but by a change from dry land to the bottom of the sea, although our
knowledge of them is still so imperfect, that we cannot hazard a
probable conjecture respecting the numbers of these changes, whether
they commence at the same or at different periods in the various
quarters of the world, and whether they are local or universal.
These changes appear neither sudden nor violent, such as we consider
revolutions of the earth, but at all times proceed with silent and
regular steps, and depend upon similar causes, concealed it is true
from us, such as the universal retreat of the waters from their
original height to the present bed of the ocean. We do not belong to
those geologists who divert the world from its axis for the purpose
of explaining the inequalities of its surface, at whose command the
Earth sometimes opens her bosom to engulf the sea, and at other times
the floodgates of Heaven are lifted up to pour down another ocean.
He who reflects on the devastation caused by earthquakes, inundations
and the fall of mountains, even though they are merely local
appearances confined to particular quarters, cannot help putting
the question to himself, how the order, regularity and connection
exhibited by strata of rocks, could in any measure exist, if the same
or similar accidents had happened throughout the whole world, and
if mechanical power had operated with such energy, and to such an
extent? All our knowledge of the structure of the earth, and of the
existence of its inhabitants, declares rather a quiet uninterrupted
and continually progressive advancement in its formation and
development.
In the lapse of geological epochs, we observe a gradation of rock
formations following one another, in which the latter, however
remotely connected, still appear sufficiently similar to the earlier
to indicate a common origin, till they at length terminate in simple
formations, resembling those which are presently taking place. When
the precipitates were exhausted, and the structure was completed,
nay, even earlier, its destruction commenced; not that violent
destruction by which lofty mountains are torn asunder and levelled,
no uproar of nature, no gigantic struggle of the elements, such as
we commonly conceive, but a decomposition of the strata of rocks
to a greater or less depth, caused partly by chemical, partly by
mechanical, but slow operating powers, what they wanted in intensity
being compensated by the endurance of their operation. According
to the common law of nature, deficiency of power is supplied by
duration of time; for, of all the oracles which have been consulted
concerning the formation of the earth, there is no one which can
make such important revelations to us as the oracle of the age of
mountains. These operations at the earth’s surface generally appear
to have produced its present figure, and to have designed it for the
habitation of numerous organic beings. This appears as early as a
suitable element occurred; first, in water, then in land animals;
and, like the formation of rocks, we observe a regular succession of
organic formations, the later always descending from the earlier,
down to the present inhabitants of the earth, and to the last created
being who was to exercise dominion over them. But here occurs this
important distinction: the organic world with youthful vigour renews
itself daily, and decomposes its materials only to reunite them by
fresh combinations in uninterrupted succession; while the powers of
the inorganic world appear almost extinguished. Though this course of
nature is manifest to our own observation, her resources and progress
are, on the contrary, more concealed; and we can hardly lift the veil
which conceals her, unless we follow Bacon’s advice, Turn back from
rash theories, and follow observation and experience.
We have hitherto endeavoured to shew that incontrovertible geognostic
facts indicate an alternate rising and falling of the water which
covered the earth’s surface, but that they were not of a kind to
justify the notion of violent revolutions, or of sudden and universal
eruptions of the sea; and that, therefore, such deluges as the Mosaic
deluge, recorded in the traditions of nations, were not revolutions
of this description. If, according to the supposition of Cuvier, the
earth’s surface inhabited at the commencement of the latter deluge
has become the present bed of the sea, and the former bed of the
sea has become the present dry land, then, according to the present
state of geography, _though only conjectural_, we should be able
to point out such portions of the earth as were overwhelmed by the
catastrophe; and yet we have never heard that any one has hazarded
such an experiment. In the constitution of the present habitable
globe, we find no proofs remaining of such a revolution.
Among these revolutions of nature, we never reckon common
inundations, such as take place at present from water overflowing its
boundaries, though these also may produce devastation whose effects
remain visible for an hundred years. But, in mountainous districts,
another kind of aqueous eruption makes its appearance, and may be
classed along with the traditions of a deluge. We very frequently,
for instance, observe the valleys of high mountains forming a range
of basins separated from one another by shorter or longer defiles,
and opening through the last defile into a wider valley, or a marsh.
