GEOLOGY.
1. Man, as I trust has been made apparent to the consciousness and
conviction of the reader, is an intelligent, moral, religious, and
spiritual creature; and we have to discuss the difficulty, or
perplexity, or objection, which arises in our minds, when we consider
such a creature as occupying an habitation, which is but one among many
globes apparently equally fitted to be the dwelling-places of living
things--a mere speck in the immensity of creation--an atom among such a
vast array of material structures--a world, as we needs must deem it,
among millions of other objects which appear to have an equal claim to
be regarded as worlds.
2. The difficulty appears to be great, either way. Can the earth alone
be the theatre of such intelligent, moral, religious, and spiritual
action? On the other hand, can we conceive such action to go on in the
other bodies of the universe? If we take the latter alternative, we must
people other planets and other systems with men such as we are, even as
to their history. For the intellectual and moral condition of man
implies a _history_ of the species; and the view of man's condition
which religion presents, not only involves a scheme of which the history
of the human race is a part, but also asserts a peculiar reference had,
in the provisions of God, to the nature of man; and even a peculiar
relation and connection between the human and the divine nature. To
extend such suppositions to other worlds would be a proceeding so
arbitrary and fanciful, that we are led to consider whether the
alternative supposition may not be more admissible. The alternative
supposition is, that man is, in an especial and eminent manner, the
object of God's care; that his place in the creation is, not that he
merely occupies one among millions of similar domiciles provided in
boundless profusion by the Creator of the Universe, but that he is the
servant, subject, and child of God, in a way unique and peculiar; that
his being a spiritual creature, (including his other attributes in the
highest for the sake of brevity,) makes him belong to a spiritual world,
which is not to be judged of merely by analogies belonging to the
material universe.
3. Between these two difficulties the choice is embarrassing, and the
decision must be unsatisfactory, except we can find some further ground
of judgment. But perhaps this is not hopeless. We have hitherto referred
to the evidence and analogies supplied by one science, namely,
astronomy. But there are other sciences which give us information
concerning the nature and history of the earth. From some of these,
perhaps, we may obtain some knowledge of the place of the earth in the
scheme of creation--how far it is, in its present condition, a thing
unique, or only one thing among many like it. Any science which supplies
us with evidence or information on this head, will give us aid in
forming a judgment upon the question under our consideration. To such
sciences, then, we will turn our attention.
One science has employed itself in investigating the nature and history
of the earth by an examination of the materials of which it is
composed; namely, Geology. Let us call to mind some of the results at
which this science has arrived.
4. A very little attention to what is going on among the materials of
which the earth's surface is composed, suffices to show us that there
are causes of change constantly and effectually at work. The earth's
surface is composed of land and water, hills and valleys, rocks and
rivers. But these features undergo change, and produce change in each
other. The mountain-rivers cut deeper and deeper into the ravines in
which they run; they break up the rocks over which they rush, use the
fragments as implements of further destruction, pile them up in sloping
mounds where the streams issue from the mountains, spread them over the
plains, fill up lakes with sediment, push into the sea great deltas. The
sea batters the cliffs and eats away the land, and again, forms banks
and islands where there had been deep water. Volcanoes pour out streams
of lava, which destroy the vegetation over which they flow, and which
again, after a series of years, are themselves clothed with vegetation.
Earthquakes throw down tracts of land beneath the sea, and elevate other
tracts from the bottom of the ocean. These agencies are everywhere
manifest; and though at a given moment, at a given spot, their effect
may seem to us almost imperceptible, too insignificant to be taken
account of, yet in a long course of years almost every place has
undergone considerable changes. Rivers have altered their courses, lakes
have become plains, coasts have been swept away or have become inland
districts, rich valleys have been ravaged by watery or fiery deluges,
the country has in some way or other assumed a new face. The present
aspect of the earth is in some degree different from what it was a few
thousand years ago.
5. But yet, in truth, the changes of which we thus speak have not been
very considerable. The forms of countries, the lines of coasts, the
ranges of mountains, the groups of valleys, the courses of rivers, are
much the same now as they were in ancient times. The face of the earth,
since man has had any knowledge of it, may have undergone some change,
but the changeable has borne a small proportion to the permanent.
Changes have taken place, and are taking place, but they do not take
place rapidly. The ancient earth and the modern earth are, in all their
main physical features, identical; and we must go backwards through a
considerably larger interval than that which carries us back to what we
usually term _antiquity_, before we are led, by the operation of causes
now at work, to an aspect of the earth's surface very different from
that which it now presents.
