174 KEY. A. IRYINa OX THE STRATIGRAPHY 



general dip in this direction), when we come to Section S (see 

 below) ; but at the white gate an occupation-road strikes almost 

 due north down the steep flank of the hill, evidently crossing the 

 unexposed green earthy beds of Section S, since, at a distance of 

 275 yards, by the map, and at an altitude of 238' O.D. by level- 

 ling, the clays of the California type, referred to Nos. 9 and 10, 

 crop out, and these can be traced a good distance along a clean 

 ditch to the north. They are seen again in the lower part of 

 the lane leading east to Warren Lodge ; and they are well ex- 

 posed in the cutting on the JSTine-mile Eide (referred to above, 

 p. 173), 300 yards further to the north, with their base exposed 

 in a ditch-section at 207' O.D., below which the fine quartz- 

 sands (No. 11) crop out plainly enough. I draw particular atten- 

 tion to the ax^proximate agreement of levels of the clays which 

 crop out beneath the green-earth series on the north flank of this 

 western spur of the hills vrith those of the same clays in the 

 California clay-pits (Section Q). 



In considering the above facts, we have to choose between 

 three possible explanations of the altitude (300' O.D.) of the 

 pebble-bed at the corner of the lane north of the church. Either 

 (1) the clays of the horizon, No. 5, are suddenly developed to a 

 thickness of from 30 to 40 feet ; or (2) a clay with a strong pebble- 

 bed occurs 20 feet or more above the base of the Upper Sands ; 

 or (3) there is a strong local northerly dip on the north flank of 

 this hill. Opinions may differ : I prefer the third explanation as 

 most probable. Such a local feature might easily result from 

 some post-Eocene faulting in the Secondary Eocks below and a 

 consequent flexure of the more yielding Eocene beds. Assuming 

 the true dip here to be north, I have estimated, from approxi- 

 mate data, a dip of 1 in 6-6, or nearly 9°, in the upper hill-flank, 

 the dip diminishing as we descend the hill. 



Section S. In lane 7iorth of Finchampstead Church. 



feet. 



a. Strougclay, distinctly laminated at the base 3 (I!^o. 5). 



[Thin layer of bog-ii'on-ore.] 



b. Green earthy sands, laminated purplish seams ofl 



clav, and below these strong loamj' sands, ^Tith I , gj^ .-^ 7 Xr f^^ 

 much green sand in pipes and layers, as in bed / [ ^ ^ '' 



Section P J . 



c. Clays and loams * (more clayey in upper part) ? (IS'os. 9 & 10). 



30 feet or more. 



The lane trends from this point nearly due north to Mue-mile 

 Eide, within a quarter of a mile of the open pit in London Clay 

 mentioned above. Taking into account the depth of the water- 

 bearing line in the wells in the neighbourhood, and the altitudes of 

 the respective outcrops of the Lower Sands (No. 11) and of the 

 London Clay, the sands below No. 10 cannot be here much more 



* These, it will be observed, crop out on the same level as at 300 yards to 

 the east, and as at California, nearly 1 mile to the east. 