The shape of these basins, or cauldrons, commonly lying above one
another like so many stories, and the level surface of their water,
leave no doubt of their being once enclosed lakes which were formerly
blocked up by the barriers of the defiles, and which flowed towards
the level country, as soon as the defiles were broken down by the
waters. If no kind of historical monuments in the west of Europe
bears evidence of those events, which, at least on a small scale,
occur in our own times, this intimates that it was inhabited, not by
an original population, but by a foreign or modern race of people;
whereas those revolutions extended to remote antiquity. The numerous
masses of rock found on both sides of the Alps to the height of
4000 feet, as well as in the plains of the north of Europe, at a
great distance from their original position, and concerning whose
coming hither so much light has lately been thrown by Messrs Buch
and Escher, are a very probable proof of these debacles; while every
circumstance renders it evident that these blocks were swept along
by the currents thus created, to the place where they are now found.
The Greek writers have also preserved accounts of such revolutions,
which, although not unquestionably authenticated, are yet stamped
with the impress of historical testimony. Herodotus has the following
passages directly relative to the country where the Greeks place
their second or Deucalionic deluge. “Thessaly must formerly have
been an inland sea, surrounded by high mountains. On the east it was
bounded by Pelios and Ossa, whose bases were united; on the north by
Olympus; on the west by Pindus; and on the south by Othrys. Thessaly
lay in the midst of these mountains in the form of a basin, into
which, in conjunction with other copious streams, the five well-known
rivers, the Peneus, the Apidanus, the Orochomenus, the Enipeus, and
the Pamisos, emptied themselves. These rivers, which are collected in
their basin from the mountains which encompass Thessaly, after their
junction under the name of Peneus, in which they lose their former
appellation, open towards the sea through a narrow valley. According
to tradition, this valley and opening did not formerly exist; so
that the rivers and the Lake Brebeis, which did not formerly bear
these names, having their confluence in this place, rendered the
whole of Thessaly an inland sea. The Thessalians affirm that Neptune
opened the valley for the passage of the river Peneus, and they may
perhaps be right. If we consider Neptune the author of earthquakes,
and consider the violent concussion of the mountains caused by them
as the work of this deity, we must, upon surveying these regions,
confess that they owe their present shape to him; for the separation
of every mountain appears to me to have been produced by some violent
commotion of the earth.” Strabo makes mention of this tradition,
which he thought worthy of belief, and accounts for the origin of the
Vale of Tempe, which is the bed of the river Peneus, and likewise for
the separation of Ossa from Olympus, by means of an earthquake[405].
In making this remark, we perceive that our theories which allow
that earthquakes are to operate in forming the surface of the earth,
have not even the merit of novelty. According to the last writer,
similar eruptions of water must have originated in the lake Copais in
Bœotia[406], in the lakes Bistonis and Aphnetis, in Thrace, and have
been accompanied with huge devastation[407]. Diodorus Siculus[408]
remembered a Samothracian tradition, according to which the Euxine
Sea was once shut up on all sides. It afterwards burst through its
mighty mound of _kyanischen_ rocks to the Hellespont, and inundated
a great part of the coast of Asia, as well as Samothracia itself. An
objection started to the possibility of such an event is, that, from
the observations of Olivier and General Andreossy, the shores of the
Black Sea are, in most places, lower than those of the Bosphorus; and
that its waters, therefore, even if they were considerably higher
than they are at present, would more readily overflow the former than
the latter. But since every rock exposed for such a length of time
is daily crumbling down, it is a question, whether the shore of the
Black Sea has undergone any alteration since that period; and we know
that the eruptions took their direction, not so much from the low
situation of the barrier, as from the nature of the rock of which it
was constructed, being influenced by the weather, and from the rock
itself being rent asunder. Be that as it may, the words with which
Diodorus commences his narrative are remarkable, when he says, the
Samothracian deluge happened earlier than those of other nations.
It at least so far preceded others, that, in the estimation of the
Greek historian, independent of the deluges of Ogyges and Deucalion,
similar natural occurrences more or less authenticated were received
as historical facts.
Finally, the effects produced by the bursting of lakes or debacles
do not appear to be out of proportion to the devastation mentioned
by the traditions of nations. To abide by our former example,
floods which could carry along with them masses of rock of 50,000
cubic feet, were in a situation to bury a whole people; and the few
individuals who might be preserved would undoubtedly have handed
down the memory of such an event to remote posterity. Other deluges
may have arisen from other causes, at a time when, as is shewn by
numerous vestiges, lakes and rivers had a much greater elevation
than at present; and, therefore, every overflowing of them must have
produced greater and more extensive ravages.
From these last local eruptions of water, that is, from single
limited districts, arose the mechanical precipitates known under the
denomination of Alluvial Soil. Their situation, as the uppermost
covering of the earth, as well as their origin, which takes place
beneath our own observation, furnishes evidence of their being the
most recent mineral formations; and it follows from their nature and
connection that they were not produced by chemical means, but removed
by the mechanical force of water. Since they, among other things,
contain prostrate forests, and abundant remains of land animals, we
conclude that they did not originate in the bed of the sea, but were
floated and deposited upon the dry land by an overflow of land water.
