﻿S. V. Wood,jun. — American and British Surface- Geology. 545 



Chalk debris, immediately underlies the Hessle clay wrapper in the 

 two high cliffs already mentioned ; while that of Scotland, so far as 

 it belongs to the same period of glaciation, is latest of all, and may 

 have accumulated while the South of England was the theatre of the 

 disturbances presently referred to. Moreover, when the latest part 

 of the Upper Glacial formation, the Moel Tryfaen and Lancashire 

 high-level sands, was accumulated, it is clear that, except to the 

 extent possibly of some glaciers still remaining in the vallej'S of 

 the islands to which the mountain district of the North of England 

 was at that time reduced by submergence, there could have been 

 no ice enveloping the Southern extremity of that district, though 

 Snowdon and other higher mountains of North Wales may possibly 

 still have been snow-clad. The North of Scotland, too, from its 

 latitude, may also at this time have not been freed from its ice, so 

 that the morainic clay of that part of Britain, except so far as it ma}'^ 

 be of later (i.e. Hessle) age, may even be synchronous with these 

 high-level sands of Lancashire and Wales, for the shells which have 

 occurred at Elie and elsewhere on its eastern coast, though more 

 Arctic in character, possess the same modern facies as do those of 

 Moel Tryfaen, and of Macclesfield, as well as those from gravels of 

 Hessle age. 



In the East of England the sea, during that earlier part of the Glacial 

 period to which the Contorted Drift belongs, was evidently deep enough 

 to buoy up the glacier which occupied some part of the Chalk country, 

 and break off portions into bergs ; and these, from the dimensions 

 of the masses of reconstructed Chalk which by their grounding 

 they introduced into the mud of that drift, must have been of con- 

 siderable size. What that depth of water was it is difficult to 

 estimate ; but when we consider that the mass of Lower Glacial 

 deposits in which these bergs grounded was itself in that part near 

 200 feet thick, it is clear that at this stage in the Glacial period 

 the Eastern counties must have undergone, since the time of the 

 newest Crag beds, great depression and submergence. As already 

 mentioned, however, this sea-bed had, prior to the Middle Glacial 

 sands, undergone denudation, the effect of which was to excavate 

 along the lines of our present valleys wide and deep troughs, in 

 which to a great extent these sands accumulated, and were over- 

 spread in their turn by a deposit of the morainic chalky clay. 

 After this, as I shall presently endeavour to show, so much of this 

 area as forms the eastern part of the counties of Norfolk and 

 Suffolk was early in the formation of the chalky portion of the 

 Upper Glacial converted into a belt of land, which divided the 

 inland-ice from the sea, and through the valleys of which that ice 

 in the form of glacier tongues escaped. By the well at Yarmouth, 

 described by Mr. Prestwich in the 16th vol. of the Journ. of the 

 Geol. Soc. of London (p. 450), we learn that the depth to which 

 one of these valleys, the Yare, has been excavated and filled up 

 since with silt and mud is 170 feet below Yarmouth, or about 155 

 below Ordnance datum. This is not only far below the surface of 

 the adjoining sea-bottom, but is below the surface of that sea -bottom 



DECADE II. VOL. IV.— NO. XII. 35 



