SECONDARY ROCKS.
_3. The Oolite proper._
“O Lord, how manifold are thy works! in wisdom hast thou made them
all.”—DAVID.
Proceeding with our rapid sketch of the crust of the earth and its uses,
we now leave the Lias, to enter upon a survey of the Oolite proper.
Overlying the Lias, and underlying the Wealden, we find this deposit,
which, though it occupies a comparatively narrow track in our own
country, is remarkable for the peculiarity and beauty of its fossils,
and for the commercial importance of the rocks of which it is composed.
Its name is derived from _ōŏn_, an egg, and _lithos_, a stone,[88] from
the remarkable resemblance many of the beds bear to the roe, or eggs of
a fish. A good specimen of oolite and the hard roe of a red herring are
unlike one another, mostly in the circumstance that one can be cooked,
and the other cannot. These egg-like grains are mere agglomerations of
calcareous matter, although sometimes a piece of coral, or a broken
shell, or a grain of sand, is found to be the nucleus around which these
deposits have arranged themselves. It may be as well here to say a word
upon the general character of _calcareous_ rocks, which are so largely
to engage our attention in this and a subsequent chapter. “This division
comprehends those rocks which, like chalk, are composed chiefly of lime
and carbonic acid. Shells and corals are also formed of the same
elements, with the addition of animal matter. To obtain pure lime it is
necessary to calcine these calcareous substances,—that is to say, to
expose them to heat of sufficient intensity to drive off the carbonic
acid and other volatile matter, without vitrifying or melting the lime
itself. White chalk is often pure carbonate of lime; and this rock,
although usually in a soft and earthy state, is sometimes sufficiently
solid to be used for building, and even passes into a compact stone, or
a stone of which the separate parts are so minute as not to be
distinguishable from each other by the naked eye.
“Many limestones are made up entirely of minute fragments of shells and
corals, or of calcareous sand cemented together. These last might be
called ‘calcareous sandstones;’ but that term is more properly applied
to a rock in which the grains are partly calcareous and partly
siliceous, or to quartz-ore sandstones having a cement of carbonate of
lime.
“The variety of limestones called ‘_oolite_’ is composed of numerous
small egg-like grains, resembling the roe of a fish, each of which has
usually a small fragment of sand as a nucleus, around which concentric
layers of calcareous matter have accumulated.
“Any limestone which is sufficiently hard to take a fine polish is
called _marble_. Many of these are fossiliferous; but statuary marble,
which is also called saccharine limestone, as having a texture
resembling that of loaf-sugar, is devoid of fossils, and is in many
cases a member of the metamorphic series.”[89] The geographical
distribution of this group of rocks may be traced thus:—Commencing with
the _Bill_ of Portland, (for there is no _isle_ of Portland,) it runs up
through part of Dorsetshire, Somersetshire, Gloucestershire,
Oxfordshire, Northamptonshire, part of Lincolnshire, terminating in
Yorkshire, where the lias and oolite may be seen lying conformably or in
sequence; the zone we have thus indicated being about thirty miles in
width. The following tabular arrangement will supplement this by
pointing out the divisions and subdivisions of the oolite; on which,
however, we do not intend to dwell, as our only object, in this most
preliminary treatise,—and we shall be pardoned again intruding this
thought upon our readers,—is to assist in the investigation of our
standard text-books on this science:—
OOLITE PROPER.
1. UPPER. │1. Portland stone, with underlying dirt-beds.
│2. Kimmeridge clay.
──────────┼─────────────────────────────────────────────
2. MIDDLE.│1. Coral rag.
│2. Oxford clay.
──────────┼─────────────────────────────────────────────
3. LOWER. │1. Cornbrash and Forest marble.
│2. Great Oolite and Stonesfield slate.
│3. Fuller’s earth.
