ft. in.
1 Yellow clay 4 0
2 Coal Smut; (might represent Sill, coal) 1 0
3 Clunch 1 0
4 Vigor coal 0 10
5 Ganey coal rock (shale) 1 0
6 Ganey coal 1 3
7 Linseed earth (A brown soapy kind of clay) 1 0
8 Best coal and middle coal (These are 2 0
separated by a parting which diminishes
from 10 inches on the west to 2 in. on the
east.)
9 Fine clunch 1 0
10 Clod coal 2 0
11 Clunch with roots and plants, and nodules 5 0
of ironstone at bottom
12 Little flint coal 2 0
13 Little flint rock (with prostratetrees and 27 0
petroleum)
14 Crawstone crust, with upright trees and
roots embedded.
Total 49 11
Beds of underclay so invariably accompany seams of coal that some have
come to the conclusion that there was no exception to the rule. Here
however is one, in the case of the Little Flint coal, which lies
immediately upon a sand rock. Evidently it was not formed like peat from
vegetation which grew and accumulated on the spot. There is no underclay
to support the roots of ordinary coal-measure plants, but the coal
follows closely the contour of the rock on which it lies; as though it
had flowed over it and had been laid down upon it like a sheet of
bituminous matter. And there is not the least doubt but that this was
the case. Sigillarias, Lepidodendrons, Calamites, and tree-ferns
flourished on the slime now hardened into shale, and which shows
sun-cracks, and worm-burrowings, indicative of the then surface, with
tracks of locomotive mullusca, as they dragged their shells along the
soft impressionable slime. Heavy tropical rains then falling upon some
upraised and exposed Caradoc or perhaps Millstone grit lands, the latter
scarcely yet consolidated, brought down and held in suspension a quantity
of sand which, as it settled down, formed a bed varying from three to
thirty feet in thickness. The body of water which contained so much sand
must, of course, have been much greater, and would probably cover the
whole of the vegetation. The result was that the lower parts of the
largest trees which were buried first were preserved in situ. The upper
parts toppled over and lay embedded in the sand, as we find them. In
both cases the vegetable matter decayed and was replaced atom by atom
with fine sand; but the vegetable tissues, oil, and seeds, being
lightest, rose above the sand, forming a pulpy bituminous plastic bed,
which first fermented, and then crystalized into coal. Even the little
disc-like seeds of the sigillaria, which make up a considerable portion
of the coal, and which floated with other matter, lie flat and parallel
with the lamina of the coal itself.
Nor is this the only instance of the kind. The Top coal of Halesfield
and Kemberton shews signs of liquefaction; portions of fish, such as
teeth, bones, and scales being embedded in the coal.
We ought to add in connection with the Black Rock section that the five
feet of clunch over the Little Flint Coal is the underclay for the Clod
Coal, and is full of roots and rootlets.
[Picture: Trees, fens, swamp]
The descent from the Crawstone crust to the Silurian shale of the Dale
cannot be traced. As passed through at the Limestone pit at Lincoln
Hill, it was as follows:—
Ft. In.
1. Crawstone Measure Crust 1 8
2. Rock 10 6
3. Coal Smut 0 9
4. Clunch with balls of Sandstone 12 0
5. Lancashire Ladies’ Coal 0 6
6. Strong Clunch with Sandstone balls 19 0
7. Sandstone Rock 10 6
8. Chalkstone 12 0
9. Limestone (Silurian) 28 6
Total 95 5
This then may be considered a fair representation of the remainder of the
measures which occur below those seen on the surface at the Black Rock
Quarry; but the passage from the carboniferous to the Silurian formations
is _no where conformable_, and no mention is made of the Millstone grit,
a portion of which certainly intervenes, and which is to be seen in small
patches near, but which might possibly be represented by the three or
four last measures in the section of the Lincoln Hill Limestone Shaft.
Excellent opportunities occur in this immediate neighbourhood of studying
the junction of the Silurian and Carboniferous formations, and of the
evidences afforded of the denudation of the one prior to the formation of
the other. To the general reader these words may convey little meaning,
but the scientific student who studies the evidences here made clear
cannot fail to comprehend the fact that he has before him not only an old
sea-bed, rich in relics of the fauna which inhabited its waters, but a
sea-bed which had become a cliff, and had in turn been gradually cut down
and wasted during successive ages prior to that at which a carboniferous
flora had begun to flourish. Two series of rocks are here in
juxtaposition, yet so widely separated by time, as to indicate a gap in
the consecutive history of the earth as great as if we were to blot out
the intermediate history of this country from the close of the Heptarchy
to the reign of George III.; only that the period of time in the latter
case would bear no manner of comparison with the former. If we suppose
the Wenlock limestone to have been once covered at these points by the
Ludlow limestone, and this again by the old red sandstone—as is the case
to the south, to say nothing of the carboniferous limestone and millstone
grit, we are forced to the conclusion that thousands of vertical feet,
and hundreds of cubic miles of solid ground were first piled up and then
cut down and carried away by the sea. Creation itself in the interval of
their formation passed through many phases, during which new species came
slowly into being and disappeared, and were again replaced by others. To
fill up the gap that succeeds this great silurian flooring of the
coal-measures, to study the intermediate links of the missing strata we
must go to the millstone grit in its undenuded or partially denuded
state, as it occurs beneath the coal-measures of Little Wenlock, or at
the bend of the road, called “The Turn,” in going from Coalbrookdale to
Wellington.
