A PLANET’S HISTORY
_Self-sustained Stage_
Up to this point in our retrospective survey the long course of
evolution has taken one line, that of dynamical separation of the
system’s parts with subsequent reunitement of them according to the
laws of celestial mechanics. Of this action I have submitted the reader
my brief: departing in it from common-law practice, in which the cause
of action is short and the brief long. And I have, I trust, guarded
against his appealing on exceptions.
From this point on we have two kinds of development to follow: the
one intrinsic, the chemical; the other incidental, the physical. Not
that, in a way, the one is divorcible from the other. For the physical
makes possible the chemical by furnishing it the conditions to act.
But in another sense, and that which is most thrust upon our notice,
the two are independent. Thus oceans and land, hills and valleys,
clouds and blue sky, as we know them,—everything, pretty much, which
we associate with a world,—are not universal, inevitable, results
of planetary evolution, but resultant, individual, characteristics
of our particular abode. They are as much our own as the peculiar
arithmetic of waiters is theirs, or as used to be the sobriety of the
country doctor’s horse—his and no other’s. Our whole geologic career is
essentially earthly. Not that its fundamental laws are not of universal
application, but the kaleidoscopic patterns they produce depend on the
little idiosyncrasies of the constituents and the mode in which these
fall together. Our everyday experiences we should find quite changed,
could we alight on Venus or on Mars.
On the other hand, the chemical changes which follow a body’s
acquisition of heat, setting in the moment that heat has reached its
acme and starts to decline, are as universal as the universe itself.
They are conditioned, it is true, by the body’s size and by the
position that body occupied in the primal nebula, but they depend
directly upon the degree of heat the body had attained. The larger
the planet, the higher the temperature it reached and the fuller its
possibilities. Even the planets are born to their estate. Thus the
little meteorites live their whole waking life during the few seconds
they spend rushing through our air. For then only does change affect
their otherwise eternally inert careers. That the time is too short for
any important experience is evident on their faces.
Heat is most intimately associated with the very constitution of
matter. It is, in fact, merely the motion of its ultimate particles,
and plays an essential part in their chemical relations. Just as a
certain discreet fervor and sufficient exposure for attraction to take,
make for matrimony, so with the little molecules, a suitable degree of
warmth and a propitious opportunity similarly conduce to conjunction;
too fiery a temperament resulting in a vagabondage preventative of
settled partnership and too cold a one in permanent celibacy. You may
think the simile a touch too anthropomorphic, but it is a most sober
statement of fact. Indeed, it is more than probable that in some dull
sense they feel the impulse, though not the need of expressing it
in verse. That metals can remember their past states seems to have
been demonstrated by Bose, and is certainly in keeping with general
principles as we know them to-day. For memory is the partial retention
of past changes, rendering those changes more facile of repetition.
A high degree of heat, then, makes chemical union impossible, because
the great speeds at which the molecules are rushing past each other
prevents any of them being caught. Lack of speed is equally deterrent.
Nor is it wholly or even principally, perhaps, a movement of the whole
which is here concerned, but a partitive throbbing of the molecule
itself. Certain it is that great cold is as prohibitive of chemic
combination as great heat. Phosphorus, which evinces such avidity for
oxygen at ordinary temperatures as to have got its name from the way it
publishes the fact, at very low ones shows a coolness for its affinity
amounting to absolute unconcern. Thus only within a certain range of
temperature does chemical combination occur. To remain above or below
this is to stay forever immortally dead. To get hot enough in the first
place, and then subsequently to cool, are therefore essential processes
to a body which is to know evolutionary advance.
To pen the history of the solar system and leave out of it all mention
of its most transcendentally wonderful result, the chemical evolution
attendant upon cooling, would be to play “Hamlet” with Hamlet left out.