6. For instance, rivers do, no doubt, more or less alter, in the course
of years, by natural causes. The Rhine, the Rhone, the Po, the Danube,
have, certainly, during the last four thousand years, silted up their
beds in level places, expanded the deltas at their mouths, changed the
channels by which they enter the sea; and very probably, in their upper
parts, altered the forms of their waterfalls and of their shingle beds.
Yet even if we were thus to go backwards ten thousand, or twenty, or
thirty thousand years, (setting aside great and violent causes of
change, as earthquakes, volcanic eruptions, and the like,) the general
form and course of these rivers, and of the ranges of mountains in which
they flow, would not be different from what it is now. And the same may
be said of coasts and islands, seas and bays. The present geography of
the earth may be, and from all the evidence which we have, must be, very
ancient, according to any measures of antiquity which can apply to human
affairs.
7. But yet the further examination of the materials of the earth
carries us to a view beyond this. Though the general forms of the land
and the waters of continents and seas, were, several thousand years ago,
much the same as they now are; yet it was not always so. We have clear
evidence that large tracts which are now dry ground, were formerly the
bed of the ocean; and these, not tracts of the shore, where the varying
warfare of sea and land is still going on, but the very central parts of
great continents; the Alps, the Pyrenees, the Himalayas. For not only
are the rocks of which these great mountain-chains consist, of such
structure that they appear to have been formed as layers of sediment at
the bottom of water; but also, these layers contain vast accumulations
of shells, or impressions of shells, and other remains of marine
animals. And these appearances are not few, limited, or partial. The
existence of such marine remains, in the solid substance of continents
and mountains, is a general, predominant, and almost universal fact, in
every part of the earth. Nor is any other way of accounting for this
fact admissible, than that those materials really have, at some time,
formed bottoms of seas. The various other conjectures and hypotheses,
which were put forward on this subject, when the amount, extent,
multiplicity, and coherence of the phenomena were not yet ascertained,
and when their natural history was not yet studied, cannot now be
considered as worthy of the smallest regard. That many of our highest
hills are formed of materials raised from the depths of ocean, is a
proposition which cannot be doubted, by any one, who fairly examines the
evidence which nature offers.
8. If we take this proposition only, we cannot immediately connect it
with our knowledge respecting the surface of the earth in its present
form. We learn that what is now land, has been sea; and we may suppose
(since it is natural to assume that the bulk of the sea has not much
changed) that what is now sea was formerly land. But, except we can
learn something of the manner in which this change took place, we cannot
make any use of our knowledge. Was the change sudden, or gradual;
abrupt, or successive; brief, or long-continuing?
9. To these questions, the further study of the facts enables us to
return answers with great confidence. The change or changes which
produced the effects of which we have spoken--the conversion of the
bottom of the ocean into the centre of our greatest continents and
highest mountains,--were undoubtedly gradual, successive, and long
continued. We must state very briefly the grounds on which we make this
assertion.
10. The masses which form our mountain-chains, offer evidence, as I have
said, that they were deposited as sediment at the bottom of a sea, and
then hardened. They consist of successive layers of such sediment,
making up the whole mass of the mountain. These layers are, of course,
to a certain extent, a measure of the time during which the deposition
of sediment took place. The thicker the mass of sediment, the more
numerous and varied its beds, and the longer period must we suppose to
have been requisite for its formation. Without making any attempt at
accurate or definite estimation, which would be to no purpose, it is
plain that a mass of sedimentary strata five thousand or ten thousand
feet thick, must have required, for its deposit, a long course of years,
or rather, a long course of ages.
11. But again: on further examination it is found, that we have not
merely one series of sedimentary deposits, thus forming our mountains.
There are a number of different series of such layers or strata, to be
found in different ranges of hills, and in the same range, one series
resting upon another. These different series of strata are
distinguishable from one another by their general structure and
appearance, besides more intimate characters, of which we shall shortly
have to speak. Each such series appears to have a certain consistency of
structure within itself; the layers of which it is composed being more
or less parallel, but the successive series are not thus always
parallel, the lower ones being often highly inclined and irregular,
while the upper ones are more level and continuous: as if the lower
strata had been broken up and thrown into disorder, and then a new
series of strata had been deposited horizontally on their fragments. But
in whatever way these different sedimentary series succeeded each other,
each series must have required, as we have seen, a long period for its
formation; and to estimate the length of the interval between the two
series, we have, at the present stage of our exposition, no evidence.
12. But the mechanical structure of the strata, the result, as it seems,
of aqueous sedimentary deposit, is not the only, nor the most important
evidence, with regard to the length of time occupied by the formation of
the rocky layers which now compose our mountains. As we have said, they
contain shells, and other remains of creatures which live in the sea.
