TJPrEK EOCENE (bARTON AND UPPER BAGSHOT FORMATIONS). 609 



factory Upper Bagshot section (7). These sections prove that the 

 base of the Upper Bagshot rises up to the 300-feet contour-line at 

 this northern end of the main mass. 



Passing eastwards to Chobham Common the following beds are ex- 

 posed on a road at the point 8. 



1. Capping of pebbles on hill top (remains of Upper Bagshot pebble-bed). 



2. Yellow sandy clays, say 10 to 15 feet. ] 



3. Green sand, with Cardita planicosta, I Bracklesham Beds. 



Corhiila gallica, &c., in abundance. J 



The clays of bed 2 were worked for bricks half a mile north of 

 Chobham Place, and the same clays and underlying green sand are 

 exposed in another disused brickfield near Titlarks Parm (9) (details 

 given Q. J. G. S. vol. xlii. p. 404). The low hill just above 

 this section (10) is capped with pebbles from the Upper Bagshot 

 pebble-bed. These sections prove that the surface of the higher 

 part of the Chobham-Common plain is Middle Bagshot, and the 

 round-topped hills which rise above it are Upper Bagshot. In two 

 of them there are good sections in characteristic Upper Bagshot sand 

 (11, 12). At Long Down there must be over 50 feet of Upper Bagshot, 

 and it appears to extend slightly further than is shown on the 

 map. 



A brickfield has quite recently been opened close to Chobham 

 Place (13) and at about the same level. In March 1887 some 3 or 

 4 feet of stiff grey clay (Bracklesham) was shown, and this together 

 with the former sections leads us to believe that Chobham Place is 

 correctly mapped Bracklesham, so that we cannot confirm Pro- 

 fessor Prestwich's section in which 100 feet of Upper Bagshot are 

 represented overlying the Middle Bagshot at that place (Q. I. G. S. 

 vol. iii. p. 384, fig. 4). 



Several of the hills east of Chobham Place, at Ottershaw, and 

 towards Chertsey are capped with pebbles, for the most part pro- 

 bably derived from the Upper Bagshot basement-bed ; and the great 

 pebble-bed at the top of St. Ann's Hill, Chertsey, in all probability 

 is on the same horizon, though, unfortunately, the fossils which 

 occur in it are not sufficiently perfect for identification. 



Chobham Kidges attain a height of over 400 feet, and are com- 

 posed of Upper Bagshot sand capped with gravel ; and if the pebble- 

 bed is taken as its base, it extends much further to the east than 

 is shown on the map. 



The well at the Albert Asylum (14), on the top of the ridges, 

 furnishes the greatest recorded thickness of Upper Bagshot, viz., 

 226 feet of sand and 2J feet of pebbles. The surface is about 400 

 feet and the level of the Bracklesham beds 171 1 feet above O.D. 



A little to the north and west of this well very fine sections were 

 opened on the railway from Bagshot to Camberley (15). They 

 showed sands of different tints of yellow and brown in broad bands 

 of varying shades, and casts of badly preserved shells were very 

 abundant. In our collection there are over 100 specimens from the 



2s2 



