scale a very great amount of unconformability between two formations, and in this special case we see the nature of the relation between the Coal-measures and the Silurian, rocks of the South Staffordshire coal-field; that the Silurian rocks were greatly denuded and worn away, and cliffs and hollows formed in them, on, against, and over which the Coal-measures were deposited, both lying in a nearly horizontal position.
In the district south and west of Dudley there has been no pit sunk from any of the known beds of the Coal-measures down to the Silurian, unless they reached that formation in the Blackheath colliery, south of Rowley Regis (see Vertical section, sheet 18, No. 26). In that abortive search for valuable coal or ironstone, they reached, at 570 feet from the surface, the representative of the Thick coal in a debased and worthless form, and they sank to a depth of 121 feet below it, meeting with only a few trifling beds of coal or ironstone. At a depth of 661 feet from the surface, and 81 feet below the Thick coal, they met what is described as "red parting and limestone, 1 inch," and below that they found thick and regular beds of "rock binds," separated by inch partings of white clay. Now if the sinkers had never before worked in the Silurian rocks they might easily have described those as "rock binds," and they bored through precisely similar materials for 300 feet below the bottom of the shaft. This statement makes it very probable that the last 340 feet out of the 1,001 feet passed through altogether, consisted of Silurian shale, since it is totally contrary to the nature of the South Staffordshire Coal-measures to maintain one lithological character through so great a thickness. If these rock binds were Silurian shale, then there was only 81 feet of Coal-measures between it and the Thick coal in that locality.
The nearest deep sinking to this that I am aware of is the one at the Level colliery north-east of Brierley Hill, made by Mr. Benjamin Gibbons, and quoted by Sir R. I. Murchison in his Silurian System, p. 478. Of this pit we have already investigated the details, and endeavoured to identify the lower coals. The following abstract will give us all further necessary information about it:—
| FT. | |
| To the bottom of the Thick coal | 240 |
| To ditto of 2nd Heathen ditto | 18 |
| To ditto of Stinking ditto | 34 |
| To ditto of New mine (?) ditto | 37 |
| To ditto of Fire-clay (?) ditto | 15 |
| To ditto of Bottom ditto | 29 |
| To ditto of (small coal and batt 8 in.) | 19 |
| Alternations of "rock," fire-clay, clunch, and binds, varying from 2 feet to 10 feet each | 109 |
| Dark gritty rock, with conglomerate | 26 |
| Light blue clunch | 3 |
| Below which they bored in red clunch | 60 |
| 590 |
Making a total of 217 feet below the Bottom coal, or 350 feet below the Thick coal, without meeting with anything that appears like Silurian rocks.
