580 MESSES. GAKDITEIl, KEEPING, AlyT) MONCKTON" ON THE 



Bagshots *. But Prof. Prestwicli, when again dealing with the sub- 

 ject in 1856, still considered the question unsettled ; for he says : — 

 " How far the Upper Bagshct Sands are related to the Bracklesham 

 series it is difficult to say. The few fossils I have found in those sands 

 are not sufficiently distinctive to enable me to pronounce a decided 

 opinion. As, however, the fossiliferous Middle Bagshot Sands are 

 very thin, and represent apparently only the lower or middle part of 

 the Bracklesham Series, I think it probable that it is the upper beds 

 of sand and clay of the latter which pass northward into the thick 

 sands of the Upper Bagshot Sands. Still, it is possible that part 

 of them may represent the Barton Series ; for we see at Barton 

 how shifting the upper part of that series is, how clay predominates 

 at one place and sands at another '' t. The Geological Survey Memoir 

 of 1872 on the London basin contributed little further evidence as 

 to the age of the beds under consideration, and to the present day 

 Prof. Prestwich regards it as an open question j. Dumont, however, 

 classed the Barton Beds with the Upper Bagshot Sands, and they 

 have been generally regarded as more or less equivalent in age. 



Area. — The Upper Bagshot Sands are chiefly restricted in the 

 London basin to what is termed the "main mass" of the formation 

 at and around Bagshot Heath, and extend from the eastern end of 

 Berkshire into Surrey and Hampshire. In the Hampshire basin 

 the Barton Beds occupy the coast-section in Christchurch Bay for 

 about three miles ; they have been traced inland to a little east of 

 Bingwood, near the village of Powner, and the Corhida-zone has 

 been recognized in brick-pits at Bramsgrove, not quite halfway 

 between Powner and the coast. The C/iama-beds have been seen 

 at Binstead Manor, on the Compton estates, a mile north of Lynd- 

 hurst § (by the Eev. J. Compton, Eev. 0. Fisher, and by Mr. Keeping). 

 In the Isle of Wight they crop out and are well exhibited at Alum 

 Bay, and are equally present at the other extremity, Whitecliff Bay. 

 Mr. Bristow records that he met with Barton fossils at Gunvelle, north 

 of Carisbrooke, and the clays without fossils have been identified at 

 one or two other spots in the island. The area over which they extend 

 is remarkably limited, considering their importance. Prof. Prestwich 

 correlated them with the Sables de Beauchamp in France || and the 

 Laekenian system in Belgium^, and the accuracy of his views in 

 this case has never been disputed. 



Thickness. — The thickness of the Upper Bagshot Sand in the 

 London basin nowhere greatly exceeds 200 feet, and is usually 

 much less, owing to denudation. It is, except the gravels, the 

 highest formation in the area. In the Hampshire cliffs the whole 

 series, from the pebble-bed at the base to the top of the Long-Mead- 



* Journ. E.oj'al Agricult. Soc. vol. xii. p. 445 (1851). 



t Quart. Journ. Geol. Soc. vol. xiii. p. 132. 



J In his latest works, Quart. Journ. Geol. Soc. vol. xlir. (1888), p. 107, and 

 Geology, vol. ii. p. 363, he still regards the question as unsettled. 



§ Mem. Geol. Surv. I. of \¥ight, Bristow, 1862, p. 46. 



II Quart. Journ. Geol. Soc. vol. iii. (1847) p. 354. " On the probable Age of 

 the London Clay and its relations to the Hampshire and Paris Basin Tertiary 

 System." ^ Ibid. vol. xiii. (1857) p. 107. 



