112 Rev. A. Irving — Outlier of Upper Bagshot Sands. 



road from Arborfield Cross to Wokingham. The highest point on 

 this outlier is on Birtle Heath, where it is capped with Quaternary 

 Drift, containing an intermixture of rounded flint pebbles and sub- 

 angular discoloured flints, and partaking therefore of the general 

 character of the plateau gravels of this district. Close by Barkham 

 Lodge (at the south-east corner of Bearwood Park) the altitude is 

 marked on the Survey Map 280 above O.D. The well at Barkham 

 Lodge is 40 feet deep ; and as this well in all probability reaches 

 the water-bearing line at the top of the London Clay, we may take 

 this as representing very nearly the greatest thickness of the sands 

 of this outlier, together with the capping of later Drift. Bearwood 

 House is situated at an altitude of 240 feet, a little way off the mass 

 of Bagshot Sands, and stands on a drift-gravel, consisting of pebbles 

 and subangular fragments of flint embedded in a matrix of sand, 

 of the same character as that which forms the mass of the outlier. 

 I had a good opportunity during the summer of examining a section 

 of this in a wide open trench across the yard of the house. The two 

 feet of made earth at the top was well marked off from the gravelly 

 sand below, which was seen resting at depths of from 4 to 6 feet 

 upon an eroded surface of London Olay,^ which could be identified 

 with certainty, although it had lost its character as " blue-clay " by 

 oxidation to a bright brown red. The large lake in Bearwood Park, 

 about 50 feet lower than the house, lies in a hollow of the London 

 Clay. 



The Pebble-Bed. 



The best exposure of this in situ is in a " gravel-pit," about a 

 quarter of a mile to the south-west of Barkham Lodge, just behind 

 a small group of cottages, which stand in the angle of the roads. 

 At the present time some hundreds of tons of flint pebbles, and 

 nothing but flint pebbles, may be seen lying in heaps in this pit, the 

 pebbles being of various sizes from that of a hazel-nut up to large 

 pebbles measuring 6x4x2 inches. Nothing can exceed the 

 smoothness and regularity of their contour. In the face of the quarry 

 the pebble-bed is exposed in a horizontal band from 2 to 3 feet in 

 thickness. The pebbles are closely huddled together, as closely as 

 the Bunter pebbles are in the well-known quarries in Sutton Park, 

 near Birmingham, which during the last meeting of the British 

 Association 1 had the pleasure of examining in company with 

 Mr. Harrison. They are enclosed in a greenish sandy matrix, pre- 

 cisely like that in which the pebbles are embedded at some points 

 in the cutting north of Wellington College Station, about four miles 

 distant from this section. The boundary-line between the pebble- 

 bed and the bed of Bagshot Sand which comes immediately above it 

 is as sharp and well defined as anything can possibly be. The latter 

 bed is a strong loamy sand, very ferruginous and rather coarse in 

 grain ; so loamy that on weathering it flakes off on the face of the 

 section, and its outline becomes somewhat rounded. The beds 



1 Proved depth 256 feet. See Mem. Geol. Suryey, vol. iv. p. 423. Compare 

 my paper in Geol. Mag. for September, 1886. 



