164 KEY. A. lEVLJfG 02? THE STEATIGEAPHX 



15. St7pplementaet jS'otes on the Stkatigeaphy of the Bagshot Beds 

 of the LoifDoi? Basiis^. By the Kev. A. Ieyi2«^&, B.Sc. (Lond.), 

 B.A., P.G.S., Senior Science Master in Wellington College. 

 (Eead January 11, 1888.) 



In this paper it is intended to lay before the Society the results of 

 additional work in this Formation done during the year 1887. It 

 deals with the succession of the beds all along the northern margin 

 of the district, from Parley Hill near Eeading to Englefield Green, 

 and with the deYelopment of the formation in the more westerly 

 portion of the area (basin of the Kennet). 



Paet I. 



In this part of the paper I shall attempt to show from the 

 description of numerous sections that the inference as to marginal 

 conditions in my last paper is found to hold all along the northern 

 ilank of the district. 



In the recent discussion of this subject some ambiguity has crept 

 into the use of the term " Middle Bagshot." Por my part I have, 

 as I belioYe, consistently used the term throughout with the exact 

 connotation which I gave to it in the year 1883 *, and in the 

 Quarterly Journal of the year 1885 (vol. xli. p. 494). In the 

 WeUington-CoUege section it is seen to include beds of the horizons 

 I^os. 3-10 ; and whenever I have found a complexus of beds 

 answering in general physical character to these, I have assigned 

 them to the Middle Stage without taking the empirical consideration 

 of mere thickness into account: since in none of the deep-weU 

 sections of the interior of the district have we anything approaching 

 to a recurrence of such a series in either the Upper or Lower stages. 



NoETH Plank op Easthaitpstead Plain and Chobham Etdges. 



Referring now to fig. 1 and section E of my last paper f, I proceed 

 to consider a series of sections in which we can recognize (whoUy 



* Proc. Geol. Assoc, vol. viii. pp. 144, 146. On this point I am, I believe, 

 quite in harmony with the Survey, and with Prof. Prestwich (see Quart. Journ. 

 G-eol. Soc. vol. xliv. " On the Correlation of the Eocene Strata "). 



t During this winter the basement-line of the beds 2sos. 9 and 10, with fine 

 whitish quartz sands (No. 11), ciu'rent-bedded below, has been exposed to open 

 day in a sand-pit 470 yards east of the new Wokingham road, and 120 yards 

 north of Nine-mile Eide, at 230' O.D. This is found, when scaled, to be in 

 perfect stratigraphical alignment with the altitudes given for that horizon in 

 the table on p. 384 (Quart. Journ. Greol. Soc. vol. xHii.). In the clay-pit 

 further to the east the dark grey sandy shales (of which about 6 ft. are exposed 

 in the sand-pit just mentioned) are reached beneath 7 ft. of the "mild clay" 

 (with ferruginous concretions), a very good brick-material, over which there lies 

 6 ft. of drift, consisting of contorted sands and pebbly gravel. Taking into account 

 the altitude of the base of No. 10 (230' O.D.), the depth of several wells, and 

 the fall of the ground until the London Clay crops out, the 40 ft. obtained by 

 scaling appears to be an outside limit of the thickness of the quartz-sand series 

 (Nos. 11 and 12) as compared with the 92 ft. of them in the weU-section at 

 Wellington College. 



