﻿1850.] 



TRIMMER ON THE ERRATICS OF NORFOLK. 



25 



the upper and lower erratics have both been very generally removed, 

 and the secondary strata are covered with thin accumulations of their 

 reconstructed materials, brought down to lower levels. 



19. The variations of soil and subsoil are caused by this varying 

 amount of denudation, combined with the varying thickness and 

 composition of the Warp, the former being the result of levels and 

 contours, the latter of the composition of the neighbouring and sub- 

 jacent beds exposed to denuding action. For details I refer to my 

 Map of Norfolk *, and to the paper on the Distribution of Soils, in 

 the Journal of the Royal Agricultural Society of England, vol. vii. 

 part ii. 1847. 



20. Although the boulder clay extends to the northern confines of 

 the valley of the Thames, I have seen no trace of it south of that 

 river, nor have I met with any boulder, except one of trap which 

 was in the upper part of the elephant bed at Brighton, a deposit 

 which much resembles the upper erratics of Norfolk. The superficial 

 deposits of Hampshire, Sussex, and Dorsetshire consist of flint gravel, 

 unabraded or very slightly abraded, of little depth, rarely exceeding 

 30 feet, and often much less, very generally spread over the surface 

 at all heights, from about 600 feet on the summit of some of the 

 chalk hills, down to the sea level. The highest beds contain the 

 largest flints and the least abraded. They appear to diminish in size 

 with the different stages of descent ; and it is a remarkable fact, that 

 they are in general little more waterworn at the lowest than at the 

 highest levels. I consider this gravel to be a modification of the 

 upper erratics of Norfolk, the region south of the Thames having 

 been, perhaps, the last submerged, and having continued the shortest 

 time under water. I have found neither shells nor mammalian bones 

 in this gravel throughout the Hampshire eocene district, west of the 

 Southampton Water, nor could I hear of any having been found. 

 The local papers have, however, very recently announced the disco- 

 very of tusks of the elephant and horns of the stag in beds connected 

 with this gravel, in the grounds of Lord Eldon at Encombe. 



21. With regard to mammalian remains, I believe that we have 

 two elephantine groups, one preceding the submergence of the erratic 

 period, and the other inhabiting the country at the close of the period 

 of elevation. To the former are to be referred the mammalian crag 

 and the remains of the bone-caverns in general ; — to the latter the 

 freshwater beds of the valley of the Thames, of the Avon in Wor- 

 cestershire, of Gaytonthorpe, and of Bielbecks in Yorkshire, together 

 with the marine deposit of the valley of the Nar. 



22. In the valley of the Thames there are two deposits of brick- 

 earth and gravel ; one containing mammalian bones, with land and 

 freshwater shells identical with species now inhabiting the neighbour- 

 hood ; the other destitute of them. The former are only found in 

 the vicinity of the Thames and its tributaries, and at certain heights 

 above them ; the greatest distance at present known being about a 

 quarter of a mile, and the greatest height above the present stream 

 about 40 feet. These fluviatile deposits of gravel, sand, and loam are 



* The map does not accompany this paper. 