The first thing striking the attention is a buff coloured shale,
weathered on the surface to clay, at the base of the bold bluff cliff of
gritty sandstone so conspicuous on the brow of the hill. Whilst
examining this member of the Silurian series a man from a neighbouring
cottage remarked, “That is fuller’s earth; persons fetch it when they are
galled, and it is good for the eyes; large quantities are fetched away
and sent to Manchester.”
The fossils it contains show that it belongs to the lowest member of the
Ludlow group, and that the whole of the Aymestry and Upper Ludlow have
been stripped off and washed away before either the millstone grit or the
coal-measures were formed.
Among the fossils yielded by this shale, in addition to bivalves and
corals, are those interesting forms of crustaceans called pen fossils,
from their resemblance to a quill pen. The species we found was
Graptolithus priodon, described in the early works of Murchison as
Graptolithus Ludensis. The trilobites, from the fineness of the
material, are so sharply and beautifully preserved that the visual organs
of the little creatures are clearly discernible, even to the optical
tubes, elongated cones, or crystaline lens such as are to be seen so
marvellously distinct on the eyes of the dragon-fly of the present day.
The beautiful markings too on the shield of these wondrous little
creatures which flourished in these seas, in such numbers that they may
be got out in groups—forms which died out and perished before the close
of the carboniferous formation represented above it—are so delicate and
fine as to equal if not to defy imitation in ordinary materials in use at
the Dale Works; and it is we fancy at least worth the experiment whether
with this shale reduced to powder it might not be made to produce
delicate impressions after the example here set by nature. We also found
here some beautiful Lingula, a Patella, an Orbicula, a Leptæna, a
Lituites, a Fienestella, and other fossils. To inhabitants of the Dale,
here is a field of research open which they may make their own, close to
their own doors.
This fine earth is known by various names where it occurs in Shropshire
and the adjoining county of Herefordshire. In the latter county it is
said to be used by country people for cleansing purposes, in which case
it is called “Walker’s earth or soap.”
If the reader will follow this soft soapy shale, as we did, higher up
into the coppice, he will find large masses of rock which have been
toppled over through the shale giving way. A slip on the side of the
narrow path discloses a bed of it, and immediately above it, consequent
upon a former slip, we come upon a sandstone rock from twelve to fourteen
feet thick, with quartz pebbles, representing the millstone-grit. Then a
bed of black shale occurs, about six inches thick, which is chiefly made
up of coal-plants, some of which are converted into charcoal. These
plants do not appear to have grown on the spot, but to have been drifted
into their present position. They were evidently in a soft and yielding
state, some of them being pressed quite flat. {318} One good sized slab
opened with a cast of a Lepidodendron, and we met with another cast,
clearly of the same tree, a short distance west of it. Another, a
Sigillaria, was much more distinct, the leaf scars being quite sharp, and
the fibres of the inner bark very clear. This interesting band of coal
shale is succeeded by another of yellowish clay, of about equal
thickness; and these are followed by a second and a third band of black
shale, with alternate ones of yellowish clay. Above these are thick
sandstone rocks, some white, and some coloured red by iron, which here
and there occurs in the form of hematite.
[Picture: Fossil tree?]
The whole of these rocks, from the surface to the soft Lower Ludlow shale
here described would better represent the series of connecting links
conducting us down from the Crawstone Crust at the Black Rock Quarry than
any shaft section we could find described, and the whole may properly be
classified as Millstone grit, which is known to attain a thickness of 80
feet in this locality, and to increase to 120 and 150 at a short distance
from here, whilst in Derbyshire it thickens to 350 feet, and elsewhere to
a maximum of 1,000 feet, and includes, as here, shales and thin coals.
Colliers recognise the ironstone which crops out here as the Poor Robin
of the Dawley Deep field pit, which occurs 60 feet below the Little Flint
Coal; which affords another key to the series of measures which underlie
the same coal at the Black Rock Quarry. The Poor Robin however here
described must not be confounded with the one of the same name in south
Staffordshire, which occurs higher up in the series.
We have given a few, and those the lower coals only, such as are found in
the vicinity of Coalbrookdale; it would require more space than we can
devote to it to enter upon a description of the measures occurring higher
up in the series, in what is called the Coalbrookdale Coalfield. The
ideal representation given of coal producing plants at the head of this
article and in subsequent pages, and the one given p. 213, will convey a
tolerable idea of the surface as it occurs to the minds of geologists
during successive periods of the coal formation, and upon which we
purpose offering some remarks, condensed and as brief as is consistent
with a due explanation of the circumstances. We have already spoken of
the oil which exudes from the rock described. It is the same which oozed
from a similar rock at the “Tar Tunnel” at Coalport, at the rate, it is
said, of 1,000 barrels per week. We extract from it naptha, rectified
naptha, gas to illumine our houses, and those magnificent colours derived
from the sun’s rays when the earth was young and green, mauve, magenta
and a hundred medium tints.
