opposite Shirts Mill, and in the gap between these two ends a piece' of the upper limestone only is seen at the surface of the ground, dipping about west-south-west.
Fig. 18.
Scale, 2 inches to a mile.
Dark part is Coal-measure ground, with dark lines for coal crops; the part obliquely shaded being above the Thick coal, that horizontally shaded being below it.
Light part Silurian ground, with the limestones. Dotted lines are faults.
On the east side of the Castle Hill, between it and the Tipton road, the beds of limestone, after dipping from the hill for some distance, are found in the under-ground workings to flatten, and afterwards rise again towards the east, so that where the words "Castle-foot pottery" stand in the Ordnance map, east of the Tipton road, the limestone is reached by a shaft at the depth of only 52 yards (156 feet). From this point it again dips towards the east, at such an angle that in the space of 90 yards due east it becomes 112 yards deeps (336 feet).[1]
Wren's Nest Hill.—The Wren's Nest Hill is similar in general structure to the Castle Hill, but differs from it in some of its details. Like the Castle Hill, its general form is that of an oblong dome-shaped elevation, with a central nucleus of lower shale, on which repose the limestones, dipping every way at considerable angles from the centre of the hill. On the south-west side of the hill the beds curve round very symmetrically, dipping west, south-west, and south, at an angle of about 40°. Similarly on the north-east side the two limestones are symmetrically curved, dipping east and north-east, and finally almost
- ↑ This gives us a dip of 60 yards in 90 = 32°.
