its conveniences and adaptabilities; and hence they have not
shared the benefits of that inventive ingenuity which has achieved such
wonders of mechanical appliance while steam has been in the ascendant.
But it must be remembered that in our extravagant use of coal we are
drawing from a bank into which nothing is being paid. We are consuming
an exhaustive store, and the time must come when it will be needful to
look around in quest of “powers that may be.” Then an impetus may be
given to the application of the tides to mechanical purposes as a prime
mover.[19] For the people of the British Islands the problem would have
an especial importance, viewing the extent of our seaboard and the
number of our tidal rivers. The source of motion that offers itself is
of almost incalculable extent. There is not merely the onward flowing
motion of streams to be utilized, but also the _lift_ of water, which,
if small in extent, is stupendous in amount; and within certain limits
it matters little to the mechanician whether the “foot-pounds” of work
placed at his disposal are in the form of a great mass lifted to a small
height or a small mass lifted to a great height. There is no reason
either why the utilization of the tides should be confined to rivers.
The sea-side might well become the circle of manufacturing industry, and
the millions of tons of water lifted several feet twice daily on our
shores might be converted, even by schemes already proposed, to furnish
the prime movement of thousands of factories. And we must not forget how
completely modern science has demonstrated the inter-convertibility of
all kinds of force, and thus opened the way for the introduction of
systems of transporting power that, in such a state of things as we are
for the moment considering, might be of immense benefit. Gravity, for
instance, can be converted into electricity; and electricity gives us
that wonderful power of transmitting _force_ without transmitting (or
even moving) _matter_, which power we use in the telegraph, where we
generate a force at one end of a wire and _use_ it to ring bells or
deflect needles at the other end, which may be thousands of miles away.
What we do with the slight amount of force needful for telegraphy is
capable of being done with any greater amount. A tide-mill might convert
its mechanical energy by an electro-magnetic engine, and in the form of
electricity its force could be conveyed inland by proper wires and there
reconverted back to mechanical or moving power. True, there would be a
considerable loss of power, but that power would cost nothing for its
first production. Another means ready to hand for transporting power is
by compressed air, which has already done good service; another is the
system so admirably worked out by Sir W. Armstrong, of transmitting
water-power through the agency of an “accumulator,” now so generally
used at our Docks and elsewhere, for working cranes and such other uses.
And as the whole duty of the engineer is to _convert_ the forces of
nature, there is a rich field open for his invention, and upon which he
may one day have to enter, in adapting the pulling force of the moon to
his fellow man’s mechanical wants through the intermediation of the

Another of the high functions of the moon is that by which she subserves
the wants of the navigator, and enables him to track his course over the
pathless ocean. Of the two co-ordinates, Latitude and Longitude, that
are needful to determine the position of a ship at sea (or of any
standpoint upon the earth’s surface) the first is easily found, inasmuch
as it is always equal to the altitude of the celestial pole at the place
of observation. But the determination of the longitude has always been a
difficult problem, and one upon which a vast amount of ingenuity has
been expended. When it was first attacked it was soon discovered that
the moon was the object of all others by which it could be most
accurately and, all things considered, most readily determined. We must
premise that the longitude of one place from another is in effect the
difference between the local times at the two places, so that when we
say that a place or a ship is, for instance, seven hours, twenty-four
minutes, ten seconds, west of Greenwich, we mean that the time-o’-day at
the place or ship is seven hours twenty-four minutes ten seconds earlier
than that at Greenwich. Hence, finding the longitude at sea or at any
place and moment means finding what time it is at Greenwich at that
moment. Of course this could be most easily done if we could set a
timekeeper at Greenwich and rely upon its keeping time during a long sea
voyage; and this plan appeared so feasible that our Government long ago
offered a prize of £20,000 for a timekeeper which would perform to a
stated degree of accuracy after a certain sea voyage. One John Harrison
did make such a timekeeper, that actually satisfied the conditions, and
obtained the prize: and chronometers are now largely used for longitude,
their construction having been brought to great perfection, especially
in England, owing to a continuance (in a less liberal degree, however,)
of Government inducement. But chronometers are not entirely to be relied
on, even where several are carried, which in other than Government ships
is rarely the case: recourse must be had to the heavenly bodies for
check upon the timekeeper. And the moon is, as we have said, the body
that best serves the requirements of the problem.

