John Lothrop Motley - "History of the United Netherlands, 1588"

Horace Walpole - "The Letters of Horace Walpole, Volume 1"

P. G. Wodehouse - "The Man Upstairs and Other Stories"

Homer Eon Flint - "The Lord of Death and the Queen of Life"

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PHILADELPHIA, Pa. -- The Philadelphia literary world will celebrate the launch of two new players today, April 10th: Kay Square Press, a new publishing company focused on Philadelphia-area artists, their stories, and their art; and Kay Square's first release, 'With the Rich and Mighty: Emlen Etting of Philadelphia' (ISBN: 978-0-9815129-0-7), a critical biography by Kenneth C. Kaleta.

FlatSigned Press Alleges Don Imus Remarks Damage Legacy of President Gerald R. Ford
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Books: The Harvard Classics Volume 38

V >> Various >> The Harvard Classics Volume 38







UNIFORMITY OF CHANGE


II

SUPPOSED ALTERNATE PERIODS OF REPOSE AND DISORDER--OBSERVED FACTS
IN WHICH THIS DOCTRINE HAS ORIGINATED--THESE MAY BE EXPLAINED BY
SUPPOSING A UNIFORM AND UNINTERRUPTED SERIES OF CHANGES--THREE-
FOLD CONSIDERATION OF THIS SUBJECT: FIRST, IN REFERENCE TO THE
LAWS WHICH GOVERN THE FORMATION OF FOSSILIFEROUS STRATA, AND THE
SHIFTING OF THE AREAS OF SEDIMENTARY DEPOSITION; SECONDLY, IN
REFERENCE TO THE LIVING CREATION, EXTINCTION OF SPECIES, AND
ORIGIN OF NEW ANIMALS AND PLANTS; THIRDLY, IN REFERENCE TO THE
CHANGES PRODUCED IN THE EARTH'S CRUST BY THE CONTINUANCE OF
SUBTERRANEAN MOVEMENTS IN CERTAIN AREAS, AND THEIR TRANSFERENCE
AFTER LONG PERIODS TO NEW AREAS--ON THE COMBINED INFLUENCE OF ALL
THESE MODES AND CAUSES OF CHANGE IN PRODUCING BREAKS AND CHASMS
IN THE CHAIN OF RECORDS--CONCLUDING REMARKS ON THE IDENTITY OF
THE ANCIENT AND PRESENT SYSTEM OF TERRESTRIAL CHANGES.


ORIGIN OF THE DOCTRINE OF ALTERNATE PERIODS OF REPOSE AND
DISORDER.--It has been truly observed, that when we arrange the
fossiliferous formations in chronological order, they constitute
a broken and defective series of monuments: we pass without any
intermediate gradations from systems of strata which are
horizontal, to other systems which are highly inclined--from
rocks of peculiar mineral composition to others which have a
character wholly distinct--from one assemblage of organic remains
to another, in which frequently nearly all the species, and a
large part of the genera, are different. These violations of
continuity are so common as to constitute in most regions the
rule rather than the exception, and they have been considered by
many geologists as conclusive in favour of sudden revolutions in
the inanimate and animate world. We have already seen that
according to the speculations of some writers, there have been in
the past history of the planet alternate periods of tranquillity
and convulsion, the former enduring for ages, and resembling the
state of things now experienced by man, the other brief,
transient, and paroxysmal, giving rise to new mountains, seas,
and valleys, annihilating one set of organic beings, and ushering
in the creation of another.

It will be the object of the present chapter to demonstrate that
these theoretical views are not borne out by a fair
interpretation of geological monuments. It is true that in the
solid framework of the globe we have a chronological chain of
natural records, many links of which are wanting: but a careful
consideration of all the phenomena leads to the opinion that the
series was originally defective--that it has been rendered still
more so by time--that a great part of what remains is
inaccessible to man, and even of that fraction which is
accessible nine-tenths or more are to this day unexplored.

