262 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 16, 



This section shows that neither the London Clay nor the Reading 

 Beds are here more than from 12 to 15 feet thick, and therefore that 

 the Bagshot Sand is only 25 or 30 feet from the Chalk. In the London 

 Clay there were many pieces of ironstone, as at Wilton Kiln ; and in 

 one of them I found a cast of an Ostrea. This formation covers the 

 Beading Beds over a great part of the outlier ; but the patch of Bag- 

 shot Sand, the boundary of which is partly marked by a sHght rise of 

 the ground, only stretches about a third of a mile both northward and 

 southward of Stoke Parm. On the south-west of the farm, I saw a 

 deep and long ditch, freshly cut, in the sand ; and along the road, a 

 quarter of a mile north-east of the farm, sand is again shown. Further 

 northwards the beds are much hidden by pebble-gravel (drift) and 

 by wood. At Chisbury Barrow there is a section along the road- 

 cutting up the southern side of the hill, showing sands, with a little 

 clay, from the top of the Chalk up to the gravel that caps the hill. 

 These must altogether be some 40 or 50 feet in thickness. As I 

 have shown that, in another part of the outher, the Reading Beds 

 are not more than 15 feet thick, it seems unhkely that here they 

 should be three times that thickness ; I should conclude, therefore, 

 that the sands of Chisbury Barrow do not belong wholly to that for- 

 mation ; but rather that the upper beds, whicji in look are like those 

 above the London Clay at Stoke Earm, are also like them in age, that 

 is to say, are a part of the Lower Bagshot Sand, which formation 

 therefore here rests directly on the Reading Beds, the London Clay 

 having thinned out. I should not have ventured, however, to colour 

 those beds as Lower Bagshot on the Geological Survey Map, had not 

 such a step been confirmed by a section in an outlier further west, 

 where a thin pebble-bed, representing the basement-bed of the 

 London Clay, is aU that separates the Beading Beds from an over- 

 lying mass of sand. 



A little west of the large outlier just described are three smaller 

 outliers of the Beading Beds. Tottenham House stands on one, 

 from below which the Chalk rises sharply to the south; another 

 caps the Chalk over a great part of Bedvrin Common, but is much 

 hidden by a clayey drift ; and between these two there is a small patch, 

 barely separated from the first. 



Further westward is a more important outlier, stretching from 

 the house at the western end of Terrace Hill in a north-westerly 

 direction for a mile and a quarter. At its southern end the Chalk 

 rises up sharply to the south from beneath the Tertiary beds ; but, 

 as usual, the dip soon decreases towards the north. At the brick- 

 yard on the eastern side of the outlier, the sections in different parts 

 of the pit seem to show that the Tertiary beds here rest unevenly on 

 the Chalk ; for although the junction is not seen, the waved lines of 

 bedding in the sands, &c., look as if caused by the beds having given 

 way here and there, and fiUed pipes and hollows in the underlying 

 Chalk. The section does not show an unbroken series of the Tertiary 

 beds from top to bottom ; but the upper beds are clear. Plastic clay, of 

 the Beading Beds, chiefly green, has been found above the Chalk ; but 



