Geological Society of London. 285 



Middle Bagshots about 55 feet. 



Lower Bagshots „ 115 „ 



London Clay ,, 335 „ 



It was inferred from various calculations, as also from direct obser- 

 vation, that the thickness of the London Clay shows no diminution 

 throughout the section, being nearly the same also at Ash and at 

 Aldershot Place. 



In " Caesar's Camp " the Pebble-bed occurs at altitudes ranging 

 from 500 to 550 feet. 



The author concluded that wherever we can fix the top or base 

 of the London Clay, we get a northerly dip of 2^° to 3°, showing a 

 fairly constant thickness of from 330 to 340 feet. The same thing 

 occurs from Odiham on the west to Ash on the east, whilst at 

 Brookvvood the London Clay is thicker. He also assumed the exist- 

 ence of a passage from the London Clay up into the Bagshot beds in 

 the deep wells or borings at Wellington College, at Brookwood, and 

 at South Camp. Hence at these points there can have been no great 

 erosion or unconformity. The overlying Bagshots lie conformably 

 on the London Clay and on each other. 



2. " Supplementary Note on the Walton Common Section." By 

 W. H. Hudleston, Esq., M.A., F.R.S., Sec.G.S. 



The principal object of this paper was to point out the occurrence 

 of certain beds of clay or loam in what are usually known as the 

 " Lower Bagshot Sands " of West Surrey. It was shown that the 

 sandy series. No. 3, of the previous paper is overlain by a second 

 clay series, No. 4, whose mode of occurrence and lithology were 

 described. This is again succeeded by a third sandy series. No. 5, 

 which, it is believed, is maintained throughout the remainder of the 

 cutting as far as the Eiver Wey, with occasional clay patches 

 deposited in small basin-shaped hollows of the sand. 



The nature and geological position of the brick-earth of Hatch 

 on Woburn Hill was next described. This forms a portion of the 

 " clays most extensively developed between Addlestone and Chert- 

 sey," referred by Professor Prestwich to his Middle Bagshots, and 

 mapped as such by the Geological Survey. The clay is seen to 

 occur as a lenticular mass, 21 ft. thick at its maximum, in a hollow 

 of loose yellow sand ; the current-bedding of the upper loamy layers 

 is very marked towards the north end, with a strong false dip to the 

 south, i.e. towards the centre of the basin. 



Accepting as the true datum line for the base of the Middle 

 Bagshots in this district, " the foliated clays, more or less sandy, 

 having a thickness of 14 ft," which are shown by Prof. Prestwich 

 to be typically developed in the railway-cutting on Goldsworth Hill, 

 it was contended that the Hatch brick-earth cannot be correlated with 

 these. The true basal beds of the Middle Bagshots in this district 

 differ somewhat in their physical characters ; but it was on strati- 

 graphical grounds mainly that the author endeavoured to show 

 that the Hatch brick-earth should, despite its argillaceous nature, 

 be assigned to the Lower Bagshots. A diagrammatic section from 

 St. George's Hill (245 ft.), through Woburn Hill (92 ft.), to St. 



