"fire-clays" contain the Stigmaria roots, properly permeating their ancient soil, there is usually a little difficulty in practically tracing their crop, but when the mineral matter of these beds takes the more ordinary form of a sandstone or arenaceous shale, the case is different. Then an examination of the mode of occurrence of the Stigmaria roots themselves is essential, especially when the lithological character of the bed may be liable to change, and in some coal districts we have been enabled to trace the same Stigmaria bed from the ordinary condition of a fire-clay to a rock in which the arenaceous matter greatly prevailed.[1]
Note on the Mode of working the Coal and Ironstone of South Staffordshire. By Warington W. Smyth, M.A., Professor of Mining and Mineralogy to the Museum of Practical Geology.
A brief sketch of the modes of working the beds of coal and ironstone in South Staffordshire is appended, with a view of recording generally the practical methods, adopted at the present time, for the extraction of those rich stores of mineral wealth of which the geological relations have been described in the preceding pages.
The acknowledged requisite for the most advantageous method of working, viz, the combination of the cheapest mode of extracting the greatest possible quantity of mineral, with the safety and comfort of the men, has in this district been greatly modified by the circumstances of position, and an adherence to long established customs. In a few rare instances only have any attempts been made to substitute a new system for the old routine, and to such it will be needful to advert after we have viewed the principal features of the practice almost universally followed.
in the first place, the division of the ground into separate works is guided by the faults which in so many instances constitute natural boundaries and by the depth from the surface, of the deposits proposed to be worked; and an observer, conversant with districts of coal where extensive unbroken areas are worked at great depths by few shafts, cannot fail to be struck with the appearance of the South Staffordshire field, dotted over as it is with innumerable shafts, and deformed by the large waste heaps of slate and slack which so frequently surround them. The cause of this, lying in the subdivision into small arcas, and the comparative shallowness of the workings, and conducive no doubt to simplicity in all the internal arrangements, afford such facilities for securing the desiderata above alluded to, that it must be a matter of surprise to find that certain ancient incomplete usages should so long have held their ground.
The shafts by which access to the coal and ironstone measures is to be obtained, are sunk two together, at a distance of six or eight yards asunder, and with a diameter of six or eight feet. Each shaft being
- ↑ The consolidation of Stigmaria beds is occasionally very considerable, even approaching that of quartz rock. Good examples of Stigmaria beds thus consolidated may be seen on the coast (at Lilliput) near Swansea, where from the infiltration of silica, two beds, each supporting small beds of coal, and penetrated by Stigmaria roots and rootlets in their relative places of growth, have become hard quartz rocks.
