TYNEDALE ESCARPMENTS. 



285 



XVI. — Tynedale Escarpments; their Pre-glacial, Glacial, and 

 Post-glacial Features. By Hugh Millek, F.G.S., Assoc. E.S.M., 

 H.M. Greological Survey. 



TABLE or CONTENTS. 



General Description. 

 Relation of Features to Rock Struc- 

 ture. 

 Locality treated of. 

 Denudants. 

 Theories of Escarpment-formation. 



1 Old Diluvial Theory. 



2 Theory of Protrusion. 



3 Marine Theory. 



4 Theory of Glacial Excavation. 



5 Theory of Formation of Out- 



crop-terraces by Rivers. 



6 Hutton's Theory of Origin by 



Atmospheric Waste. 

 Adequacy of this agent. 

 Its forces : 



1 Frost. 



2 Rain and Wind. 

 Illustrations in Tynedale of Atmos- 

 pheric Action. 



Suitableness of Theory. 

 Development of Escarpments, — 



1 By Stream and Atmospheric 



disintegration together. 



2 By Atmospheric disintegra- 



tion alone. 



Tynedale Valleys,— 



1 Longitudinal. 



2 Transverse. 



The "Rig -and -Fur" of Escarp- 

 ments. 



1 Relations of Waterflow to 



Ridges. 



2 Sandstone Escarpments. 



3 Limestone Escarpments. 



4 Shale. 



5 The Whinsill. 

 Watershed Escarpments. 

 Escarpments near theValley-Terraces 

 Age of the Valley and Escarpment- 

 system. 



Effects of the Glacial Period upon 



these Escarpments. 

 Post Glacial Atmospheric Action. 



1 Waterfalls and Denes. 



2 Crag-Talus. 



3 Swallow holes. 



4 Aerial Pot holes. 



6 A theory of the incised Cups 



and Channels. 

 G "Snail Borings" in Lime- 

 stone. 

 Conclusion. 



General Description. — The tourist, in tracing the course of the 

 llouian Wall westward, finds himself crossing, obliquely, the fork 

 between the North and South branches of the Tyne. A little west 

 of Sewingshields farm house he has reached the summit of a lofty 

 crag, a main headland of the basaltic ridge there selected by the 

 Ilomans for the line of their great military barrier. The ' ' gods of 

 the mountains," lie may say, had assuredly deserved the worship 