For the thing which makes the second half of the great cosmic drama so
inconceivably grand is the building up of the infinitely little into
something far finer than the infinitely great. The mechanical action
that first tore a sun apart, and then whirled the fragments into the
beautifully symmetric system we behold to-day, is of a grandeur which
is at least conceivable; the molecular one that, beginning where the
other left off, built up first the diamond and then humanity is one
that passes our power to imagine. That out of the aggregation of
meteorites should come man, a being able to look back over his own
genesis, to be cognizant of it, as it were, from its first beginnings,
is almost to prove him immanent in it from the start. Fortunate it is
that his powers should seem more limited than his perceptions, and the
more so as he goes farther, else he had been but the embodiment of
conceit.
We must sketch, therefore, the steps in this marvellous synthesis;
hastily, for I have already spoken of it elsewhere in print and
repetitions dull appreciation,—in the appreciative,—though we have the
best of precedents for believing that, even in science, to be dull
and iterative insures success; the dulness passing for wisdom and the
iteration tiring opposition out.
In the Sun all substances are in their elemental state. Though its
materials are the same as the Earth’s, we should certainly not feel at
home there, even if we waived the question of comfort, for we should
recognize nothing we know. We talk glibly of elements as if we had
personal acquaintance with them, man’s innate snobbery cropping out.
For to the chemist alone are they observable entities. No one but he
has ever beheld calcium or silicon, or magnesium, or manganese, and
most of us would certainly not know these everyday elements if we met
them on the street. Of all the substances composing the Earth’s crust,
or the air above, or the water beneath, practically the only elements
with which we are personally familiar are iron, copper, and carbon,
and these only in minute quantities and in that order of acquisition;
which accounts for the stone, iron, and bronze ages of man, ending we
may add with the graphite or lead-pencil age of early education.
Yet that elementary substances once existed here we have evidence. We
find such in volcanic vents. That the Earth was once as hot on its
surface as it now is underneath, we know from the condition of the
plutonic rocks where sedimentary strata have not covered them up.
Volcanoes and geysers are our only avenues now to that earlier state of
things. From these pathways to the past, and only from them, do we find
elementary substances produced to-day,—hydrogen, sulphur, chlorine,
oxygen, and carbon.[15] We are thus made aware that once the Earth was
simple, too, on the surface as well as deeper down. A side-light, this,
to what we knew must have been the case.
[15] Geikie, “Geology,” pages 85, 86, and 131-136.
From its primordial state, the least complex compounds were evolved
first. As the heat lessened, higher and higher combinations became
possible. And this is why the more complex molecules are so unstable,
the organic ones the most. Since they are not possible at all under
much stir of their atomic constituents, it shows that the bond between
them must be feeble—and, therefore, easily broken by other causes
besides heat. To the instability of the organic molecule is due its
power; and to cooling, the possibility of its expression.
[Illustration: LOWELL OBSERVATORY SPECTROGRAM SHOWING WATER-VAPOR IN
THE ATMOSPHERE OF MARS, JANUARY 1908.—V. M. SLIPHER.]
For the steps in the chemical process from Sun to habitable Earth
we must look to the spectroscope; not in its older field, the blue
end of the spectrum, but in that which is unfolding to our view in
Dr. Slipher’s ingenious hands, the extension of the observable part
of it into the red. For at that end lie the bands due to planetary
absorption. Here we have already secured surprising results as to the
atmospheres of the various planets. We have not only found positive
evidence of water-vapor in the atmosphere of Mars, but we have detected
strange envelopes in the major planets which show a constitution
different from that of the Sun on the one hand, and of the Earth on
the other. That size and position are for much in these peculiarities,
I have already shown you; but something, too, is to be laid at the
door of age. The major planets are not so advanced in their planetary
history as is our Earth; and Dr. Slipher’s spectrograms of them
disclose what is now going on in that prefatory, childish stage.
These spectrograms are full of possibilities, and it is not too much to
say that chemistry may yet be greatly indebted to the stars. Compounds,
the strange unknown substances there revealed by their spectral
lines, may be cryptic as yet to us. Some of the elements missing in
Mendeléeff’s table may be there, too. Helium was first found in the
Sun; coronium still awaits detection elsewhere. So with these spectral
lines of the outer planets. It looks as if chemistry had been a thought
too previous in making free for others with what should have been their
names, Zenon and Uranium. For we may yet have to speak of Dion and
Varunium.