How is it conceivable that these precipitates have been covered by
the ocean, since their deposition, and have, by means of an opposite
change, become the dry land they are at present; and yet it must have
been so, if they are to be considered as intimations of the Mosaic
deluge.
The view now given, which is that of Henger in his Beiträge, is also
advocated by other naturalists, and has lately been brought forward
in an interesting manner in the Edinburgh Philosophical Journal[409].
We have been frequently requested to give the two views, in regard
to the universal deluge, namely, that which maintains that it is
proved by an appeal to the phenomena of the mineral kingdom; the
other, which affirms that that great event has left no traces of its
existence on the surface or in the interior of the earth. M. Cuvier’s
Essay, and Professor Buckland’s Reliquiæ, are the best authorities
for the first opinion; while numerous writers have advocated the
second.
NOTE, p. 244.
ON THE ACTION OF RUNNING WATERS.
A very great degree of power has been attributed to the waters
which move at the surface of the earth, or in its interior. Many
geologists have advanced the opinion, that they have scooped out the
channels and even the valleys in which they flow, and formed the
cliffs whose feet they wash; and many philosophers, naturalists and
even geologists, still support this opinion, not only in some of its
applications, but even in its whole extent.
In order to appreciate it, it is sufficient to observe with care the
different modes of action of water set in motion by different causes,
and the changes which it has operated upon the rocks and deposits
upon which it has acted, from the most remote times to which history
may reach.
We must, in the first place, successively examine the different sorts
of action of the principal masses of water which are in motion at
the surface of the earth, that is to say, the action of torrents, of
rivers, of currents of the sea, or of great lakes, and that of waves.
We shall afterwards see what consequences are to be deduced from
these observations.
1. _Action of Torrents._
_Torrents_ have a true degrading and _scooping_ action upon the
earth’s surface, but, by the necessary consequence of the sense
which we attach to the word, this action cannot be exercised upon
spaces of great extent, for a torrent is a water-course which has a
great declivity. Now, on account of the little height which the most
elevated summits of the globe have in comparison with the extent
of its surface, this action cannot be very extensive; it can only,
therefore, produce short and narrow ravines. This action, as all who
have visited high mountain chains may have seen, is only often local
and instantaneous; it presents no remarkable effect but upon the
heaps of debris which cover the declivities of the mountains, and on
broken rocks, partially disintegrated by other causes, and lastly on
moveable deposits. The results of this action contribute to confine
it within narrower limits still, by heaping up at the mouths of
torrents in the valleys or plains, the debris carried down by these
torrents. The elevation of the soil, which necessarily follows from
the accumulation of these debris, diminishes with the declivity, the
rapidity, and consequently the power of these water-courses.
Great masses of water moving rapidly, have a marked transporting
power. Striking examples of this power have but too often been
seen in Holland, by the breaking down of the dikes, and in Alpine
mountains, in consequence of extraordinary rains during tempests,
or from the rupture of some of the natural barriers of lakes. In
these latter times (in 1818), the Vallée de Bagne experienced the
terrible effects of this devastating power. Masses of ice having
fallen towards the upper part of this valley, and accumulated
there, raised a dike sufficiently compact and strong to block up
the course of the Dranse. The waters of this river, rapid and pent
up in certain parts of its course, as are all those of the high
Alps, accumulated above this barrier of ice, and formed a lake which
attained, at its maximum, 130 metres of mean breadth, from 3000 to
4000 metres of length, and 36 of mean depth, and consequently a
volume of water estimated at about 29,000,000 cubic metres. Although,
by means of operations conducted with equal skill and courage,
about the third part of this volume was let off without danger, the
remaining part having suddenly broken through the barrier of ice,
was precipitated with an almost unexampled impetuosity of 11 metres
in the second, into the Vallée de Bagne. In the first part of its
course, and in the space of half an hour which the mass of water took
in traversing a league, it carried away trees, dwellings, enormous
masses of debris, and rocks _already separated from their mass_, as
M. Escher, expressly says; it covered all the broad parts of the
valley with rubbish, pebbles and sand, and carried the remainder of
the substances which it had swept away, as well to the extremity
of the valley, towards Martigny, as into the bed of the Rhone. The
mass of water took an hour and a half in rushing from the glacier to
Martigny. The same event took place from the same cause, and with
nearly similar results, in 1595.
