and the expense that would be incurred in separating the two substances if that were attempted. (See postea, p. 50).
All the evidence then at present known gocs rather against the value of the coals and ironstones to be found in the corner of the coal-field that lies south of Oldbury, and east of Rowley Regis and Halesowen, for although particular spots may possibly contain workable beds of coal, yet the hitting on those spots must always be a matter of chance, as there seems to be no indications in the general mass of the ground to lead up to them.
North of Oldbury I know of no important variation in the character of the Thick coal, either towards Tipton or Wednesbury, until we return to the district near Bilston, already described.
In the Thick coal worked beneath the Lower red sandstone, or Permian of West Bromwich, the thickness is described as only 27 feet or 28 feet; but it appears to be all solid coal, with none but the most insignificant partings.
Rock faults, swells, rolls, &c.—There are some remarkable peculiarities and irregularities of structure, which, although by no means peculiar to the Thick coal, but occurring now and then in all beds of coal in all coal-fields, are yet so well seen in the Thick coal on account of the scale on which they are exhibited, that it is worth while to take this opportunity of describing them a little more in detail.
One kind of irregularity has been just alluded to, namely, the occurrence of sandstones in the mass of the coal, or in the place of it. This is often spoken of by the miners, under the name of a "rock fault," a term we may use for want of a better, though it is apt to give rise to confusion, unless it be carefully distinguished from the true " fault," a dislocation which is quite independent of the character or quality of the beds.
Rock faults seem to be of two kinds, the one like that described by Mr. Buddle, under the name of "The Horse," as occurring in the Forest of Dean coal-field, which seems to be the result of a partial denudation or wearing away of the coal just subsequent to its formation, the hollow thus eroded being filled with whatever substance it was that was next deposited on the top of the coal. The other kind of rock fault arises from the contemporaneous deposition of sand or silt together with the coal, so that the formation of the two alternated at comparatively short intervals and over a comparatively small space, so that the whole coal incloses cakes, layers, or masses of sandstone of greater or less magnitude, and more or less intermingled with it. These masses may sometimes apparently be so large as over a certain part of the area to exclude the coal altogether, although they dove-tail into it, and are interlaced with it in interstratified layers round the margin of the area.
I never had the opportunity of personally examining an example of the first kind of rock fault. Mr. Aaron Peacock, however, described one to me as occurring a little west of Oldbury, in the Gower pits at the northern foot of the Rowley Hills. According to this description, which was very carefully given, there was a gap in the Thick coal 60 yards wide, and of much greater length. The bed on which the Thick coal rests is there called the "pouncill batt," and he described this as running under the Thick coal and across the gap the whole way with great regularity. The Thick coal was said to end on each side with a smooth slope, and the Broad earth or Cat earth above the coal was described as coming down over this slope, and running along upon the
