and for the same distance to the northward, varying in thickness from 20 feet to 40 feet, lying always just above the Bottom coal, which is often greatly injured by it. It does not extend as far east as the Birch Hills,[1] nor far north towards Bloxwich, nor beyond Clark's-lane to the westward, neither was any found in Messrs. Bates's pits at the Trentham colliery between Mumber-lane and Wednesfield.
Near Wolverhampton none has been found in the Rough Hills. Cockshutts, or Parkfields collieries. At the Chillington colliery it is found, however, sometimes above, sometimes below the Bottom coal, and varying from 15 feet to 30 fect in thickness.
I was assured by Evan Lloyd, the ground-bailiff of the Chillington colliery, that there were two distinct beds of "green rock" there, as in the two following sections:—
| Western part of the Chillington Colliery. | Eastern part of the Chillington Colliery. | ||||
| FT. | FT. | ||||
| 1. | Black and white ironstone | 3 | 1. | Black and white ironstone | 3 |
| 2. | Bottom coal | 12 | 2. | Green rock, about | 15 |
| 3. | Clunch | 24 | 3. | Bottom coal | 12 |
| 4. | Gubbin and ballsironstone | 8 | 4. | Clunch | 24 |
| 5. | Slums | 3 | 5. | Gubbin and balls ironstone | 8 |
| 6. | Green rock, about | 35 | 6. | Slums | 3 |
| 7. | Hard rock | 12 | 7. | Hard rock | 12 |
Notwithstanding these facts the Gubbin and balls ironstone was worked continuously over the whole colliery without meeting any green rock. In this locality, therefore, there could have been no cutting up of the green rock through the measures, though it is by no means sure that these two sheets may not have a connexion elsewhere.
I was assured also by almost every one engaged in the works of this neighbourhood that, notwithstanding the variations in thickness of the "green rock," there was no change in the total thickness of the measures; that, for instance, the thickness between the New mine coal and the Blue flats ironstone remained the same, whatever might be the variation in the thickness of the "green rock." In other words, it was affirmed almost universally that the "green rock" not only intruded between the measures, but obliterated a mass of beds equal to its own thickness. This assertion was so confidently made by almost every practical man in the neighbourhood, that, however incomprehensible. I should have received it as true, had not an analysis of the materials received from them enabled me to disprove it. It is no doubt founded in fact; the greater the thickness of the intruded trap rock, the more intense, probably, would be the squeeze, and the consequent contraction suffered by the adjacent beds. Beds of coal, too, might certainly be nearly or altogether annihilated by the intrusion of molten rock, but we cannot conceive sandstone or clunch being thus destroyed. The truth is, that the original thickness of the measures was itself very variable, and it probably happened that, in one or two of the places where the facts were first observed, 2 partial thickening or thinning of the trap rock compensated for the reverse in the original beds. It may also have happened that the very fact of there being a local thinning of some of the upper measures gave occasion for a corresponding thickening of the intruded trap rock. That, however, the assertion before
- ↑ Beyond the Birch Hills furnaces, however, near Birch Hills Hall, trap is again found in the Coal-measures, about or above the place of the Bottom coal.