The lunar method for longitude amounts practically to this. The stars
are fixed; the sun, moon, and planets move amongst them; the sun and
planets with very slow rates of apparent motion, the moon with a very
rapid one. If, then, it be predicted that at a certain instant of
Greenwich time the moon will be a certain distance from a fixed star,
and if the mariner at sea observes _when_ the moon has that exact
distance, he will know the Greenwich time at the instant of his
observation.[20] The moon thus becomes to him as the hand of a
timepiece, whereof the stars are the hour and minute marks, the whole
being, as it were, set to Greenwich time. Then if he knows (which he
does by other observations easily obtained) the local time at his ship,
he can take the difference between the Greenwich time and his time,
which difference is in fact his longitude from Greenwich. The requisite
predictions of the distance of the moon from several fixed stars near
her are given to the utmost exactness for every three hours of every day
and night (when the moon can possibly be seen) in the navigator’s _vade
mecum_, the “Nautical Almanac,” and from these given distances the
navigator can, by a simple process of differencing, obtain the distance,
and hence the Greenwich time, for any intermediate instant at which he
may chance to make his observation. Whenever he can see the moon he can
obtain Greenwich time. Of course the whole value of this method depends
upon the exactitude of the predicted distances corresponding to the
given Greenwich times. These distances are obtained by tables of the
moon’s motions, which must be found from observations. The motions in
question are of an intricacy almost past comprehension, on account of
the disturbing forces to which the moon is subjected by the sun and
planets. The powers of the profoundest mathematicians, from Newton
downwards, have been severely exercised in efforts to group them into a
theory, and represent them by tables capable of furnishing the requisite
exact predictions of lunar positions for nautical purposes. Accurate
observations of the moon’s place night after night have, from the dawn
of this lunar method for longitude, been in urgent request by
mathematicians for the purposes specified, and it was solely to procure
these observations that the Observatory at Greenwich was established,
and mainly for their continued prosecution (and for the stellar
observations necessary for their utilization) that it is sustained. For
two centuries the moon has been unremittingly observed at Greenwich, and
the tables at present used for making the “Nautical Almanac” (those
formed by Prof. Hansen) depend upon the observations there obtained. The
work still goes on, for even now the degree of exactitude is not what is
desired, and astronomers are looking forward with some interest to new
lunar tables which were left complete by the late M. Delaunay, formerly
the head of astronomy in France, based upon a theory which he evolved.
This use of the moon is the grandest of all in respect of the results to
which it has led.

Then, too, regarding the moon as a timekeeper, we must not forget the
service that it renders in furnishing a division of time intermediate
between the day—which is measured by the earth’s rotation—and the year,
which is defined by the earth’s orbital revolution. Notwithstanding the
survival of lunar reckoning in our religious services, we, in our time
and country, scarcely need a moon to mark our months; but we must not
forget that with many ancient people the moon was, and with some is
still, the chief timekeeper, the calendars of such people being lunar
ones, and all their events being reckoned and dated by “moons.” To us,
however, the moon is of great service in this department by enabling us
to fix dates to many historical events, the times of occurrence of which
are uncertain, by reason of defective records or by dependence upon such
uncertain data as “lives of emperors,” years of this or that king’s
reign, or generations of one or another family. The moon now and then
clears up a mystery, or decides a disputed point in chronology, by
furnishing the accurate date of an ancient eclipse, which was a
phenomenon that always inspired awe and secured for itself careful
record. The chronologer is continually applying to the astronomer for
the date and place of visibility of some total eclipse, of which he has
found an imperfect record, veritable as to the fact, but dated only by
reference to some year of a so-and-so’s reign, or by some battle or
other historical occurrence. The eclipses that occurred near the time
are then examined, and when one is found that tallies with recorded
conditions in other respects (such as the time of day and the place of
observation), its indisputable date becomes a starting-point from which
the chronologer works backwards and forwards in safety. There is one
famous eclipse—that predicted by Thales six centuries before Christ,
which put an end to the battle between the Medes and Lydians by the
terror its darkness created in both armies—which is most intimately
associated with ancient chronology, and has been used to rectify a
proximate date (the first year of Cyrus of Babylon) which forms the
foundation of all Scripture chronology. Sacred and profane history alike
are continually receiving assistance from the accurate dates which the
moon, by having caused eclipses of the sun, enables the astronomer to
fix beyond cavil or doubt.

