§ 6. SLATE ROCKS OF SHROPSHIRE AND CUMBERLAND. 801 



form the Longmynd and contiguous ranges of hills, com- 

 prising Ratlinghope, Linley, Pontesford, &c, and vary in 

 height from 1,000 to 1,600 feet. The strata consist of 

 hard sandstone, grit, schist, and imperfectly consolidated 

 slates, which are piled up in mural masses, the beds being 

 either vertical, or in very highly inclined positions.* jSo 

 traces of organic remains have been observed, nor indeed 

 could reasonably be expected, from the altered condition 

 of the strata, produced by the intrusive trap rocks. But 

 cupriferous veins, bitumen, and other minerals, occur in the 

 slates and sandstones, throughout the tract included between 

 the Longmynd and the Stiper stones, especially where 

 there are contiguous masses of trap.f Sir R. I. Murchison 

 concludes his interesting account of the Longmynd hills, 

 with the remark, that the stratified rocks are lithologically 

 similar to, and probably of the same geological age as the 

 so-called greywacke of theLammermuir and other hills in the 

 south of Scotland. They also correspond with much of the 

 greywacke of the north of Ireland, and with that of large 

 tracts in Somerset and Devon. 



The Lake district, so well known to the tourist, may be 

 described as a circular cluster of mountains, the central 

 portion consisting of serrated peaks of schistose rocks, 

 thrown into their present position by granite and other igneous 

 masses which constitute the true geological centres of the 

 mountain groups. The outskirts of this region are chiefly 

 formed by carboniferous deposits ; a zone of mountain lime- 

 stone appears on the east, north, and south, and the 

 western side is bounded by the Irish Sea. 



Within the calcareous zone, are several extensive masses 

 of granite, syenite, and porphyry, but the greater part of 

 the region is occupied by stratified deposits of a slaty 



* Silurian System, chap. xxi. See the beautiful geological views of 

 these mountain ranges, 

 f Silurian System, p. 261. 



