"And God said, Let there be luminaries in the firmament of heaven
to divide between the day and the night, and let them be for signs
and for seasons, and for days and for years.
"And let them be for luminaries in the firmament of heaven to give
light upon the earth; and it was so.
"And God made the two luminaries, the great ones; the luminary,
the great one, to rule over the day, and the luminary, the small
one, to rule over the night, and also the stars.
"And God gave them in the firmament of heaven to give light upon
the earth.
"And to rule over the day and over the night, and to divide
between the light and between the darkness; and God saw that it
was good.
"And there was evening, and there was morning, a fourth day."
This day's work differs from that of the preceding and succeeding
days, in the fact that its sphere was without the earth, which was
only indirectly influenced by it, and consequently the geological
records give us no direct information upon the subject, though in
two points they tally with the Mosaical account. In the first
place, the deposits of coal, which preceded this period, indicate
a time when a nearly uniform temperature, and that a high one,
prevailed throughout the world. The coal beds are found not only
in tropical regions, but in very high latitudes. Not only is the
vegetation of which these coalfields are the result, analogous to
that which is now found in warm climates only--(this might be the
case, and yet we should not be justified in drawing the inference
that the actual species of plants were tropical, for it often
happens that different species of the same genus, having
considerable external resemblance, are very different in their
habits, some requiring tropical heat, while others flourish only
in temperate climates)--but the marked feature is the astonishing
luxuriance of this vegetation, which could only have been
developed under the most favourable circumstances of warmth and
moisture. Now the heat which any particular portion of the earth's
surface receives from the sun depends entirely upon the latitude.
hence it is impossible that a uniform high temperature could exist
in a world which derived its heat wholly or chiefly from that
source. Whether the high temperature which prevailed on the earth
during the deposition of the coal measures was derived from
internal heat it is impossible to say; it is evident that the
temperature of the earth's surface has been in past times, and
perhaps is now, modified by causes which no scientific research
has been enabled to detect [Footnote: Since the sun's secular
motion has been known, astronomers have suggested that the solar
system has been carried through portions of space having variable
temperatures. Geologists, however, do not seem inclined to accept
this as a sufficient reason for the phenomena observed.]. But we
may safely conclude that during the third day the earth did not
derive its heat from the sun. The second point, the barrenness of
the geological records of this period, will be noticed hereafter.
The record of the fourth day's work admits of two interpretations,
it may describe things merely as they appeared, or as they
actually occurred.
1. It is possible that the events of the fourth day may be
described phenomenally--that up to this period the state of things
on the earth had been to a great extent similar to that which we
have reason to believe is still existing in the planet Jupiter-
that the atmosphere was so charged with vapour that no direct rays
from the heavenly bodies could penetrate it; but that at this
time, owing to the declining heat, a great part of the aqueous
constituents of this vapour had been precipitated in the form of
rain, while other vapours had entered into chemical combinations
with other elements to form the various minerals of the earth's
surface, and the atmosphere had become first translucent, and then
transparent. While this process was going on, no direct light from
the sun, supposing it to be already in existence, could penetrate
the veil. Diffused light only could reach the earth's surface, but
when the atmosphere became clear the sun, moon, and stars would
become visible.
Against this view several objections may be brought. In the first
place, as has been already noticed, we cannot treat the account of
the Creation as derived from ordinary human sources. Either it is
a revelation from the Creator or it is nothing. Now we can readily
admit that a man, speaking of an event which lie had witnessed,
but did not understand, would describe it as it appeared to him,
but we cannot admit this supposition when the work is described by
the Great Artificer Himself. In the next place, the temperature of
the earth's surface must in this case have been affected by the
sun, and must therefore have been more or less dependent upon
latitude--and in the third place the distinction between day and
night must have come into operation, whereas the narrative implies
that it was yet incomplete.
2. The other possible interpretation is, that at this period the
concentration of light and heat in the sun was so far completed
that he became the luminary of the system, which had hitherto
derived its light and heat from other sources. Probably, for a
long time, the internal heat of the planets may have been so great
that they were a light to themselves. This state of things,
however, must have come to an end before animal or vegetable life
could have existed on their surface, but other ways exist, and are
in operation in other parts of the universe, by which light and
heat might have been supplied independently of the sun. That light
which is now gathered up in the sun might for a long time have
existed as a nebulous ring, similar to the well-known Ring Nebula
in Lyra. Any planets existing within such a ring would probably
derive from it sufficient light and heat. Or the nebulous matter,
in a luminous state, while slowly advancing to concentration,
might as yet have been so diffused as to fill a space in which the
earth's orbit was included. In either case the earth would have
received a uniform diffused light, without any alternations of
night and day. It is of course impossible that we should be able
to say whether there are any worlds in which such a state of
things prevails at present. Up to this time, with one possible
exception, [Footnote: "Sirius is accompanied by a 10 mag. star,
whose existence was suspected (like that of Neptune), long before
its discovery by Alvan Clark in 1861, from the irregular movements
of its primary. But though it appears so small, its disturbing
effects can only be accounted for on the supposition that its mass
is at least half that of Sirius, in which case its light must be
very faint, possibly wholly reflected." (Webb's Celestial Objects,
p. 202.)] the only worlds which the telescope has revealed to us,
beyond the limits of our own system, are self-luminous. No
reflected light is strong enough to make its existence perceptible
at such enormous distances in the most powerful telescope which
has yet been constructed.
