506 8. V. WOOD, JUK., OK THE NEWER 



this supply either diminished or ceased, the water arising from the 

 melting during summer found its way between this escarpment- 

 face and the moraine, and having once done this, it, by the ever- 

 increasing quantities pouring from the ice in its dissolution, soon 

 swept out the clay, and washing it into gravel, contributed to that 

 spoil of Lincolnshire, hard white chalk, which, together with the 

 red chalk of the same county, is found in the Cotteswold gravels, 

 presently to be described. Patches of the gravel resulting from, 

 the spoil of the Bain-Steeping trough still remain in it, as at Hag- 

 worthingham (where they cap low hills which were formed out of 

 the Neocomian beds by this denudation), and they are of the cannon- 

 shot kind. 



The narrow spaces in Map No. 1 (PL XXI.) uncovered with the 

 shading representing the Chalky Clay are the river-valleys of the 

 region, the rivers of which are delineated in Map 2. These the ice 

 in shrinking cut out. At the close of the Chalky Clay the sea lay 

 to the west of it, deepening in that direction towards the Atlantic, 

 and it lay in a shallower condition over a part of the German Ocean. 

 Judging from the elevation of the gravel line resting on the Chalky 

 Clay, the sea at this time still flowed up the Lea valley, end, but for 

 the intervention of a space of higher ground near Dunstable, would 

 have formed a strait between the sea in Sheet 1 and that in Sheet 46. 



The water parting between the systems of the Ouse and Thames 

 in Sheet 46, and that between the Nen and Avon in Sheet 53, 

 appear at the close of the Chalky Clay to have just emerged ; but that 

 between the Welland and the Avon (which is part of the Severn 

 system), in the S.E. of Sheet 63, was still beneath the sea-level of that 

 time ; and it was through the Welland valley and over this parting 

 that material from the washing-out of the Bain- Steeping trough 

 evidently was carried into the sea over the Severn system, and 

 imbedded in the Cotteswold gravel in Sheet 44. 



In the case of the valleys in Sheets 70 and 83, though all these, 

 except such as lie in the extreme west of the sheets, now drain 

 to the Wash, yet at the time of the ice-retreat this was, owing 

 to the different inclination of the land, I consider, not the case ; 

 and since, as we have seen, the moraine entered the sea over 

 the upper part of the Trent system by the valley of the Soar 

 in Sheet 63, so did the sea enter the rest of the Trent system 

 from the west as the ice vacated it, and the whole area of 

 that system became occupied by the sea, so that this covered the 

 Jurassic escarpments in the north of Sheet 86, but declined to lower 

 elevations in the direction of the Wash, the line of the gravel e there 

 falling nearly to the level of the existing sea-line. The principal, 

 perhaps the only one of these valleys which has been thus reversed 

 is that flat one of the Witham and its affluents, for it is along the 

 valley of the Langworth, one of the affluents of this river as well as 

 that of the Witham itself below its confluence with the Langworth, 

 that this gravel line descends from the summit of the escarpments in 

 the north of Sheet 83 towards the Wash. 



In this direction, therefore, further part of the water from the ice 