The mention of eclipses reminds us, too, of the use which the moon has
been in increasing, through them, our knowledge of the physical
condition of the sun. If the moon had never intervened to cut off the
blinding glare of the solar disc, we should have been to this day left
to assume that the sun is all-contained by the dazzling globe that we
ordinarily see. But, thanks to the moon’s intervention, we now know that
the sun is by no means the mere naked sphere we should have suspected.
Eclipses have taught us that it is surrounded by an envelope of glowing
gases, and that it has a vast vaporous surrounding, beyond its glowing
atmosphere, which appears to be composed of matter streaming away from
the sun into surrounding space. With these discoveries still in their
infancy, it is impossible to foresee the knowledge to which they will
eventually lead, but they can hardly be barren of fruit, and whatever
they ultimately teach will be so much insight gained into the sublimest
problem that human science has before it—the determination of the source
and maintaining power of the light and heat and vivifying agency of the
sun. In according our thankful reflections to the moon for these
revelations, we must not forget that, should there be inhabitants upon
our neighbouring worlds, Mercury, Venus, and Mars, which have no
satellites, they, the supposed inhabitants, can gain no such knowledge
upon the surroundings of the ruler of the solar system. On the other
hand, any rational being who may be supposed to dwell upon Saturn or
Jupiter, would, through the intervention of their numerous moons, have,
in the latter case especially, far more abundant opportunities of
acquiring the knowledge in question than we have.

Finally, there is a use of the moon which touches us, author and reader,
very closely. It has taught us of a world in a condition totally
different from our own; of a planet without water, without air, without
the essentials to life development, but rather with the conditions for
life destruction; a planet left by the Creator—for wise purposes that we
cannot fully know—as it were but half-formed, with all the igneous
foundations fresh from the cosmical fire, and with its rough-cast
surface in its original state, its fire and mould-marks exposed to our
view. From these we have essayed to resolve some of the processes of
formation, and thus to learn something of the cosmical agencies that are
called forth in the purely igneous era of a planet’s history. We trust
that we, on our part, have shown that the study of the moon may be a
benefit not merely to the astronomer, but to the geologist; for we
behold in it a mighty “medal of creation” doubtless formed of the same
material and struck with the same die that moulded our earth; but while
the dust of countless ages and the action of powerful disintegrating and
denuding elements have eroded and obliterated the earthly impression,
the superscriptions on the lunar surface have remained with their
pristine clearness unsullied, every vestige sharp and bright as when it
left the Almighty Maker’s hands. The moon serves no second-rate or
insignificant service when it teaches us of the variety of creative
design in the worlds of our system, and exalts our estimation of this
peopled globe of ours by showing us that all the planetary worlds have
_not_ been deemed worthy to become the habitations of intelligent

