GEOLOGY. 7 



I. Palaeozoic Age. 



THE SILURIAN SYSTEM 

 Is represented in North Yorkshire only by an isolated patch in 

 the upper Tees Valley, between Falcon Glints and Cronkley 

 Fell. It is probably Lower Silurian (Stockdale Shales), con- 

 sisting of soft shales, formerly worked into slate pencils. The 

 exposure is much obscured by glacial deposits. See Q.J. G.S., 

 xxxiv. (1878), p. 27 ; Yorks. G. & P. Soc. Journal, 1877, p. 

 239 ; also paper by Mr. Gunn at the Plymouth Meeting of the 

 British Association, 1875. 



THE CARBONIFEROUS SYSTEM. 



A line drawn from Pierce Bridge on the Tees, to Tanfield 

 on the Yore, bounds on the east that part of North Yorkshire 

 which is underlaid by the Primary rocks. The Carboniferous 

 system taken as a whole makes up the entirety of the western 

 mass of moorlands. Its oldest or Limestone series of 

 strata may be conveniently treated under two divisions, a lower 

 and an upper set of beds, and it is in the midst of the former 

 that the Teesdale basalt is intruded and has its place. 



(5) The Mountain Limestone (or Scar Limestone) Series. — ■ 

 This lower limestone is more or less exposed to view 

 in the depths of each of the three principal dales of the western 

 moorlands, Teesdale, Swaledale, and Yoredale. A long Ime of 

 strongly marked dislocation passes northward from the Ingle- 

 borough district to the mountains round the source of the South 

 Tyne, an idea of the tremendous character of which may be 

 gathered from the fact that for a length of forty-five miles the 

 strata are displaced to the extent of at least three thousand feet. 

 An observer stationed upon the elevated edge on the east of 

 this line (as for instance, upon the summit of Wild Boar Fell or 

 Swarth Fell, which are situated in Westmorland, just opposite 

 the head of Yoredale) stands upon millstone grit strata, with a 

 thick mass of mountain limestone beneath them, and sees out- 

 stretched 2,000 feet below him the valley of the Eden and the 

 plain of Carlisle, where these same mountain limestone and 



Jan. 1888, 



