716 



DESCRIPTION OF THE SECTIONS. 



affecting the Oswestry coal increase in intensity on the rise. The coal is seen to be worked 

 in recent shafts through the Lower New Red Sandstone. The Millstone grit and Carboniferous 

 Limestone are largely developed, but the Old Red Sandstone and younger Silurian Rocks are 

 wanting. See pp. 64, 141 et seq. 



PLATE 31. 



Fig. 1. From the Millstone Grit and Carboniferous Limestone, forming the edge of the South 

 Welch coal basin near Abergavenny, to the Upper Silurian Rocks of Radnorshire, which 

 constitute the Begwm and Pains Castle hills on the left bank of the Wye. In this section 

 the vale of the Usk has been the scene of a powerful dislocation, to the north-west or upcast 

 side of which is the remarkable and lofty outlier of Carboniferous Limestone " Pen-cerrig- 

 calch " (borders of the Black Forest). This section is chiefly designed to exhibit the enor- 

 mous development of the Old Red System in this part of England (Herefordshire), and its 

 subdivision into 1. Conglomerate and sandstones. 2. Cornstones, marls and sandstone. 

 3. Tilestone, &c. Although this section traverses a contortion of the Ludlow Rocks, near 

 their j unction with the Old Red Sandstone, (the line of the Ludlow and Brecon anticlinal), the 

 prevalent arrangement along the Begwn and Clyro Hills, exhibits ^perfectly conformable pas- 

 sage from the one system into the other. See Map and pp. 156, 163, 171, 176 et seq., 336 et seq. 



Fig. 2. Section of the Upper Silurian Rocks as they appear in the neighbourhood of Ludlow, 

 explaining the subdivisions of the Ludlow and Wenlock formations on a larger scale than in 

 the other figures. See pp. 196 et seq. 



Fig. 3. From the coal-field of the Titterstone Clee Hills to the Cambrian Rocks of the Longmynd, 

 exhibiting a succession of the Ludlow and Wenlock formations rising from beneath the Old 

 Red Sandstone and underlaid by the Caradoc Sandstone, the latter being fully developed on 

 the banks of the Onny, though in hills of low altitude. The volcanic axis of Caer Caradoc 

 breaks in upon the sequence of the Lower Silurian Rocks and no Llandeilo Flags are visible. 

 See pp. 124, 174, 179, 196, 216 et seq., 256 et seq. 



Fig. 4. From the coal measures and basalt of the Brown Clee Hills to the quartz rock of the "Stiper 

 Stones " (north-eastern end of the mining tract of Shelve) ; passing over the same succession 

 of Old Red Sandstone and Silurian Rocks as in f. 3., with examples of the conversion of 

 Caradoc sandstone into quartz rock by the outburst of volcanic matter. (Caer Caradoc.) Trap is 

 seen protruding at many points through the Cambrian Rocks, and copper and lead ores occur 

 occasionally near the contact. A remarkable outlier of Ludlow Rocks is seen at Botville, near 

 Church Stretton, in a vertical position on the north-western face of the trap of Caer Caradoc. 

 See pp. 122, 174, 196, 216, 220, 231 et seq. 



Fig. 5. Section across the Ludlow promontory, exposing in its centre the valley of elevation of 

 Wigmore Lake. A double upcast is seen to the south-east and a single upcast to the north- 

 west, the descending series from each flank being Old Red Sandstone, Ludlow Rocks, Wenlock 

 Limestone, and Shale, the latter occupying the centre of the denudation. This is a stri- 

 king point of the great Ludlow and Brecon anticlinal which is traceable by Old Radnor, and 

 the Wye at Erwood, and reappears to the south-west near Brecon. See Map and pp. 196 

 et seq., 238. 



Fig. 6. Traverse from five miles north of Brecon to the hills of Llwyn Madoc passing over the 

 "Brecon anticlinal," a ridge composed of Ludlow Rocks which at Castel Madoc are thrown 