Coal itself rarely contains well preserved specimens of plants, but
Sporangia (_Flemingites gracilis_) may be found in the Lancashire
Ladies’, the Flint coal, and most if not all others, the tough little
seed cases having resisted the effects of fermentation and
crystallization, which destroyed the cellular tissues of plants, but
which may sometimes be seen in a carbonised state. If the reader will be
at the trouble to split open a piece of coal where he finds brown streaks
at the edge, he may detect with the naked eye thousands of little discs
clustered and heaped together so thick as to constitute one third at
least of the coal; and if he applies a lens he will find some open, with
bright amber coloured matter inside; and others closed and imbricated.
We have found them in all the coals we have yet examined. Let any one
doubtful of the vegetable origin of coal take a bass burnt white from the
grate, tap it on the edge, and he will find between the laminated plates
numerous impressions of plants. Lindley and Hutton, from experiments
instituted by them, state that plants such as are represented on pages
305 and 313, were peculiarly adapted for preservation under water.
[Picture: Alethopteris lonchitica]
Many hundreds of species of plants have been made out, two thirds being
ferns. Very beautiful and clear impressions of the accompanying one,
Alethopteris lonchitica, or true fern, are obtained, the finest
impressions being generally in the Ballstone. It was in fact the great
age of ferns: as many as 250 having been described, according to form,
structure, &c. Thus, we get:—Asterophyllites (star leaf fern),
Cyclopteris (round fern) chiefly in the Ballstone, Caulopteris (star
fern); Sphenopteris (wedge shape fern); also Newropteris, or nerved
winged fern, which are given on the two following pages:—
Many bear strong resemblances at a first glance to others cultivated in
our greenhouses, or growing wild in their favourite habitats, and some
approximate so closely to living forms as to make it a question whether
they should be classified with different genera or not. The number is
remarkable, considering that not more than sixty distinct species are at
present indigenous to Europe. The tree ferns of modern horticultural
gardens, with their scar-marked trunks and branching fronds, like those
from the Mauritius, Brazil, and the Isle of Bourbon, convey tolerable
ideas of those of the coal-measure period. We have already spoken of the
mare’s-tail of antediluvian times; it is seen in the full page
representation, with its glorious head towering high, and the young
shoots peering above the slime. Deep in the forest is a species sending
forth silky streamers; and prostrate is a species of Lepidodendron, or
scaly tree, with branches feathered to the end and bearing cones as scaly
as the tree. Others also shoot out their leaves; the Ulodendron staggers
beneath its large arm-bearing cones, whilst the seal-impressioned
Sigillaria towers high and overtops the whole with its noble crown of
foliage. The roots of the latter lie by thousands on our coal-banks,
showing distinctly whence the smaller fibres started; some are still
connected, being protected by a matrix that formed the sandy soil in
which they grew. Water-reeds and forest trees, green parasitic plants,
ribbed and jointed, sending forth long-entangling feelers, must have
woven a mantle of vegetation rank, matted, and dense in shadow, over the
marshy platform where reptiles lurked at intervals. Of the inhabitants
of those newly-formed forest lands, scorpions, beetles, flies, and a few
reptiles, are all that have yet been found among the relics of the
Shropshire coalfields. Saving the buzzing of a beetle and the whirring
flight of a scorpion, the shaking of great fronds and fruits, and the
sighings of the forest as hot breezes shook the giant pines and rung the
pendant catkins, or the sudden splash of some strange fish seizing upon
its prey, no sounds were heard. Unlike our woods and copses, all was
silence: no songs of birds, no carolling of larks, no warbling of
thrushes, no lowing of cattle, no bleating of sheep, and no human voice
to break the stillness.
[Picture: Fern with wide leaves]
[Picture: Fern with gapped leaves?]
[Picture: Feathered fern]
There were inequalities of surface then as now. The country had its
uplands and its valleys, its rivers and its lakes, its dry and damp
soils, its cool and sunny spots, but with one general genial climate
reigning over all.
* * * * *
We have said on page 284 that Mr. Cranege lived in the house Mr. Moses
now lives in. It should have been, where Mr. W. Hughes now lives,
opposite the Wesleyan chapel.
In mentioning this chapel we might add that the Rev. John Fletcher
assisted in its erection, working and carrying stones like another man,
with his coat off.
The lease for the ground was obtained by John Share from Mr. Reynolds.
Mr. Reynolds told Share he might make out the lease for 99 years. Share
made it out for 99 years and added “and one year more.” Mr. Reynolds
said “Share thou art deep, but I’ll sign it.” The lease has recently
expired and the building has been handed over to the Conference.