From the chemical aspect of evolution we pass to its physical side;
from the indirectly to the directly visible results. Here again, to
learn what happened after the sunlike stage, we must turn to the major
planets. For the cooling which induced both physical and chemical
change has there progressed less far, inasmuch as a large globe takes
longer to cool than a small one. To the largest planets, then, we
should look for types of the early planetary stages to-day.
Almost as soon as the telescope was directed to Jupiter, among the
details it disclosed were the Jovian belts (in the year 1630), dark
streaks ruling the planet’s disk parallel to its equator. They are of
the first objects advertised as visible in small glasses to-day, vying
with the craters in the Moon as purchasable wonders of the sky. As the
belts were better and better seen, features came out in them which
proved more and more interesting. Cassini, in 1692, noticed that the
markings travelled round Jupiter and those nearest his equator the
quickest. Sir William Herschel thought them due to Jovian trade-winds,
the planet’s swift rotation making up for deficiency of sun; why, does
not appear.
Modern study of the planet shows that the bright longitudinal layers
between the dark belts are unquestionably belts of cloud. Their
behavior indicates this, and their intrinsic brightness bears it out.
For they are of almost exactly that albedo. Whether they are the kind
of cloud with which we are familiar, clouds of water-vapor, we are not
yet sure. But whatever their constitution, their conduct is quite other
than is exhibited by our own.
In the first place, they are of singular permanence for clouds. The
fleeting forms we know as such assume in the Jovian air a stability
worthy of Jove himself. In their general outlines, they remain the same
for years at a time. “Constant as cloud” would be the proper poetic
simile there. But while remaining true to themselves, they prove to be
in slow, unequal shift with one another. Thus Jupiter’s official day
differs according to the watch of the particular belt that times it.
Spots in different latitudes drift round lazily in appearance, swiftly
in fact, those near the equator as a rule the fastest. Nor is there any
hard and fast latitudinal law; it is a go-as-they-please race in which
one belt passes its neighbor at a rate sometimes of four hundred miles
an hour. The mean day is 9ʰ 55ᵐ long.
[Illustration: JUPITER AND ITS “GREAT RED SPOT”—A DRAWING BY DR.
LOWELL, APRIL 12, 7ʰ 0ᵐ-5ᵐ, 1907.]
[Illustration: JUPITER AND ITS “GREAT RED SPOT”—A DRAWING BY DR.
LOWELL, APRIL 12, 7ʰ 28ᵐ-42ᵐ, 1907.]
A side-light is cast upon the Jovian state of things by the “great red
spot,” which has been more or less visible for thirty years, and which
takes five minutes longer than the equatorial band to travel round. Its
tint bespoke interest in what might be its atmospheric horizon. Yet
it betrayed no sign of being either depressed or exalted with regard
to the rest of the surface. “In 1891,” as Miss Clerke puts it, “an
opportunity was offered of determining its altitude relative to a small
dark spot on the same parallel, by which, after months of pursuit,
it was finally overtaken. An occultation appeared to be the only
alternative from a transit; yet neither occurred. The dark spot chose a
third. It coasted round the obstacle in its way, and got damaged beyond
recognition in the process.” It thus astutely refused to testify.
[Illustration: SUN SPOTS—AFTER BOND.]
Now, this exclusiveness on the part of the “great red spot” really
offers us an insight to its character. Clearly it was no void, but
occupied space with more than ordinary persistency. As it was neither
above nor below the dark spot and shattered that spot on approach,
which its former surroundings had not done, its force must have been
due to motion. This can be explained by its being formed of a vast
uprush of heated vapor from the interior. In short, it was a sort of
baby elephant of a volcano, or geyser, occurring as befits its youth
in fluid, not solid, conditions, but fairly permanent, nevertheless—a
bit of kindergarten Jovian geology. This estimate of it is concurred in
by Dr. Slipher’s spectrogram of the dark and light belts respectively.
For in the spectrum of the dark one we see the distinctive Jovian bands
intensified as if the light had traversed a greater depth of Jovian
air. Its color, a cherry red, abets the conclusion—that in such places
we look down into the fiery, chaotic turmoil so incessantly going on.
