I agree, therefore, with MM. Deluc and Dolomieu, in thinking, that
if any thing in geology be established, it is, that the surface of
our globe has undergone a great and sudden revolution, the date of
which cannot be referred to a much earlier period than five or six
thousand years ago; that this revolution overwhelmed and caused to
disappear the countries which were previously inhabited by man, and
the species of animals now best known; that, on the other hand, it
laid dry the bottom of the last sea, and formed of it the countries
which are at the present day inhabited; that it is since the
occurrence of this revolution that the small number of individuals
dispersed by it have spread and propagated over the newly exposed
lands, and, consequently, that it is since this epoch only, that
human societies have assumed a progressive march, that they have
formed establishments, raised monuments, collected natural facts, and
invented scientific systems.
But the countries which are at present inhabited, and which the last
revolution laid dry, had already been previously inhabited, if not
by men, at least by land animals, and, therefore, one preceding
revolution at least had put them under water; and if we may judge by
the different orders of animals the remains of which are observed in
them, they had perhaps been subjected to two or three irruptions of
the sea.
_Further Researches to be made in Geology._
These alternations now appear to me to form the problem in geology
that it is of most importance to solve, or rather to define and
circumscribe within due limits; for, in order to resolve it
satisfactorily, it would be necessary to discover the cause of these
events,--an undertaking which presents a difficulty of quite a
different kind.
I repeat it, we see pretty clearly what is going on at the surface
of the continents in their present state; we have formed a tolerable
conception of the uniform progress and regular succession of the
primitive formations, but the study of the secondary formations has
been little more than merely commenced. That wonderful series of
unknown zoophytes and marine mollusca, succeeded by reptiles and
fresh-water fishes equally unknown; and these again replaced, in
their turn, by other zoophytes and mollusca, more nearly related
to those of the present day; those land animals, and those equally
unknown fresh water mollusca and other animals which next occupied
the surface, to be again displaced but by mollusca and other animals
similar to those of our present seas; the relations of these
diversified beings to the plants the remains of which accompany
theirs, the connection of these two kingdoms with the mineral
strata in which they are deposited; the greater or less uniformity
existing between these different orders of beings in the different
basins;--these are phenomena which appear to me imperiously to demand
the attention of philosophers.
Rendered interesting by the variety of the products of the partial
or general revolutions of this epoch, and by the abundance of the
various species that figure alternately on the stage, this study
is divested of the dryness of that of the primordial formations,
and does not, like it, almost necessarily launch into hypotheses.
The facts are so direct, so curious, and so evident, that they are
sufficient, so to speak, to satisfy the most ardent imagination;
and the conclusions to which they lead from time to time, however
scrupulous the observer may be, having nothing vague in them, are
equally free of any thing arbitrary. In fine, it is in those events
that approach nearer to our own times, that we may hope to find some
traces of more ancient events, and of their causes; if, indeed, after
so many fruitless attempts as have been already made, one may be
permitted to flatter himself with such a hope.
These ideas have haunted, I may almost say have tormented me, during
my researches among fossil bones, the results of which I have
lately presented to the public; researches which embrace but a very
small part of those phenomena of the age preceding the last general
revolution of the globe, and which are yet intimately connected with
all the others. It was almost impossible that the desire should not
arise of investigating the general mass of these phenomena, at least
as they occur in a limited space around us. My excellent friend, M.
Brongniart, in whose mind other studies excited the same desire,
had the complaisance to associate me with himself in the task; and
it is thus that we have laid the first foundations of our labours
upon the environs of Paris. But this work, while it still bears my
name, has become almost entirely that of my friend, from the infinite
attention which he has bestowed, since the first conception of our
plan, and since our journeys, upon the profound investigation of
the objects, and the perfecting and arranging of the whole. I have
placed it, with M. Brongniart’s consent, in the second part of my
“Recherches,” in that in which I treat of the fossil bones of our
neighbourhood. Although apparently relating only to a rather limited
extent of country, it affords numerous results, which are applicable
to geology in general, and, in this point of view, it may be
considered as intimately connected with the present discourse; at the
same time, that it is, without a doubt, one of the best ornaments of
my work[244].
In it there is presented the history of the most recent changes
that have taken place in a particular basin, and it descends so
far as the Chalk formation, the extent of which over the globe is
vastly more considerable than that of the materials of the basin
of Paris. The chalk, which has been considered so modern, is thus
found to be advanced in antiquity among the ages of the great period
preceding the last catastrophe. It forms a sort of limit between the
most recent formations, those to which the name of _Tertiary_ may
be reserved, and the formations which are named _Secondary_, which
have been deposited before the Chalk, but after the Primitive and
Transition formations.