Torrents may therefore scoop out ravines in certain formations, and
produce effects which appear considerable, because we judge of them
by comparison with our own feeble means. But how diminutive and
circumscribed are these changes produced in the configuration of
the globe, compared with the long and broad valleys which furrow in
vast numbers the immense surface of the earth, and to the formation
of which neither the torrents nor great rivers which exist at the
present day have in any way contributed, as we shall presently
demonstrate.
2. _Action of Rivers._
The action of _rivers_ must be examined under two very different
circumstances, or at two different parts of their course.
_First_, When they are compressed between mountains, whether at no
great distance from their source, or even at the middle of their
course.
_Secondly_, When they have reached broad valleys, whose declivity is
slight, or plains which commonly surround their mouth.
In the first case, these rivers partake of the impetuosity and power
of torrents. They often run with rapidity, and in great quantity, at
the bottom of narrow and deep valleys: they are as it were inclosed
in channels, whose vertical walls appear as if cut by art. The first
idea which presents itself to all who have seen these appearances
for the first time, and who are satisfied with first impressions,
is, that these streams, which are pretty powerful and always very
impetuous, have dug these deep grooves; and if sometimes the hardness
of the rocks and the height of the precipices which form their
sides, appear too great for those small streams that meander at
their feet, what cannot be attributed to their immediate power is
attributed to the continued action of time.
Without examining how long a series of ages it would be necessary
to admit, before the rivers which we have mentioned above, and the
water-courses encased in the deep valleys of the Alps, Pyrenees,
Jura, Grampians, &c. could have scooped their valleys, on which their
present action is so slow that no one has yet been able to estimate
it; without examining if this long series of ages agrees with the
phenomena, which preclude our attributing so remote an antiquity
to the actual state of the earth’s surface, a question of too much
importance to be treated indirectly; it will be sufficient to mention
here four sorts of observations, in order to be persuaded, or at
least to suspect, that the present rivers, even supposing them ten
times the size that they are, could not have scooped out the deep
channels at the bottom of which they run.
1. We must recur to the period when the ranges of hills which border
the present valleys were not as yet scooped out, but were united in
such a manner as not to leave any hollow between them, or merely a
slight original depression.
This shallowness of the valley would be accompanied with an
inconsiderable slope of its bottom. If, then, we suppose the same
mass of water, it must run with less quickness, and consequently
with much less power; and yet a very great force must be attributed
to it, before it could have had the power of removing a portion of
rock nearly represented by a recumbent triangular prism, having often
500 metres of breadth by a sometimes equal and often much greater
vertical thickness. If, in order to get rid of this difficulty, we
admit a volume of water incomparably larger than the present volume
of the rivers to which so great effects are attributed, we must admit
much more elevated and more extended mountains, to give rise to so
great a volume of water.
Were we only detained by this hypothesis, and did not direct
observation oppose itself to the admission of this disaggregating
power and its effect, we might pass it over; but two other
observations render the hypothesis inadmissible.
2. Historical records equally concur to prove that the rivers
possessed of the greatest power which can be attributed to them, have
no appreciable corroding action upon the rocks on which they move.
No one has maintained that the greater number of the cascades,
cataracts, or rapids, long known and mentioned on account of their
celebrity, have disappeared or have even sensibly diminished, nor
consequently that the natural dike which the water had encountered
in its course, has been worn or even completely disrupted. We do
not find that cascades have changed into cataracts, and these again
into rapids. The cataracts of the Nile have been spoken of from time
immemorial, as always opposing an obstacle to the navigation of that
river; the same is the case with those of the Danube, of the fall of
the Rhine at Schaffhausen, &c. The famous cascades of the Alps and
Pyrenees have been cited ever since writing was in use; and among all
these examples we can scarcely find two or three cascades that have
been lowered, or cataracts reduced in their level.
The only cascade which we can point out as having really diminished
in height, is that of Tungasca in Siberia. We do not, however, assert
but that there may be others. So many causes different from those
of erosion may concur to lower a cascade, or even make it disappear
almost entirely, that we are rather astonished at the small number
of examples mentioned, than embarrassed by the objections which
these examples might present to the opinion which we are defending:
for the fall of a part of the rock which forms the cliff from which
the cascade is precipitated; an abundant accumulation of debris at
the foot of the cliff; a real destruction of the softer deposits,
forming part of the strata of the mountain from which they fall, are
sufficient causes for changing the height of waterfalls. These causes
must present themselves pretty frequently; but how different is their
action from that of erosion? This, if it existed, would extend from
the source of the river to its mouth, and would have a considerable
influence upon the configuration of the earth’s surface. Those which
we have mentioned have, on the contrary, an action so limited and so
local, as to be scarcely appreciable.