Rev. A. Irving — The Bagshot Beds and London Clay. 405 



From the London Clay at Aldershot, in the brick-yard due south 

 •of the Station. I have obtained Cyprosa BowerbanTcii, Modiola elegans. 

 The last-mentioned is very abundant in the septaria of that locality. 



In his excellent work, Stratigraphical Geology and Palaeontology, 1 

 Mr. Etheridge remarks : " Prof. Prestwich has shown that there are 

 traces of palasontological zones in the London Clay, the lowest 

 indicating in the east of the area of deposit a maximum depth of 

 water (500 feet), while a progressive shallowing is seen in the 

 higher zones, the uppermost of which contains the chief part of a 

 terrestrial flora, as well as the fish and reptilian remains, all of which 

 are seen in the Sheppey Beds." 



The thicknesses given by Prof. Prestwich 2 for the London Clay, as 

 proved in two wells at Sheerness, are 347 feet and 356 feet, very 

 near approximations to the least thickness (371 feet) assigned in my 

 last paper to the same formation in the Brookwood section. There 

 too, according to Mr. Whitaker, 3 "the London Clay has a more 

 loamy character and brown colour ; there are also some beds of sand 

 (north of Wyburns) which become more numerous further east, so 

 that there is no sharp line of demarcation between the undoubted London 

 Clay and the overlying sand, which has been referred to the Bagshot 

 Series." This corresponds very well with what I have described as 

 indicating a passage in the Brookwood section ; while such features 

 are conspicuous by their absence in all sections where I have seen 

 the Bagshots resting on the London Clay along the flanks of the 

 present Bagshot area. 



It is much to be regretted that the works at Brookwood were not 

 watched during the progress of the well through the London Clay. 

 As it is, there would appear to be no record of any traces of a 

 ' terrestrial flora ' or of ' fish and reptilian remains ' to correspond 

 with those of the Sheppey Beds. In the most complete as to its 

 details of the well-sections referred to in this paper — that of the 

 Wokingham Town Well — furnished on so excellent an authority as 

 that of Prof. T. Bupert Jones, there is no mention whatever of any 

 traces of those remains which seem to characterize the higher zones 

 of the London Clay ; nor have I met with any in the brickyards at 

 the surface. It would appear, therefore, that at Wokingham the 

 evidence furnished by the London Clay itself, as to the removal by 

 denudation of all the upper portions of that formation, before the 

 Bagshot Sands were deposited upon it, is pretty direct and conclusive ; 

 and this entirely harmonizes with the observations, which I have 

 previously recorded, 4 of the evidence of erosion of the London Clay 

 beneath the Bagshot Sands at Wokingham, and the occurrence of 

 rounded flint pebbles on that eroded surface at the bottom of the 

 Bagshot Sands there exposed. 



Taking all the facts adduced in this paper, and comparing them 

 with those mentioned in my paper on the Brookwood section, it is 



1 Page 610. 



2 Q. J. G. S. vol. x. p. 404, quoted by Mr. Whitaker at p. 469 of the Memoir 

 on the London Basin. 3 Memoir, p. 317. 



4 Q. J. G. S. August, 1885, pp. 504, 505 ; Proc. Geol. Association, vol. ix. p. 222. 