These they contain, not in small numbers, scattered and detached, but in
vast abundance, as they are found in those parts of the ocean which is
most alive with them. There are the remains of oysters and other
shell-fish in layers, as they live at present in the seas near our
shores; of corals, in vast patches and beds, as they now occur in the
waters of the Pacific; of shoals of fishes, of many different kinds, in
immense abundance. Each of these beds of shells, of corals, and of
fishes, must have required many years, perhaps many centuries, for the
growth of the successive individuals and successive generations of which
it consists: as long a time, perhaps, as the present inhabitants of the
sea have lived therein: or many times longer, if there have been many
such successive changes. And thus, while the present condition of the
earth extends backwards to a period of vast but unknown antiquity; we
have, offered to our notice, the evidence of a series of other periods,
each of which, so far as we can judge, may have been as long or longer
than that during which the dry land has had its present form.
13. But the most remarkable feature in the evidence is yet to come. We
have spoken in general of the oysters, and corals, and fishes, which
occur in the strata of our hills; as if they were creatures of the same
kinds which we now designate by those names. But a more exact
examination of these remains of organized beings, shows that this is not
so. The tribes of animals which are found petrified in our rocks are
almost all different, so far as our best natural historians can
determine, from those which now live in our existing seas. They are
different species; different genera. The creatures which we find thus
embedded in our mountains, are not only dead as individuals, but extinct
as species. They belonged, not only to a terrestrial period, but to an
animal creation, which is now past away. The earth is, it seems, a
domicile which has outlasted more than one race of tenants.
14. It may seem rash and presumptuous in the natural historian to
pronounce thus peremptorily that certain forms of life are nowhere to be
found at present, even in the unfathomable and inaccessible depths of
the ocean. But even if this were so, the proposition that the earth has
changed its inhabitants, since the rocks were formed, of which our hills
consist, does not depend for its proof on this assumption. For in the
organic bodies which our strata contain, we find remains, not only of
marine animals, but of animals which inhabit the fresh waters, and the
land, and of plants. And the examination of such remains having been
pursued with great zeal, and with all the aids which natural history can
supply, the result has been, the proofs of a vast series of different
tribes of animals and plants, which have successively occupied the earth
and the seas; and of which the number, variety, multiplicity, and
strangeness, exceed, by far, everything which could have been previously
imagined. Thus Cuvier found, in the limestone strata on which Paris
stands, animals of the most curious forms, combining in the most
wonderful manner the qualities of different species of existing
quadrupeds. In another series of strata, the Lias, which runs as a band
across England from N. E. to S. W., we have the remains of lizards, or
lacertine animals, different from those which now exist, of immense size
and of extraordinary structure, some approaching to the form of fishes
(_ichthyosaurus_); others, with the neck of a serpent; others with
wings, like the fabled forms of dragons. Then beyond these, that is,
anterior to them in the series of time, we have the immense collection
of fossil plants, which occur in the Coal Strata; the shells and corals
of the Mountain Limestone; the peculiar fishes, different altogether
from existing fishes, of the Old Red Sandstone; and though, as we
descend lower and lower, the traces of organic life appear to be more
rare and more limited in kind, yet still we have, beneath these, in
slates and in beds of limestone, many fossil remains, still differing
from those which occur in the higher, and therefore, newer strata.
15. We have no intention of instituting any definite calculation with
regard to the periods of time which this succession of forms of organic
life may have occupied. This, indeed, the boldest geological
speculators have not ventured to do. But the scientific discoveries thus
made, have a bearing upon the analogies of creation, quite as important
as the discoveries of astronomy. And therefore we may state briefly some
of the divisions of the series of terrestrial strata which have
suggested themselves to geological inquirers. At the outset of such
speculations, it was conceived that the lower rocks, composed of
granite, slate, and the like, had existed before the earth was peopled
with living things; and that these, being broken up into inclined
positions, there were deposited upon them, as the sediment of
superincumbent waters, strata more horizontal, containing organic
remains. The former were then called _Primitive_ or _Primary_, the
latter, _Secondary_ rocks. But it was soon found that this was too
sweeping and peremptory a division. Rocks which had been classed as
Primary, were found to contain traces of life; and hence, an
intermediate class of _Transition_ strata was spoken of. But this too
was soon seen to be too narrow a scheme of arrangement, to take in the
rapidly-accumulating mass of facts, organic and others, which the
geological record of the earth's history disclosed. It appeared that
among the fossil-bearing strata there might be discerned a long series
of Formations: the term _Formation_ being used to imply a collection of
successive strata, which, taking into account all the evidence, of
materials, position, relations, and organic remains, appears to have
been deposited during some one epoch or period; so as to form a natural
group, chronologically and physiologically distinct from the others. In
