5. Marl-slate { 5. Mergel-Schiefer or } 5. Red and green grits
{ Kupferschiefer } with copper-ore.
{ 6. White limestone with
6. Lower sandstones, and } 6. Todteliegende { gypsum and white
sands of various colours } { salt.
At the base of the system lies a band of _lower sandstone_ (No. 6) of
various colours, separating the Magnesian Limestone from the coal in
Yorkshire and Durham; sometimes associated with red marl and gypsum, but
with the same obscure relations in all these beds which usually attend
the close of one series and the commencement of another; the imbedded
plants being, in some cases, stated to be identical with those of the
Carboniferous series. In Thuringia the _Rothliegende_, or _red-lyer_, a
great deposit of red sandstone and conglomerate, associated with
porphyry, basaltic trap, and amygdaloid, lies at the base of the system.
Among the fossils of this age are the silicified trunks of Tree-ferns
(_Psaronius_), the bark of which is surrounded by dense masses of
air-roots, which often double or quadruple the diameter of the original
stem; in this respect bearing a strong resemblance to the living
arborescent ferns of New Zealand.
The marl-slate (No. 5) consists of hard calcareous shales,
marl-slates, and thin-bedded limestone, the whole nearly thirty
feet thick in Durham, and yielding many fine specimens of Ganoid and
Placoid fishes--_Palæoniscus_, _Pygopterus_, _Cœlacanthus_, and
_Platysomus_--genera which all belong to the Carboniferous system, and
which Professor King thinks probably lived at no great distance from the
shore; but the Permian species of the marl-slate of England are
identical with those of the copper-slate of Thuringia. Agassiz was the
first to point out a remarkable peculiarity in the forms of the fishes
which lived before and after this period. In most living fishes the
trunk seems to terminate in the middle of the root of the tail, whose
free margin is “homocercal” (even-tail), that is, either rounded, or, if
forked, divided into two equal lobes. In Palæoniscus, and most Palæozoic
fishes, the axis of the body is continued into the upper lobe of the
tail, which is thus rendered unsymmetrical, as in the living sharks and
sturgeons. The latter form, which Agassiz termed “heterocercal”
(unequal-tail) is only in a very general way distinctive of Palæozoic
fishes, since this asymmetry exists, though in a minor degree, in many
living genera besides those just mentioned. The compact limestone (No.
4) is rich in Polyzoa. The fossiliferous limestone (No. 3), Mr. King
considers, is a deep-water formation, from the numerous Polyzoa which it
contains. One of these, _Fenestella retiformis_, found in the Permian
rocks of England and Germany, sometimes measures eight inches in width.
Many species of Mollusca, and especially Brachiopoda, appear in the
Permian seas of this age, _Spirifera_ and _Producta_ being the most
characteristic.
Other shells now occur, which have not been observed in strata newer
than the Permian. _Strophalosia_ (Fig. 73) is abundantly represented in
the Permian rocks of Germany, Russia, and England, and much more
sparingly in the yellow magnesian limestone, accompanied by _Spirifera
undulata_, &c. _S. Schlotheimii_ is widely disseminated both in England,
Germany, and Russia, with _Lingula Credneri_, and other Palæozoic
Brachiopoda. Here also we note the first appearance of the Oyster, but
still in small numbers. _Fenestella_ represents the Polyzoa. _Schizodus_
has been found by Mr. Binney in the Upper Red Permian Marls of
Manchester; but no shells of any kind have hitherto been met with in the
Rothliegende of Lancashire, or in the Vale of Eden.
The brecciated limestone (No. 2) and the concretionary masses (No. 1)
overlying it (although Professor King has attempted to separate them)
are considered by Professor Sedgwick as different forms of the same
rock. They contain no foreign elements, but seem to be composed of
fragments of the underlying limestone, No. 3. Some of the angular masses
at Tynemouth cliff are two feet in diameter, and none of them are
water-worn.
[Illustration: Fig. 73.--Strophalosia Morrisiana.]
[Illustration: Fig. 74.--Cyrtoceras depressum.]
[Illustration: Fig. 75.--Walchia Schlotheimii.]