_Recapitulation of the Observations upon the Succession of the
Tertiary Formations._
The most superficial strata, those deposits of mud and clayey sand,
mixed with rolled pebbles, that have been transported from distant
countries, and filled with bones of land animals, the species of
which are for the most part unknown, or at least foreign to the
country in which they are found, seem especially to have covered
all the plains, filled the bottom of all the caverns, and choked up
all the fissures of rocks that have come in their way. Described
with particular care by Mr Buckland, under the name of _diluvium_,
and very different from those other beds equally consisting of
transported matters, continually deposited by torrents and rivers,
which contain only bones of animals that still live in the country,
and distinguished by the name of _alluvium_, the former are now
considered by all geologists as exhibiting the most obvious proof of
the immense inundation which has been the last of the catastrophes of
our globe[245].
Between this diluvium and the chalk, are the formations alternately
filled with fresh water and salt water productions, which mark the
irruptions and retreatings of the sea, to which this part of the
globe has been subjected, since the deposition of the chalk-strata:
first, marls and buhrstones, or cavernous quartz, filled with
fresh-water shells, similar to those of our marshes and pools; under
them marls, sandstones, and limestones, all the shells of which are
marine, such as oysters, &c.
At a greater depth are found fresh water formations of an older date,
and particularly those famous gypsum deposits of the neighbourhood
of Paris, which have afforded so much facility in ornamenting the
buildings of that great city, and in which we have discovered whole
genera of land-animals, of which no traces had been elsewhere
perceived.
They rest upon those not less remarkable beds of limestone, of
which our capital is built, in the more or less compact texture of
which the patience and sagacity of our naturalists, and of several
ardent collectors, have already detected more than 800 species of
shells, all of them marine, but the greater part unknown in the
presently-existing sea. They also contain only bones of fishes, and
of cetacea and other marine mammifera.
Under this marine limestone there is another fresh water deposit,
formed of clay, in which there are interposed large beds of lignite
(brown coal), or that sort of fossil-coal which is of more recent
origin than the common or black coal. Among shells, which are always
of fresh water origin, there are also found bones in the deposit;
but, what is remarkable, bones of reptiles, and not of mammifera. It
is filled with crocodiles and tortoises, but the genera of extinct
mammifera which the gypsum contains, are not found in it: they
evidently did not exist in the country when these clays and lignites
were formed.
This fresh water formation, the oldest which has been distinguished
in our neighbourhood, and which supports all the formations which we
have just enumerated, is itself supported and embraced on all sides
by the chalk, an immense formation, both as to thickness and extent,
which shews itself in very distant countries, such as Pomerania and
Poland; but which, in our vicinity, reigns with a sort of continuity
in Berri, Champagne, Picardy, Upper Normandy, and a part of England,
and thus forms a great circle, or rather a great basin, in which the
deposits of which we have been speaking are contained, but of which
they also cover the edges in the places where they were less elevated.
In fact, it is not in our basin only that these various formations
have been deposited. In the other countries where the surface of
the chalk presented similar cavities for them; in those even where
there was no chalk, and where the older formations alone presented
themselves as supports, circumstances often led to the formation
of deposits more or less similar to ours, and containing the same
organic bodies.
Our formations containing fresh-water shells, have been seen in
England, in Spain, and even so far as the confines of Poland.
The marine shells interposed between them, have been found along the
whole course of the Appenines.
Some of the quadrupeds of our gypsum deposits, our palæotheria, for
example, have also left their bones in certain gypseous formations of
the Velai, and in the molasse quarries of the south of France.
Thus the partial revolutions which have taken place in our
neighbourhood, between the period of the chalk and that of the great
inundation, and during which the sea threw itself upon our districts
or retired from them, had also taken place in a multitude of other
countries. It seems as if the globe had undergone a long series
of changes by which variations were produced, probably in close
succession, as the deposits which they have left nowhere shew much
thickness or solidity. The chalk has been produced by a more tranquil
and more continuous sea; it contains only marine productions, among
which there are, however, some very remarkable vertebrate animals,
but all of the class of reptiles and fishes; large tortoises, vast
lizards, and other similar animals.
The formations anterior to the chalk, and in the hollows of which the
chalk is itself deposited, as the formations of our neighbourhood
are in its hollows, form a great part of Germany and England; and the
efforts which the naturalists of these two countries have recently
made according with ours, and proceeding upon the same principles,
combined with those which had been previously tried by the school of
Werner, will soon leave nothing to be desired with respect to our
knowledge of them. Messrs de Humboldt and de Bonnard in France and
Germany, and Messrs Buckland and Conybeare in England, have furnished
the most complete and most instructive accounts of them.
* * * * *
The subjoined table, in which not only the secondary formations have
been arranged, but the whole series of strata, from the oldest known
to the most modern and most superficial, has been politely furnished
me by M. de Humboldt, to adorn my work. It may be considered as an
epitome of the labours of geologists up to the present period[246].