│4. Inferior Oolite.—_Lyell._
In the upper oolites, it will be seen, is found the famous Portland
stone, in which are some of the most remarkable specimens of the extinct
fauna of this remote period. “They are found most plentifully in what is
locally designated the ‘dirt-bed’ of Portland—a stratum of dark
argillaceous mud, which must at one time have been the soil in which
they and other vegetables flourished, but which, by a submergence of the
land, was converted into the bottom of an estuary, over which other
strata of clay, limestone, and sand were deposited. ‘At the distance of
two feet,’ says Bakewell, ‘we find an entire change from marine strata
to strata once supporting terrestrial plants; and should any doubt arise
respecting the original place and position of these plants, there is,
over the lower dirt-bed, a stratum of fresh-water limestone; and upon
this a thicker dirt-bed, containing not only the cycadeæ, but stumps of
trees from three to seven feet in height, in an erect position, with
their roots extending beneath them. Stems of trees are found prostrate
upon the same stratum; some of them are from twenty to twenty-five feet
in length, and from one to two feet in diameter. The following section
of a cliff in Dorset exhibits very clearly proofs of the alternation
from marine strata to dry land covered with a forest, and of a
subsequent submergence of the dry land under a river or lake which
deposited fresh-water limestone.’”
[Illustration:
_a a a_, Portland stone (marine formation); _b_, Dirt-bed, consisting
of black mould and pebbles (temporary dry land); _c_, Burrstone, and
_d_, Calcareous slate (both of fresh-water formation).—_Chambers’
Geology, p._ 128.
]
From the well-known quarries in Portland, a description of which would
tempt us too far astray, have been procured the materials for St. Paul’s
Cathedral, the Reform Club, and other public buildings. A visit to
Portland, and examination of the quarries, such as we have twice paid,
is well worth the attention of any summer tourist, and will richly
repay, in its romantic scenery, and in the unique simplicity of its
people’s manners, a week’s quiet stay at the King’s Arms, the once
favoured and favourite inn of George the Third.
Then, if we take the middle oolite, we shall find in it the well-known
“coral rag,” so called because of the continuous beds of petrified coral
found in great abundance, and in many places, apparently, in the same
position in which they once grew at the bottom of the sea. We give below
a few specimens recently obtained by us from the north of Wiltshire,
from which it will be seen how closely they resemble those of existing
species.
[Illustration:
OOLITE CORAL. (Nat. Size.)
]
[Illustration:
CORALS AND SPONGE FROM THE OOLITE.
]
But what period was that, and what sunny clime was this, when the ocean
poured its waves over what are now our oolitic building-stones, and when
the coral insect built its continuous reefs in this our England, just as
it is now distributing its labours over so vast an expanse of sea in the
tropics and the southern hemisphere?[90] We cannot but recal the poetic
and vivid language of Hugh Miller: “Oh, that hoarse voice of Ocean,
never silent since time first began!—where has it not been uttered?
There is stillness amid the calm of the arid and rainless deserts, where
no spring rises and no streamlet flows, and the long caravan plies its
weary march amid the blinding glare of the sand; and the red unshaded
rays of the fierce sun. But, once and again, and yet again, has the roar
of Ocean been there. It is his sands that the winds heap up, and it is
the skeleton remains of his vassals,—shells, and fish, and the stony
coral,—that the rocks underneath enclose. There is silence on the tall
mountain peak, with its glittering mantle of snow, where the panting
lungs labour to inhale the thin bleak air, where no insect murmurs and
no bird flies, and where the eye wanders over multitudinous hill-tops
that lie far beneath, and vast dark forests that sweep on to the distant
horizon, and along long hollow valleys, where the great rivers begin.
And yet, once and again, and yet again, has the roar of Ocean been
there. The effigies of his more ancient denizens we find sculptured on
the crags, where they jut from beneath the ice into the mist wreath, and
his later beaches, stage beyond stage, terrace the descending slopes.