The crystalline or concretionary limestone (No. 1) formation is seen
upon the coast of Durham and Yorkshire, between the Wear and the Tees;
and Mr. King thinks that the character of the shells and the absence of
corals indicate a deposit formed in shallow water.
The plants also found in some of the Permian strata indicate the
neighbourhood of land. These are land species, and chiefly of genera
common in the Coal-measures. Fragments of supposed coniferous wood
(generally silicified) are occasionally met with in the Permian red beds
of many parts of England.
Among the Ferns characteristic of the period may be mentioned
_Sphenopteris dichotoma_ and _S. Artemisiæfolia_; _Pecopteris
lonchitica_ and _Neuropteris gigantea_, figured on pp. 143, 144. “If we
are,” says Lyell, “to draw a line between the Secondary and Primary
fossiliferous strata, it must be run through the middle of what was once
called the ‘New Red.’ The inferior half of this group will rank as
Primary or Palæozoic, while its upper member will form the base of the
Secondary or Mesozoic series.”[52] Among the _Equiseta_ of the Permian
formation of Saxony, Colonel Von Gutbier found _Calamites gigas_ and
sixty species of fossil plants, most of them Ferns, forty of which have
not been found elsewhere. Among these are several species of _Walchia_,
a genus of Conifers, of which an example is given in Fig. 75.
[52] “Elements of Geology,” p. 456.
[Illustration: Fig. 76.--Trigonocarpum Nöggerathii.]
In their stems, leaves, and cones, they bear some resemblance to the
_Araucarias_, which have been introduced from North America into our
pleasure-grounds during the last half-century.
Among the genera enumerated by Colonel Von Gutbier are some fruits
called _Cardiocarpon_, and _Asterophyllites_ and _Annularia_, so
characteristic of the Carboniferous age. The Lepidodendron is also
common to the Permian rocks of Saxony, Russia, and Thuringia; also the
_Nöggerathia_, a family of large trees, intermediate between Cycads
(Fig. 72) and the Conifers. The fruit of one of these is represented in
Fig 76.
PERMIAN ROCKS.--We now give a sketch of the physiognomy of the earth in
Permian times. Of what do the beds consist? What is the extent, and what
is the mineralogical constitution of the rocks deposited in the seas of
the period? The Permian formation consists of three members, which are
in descending order--
1. Upper Permian sandstone, or Grès des Vosges; 2. Magnesian Limestone,
or Zechstein; 3. Lower Red Sandstone, Marl-slate or Kupferschiefer, and
Rothliegende.
The _grès des Vosges_, usually of a red colour, and from 300 to 450 feet
thick, composes all the southern part of the Vosges Mountains, where it
forms frequent level summits, which are evidences of an ancient plain
that has been acted on by running water. It only contains a few
vegetable remains.
The _Magnesian Limestone_, Pierre de mine, or Zechstein, so called in
consequence of the numerous metalliferous deposits met with in its
diverse beds, presents in France only a few insignificant fragments; but
in Germany and England it attains the thickness of 450 feet. It is
composed of a diversified mass of Magnesian Limestone, generally of a
yellow colour, but sometimes red and brown, and bituminous clay, the
last black and fetid. The subordinate rocks consist of marl, gypsum, and
inflammable bituminous schists. The beds of marl slate are remarkable
for the numbers of peculiar fossil fishes which they contain; and from
the occurrence of small proportions of argentiferous grey copper-ore,
met with in the bituminous shales which are worked in the district of
Mansfeld, in Thuringia--the latter are called _Kupferschiefer_ in
Germany.
The _Lower Red Sandstone_, which attains a thickness of from 300 to 600
feet, is found over great part of Germany, in the Vosges, and in
England. Its fossil remains are few and rare; they include silicified
trunks of Conifers, some impressions of Ferns, and Calamites.
In England the Permian strata, to a great extent, consist of red
sandstones and marls; and the Magnesian Limestone of the northern
counties is also, though to a less degree, associated with red marls.
