SECONDARY ROCKS.
_No. 2. The Oolitic System._
“Hast thou perceived the breadth of the earth? declare if thou knowest
it all.”—JOB.
The next division of the secondary rocks is termed the Oolitic system or
group. This is a term rather of convenience than of scientific accuracy.
In this title it is intended to include the Lias, the Oolite proper, and
the Wealden formations. This chapter will be limited to a consideration
of the first two series of rocks just named, and in each we shall find
abundant material for thoughtful contemplation and intelligent wonder.
The English student of geology possesses this great advantage over the
student of geology in other lands: this little “corner of Europe,”
called England, contains types of almost all the European rocks, and not
a few of those that are found in Asia, Africa, and America. To this fact
Professor Whewell alluded when he said, “As if nature wished to imitate
our geological maps, she has placed in the corner of Europe our island,
containing an index series of European formations in full detail.” Out
of this circumstance, though little thought of by any except the
geologist, arise our threefold sources of wealth. But for the varied
distribution of rocks through our country, neither mining, nor
manufacturing, nor agricultural operations could be carried on to that
extent, and with that success, which have made this country the envy and
the admiration of the civilized world. In the warlike age, when
Shakspeare wrote, we expect that his praise of England will be on
account of her internal security from foreign invasion, and in the hardy
prowess of her sons; as when he says, and we are not insensible to the
patriotic emotions wakened up by such noble words,—
“This royal throne of kings, this sceptred isle,
This earth of majesty, this seat of Mars,
This fortress built by nature for herself,
Against infection and the hand of war;
This blessed plot, this earth, this realm, this England.”
_King Richard II._
But, we confess, we rather dwell on other features in our physical and
social history, as affording the best proof of our real greatness, and
the best illustration of our untiring Anglo-Saxon energy. We would
rather record such facts as the following, than announce any “famous
victory;” we would rather turn fondly to considerations like these, than
contemplate
“Our sands that will not bear her enemy’s boats,
But suck them to the top-mast.”
“Though animal organization is beyond the constructive skill of man, he
takes the elements existing in nature, and by new combinations gets new
power. He keeps adding to the qualities of his noblest coursers, his
fleetest dogs, and his goodliest beeves. He year by year develops the
resources of the soil, reclaims the marsh from wild fowl, the heath from
rabbits, and the flinty hillside from briars and thistles. He goes on
multiplying the blades of grass and grains of corn, and compels an equal
area to yield a twofold substance. He discovers in his raw materials
unsuspected properties, until soda and sand are converted into a Crystal
Palace, and water, coal, and stony ore into a train, which rushes with
the might of an earthquake and the velocity of the wind. He devises
fresh applications of machinery, and in the creations of his ingenuity
finds a servant and a master. The broad result to England is quickly
told: fifty years have doubled the population, and employment and
subsistence have been doubled likewise. An engine is contrived which
economises labour, and threatens starvation to the labourer; but the
issue proves that the work it makes is more than it saves. Annihilate
all the cranks and wheels constructed in the interval, and return our
counties with their present population to the condition in which they
were when the century began, and there would be nothing but famine in
the land. A government wiser than man’s has provided, in the constant
exertion of talent, for the increase of our race, and maintains a
proportion between our wants and our progress. Every round we rise in
the ladder leads to a higher; but our step is limited, or we should
outstrip our needs by too prodigious a stride, and encroach on the
rights of a future age.”[77]
There is no turning over a leaf in the many-paged book of geologic
investigation, without finding the frequent application of thoughts like
these. Every part of the crust of the earth has its uses, and uses, too,
that are peculiar to _it_; and as we have endeavoured hitherto to point
out the economic uses of each formation in the great onward progress of
humanity, we shall not find ourselves at a loss in this respect, now
that we enter the second division of the secondary rocks.
