Rev. A. Irving — Outlier of TJipinr BagsJiot Sands. 115 



Bagsliot Sands, where the strongest possible evidence (that of proved 

 superposition) leaves no room for doubt as to its occupying a low 

 horizon in the Upper Bagshot. 



The longest of the three spurs mentioned above as projecting to the 

 south of the mass of the outlier terminates in a hill about 240 feet 

 above O.D., just to the east of Manor Farm, and rather more than a 

 quarter of a mile to the north of Barkham Church. This hill is of 

 London Clay uncovered by drift on its slopes, and capped by a mass 

 of pebbles and sand of the same nature as that in the Barkham pit. 

 The pebbles were dug here in quantity for some time for road 

 material. The pit is now ploughed over, but the enormous number 

 of well-rounded pebbles seen in the ploughed surface at the top of 

 the hill bears testimony to the nature of this hill-cap, though, not 

 having seen the pit open, I am unable to say whether the cap con- 

 tained the pebble-bed in situ, or consisted of a mass of re-constructed 

 materials. 



There are some very ancient gravel-pits about half a mile nearly 

 south-west of the Scotch Farm, where the nature of the drift which 

 caps the outlier can be studied ; and in the open field close by there 

 is an open gravel-pit on the crest of the hill, remarkable for the 

 number of Sarsen-stones which occur in the sandy gravel, and for 

 the huge size of some of them ; but of the Sarsens I hope to have 

 something to say in a future communication, in addition to what I 

 have already written.^ 



One or two remarks are suggested by this Bagshot outlier at Bear- 

 wood. 



1. The pebble-bed occurring here so remarkably well developed 

 (as has been shown above) in such a way as to leave no possible 

 room for doubt of its Bagshot age, at the same altitude as the pebble- 

 bed at the base of the Upper Bagshot in the more central parts of 

 the Bagshot area, we can hardly avoid assigning it to the same 

 horizon. Though there is no fossil-evidence to bring forward in 

 support of this view, it must be borne in mind that it is only 

 from a few sections in the Upper Bagshot that fossils have been 

 recorded, and such as have been found ai'e nothing more than mere 

 ferruginous casts. There is no dip to the south or east in this 

 pebble-bed. 



2. If, on the strength of the pretty strong physical evidence cited 

 above, we are led to assign the outlier at Bearwood to the horizon to 

 which it is assigned in this paper (and I see no valid argument 

 against so doing), then we have here a clear case of Upper Bagshot 

 Sands resting directly upon the London Clay ; a phenomenon which 

 can only be explained by the former overlap of the Upper members 

 of the series.^ 



1 See Proc. Geol. Assoc, vol. viii. pp. 153-160. 



2 A very similar case of a massive pebble-bed at the base of the Brachlesham Series, 

 and restina: upon London Clay, has been recently mentioned in a letter to the author 

 by Mr Whitaker, as occurring in the Hampshire Basin. No authenticated instance 

 of a bed of pebbles in undoubted Lower Bagshot Sands has yet been recorded in this 

 western part of the London Basin, while those in Essex may for very good reasons 

 be assigned to a higher horizon. (See "Whitaker, Geol. of London, p. 52.) 