In Lancashire thin beds of Magnesian Limestone are interstratified with
red marls in the upper Permian strata, beneath which there are soft Red
Sandstones, estimated by Mr. Hull to be about 1,500 feet thick. These
are supposed to represent the Rothliegende, and no shells of any kind
have been found in them. The upper Permian beds, however, contain a few
Magnesian Limestone species, such as _Gervillia antiqua_, _Pleurophorus
costatus_, _Schizodus obscurus_, and some others, but all small and
dwarfed.
The coal-fields of North and South Staffordshire, Tamworth, Coalbrook
Dale, and of the Forest of Wyre, are partly bordered by Permian rocks,
which lie unconformably on the Coal-measures; as is the case, also, in
the immediate neighbourhood of Manchester, where they skirt the borders
of the main coal-field, and consist of the Lower Red Sandstone, resting
unconformably on different parts of the Coal-measures, and overlaid by
the pebble-beds of the Trias.
At Stockport the Permian strata are stated by Mr. Hull to be more than
1,500 feet thick.
In Yorkshire, Nottinghamshire, and Derbyshire, the Permian strata are
stated by Mr. Aveline to be divided into two chief groups: the
Roth-liegende, of no great thickness, and the Magnesian Limestone
series; the latter being the largest and most important member of the
Permian series in the northern counties of England. The Magnesian
Limestone consists there of two great bands, separated by marls and
sandstone, and quarried for building and for lime. In Derbyshire and
Yorkshire the magnesian limestone, under the name of Dolomite, forms an
excellent building-stone, which has been used in the construction of the
Houses of Parliament.
In the midland counties and on the borders of Wales, the Permian section
is different from that of Nottinghamshire and the North of England. The
Magnesian Limestones are absent, and the rocks consist principally of
dark-red marl, brown and red sandstones, and calcareous conglomerates
and breccias, which are almost entirely unfossiliferous. In
Warwickshire, where they rest conformably on the Coal-measures, they
occupy a very considerable tract of country, and are of very great
thickness, being estimated by Mr. Howell to be 2,000 feet thick.
In the east of England the Magnesian Limestone contains a numerous
marine fauna, but much restricted when compared with that of the
Carboniferous period. The shells of the former are all small and dwarfed
in size when compared with their congeners of Carboniferous times, when
such there are, and in this respect, and the small number of genera,
they resemble the living mollusca of the still less numerous fauna of
the Caspian Sea.
Besides the poverty and small size of the mollusca, the later strata of
the true Magnesian Limestone seem to afford strong indications that they
may have been deposited in a great inland salt-lake subject to
evaporation.
The absence of fossils in much of the formation may be partly accounted
for by its deposition in great measure from solution, and the
uncongenial nature of the waters of a salt-lake may account for the
poverty-stricken character of the whole molluscan fauna.
The red colouring-matter of the Permian sandstones and marls is
considered, by Professor Ramsay, to be due to carbonate of iron
introduced into the waters, and afterwards precipitated as peroxide
through the oxidising action of the air and the escape of the carbonic
acid which held it in solution. This circumstance of the red colour of
the Permian beds affords an indication that the red Permian strata were
deposited in inland waters unconnected with the main ocean, which waters
may have been salt or fresh as the case may be.
“The Magnesian Limestone series of the east of England may, possibly,
have been connected directly with an open sea at the commencement of the
deposition of these strata, whatever its subsequent history may have
been; for the fish of the marl strata have generically strong affinities
with those of Carboniferous age, some of which were truly marine, while
others certainly penetrated shallow lagoons bordered by peaty
flats.”[53]
[53] “On the Red Rocks of England,” by A. C. Ramsay. _Quart. Jour.
Geol. Soc._, vol. xxvii., p. 246.