We commence with the Lias.[78] During the new red sandstone period, clay
and marl were being deposited at the bottom of the seas and lakes then
in existence. These were the natural degradations of existing rocks;
into these soft deposits sunk various pre-Adamite remains, finding in
the soft argillaceous beds ready to receive them the “possession of a
burying-place” provided for them by the infinite Creator. Here they
remained until in process of time, at the close of the new red sandstone
period, these beds and their contents were upheaved from beneath the
ocean, apparently without much violence; and becoming hardened by the
chemical action of sun and wind, present us with the formation we are
now studying, rich in its peculiarly characteristic fossils. The name
lias, or layers, indicates the finely stratified condition of the rocks,
and affords proof of the tranquil method of their deposit and upheaval.
They stretch in a north-easterly direction from Lyme Regis, in
Dorsetshire, where it may be seen on the open coast cliffs for about
four miles, on to Whitby, in Yorkshire, where also it lies open to the
sea, in cliffs of considerable elevation, and lying conformably with
other strata, and is thus particularly favourable to geologistic
examination. It is in the shales of the lias at Whitby, and at Lyme
Regis, that most of the extraordinary and remarkable fossils have been
met with that we are about to describe, and for which this formation is
so justly renowned. Indeed, so far as palæontology, or the knowledge of
ancient beings, is concerned, there is no formation more full of
interest to the student.
Here we meet for the first time with the ammonite. We will introduce him
first in his fictitious, and then in his real character, and this we do
to show how science dispels the follies of ignorance and superstition.
The ammonites were once supposed to be petrified snakes—indeed they are
even now called by the ignorant, “_snake-stones_;” and the pleasant
little legend about these snake-stones was this, that St. Hilda, who
once resided near Whitby, was very much annoyed, as any matron would be,
especially if she kept an establishment for young ladies, as St. Hilda
is alleged to have done, by the multitude of snakes that infested the
place, and disturbed her equanimity. Accordingly, she set to work, and
having first prayed their heads off, then prayed the snakes into stone.
In Scott’s “Marmion” the legend reads thus:—
“And how the nuns of Whitby told
How of countless snakes, each one
Was changed into a coil of stone
When holy Hilda prayed,
Themselves within their sacred bound,
Their stony folds had often found.”—CANTO 2.
Richardson, in his Geology, relates the “instance of a dealer who having
been requested by his customers to supply them with some of the
creatures which had escaped decapitation, contrived to manufacture some
heads of plaster of Paris, and affixed them to the specimens; thus he
pursued a thriving trade, until some remorseless geologist visiting the
place, not only beheaded the reptiles, but showed that they were in
reality fossil shells.” With the figure of the ammonite every reader of
geological books is familiar; it is, perhaps, the best known and most
beautiful of all our fossils. We give below a representation of four
different kinds, found in the lias and oolite.
[Illustration:
1. AH. BECHEI. LIAS
]
[Illustration:
2. AM. BRODIEI. OOLITE.
]
[Illustration:
3. AM. HUMPHRIESIANUS. LIAS.
]
[Illustration:
4. AM. WALCOTTI. LIAS.
]
In general outline it will be seen that the ammonite somewhat resembles
the nautilus, and yet there are characteristic differences that are so
striking as to mock the development hypothesis. In the first place, the
shell of the ammonite, though of the same flat discoidal form as that of
the nautilus, appears to have been much thinner; secondly, it will be
seen that the whorls of the ammonite are rounder and more in number than
those of the nautilus; and lastly, the siphuncle, of which more
presently, runs _round_ the chambers of the ammonite, but _through_ the
chambers of the nautilus. Let us look a little at each of these
peculiarities; and to aid us, we give below two drawings of sections of
ammonites, and two drawings of a nautilus.
[Illustration:
AM. KŒNIGI LIAS.
]
[Illustration:
NAUTILUS. (FOSSIL.) HORIZONTAL.
]
[Illustration:
AM. HETEROPHYLLUS. LIAS.
]
[Illustration:
NAUTILUS (FOSSIL), SHOWING THE SIPHUNCLE.
