﻿S. V. Wood, fun. — Amerioah and British Surface- Geology. 541 



The Middle and Upper Grlacial deposits of England appear to me 

 to have been formed during the culmination and recession of the ice 

 only, as in the case of the Karnes of the Ohio water-parting and of 

 the Erie clay. During the accumulation of the Middle Glacial sand 

 and gravel formation, it is not clear how far the ice extended, 

 because, by the action of the inland ice on the western side of the 

 three Eastern counties, after the elevation of the greater part of 

 them into land which accompanied the protrusion of glacier tongues 

 along their valleys, as presently explained, this formation on the 

 western sides of these counties seems to have been destroyed. The 

 origin of these sands and gravels, however, appears to have been due 

 to the washing out by submarine currents of the moraine extruded 

 by the land-ice lying somewhere west of the line marking this 

 destruction in Suffolk and Norfolk which is defined in the sequel ; ' 

 and this was both accompanied and followed by the lifting and 

 dropping through the agency of floating-ice of sheets of the un- 

 stratified moraine itself, because we find such moraine occasionally 

 interstratified in the sands and gravels, as well as very extensively 

 forming a thick bed of Glacial clay over them. 



During the first formation of these sands and gravels, the eastern 

 side of England must have been submerged some 400 feet, because 

 we find them (without any indication of disturbance having occurred 

 in the floor which supports them) ranging from the present sea- 

 level nearly up to that altitude. Near the southern extremity of 

 Glacial clay occurrence in Middlesex, these gravels range up to 

 about 300 feet at Finchley, where they are covered by the morainic 

 clay, and in Essex to 367 feet at Danbury, where they are not so 

 covered. Between these points the morainic clay of the Upper 

 Glacial occupies for the most part lower ground, resting direct on the 

 London clay, as though, after the deposit of the sands and gravels, 

 and their partial overspread by the morainic clay dropped upon them, 

 the ice had advaaced and ploughed out the lower ground, which was 

 afterwards covered by the moraine extruded.^ 



The distribution of the same sands and gravels and of the 

 morainic clay over parts of the counties of Hertford, Bedford, 

 Buckingham, Warwick, Oxford, and Leicester, where in some in- 

 stances they attain elevations somewhat greater than at Danbury, 

 discloses analogous features ; and seems to indicate that similar 

 small extensions and recessions of the ice when at its furthest limit 

 took place in that part of England also. 



As the sands and gravels with marine mollusca reach in North 

 Wales to an elevation considerably exceeding 1300 feet, and in 

 Lancashire, on the west slope of the Pennine ridge, to elevations 



^ A considerable spread of coarse rolled flint gravel in "West Norfolk resembling 

 cannon shot seems to have resulted from similar current action dui-ing the formation 

 of the Upper Glacial chalky clay, upon which ia some instances it seems to rest. 



2 The position of the beds thus referred to is shown in the Geological represen- 

 tation of Ordnance Sheets 1 and 2, which I made, and in the year 1866 placed in the 

 Library of the Geological Society, with a manuscript memoir and sections in illus- 

 tration of it. It is also shown in the map at p. 348 of Vol. III. Geol. Mag. 1866. 



