436 



ME. H. G. LYONS ON THE LONDON CLAY 



half a mile east, described bv Messrs. Monckton and Herries * as 

 occurring beneath the clay-beds of the Middle Bagshots, which I have 

 mentioned above, the arguments already put forward for conform - 

 ability and constant northerly dip of the beds, and the regular 

 succession of the beds in the Long Yalley, I consider the Ash-Station 

 Well to show the basement beds of the Lower Bagshot of a character 

 very similar to those in the Brookwood and South-Camp deep borings. 

 Moreover, the London Clay crops out 1200 feet south on the read 

 leading to the South-Western Station at the same level as the Station. 

 This gives a slope to the north of 61 feet (the thickness of the 

 Bagshot strata) in 1200 feet, or about 1 in 20, which would give 

 2° 52', which dip corresponds well with that measured by Mr. 

 Monckton at East-Wyke Farm (Quart. Journ. Geol. Soc. vol. xlii.). 



Also, at the South- Western Ash-Green Station, a deep well-boring 

 (Surv. Mem. vol. iv. p. 537) gives London Clay and Reading beds as 

 370 feet thick. Deducting 80 feet for the Reading beds, we have 

 290 feet as the thickness of London Clay, 1500 feet from the outcrop, 

 and a slope of 1 in 20, which we have just found above for the over- 

 lying Bagshot strata, gives a thickness of 75 feet to be added. A 

 further deduction of the difference in level between the well, 290 feet, 

 and the outcrop 255 feet above O.D., viz. 35 feet, is also required; 

 and thus we have a thickness of 330 feet for the London Clay, which 

 is about the same as that in the South-Camp boring and in the 

 Aldershot Waterworks, as will be shown again later. I therefore 

 consider that there can have been but little erosion of the London 

 Clay at this point before the deposition of the Bagshot beds. 



In describing the well-section at Ash Station, S.E. Railway,. 

 Mr. Irving (Proc. Geol. Assoc. he. tit:) says, " Here we are about the 

 level of the southern end of the Fox Hills, which consist of un- 

 doubted Upper-Bagshot sands." This would account for his drawing 

 the Bagshot beds horizontal in the woodcut there given ; but as the 

 well-mouth is over 60 feet below the outcrop of the Upper-Bagshot 

 sands, in order to bring them into the well-section a downward slope 

 of 108 feet in 1800 feet must be allowed, since to the 60 feet given 

 above the 48 feet of yellow sand, called Upper Bagshot in the section, 

 must be added. This gives a slope of about 1 in 17 to the south ; 

 and by the well-section and the point of outcrop of the London Clay, 

 we get a slope of about 3°, or, say, 1 in 20 north for that formation. 

 Of this Bagshot anticlinal, which is not shared in apparently by the 

 London Clay, I maintain we have no sufficient evidence ; and I have 

 already argued against one at Thorn Hill, and shall do so again 

 when describing the section across Aldershot Town. Moreover, the 

 anticlinal here would bring in Middle-Bagshot beds and Upper- 

 Bagshot sands overlying them, dipping 4° south, just about where 

 Messrs. Monckton and Herries have described Lower-Bagshot sands 

 underlying Middle-Bagshot basal clays, and dipping about 3° north. 

 This appears to me conclusive. 



I have quite lately obtained (through the kindness of General 

 Hammersley, of Ash Grange) some details of a deep well in the London 



* Quart. Journ. Geol. Soc. vol. xlii. p. 413. 