There are some facts connected with our own system which make it
appear not improbable that up to the time of which we are speaking
the light which is now gathered up in the sun was diffused over a
space in which at all events the earth's orbit was included. It is
now a recognized fact that all the light of the system is not as
yet wholly concentrated in the sun, as we generally recognize it,
but that to some extent the sun is still a nebulous star. Under
ordinary circumstances we see only that circular disc, which we
usually recognize as the sun. Its surpassing brightness overpowers
every thing else, whether we view it with the unaided eye or
through the telescope. But when the actual disc is hidden from us
by the moon in a total eclipse, other regions of light surrounding
the disc, make their appearance, and in them the most wonderful
processes are continually going on. The simultaneous discoveries
of Messrs. Lockyer and Janssen, in 1868, have enabled some of
these processes to be continuously watched when the sun is not
eclipsed, but others can as yet only be seen during the few
minutes (never amounting to seven) which a total eclipse lasts, so
that as yet we know very little of them.
Immediately surrounding the disc of the sun, which is visible to
the naked eye, is a brilliant ring of light, known now as the
chromosphere or sierra. This is the region which till 1868 could
be seen only during total eclipses, but can now be watched at all
times by means of the spectroscope. In it symptoms of intense
action are from time to time witnessed. For many years past,
whenever a total eclipse occurred, there were observed on the edge
of this ring certain red prominences. The spectroscope has
revealed their nature. They consist chiefly of enormous volumes of
hydrogen, ejected from the surface of the sun with a velocity
almost inconceivable, and at the same time revolving about their
axis after the fashion of a cyclone. [Footnote: Popular Science
Review, January, 1872, p. 150; Look. Byer's Lecture on the Sun, at
Manchester, 1871.] A very remarkable instance of this was observed
in America in September 1871, by Professor Young. A mass of
incandescent hydrogen was propelled to a height of 200,000 miles
above the visible disc; of these the last 100,000 miles were
passed through in 10 minutes. Such events, though not commonly on
so vast a scale, are continually occurring on the surface of the
sun, and they seem to be in close connexion with the magnetic
phenomena occurring on the earth.
Beyond the chromosphere lies the corona. The spectroscope has not
yet rendered this visible at all times, and consequently we are
dependent upon the information to be obtained during the few
minutes of total eclipses, when alone it is visible. Consequently
during recent solar eclipses this has been the point to which the
attention of astronomers has been especially devoted. The eclipse
of December, 1870, decided one point, that the corona was a truly
solar phenomenon, and not, as some astronomers imagined, an
optical phenomenon, produced by our own atmosphere. The corona
presents the appearance of nebulous light, fading as it becomes
more remote from the sun, of very irregular outline, at some
points not extending more than 15', at others as much as 60' or
70' from the sun's disc, or, in other words, reaching to distances
from the sun's surface varying from 400,000 to 1,800,000 miles.
More important information has been obtained from the eclipse of
December 12,1871. It is now ascertained that the corona comprises
not only gaseous elements, especially hydrogen, but also solid or
fluid particles, capable of giving a continuous though very faint
spectrum with dark lines, indicating the existence of matter
capable of reflecting light. The character of the coronal spectrum
very much resembles that of the Nebula in Draco, No. 4373. The
ascertained extent of the corona exceeds a million of miles above
the surface of the sun, and it seems probable that the Zodiacal
light is only a fainter extension of it. [Footnote: Popular
Science Review, April, 1872, pp. 136-146.]
On a clear evening in the early spring months, as soon as twilight
is completely ended, a conical streak of light may be sometimes
seen, arising' from the western horizon, and extending through an
arc of 60 or 70 degrees, nearly in the direction of the Ecliptic,
and finally terminating in a point. This is the Zodiacal light. In
tropical climates it is seen much more frequently, [Footnote:
Humboldt, Kosmos, vol. i. p. 126 (Bohu's edition).] and is much
more brilliant than in England. This then is probably an envelope
of still fainter light than the corona. It must extend beyond the
orbit of Venus, as the maximum elongation of Venus is 47 degrees,
while the Zodiacal light has been traced for 70 degrees, and
probably farther. It is very possible that the earth is
occasionally involved in it, and that from it we derive that
diffused light which, though faint, is very serviceable to us on a
starless evening, and of which no other account has as yet been
given. The light we receive in this way is often as powerful as
that which we should receive from the stars if they were not
hidden by clouds.