Reflections upon the uses of the moon not unnaturally lead our thoughts
to some matters that may be regarded as abuses. These mainly take the
form of superstitions, erroneous beliefs in the moon’s influence over
terrestrial conditions, and occasionally of erroneous ideas upon the
moon’s functions as a luminary. The first-mentioned are almost beneath
notice, for they include such mythical suspicions as that the moon
influences human sanity and other affections of mind and body; that the
moon’s rays have a decomposing effect upon organic matter; that they
produce blindness by shining upon a sleeper’s eyes; that the moon
determines the hours of human death, which is supposed to occur with the
change of the tide, etc. All such, having no foundation on fact, are put
beyond our consideration. The third matter we have mentioned may also be
dismissed in a very few words. The erroneous ideas upon the moon’s
functions as a luminary, to which we allude, are those which are
manifested by poets and painters, and even historians, who do not
hesitate to bring the moon upon a scene in any form and at any time they
please without reference to actual lunar circumstances. It is no
uncommon thing to see, in a picture representing an evening scene, a
moon introduced which can only be seen in the morning—a waning moon
instead of a waxing one; and astronomical critics have, indeed, caught
artists so far tripping as to put a moon in a picture representing some
event that occurred upon a date when the moon was new, and therefore
invisible. Writers take the same liberties very frequently. A newspaper
correspondent, during the Franco-Prussian war, described the full moon
as shining upon a scene of desolation on a particular night, when really
there was no moon to be seen. One of the most flagrant cases of this
kind, however, occurs in Wolfe’s ballad on “The death of Sir John
Moore,” where it is written that the hero was buried “By the struggling
moonbeam’s misty light.” But the interment actually took place at a time
when the moon was out of sight. We mention these abuses of the moon in
the hope of promoting a better observance of the moon’s luminary office.
They who wish to bring the moon upon a scene, not knowing _ipso facto_
that it was there, should first take the advice of Nick Bottom in the
“Midsummer Night’s Dream,” and make sure of their object by consulting
an almanac.

The second of the specified abuses to which the moon is subject refers
to its supposed influence on the weather; and in the extent to which it
goes this is one of the most deeply rooted of popular errors. That there
is an infinitesimal influence exerted by the moon on our atmosphere will
be seen from the evidence we have to offer, but it is of a character and
extent vastly different from what is commonly believed. The popular
error is shown in its most absurd form when the mere _aspect_ of the
moon, the mere transition from one phase of illumination to another, is
asserted to be productive of a change of weather; as if the gradual
passage from first quarter to second quarter, or from that to third,
could of itself upset an existing condition of the atmosphere; or as if
the conjunction of the moon with the sun could invert the order of the
winds, generate clouds, and pour down rains. A moment’s reasoning ought
to show that the supposed cause and the observed effect have no
necessary connection. In our climate the weather may be said to change
at least every three days, and the moon changes—to retain the popular
term—every seven days; so that the probability of a coincidence of these
changes is very great indeed: when it occurs, the moon is sure to be
credited with causing it. But a theory of this kind is of no use unless
it can be shown to apply in every case; and, moreover, the change must
always be in the same direction: to suppose that the moon can turn a
fine day to a wet one, and a wet day to a fine morrow indiscriminately,
is to make our satellite blow hot and cold with the same mouth, and so
to reduce the supposition to an absurdity. If any marked connection
existed between the state of the air and the aspect of the moon, it must
inevitably have forced itself unsought upon the attention of
meteorologists. In the weekly return of Births, Deaths, and Marriages,
issued by the Registrar-General, a table is given, showing all the
meteorological elements at Greenwich for every day of the year, and a
column is set apart for noting the changes and positions of the moon.
These reports extend backwards nearly a quarter of a century. Here,
then, is a repertory of data that ought to reveal at a glance any such
connection, and would certainly have done so had it existed. But no
constant relation between the moon columns and those containing the
instrument readings has ever been traced. Our meteorological
observatories furnish continuous and unbroken records of atmospheric
variations, extending over long series of years: these afford still more
abundant means for testing the validity of the lunar hypothesis. The
collation has frequently been made for special points in the inquiry,
and certainly _some_ connection has been found to obtain between certain
positions of the moon in her orbit and certain instrumental averages;
but so small are the effects traceable to lunar influence, that they are
almost inappreciable among the grosser irregularities that arise from
other and as yet unexplained causes.