The readiest way, perhaps, of persuading the reader that we may
dispense with great and sudden revolutions in the geological
order of events is by showing him how a regular and uninterrupted
series of changes in the animate and inanimate world must give
rise to such breaks in the sequence, and such unconformability of
stratified rocks, as are usually thought to imply convulsions and
catastrophes. It is scarcely necessary to state that the order of
events thus assumed to occur, for the sake of illustration,
should be in harmony with all the conclusions legitimately drawn
by geologists from the structure of the earth, and must be
equally in accordance with the changes observed by man to be now
going on in the living as well as in the inorganic creation. It
may be necessary in the present state of science to supply some
part of the assumed course of nature hypothetically; but if so,
this must be done without any violation of probability, and
always consistently with the analogy of what is known both of the
past and present economy of our system. Although the discussion
of so comprehensive a subject must carry the beginner far beyond
his depth, it will also, it is hoped, stimulate his curiosity,
and prepare him to read some elementary treatises on geology with
advantage, and teach him the bearing on that science of the
changes now in progress on the earth. At the same time it may
enable him the better to understand the intimate connection
between the Second and Third Books of this work, one of which is
occupied with the changes of the inorganic, the latter with those
of the organic creation.

In pursuance, then, of the plan above proposed, I will consider
in this chapter, first, the laws which regulate the denudation of
strata and the deposition of sediment; secondly, those which
govern the fluctuation in the animate world; and thirdly, the
mode in which subterranean movements affect the earth's crust.

UNIFORMITY OF CHANGE CONSIDERED, FIRST, IN REFERENCE TO
DENUDATION AND SEDIMENTARY DEPOSITION.--First, in regard to the
laws governing the deposition of new strata. If we survey the
surface of the globe, we immediately perceive that it is
divisible into areas of deposition and non-deposition; or, in
other words, at any given time there are spaces which are the
recipients, others which are not the recipients, of sedimentary
matter. No new strata, for example, are thrown down on dry land,
which remains the same from year to year; whereas, in many parts
of the bottom of seas and lakes, mud, sand, and pebbles are
annually spread out by rivers and currents. There are also great
masses of limestone growing in some seas, chiefly composed of
corals and shells, or, as in the depths of the Atlantic, of
chalky mud made up of foraminifera and diatomaceae.

As to the dry land, so far from being the receptacle of fresh
accessions of matter, it is exposed almost everywhere to waste
away. Forests may be as dense and lofty as those of Brazil, and
may swarm with quadrupeds, birds, and insects, yet at the end of
thousands of years one layer of black mould a few inches thick
may be the sole representative of those myriads of trees, leaves,
flowers, and fruits, those innumerable bones and skeletons of
birds, quadrupeds, and reptiles, which tenanted the fertik
region. Should this land be at length submerged, the waves of the
sea may wash away in a few hours the scanty covering of mould,
and it may merely impart a darker shade of colour to the next
stratum of marl, sand, or other matter newly thrown down. So also
at the bottom of the ocean where no sediment is accumulating,
seaweed, zoophytes, fish, and even shells, may multiply for ages
and decompose, leaving no vestige of their form or substance
behind. Their decay, in water, although more slow, is as certain
and eventually as complete as in the open air. Nor can they be
perpetuated for indefinite periods in a fossil state, unless
imbedded in some matrix which is impervious to water, or which at
least does not allow a free percolation of that fluid,
impregnated, as it usually is, with a slight quantity of carbonic
or other acid. Such a free percolation may be prevented either by
the mineral nature of the matrix itself, or by the superposition
of an impermeable stratum; but if unimpeded, the fossil shell or
bone will be dissolved and removed, particle after particle, and
thus entirely effaced, unless petrifaction or the substitution of
some mineral for the organic matter happen to take place.

That there has been land as well as sea at all former geological
periods, we know from the fact that fossil trees and terrestrial
plants are imbedded in rocks of every age, except those which are
so ancient as to be very imperfectly known to us. Occasionally
lacustrine and fluviatile shells, or the bones of amphibious or
land reptiles, point to the same conclusion. The existence of dry
land at all periods of the past implies, as before mentioned, the
partial deposition of sediment, or its limitation to certain
areas; and the next point to which I shall call the reader's
attention is the shifting of these areas from one region to
another.

First, then, variations in the site of sedimentary deposition are
brought about independently of subterranean movements. There is
always a slight change from year to year, or from century to
century. The sediment of the Rhone, for example, thrown into the
Lake of Geneva, is now conveyed to a spot a mile and a half
distant from that where it accumulated in the tenth century, and
six miles from the point where the delta began originally to
form. We may look forward to the period when this lake will be
filled up, and then the distribution of the transported matter
will be suddenly altered, for the mud and sand brought down from
the Alps will thenceforth, instead of being deposited near
Geneva, be carried nearly 200 miles southwards, where the Rhone
enters the Mediterranean.

