The rocks of the South Staffordshire coalfield are pierced locally by sheets of igneous rock. The most important of these is a mass of dolerite about two miles and a half in length, which caps the long ridge of Rowley Regis. It is traversed by several mining shafts, which pass through the dolerite into the workable coals below. Other igneous masses occur near Dudley, and at Pouk Hill, near Walsall. THE EAST WARWICKSHIRE COALFIELD.--The rocks of this coalfield form a narrow strip about 15 miles in length, ranging from Tamworth on the north to Bedworth on the South. The coalbearing strata rest unconformably upon the Cambrian below, and pass up conformably into the Permian above. The sequence of the beds is practically identical with that of South Staffordshire--the richer coal measures being all confined to the lower part of the Carboniferous series, and passing up through a group of coloured clays into a final group of barren sandstones. In the north of the coalfield five workable seams of coal occur, separated by many feet of barren measures. As they pass to the southward the intermediate strata thin out, and the coal-beds practically come together at Hawkesbury to form one Main coal seam, as do the corresponding members of the Thick coal of South Staffordshire. It is probable that the two coalfields were formed in the same general area of deposition, and except for the possibility of its destruction by erosion prior to the deposition of the Triassic, it might be suggested with safety that the Thick coal of South Staffordshire extends in a continuous sheet under the red rocks of Northern Warwickshire from Smethwick to Hawkesbury. FOREST OF WYRE.--Unlike the strata of the other coalfields, the Carboniferous rocks of the coalfield of the Forest of Wyre are comparatively barren of good coal seams. The best, which is locally known as the _Main_ coal, is about seven-and a-half feet in thickness, and occurs at an average depth of 300 feet. COALBROOKDALE.--This coalfield, which lies to the east of the Wrekin, covers an area of about 28 square miles. It originally contained about 28 coal seams, but the majority of these are now practically worked out. The succession includes the Carboniferous limestone, the Millstone grit, and the Lower coal-measures in conformable sequence. The Upper coal-measures rest in a hollow eroded out of the Lower coal-measures beneath, forming what is locally known as the “Symon Fault.” PERMIAN OR DYASSIC. The Permian rocks of the Birmingham District are totally distinct in their petrological characters from those of the typical area of Yorkshire and Durham. No true limestones are present, and the formation is wholly made up of red sandstones, marls and beds of angular breccia.