Where has the great destroyer not been,—the devourer of continents—the
blue foaming dragon, whose vocation it is to eat up the whole land? His
ice-floes have alike furrowed the flat steppes of Siberia, and the rocky
flanks of Schehallion; and his nummulites and fish lie embedded in the
great stones of the Pyramids, hewn in the times of the old Pharaohs, and
in the rocky folds of Lebanon still untouched by the tool. So long as
Ocean exists, there must be disintegration, dilapidation, change; and
should the time ever arrive when the elevatory agencies, motionless and
chill, shall sleep within their profound depths, to awaken no more, and
should the sea still continue to impel its currents and to roll its
waves, every continent and island would at length disappear, and again,
as of old, ‘when the fountains of the great deep were broken up,’
‘A shoreless ocean tumble round the globe.’”[91]
From this digression we return to our third division of the Oolite
proper, the _Lower Oolite_, as developed in Somersetshire (around Bath),
and in Wiltshire (Tisbury, Braford, &c.), which has its own points of
interest and of use. Here occurs the fuller’s earth, mostly found at a
village near Bath, called Old Down, which possesses the peculiar
property of absorbing the grease or oil remaining in cloth, and thus
_fulling_ or thickening it. Here also is found that peculiar rubbly
limestone, called “_Cornbrash_,”[92] in Wiltshire, which, on exposure to
atmospheric agencies, soon decomposes, and by mixture with he ordinary
constituents of the soil, makes an admirable material in agricultural
operations. Here also we have the Bath Oolite, the quarries of which are
very extensive, abundant in fossils, and the character of whose stone
gives to the city of Bath that clean and aristocratic appearance which
is so striking to the stranger approaching Bath from the Great Western
Railway.
“In this lower division,” says Lieutenant-Colonel Portlock, “also occurs
the Bath oolite, which is an excellent stone for the delicate mouldings
of gothic architecture, and is represented in France by the Caen stone,
which was imported for the purpose by our early architects, as may be
seen in the beautiful Temple Church.”[93] Of two varieties of Oolite,
called “Barnack rag” and “Ketton stone,” obtained from the quarries in
Rutlandshire and Northamptonshire, almost all the churches in
Cambridgeshire, of the twelfth and thirteenth centuries, are built. As
an instance, and illustrative of previous remarks, we may specify King’s
College Chapel, Cambridge. Whoever has been to the top of that gem of
gothic architecture, and walked outside where the stone is weathered,
and has been supplemented in various indifferent ways, may there see the
ripple marks of the old tides and winds, marking the ebb and flow of
pre-Adamite phenomena; and little shells, some of them most tiny ones,
but in beautiful preservation, once left in the soft calcareous sand,
now embedded in the hard building stone. And here, before we speak of
the fossils of the Oolite, we should like to be thoroughly understood
about this same ripple-mark, of which we have more than once spoken, and
which it seems desirable to explain. “Another structure, often
conspicuous in fine-grained sandstones, is that commonly called
“ripple-mark.” Either in quarries or natural cliffs, wherever the upper
surface of a bed is exposed, it is often found to be not smooth or flat,
but waved in small undulations, exactly like those so often seen on a
sandy shore. Now, a good deal of misconstruction has, I think, arisen as
to the origin of these small undulations or ripples in the sand, leading
sometimes to a possibility of grave error in geological reasoning.
People standing on the beach, and observing the gentle rippling motion
of the waves, and a very similar form in the sand beneath them, have not
unnaturally jumped to the conclusion that the one was the cause of the
other, that the ripple on the surface of the water had somehow imprinted
its form on the sand at the bottom. Now, really, one is not the _cause_
of the other, but they are both caused by the same action, and each is
as much a ripple as the other. The wave-like form in the sand is not a
ripple _mark_, but a ripple; if it is the mark of anything, it is a
‘current mark,’ and as such I have always preferred to speak of it. Just
as a current in the air produces a ripple in the surface of the water
below it, so a current in the water produces a ripple in the sand below
it. It makes no difference, indeed, whether the sand be acted upon by
air or water. Wherever the circumstances are favourable, wind will cause
a ripple or current mark on the surface of blown sand, as I observed
frequently under very favourable circumstances at Sandy Cape, in
Australia, and as has been observed by Sir Charles Lyell, near Calais.
