﻿1851.] 



AUSTEN ON THE PLEISTOCENE PERIOD. 



129 



land. In making this statement it is necessary to add, that I of 

 course refer the marine beds of the Cotentin, at Carantan, to the 

 period of the lower marine beds of our own western coasts, and am 

 quite prepared to find in them the same amount of specific peculi- 

 arities which the testaceous fauna of that side of the Channel now 

 presents, as compared with that even of our western coasts. 



As yet we possess no sure guide towards determining the condition 

 of the surface area of the red and coralline crag subsequently to its 

 completion, and prior to that indicated by the mammaliferous crag 

 and its equivalents, for which latter period the relative position of 

 land and water is sufficiently clear. The outline of the surface of 

 the Eastern counties, as to lines of drainage, had been imparted prior 

 to the period of the Norwich crag, inasmuch as the fluvio-marine 

 portions of this formation (which are simply the indications of the 

 places where rivers discharged into the sea) occur at the lines of the 

 present drainage. 



I propose to consider the older sea-beds (Sections, PI. VI. 1, 1, 1, 1.) 

 of the western portions of the English Channel area as of the same 

 age as the Norwich or mammaliferous crag, a view which will be 

 found to be in perfect accordance with the conditions indicated by 

 their marine faunas, as also with the relative places which both sets 

 of accumulations occupy in a well-marked series of oscillations. The 

 lowest sea-beds of the Bristol Channel valley will represent this period 

 of level in that quarter, when the sea may have reached inland to a 

 considerable distance, for the beds at Kempsey are most probably of 

 this age. 



In this we have an outline of land and water very similar to that 

 which is presented at present, as regards the relation of the South 

 and East of England to the continent. 



Next in ascending chronological order we have the accumulations 

 described as the necessary results of sub-aerial conditions ; and from 

 the vast thickness which these masses present, along lines to which 

 they have been cut back by a former sea-level, it is clear that they 

 must at one time have had a very considerable extension seawards, or 

 that originally they were carried on beneath the water-level by which 

 they have thus been cut back. This implies a former elevation of 

 the land, with relation to the highest upward range of the oldest 

 sea-level {e, Sect. 4. PI. VI.). 



The most interesting inquiry which these sub-aerial masses suggest 

 is that of the absolute amount of the elevation which this region then 

 acquired : with respect to this point many general and local consi- 

 derations afford us data for very reasonable suppositions, some of 

 which, however, I do not propose to refer to at present. In nearly 

 all the sections to which I have called attention we can distinguish 

 the results of the meteoric agency of the present period. The com- 

 position of these beds shows that the transporting power is exceedingly 

 limited. In the older sub-aerial accumulations, on the contrary, we have 

 evidences, as already shown, of power sufficient to detach great blocks 

 from the jointed masses of older rocks, to break up the fissile slates, 

 and to accumulate the sharp and angular detritus in lower positions. 



