come to the space south of Tipton occupied by the Dudley Port Trough. The pair of faults forming the a Port Trough run parallel to, eat almost in the same line with, the Netherton anticlinal. They tend, however, to produce a synclinal rather than an anticlinal effect, and the faults on each side of them aid that effect, since their downthrow is always towards the Trough. The faults running parallel to the Trough which strike from the northern flank of the Rowley Hills are mostly upthrows to the south-east till we approach the Brades, when they again have a southerly downthrow.
Beyond these the Coal-measures stretch into what we may call the south-eastern end of the central district, in which the beds lie nearly flat, as about Titford and Causeway Green, between the Rowley Hills and the eastern Boundary fault.
North of the Great Bentley fault lies the northern portion of the coal-field, in which the dip of the measures is at first steadily from east to west, at a mean angle of about 3°, gradually curving round till it dips west-north-west, and then apparently north-west at the same low angle, over Cannock Chase up towards Brereton. In the Old Park of Beaudesert, however, they appear to become first quite horizontal, and farther on at Brereton they are said to dip gently to the south-east, and to rise towards the north-west and crop up into the New red sandstone that lies upon them.
Many faults running chiefly east and west traverse the northern art of the coal-field, especially the part of it between the Great Bentley fault and Cannock Chase.
Trough Faults.—Besides the faults which have already been mentioned by name, there exists many others, some of which have been alluded to, in all parts of the coal-field. Their description must be left till we speak of them in detail, but it will be well first of all to call attention to those among them which dominate over the rest, and seem to bear to them a relation analogous to that which the keystone bears to the arch.
These are the Trough faults, of which we may enumerate six.
Two of these are in the Pensnett Basin, namely, the well-known Brierley Hill Trough, which runs nearly due east and west, and the less marked Tansy Green Trough, which, likewise, has a general east and west extension.
The central district has only one, but that is the largest and best marked of all, namely, the Dudley Port Trough, which runs nearly north-north-east for three miles, and then gradually curving round seems to merge into the system of east and west faults that traverse that portion of the coal-field.
The Great Bentley fault is itself the southern side of a trough, though of an unequal and imperfect character, since the amount of the upthrow of the corresponding fault on the northern side is only about one-fifth or one-sixth of the downthrow of the Great Bentley fault itself.