In the deltas of large rivers, such as those of the Ganges and
Indus, the mud is first carried down for many centuries through
one arm, and on this being stopped up it is discharged by
another, and may then enter the sea at a point 50 or 100 miles
distant from its first receptacle. The direction of marine
currents is also liable to be changed by various accidents, as by
the heaping up of new sandbanks, or the wearing away of cliffs
and promontories.

But, secondly, all these causes of fluctuation in the sedimentary
areas are entirely subordinate to those great upward or downward
movements of land, which will presently be spoken of, as
prevailing over large tracts of the globe. By such elevation or
subsidence certain spaces are gradually submerged, or made
gradually to emerge: in the one case sedimentary deposition may
be suddenly renewed after having been suspended for one or more
geological periods, in the other as suddenly made to cease after
having continued for ages.

If deposition be renewed after a long interval, the new strata
will usually differ greatly from the sedimentary rocks previously
formed in the same place, and especially if the older rocks have
suffered derangement, which implies a change in the physical
geography of the district since the previous conveyance of
sediment to the same spot. It may happen, however, that, even
where the two groups, the superior and the inferior, are
horizontal and conformable to each other, they may still differ
entirely in mineral character, because, since the origin of the
older formation, the geography of some distant country has been
altered. In that country rocks before concealed may have become
exposed by denudation; volcanos may have burst out and covered
the surface with scoriae and lava; or new lakes, intercepting the
sediment previously conveyed from the upper country, may have
been formed by subsidence; and other fluctuations may have
occurred, by which the materials brought down from thence by
rivers to the sea have acquired a distinct mineral character.

It is well known that the stream of the Mississippi is charged
with sediment of a different colour from that of the Arkansas and
Red Rivers, which are tinged with red mud, derived from rocks of
porphyry and red gypseous clays in 'the far west.' The waters of
the Uruguay, says Darwin, draining a granitic country, are clear
and black, those of the Parana, red. [Footnote: Darwin's Journal,
p. 163, and edit., p. 139.] The mud with which the Indus is
loaded, says Burnes, is of a clayey hue, that of the Chenab, on
the other hand, is reddish, that of the Sutlej is more pale.
[Footnote: Journ. Roy. Geograph. Soc., vol. iii, p. 142.] The
same causes which make these several rivers, sometimes situated
at no great distance the one from the other, to differ greatly in
the character of their sediment, will make the waters draining
the same country at different epochs, especially before and after
great revolutions in physical geography, to be entirely
dissimilar. It is scarcely necessary to add that marine currents
will be affected in an analogous manner in consequence of the
formation of new shoals, the emergence of new islands, the
subsidence of others, the gradual waste of neighbouring coasts,
the growth of new deltas, the increase of coral reefs, volcanic
eruptions, and other changes.

UNIFORMITY OF CHANGE CONSIDERED, SECONDLY, IN REGERENCE TO THE
LIVING CREATION.--Secondly, in regard to the vicissitudes of the
living creation, all are agreed that the successive groups of
sedimentary strata found in the earth's crust are not only
dissimilar in mineral composition for reasons above alluded to,
but are likewise distinguishable from each other by their organic
remains. The general inference drawn from the study and
comparison of the various groups, arranged in chronological
order, is this: that at successive periods distinct tribes of
animals and plants have inhabited the land and waters, and that
the organic types of the newer formations are more analogous to
species now existing than those of more ancient rocks. If we then
turn to the present state of the animate creation, and enquire
whether it has now become fixed and stationary, we discover that,
on the contrary, it is in a state of continual flux--that there
are many causes in action which tend to the extinction of
species, and which are conclusive against the doctrine of their
unlimited durability.