In each case the moving fluid propels the grains of sand forward, piling
them up into ridges, which are perpetually advancing by the rolling of
particles over the crest of each ridge into the hollow beyond, where
they are for a time sheltered from the current, but soon buried under
the advancing ridge, to be again turned up and rolled onward, perhaps,
as their site becomes exposed to the force of the stream.”[94]
Other fossil remains found in the Oolite demand our notice before we
leave this period of the earth’s history, or this portion of the earth’s
crust. In the autumn of last year we were _en route_ to Cornwall, but
turned aside to visit, among other matters, the Oolite in the
neighbourhood of Bath, Chippenham, Bradford, and Trowbridge. Leaving the
trunk line of the Great Western, we transferred ourselves at Chippenham
to the branch that would take us to Trowbridge, that little Halifax or
Preston of the West of England. Many a long day had passed since we made
our first acquaintance with the poet Crabbe, and, though fossil hunting,
we felt we must pay a pilgrimage to his honoured shrine. We looked at
the old church in which for eighteen years he was the representative and
expounder of a large and human creed first uttered by the Great Teacher
from Galilee; and standing by Chantrey’s monument of Crabbe, we thought
how dear to God the man must be, who by dint of purpose, purity, and
hope, had risen from an unknown boy to command the ear of the public in
a time of poetic dearth, and who, amidst a very chequered life, had
realized the fine idea of Goldsmith:
“As some tall cliff, that lifts its awful form,
Swells from the vale, and midway leaves the storm,
Though round its breast the rolling clouds are spread,
Eternal sunshine settles on its head.”
We have heard it objected to Crabbe’s poetry that it wants fire, that it
has no romance, that it moves among the homely scenes of rustic life,
and seldom soars above parochial records and village history. But
Crabbe’s life was a singularly unromantic one; everything with him had
been real, hard, up-hill work, in which he had broken down had he not
believed in work rather than in genius. At Bungay School he was flogged
unmercifully, according to the wise methods of teaching the classics
then in vogue, but now happily exploding, except in our antediluvian
public schools; at Bury St. Edmunds he was apprenticed to a surgeon, who
quickly turned him into an errand boy and servant of all work; at twenty
years of age, conscious of innate power, and aspiring to literary
honour, he found himself in London in two equal conditions of misery,
without a _friend_ and without a _pound_; and then, in this very
condition of impecuniosity, the tender place of his heart was touched by
an unpropertied girl, Sarah Elwy, and he, the friendless young man,
loves her with a pure, deep, passionate, and unchanging love. For eight
long years of struggle, her image gave buoyancy to his spirit, and
oneness to his purpose, amidst the ups and downs of no common
hardships,—now turned from the rich man’s door by lacqueys in silver
lace, and then politely bowed out by those who might have been his
patrons in an hour of need, until, fortune favouring the bold, he became
not only the recognised poet of the poor, but better still, the husband
of a woman of surpassing worth.
Never aspiring to be a great poet, but only a true and real man, he
lived, and laboured, and published much. As a parish clergyman, his
memory at Trowbridge is a familiar household word, and having honourably
served his generation according to the will of God, he placidly and
Christianly fell asleep. As we stood by Chantey’s monumental record of
this good man, we felt that it did us good to look on such a memorial of
a working man; a working man, in the truest sense of the word, for we
must take some care, or else this good name will become an empty
conventional sham. We must not confine the term to any one class,
whether to men who work with sweat of _brow_, or to other men who work
as hard, and harder too, with sweat of _brain_; we give the name of
working men to all who toil with head or hand, and all such may be
bettered by the contemplation of a character like Crabbe’s.
