XOETHUMBEELAjS'P and DURHAM. 11 



the latter than to the former. Some thick sandstones near the 

 bottom of the group are red, and might, if colour were a test, be 

 mistaken for Old E,ed Sandstone. 



The Mountain Limestone, southward of the Stublick Dike, 

 differs in some important characters from the northern series : 

 the limestones are very much thicker and greater in the aggre- 

 gate. Taking the whole series as developed in the district, and 

 in the bordering counties, we find, from Forster's sections, a 

 total thickness of 2080 feet, of which 470 feet are calcareous in 

 nineteen beds, 820 feet are siliceous, and 790 feet are argilla- 

 ceous. Along the Penine chain, the hills, formed chiefly of such 

 strata, are high, massive, and rounded, with a gradual slope 

 eastward, and a steep inclination to the west, the general dip of 

 the beds being eastward and south-eastward. Here the name is 

 descriptive of the formation; for the thick beds of limestone 

 appear in great cliffs and rise to high elevations, one bed on 

 Mickle Fell reaching a height of 2540 feet above the sea level. 

 The whole, however, is not seen within our district ; eleven only 

 of the limestones have been observed, from the uppermost, the 

 Pell Top, to the Tyne bottom Limestone, which, in the neigh- 

 bourhood of Alston, overlies the Great Whin Sill. We have, 

 therefore, southward of the Stublick Dike, only 900 feet of 

 Mountain Limestone strata, of which 412 feet are argillaceous, 

 314 feet siliceous, 180 feet calcareous, with only about 4 feet of 

 workable coal. The limestones come to the surface chiefly in 

 the dales, while the siliceous and argillaceous strata occupy the 

 higher grounds ,• and hence, excepting in these sheltered valleys, 

 or where the limestone spreads over the surface, there is a wide 

 extent of peaty moors covered with heath ; and this effect is due 

 also to the predominance of sandstones and shales in the upper 

 part of the series, for of these there are 330 feet between the 

 Fell Top Limestone and the Little or Second Limestone, the 

 intervening strata being similar to those of the overlying Mill- 

 stone Grit, with which it has been usual to group them. 



The limestones are the most regular and characteristic strata. 

 The Fell Top limestone, which is from 2 to 6 feet thick, appears 

 in the dales of the Derwent, the Allen, and the Wear, coming 