[Illustration: PHOTOGRAPH OF A SUN SPOT—AFTER THE LATE M. JANSSEN.]
It is of interest to note that we have prototypes of this sort of
extraterrestrial cyclone in the Sun. His spots are probably local
upsettings of atmospheric equilibrium, using the word atmospheric in
the widest possible sense. Just as our storms are the mildest examples
of the like expostulation at the impossibility of keeping up a too
long continued decorum. Only that with us the Earth is not so much
to blame as the Sun; while both Jupiter and the Sun are themselves
responsible for their condition.
Thus we have, in the very depth of their negation, warrant from the
dark belts of Jupiter that the bright ones are cloud. But also that
they are not clouds ordered as ours. The Jovian clouds pay no sort
of regard to the Sun. In orbital matters Jupiter obeys the ruler of
the system; but he suffers no interference from him in his domestic
affairs. His cloud-belts behave as if the Sun did not exist. Day and
night cause no difference in them; nor does the Jovian year. They come
when they will; last for months, years, decades; and disappear in like
manner. They are _sui Jovis_, caused by vertical currents from the
heated core and strung out in longitudinal procession by Jupiter’s
spin. They are self-raised, not sun-raised, condensations of what is
vaporized below. Jove is indeed the cloud-compeller his name implies.
Yet Jupiter emits no light, unless the cherry red of his darker belts
be considered its last lingering glow. He is thus on the road from Sun
to world, and his present appearance informs us that this incubation
takes place under cloud.
The like is true of Saturn, in fainter replica, even to the cherry
hue. In one way Saturn visibly asserts his independence beyond that
possible by Jupiter. For Jupiter’s equator lies almost in the plane
of his orbit, and on a hasty view the Sun might be credited with the
ordering of the belts, as was indeed long the case. But Saturn’s
inclination to his orbital plane is 27°; yet his belts fit his figure
as neatly as his rings, and never get displaced, no matter how his body
be turned.
Uranus and Neptune are in the same self-centred attitude at present as
the faint traces of belts on their disk, otherwise of the same albedo
as cloud, lead us to conclude. Yet both their densities and their
situation give us to believe them further advanced than the giant
planets, and still they lie wrapped in cloud.
These planets, then, are quite unbeholden to the Sun for all their
present internal economies. What goes on under that veil of clouds with
which they discreetly hide their doings from the too curious astronomic
eye—we can only conjecture. But we discern enough to know that it is
no placid uneventfulness. That it will continue, too, we are assured.
For whether these clouds are largely water-vapor now, or not, to
watery ones they must come as the last of all the wrappers they will
eventually put off.
The major planets are the only ones at the present moment in this
self-centred and self-sustained stage. Their great size has kept them
young. In the smaller terrestrial planets we could not expect to
witness any such condition to-day. If they experienced an ebullient
youth, they have long since outgrown it. Only by rummaging their past
could we find evidence on the point, and this, distance both in time
and space bars us from doing. There is but one body into whose foretime
career we could hope to peer with the slightest prospect of success—our
own Earth.
[Illustration: THE VOLCANO COLIMA, MEXICO, MARCH 24, 1903—JOSÉ MARIA
ARREOLA, PER FREDERICK STARR.]
[Illustration: JUKES BUTTE, A DENUDED LACCOLITH, AS SEEN FROM THE
NORTHWEST—GILBERT.]
[Illustration: IDEAL SECTION OF A LACCOLITH—GILBERT.]
Whether our Earth was ever hot enough at the surface to vaporize
those substances which now form the Jovian or Saturnian clouds, we do
not know; but that it was once hot enough to vaporize water we are
perfectly certain. And this from proof both of what did exist and
of what did not. That the surface temperature was at onetime in the
thousands of degrees Fahrenheit, the Plutonic magma underlying all the
sedimentary rocks of the Earth amply shows. Reversely, the absence
of any effect of water until we reach these sedimentary deposits,
testifies that during all the earlier stages of the Earth’s career
water as such was absent, and as water subsequently appeared, it is
clear that the conditions did not at first allow it to form. We are
sure, therefore, that there was a time when water existed only as
steam, and very possibly a period still anterior to that when it did
not exist at all, its constituent hydrogen and oxygen not having yet
combined. There was certainly an era, then, in the morning of the
ages, when the Earth wore her cloud-wrapper much as Jupiter his now.
