1853.] TRIMMER ON THE GRAVELS OF KENT, 293 



I cannot, with Mr. Austen*, place the Brighton old heach on the 

 parallel of the Crag ; for this reason, that it contains pebbles and 

 boulders of granite, and other crystalline rocks of northern origin, 

 which are not found in the Crag, and which do not make their ap- 

 pearance in any deposit till the commencement of the Boulder clay or 

 Lower erratics. 



The granitic fragments of Brighton were probably transported 

 during the latter portion of the Boulder-clay period. 



In illustration of these views, I refer to the accompanying maps 

 (in Plate XIII.) of the changes which would take place in the phy- 

 sical geography of this north-western extremity of Europe, at dif- 

 ferent stages of the process of depression and re-elevation, during the 

 pleistocene epoch. 



No. I. represents the first elephantine or stationary period, — the 

 period of the Forest of Cromer and Happisburgh, which is rooted in 

 the mammalian crag, — when England and Scotland were united to 

 the Continent. 



I have represented Ireland and England as united also ; but from 

 the general dearth of elephantine remains in Ireland, this may be 

 considered as doubtful. 



No. II. represents the close of the period of boulder-clay, when the 

 whole of Great Britain and Ireland was submerged, except the 

 summits of mountains exceeding 1.500 feet in height, and except in 

 England the counties south of the Thames, or rather of the present 

 site of the Thames. 



At this period we may suppose England still united to the Conti- 

 nent in the direction of Normandy and Cornwall, and a gulf to have 

 occupied part of the north of France, and the eastern part of the 

 present site of the English Channel ; and into this gulf the granitic 

 fragments may have been transported, which were afterwards re- 

 arranged in the ancient beach of Brighton. 



No. III. represents the latter portion of the period of Upper Erratics. 

 The southern counties were now submerged, and the formation of 

 the anticlinal of the Weald in progress. 



We may suppose Scotland, Ireland, and the north of England to 

 have been re-elevated at this time in the direction of Scandinavia and 

 the north of Germany, and thus re-united to the Continent. 



This was the period of the immigration of the Reindeer and Mega- 

 ceros ; and the tracts represented as reconverted into land are those 

 in which the remains of the latter are most abundant. 



At this period the deposits of the Clyde and Forth would be laid 

 dry ; and this early elevation will explain the more arctic character 

 of their shells as compared with those of the valley of the Nar, — a dif- 

 ference which has been noticed by palaeontologists as greater than 

 can be ascribed to difference of latitude alone. 



In No. IV. England is represented as completely re-elevated and 

 again united to the Continent on the south-east, but separated on the 

 north-east. The Thames was then a river of greater volume, and ex- 

 tending further eastward, than the present stream ; for its ancient 

 * Quart. Journ. Geol. Soc. vol. vii. p. 136, tabular view. 



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