But we return; our digression makes geology lag behind. We were
fortunate in procuring several fine specimens of the Crinoidean[95] or
Stone-lily family, about which the reader will pardon a few details. At
the stations of the Great Northern Railway, the marble mantelpieces and
uprights are all made of the Derbyshire encrinital marble, and the mind
is filled with singular surprise in the contemplation of these
interesting relics of past creations. How multitudinous must have been
this one form of life in those ancient days, and how quietly these
encrinites, when their brief term of life was over, must have sunk down
into the soft calcareous and argillaceous beds lying at the bottom of
the old ocean waiting to receive them, only that, mummy like, it might
embalm them safely, until in process of time, by upheaval, evaporation,
and sun-hardening, their delicate forms should be brought out to our
daylight in all the symmetry and beauty of their pre-Adamite life! But
the family of Crinoideans or Stone-lilies, called the “_Pear_
encrinite,” or “_apiocrinites rotundus_,” differs very remarkably from
the “_Lily_ encrinite,” or “_encrinites molliformis_;” and the following
descriptions grouped from Lyell and Buckland, aided by the accompanying
figures, will introduce these singular animals to our readers. “The
Crinoideans or Stone-lilies are almost all confined to the limestone,
but an exception occurs at Bath, where they are enveloped in clay. In
this case, however, it appears that the solid upper surface of the
‘Great Oolite’ had supported for a time a thick submarine forest of
these beautiful zoophytes, (_plant-animals_,) until the clear and still
water was invaded by a current charged with mud,” (see diagram below,
_a_,) “which threw down the stone-lilies, and broke most of their stems
off near the point of attachment. The stumps still remain” (_b_) “in
their original position, but the numerous articulations once composing
the stem, arms, and body of the zoophyte, were scattered at random
through the argillaceous deposit in which some now lie prostrate. Vast
strata of entrochal[96] marble, extending over large tracts of country
in Northern Europe and North America, are made up of the petrified bones
of encrinites, just as a cornrick is composed of straws. Man applies it
to construct his palace or to adorn his sepulchre, but there are few who
know, and fewer still who duly appreciate the surprising fact, that much
of this marble is composed of the skeletons of millions of organized
beings, once endowed with life, and susceptible of enjoyment, which
after performing the part that was for a while assigned to them in
living nature, have contributed their remains towards the composition of
the mountain masses of the earth.”
[Illustration:
_In situ._ _Restored._
PEAR ENCRINITES, OR APIOCRINITES ROTUNDUS. BRADFORD, WILTS.
]
That a better idea still may be formed of this zoophyte, let the
following diagrams be added: 1 is the body or bulbous head of the
pear-encrinite, curiously laminated, and geometrically divided; 2 is a
stem the natural size, and 3 a section, or one of the articulations, in
which its entrochal and radiated character will appear.
Below is a root of the pear-encrinite (1); this will give some idea how
rudely the graceful stems were broken off by the mud sea that came upon
them, and how firm a hold the roots of these beautiful zoophytes took of
the ocean bottom; many of these roots are covered with serpulæ and
coral, that only reveal their beauty under the lens. In the root before
us, a little coral insect has begun to reticulate his tiny links of
network; these may be seen in 3, magnified, and by comparison with 2,
which is a piece of Jamaica coral, found plenteously on the seashore of
the north side of the island, the similarity in structure and symmetry
will be immediately detected.
[Illustration: Fossil]
We have already spoken of the Ammonite, but we give here a specimen of a
rare kind, preserved in the fine clay near Chippenham. The form of this
ammonite is more remarkable than that of any other; its delicate
nautilus shell has been sadly compressed, and some of its external
protuberances have been broken off, and are here restored by dotted
lines; but, more striking still, the delicate horn-like structure that
terminated its mouth or aperture has been perfectly embalmed by Nature’s
kindly hand.
[Illustration: Fossil]
[Illustration:
AM. JASON, OR AM. ELIZABETHÆ. _Oolite._
]
We have no ammonites afloat now: its twin brother, the nautilus,
survives still in sunny climes on the tropic seas; and, perhaps, when a
“new heaven and a new earth” shall usher in another act in the great
drama of creation, the nautilus may be superseded by other forms of
molluscous life, to show forth the exhaustless resources of His skill
and wisdom, who is “wonderful in counsel and excellent in working.” Thus
sings a poet and a geologist:—
“The nautilus and the ammonite
Were launch’d in storm and strife;
Each sent to float, in its tiny boat,
On the wide, wild sea of life.
“And each could swim on the ocean’s brim,
And anon, its sails could furl;
And sink to sleep in the great sea deep,
In a palace all of pearl.
“Thus hand in hand, from strand to strand,
They sail’d in mirth and glee,
Those fairy shells, with their crystal cells,
Twin creatures of the sea.
“But they came at last to a sea long past,
And as they reach’d its shore,
The Almighty’s breath spake out in death,
And the ammonite lived no more.
“And the nautilus now, in its shelly prow,
As o’er the deep it strays,
Still seems to seek, in bay and creek,
Its companion of other days.
“And thus do we, on life’s stormy sea,
As we roam from shore to shore,
While tempest-tost, seek the loved—the lost,
But find them on earth no more!”—RICHARDSON.
Below we add a small group of oolitic shells, not on account of any
particular beauty of form attaching to them, but as characteristic of
this formation, and as lying conveniently near us for being figured.