That the seas were not once and yet are to-day, affords proof positive
that at some intermediate period they began to be. Avery long
intermediate one it must have been, too,—all the time it took the Earth
to cool from about 2000° C. to 100° C. Not till after the temperature
had fallen to the latter figure in the outer regions of the atmosphere
could clouds form, and not till it had done so at the solid surface
could the steam be deposited as water. Reasoning thus presents us with
a picture of our Earth as a vast seething caldron from which steam
condensing into cloud was precipitated upon a heated layer of rock,
to rise in clouds of steam again. The solid surface had by this time
formed, thickening slowly and more or less irregularly, and into its
larger dimples the water settled as it grew, deepening them into the
great ocean basins of to-day. We see the process with as much certainty
and considerably more comfort than if, in the French sense, we had
assisted at it. Presence of mind now thus amply makes up for absence of
body then.
Passing on evolutionarily we reach more and more tolerable conditions
and solid ground in fact, as well as theory. Thus the crust hardened
and cooled, while the oceans still remained uncomfortably hot. For
water requires much more heat to warm it to a given temperature than
rock, about four and a half times as much. It has therefore by so much
the more to lose, and is proportionally long in the losing. These
hot seas must have produced a small universe of cloud, and as the
conditions were the same all over the Earth, we can see easily with the
mind’s eye that we could not have seen at all with the bodily one, had
we occupied the land in those very early days. To be quite shut out
from curious sight without, was hardly made up for by not being able
to see more than dimly within. Any one who has stood on the edge of a
not-extinct crater when the wind was blowing his way, will have as good
a realization of the then state of things as he probably cares for.
Now this astronomic drawing of the then Earth, which by its lack of
detail allows of no doubt whatever, permits us to offer help in the
elucidation of some of their phenomena to our geologic colleagues.
We are the more emboldened to do so in that they have themselves
appealed to astronomy for diagnosis, and accepted nostrums devised by
themselves. It is always better in such cases to call in a regular
practitioner. Not that he is necessarily more astute, but that he knows
what will not work. It was in the matter of the paleologic climate that
they were led to consult astronomy. The singular thing about paleologic
times was the combination of much warmth with little light; and the
not less singular fact that these conditions were roughly uniform over
the whole Earth. From this universality it was clear, as De Lapparent,
their chief spokesman, puts it, that nothing local could explain the
fact. It was something which demanded a cause common to the globe.
It thus fell properly within the province of astronomy. For if we are
to draw any line between the spheres of influence of the two sciences,
it would seem to lie where totality ends and provincialism begins. I
use this not as a pejorative, but simply to part local color from one
universal drab. In the Earth’s general attributes,—its size, shape, and
weight,—we must have recourse to astronomy to learn the facts. Not less
so for those principal causes which have shaped its general career; we
surrender it only at the point where everyday interest begins, when
those causes that led it through its uninviting youth give way to
effects which in the least concern humanity at large.
Between the mere aggregation of matter into planetary bodies, of which
nebular hypotheses treat, and the specific transformation of plants and
animals upon their surfaces with which organic evolution is concerned,
lies a long history of development, which, beginning at the time
the body starts to cool, continues till it become, for one cause or
another, again an inert mass. In this period is contained its career as
a world. Planetology I have ventured to call the brand of astronomy
which deals with this evolution of worlds. It treats of what is general
and cosmic in that evolution, as geology treats of what is terrestrial
and specific in the history of one member of the class, our own Earth.
The two do not interfere, as the one faces questions in time and space
to which the other remains perforce a stranger. If the picture by the
one be fuller of detail, the canvas of the other permits of the wider
perspective. Certain events in the history of our Earth can only be
explained by astronomy, as geologists have long since recognized. It is
these that fall into our present province.
