CARBONIFEROUS LIMESTONE. 163 



walls, etc. Some of the beds are polished and used as marble for ornamental 

 purposes. The Derbyshire marble is found very serviceable for chimney-pieces 

 and other ornaments, and from its varied characters is known as Black, Rosewood, 

 Shelly or Mussel, Bird's-eye, Dog's-tooth, Coralloid, Entrochal, or Encrinital 

 Limestone. Formerly there were Marble Mills at Mells, in Somerset. 



In the southern part of the Lake District may be mentioned the Kendal grey 

 marble ; while, near Egremont, the Cleator Limestone is of local repute. 

 Carbonaceous and bituminous matter appear to be the colouring principle of the 

 darker beds, and its irregular diffusion constitutes the beauty of some marbles in the 

 North of England. The Beetham Fell Marble, near Milnthorpe, Westmoreland, 

 is a remarkable instance, it is of a cloudy character.^ In some places the upper 

 beds partake so greatly of the nature of chert as to be unfit for the purposes of 

 the lime-burner.' In Flintshire, and other places, where these beds crop out on 

 the surface, masses are ploughed up from beneath the soil, exhibiting the casts of 

 the inside of Crinoids in chert ; these are commonly called scrriv-stones. Blocks of 

 these wexQ heretofore used in the forming of millstones, which were employed 

 instead of the French buhr-stone. 



Elaterite, or mineral caoutchouc (popularly known as "mineral india-rubber "), 

 an elastic variety of bitumen, which emits an unpleasant odour, is met with at 

 Windy Knoll, near Castleton. 



The Carboniferous Limestone has yielded ores of zinc and lead in the Mendip 

 Hills, Derbyshire, Cumberland, Westmoreland, the north-west of Yorkshire, 

 Flintshire, Denbighshire, etc. There are "Old lead works" between Llangan 

 and Penlline, about four miles south-east of Bridgend. 



The Haematite of Ulverston, Whitehaven, and Cleator Moor, and the Ironstone 

 beds of Ridsdale or Redesdale in Northumberland, occur in the Carboniferous 

 Limestone series ; while in some places Iron-ores occur in pockets of the Limestone 

 beneath superincumbent New Red rocks, as south of Lla.ntrissant, in Glamorgan- 

 shire. Fossils are met with in the Haematite of Cumberland and other places. "^ 



In the Forest of Dean, iron-ore was worked during the Roman occupation ; the 

 ore occurs in pockets at the top of the Limestone. 



Barytes (Sulphate of Baryta) or Heavy Spar occurs in Derbyshire, and has been 

 raised there for use as a pigment, and for the adulteration of white lead. Fluor 

 spar (Fluoride of Calcium) is found in Cumberland and Derbyshire ; in the latter 

 county a blue or purple nodular variety, generally known as ' Blue John,' is 

 obtained at the Blue John mine at the foot of Mam Tor, near Castleton, where it 

 lines veins in the Carboniferous Limestone. It is manufactured into ornaments. 

 Portions of veins of calc-spar coloured with iron-oxide are sold at Bristol as 

 "Bacon Stone." Beekite has been met with in Flintshire and Yorkshire. (See 

 p. 141.) 



The soil on the Carboniferous Limestone is very often thin, but when present it 

 is usually a ferruginous loam ; and where covered by short, sweet turf, it forms 

 good ground for sheep-farms. 



The rock, however, frequently juts out to the surface, and gives a rugged and 

 picturesque aspect to the scenery. Many of the cliffs, combes, dales, and caverns, 

 of Somersetshire, Derbyshire, and Yorkshire, are formed in this rock. 



The Carboniferous Limestone yields many springs of water, which find their way 

 through joints and fissures. (See sequel.) Analyses by Mr. George Shrubsole of 

 the Carboniferous Limestone near Llangollen, show from 95 to 97 per cent, of 

 carbonate of lime, a small quantity of carbonate of magnesia, together with silica, 

 iron oxide, alumina, and traces of phosphoric acid.* 



1 Sedgwick, T. G. S. (2), iv. 72. 



- Conybeare and Phillips, Outlines of the Geology of England and Wales, 



P- 399- 



^ J. G. Goodchild, Trans. Cumberland Assoc, part vii. p. 116; see also p. loS 

 (lead-ore) ; J. D. Kendall, Trans. N. of Eng. Inst. Mining Eng. xxviii. 107. 



* G. W. Shrubsole, Proc. Chester Soc. Nat. Sc. 1884, pp. 107, no. 