The lunar influences upon our atmosphere most likely to be detected are
those of a tidal character, and those due to the radiation of the heat
which the moon receives from the sun. The first would be shown by the
barometer, which may be called an “atmospheric tide gauge.” Some years
ago Sir Edward Sabine instituted a series of observations at St. Helena,
to determine the variations of barometric indications from hour to hour
of the lunar day. The greatest differences were found to occur between
the times when the moon was on the meridian, and when it was six hours
away from the meridian; in other words, between atmospheric high tide
and low tide. But the average of these differences amounted only to the
four-hundredth part of an inch on the instrument’s scale; a quantity
that no weather observer would heed, that none but the best barometers
would show, and that can have no perceptible effect on weather changes.
The distance of the moon from the earth varies, as is well known, in
consequence of the elliptical form of her orbit: this variation ought
also to produce an effect upon the instrument’s indications; but Colonel
Sabine’s analysis showed that it was next to insensible; the mean
reading at apogee differing from that at perigee by only the
two-thousandth part of an inch. Schubler, a German meteorologist, had
arrived at similarly negative results some years previously. Hence it
appears that the great index of the weather is not sensibly affected by
the state of the moon: the conclusion to be drawn with regard to the
weather itself is obvious enough. As regards the heat received from the
moon, we know, from the recent experiments of Lord Rosse in England, and
Marie Davy in France, elsewhere alluded to, that a degree of warmth
appreciable to the highly sensitive thermopile is exerted by the moon
upon the earth near to the time of full moon, when the sun’s rays have
been pouring their unmitigated heat upon the lunar surface continuously
for fourteen days. And as it is improbable that the whole of the heat
sent earthwards from the moon reaches the earth’s surface, we must infer
that a considerable amount is absorbed in the higher atmosphere, and
does work in evaporating the lighter clouds and thinning the denser
ones. The effect of this upon the earth is to facilitate the radiation
of its heat into space, and so to cool the lower atmospheric strata. And
this effect has been shown to be a veritable one by an exhaustive
tabulation of temperature records from various observatories, which was
undertaken by Mr. Park Harrison. The general conclusion from these was,
that the temperature at the earth’s surface is lower by about 2½ degrees
at moon’s last quarter than at first quarter; the paradoxical result
being what would naturally follow from the foregoing consideration. The
tendency of the full moon to clear the sky has been remarked by several
distinguished authorities, to wit, Sir John Herschel, Humboldt, and
Arago; and in general the clearing may be accepted as a meteorological
fact, though in one case of close examination it has been negatived. It
cannot be doubted that a full moon sometimes shows a night to be clear
that would in the absence of the moon be called cloudy.

When close comparisons are made between the moon’s positions and records
of rain-fall and wind-direction, dim indications of relation exhibit
themselves, which may be the feeble consequences of the change of
temperature just spoken of; but in every case where an effect has been
traced it has been of the most insignificant kind, and no apparent
connexion has been recognized between one effect and another. Certainly
there is nothing that can support the extensive popular belief in lunar
influence on weather, and nothing that can modify the conviction that
this belief as at present maintained is an absurd delusion. Yet its
acceptance is so general, and runs through such varied grades of
society, that we have felt it our duty to dwell upon it to the extent
that we have done.


Having arrived at the conclusion of our subject, it appears to us
desirable that we should recall to the reader, by a rapid review, its
salient features.

Our main object being to attempt what we conceived to be a rational
explanation of the surface details of the moon which should be in
accordance with the generally received theory of planetary formation,
and with the peculiar physical conditions of the lunar globe—the opening
of our work was a summary of the nebular hypothesis as it was started by
the first Herschel and systemised by Laplace. Following these
philosophers we endeavoured to show how a chaotic mass of primordial
matter existing in space would, under the action of gravitation, become
transformed into a system of planetary bodies circulating about a common
centre of gravity; and further, how, in some cases, the circulating
planetary masses would themselves become sub-centres of satellitic
systems; our earth being one of these sub-centres with only one
satellitic attendant—to wit, the moon, the subject of our study.

The moon being thus considered as evolved from the parent nebulous mass,
and existing as an isolated and compact body, we had next to consider
what was the effect of the continued action of the gravitating force. By
the light of the beautiful “mechanical theory of heat” we argued that
this force, not being _destructible_, but being _convertible_, was
turned into heat; and that whatever may have been the original condition
of the parent nebulous mass, as regards temperature, its planetary
offspring became elevated to an intense degree of heat as they assumed
the form of spheres under the influence of gravitation.