this way it appeared that, taking as the highest part of the Secondary
series, the beds of chalk, which, marked by characteristic fossils, run
through great tracts of Europe, with other beds, of sand and clay, which
generally accompany these; there was, below this _Cretaceous Formation_,
an _Oolitic Formation_, still more largely diffused, and still more
abundant in its peculiar organic remains. Below this, we have, in
England, the _New Red Sandstone Formation_, which, in other countries,
is accompanied by beds abundant in fossils, as the _Muschelkalk_ of
Germany. Below this again we have the _Coal Formation_, and the
_Mountain Limestone_, with their peculiar fossils. Below these, we have
the Old Red Sandstone or Devonian System, with its peculiar fishes and
other fossils. Beneath these, occur still numerous series of
distinguishable strata; which have been arranged by Sir Roderick
Murchison as the members of the _Silurian_ formation; the researches by
which it was established having been carried on, in the first place, in
South Wales, the ancient country of the Silures. Including the lower
part of this formation, and descending still lower in order, is the
_Cambrian_ formation of Professor Sedgwick. And since the races of
organic beings, as we thus descend through successive strata, seem to be
fewer and fewer in their general types, till at last they disappear;
these lower members of the geological series have been termed, according
to their succession, _Palaeozoic_, _Protozoic_, and _Hypozoic_ or
_Azoic_. The general impression on the minds of geologists has been,
that, as we descend in this long staircase of natural steps, we are
brought in view of a state of the earth in which life was scantily
manifested, so as to appear to be near its earliest stages.
16. Each of these formations is of great thickness. Several of the
members of each formation are hundreds, many of them thousands of feet
thick. Taken altogether, they afford an astounding record of the time
during which they must have been accumulating, and during which these
successive groups of animals must have been brought into being, lived,
and continued their kinds.
17. We must add, that over the Secondary strata there are found, in
patches, generally of more limited extent, another, and of course, newer
mass of strata, which have been termed _Tertiary Formations_. Of these,
the strata, near and under Paris, lying in a hollow of the subjacent
strata, and hence termed the _Paris Basin_, attracted prominent notice
in the first place. And these are found to contain an immense quantity
of remains of animals, which, being well preserved, and being subjected
to a careful and scientific scrutiny by the great naturalist George
Cuvier, had an eminent share in establishing in the minds of Geologists
the belief of the extinct character of fossil species, and of the
possibility of reconstructing, from such remains, the animals, different
from those which now live, which had formerly tenanted the earth.
18. We have, in this enumeration, a series of groups of strata, each of
which, speaking in a general way, has its own population of animals and
plants, and is separated, by the peculiarities of these, from the groups
below and above it. Each group may, in a general manner, be considered
as a separate creation of animal and vegetable forms--creatures which
have lived and died, as the races now existing upon the earth live and
die; and of which the living existence may, and according to all
appearance must, have occupied ages, and series of ages, such as have
been occupied by the present living generations of the earth. This
series of creations, or of successive periods of life, is, no doubt, a
very striking and startling fact, very different from anything which the
imagination of man, in previous stages of investigation of the earth's
condition, had conceived; but still, is established by evidence so
complete, drawn from an examination and knowledge of the structures of
living things so exact and careful, as to leave no doubt whatever of the
reality of the fact, on the minds of those who have attended to the
evidence; founded, as it is, upon the analogies, offices, anatomy, and
combinations of organic structures. The progress of human knowledge on
this subject has been carried on and established by the same
alternations of bold conjectures and felicitous confirmations of
them,--of minute researches and large generalizations,--which have given
reality and solidity to the other most certain portions of human
knowledge. That the strata of the earth, as we descend from the highest
to the lowest, are distinguished in general by characteristic or organic
fossils, and that these forms of organization are different from those
which now live on the earth, are truths as clearly and indisputably
established in the minds of those who have the requisite knowledge of
geology and natural history, as that the planets revolve round the sun,
and satellites round the planets. That these epochs of creation are
something quite different from anything which we now see taking place on
the earth, no more disturbs the belief of those facts, which scientific
explorers entertain, than the seemingly obvious difference between the
nebulae which are regarded as yet unformed planetary systems, and the
solar system to which our earth belongs, disturbs the belief of
astronomers, that such nebulae, as well as our system, really exist.
Indeed we may say, as we shall hereafter see, that the fact of our earth
having passed through the series of periods of organic life which
geologists recognize, is, hitherto, incomparably better established,
than the fact that the nebulae, or any of them, are passing through a
series of changes, such as may lead to a system like ours; as some
eminent astronomers in modern times have held. In this respect, the
history of the world, and its place in the universe, are far more
clearly learnt from geology than from astronomy.
