TYNEDALE ESCARPMENTS. 289 



them, the form of both being moulded more or less in confor- 

 mity with general characteristics of structure. 



The ridges and furrows between the Tynes coincide with the 

 peculiarities of the framework of rock in a very marked degree. 

 That portion of the Lower Carboniferous series of the IS'orth 

 of England to which these strata belong, consists of beds of 

 sandstone, limestone, and shale, rocks greatly differing from one 

 another in coherency and durability. The sandstones, thickest 

 and most massive, are here always to be found in the loftior 

 crags and bolder swells ; the limestones, being thinner, are com- 

 monly subordinate elements in the projecting features ; and the 

 more yielding shales are to be found in the troughs and hollows 

 that throw the ridges into relief. ''It seems unnecessary," as 

 Phillips long ago remarked of similar features in Yorkshire, " to 

 offer any other explanation of the prominent and retiring parts 

 of the profile than that afforded by a consideration of the relative 

 resistances offered by the different rocks."** All those notions 

 of vertically upheaving force, which the occasionally rugged and 

 broken appearance of crags seem at first sight to encourage, are 

 perforce abandoned on better examination. The uniform accli- 

 vities, where the heel may often strike upon the plane of the 

 rock, have simply been uncovered by the removal of less stable 

 beds, perhaps of shale, whose outcrop is now hid under the shel- 

 tering front of the crag overlooking them. They are the dip- 

 slopes, — bared planes of separation between beds. The short steep 

 faces in which they terminate arc the scarps, the abrupt ending 

 of strata whose upward continuation has been by some means 

 cut away and removed. A feature thus composed of di2)-slope 

 and scarp is called an escarpment. 



Locality treated of. — The area with which this paper deals is re- 

 stricted to the space betwixt the North and South Tynes, and from 

 the former over towards the Wansbcck. The general E.N.E. line 

 of the Roman "Wall from near Grcenhcad, South Tyue, to where 

 it dips, beyond Carrowbrongh, into North Tyne, will sufficiently 

 indicate the trend of the outcrops there. Through the greater 



* I'liilliiis Geology of Vorksliliv, I'ml 11., p. 1(»!>. 



