§4. DEVONIAN STRATA OF DEVON AND CORNWALL. 



753 



borders of Herefordshire, near Kingston for example; 

 whence casting his eye to the south and south-east, the 

 circle of vision, although extending over all the hills 

 between the Wye and the Usk, and terminating only in 

 the lofty mountains called the Brecon and Caermarthen 

 Fans, 2,500 feet above the sea-level, embraces nothing 

 but Devonian sandstone. This view does not include 

 a wide superficies, occupied merely by undulating masses 

 of the same strata, but a territory in which successive 

 members of the system rise from beneath each other in 

 distinct mountainous escarpments. The same succession, 

 though on a much smaller scale, is displayed in Shropshire, 

 between the coal-field of the Clee Hills and the older rocks 

 of Ludlow ; whilst in the central districts of Herefordshire 

 the strata lie in a great basin, the lower edges of which are 

 turned up against the Silurian rocks, both on their eastern 

 and western flanks."* 



The red conglomerates of this system are well displayed 

 on the right bank of the Wye from Monmouth to Tintern 

 Abbey (Medals, p. 930) : and beds of the Devonian sand- 

 stone and conglomerate form the base of the mountain lime- 

 stone at the embouchure of the Avon, and the central 

 nucleus or axis of the Mendip Hills {ante^ p. 522). 



4. Devonian strata of Devonshire and Cornwall. 

 — In the south of Devonshire, in many places dipping to- 

 wards the anthracite or carboniferous shales of the northern 

 part of the district {ante, p. 683), there is an extensive series 

 of strata, composed of green chlorite slates, alternating with 

 quartzose shales and sandstones, with blue and grey lime- 

 stones, which pass into, or are associated with, red sandstones 

 and conglomerates. Many of these beds abound in organic 

 remains. The slates of Devonshire were formerly regarded 

 as belonging to the earliest or most ancient fossiliferous 



* Silurian System, p. 170. 



