134 Reports and Proceedings — 



2. "The Physical History of the Bagshot Beds of the London 

 Basin." By the Eev. A. Irving, B.Sc, F.G.S. 



The author, in reviewing the position taken up by him, attempted 

 to estimate the value of such palaeontological evidence as exists, and 

 insists on the importance of the physical evidence in the first place. 

 He gave reasons for considering the evidence of pebbles, pipe- 

 clay, derived materials, ferruginous concretions, percentages of 

 carbon (ranging in the more carboniferous strata up to nearly 2^°/q) 

 taken together with the evidence of carbon in combination, as 

 adduced in former papers, freshwater Diatoms (now perhaps recorded 

 for the first time in the Middle and Lower Bagshot), and the micro- 

 scopic structure of the sands and clays, as furnishing such a cumu- 

 lative proof of the fluviatile and delta origin of the majority of the 

 Middle and Lower Bagshot Beds, as can hardly be gainsaid ; while 

 he regarded the wide distribution of the Sarsens, taken along with 

 the absence of such evidence as is quoted above, as indicating, along 

 with the fauna, a much greater former area for the Upper Bagshot 

 than for the strata below them. 



He referred to the evidence furnished by the Walton section (Q.J. 

 G. S. May, 1886), the Brookwood deep well (Geol. Mag. August, 

 1886), the contemporaneous denudation of the London Clay (Geol. 

 Mag. September, 1886) as affording further support to the view 

 which he has advocated ; gave six new sections on the northern side 

 of the area, showing (1) the attenuation of the Lower Bagshots 

 beneath the Middle Bagshot clays, (2) the greater development of 

 clays towards the margin at the expense of the sands, (3) contempo- 

 raneous transverse erosion of the London Clay, (4) cases of overlap, 

 (5) the occurrence of massive pebble-beds at nearly the same altitude 

 along the northern flank underlying (as at Easthampstead and Bear- 

 wood) Upper Bagshot sands, and resting either immediately upon, 

 or in near proximity to, the London Clay ; and added an account of 

 his observations on the flank of St. Anne's Hill, Chertsey, which he 

 takes to be nothing more than an ancient river-valley escarpment, 

 subsequently eroded by rain-water, the hollows thus formed having 

 been subsequently filled up and covered over by pebbles and other 

 debris of the beds in the higher part of the hill, these assuming the 

 character of ordinary talus material. The consideration of the 

 southern margin of the Bagshot district is reserved for a future paper. 



The author considered that his main position, resting as it does 

 upon physical evidence, remains untouched by the attempt of later 

 writers to disprove it ; while the disproof breaks down even on its 

 own lines (the stratigraphical), the paper in which this disproof is 

 insisted upon being chai'acterized by (1) an incomplete grasp of the 

 problem on the part of its authors, (2) equivocal data, (3) omission 

 of important evidence, (4) inconsistencies, (5) erroneous statements. 



The author (while con-ecting some errors of stratigraphical detail, 

 which appeared in his former paper, from insufficiency of data) 

 maintained that (though occasional intercalated beds with marine 

 fossils may be met with, as is commonly the case in a series of delta- 

 and lagoon-deposits) the view he has put forward is, in the main, 



