The works of the company in the Dale, at Lightmoor, Horsehay, the Castle,
and other parts of Dawley, are so intimately connected and so entirely
dependent upon the mineral resources of the district, that some further
notice is needed to complete this stretch. We said at the commencement
that neither iron nor coal were found here, but in the quotation from the
Philosophical Transactions it is stated that Mr. Ford made iron either
hard or soft from ore and coal got in the dale; and it may perhaps
without being considered a sketch of language be said that the opening
into the Lightmoor valley, where coals were undoubtedly worked at an
early period, is a northern lip or extension of the Dale itself. Indeed
the whole of the rich mineral tract extending from Broseley to the
extreme limits of the Lilleshall Company’s works, some seven miles in
length, and terminating in a Symon Fault on the south-east of Madeley
parish, about four miles in breadth, is universally known as the
Coalbrookdale Coalfield; but the Dale proper is a hollow scooped out of
soft Silurian shale, which shews itself at the railway station, by the
viaduct, on the road to Lightmoor, and in various other places. Here two
great faults or rents in the coalfield meet; one coming down from the
Dunge at Broseley, and the other from the direction of Lilleshall,
causing a difference of level varying from fifty to seven hundred feet.
The coal-measures approach the northern extremity of the Dale on three
sides, forming a fringe which rises from a few feet above the Dale to
three hundred feet above the Severn at Ironbridge, and to over seven
hundred feet at the highest points. It was this outside fringe of lower
coals which tempted early miners, who by means of levels in the hill
sides got their “Smith’s Coal,” leaving others, which they did not then
need for house fuel. Interesting instances of the outcrops of these
coals are to be seen at the surface on high grounds overlooking the Dale,
also on the side of the railway opposite to Black Rock quarry, where an
instructive section of the Best, Middle, and Clod Coals are visible, with
a slight fault displacing them. They crop out on the side of the Lincoln
Hill walks; and on sinking a trial pit at Castle Green near there, many
years ago, it was found that the Middle and Clod coals had been removed,
and the space filled up with gob. The upper coals here, and also the
pennystone, as at the Lodge Pit, remained; but at the latter the clod
coal, the best coal for iron-making purposes, was removed, and the space
filled up with refuse.
When quarrying stone at the Black Rock, on the right hand side of the
tramroad leading to Lightmoor, for the purpose of constructing the
viaduct for the Wellington and Severn Junction Railroad, an interesting
discovery was made of a number of fossil trees. Some were still clinging
to the soil from which they originally derived their nourishment, as here
shewn, somewhat imperfectly, by the accompanying engraving. One was
twelve feet in circumference at the point at which the roots, which were
eight in number, and two feet ten inches in their thickest part, diverged
and spread, at a distance of eighteen inches from the trunk, and divided
into two, and at a distance of four feet dipped into ground. The tree
appeared to have been buried in mud before decay commenced, and to that
circumstance was due probably its preservation from further decay,
portions of trunks and branches were strewed around. We obtained a
photograph and forwarded it to the Illustrated London News, in which
paper an engraving appeared at the time. It was, we believe, a
sigillaria, but was smooth, and shewed few of the marks common to the
genus, such as appear on the accompanying enlarged section of the upper
part of trees of a like kind. The roots also were smooth as far as
exposed. The rock in which the roots were embedded was the Crawstone
crust, and the sandrock which surrounded it was highly charged with oil
or petroleum, derived from the vegetation which had produced the seam of
coal, (the little flint coal) above, or from the decaying trees and
branches of trees which now lie prostrate, and are embedded in the rock
itself. There is one of considerable size at the time we write, five
feet of which is exposed to view, the other part is obscured by the rock;
and at the upper end where it enters the rock is a soft brown substance,
about an inch thick, with impressions of the woody fibre of the tree
itself. It is just that kind of fleshy substance one would suppose to
belong to such trees, and one can scarcely resist the impression that it
is the bark. Examined by the lens it appears to be thickly studded with
small white crystals, strewed about.
[Picture: Fossil tree]
[Picture: Fossil bark]
Interlacing each other are Calamites, the giant representatives of our
mares-tail which still flourishes near in damp places on the surface.
The following representation will afford an idea of the gigantic
proportions they then attained. They are to be found at all stages of
growth; sometimes with their central pith, surrounded by a ligneous
cylinder, divided by medullary rays, and having a thick bark. These
reed-like plants were of course suited to the moist condition then
prevailing, and assumed magnificent proportions.
[Picture: Calamites]
The following is the section as it now appears, commencing at the surface
and taking the measures in a descending order.