Geologists, however, have applied astronomy according to their own
ideas. Either they called in aurists, so to speak, when what they
needed was an oculist, or they went to books for their drugs, which
they then administered themselves—a somewhat dangerous practice. Thus
they began by displacing the Earth’s axis in hope of effecting a
result; not realizing that this would only shift the trouble, not cure
it; in fact, make it rather worse. They next tried what De Lapparent,
one of the most brilliant geologists of the age, calls “a variation
in the eccentricity of the ecliptic[16] joined to precession of the
equinoxes,”—a startling condition unknown to astronomy which does not
deal in eccentric planes, whatever such geometric anomalies may be,
but by which its coiner evidently means a change in the eccentricity
of the orbit, as the context shows. Its effect on the Earth, as he
wisely points out, would be to reduce its extremities to extremes. To
get out of his quandary he then embraced a brilliant suggestion of
a brother geologist, M. Blandet. M. Blandet conceived the idea, and
brought it forth unaided, that all that was necessary was a sun big
enough to look down on both poles of the Earth at once. To get this
he travelled back to the time when, in Laplace’s cosmogony, the Sun
filled the whole orbit of Mercury. This conception, which, De Lapparent
remarks, “might, at the time of its apparition, have disconcerted
spirits accustomed to consider our system as stable,”—an apparition
which we may add would certainly continue to disconcert them,—he
says seems to him quite in harmony with that system’s genesis. That
it labors under two physical impossibilities, one on the score of
the Sun, the other on that of the Earth, and that in this case two
negatives do not make an affirmative, need not be repeated here, as
the reader will find it set forth at length elsewhere,[17] together
with what I conceive to be the only explanation of paleothermal times
which will work astronomically—presently to be mentioned. But before
I do so, it is pertinent to record two things that have come to my
notice since. One is that in rereading Faye’s “Origine du Monde,” I
came upon a passage in which it appears that M. Blandet had actually
consulted Faye about his hypothesis, and that Faye had shown him its
impossibility on much the same grounds as those above referred to;
which, however, did not deter M. Blandet from giving it to the world
nor De Lapparent from god-fathering the conception.
[16] “Abrégé de Geologie,” De Lapparent.
[17] “Mars as the Abode of Life,” Macmillan, 1908.
Faye, meanwhile, developed his theory of the origin of the world, and
by it explained the greater heat and lesser light of paleologic times
compared with our own, thus: The Earth evolved before the Sun. In
paleologic times the Sun was still of great extent,—an ungathered-up
residue of nebula that had not yet fallen together enough to
concentrate, not a contracting mass from which the planets had been
detached,—and was in consequence but feebly luminous and of little
heating effect; so that there were no seasons on Earth and no climatic
zones. The Earth itself supplied the heat felt uniformly over its whole
surface.
This differs from my conception, as the reader will see presently, in
one vital point—as to why the Earth was not heated by the Sun. In the
first place Faye’s sun has no _raison d’être_; and in the second no
visible means of existence. If its matter were not already within the
orbit of the Earth at the time, there seems no reason why it should
ever get there; and if there, why it should have been so loath to
condense. We cannot admit, I think, any such juvenility in the Sun at
the time the Earth was already so far advanced as geology shows it to
have been in paleologic times. For the Earth had already cooled below
the boiling-point of water.
[Illustration: TREE FERN.]
To understand the problem from the Earth’s point of view, let us
review the facts with which geology presents us. The flora of
paleologic times, as we see both at their advent in the Devonian and
from their superb development in the Carboniferous era, consisted
wholly of forms whose descendants now seek the shade.[18] Tree ferns,
sigillaria, equisetæ, and other gloom-seeking plants composed it.
That some tree fern survivals to-day can bear the light does not
invalidate the racial tendency. We have plenty of instances in nature
of such adaptability to changed conditions. In fact, the dying out
and deterioration of most of the order shows that the conditions have
changed. And these plants, grown to the dimensions of trees, inhabited
equally the tropic, the temperate, and the frigid zones as we know them
now. Lastly, no annual rings of growth are to be found on them.[19] In
other words, they grew right on, day in, day out. The climate, then,
was as continuous as it was widespread.
