The red rocks of this _Triassic_ formation not only form by far the most predominant and most conspicuous geological feature of the district at the present time, but not long since, geologically speaking, they must have extended over the entire area in one unbroken expanse. They now constitute a sheet of red sandstones and marls, through which protrude, in numerous bands and patches, the older Paleozoic rocks. Although nowhere very steeply inclined, these red beds of the _Triassic_ have been bent into several long low arches, or broad domes, whose longer axes range approximately north and south. The summits of many of these arches have been denuded, and the underlying older rocks have again been bared to-day. Four of these arches are especially conspicuous, those of the Wrekin, Malvern, Dudley, and Nuneaton. In each of these the underlying _Coal Measures_ are laid bare, forming the four coalfields of Coalbrookdale, Forest of Wyre, South Stafford, and Eastern Warwick, all of which shew round their outer margins a narrow band of the intermediate formation of the _Permian_. In each of these anticlinals, too, the denudation of the core of the arch has been sufficient to wear away the _Carboniferous_ from its centre, and to expose to view yet older formations--the _Old Red Sandstone_ in the Forest of Wyre, the _Silurian_ in South Staffordshire, the Malverns, and Coalbrookdale, and even the _Upper Cambrian_ and its underlying igneous rocks in the Wrekin, the Lickey, and near Nuneaton. With the exception of the _Silurian_ of Abberley and Dudley, and the recently discovered _Cambrian_ of Nuneaton, however, these _pre-Carboniferous_ rocks are comparatively inconspicuous, rising up merely in narrow bands in the cores of long wedge-shaped hills. From the economical as well as from the structural point of view, by far the most important of these geological arches is that of South Staffordshire, which is the southward continuation of the Pennine chain, and part of the true backbone of Southern Britain. The central axis of this arch runs, as we have seen, through the Dudley Hills, and dies away in the complex of faults to the south of the Lickeys. On the natural consequences of the rise of this arch, all the physical, scenic, and economic peculiarities of the central parts of the district are essentially dependent. The hills and plains around Birmingham are all more or less related to this grand anticlinal--the hills marking the uplifted edges of the harder rocks, the limestones, sandstones, and pebble beds; and the plains, the position of the gently inclined soft shales and marls. It has brought within workable distance of the surface the coals and ironstones of South Staffordshire, and the valuable limestones of the Dudley Hills, and it has had its final effect in bringing together the overflowing population of the town and district.