680 THE WONDERS OF GEOLOGY. Lect. VII. 



and the sandstone and shales of the Coal above. In Cum- 

 berland and Westmoreland, &c. it appears as an elevated 

 belt, which partly surrounds the Cumbrian slate mountains, 

 and forms, on the west, a ridge nearly three thousand feet 

 in height. 



In Northumberland the mountain limestone with its as- 

 sociated millstone-grit, occupies large areas, and constitutes 

 ranges of hills of considerable elevation ; the geographical 

 features strongly contrasting with those of the adjacent 

 country on the south, which consists of the coal-bearing 

 strata, spread out in a plain of great extent. 



In Derbyshire the grand physical features of the country 

 are produced by the mountain limestone, which rises into 

 crags or peaks, and hills, presenting bold precipitous 

 escarpments, and produces the wildest and most picturesque 

 scenery. Professor Phillips estimates the thickness of the 

 lower division of limestones with shale partings (provin- 

 cially termed scar-limestones\ in Derbyshire, at 750 feet ; 

 the alternations of shale, sandstone, limestone, and ironstone, 

 which surmount the former, at 500 feet ; and the cappings 

 of millstone -grit which form the summits of the hills, at 

 360 feet. 



The carboniferous limestone, though some of the 

 beds are destitute of fossils, is for the most part largely 

 made up of corals, shells, crinoidea, &c. ; and which often 

 form three-fourths of the mass. We reserve a more par- 

 ticular notice of these organic remains for a subsequent part 

 of this Lecture. The Derbyshire encrinital marbles (ante, 

 p. 650), and the coralline marbles of St. Vincent's rocks, 

 near Clifton, are well-known examples of the finer compact 

 varieties of these calcareous deposits. 



The chert, where interpolated among the crinoideal 

 remains, contains beautiful casts and impressions of the 

 stems and ossicula, and also of the associated shells, in con- 

 sequence of the siliceous matter which flowed into, and 



