152 CARBONIFEROUS. 



which delight our eyes amidst the calcareous dales of Derbyshire 

 and Yorkshire, wide, heathy, and boggy moorlands overspread the 

 surface of sandstones and shales, and we seem to wander in a 

 region of barren Coal-measures, rather than on a tract of the 

 thickest Carboniferous Limestones.^ 



On the Northumberland coast the Bernician rocks are well ex- 

 posed near Eeadnell and North Sunderland point. The uppermost 

 beds, no doubt, are equivalent to the Yoredale rocks, but, as Prof. 

 Lebour has pointed out, there is nothing in this part of England to 

 enable one to draw a line separating the Yoredale from the rest of 

 the Carboniferous Limestone series — hence the utility of the term 

 Bernician. 



The beds include a series of limestones, shales, grits, and sand- 

 stones, of very variable character. The upper beds consist chiefly 

 of sandstones and shales ; and the lower beds of limestones, thin 

 coals, and fire-clays. The thickest limestone seldom exceeds 30 

 feet, and the total thickness of the series is from 500 to 8000 feet. 



In the Alston Moor district the thickness of the series, according 

 to measurements by Westgarth Forster, is about 2500 feet; and 

 near Alnwick it is about the same ; but, as Prof. Lebour points out, 

 between these two regions, in the tract lying between the Tyne 

 and the Coquet, the maximum thickness is at least 8000 feet.^ 



The Coal-seams occur with and without underclays, and are in 

 every way comparable, except as to commercial importance, with 

 those of the Coal-measures. The Bernician coal-seams, however, 

 exhibit a much greater tendency to split up, thicken and thin out 

 in short distances, than do the seams in the Coal-measures. The 

 coal-seams are known by different terms, and include the Redesdale, 

 Plashetts, Shilbottle, and Beadnell Coals. The Beadnell Coal is 

 about three feet in thickness. 



Among the limestones, the Great Limestone is most persistent ; 

 it is extensively quarried, and frequently forms a distinct feature in 

 the country. It averages from twenty-five to thirty feet in thick- 

 ness. Other limestones are the Fell Top Limestone, Ebb's Nook 

 Limestone, the Eight-yard or Four-fathom Limestone, the Six-yard 

 Limestone forming the Blythe Rocks at Benthall, the Scremerston 

 Limestone south of Berwick, the Lamberton or Dun Lime- 

 stone north of Berwick, and the Beadnell or North Sunderland 

 Limestone. (See p. 164.) The last-named limestone is capped 

 by layers largely made up of Producius loyigispinus and Spirifera 

 irigotialis? 



In the Four-fathom Limestone a Foraminifer, named Saccamina 

 Carteri hy Dr. H. B. Brady, was discovered by Sir W. C. Trevelyan 

 at the Elf Hills quarry, near Scot's Gap. This minute fossil, which 

 gives the rock an oolitic appearance, has since been found at 

 other horizons. 



1 Manual of Geology, 1855, p. 167. 

 ^ Geology of Northumberland, p. 33. 



^ G. A. Lebour, Trans. N. of England Inst. Mining Engineers, xxxiii. 69. See 

 also vol. XXV. 