There is indisputable evidence that the Permian ocean covered an immense
area of the globe. In the Permian period this ocean extended from
Ireland to the Ural mountains, and probably to Spitzbergen, with its
northern boundary defined by the Carboniferous, Devonian, Silurian, and
Igneous regions of Scotland, Scandinavia, and Northern Russia; and its
southern boundaries apparently stretching far into the south of Europe
(King). The chain of the Vosges, stretching across Rhenish Bavaria, the
Grand Duchy of Baden, as far as Saxony and Silesia, would be under
water. They would communicate with the ocean, which covered all the
midland and western counties of England and part of Russia. In other
parts of Europe the continent has varied very little since the preceding
Devonian and Carboniferous ages. In France the central plateaux would
form a great island, which extended towards the south, probably as far
as the foot of the Pyrenees; another island would consist of the mass of
Brittany. In Russia the continent would have extended itself
considerably towards the east; finally, it is probable that, at the end
of the Carboniferous period, the Belgian continent would stretch from
the Departments of the Pas-de-Calais and Du Nord, in France, and would
extend up to and beyond the Rhine.
In England, the Silurian archipelago, now filled up and occupied by
deposits of the Devonian and Carboniferous systems, would be covered
with carboniferous vegetation; dry land would now extend, almost without
interruption, from Cape Wrath to the Land’s End; but, on its eastern
shore, the great mass of the region now lying less than three degrees
west of Greenwich would, in a general sense, be under water, or form
islands rising out of the sea. Alphonse Esquiros thus eloquently closes
the chapter of his work in which he treats of this formation in England:
“We have seen seas, vast watery deserts, become populated; we have seen
the birth of the first land and its increase; ages succeeding each
other, and Nature in its progress advancing among ruins; the ancient
inhabitants of the sea, or at least their spoils, have been raised to
the summit of lofty mountains. In the midst of these vast cemeteries of
the primitive world we have met with the remains of millions of beings;
entire species sacrificed to the development of life. Here terminates
the first mass of facts constituting the infancy of the British Islands.
But great changes are still to produce themselves on this portion of the
earth’s surface.”
Having thus described the _Primary Epoch_, it may be useful, before
entering on what is termed by geologists the _Secondary Epoch_, to
glance backwards at the facts which we have had under consideration.
In this Primary period plants and animals appear for the first time
upon the surface of the cooling globe. We have said that the seas of the
epoch were then dominated by the fishes known as _Ganoids_ (from γανος,
_glitter_), from the brilliant polish of the enamelled scales which
covered their bodies, sometimes in a very complicated and fantastic
manner; the _Trilobites_ are curious Crustaceans, which appear and
altogether disappear in the Primary epoch; an immense quantity of
Mollusca, Cephalopoda, and Brachiopoda; the _Encrinites_, animals of
curious organisation, which form some of the most graceful ornaments of
our Palæontological collections.
[Illustration: Fig. 77.--Lithostrotion. (Fossil Coral.)]
But, among all these beings, those which prevailed--those which were
truly the kings of the organic world--were the Fishes, and, above all,
the _Ganoids_, which have left no animated being behind them of similar
organisation. Furnished with a sort of defensive armour, they seem to
have received from Nature this means of protection to ensure their
existence, and permit them to triumph over all the influences which
threatened them with destruction in the seas of the ancient world.
[Illustration: Fig. 78.--Rhyncholites, upper, side, and internal views.
1, Side view (Muschelkalk of Luneville); 2, Upper view (same locality);
3, Upper view (Lias of Lyme Regis); 4, Calcareous point of an under
mandible, internal view, from Luneville. (Buckland.)]
In the Primary epoch the living creation was in its infancy. No Mammals
then roamed the forests; no bird had yet displayed its wings. Without
Mammals, therefore, there was no maternal instinct; none of the soft
affections which are, with animals, as it were, the precursors of
intelligence. Without birds, also, there could be no songs in the air.
Fishes, Mollusca, and Crustacea silently ploughed their way in the
depths of the sea, and the immovable Crinoid lived there. On the land we
only find a few marsh-frequenting Reptiles, of small size--forerunners
of those monstrous Saurians which make their appearance in the Secondary
epoch.
The vegetation of the Primary epoch is chiefly of inferior organisation.
With a few plants of a higher order, that is to say, Dicotyledons,
Calamites, Sigillarias, it was the Cryptogamia (also several species of
Ferns, the Lepidodendra, Lycopodiaceæ, and the Equisetaceæ, and some
doubtfully allied forms, termed Nöggerathia), then at their maximum of
development, which formed the great mass of the vegetation.
