THE BAGSH0T BEDS OF THE LONDON BASIN. 383 



along the small brook-escarpment a little way to the west and parallel 

 to the railway. It is seen a little way further north in a dipping-well 

 by the east side of the line, and in the banks of the brook on both 

 sides. In the wood to the east it passes under beds nos. 9, 10, which 

 form a small plateau through Gorrick Plantation, on the ~N.W. corner 

 of which bed no. 10 appears to touch the London Clay in the ditch 

 outside the fence. The presence of the latter formation is further 

 shown by oak trees, by the presence of Silverstock Bog (see 

 Ordnance map), by the fact that the clay was dug into in draining 

 last summer, and was dug for brick-material about j, mile to the 

 west a few years ago. The bed seen in the cutting a little further 

 north must be a continuation of no. 10, both lithologically and by 

 the features of the ground ; and it appears to be continued through 

 Luckley Park, on the north side of which it is only cut off from the 

 Wokingham outlier by the line of erosion of the Emm Brook. It is 

 exposed just north of this in a small road- section, and it forms a small 

 plateau, which is cut through on the railway, where the base of 

 no. 10 is seen, sharply denned from no. 11 (here well cleaned by 

 oxidation), at 210 (O.D.). 



The following small clean section in the brook-side south of Ravens- 

 wood shows the mixed character of bed no. 10 *, and the consequent 

 impossibility of determining its dip by comparison of small sections 

 of it. 



Section D. Bank of Broolc near Ravenswood. 



ft. in. 



a. Drift 3 0 



b. Stiff loam, yellow and brown 1 0 



c. E-ather strong clay, yellow and brown 0 9 



d. Strong loamy sand with thin pipe-clay partings and red and puce- | 0 q 



coloured ferruginous layers j ° 



Total exposure 7 9 



A rough analysis of a sample from the same bed a little further 

 down the brook gives : — free silica, 60 per cent. ; clay, 25 per cent. ; 

 ferric oxide, 13*5 per cent. ; sodium chloride, 0*5 per cent. ; water 

 of hydration, about 1 per cent. This bed is, in fact, so variable that 

 I mistook portions of it in the railway-cuttings for bed no. 4 ; and 

 this was the main, though not the only, reason why I suggested an 

 anticlinal in my previous paper. Along this line of section A (fig. 1) 

 the dip, as indicated by the base of bed no. 10, would appear to be 

 about from 10 to 15 ft. in 3 miles ; but the true dip is probably some- 

 what greater and in a more easterly direction, to judge from the 

 general strike f . 



Numerous well-sections in Wokingham give the same succession 

 of beds as we find in the Tangley cutting. Everywhere the water 



* It is by no means so " homogeneous " as one would suppose from the well- 

 specimen. 



t More correct determination of levels shows that the pebble-bed in the 

 lower lake at Wellington College is on the horizon of no. 6. That on the 

 horizon of no. 3 has been proved higher up the valley at 261 (O.D.). 



2 D 2 