]
The shell of the ammonite is a continued arch, having transverse arches
or ribs crossing the main arch, giving to _some_ particular forms of
beauty, and to _all_ the peculiar symmetry of a series of spiral curves.
But, to compensate for the thinness of the shell, a peculiar adaptation
is provided; it consists in the flutings which are seen in the surface,
occasioned by the transverse ribs. A pencil-case made of a thin plate of
silver is all the stronger for being fluted, and the zinc roof of a
railway station is fluted or corrugated, on the same principle. It is
thus that strength is combined with economy of material and elegance of
form. In the ammonite we see this recent invention anticipated by the
Creator, long ages ere man had appeared. In addition to this, those
round knobs or bosses studding some of the ammonites (_e.g._ 1 and 3),
like gems upon a diadem, add strength as well as beauty to their frail
forms, and thus served the same purpose as the groin work in gothic
architecture, a beautiful illustration of which may be seen in the roof
of Salisbury Cathedral. Then, looking at the chambers of the shell in
the sections, we find that some were for living in, while others were
mere empty air-cells, used for purposes of elevation or depression,
according as the animal wished to rise to the top or sink to the bottom
of the sea,—these front chambers being the drawing-rooms in which the
aristocratic ammonite lived. Running _round_ them is an hydraulic
instrument, called the siphuncle, or air-tube, by means of which
singular mechanism this curious animal altered his specific gravity for
purposes of sinking or swimming. “The universal prevalence of such
delicate contrivances in the siphuncle, and of such undeviating and
systematic union of buoyancy and strength in the air chambers throughout
this entire family, are amongst the most prominent instances of order
and method that pervade these remains of former races that inhabited the
ancient seas; and strange indeed must be the construction of that mind,
which can believe that all this order and method can have existed
without the direction and agency of some commanding and controlling
Mind,”[79] These are what Cowper finely calls “_the unambiguous
footsteps of the God_;” and in tracing them our minds are elevated into
exalted ideas of Him, whose wisdom is unsearchable, and whose ways are
past finding out. With regard to the sections of the ammonite, as seen
in the two previous figures, dimly indeed compared with the beautiful
specimens from which they were copied, we can only add, in the words of
the treatise just quoted, “Nothing can be more beautiful than the
sinuous windings of these sutures in many species, at their union with
the exterior shell, adorning it with a succession of most graceful
forms, resembling festoons of foliage and elegant embroidery. When these
thin septa are converted into iron pyrites, their edges appear like
golden filagree work, meandering amid the pellucid spar that fills the
chambers of the shelf.”
We pass by some other fossils found in the lias, such as the
pentacrinite, of which we shall speak when we come to other members of
the crinoideal family, gryphites,[80] of which the _gryphea incurva_ is
the most common type, broken portions of which, and sometimes good
specimens, may be found in most gravel heaps, their peculiar form having
obtained for them the name among the rustics of “_devil’s toe-nails_;”
and belemnites,[81] often met with in vast numbers, and known under the
name of _ladies’ fingers_, and _thunderbolts_; and fossil fish, a few
specimens of which are found in the lias.
Passing by these, we next notice the huge Saurians,[82] by far the most
wondrous vertebrated animals with which either the ancient or modern
vestiges of creation have made us acquainted. These saurians, sometimes
called Enaliosaurians, (_enalios_, the sea, and _sauros_, a lizard,) on
account of their peculiar habitat, may all be included in Milton’s
description of the leviathan, though it is hard to tell what precise
creature our great poet had in his “mind’s eye” at the time of writing
this description—one line of which, from having a syllable too much,
reads most unrhythmically—for the crocodile does not go so far out to
sea as he represents, and if he did, would be hardly likely to go on to
the “Norway foam;” nor can he mean the whale, for the whale has no
“scaly rind:”—
“That sea beast,
Leviathan, which God of all his works
Created hugest that swim the ocean stream.”
_Par. Lost_, Book I.