There are also causes which give rise to new varieties and races
in plants and animals, and new forms are continually supplanting
others which had endured for ages. But natural history has been
sucessfully cultivated for so short a period, that a few examples
only of local, and perhaps but one or two of absolute,
extirpation of species can as yet be proved, and these only where
the interference of man has been conspicuous. It will
nevertheless appear evident, from the facts and arguments
detailed in the chapters which treat of the geographical
distribution of species in the next volume, that man is not the
only exterminating agent; and that, independently of his
intervention, the annihilation of species is promoted by the
multiplication and gradual diffusion of every animal or plant. It
will also appear that every alteration in the physical geography
and climate of the globe cannot fail to have the same tendency.
If we proceed still farther, and enquire whether new species are
substituted from time to time for those which die out, we find
that the successive introduction of new forms appears to have
been a constant part of the economy of the terrestrial system,
and if we have no direct proof of the fact it is because the
changes take place so slowly as not to come within the period of
exact scientific observation. To enable the reader to appreciate
the gradual manner in which a passage may have taken place from
an extinct fauna to that now living, I shall say a few words on
the fossils of successive Tertiary periods. When we trace the
series of formations from the more ancient to the more modern, it
is in these Tertiary deposits that we first meet with assemblages
of organic remains having a near analogy to the fauna of certain
parts of the globe in our own time. In the Eocene, or oldest
subdivisions, some few of the testacea belong to existing
species, although almost all of them, and apparently all the
associated vertebrata, are now extinct. These Eocene strata are
succeeded by a great number of more modern deposits, which depart
gradually in the character of their fossils from the Eocene type,
and approach more and more to that of the living creation. In the
present state of science, it is chiefly by the aid of shells that
we are enabled to arrive at these results, for of all classes the
testacea are the most generally diffused in a fossil state, and
may be called the medals principally employed by nature in
recording the chronology of past events. In the Upper Miocene
rocks (No. 5 of the table, p. 135) we begin to find a
considerable number, although still a minority, of recent
species, intermixed with some fossils common to the preceding, or
Eocene, epoch. We then arrive at the Pliocene strata, in which
species now contemporary with man begin to preponderate, and in
the newest of which nine-tenths of the fossils agree with species
still inhabiting the neighbouring sea. It is in the Post-Tertiary
strata, where all the shells agree with species now living, that
we have discovered the first or earliest known remains of man
associated with the bones of quadrupeds, some of which are of
extinct species.

In thus passing from the older to the newer members of the
Tertiary system, we meet with many chasms, but none which
separate entirely, by a broad line of demarcation, one state of
the organic world from another. There are no signs of an abrupt
termination of one fauna and flora, and the starting into life of
new and wholly distinct forms. Although we are far from being
able to demonstrate geologically an insensible transition from
the Eocene to the Miocene, or even from the latter to the recent
fauna, yet the more we enlarge and perfect our general survey,
the more nearly do we approximate to such a continuous series,
and the more gradually are we conducted from times when many of
the genera and nearly all the species were extinct, to those in
which scarcely a single species flourished which we do not know
to exist at present. Dr. A. Philippi, indeed, after an elaborate
comparison of the fossil tertiary shells of Sicily with those now
living in the Mediterranean, announced, as the result of his
examination, that there are strata in that island which attest a
very gradual passage from a period when only thirteen in a
hundred of the shells were like the species now living in the
sea, to an era when the recent species had attained a proportion
of ninety-five in a hundred. There is, therefore, evidence, he
says, in Sicily of this revolution in the animate world having
been effected 'without the intervention of any convulsion or
abrupt changes, certain species having from time to time died out
and others having been introduced, until at length the existing
fauna was elaborated.'

In no part of Europe is the absence of all signs of man or his
works, in strata of comparatively modern date, more striking than
in Sicily. In the central parts of that island we observe a lofty
table-land and hills, sometimes rising to the height of 3,000
feet, capped with a limestone, in which from 70 to 85 per cent of
the fossil testacea are specifically identical with those now
inhabiting the Mediterranean. These calcareous and other
argillaceous strata of the same age are intersected by deep
valleys which appear to have been gradually formed by denudation,
but have not varied materially in width or depth since Sicily was
first colonised by the Greeks. The limestone, moreover, which is
of so late a date in geological chronology, was quarried for
building those ancient temples of Girgenti and Syracuse, of which
the ruins carry us back to a remote era in human history. If we
are lost in conjectures when speculating on the ages required to
lift up these formations to the height of several thousand feet
above the sea, and to excavate the valleys, how much more remote
must be the era when the same rocks were gradually formed beneath
the waters!

The intense cold of the Glacial period was spoken of in the tenth
chapter. Although we have not yet succeeded in detecting proofs
of the origin of man antecedently to that epoch, we have yet
found evidence that most of the testacea, and not a few of the
quadrupeds, which preceded, were of the same species as those
which followed the extreme cold. To whatever local disturbances
this cold may have given rise in the distribution of species, it
seems to have done little in effecting their annihilation. We may
conclude therefore, from a survey of the tertiary and modern
strata, which constitute a more complete and unbroken series than
rocks of older date, that the extinction and creation of species
have been, and are, the result of a slow and gradual change in
the organic world.