Their hard names—hard to the mere English reader—may possibly alarm the
young, who may at present skip the names: let them get to love the
science—let them get into the habit of making nature have a meaning in
its realities, and into the settled purpose of determining to know what
kind of a world this is in which God has cast their lot, and soon these
hard names will be only as finger-posts, directing to certain roads on
which they may journey to the end of a happy pilgrimage. Aye, better
than any old pilgrimage to a fabulous Holy Sepulchre, will be your
pilgrimage to sepulchres wrought by the hand of Infinite Benevolence,
for the creatures whom his infinite wisdom had formed, and sustained
until he pronounced the decree, “Return!”
[Illustration:
1. CUCULLEA CARINATA.
2. CUCULLEA UMBONATA.
3. MODIOLA BIPARTITA.
4. TEREBRATULA GLOBOSA.
5. TEREBRATULA DIGONA.
6. TEREBRATULA MAXILLATA.
]
Before we quit the Oolite, we have one more stranger to introduce—and in
very truth he is the strangest stranger with whom we have yet made
acquaintance. We refer to the Pterodactyle.[97] The geologist, we may
suppose, has just lighted on one of these extraordinary remnants of
antiquity, say in the Stonefield Quarry, Oxfordshire, and stands aghast
as his pick lays open the fragments of this nondescript creature.
[Illustration: Fossil]
But when the researches of science had laid bare the whole of the fossil
remains of this heterogeneous creature, when the head and gape of the
crocodile, the wing-hands of the bat, and the web-feet of the duck were
all revealed; when it was ascertained to be one of those flying reptiles
that have no existing type, and that it was “the most extraordinary of
all the beings of whose former existence the study of fossils has made
us aware,” and “the most unlike anything that exists in the known
world;” the blank wonder of the geologist gave way to calm and admiring
study, as these undreamt-of relics of the past were made subservient to
the wisdom and delight of the present.
[Illustration: Fossil]
The following is Cuvier’s description of this strange creature, borrowed
from Ansted, vol. i, p. 418:—
“You see before you,” he says, “an animal which in all points of bony
structure, from the teeth to the extremity of the nails, presents the
well-known saurian characteristics, and of which one cannot doubt that
its integuments and soft parts, its scaly armour, and its organs of
circulation and reproduction, were likewise analogous. But it was at the
same time an animal provided with the means of flying; and when
stationary, its wings were probably folded back like those of a bird,
although, perhaps, by the claws attached to its fingers, it might
suspend itself from the branches of trees. Its usual position, when not
in motion, would be upon its hind feet, resting like a bird, and with
its neck set up and curved backwards, to prevent the weight of the
enormous head from destroying its equilibrium. Any attempt, however, to
picture this strange animal in a living state, would appear to one who
has not followed the whole argument to be rather the production of a
diseased imagination, than the necessary completion of a sketch of which
the main outlines are known to be true. The animal was undoubtedly of
the most extraordinary kind, and would appear, if living, the strangest
of all creatures. Something approaching to it in form we may perhaps
recognise in the fantastic pictures of the Chinese; but art has, in this
respect, not been able to rival nature; and the fabled centaur, or
dragon, do not present anomalies more strange than those of the species
we have been considering.”
This description of Cuvier will recal to the reader’s mind the
well-known words of Milton (Par. Lost, Book II. line 247), in which, in
his description of an imaginary fiend, he almost realizes to the life
the animal whose extinct and fossil remains have been so recently
disinterred.
“The fiend
O’er bog, or steep, through strait, rough, dense, or rare,
With head, hands, wings, or feet, pursues his way,
And sinks or swims, or wades or walks, or creeps or flies.”
[Illustration:
1. PTERODACTYLE, FROM SOLENHOFEN, (one-third natural size.)
]
We conclude this chapter by giving drawings of the Pterodactyle. The
_first_ is the Pterodactyle as found at Solenhofen; the _second_ is the
skeleton restored; and the _third_ the animal itself, according to the
best judges of what a portrait of the Pterodactyle would be.
[Illustration:
2. SKELETON RESTORED.
]
[Illustration:
3. THE PTERODACTYLE.
]