which sends out veins into the adjacent Coal-measure sandstone, and is therefore intrusive. It is not at all necessary, however, to look upon the intrusion of this mass of trap as contemporaneous with the formation of the anticlinal elevation.
The Cradley Basin.—It appears from former and recent information that a fault runs parallel to the Netherton anticlinal on the eastern side of it, from Careless Green to the neighbourhood of Musham. I believe this fault, however, to be merely a fracture, with but a slight displaces ment, in the Thick coal and other measures where their "lie" changes suddenly from a nearly horizontal to a highly inclined position.
From this line of disturbance they appear to stretch across very uniformly and nearly horizontally under Cradley Heath. Congreaves, and High Haden, as also under Dudley Wood and Old Hill, till they reach the Russell's Hall fault before described, when they are suddenly bent up at a sharp angle as well as broken and heaved to a height of 300 or 400 feet.
A few small faults are met with about Baremoor and Congreaves, as shown on the map, and another small east and west fault runs through the Hawn Colliery with a downthrow of 30 feet to the south.
As the beds dip to the south, while the ground rises rather rapidly in that direction, it follows that the uppermost beds of the Coal-measures must soon make their appearance. We accordingly find the Halesowen sandstone group stretching across the coal-field from east to west, and above those we soon meet with the red beds of the Permian formation.
On the road from Halesowen to Hagley two considerable patches of Permian rock are seen to rest on the upper sandstones of the Coal-measures; one at Quarry Hill and Hasbury, and the other at Hayley Green. These Permian beds dip to the southward; but in the brook immediately south of them good Coal-measure beds can be seen, and farther south in Uffmoor Wood one, if not two, little coals have been found, and may be seen cropping into the brooks. It is clear, therefore, that these two Permian outliers are cut off to the southward by a fault which is an upcast to the south, and runs about east-north-east and west-south-west along their southern boundary.
The southern boundary of the coal-field stretching from Wychbury Hill on the west, to Lappal tunnel on the east, is formed by the horizontal beds of the upper Coal-measure sandstones and shales becoming covered as we ascend the rising ground to the south, by the horizontal beds of the Permian rocks.[1] It will be seen accordingly, by inspection of the map, that this boundary, instead of being smooth and regular, like that of the east and west sides of the coal-field, is indented and undulating, depending chiefly on the shape of the ground. Wherever a valley sufficiently deep penetrates to the south, there is a bay of Coal-measures marked in the map. Wherever a ridge sufficiently high stretches to the north, a promontory of red rock will be seen advancing in that direction. We have here, therefore, a true natural surface boundary of the coal-field, caused simply by the irregular denudation of the rock that covers it.
Pensnett Basin.—The Pensnett Basin is bounded by the Netherton anticlinal on the south-east, the south-western slopes of the Dudley and Sedgley ridge, and the northern part of the Russell's Hall fault on the north-east and the Western Boundary fault on the north-western and south-western. Instead of declining gently to the north and passing
- ↑ By horizontal is here meant "apparent horizontality" only. There may be a slight dip to the southward of 2° or 3°, every geologist knowing that it is impossible to detect such a slight variation from horizontality with anything approaching to certainty or accuracy, except under very favourable circumstances.