But before we enter on a description of these extinct and anomalous
creatures, we shall give a sketch of both. No. 1 is the skeleton of the
Ichthyosaurus,[83] restored from the fragments found chiefly at Lyme
Regis: it may be seen, with several of its congeners and contemporaries,
in the British Museum. No. 2 is a restored outline of this saurian; from
both of which sketches it will be seen that the most justly dreaded
monsters of our tropical climates sink into insignificance beside the
ancient tenants of the mighty deep, in those remote periods of
geological antiquity we are now contemplating. The combination of the
forms of the fish and the lizard seems more like a troubled dream of
Fuseli, than the calm and philosophic deductions of the most eminent
anatomists and philosophers.
[Illustration: Fossil]
The fossil remains of this creature show that it was intended chiefly,
if not entirely, for a marine life. Like the seal, it may occasionally
have come to bask on the shore, although, like the seal, it possessed no
developed legs or feet, but only paddles. The size of these animals was
enormous; they sometimes attained a length of upwards of thirty feet;
and to realize such a creature, we must imagine our meeting with a
monster thus long in some tropical swamp, having a smooth slimy skin
like a whale, a long heavy head like a porpoise, teeth like a crocodile,
vertebræ hollow, and therefore light, like the vertebræ of a fish,
enabling it to dive swiftly to the bottom, and equally as swift to rise
again; and paddles like a whale. Again, look at the head,—that is, go
into room No. 4 of the British Museum, and look with wonder, as we often
have, on Wall-case A(1), and B(2), and C(3), and you will agree with us
that the half of the wonders of this heteroclite[84] creature have not
been told. It had a gape, that is, it could open its jaws seven feet, so
that a grenadier guard might walk into his mouth without stooping; it
had teeth, not placed in sockets, but arranged in a long continuous
trough; it had an eye more marvellous than the eye of the Ancient
Mariner, that kept the wedding guest sitting on a stone, who could do
nought but hear, for the eye of the Ichthyosaur was often eighteen
inches in diameter, so that a man might put his head, hat and all, into
its socket,—and this eye was possessed of more wondrous properties than
even the eye of the celebrated Irishman that could see round a corner,
for the eye of the Ichthyosaur enabled its owner to see all round the
country at one time; and as it was a very predatory animal, having
doubtless as many enemies as victims, it required this eye both day and
night, and accordingly the eye was placed _close to the nose_, so that
the animal could not come to the surface of the water to breathe without
being immediately forewarned of danger, or advised of a prize.[85]
Next follows the _Plesiosaurus_,[86] which may be seen, in its skeleton
parts, restored, and in casts, in room No. 3 of the British Museum, in
Wall-cases D(4), E(5), F(6). “The beautiful state of preservation of
many of the Plesiosauri, the entire skeleton, from the point of the
muzzle to the extremity of the tail, lying in relief, as if it had sunk
down quietly on the soft clay, and become petrified on the spot,
manifests how different were the conditions in which the strata of the
lias and the wealden were deposited; while the exquisite manner in which
the investing stone has been removed, attests the consummate skill and
indefatigable zeal of the gentleman (Mr. Hawkins) by whom these superb
fossils were developed.”[87]
Below, No. 1, is a skeleton of the Plesiosaurus, and No. 2 is the
restored outline of the animal, whose largest specimen never exceeded
seventeen feet.
[Illustration: Fossil]
Cuvier thus describes the Plesiosaur (we borrow the quotation from
Buckland):—
“The Plesiosaur is the most heteroclite, and in character the most
monstrous, of all the animals that have yet been found amid the ruins of
a former world. To the head of a lizard it united the teeth of a
crocodile, a neck of enormous length resembling the body of a serpent, a
trunk and tail like that of an ordinary quadruped, the ribs of a
chameleon, and the paddles of a whale. Such are the strange combinations
of form and structure of the Plesiosaurus, a genus the remains of which,
after interment for thousands of years amidst the wreck of millions of
extinct inhabitants of the ancient earth, are at length recalled to
light by the researches of the geologist, and submitted to our
examination in nearly as perfect a state as the bones of species that
are now existing on the earth.”
