PLIOCENE PEEIOD IN ENGLAND. 509 



Thames system with that over the Ouse system were on either side 

 of this island ; and in one of these, at Winslow- station brick-field, 

 I found that the Chalky Clay (underlain by c) had over it a bed of 

 gravel full of quartzite pebbles. The Ordnance mark denoting 277 

 feet elevation is on the bridge near this brickfield ; but as Winslow 

 is at the head of the Ouse drainage-system, and the parting between 

 this system and that of the Thames, though open (by way of the Eay, 

 at least) at the time represented by Map 2, had, I think, emerged 

 by the close of the Chalky Clay, the gravel over the clay here, though 

 of the same age as e, does not occupy, as in the cases just men- 

 tioned and those about to be mentioned, the actual issues of the ice 

 of the Chalky Clay to the sea at the close of that formation. 



Mr. Lloyd, in describiug the Drift of the Avon valley, gave the 

 elevation of the quartzite gravel there in Sheet 53 as reaching 

 386 feet*. He does not, however, distinguish to which of the 

 gravels that he groups together as the Older Drift of this part this 

 elevation applies ; but from the notices of its occurrence around 

 Kugby, given by Mr. Wilson in vol. xxvi. of the Journal (p. 192), 

 particularly at Cawston, Clifton, Shawell, and Newton, it would 

 appear that the gravel over the Chalky Clay in the north-east of 

 this sheet ranges nearly or quite to this height (the clay there 

 being also underlain by the gravel c), while at a lower elevation it 

 caps the clay plunging from this position into the valley of the Avon 

 and cutting out c ; for it is described by him, in the report of the 

 Rugby School Natural-History Society for 1873, as there passing 

 imperceptibly downwards into the Chalky Clay, just as I found it in 

 similar position in the Blackwater valley crossed by the line of 

 fig. VII. This is in the Welland and Avon issue, the deepest and 

 broadest apparently of aU the issues of the ice to the sea, except 

 perhaps that of the Trent. 



Proceeding from this part directly towards Moel Tryfaen, we 

 get, at Birmingham, near the centre of the south of Sheet 62, the 

 section of Messrs. Crosskey and Woodward, which I have copied in 

 fig. XYII. Here the gravel e appears to reach the elevation of 520 

 feet. This seems to be in the (reversed) Trent issue. 



In all this, both in the direction southwards from Sheet 48 

 and westwards from Sheet 1, we find the increment of submer- 

 gence so far agreeing with that traced at the end of Stage 11, 

 that, from the part where this gravel rises above Ordnance datum 

 in the north of Sheet 48 to the place of Section XVII. being 140 

 miles and the rise 520 feet, it gives a westerly increment of 3*7 as 

 against the 4-5 feet per mile in Stage II., while from the same point 

 to Ongar cutting, in Sheet 1, the distance being 70 miles and the 



^ Quart. Journ. Geol. Soc. toI. xxvi. p. 216. The gravel reaching this elevation 

 is that distinguished by Mr. Lloyd with the letter A. Mr. Lloyd's bed B, where it 

 occurs in the Lias districts, is the Chalky Clay, and elsewhere it may be ita 

 marine equivalent, as may also be his 0. His D is the Middle Glacial (c). All 

 these he puts together as the Older Drift ; and his other, or Newer Drift, indi- 

 cated by succeeding letters, is that of stages subsequent to this portion of my 

 memoir. 



