§ 14. CARBONIFEROUS OR MOUNTAIN LIMESTONE. 679 



coal used for economical purposes, are in some countries 

 situated in this division of the system. Layers and nodules 

 of chert occasionally traverse the limestones, like the flints 

 in chalk. 



The term Mountain limestone, applied to these calca- 

 reous rocks, has originated from their often forming elevated 

 mountain chains, as in Derbyshire, Yorkshire, Somerset- 

 shire, &c. giving rise to scenery which equals, if not 

 surpasses, in picturesque beauty that of any other part 

 of England. I need but mention the vale of the Avon at 

 Clifton, Matlock- dale, Dovedale, the escarpments that over- 

 hang the Wye near Chepstow, &c. The magnificent gorge 

 of the Avon at Clifton is flanked by an uninterrupted suc- 

 cession of mural precipices, known by the name of St. 

 Vincent's Rocks, and presents an unrivalled natural section 

 of the carboniferous limestone. The calcareous beds rest 

 conformably on strata of the Devonian system, which may 

 be seen on both sides the river, near Cook's Folly, extending 

 on the south under Leigh-down and Weston-down.* 



This series of strata is also remarkable for the deep 

 chasms and fissures by which the rocks are traversed ; the 

 principal caverns of this country being situated in them ; 

 those of Derbyshire, Yorkshire, Somersetshire, &c. are 

 well known. Subterraneous rivers are likewise frequent 

 throughout the districts formed by these deposits. 



The mountain limestone is largely developed over the 

 central and northern parts of England, and the south-west 

 of Scotland : and is the predominant rock throughout a 

 great part of Ireland. In Somersetshire, Gloucestershire, 

 Shropshire, North and South Wales, and Derbyshire, it 

 constitutes as it were an entire calcareous mass, which is 

 interposed between the Devonian group ; or, where that is 

 wanting, between the more ancient Silurian rocks below, 



* See Excursions to Clifton and Matlock-dale, and Crich Hill; 

 Medals of Creation, vol. ii. pp. 929, 933. 