19. But with regard to this series of Organic _Creations_, if, for the
sake of brevity, we may call them so; we may naturally ask, in what
manner, by what agencies, at what intervals, they succeeded each other
on the earth? Now, do the researches of geologists give us any
information on these points, which may be brought to bear upon our
present speculations? If we ask these questions, we receive, from
different classes of geologists, different answers. A little while ago,
most geologists held, probably the greater number still hold, that the
transitions from one of these periods of organic life to another, were
accompanied generally by seasons of violent disruption and mutation of
the surface of the earth, exceeding anything which has taken place since
the surface assumed its present general form; in the same proportion as
the changes of its organic population go beyond any such changes which
we can discern to be at present in operation. And there were found to be
changes of other kinds, which seemed to show that these epochs of
organic transition had also been epochs of mechanical violence, upon a
vast and wonderful scale. It appeared that, at some of these epochs at
least, the strata previously deposited, as if in comparative
tranquillity, had been broken, thrust up from below, or drawn or cast
downwards; so that strata which must at first have been nearly level,
were thrown into positions highly inclined, fractured, set on edge,
contorted, even inverted. Over the broken edges of these strata, thus
disturbed and fractured, were found vast accumulations of the fragments
which such rude treatment might naturally produce; these fragmentary
ruins being spread in beds comparatively level, over the bristling edges
of the subjacent rocks, as if deposited in the fluid which had
overwhelmed the previous structure; and with few or no traces of life
appearing in this mass of ruins; while, in the strata which lay over
them, and which appeared to have been the result of quieter times, new
forms of organic life made their appearance in vast abundance. Such is,
for example, the relation of the coal strata in a great part of
England; broken into innumerable basins, ridges, valleys, strips, and
shreds, lying in all positions; and then filled into a sort of level, by
the conglomerate of the magnesian limestone, and the superincumbent red
sandstone and oolites. In other cases it appeared as if there were the
means of tracing, in these dislocations, the agency of igneous stony
matter, which had been injected from below, so as to form
mountain-chains, or the cores of such; and in which the period of the
convulsion could be traced, by the strata to which the disturbance
extended; _those_ strata being supposed to have been deposited before
the eruption, which were thrust upwards by it into highly-inclined
positions; while those strata which, though near to these scenes of
mechanical violence, were still comparatively horizontal, as they had
been originally deposited, were naturally inferred to have been formed
in the waters, after the catastrophe had passed away. By such reasonings
as these, M. Elie de Beaumont has conceived that he can ascertain the
relative ages (according to the vast and loose measurements of age which
belong to this subject) of the principal ranges of mountains of the
earth's surface.
20. Such estimations of age can, indeed, as we have intimated, be only
of the widest and loosest kind; yet they all concur in assigning very
great and gigantic periods of time, as having been occupied by the
events which have formed the earth's strata, and brought them into their
present position. For not only must there have been long ages employed,
as we have said, while the successive generations of each group of
animals lived, and died, and were entombed in the abraded fragments of
the then existing earth; but the other operations which intervened
between these apparently more tranquil processes, must also have
occupied, it would seem, long ages at each interval. The dislocation,
disruption, and contortion of the vast masses of previously existing
mountains, by which their framework was broken up, and its ruins covered
with beds of its own rubbish, many thousand feet thick, and gradually
becoming less coarse and smoother, as the higher beds were deposited
upon the lower, could hardly take place, it would seem, except in
hundreds and thousands of years. And then again, all these processes of
deposition, thus arranging loose masses of material into level beds,
must have taken place in the bottom of deep oceans; and the beds of
these oceans must have been elevated into the position of mountain
ridges which they now occupy, by some mighty operation of nature, which
must have been comparatively tranquil, since it has not much disturbed
those more level beds; and which, therefore, must have been
comparatively long continued. If we accept, as so many eminent
geologists have done, this evidence of a vast series of successive
periods of alternate violence and repose, we must assign to each such
period a duration which cannot but be immense, compared with the periods
of time with which we are commonly conversant. In the periods of
comparative quiet, such as now exist on the earth's surface, and such as
seem to be alone consistent with continued life and successive
generation, deposits at the bottom of lakes and seas take place, it
would seem, only at the rate of a few feet in a year, or perhaps, in a
century. When, therefore, we find strata, bearing evidence of such a
mode of deposit, and piled up to the amount of thousands and tens of
thousands of feet, we are naturally led to regard them as the production
of myriads of years; and to add new myriads, as often as, in the
prosecution of geological research, we are brought to new masses of
strata of the like kind; and again, to interpolate new periods of the
same order, to allow for the transition from one such group to another.