We add a word upon the uses of this portion of the crust of the earth,
and we do so in the striking words of Hugh Miller. “We have seen how
this central district of England has its storehouses of coal, iron,
salt, lime,—liberal donations to the wants of the human animal, from the
carboniferous, saliferous, and silurian systems; and to this we must now
add its inexhaustible deposits of medicine, contributions to the general
stock by the oolitic system. Along the course of the lias medicinal
springs abound: there is no other part of England where they rise so
thickly, or of a quality that exerts a more powerful influence on the
human frame. The mineral waters of Cheltenham, for instance, so
celebrated for their virtues, are of the number; and the way in which
they are elaborated in such vast quantities seems to be as follows:—They
all rise in the lias, a formation abounding in sulphate of iron, lime,
magnesia, lignite, and various bituminous matters; but they all have
their origin in the saliferous marls of the upper new red sandstone
which the lias overlies. In the inferior formation they are simply brine
springs, but brine is a powerful solvent. Passing through the lias, it
acts upon the sulphur and the iron—becomes, by means of the acid thus
set free and incorporated with it, a more powerful solvent
still—operates upon the lime, upon the magnesia, upon the various
lignites and bitumens—and at length rises to the surface, a
brine-digested extract of liassic minerals. The several springs yield
various analyses, according to the various rocks of the upper formation
through which they pass; some containing more, some less lime, sulphur,
iron, magnesia, but in all the dissolving menstruum is the same. And
such, it would appear, is the mode in which Nature prepares her simples
in this rich district, and keeps her medicine-chest ever full.”
Thus wondrous is the machinery of God’s universe; every day utters some
fresh speech, and every night shows forth some new knowledge.
“The Lord of all, himself through all diffused,
Sustains and is the life of all that lives.
Nature is but a name for an effect,
Whose cause is God.”
NOTE.—We do not like to close this chapter without mentioning the name
of _Mary Anning_, of Lyme Regis. It is mainly to her practical talent
and perseverance that we owe these relics of past ages found in the
lias: the history of the British Museum will have to record this
humble name, as well as that of Sir Hans Sloane, its founder. The
following we borrow from Miss Zornlin’s “Recreations in Geology,” p.
197—
“Mary Anning died in 1847. Her father, by trade a carpenter, was in
his own neighbourhood one of the first collectors of _coorosities_, as
they are locally termed, such as _petrified ladies’ fingers_ and
_turbots_ (as the fish were termed), _verterbarries_ (vertebræ),
_cornemonius_ (ammonites), and _crocodiles’ jaws_ (ichthyosauri), &c.
He died when his daughter Mary was about ten or eleven years old; and
the circumstances of the family being straitened, she went down one
day to the beach to search for ‘coorosities.’ She found a fine
specimen of an ammonite; and as she was coming home, a lady who met
her in the street offered her half-a-crown for the fossil in her hand.
Mary Anning’s future destiny was sealed. She prosecuted her searches
‘on beach,’ and in the following year (1811) observed among the ledges
of the rocks a projecting bone of some animal. This enterprising girl
(then only eleven years old) traced the fossil in the cliff, and hired
some men to dig it out. It proved to be the skeleton of an
ichthyosaurus, and has for many years formed an object of interest in
the British Museum. Mary Anning afterwards sold this specimen for
about 23_l._”
To this we add, that in the “Memoirs of Ichthyosauri,” by Thomas
Hawkins, Esq. reference is made to Miss Anning, as one “who devoted
herself to science, and explored the frowning and precipitous cliffs,
when the furious spring-tide conspired with the howling tempest to
overthrow them, and rescued from the devouring ocean, sometimes at the
peril of her life, the few specimens which originated all the facts
and ingenious theories of those eminent persons, whose names must ever
be remembered with sentiments of the liveliest gratitude.”