Essington Wood, those of Rumour Hill near Cannock, and of Littleworth on Cannock Chase. They are largely opened for brick pits, the bricks being hard blue bricks of a superior quality and peculiar appearance. The beds in those northern localities consist principally of dark purplish-red clay, mottled and streaked occasionally with green, and interstratified not unfrequently with soft reddish or brown sandstones. They appear to constitute a group of very considerable thickness, since they have been sunk through for more than 200 feet at the Coppy Hall colliery, just at their edge, and have probably a total thickness of at least double that. They are nowhere known to be covered, in the northern part of the coal-field, by any group of greenish or brownish sandstone, as they are near Halesowen and the neighbourhood, but possibly they may have been so originally, after having, like the other coal-measures, swelled out to a greatly increased bulk on the north over that which they possessed on the south side of the district.
Having thus traced the beds over the Upper Sulphur coal, together, perhaps, with some of those in which it lies over the whole coal-field, we, will now turn to the detailed descriptions of the beds mentioned in the first general section given at page:
2. The Upper Sulphur Coal.—The Upper Sulphur coal is itself a small and insignificant bed, rarely if ever exceeding 1 foot 6 inches in thickness; it has never been "gotten," nor would it be worth the trouble of extracting. Like most other small coals, it is local only, and is altogether wanting in some shafts that go through the beds in which it is found at other places.
3. Intermediate Measures.—The intermediate measures, between the Upper Sulphur coal and the Two-foot, have a mean thickness of about 150 feet, which thickness, wherever the two coals are undoubtedly present, does not seem to vary more than 37 feet. The variations in thickness seem to be due to the greater or less abundance of sandstones. The beds are chiefly argillaceous, being designated usually by the terms "bind," "clunch," "ground," "fire-clay," &c., but having several interstratified beds of various kinds of "rock" or sandstone. Like the beds before described, as we go south the sandstones begin to thicken and predominate, and become in some instances conglomeritic.
4. Little or Two-foot Coal.—Although this coal has never been worked or "gotten," its thickness not being sufficient to allow it to be got with profit, it is yet a very persistent bed, as its presence is noted in all the detailed pit sections we have which pass through its place. It varies from 1 to 2 feet thick, but I know nothing of its quality, nor whether any trials of it have been made.
5. Intermediate measures between the Little coal and the Brooch.— These beds are almost universally clunch, binds, fire-clay, or some argillaceous material; but in one or two cases they contain beds of rock or sandstone. Their thickness in all the central portion of the field varies from 13 to 48 feet, the mean being about 25 feet. As we go south and west, however, into the district of Congreaves. Cradley, and the Black Delph, the thickness of these beds rapidly diminishes, and they vary only from 2 to 7 feet, consisting of fire-clay or batt, or both. In some places in the neighbourhood of Kingswinford, as also in the district last referred to, a little coal makes its appearance occasionally in these beds, but is too unimportant to require a separate notice.
6. (I.) The Brooch Coal.[1]—This is the uppermost workable coal in the coal-field; it is almost invariably of excellent quality, and in
- ↑ Sir R. I. Murchison, in his account of this district in the "Silurian System," derives this word from the measures having been first "broached" or entered on by this coal. Historically. I believe this was not the fact, as the first working seems to have been along the crop of the Thick coal. I venture to conjecture that the name is derived from the old-used word "broche," a spit, as this coal makes an excellent fire for roasting at.
