Vol. 62.] THE CLAY-WITH-FLINTS. 145 



the domes and anticlines. In this way, therefore, the distribution 

 of the clay-tracts should clearly indicate the source from which 

 the Clay-with-Flints has been chiefly derived. 



There is, however, one large area in which the relations of the 

 Clay-with-Flints are complicated by several special circumstances, 

 and the consideration of which I shall leave to others who have 

 better acquaintance with it. This area is that of Kent and Eastern 

 Surrey, where the Thanet Beds are the lowest member of the 

 Eocene Series, and where also the Oldhaven Beds seem to have 

 passed over them southwards onto the Chalk. This area also was 

 submerged in Lower Pliocene times, and there seems to be some 

 uncertainty about the relation of the Lenham Beds to the Clay- 

 with-Flints. Mr. Beid states that, on Lenham Down, 1 patches of 

 Lenham Beds underlie extensive sheets of Clay-with-Flints ; on the 

 other hand, Prestwich had long ago figured and described a layer of 

 brown and black clay with flints, as underlying the Lenham Sands 

 and resting on the Chalk, not far from the same place. Its position 

 according to Prestwich seems natural ; but its position according 

 to Mr. Beid seems difficult to understand. 



I shall, therefore, confine myself in the following pages to a 

 consideration of those areas where the Beading Beds form the 

 lowest member of the Eocene Series, and where no marine Pliocene 

 Beds occur as a disturbing factor. 



Let us turn first to the country which lies west and north-west 

 of the London Tertiary Basin. Anyone who will study the published 

 Drift- editions of the 1-inch maps of the Geological Survey, such 

 as Sheets 267, 268, etc., will see that there appears to be a very 

 close connection between the Beading Beds and the areas mapped 

 as Clay-with-Flints. It must, of course, be remembered that the 

 latter include the overlying loam and brickearth where such 

 materials occur ; but these are admitted to be inseparable from 

 Clay-with-Flints. 



The noticeable point is, that these loams, with their basal layer 

 or fringe of Clay-with-Flints, behave as if they were merely dis- 

 integrated portions and outliers of the Beading Beds. 



In the far west of the London Basin, that is, in the western parts 

 of Wiltshire and Berkshire, the tracts of Clay-with-Flints occur on 

 ridges and plateaux which are clearly portions of an inclined plane 

 rising towards the outer escarpment of the Upper Chalk. The 

 material seldom descends far down the slopes of these ridges, except 

 in places where there is reason to believe that landslips have 

 occurred ; as a rule, the average level of the boundary-lines is little 

 below that at which outliers of Eocene occur or might occur. In 

 other words, the surface on which the tracts of Clay- 

 with-Flints lie is practically a prolongation of the 

 basal Eocene plane. Moreover, the tracts do not become larger 

 and thicker in the direction of the Chalk-escarpment, as should be 



1 ' The Pliocene Deposits of Britain ' Mem. Geol. Surv. 1890, p. 45. 