_TABLE of Geological Formations in the order of their superposition._
By M. Al. de Humboldt.
+---------------------------------------------+--
| Alluvial Deposits. |
+---------------------------------------------+
| Lacustrine Formation with Buhrstones. |
+---------------------------------------------+
| Fountainbleau sandstone and sand. |
+---------------------------------------------+
| Gypsum with bones. Siliceous Limestone. | _Tertiary_
+---------------------------------------------+
| Coarse Limestone. |_Formations._
| (London Clay.) |
+---------------------------------------------+
| Tertiary sandstone with lignites. |
+---------------------------------------------+
| (Plastic clay,--Molasse,--Nagelfluhe.) |
+----------+---------------------------------------------+----------+
| white. |
| Chalk. tufaceous. _Ananchites._ |
| chloritic. |
+-----+--------------------------------------------------+----------+
|Green sand. |
|Weald clay. (Secondary Sandstone with _lignites_.)| _Secondary_
|Iron Sand. |
+-----+--------------------------------------------------+----------+
| _Ammonites._ Jura Limestone. Slaty beds with fishes and |
| _Planulites._ crustacea. |
+-----------------------------------------+Coral rag. |
| Quadersandstein, or white sandstone, |Dive clay. |
| sometimes above the lias. |Oolites and Caen |
+-----------------------------------------+ limestone. |
| Muschelkalk. |Marly or calcareous lias |
| _Ammonites nodosus._ | with _Gryphæa arcuata_.|
+-----------------------------------------+-------------------------+
| Marls with fibrous gypsum. Saliferous variegated sandstone. |
| Arenaceous beds. |
+-------------------------------------------------------------------+
| _Productus aculeatus._ |
| Magnesian limestone. Zechstein. (Alpine limestone.) |
| Copper slate. |
+-------------+-----------------------------------------------------+
|Quartziferous| Co-ordinate formations of porphyry, |
|Porphyry. | red sandstone, and coal. | _Formations._
+-------------+-----------------------------------------------------+
| _Transition Formations._ |
| |
| Slates with Lydian-stone, greywacke, diorites, euphotides. |
| Limestones with orthoceratis, trilobites and euomphalites. |
+-------------------------------------------------------------------+
| _Primitive Formations._ |
| |
| Clayslates (Thonschiefer). |
| Micaslates. |
| Gneiss. |
| Granites. |
+-------------------------------------------------------------------+
Under the chalk are found deposits of green sand, of which its lower
strata contains some organic remains. Beneath this are ferruginous
sands. In many countries both of these deposits are agglutinated into
beds of sandstone, in which lignites, amber, and remains of reptiles,
are also observed.
Under this, we find the great mass of strata which compose the Jura
chain, and that of the mountains by which it is continued into Suabia
and Franconia, the principal ridges of the Apennines, and multitudes
of beds in France and England. It consists of limestone-schists,
rich in fishes and crustacea; vast beds of oolites, or of a granular
limestone; grey marly limestones, with pyrites, characterised by
the presence of ammonites, of oysters with recurvate valves, named
Gryphææ, and of reptiles, which are remarkable on account of their
forms and structures.
Large beds of sand and sandstone, often presenting vegetable
impressions, support all these Jura deposits, and are themselves
supported by a limestone, the innumerable shells and zoophytes
contained in which induced Werner to give it the much too general
name of _Shell-limestone_, and which is separated by other beds of
sandstone, of the kind denominated _variegated_ sandstone, from a
still older limestone, which has been not less improperly called
_Alpine limestone_, because it composes the High Alps of the Tyrol;
but which also shews itself at the surface in the eastern provinces
of France, and in the whole southern part of Germany.
In this shell-limestone are deposited great masses of gypsum and rich
beds of salt; and under it are found the thin beds of copper-slates
so rich in fishes, among which there are also fresh-water reptiles.
The copper-slate rests upon a red sandstone, to the epoch of which
belong those famous deposits of coal, which supply the present
inhabitants of the civilized countries of Europe with fuel, and are
the remains of the first vegetable productions with which the face
of the globe was adorned. We learn from the trunks of ferns, whose
impressions they have preserved, how different these ancient forests
have been from ours.
We then quickly come to those transition formations, in which
primeval nature, nature dead and purely mineral, seems to have
disputed the empire with organising nature. Black limestones, and
schists which present only crustacea and shells of kinds now extinct,
alternate with remains of primitive formations, and announce our
having arrived at those formations, the oldest with which we are
acquainted, those ancient foundations of the present envelop of the
globe, the marbles and primitive slates, the gneisses, and, lastly,
the granites.
