266 NEOZOIC TIME. [CHAP. XIII. 



marine drifts which spread over so large a part of Che- 

 shire and Lancashire has not yet been ascertained, but 

 high-level marine beds have been found at a height of 

 1,200 feet near Macclesfield. 



In the midland and eastern counties, also, two distinct 

 groups of Glacial deposits are found. The older group is 

 well developed in East Anglia, and it is generally supposed 

 that the oldest Pleistocene beds in England are those which 

 succeed the Pliocene series near Croraer. These consist of 

 laminated clays, sands, and boulder-clays, overlain by a 

 mass of contorted loam, sand, and gravel, the whole at- 

 taining a thickness of nearly 200 feet, and yielding shells 

 of marine species ; these beds are believed to pass inland 

 beneath the grey or chalky Boulder-clay which has such a 

 wide extension to the south, west, and north-west. Some 

 doubts indeed have recently been thrown on this presumed 

 succession, 1 but the difficulties experienced in the mapping 

 of north-east Norfolk can hardly be allowed to invalidate 

 the succession which holds good over such large areas to 

 the southward, where the deposits are less disturbed and 

 contorted ; it may, in fact, be stated that throughout Essex, 

 Herts, Suffolk, and south Norfolk, except where the height 

 of the ground rises above 300 feet, there is a lower set of 

 loams, clays, sands, and gravels, which sometimes contain 

 fragments of marine shells, and are overlain by a chalky 

 Boulder-clay which is quite destitute of such remains. 

 Beyond these counties there is no such definite succession, 

 but the upper Boulder- clay spreads over large areas to the 

 westward and is associated with irregular masses of sand 

 and gravel. 



There are certain facts connected with the surface eleva- 

 tion of the eastern parts of Norfolk and Suffolk, and with 

 the distribution of the chalky Boulder-clay, which are 



1 Reid, "Geology of the Country around Cromer," p. 115, and 

 Woodward, " Geology of the Country around Fakenham," &c., p. 19. 