21. Nor is there anything which need startle us, in the necessity of
assuming such vast intervals of time, when we have once brought
ourselves to deal with the question of the antiquity of the earth upon
scientific evidence alone. For if geology thus carries us far backwards
through thousands, it may be, millions of years, astronomy does not
offer the smallest argument to check this regressive supposition. On the
contrary, all the most subtle and profound investigations of astronomers
have led them to the conviction, that the motions of the earth may have
gone on, as they now go on, for an indefinite period of past time. There
is no tendency to derangement in the mechanism of the solar system, so
for as science has explored it. Minute inequalities in the movements
exist, too small to produce any perceptible effect on the condition of
the earth's surface; and even these inequalities, after growing up
through long cycles of ages, to an amount barely capable of being
detected by astronomical scrutiny, reach a maximum; and, diminishing by
the same slow degrees by which they increased, correct themselves, and
disappear. The solar system, and the earth as part of it, constitute, so
for as we can discover, a Perpetual Motion.
22. There is therefore nothing, in what we know of the Cosmical
conditions of our globe, to contradict the Terrestrial evidence for its
vast antiquity, as the seat of organic life. If for the sake of giving
definiteness to our notions, we were to assume that the numbers which
express the antiquity of these four Periods;--the Present organic
condition of the earth; the Tertiary Period of geologists, which
preceded that; the Secondary Period, which was anterior to that; and the
Primary Period which preceded the Secondary; were on the same scale as
the numbers which express these four magnitudes:--the magnitude of the
Earth; that of the Solar System compared with the Earth; the distance
of the nearest Fixed Stars compared with the solar system; and the
distance of the most remote Nebulae compared with the nearest fixed
stars; there is, in the evidence which geological science offers,
nothing to contradict such an assumption.
23. And as the infinite extent which we necessarily ascribe to space,
allows us to find room, without any mental difficulty, for the vast
distances which astronomy reveals, and even leaves us rather embarrassed
with the infinite extent which lies beyond our farthest explorations; so
the infinite duration which we, in like manner, necessarily ascribe to
past time, makes it easy for us, so far as our powers of intellect are
concerned, to go millions of millions of years backwards, in order to
trace the beginning of the earth's existence,--the first step of
terrestrial creation. It is as easy for the mind of man to reason
respecting a system which is billions or trillions of miles in extent,
and has endured through the like number of years, or centuries, as it is
to reason about a system (the earth, for instance,) which is forty
million feet in extent, and has endured for a hundred thousand million
of seconds, that is, a few thousand years.
24. This statement is amply sufficient for the argument which we have to
found upon it; but before I proceed to do that, I will give another view
which has recently been adopted by some geologists, of the mode in which
the successive periods of creation, which geological research discloses
to us, have passed into one another. According to this new view, we find
no sufficient reason to believe that the history of the earth, as read
by us in the organic and mechanical phenomena of its superficial parts,
has consisted of such an alternation of periods of violence and of
repose, as we have just attempted to describe. According to these
theorists, strata have succeeded strata, one group of animals and
plants has followed another, through a season of uniform change; with no
greater paroxysm or catastrophe, it may be, than has occurred during the
time that man has been an observer of the earth. It may be asked, how is
this consistent with the phenomena which we have described;--with the
vast masses of ruin, which mark the end of one period and the beginning
of another, as is the case in passing from the coal measures of England
to the superincumbent beds;--with the highly-inclined strata of the
central masses, and the level beds of the upper formations which have
been described as marking the mountain ranges of Europe? To these
questions, a reply is furnished, we are told, by a more extensive and
careful examination of the strata. It may be, that in certain
localities, in certain districts, the transition, from the mountain
limestone and the coal, to the superjacent sandstones and oolites, is
abrupt and seemingly violent; marked by _unconformable_ positions of the
upper upon the lower strata, by beds of conglomerate, by the absence of
organic remains in certain of these beds. But if we follow these very
strata into other parts of the world, or even into other parts of this
island, we find that this abruptness and incongruity between the lower
and the higher strata disappears. Between the mountain-limestone and the
red sandstone which lies over it, certain new beds are found, which fill
up the incoherent interval; which offer the same evidence as the strata
below and above them, of having been produced tranquilly; and which do
not violently differ in position from either group. The appearance of
incoherence in the series arose from the occurrence, in the region first
examined, of a gap, which is here filled up,--a blank which is here
supplied. Hence it is inferred, that whatever of violence and extreme
disturbance is indicated by the dislocations and ruins there observed,
was local and partial only; and that, at the very time when these
fragmentary beds, void of organized beings, were forming in one place,
there were, at the same time, going on, in another part of the earth's
surface, not far removed, the processes of the life, death and imbedding
of species, as tranquilly as at any other period. And the same assertion
is made with regard to the more general fact, before described, of the
stratigraphical constitution of mountain chains. It is asserted that the
unconformable relation of the strata which compose the different parts
of those chains, is a local occurrence only; and that the same strata,
if followed into other regions, are found conformable to each other; or
are reduced to a virtually continuous scheme, by the interpolation of
other strata, which make a transition, in which no evidence of
exceptional violence appears.