Such is the precise enumeration of the successive masses with which
nature has enveloped the globe. The positive geological information
presented by it, has been obtained, by combining the knowledge
furnished by mineralogy with that presented by the sciences connected
with organic existence. This order, so new and so interesting
in facts, has only been acquired by geology, since it preferred
positive knowledge, furnished by observation, to fanciful systems,
contradictory conjectures regarding the first origin of the globe,
and all those phenomena, which, having no resemblance to what
actually takes place in nature, could neither find in it, for their
explanation, materials nor touchstone. A few years ago, the greater
number of geologists might have been compared to historians, who,
in writing the history of France, should have interested themselves
only about the events which had taken place among the Gauls before
the time of Julius Cesar. In composing their romances, however, these
historians would have taken advantage of their knowledge of posterior
facts; and the geologists of whom I speak, absolutely neglected the
posterior facts, which could alone have reflected some light upon the
darkness of preceding times.
_Enumeration of the Fossil Animals recognised by the Author._
In concluding this discourse, there only remains for me now to
present the result of my own researches, or, in other words, a
general account of my great work. I shall enumerate the animals which
I have discovered, in the inverse order of that which I have followed
in my enumeration of the formations. By proceeding deeper and deeper
into the series of strata, I there rose in the series of epochs. I
shall now take the oldest formations,--make known the animals which
they contain,--and, passing from one epoch to another, point out
those which successively make their appearance in proportion as we
approach the present time.
We have seen that zoophytes, mollusca, and certain crustacea, begin
to appear in the Transition formations; perhaps there may even at
that period be bones and skeletons of fishes; but we do not by any
means observe at so early a period remains of animals which live on
land, and respire air in its ordinary state.
The great beds of coal, and the trunks of palms and ferns of which
they preserve the impressions, although they afford evidence of the
existence of dry land, and of a vegetation no longer confined to the
waters, do not yet shew bones of quadrupeds, not even of oviparous
quadrupeds.
It is only a little above this, in the bituminous copper-slates, that
we see the first traces of them; and, what is very remarkable, the
first quadrupeds are reptiles of the family of lizards, very much
resembling the large monitors which live at the present day in the
torrid zone. Several individuals of this kind have been found in the
mines of Thuringia[247], among innumerable fishes of a genus now
unknown, but which, from its relations to the genera of our days,
appears to have lived in fresh water. Every body knows that the
monitors are also fresh water animals.
A little higher is the limestone called Alpine, and resting upon it
the shell-limestone, so rich in entrochites and encrinites, which
forms the basis of a great part of Germany and Lorraine.
In it have been found skeletons of a very large sea-tortoise, the
shells of which might have been from six to eight feet in length; and
those of another oviparous quadruped of the family of lizards, of a
large size, and with a very sharp muzzle[248].
Rising still through sandstones, which present only vegetable
impressions of large arundinaceæ, bamboos, palms, and other
monocotyledonous plants, we come to the different strata of the
deposit which has been named the Jura limestone, on account of its
forming the principal nucleus of that chain of mountains.
It is here that the class of Reptiles assumes its full development,
and shews itself under the most varied forms and gigantic sizes.
The middle part, which is composed of oolites and lias, or of grey
sandstone containing gryphites, contains the remains of two genera,
the most extraordinary of all, which have combined the characters of
the class of oviparous quadrupeds with organs of motion similar to
those of the cetacea.
The _ichthyosaurus_[249], discovered by Sir Everard Home, has the
head of a lizard, but prolonged into an attenuated muzzle, armed with
conical and pointed teeth; enormous eyes, the sclerotica of which is
strengthened by a frame consisting of bony pieces; a spine composed
of flat vertebræ, of a depressed circular form, and concave on both
surfaces like those of fishes; slender ribs; a sternum and clavicles
like those of lizards and ornithorynchi; a small and weak pelvis;
and four limbs, of which the humeri and femurs are short and thick,
while the other bones are flattened, and closely set like the stones
in a pavement, so as to form, when enveloped with the skin, fins of a
single piece, almost incapable of bending; analogous, in short, both
as to use and organization, to those of cetacea. These reptiles have
lived in the sea; on shore, they could only at most have crept in the
hobbling manner of seals; at the same time after they have respired
elastic air.
The remains of four species have been found:
The most extensively distributed (_I. communis_) has blunt conical
teeth; its length sometimes exceeds twenty feet.
The second (_I. platyodon_), which is at least as large as the
former, has compressed teeth, with round and bulging roots.
The third (_I. tenuirostris_), has slender and pointed teeth, and the
muzzle thin and elongated.
The fourth (_I. intermedius_), is, as its name implies, intermediate
between the last species and the common, with respect to the form of
its teeth. The two latter species do not attain half the size of the
two first.