The incandescent sphere having attained its maximum degree of heat by
the total conversion thereinto of the gravitating force it embodied, we
explained how there must have ensued a dispersion of that heat by
radiation into surrounding space, resulting in the cooling and
consequent solidification of the outermost stratum of the lunar sphere,
and subsequently in the continuation of the cooling process downwards or
inwards to the centre. And here we essayed to prove that in this second
stage of the cooling process, when the crust was solid and the subjacent
portion of the molten sphere was about to solidify, there would come
into operation a principle which appears to govern the behaviour of
certain fusible substances, and which may be concisely termed the
principle of pre-solidifying expansion. We adduced several examples of
the manifestation of this principle, soliciting for it the careful
consideration of physicists and geologists, and looking to it as
furnishing the key to the mystery of volcanic action upon the moon,
since, without needing recourse to aqueous or gaseous sources of
eruptive power, it afforded a rationale of the ejection of the fluid and
semifluid matter of the moon through the solidified crust thereof, and
also of the dislocations of that crust, unattended by actual ejection of
subsurface matter, of which our satellite presents a variety of
examples, and which the earth also appears to have experienced at some
period of its formative history.

Arrived at this stage of our subject we thought it needful to introduce
some pages of data and descriptive detail. Accordingly in one chapter we
discussed the form, magnitude, weight, and density of the moon, and the
force of gravity at its surface: and the more soundly to fix these data
in the mind, we devoted a few lines to explanation of the methods
whereby each has been ascertained. We then examined the question (so
important to our subject) of the existence or non-existence of a lunar
atmosphere, giving the evidence, which may be regarded as conclusive, in
proof of the absence of both air and water from the moon, and,
therefore, refuting the claim of these elements to be considered as
sources or influants of the moon’s volcanic manifestations. A general
_coup-d’œil_ of the lunar hemisphere facing the earth next engaged our
attention, and we considered the aspect of the disc as it is viewed by
the naked eye and with telescopes of various powers. From this general
survey we passed to the topography of the moon, tracing briefly the
admirable labours of those who have advanced this subject, and, by aid
of picture and skeleton maps and a table of position co-ordinates,
placing it within the reader’s power to become more than sufficiently
acquainted for the purposes of this work with the names and positions of
detail objects and features of interest. Special descriptions of
interesting and typical spots and regions were given in some few cases
where such appeared to be called for.

These descriptive matters disposed of, we proceeded to discuss the
various classes of surface features with a view to explaining the
precise actions which appear to us to have led to their formation.
Naturally the craters first demanded our attention. We pointed out the
reasons for regarding the great majority of the circular formations of
the moon as craters, as truly volcanic as those of which we have
examples, modified by obvious causes, upon the earth; and, tracing the
causative phenomena of terrestrial volcanoes, we showed how the
explanations which have been offered to account for them scarcely apply
to those of the moon: and thus, driven to other hypotheses, we
endeavoured to demonstrate the probability of the lunar craters having
been produced by eruptive force, generated by that pre-solidifying
expansion of successive portions of the moon’s molten interior, which we
enunciated in our third chapter. The precise course of phenomena which
resulted in the production of a crater of the normal lunar type, with or
without the significant central cone, were then illustrated by a series
of step-by-step diagrams with accompanying descriptive paragraphs. And
after treating of craters of the normal type we pointed out and
explained some variations thereupon that are here and there to be met
with, and likewise those curious complications of arrangement which
exhibit craters superimposed one upon another and intermingled in
strange confusion.

From craters manifestly volcanic we passed to the consideration of those
circular formations which, from their vastness of size, scarcely admit
of satisfactory explanation by a volcanic hypothesis. We summarized
several proffered theories of their origin, and pointed out what we
considered might be a possible key to the solution of the selenological
enigma which they constitute, without, however, expressing ourselves
entirely satisfied with the validity of our suggestion. The less
mysterious features presented by peaks and mountain ranges were then
discussed to the extent that we considered requisite, viewing their
comparatively simple character and the secondary position they occupy in
point of numerical importance upon the moon. At greater length we dealt
with the cracks and chasms and the allied phenomena of radiating
streaks, pointing out with regard to these latter the strikingly
beautiful correspondence in effect (and therefore presumably in cause)
between them and crack-systems of a glass globe “starred” by an
expanding internal medium.