Let us also consider, in this short analysis, that during the epoch
under consideration, what we call _climate_ may not have existed. The
same animals and the same plants then lived in the polar regions as at
the equator. Since we find, in the Primary formations of the icy regions
of Spitzbergen and Melville Islands, nearly the same fossils which we
meet with in these same rocks in the torrid zone, we must conclude that
the temperature at this epoch was uniform all over the globe, and that
the heat of the earth itself was sufficiently high to render
inappreciable the calorific influence of the sun.
During this same period the progressive cooling of the earth occasioned
frequent ruptures and dislocations of the ground; the terrestrial crust,
in opening, afforded a passage for the rocks called _igneous_, such as
granite, afterwards to the porphyries and syenites, which poured slowly
through these immense fissures, and formed mountains of granite and
porphyry, or simple clefts, which subsequently became filled with oxides
and metallic sulphides, forming what are now designated metallic veins.
The great mountain-range of Ben Nevis offers a striking example of the
first of these phenomena; through the granite base a distinct natural
section can be traced of porphyry ejected through the granite, and of
syenite through the porphyry. These geological commotions (which
occasioned, not over the whole extent of the earth, but only in certain
places, great movements of the surface) would appear to have been more
frequent at the close of the Primary epoch; during the interval which
forms the passage between the Primary and Secondary epochs; that is to
say, between the Permian and the Triassic periods. The phenomena of
eruptions, and the character of the rocks called eruptive, are treated
of in a former chapter.
[Illustration: Fig. 79. _a_, Pentacrinites Briareus, reduced; _b_, the
same from the Lias of Lyme Regis; natural size.]
The convulsions and disturbances by which the surface of the earth was
agitated did not extend, let it be noted, over the whole of its
circumference; the effects were partial and local. It would, then, be
wrong to affirm, as is asserted by many modern geologists, that the
dislocations of the crust and the agitations of the surface of the
globe extended to both hemispheres, resulting in the destruction of all
living creatures. The Fauna and Flora of the Permian period did not
differ essentially from the Fauna and Flora of the Coal-measures, which
shows that no general revolution occurred to disturb the entire globe
between these two epochs. Here, then, as in all analogous cases, it is
unnecessary to recur to any general cataclysm to explain the passage
from one epoch to another. Have we not, almost in our our own day, seen
certain species of animals die out and disappear, without the least
geological revolution? Without speaking of the Beaver, which abounded
two centuries ago on the banks of the Rhône, and in the Cévennes, which
still lived at Paris in the little river Bièvre in the middle ages, its
existence being now unknown in these latitudes, although it is still
found in America and other countries, we could cite many examples of
animals which have become extinct in times by no means remote from our
own. Such are the _Dinornis_ and the _Epyornis_, colossal birds of New
Zealand and Madagascar, and the _Dodo_, which lived in the Isle of
France in 1626. _Ursus spelæus_, _Cervus Megaceros_, _Bos primigenius_,
are species of Bear, Deer, and Ox which were contemporary with man, but
have now become extinct. In France we no longer know the gigantic
wood-stag, figured by the Romans on their monuments, and which they had
brought from England for the fine quality of its flesh. The Erymanthean
boar, so widely dispersed during the ancient historical period, no
longer exists among our living races, any more than the Crocodiles
_lacunosus_ and _laciniatus_ found by Geoffroy St.-Hilaire in the
catacombs of ancient Egypt. Many races of animals figured in the mosaics
of Palestrina, engraved and painted along with species now actually
existing, are no longer found living in our days any more than are the
Lions with curly manes, which formerly existed in Syria, and perhaps
even in Thessaly and the northern parts of Greece. From what happens in
our own time, we may infer what has taken place in times antecedent to
the appearance of man; and the idea of successive cataclysms of the
globe, must be restrained within bounds. Must we imagine a series of
geological revolutions to account for the disappearance of animals which
have evidently become extinct in a natural way? What has come to pass in
our days, it is reasonable to conclude, may have taken place in the
times anterior to the appearance of man.
[Illustration: Fig. 80.--Terebellaria ramosissima. (Recent Coral.)]