300 feet. This fault sends out two slight branches, one to the east by the Round Oak, with a downthrow to the south of 5 yards; one to the north-east through Hart's Hill, with a downthrow to the south of 10 or 8 yards. At Pensnett reservoir the Brockmoor fault is believed to branch as shown in the map.
I was informed by Mr. Pearson, of Brierley Hill, that "at Brockmoor this fault threw down to the west 130 yards, or nearly 400 feet, that it was only a slip, but was 200 yards wide, or made that much barren ground." The meaning of which description is, that although the fault itself had no apparent thickness, yet the two ends of the Thick coal were separated by 200nbyards measured on the surface of the ground, showing the fault to have an inclination of not more than 33°.
Corbyn's Hall Fault—The Corbyn's Hall fault strikes out of the Great Boundary fault about a mile north of Bugpool, a little west of Salter's Hall. Its downthrow is likewise to the west and north, at first 360 feet, diminishing then to 300, which it maintains for upwards of a mile. It then curves gradually round to the north-east by Shut End House, diminishing its throw to 240 feet, and thence passing through the north end of Barrow Hill by Hunt's Mill, it strikes east up to Russell's Hall iron furnaces, its downthrow being north 120 feet. I believe this is the fault mentioned by Sir R. I. Murchison in the Silurian System, p. 504. He gives a section of it on the authority of Mr. W. Mathews, in which there is an actual dyke drawn, 140 yards in width, between the broken ends of the coal. Mr. Mathews derived his information from his ground bailiff of that time, but on cross-questioning his present ground bailiff. Mr. Job Taylor. I arrived at a different and more natural explanation of the facts. I may premise, that in South Staffordshire, by the "width" of a fault is always understood the width measured at the surface of the ground, between the broken ends of the Thick coal, or any other bed that may be worked. It is the space of barren ground as to that particular bed, the width of which is measured in yards on the mining plan. It depends, therefore, not on the actual or real width of the fault, but solely on the angle of its inclination. This will be seen from the following account:—Job Taylor first assured me that this was not a fault at all, but only a slip, by which he meant that there was no real width or substance in the fault. He then told me that the "throw" of the fault was 90 yards, and its "width" was exactly the same, as in the following diagram (Fig. 23):-—
Fig. 23
Scale, 1 inch= 150 yards.
A. B. C. Shafts.
D. Gate-road.
1. Beds containing water.
2. Brooch coal.
3. Thick coal.
4. The fault.
A shaft (A in the diagram) was sunk, which crossed the fault between the ends of the pieces of Thick coal, and was therefore said to be sunk in the fault. But from this shaft they drove out a gate-road (D), and
