204 NEOZOIC TIME. [CHAP. XI. 



bed only of the London Clay remains, and this is directly 

 covered by sands and pipeclays of the Bagshot type. The 

 only conclusion Mr. Whitaker draws from this is that the 

 London Clay has thinned out ; but it seems to me that the 

 persistence of the basement bed of the London Clay below 

 the Bagshot Beds means something more, and proves that 

 sands replace the brown clays in other words, that the 

 Lower Bagshot Beds belong to the London Clay group, and 

 not to that of the Bracklesham Beds. 



Fig. 5, which is reproduced from Mr. Whitaker' s dia- 

 gram, shows the rapid thinning out of the London Clay 

 west of Reading, and the superposition of the " Lower 

 Bagshot " on the Beading Beds. As the latter are also 

 very thin here, he thinks that the Lower Bagshot Beds 

 eventually overlapped them to the westward, so as to rest 

 directly on the Chalk a conclusion which is confirmed by 

 the abundance of " greywethers " on the Chalk Downs in 

 that direction, and by the presence of large rounded flints 

 as well as small pebbles in the " basement bed," which is 

 common to the sands and the London Clay. 



With regard to the southern extension of the London 

 Clay group, there is every reason to suppose that it spread 

 completely through Hampshire into the southern basin. 

 At Southampton and at Whitecliff Bay the London Clay is 

 just over 300 feet, and the " Lower Bagshot " is about 50 

 or 60 feet ; but at Alum Bay the former is only 200, and 

 the latter increases to 248. Noting this replacement, and 

 the fact that the plant remains of the Lower Bagshot Beds 

 are more nearly related to those of the London Clay than 

 to the flora of the overlying Bournemouth Beds, Mr. J. S. 

 Gardner suggested in 1882 that the Lower Bagshots 

 should be separated from the latter, and grouped with the 

 London Clay. 1 In Dorset the London Clay is very thin, 



1 " Geol. Mag.," 1882, p. 470. Professor Prestwich has adopted a 

 similar line of argument in his recent communication to the Geological 