25. We shall not attempt (it is not at all necessary for us to do so) to
decide between the doctrines of the two geological schools which thus
stand in this opposition to each other. But it will be useful to our
argument to state somewhat further the opinions of this latter school on
one main point. We must explain the view which these geologists take of
the mode of succession of one group of _organized_ beings to another; by
which, as we have said, the different successive strata are
characterized. Such a phenomenon, it would at first seem, cannot be
brought within the ordinary rules of the existing state of things. The
species of plants and animals which inhabit the earth, do not change
from age to age; they are the same in modern times, as they were in the
most remote antiquity, of which we have any record. The dogs and horses,
sheep and cattle, lions and wolves, eagles and swallows, corn and vines,
oaks and cedars, which occupy the earth now, are not, we have the
strongest reasons to believe, essentially different now from what they
were in the earliest ages. At least, if one or two species have
disappeared, no new species have come into existence. We cannot conceive
a greater violation of the known laws of nature, than that such an event
as the appearance of a new species should have occurred. Even those who
hold the uniformity of the mechanical changes of the earth, and of the
rate of change, from age to age, and from one geological period to
another; must still, it would seem, allow that the zoological and
phytological changes of which geology gives her testimony, are complete
exceptions to what is now taking place. The formation of strata at the
bottom of the ocean from the ruin of existing continents, may be going
on at present. Even the elevation of the bed of the ocean in certain
places, as a process imperceptibly slow, may be in action at this
moment, as these theorists hold that it is. But still, even when the
beds thus formed are elevated into mountain chains, if that should
happen, in the course of myriads of years, (according to the supposition
it cannot be effected in a less period,) the strata of such mountain
chains will still contain only the species of such creatures as now
inhabit the waters; and we shall have, even then, no succession of
organic epochs, such as geology discovers in the existing mountains of
the earth.
26. The answer which is made to this objection appears to me to involve
a license of assumption on the part of the _uniformitarian_ geologist,
(as such theorists have been termed,) which goes quite beyond the bounds
of natural philosophy: but I wish to state it; partly, in order to show
that the most ingenious men, stimulated by the exigencies of a theory,
which requires some hypothesis concerning the succession of species, to
make it coherent and complete, have still found it impossible to bring
the creation of species of plants and animals within the domain of
natural science; and partly, to show how easily and readily geological
theorists are led to assume periods of time, even of a higher order than
those which I have ventured to suggest.
27. It must, however, be first stated, as a fact on which the assumption
is founded which I have to notice, that the organic groups by which
these successive strata are characterized, are not so distinct and
separate, as it was convenient, for the sake of explanation, to describe
them in the first instance. Although each body of strata is marked by
predominant groups of genera and species, yet it is not true, that all
the species of each formation disappear, when we proceed to the next.
Some species and genera endure through several successive groups of
strata; while others disappear, and new forms come into view, as we
ascend. And thus, the change from one set of organic forms to another,
as we advance in time, is made, not altogether by abrupt transitions,
but in part continuously. The uniformitarian, in the case of organic, as
in the case of mechanical change, obliterates or weakens the evidence of
sudden and catastrophic leaps, by interposing intermediate steps, which
involve, partly the phenomena of the preceding, and partly those of the
subsequent condition. As he allows no universal transition from one
deposit to a succeeding discrepant and unconformable deposit, so he
allows no abrupt and complete transition from one collection of organic
beings,--one creation, as we may call it,--to another. If creation must
needs be an act out of the region of natural science, he will have it to
be at least an act not exercised at distant intervals, and on peculiar
occasions; but constantly going on, and producing its effects, as much
at one time in the geological history of the world, as at another.
28. And this he holds, not only with regard to the geological periods
which have preceded the existing condition of the earth, but also with
regard to the transition from those previous periods to that in which we
live. The present population of the earth is not one in which all
previous forms are extinct. The past population of the earth was not one
in which there are found no creatures still living. On the contrary, he
finds that there exists a vast mass of strata, superior to the secondary
strata, which are characterized by extinct forms, and are yet inferior
to those deposits which are now going on by the agency of obvious
causes. These masses of strata contain a population of creatures, partly
extinct species, and partly such species as are still living on our land
and in our waters. The proportion in which the old and the new species
occur in such strata, is various; and the strata are so numerous, so
rich in organic remains, so different from each other, and have been so
well explored, that they have been classified and named according to the
proportion of new and of old species which they contain. Those which
contain the largest proportion of species still living, have been termed
_Pliocene_, as containing a _greater_ number of _new_ or recent species.
