124 



A. J. JUKE3-BE0WXE ON" THE 



p. 122). This is, in fact, the conclusion at which I arrived in my 

 former paper *. 



Assuming also that the trough of the Witham estuary then lay a 

 little to the west of its present course, and that it was filled up from 

 side to side with the brown Boulder-clays, like that of the Humber 

 estuary, we ma}^ regard the strip of newer Boulder-clay which runs 

 from Billinghay to Nocton and Hanworth as occupying the western 

 half of this old trough, and may suppose that the eastern half of the 

 clay-fiUed trough has been removed by post-glacial erosion. 



This erosion was no doubt partly effected by the river flowing 

 through the Lincoln gorge and impinging upon its left bank ; and 

 it is interesting to note that this tendency to impinge upon the left 

 bank is maintained by Ihe modern river Witham, which hugs the 

 eastern edge of the fen-level all the way from Bardney to Tatter- 

 shall. The erosion of this eastern side was doubtless assisted by 

 the action of the tributary streams flowing off the clay-tracts to the 

 eastward, which would naturally have a greater volume and velocity 

 than those which drained the limestone country to the westward. 

 The Hagnaby beck rising near Bolingbroke has likewise done its 

 share of the work by attacking the promontory of older Boulder- 

 clay on the other side. 



There is, therefore, nothing to militate against the supposition of 

 such a promontory, but, on the contrary, all the facts known to me 

 tell in favour of its existence ; 1 think, therefore, it is a feature 

 which must be introduced into any picture of the Eenland during 

 early post-glacial times. 



§ 3. Points of Contact hetween the two Series of Boulder-clays. 



In East Lincolnshire there are only three localities where the 

 Brown Boulder-clay comes into contact with the White Boulder-clay. 



The first of these is at Maiden well, five miles south of Louth. 

 Here, at a height of about 400 feet above sea-level, occurs an out- 

 Ijing patch of white Chalky Boulder-clay capped with flint-gravel. 

 The same clay also continues down the slope to Maidenwell farm, 

 to the east of which a second patch of gravel occurs, probably over- 

 lying the white clay, but passing eastward into or under a mass of 

 brown clay. No good sections are here to be found. 



The second locality is near "Welton, about three miles west of 

 Louth. Here clay of the Hessle type, overlying a great depth of 

 gravel and exposed in good sections, appears to be banked against a 

 slope of white Chalky Boulder-clay. Near the line of junction a 

 soft, silty, yellowish clay, or calcareous loam, occurs; and the true 

 relations of the two series might easily be exposed by excavating a 

 short trench down the slope at this spot. 



The third locality is near AVold Newton, in sheet 86. The Chalky 

 Boulder-clay enters the sheet S.W. of this village, and ends in three 

 spurs ; the central one of these descends to a lower level than the 

 others, and either passes under or into a brownish clay; but the 



* Loc. cif. p. 409. 