These phenomena seem to point to the conclusion that the
condensation of light in the sun has been a very gradual process,
which is even yet incomplete. If we suppose that at the time of
the formation of the coal measures it was not far advanced, but
that a diffused light extended beyond the orbit of the earth,
similar in some respects to the present Zodiacal light, but equal
in intensity to the light which we now see in the corona, the
phenomena of the third day will be satisfactorily accounted for.
There is, however, still an enormous amount of mystery connected
with the sun. It is the centre from which an inconceivable amount
of force in the shape of light, heat, actinism, and probably other
manifestations, is hourly poured forth. If the whole of that force
were divided into two thousand million parts, the portion received
by the earth would be represented by one of those parts, and the
whole amount received by all the planets would fall short of
twelve of them. All the rest is radiated away into space, and so
far as we know at present lost to the system. The question then
arises, "How is this enormous expenditure supplied?" Various
sources of heat have been suggested, but none of them seem
satisfactory. One conceivable source there is, but that lies out
of the domain of science. Then again, metals, which only our most
powerful furnaces will even melt, exist in the sun's atmosphere in
the state of vapour. What must be the intensity of the heat which
underlies that metallic atmosphere? and what can be the solid or
fluid substances which, from the continuity of the spectrum, we
know must exist there?
We turn now to the Mosaic Record to see what light it throws upon
and receives from this investigation. The first thing to be
noticed is that the word used by Moses for the sun and moon is not
the same as that employed to denote light. It properly signifies a
light-holder, such as a candlestick, and harmonizes with the view
that the sun in his original state was not luminous, but was made
a luminary by the condensation of light previously existent under
other conditions. In the next place, though the apparent
dimensions of the sun and moon are the same, Moses correctly
describes the one as "the great light," the other as "the little
light," thus indicating a knowledge to which the astronomers of
his day had probably not attained.
The relation between the accounts of the first and fourth day's
work becomes clear if we assume that the sun was not made a
luminary till the fourth day. The division of night and day
depends upon two things, the rotation of the earth upon its axis,
and the concentration of light in the sun. Hence when the rotation
of the earth commenced that division was potentially provided for,
but the provision would not take effect until the second condition
was fulfilled by the concentration of light in the sun. The
indications given by the coal measures point, as we have seen, to
the same conclusion.
The only remaining question is "What was going on in the earth at
the same time?" Our materials for answering this question are but
scanty. So great an alteration in the sources of light and heat
must have involved great physical changes on the earth's surface,
and there is reason to believe that great mechanical forces were
at work producing vast changes in the relations of land and water.
"It has long been the opinion of the most eminent geologists that
the coalfields of Lancashire and Yorkshire were once united, the
upper coal measures and the overlying Millstone Grit and Toredale
Bocks having been subsequently removed by denudation; but what is
remarkable is the ancient date now assigned to this denudation,
for it seems that a thickness of no less than 10,000 feet of the
coal measures had been carried away before the deposition of even
the lower Permian Rocks, which were thrown down upon the already
disturbed truncated edges of the coal strata." [Footnote: Lyell,
Geology for Students, p. 377.] And this is but a single instance.
During the interval between the deposition of the coal measures,
which seem to belong to the third, and the Saurian remains which
mark the fifth day, we have the Permian and Triassic Rocks, of
which the Magnesian. Limestone and the new Red Sandstone are the
most important representatives in England. Till a very recent
period it was thought that these rocks belonged to a period
remarkably destitute of animal life, very few fossils having been
found in them. Recently, however, some very rich deposits have
been found in the Tyrol, belonging to this period, but they are
only local.
Of the Permian formation Sir C. Lyell says, "Not one of the
species (of fossils) is common to rocks newer than the
Palaeozoic." [Footnote: Geology for Students, p. 369.] This was
not then a time for the origination of new forms of life. In the
Trias, however, the new development of life, which was to attain
its full dimensions on the fifth day, begins to open upon us. The
earliest Saurian fossils are found, and the rocks still present us
with impressions of the feet of reptiles and birds, which walked
over the soft seashore, and left footprints, which were first
dried and hardened by the sun and wind, and then filled up with
fresh sand by the returning tide, but never entirely coalesced
with the new material.
At the close of this period the first traces of mammalian life
occur, in the shape of teeth, which are supposed to have belonged
to some small Marsupial quadrupeds, and in America the whole lower
jaws of three such animals have been discovered; but no other
remains have as yet been traced.
The Trias then seems to mark the boundary between the fourth and
fifth days. The fourth day seems to have been on the earth a
period of great change, not only in physical conditions, but also
in the forms of life. In the latter point of view, however, it
seems to have been marked by the passing-away of old forms much
more than by the origination of new ones, and hence the barrenness
of the Geological Records is in exact accordance with the silence
of the Mosaic Record as to any new developments.