TEE BAGSHOT BEDS OF THE EOXDOX BASEST. 



389 



The so-called " Lower Bagshot " I regard as essentially fluviatile, 

 the so-called " Middle Bagshot " as, upon the whole, delta and lagoon 

 deposits, the lagoons having been partially saline, perhaps by occa- 

 sional intrusions of the sea and by percolation through fringing 

 shingle-terraces, the conditions represented by the " Middle " beds 

 being feebly anticipated in different localities and at different 

 horizons in the " Lower " series. 



3. The lower levels of the Middle series towards the east (as shown 

 in well-sections) may perhaps be due to a general subsidence, the true 

 deltaic conditions encroaching upon the land as subsidence progressed, 

 so as to give a certain parallelism between beds of this horizon 

 towards the west and the earlier deposits of the " Upper 99 sands 

 towards the east or seaward margin of the area. 



4. Though we fail to find such evidence on the south flank, we 

 have on the north flank of the area strong cumulative evidence of 

 marginal conditions, and consequently an indication of the northern 

 limit of this Eocene estuary at successive stages of the process. 



5. Massive pebble-beds belong for the most part to the " Middle " 

 group, though occasionally occurring at low horizons in the " Upper " 

 group, and afford the strongest evidence which the whole series 

 offers of important changes in the relations between sea and land at 

 about that stage of the deposition of the Bagshot Beds. 



Xote. 



"With regard to the southern margin of the district, it is only 

 right that I should make here the following quotation from the 

 original MS. of the paper which was in the hands of the Officers of 

 the Society at the end of last year : — " It was my intention to deal 

 with the southern margin of the Bagshot area in this paper; but, 

 as the work has grown to considerable dimensions, and as other 

 duties have prevented me from dealing so thoroughly with the details 

 of that side of the district as I could wish, as, moreover, the Aldershot 

 district is somewhat complicated and is being worked out by my friend 

 and former pupil, Lieut. H. G. Lyons, E.E., E.G.S., it has appeared 

 better to defer the fuller consideration of it for a future communi- 

 cation.''' I only add now (April 30th) that in the part of the paper 

 which appeared in the Society's Journal (vol. xlii.) last year, dealing 

 with this portion, there are many points which I consider open to 

 criticism ; but these are dealt with in Mr. Lyons's paper. The 

 evidence recently furnished by the Brookwood well-section shows 

 that the notion of the possible occurrence of Beading Beds in the 

 Mytchett section is quite untenable. 



Erratum. 



In my former paper (vol. xli. p. 508, line 4) : — 



for Lower Bagshot read Upper Bagshot. 