UNIFORMITY OF CHANGE CONSIDERED, THIRDLY, IN REFERENCE TO
SUBTERRANEAN MOVEMENTS.--Thirdly, to pass on to the last of the
three topics before proposed for discussion, the reader will
find, in the account given in the Second Book, Vol. II., of the
earthquakes recorded in history, that certain countries have from
time immemorial, been rudely shaken again and again; while
others, comprising by far the largest part of the globe, have
remained to all appearance motionless. In the regions of
convulsion rocks have been rent asunder, the surface has been
forced up into ridges, chasms have opened, or the ground
throughout large spaces has been permanently lifted up above or
let down below its former level. In the regions of tranquillity
some areas have remained at rest, but others have been
ascertained, by a comparison of measurements made at different
periods, to have risen by an insensible motion, as in Sweden, or
to have subsided very slowly, as in Greenland. That these same
movements, whether ascending or descending, have continued for
ages in the same direction has been established by historical or
geological evidence. Thus we find on the opposite coasts of
Sweden that brackish water deposits, like those now forming in
the Baltic, occur on the eastern side, and upraised strata filled
with purely marine shells, now proper to the ocean, on the
western coast. Both of these have been lifted up to an elevation
of several hundred feet above high-water mark. The rise within
the historical period has not amounted to many yards, but the
greater extent of antecedent upheaval is proved by the occurrence
in inland spots, several hundred feet high, of deposits filled
with fossil shells of species now living either in the ocean or
the Baltic.

It must in general be more difficult to detect proofs of slow and
gradual subsidence than of elevation, but the theory which
accounts for the form of circular coral reefs and lagoon islands,
and which will be explained in the concluding chapter of this
work, will satisfy the reader that there are spaces on the globe,
several thousand miles in circumference, throughout which the
downward movement has predominated for ages, and yet the land has
never, in a single instance, gone down suddenly for several
hundred feet at once. Yet geology demonstrates that the
persistency of subterranean movements in one direction has not
been perpetual throughout all past time. There have been great
oscillations of level, by which a surface of dry land has been
submerged to a depth of several thousand feet, and then at a
period long subsequent raised again and made to emerge. Nor have
the regions now motionless been always at rest; and some of those
which are at present the theatres of reiterated earthquakes have
formerly enjoyed a long continuance of tranquillity. But,
although disturbances have ceased after having long prevailed, or
have recommenced after a suspension for ages, there has been no
universal disruption of the earth's crust or desolation of the
surface since times the most remote. The non-occurrence of such a
general convulsion is proved by the perfect horizontality now
retained by some of the most ancient fossiliferous strata
throughout wide areas.

That the subterranean forces have visited different parts of the
globe at successive periods is inferred chiefly from the
unconformability of strata belonging to groups of different ages.
Thus, for example, on the borders of Wales and Shropshire, we
find the slaty beds of the ancient Silurian system inclined and
vertical, while the beds of the overlying carboniferous shale and
sandstone are horizontal. All are agreed that in such a case the
older set of strata had suffered great disturbance before the
deposition of the newer or carboniferous beds, and that these
last have never since been violently fractured, nor have ever
been bent into folds, whether by sudden or continuous lateral
pressure. On the other hand, the more ancient or Silurian group
suffered only a local derangement, and neither in Wales nor
elsewhere are all the rocks of that age found to be curved or
vertical.

In various parts of Europe, for example, and particularly near
Lake Wener in the south of Sweden, and in many parts of Russia,
the Silurian strata maintain the most perfect horizontality; and
a similar observation may be made respecting limestones and
shales of like antiquity in the great lake district of Canada and
the United States. These older rocks are still as flat and
horizontal as when first formed; yet, since their origin, not
only have most of the actual mountain-chains been uplifted, but
some of the very rocks of which those, mountains are composed
have been formed, some of them by igneous and others by aqueous
action.

It would be easy to multiply instances of similar
unconformability in formations of other ages; but a few more will
suffice. The carboniferous rocks before alluded to as horizontal
on the borders of Wales are vertical in the Mendip hills in
Somersetshire, where the overlying beds of the New Red Sandstone
are horizontal. Again, in the Wolds of Yorkshire the last-
mentioned sandstone supports on its curved and inclined beds the
horizontal Chalk. The Chalk again is vertical on the flanks of
the Pyrenees, and the tertiary strata repose unconformably upon
it.