718 



DESCRIPTION OF THE SECTIONS. 



and Coed Way (full of faults) rests on the edges of the Silurian rocks and passes conformably 

 under the Lower New Red Sandstone and Dolomitic Conglomerate of Pecknall and Alberbury, 

 See pp. 587 et seq. 



Fig. 8. Alteration and dislocation of the New Red Sandstone, as seen at Pirn Hill, upon the line of 

 the eruptive axis of the Breidden Hills. This spot is between the great outburst of trappean 

 matter and the dykes composed of the same at Acton Reynolds. (See Map for the extension of 

 this line of dislocation into Staffordshire.) See pp. 587 et se( J- 



Fig. 9. General section from the Long Mountain across the Vale3 of the Severn, Ffirnwy and Tannat, 

 to the south-eastern flanks of the Berwyn mountains, near Llanrhaidr, explaining how the 

 strata of the Silurian System are extended by a number of undulations over so wide an area. 



In proceeding from the south-east, the Caradoc sandstone and its impure limestone are seen 

 to rise from beneath the Upper Silurian Rocks at Powis Castle. Troughs of Upper Silurian rocks 

 (mudstone) succeed. The Caradoc Sandstone re-appears upon the left bank of the Fyrnwy (Allt- 

 y-maen) and is continued by rapid undulations to the vale of the Tannat. The Llandeiio Flags 

 with Asaphus Buchii, JEncrinites and other fossils, and forming the base of the Silurian 

 System, rise from beneath the Caradoc formation and pass down into the slaty Cambrian schists 

 of the Berwyns. 



This section, so important in the verification of the order of succession, may be considered 

 the prolongation of figs. 1 and 2. The north-western part of it, including all the tract between 

 the Ffyrnwy and the Berwyns, was inserted by Professor Sedgwick, in company with whom 

 the author first examined that district. See pp. 300, 306 et seq. 



PLATE 33. 



Fig. 1. From the Longmynd on the north-east, to the hills on the right bank of the Ithon, near 

 Llanbadarn fynidd, exposing a vast trough of Upper Silurian rocks and Old Red Sandstone ; 

 the Silurian rocks resting unconformably at either end upon Cambrian rocks, the connecting 

 Lower Silurian strata being wanting. The great outlier of Old Red Sandstone which occupies 

 Clun Forest, exhibits on most sides conformable passages into the Ludlow Rock. See pp.258, 

 300, 311 et seq. 



Fig. 2. From the south-east of Kington to the north-west of Nash Scar near Presteign ; showing a 

 regular succession through the Ludlow formation, as it appears in Herrock Hill, to the Wen- 

 lock Limestone and Caradoc Sandstone. These formations being upon a line of volcanic 

 eruption, the limestone is for the most part unstratified and crystalline, and the sandstone is 

 heaved up in a mural form with an outlier of Old Red Sandstone on the north-west. Another 

 line of dislocation is seen at Kington, near the junction of the Old Red Sandstone and Upper 

 Ludlow Rock. See pp. 311 et seq. 



Fig. 3. Traverse of the trappean hills (chiefly Hypersthene Rock and greenstone) of Stanner and 

 Old Radnor, showing how their eruption has dislocated and altered the Ludlow and Wenlock 

 formations. (Thin veins of lead ore appear on the sides of the trap of Old Radnor.) Seep. 318. 



Fig. 4. From the Old Red Sandstone on the right bank of the Arrow near Kington, across the hills 

 of Hanter and Old Radnor, exhibiting the trap bursting through the Ludlow and Wenlock for- 

 mations, with slight traces of the Caradoc sandstone ; all the strata being highly dislocated, and 

 in parts much altered. Passing to the W.N.W., the section exposes the denudation of the 

 vale of Radnor, and a fine development of Upper Silurian rocks (chiefly the Ludlow formation) 

 in the mountains of Radnor Forest. See pp. 318 et seq. 