[18] De Lapparent, Dana, Geikie, _passim_.
[19] De Lapparent.
On the other hand, astronomy and geology both assert that the seas
were warm.[20] From this it follows that a vastly greater evaporation
must have gone on then than now, and that a welkin of cloud must thus
inevitably have been formed.
[20] De Lapparent, Dana, Geikie, _passim_.
Now put the two facts together, and you have the solution. The climate
was warm and equable over the whole globe because a thick cloud
envelope shut off the Sun’s heat, the heat being wholly supplied from
the steamy seas. At the same time, by the same means the light was
necessarily so tempered as to produce exactly that half-light the ferns
so dearly love. One and the same cause thus answers the double riddle
of greater warmth and less light in those old days than is now the case.
And here comes in the second find I spoke of above, in the person of
some old trilobites who stepped in unexpectedly in corroboration. It
has long been known—though its full significance seems to have escaped
notice—that in 1872 M. Barrande made the discovery that many species
of trilobites of the Cambrian and lower Silurian, the two lowest, and
therefore the oldest, strata of paleozoic times, and distant relative
of our horseshoe crabs, were blind. What is yet more significant,
the most antediluvian were the least provided with eyes. Thus in the
primordial strata, one-fourth of the whole number of species were
eyeless, in the next above one-fifth, and in the latest of all one
two-hundredth only.[21] Furthermore, they testify to the difficulty of
seeing, in two distinct ways, some by having no eyes and some colossal
ones, strenuous individuals increasing their equipment and the lazy
letting it lapse. It seems more than questionable to attribute this
blindness to a deep-sea habitat, as Suess does in describing them, for
they lived in what geologists agree were shallow seas on the site of
Bohemia to-day. Besides, trilobites never had abyssal proclivities; for
they are found preserved in littoral deposits, not in deep-sea silt.
Muddy water may have had some hand in this, but muddy water itself
testifies to great commotion above and torrential rains. So the light
in those seas was not what it became later, or would be now. Thus
these trilobites were antelucan members of their brotherhood, and this
accuses a lack of light in those earlier eras even greater than in
Carboniferous times, which is just where it ought to be found if the
theory is true.
[21] Suess, “The Face of the Earth,” p. 213.
I trust this conception may prove acceptable to geologists, for it
seems imperative from the astronomic side that something of the sort
must have occurred. And it is just as well, if not better, to view it
thus in the light of the dawn of geologic history as to remain in the
dark about it altogether. Nescience is not science—whether hyphenized
or apart; for the whole object of science is to synthesize and explain.
Its body of learning is but the letter, coördination the spirit, of
its law. Nevertheless, the unpardonable impropriety of a new idea,
I am aware, is as reprehensible as the atrocious crime of being a
young man. Yet the world could not get on without both. Time is a sure
reformer and will render the most hardened case of youth senile in
the end. So even a new idea may grow respectable at last. And it is
really as well to make its acquaintance while it still has vigor in it
as to wait till it is old and may be embraced with impunity. Boasted
conservatism is troglodytic, and usually proves a self-conferred
euphuism for dull. For conservatism proceeds from slowness of
apprehension. It may be necessary for certain minds to be in the rear
of the procession, but it is of doubtful glory to find distinction in
the fact.
Thus the youth of a world, like the babyhood of an individual, is
passed screened from immediate contact from without. That this is
the only way that life can originate on a planet we cannot say, but
that it is away in which it does occur, our own Earth attests, and
that, moreover, it is the way with all planets of sufficient size,
the present aspect of the major planets shows. It may well be that
with celestial bodies as with earthly species, some swaddle their
young, others cast them forth to take their chance, and that those
that most protect them rear the higher progeny in the end. What
glories in evolution thus await the giant planets when they shall
have sufficiently cooled down, we can only dimly imagine. But we can
foresee enough to realize that we are not the sum of our solar system’s
possibilities, and by studying the skies read there a future more
wonderful than anything we know.