﻿1851.] 



AUSTEN ON THE PLEISTOCENE PERIOD. 



127 



Fig. 5. 



—Section near 

 ham, Torbay. 



Brix- 



ture is very constant and distinct, and marks a permanent level of 

 some considerable duration. 



The characteristics of these lower sea-heds are, that they have 

 become consolidated into hard compact masses of sandstone and con- 

 glomerate, that they contain materials derived from the greensand and 

 chalk formations, and that, generally speaking, included marine tes- 

 tacea are scarce. Most of the " raised beaches " indicated by Sir H. 

 De la Beche on the Ordnance maps of Devon and Cornwall belong to 

 this period of sea-level, and of which those described are the most 

 striking illustrations ; it must not however be supposed that they 

 occur only at the wide intervals at which they are there noticed ; 

 having visited them all in the course of the last summer, I can cer- 

 tify to the accuracy of the representations which Sir H. De la Beche 

 has given. 



I refer to this period, the marine beds on the east of Torbay (Geol. 



Trans, vol. vi. p. 441). On the oppo- 

 site side of the bay, about Brixham, 

 we find the like level maintained by 

 the beds which cap the limestone 

 cliffs (fig. 5). 



On the west of Dartmouth we have 

 as instructive a section as near Fal- 

 mouth. The lower marine beds of 

 Plymouth have been repeatedly no- 

 ticed ; and the Sections, No. 1-4, PI. 

 VI., will sufficiently explain the rela- 

 tions of the several successive con- 

 ditions in St. Austle Bay. 



The lower beds of sand and shingle 

 from Brighton to Rortingdean, with 

 fragments of crystalline rocks, I would 

 refer to this period and level, so that 

 we are enabled to comprise the whole 

 length of the English Channel as 

 having partaken of this movement. 



We have therefore evidence of a 

 third line of sea-level, distinct from the 

 former ones, which taken from east to 

 west does not appear to be so constant 

 in its relations to that of the sea at 

 present, and which was of sufficient 

 duration to admit of the formation of 

 sea-cliffs. 



Before proceeding to the inferences 

 and comparisons which the foregoing 

 facts suggest, I will briefly recapitu- 



20 feet. 



with 



a. Upper band of marine shingle 



superficial vi getable soil. 



b. Subaerial beds. 



c. Marine shingle. 



d. Limestone rock. 



late the series of changes indicated 



1st. A narrow sea-zone, former sea-cliffs, and the presence of marine 

 and estuary beds where is now fresh-water, showing a last rise of 

 the land of from 8 to 1 feet for the whole of the East Channel area. 



