﻿72 DR. WOOLACOTT ON THE SUPERFICIAL DEPOSITS, ETC. [Feb. I905, 



exposure of maximum elevation at Cleadon and Fulwell. A gradual 

 decrease in its height can be traced along the coast from its first 

 occurrence south of Seaham, at an elevation of 80 feet, to Castle- 

 Eden Dene, where it lies about 60 feet above sea-level. A raised 

 beach, which was possibly formed at the same time, occurs at 

 Saltburn, some 18 miles farther south on the other side of the Tees, 

 its height there being 30 feet. 



If the height of the raised beach of County Durham is original 

 throughout its course (and it seems to be so), we have evidence of 

 differential north-and- south movements in the uplift that pro- 

 duced it. The gradient is from 3 to 6 feet per mile. This aspect 

 of the deposit has evidently a most important bearing on the con- 

 clusion enunciated by Sir Archibald Geikie in his Anniversary 

 Address to the Geological Society, Quart. Journ. Geol. Soc. vol. lx 

 (1904) p. civ, namely : — 



' That the changes of level, of which our islands furnish such signal illustra- 

 tions, have been primarily due, not to any oscillations of the surface of the 

 ocean, but to movements of the terrestrial crust connected with the slow cooling 

 and contraction of our globe." 



The raised beaches cannot be traced very far inland, and this may 

 imply that the uprise which produced them was greater near the 

 coast ; in any case, a considerable extent of country must have been 

 covered during the time in which they were being formed; and the 

 action of the sea on the deposits of Glacial origin in levelling their 

 surface, and forming derived beds of gravel, sand, and sandy clay 

 from them, has been of great moment. 



The remains of submerged forests, which are exposed at 

 irregular intervals, also occur, resting upon the other deposits at 

 Howick, Whitburn, and West Hartlepool. I have had the oppor- 

 tunity of examining the former two exposures, but more especially 

 that at Whitburn, which is unmistakably the remains of vegetation 

 that grew in situ. There seems thus to be undoubted evidence of 

 two distinct movements since the Glacial Period — the 

 first an elevation which produced the raised beach, and the second 

 a depression causing the submerged forests. 



III. The Distribution, Thickness, etc. of the Glacial Deposits. 



The superficial deposits cover the larger portion of the great 

 Northern Coalfield, comparatively little rock being exposed except in 

 the higher portions of the district. In the South-East of Northumber- 

 land the thicker masses of sandstone stand out above the mantle 

 of clay; while in Eastern Durham the Magnesian -Limestone escarp- 

 ment forms a distinct feature, and its surface is not (except in the 

 valleys) covered by any considerable thickness of superficial deposits 

 Some of the higher western ground of the Northern Counties was 

 never under ice, but stood out as nunatakkr during the Glacial 

 Period ; and since the ice-flow mainly came down the valleys, the 

 higher parts of Mid-Durham have no Boulder-Clay upon them. 

 The amount of rock exposed is shown on the Drift-maps of the 



