184 EEV. A. lEVnfG ON" THE STEATIGEAPHY 



beds, was certainly deposited in a region of debatable ground 

 between sea and land — the pebble-beds probably recording marked 

 inroads of the sea * accompanied by the drifting inland of portions 

 of the " chesil-beaches " piled up by ordinary tides along the sea- 

 ward margin of the delta. Ultimately the area was converted 

 by regional subsidence into a tidal arm of the sea (probably in 

 connexion also with the Hampshire Basin) or marine estuary, in 

 which the Upper Sands were deposited, to a thickness of which we 

 have now no direct evidence, the onlj^ remains of the younger strata 

 being perhaps the displaced Sarsens f and the reconstructed loamy 

 sands intercalated in places with the plateau-gravels. 



Discussion". 



The President said that he had received a letter from Prof, 

 Prestwich expressing regret at being unable to attend. Prof. 

 Prestwich thought that, probably, Mr. Irving's view as to the Lower 

 Bagshots being of irregular thickness is correct ; this would help 

 to confirm his own opinion as to its being Lower Eocene. It had 

 struck him that, in some of his former papers, the Author might 

 have mistaken a surface-drift of green earth, pebbles, and clay 

 for the Middle Bagshots. 



Mr. MoNCKTON would express no opinion on the general remarks. 

 Eeferring to the jN'ewbury district, he had been with Mr. Irving 

 when they visited the sand-pit shown towards the centre of the 

 section. These sands he at first believed to be Lower Bagshots, but 

 from certain lithological peculiarities, and also from the presence 

 of forms like the casts of bivalve shells, he was forced to the con- 

 clusion that the beds were Upper Bagshot. This supposition 

 suited very well with appearances on the south side of the 

 syncline, but he would like further to examine the northern side. 



He next referred to the Wellington-College and Pinchampstead 

 sections, which he criticised adversely. The question was whether 

 the several beds therein described were similar beds, or a recur- 

 rence of a similar state of things on different horizons. At the 

 doubtful points there are neither fossils nor green-sand beds, and 

 the Author had referred beds in dispute very differently in his 

 several papers, as instanced by his change of opinion at Bearwood 

 and in the Ascot well-section. Correlations based upon altitudes 

 could be of no value unless the beds were horizontal, whereas there 

 was abundant evidence of a dip to the south J. 



Mr. Heeeies disagreed with the Author's views as to the Wel- 

 lington-College sections, and considered that he had not added much 



*■ The prevalent discoid form of the flint pebbles (as one sees them in the 

 Chesil Beach at Portland, and in the older Triassic " chesil-beach " at Budleigh- 

 Salterton) in some of our pebble-beds speaks strongly for shore-action. It is 

 not improbable that many of them have been derived from the Chalk of Nor- 

 folk, or even of more distant regions. 



t See paper by the author on the " Bagshot Beds of the London Basin and 

 their associated Gravels," Proc. Greol. Assoc, vol. viii. 1883. 



j In connexion with Mr. Monckton's remarks see note * p. 173. 



