Under the management of Mr. John Fox the clay-works of the Coalbrookdale Company have become so expanded and improved, that they now form an important department of the Company’s undertakings, and are at the present juncture, no doubt, among the more profitable of their industries. Since sanitary science has so successfully called public attention to the importance of the use of good bricks impervious to damp, the productions from these excellent coal-measure clays have been more in demand. Clays, as commonly understood, mean earth of sufficient ductility to allow of being kneaded into some useful shape or form, and rank as raw materials. Some are soft, others are indurated, or hard and rocky; but all have in one sense been prepared by certain poundings, grindings, washings, and mixings, carried on by Nature on a larger scale than that on which they are now still further fitted for use. They differ in quality, in degree of fineness, and in colour, and show certain relationships by which it is clear that they are descended from sand, just as sands are descended from a hardy race of pebbles, which in turn bear close relationship to rocks, from which undoubtedly they have been derived. Surface clays used for making inferior bricks and tiles, whose earthy odour gives evidence of alumina, are generally derived from red sandstone rocks, ground down into mud by the machinery of waves or streams whilst our deeper coal-measures clunches, and clays were originally the sediment thrown by rivers at their embouchures into inland lakes or seas, and are usually much more free from lime, iron, grit, and other foreign substances and impurities.
When brought to the surface, these clays are hard as a rock. Formerly they were allowed to lie during the winter to weather, as it is called; and a statute now obsolete required, under a heavy penalty, that bricks should not be made unless the clay for making them had been turned over at intervals, three times at least before the first of March. But brickmakers, not having patience to wait for the action of the weather, have invented machinery to do the work, and the clay is taken direct from the pit to be crushed by iron rollers, and then conveyed by coarse canvas-screens to tanks to be moistened, and afterwards to the pug mill. This is an upright cylinder, with a revolving vertical shaft, fitted up with horizontal knives following each other at an angle so as to cut, amalgamate, and temper the material, and which also acts as a screw to deliver it.
Ornamental bricks of elaborate design for architectural purposes require more delicate manipulation, and the clays for these undergo a more careful preparation. Machines in some instances are used, which take the clay, temper, thoroughly amalgamate it, and convert it into the finished article, and at the brick-yards of the Coalbrookdale Company presses have been erected by which bricks may be stamped at once from the semi-dry clay.
This company, too, have been at great pains to turn their clays to account by copying the Italian and Lombard style of making bricks of various forms and colours; and the buildings erected with these bricks, and others, with white facings of the same material, of which the present Literary and Scientific Institute is an example, possess great architectural beauty. Still further examples of the æsthetic treatment of these admirable clays were made a short time ago by Monsieur Kremer, who modelled and prepared at the company’s Lightmoor clay works, in relief, and on a large scale, an historical subject, connected with Scottish history in the time of King James, as a facade for a house in London; also some noble groups, life size, of figures representing the four seasons, for a gentleman’s grounds and park near London. The reader may judge of the adaptability of these clays for such purposes by inspecting a group of a similar kind in front of the Institute.
We exhibited ourselves in 1851 specimens of these and other coal-measure clays, with articles manufactured from them on both sides the river, and we had the satisfaction of hearing from distinguished judges, familiar with their merits, such as presidents of foreign Academics of Science, speak of them as superior to any they had ever seen. [306]
Coalbrookdale Coalfield.
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.
