224 NEOZOIC TIME. [CHAP. XI. 



emptied themselves into the sea and contributed to its 

 formation. Is not the London Clay just such a lenticular 

 mass of mud as would be formed in the central and deeper 

 part of a rather shallow sea, into which many rivers poured 

 their load of sediment? Mr. Gr. F. Harris, who has studied 

 the Belgian strata, informs me that there is no evidence of 

 fluviatile deposits on a large scale in Belgium, or of the 

 influx of any large river from the east, but that the Belgian 

 geologists attribute the fluviatile and estuarine portions of 

 their Lower Eocene deposits to the influence of small 

 streams from the eastward. In the same way the river 

 by whose current the Sheppey fruits were carried may 

 have come from the land which lay over France to the 

 south, 1 but there is no reason to suppose that its volume 

 was greater than that of the Thames. We must remember 

 also that these Sheppey clays may be contemporaneous 

 rather with the Lower Bagshot Beds than with the London 

 Clay of the west. They may have been formed at a time 

 when much of the shallow sea-bed had again been con- 

 verted into a region of lakes, lagoons, and estuaries, partly 

 by the process of silting up, and partly perhaps by an 

 actual uplift of the northern part of the English area of 

 sedimentation. 



It is certain that great geographical changes took place 

 during the formation of the Lower and Middle Bagshot 

 Beds, but until the stratigraphy of this part of the Eocene 

 series is more completely worked out, it would be rash to 

 speak at all confidently with regard to the results of 

 these changes. There is, however, much reason to believe 

 that the tract which had hitherto been the principal 

 area of deposition was raised, and that large parts of it 

 became dry land, while the Paris basin was correspond- 

 ingly depressed, and the Hampshire basin became an 



1 This was Professor Prestwich's view in 1854 (see " Quart. Jouriu 

 Geol. Soc.," vol. x. p. 448), where he gives very good reasons for it. 