The more notable objects and features of the lunar surface being
disposed of, we had next to say a few words upon some residual
phenomena, chiefly upon the colour of lunar surface details, and upon
their various degrees of brightness or reflective power. And, inasmuch
as varying brightness seemed to us to be related to varying antiquity,
we were thence led to the question of the chronology of selenological
formations, and to the disputation upon the continuance of volcanic
action upon the moon in recent years. We regarded this question from the
observational and the inferential points of view, and were led to the
conclusion that the moon’s surface arrived at its terminal condition
ages ago, and that it is next to hopeless to look for evidence of
existing change.

Thus far our work dealt with the moon as a planetary body merely. It
occurred to us, however, that we might add to the interest attaching to
our satellite were we to regard it for a time as a world, and consider
its conditions as respects fitness for habitation by beings like
ourselves. The arguments against the possibility of the moon being thus
fitted for human creatures, or, indeed, for any high organism, were
decisive enough to require little enforcing. It appeared to us,
nevertheless, that much might be learnt by imagining one’s self located
upon the moon during a period embracing one lunar day (a month of our
reckoning), with power to comprehend the peculiar circumstances and
conditions of such a situation. We therefore attempted a description of
an imaginary sojourn upon the moon, and pointed out some of the more
striking aspects and phenomena which we know by legitimate inference
would be there manifested. We trust, that while our modest efforts in
the chapter referring to this branch of our subject may prove in some
degree entertaining, they may be in a greater degree instructive,
inasmuch as certain facts are brought into prominence which would not
unnaturally be overlooked in contemplating the moon from the earth, the
only _real_ stand-point that is available to us.

In our final chapter we considered the moon as a satellite, and sought
to enhance popular regard for it on account of certain high functions
which it performs for man’s benefit on this earth; but which are in
great risk of being overlooked. We showed that, notwithstanding the
moon’s occasionally useful service as a nocturnal luminary, it fills a
far higher office as a sanitary agent by cleansing the shores of our
seas and rivers through the agency of the tides. We pointed out the vast
amount of absolutely mechanical work and commercial labour which the
same tidal agency executes in transporting merchandize up and down our
rivers—an amount that, to take the port of London alone, represents a
money value _per annum_ that may be reckoned in millions sterling,
seeing that if our river was tideless all transport would have to be
done by manual or steam power. We then hinted at the stupendous
reservoir of power that the tidal waters constitute, a form of power
which has not as yet been sufficiently called into operation, but which
may be invoked by-and-by, when we have begun to feel more acutely the
consequences of our present prodigal use of the fuel that was stored up
for us by bountiful nature ages upon ages ago. The moon’s services to
the navigator, in affording him a ready means of finding his longitude
at sea; to the chronologist and historian, as a timekeeper, counting
periods too vast for accurate reckoning by other means; to the
astronomer and student of nature, in revealing certain wonderful
surroundings of the solar globe, which, but for the phenomena of
eclipses caused by the moon’s interposition, would never have been
suspected to exist—these were other functions that we dwelt upon, all
too briefly for their deserts; and, lastly, we spoke of the moon as a
medal of creation fraught with instructive suggestions, which it has
been our endeavour to bring to notice in the course of this work. And
from uses we passed to abuses, directing attention to a few popular
errors and widespread illusions relating to lunar influence upon and in
connection with things terrestrial. This part of our work might have
been considerably expanded, for, in truth, the moon has been a
misunderstood and misjudged body. Some justice we trust we have done to
her: we have brought her face to the fireside; we have analysed her
features, and told of virtues that few of her admiring beholders
conceived her to possess. We have traced out her history, fraught with
wonderful interest, and doubtless typical of the history of other
spheres that in countless numbers pervade the universe: and now, having
done our best to make all these points familiar, we commend the moon to
still further study and still more intimate acquaintance, confident that
she will repay all attentions, be they addressed to her as


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