Below these, are strata which are termed _Miocene_, implying a _smaller_
number of _new_ species. Below these again, are others which have been
termed _Eocene_, as containing few new species indeed, but yet enough to
mark the _dawn_, the _Eos_, of the existing state of the organic world.
These strata are, in many places, of very considerable thickness; and
their number, their succession, and the great amount of extinct species
which they contain, shows, in a manner which cannot be questioned, (if
the evidence of geology is accepted at all,) in what a gradual manner, a
portion at least, of the existing forms of organic life have taken the
place of a different population previously existing on the surface of
the globe.
29. And thus the uniformitarian is led to consider the facts which
geology brings to light, as indicating a slow and almost imperceptible,
but, upon the whole, constant series of changes, not only in the
position of the earth's materials, but in its animal and vegetable
population. Land becomes sea and sea becomes land; the beds of oceans
are elevated into mountain regions, carrying with them the remains of
their inhabitants; sheets of lava pour from volcanic vents and overwhelm
the seats of life; and these, again, become fields of vegetation; or, it
may be, descend to the depths of the sea, and are overgrown with groves
of coral; lakes are filled with sediment, imbedding the remains of land
animals, and form the museums of future zoologists; the deltas of mighty
rivers become the centres of continents, and are excavated as
coal-fields by men in remote ages. And yet all this time, so slow is the
change, that man is unaware such changes are going on. He knows that the
mountains of Scandinavia are rising out of the Baltic at the rate of a
few feet in a century; he knows that the fertile slope of Etna has been
growing for thousands of years by the addition of lava streams and
parasitic volcanos; he knows that the delta of the Mississippi
accumulates hundreds of miles of vegetable matter every generation; he
knows that the shores of Europe are yielding to the sea; but all these
appear to him minute items, not worth summing; infinitesimal quantities,
which he cannot integrate. And so, in truth, they are, for him. His
ephemeral existence does not allow him to form a just conception, in any
ordinary state of mind, of the effects of this constant agency of
change, working through countless thousands of years. But Time,
inexhausted and unremitting, sums the series, integrates the formula of
change; and thus passes, with sure though noiseless progress, from one
geological epoch to another.
30. And in the meanwhile, to complete the view thus taken by the
uniformitarian of the geological history of the earth, by some constant
but inscrutable law, creative agency is perpetually at work, to
introduce, into this progressive system of things, new species of
vegetable and animal life. Organic forms, ever and ever new ones, are
brought into being, and left, visible footsteps, as it were, of the
progress which Time has made;--marks placed between the rocky leaves of
the book of creation; by which man, when his time comes, may turn back
and read the past history of his habitation. But the point for us to
remark is, the immeasurable, the inconceivable length of time, if any
length of time could be inconceivable, which is required of our
thoughts, by this new assumption of the constant production of new
species, as a law of creation. We might feel ourselves well nigh
overwhelmed, when, by looking at processes which we see producing only a
few feet of height or breadth or depth during the life of man, we are
called upon to imagine the construction of Alps and Andes,--when we have
to imagine a world made a few inches in a century. But there, at least,
we had _something_ to start from: the element of change was small, but
there _was_ an element of change: we had to expand, but we had not to
originate. But in conceiving that all the myriads of successive species,
which we find in the earth's strata, have come into being by a law which
is now operating, we have _nothing_ to start from. We have seen, and
know of, no such change; all sober and skilful naturalists reject it, as
a fact not belonging to our time. We have here to build a theory without
materials;--to sum a series of which every term, so far as we know, is
nothing;--to introduce into our scientific reasonings an assumption
contrary to all scientific knowledge.
31. This appears to me to be the real character of the assumption of
the constant creation of new species. But, as I have said, it is not my
business here, to pronounce upon the value or truth of this assumption.
The only use which I wish to make of it is this:--If any persons, who
have adopted the geological view which I have just been explaining,
should feel any interest in the speculations here offered to their
notice, they must needs be (as I have no doubt they will be) even more
willing than other geologists, to grant to our argument a scale of time
for geological succession, corresponding in magnitude to the scale of
distances which astronomy teaches us, as those which measure the
relation of the universe to the earth.
This being supposed to be granted, I am prepared to proceed with my
argument.