14 ME. W. WHITAKEll ON" THE [vol. lxxv, 



(b) Hampshire Basin. 



In our other great Tertiary tract, patches of pebble -beds are 

 •shown on some of the new sheets of the Geological Survey Map, 

 but without having any special name given to them. 



Starting on the west, a patch in Wiltshire has been shown at the 

 north-western corner of Sheet 315, and apparently it should con- 

 tinue into Sheet 814; but, as there is no trace of it on the 6-inch 

 Map (Wiltshire, 72, 77) it seems likely to be merely an error 

 in colouring. 



There are twelve patches near Sher field English, in Hampshire 

 '(Sheets 315 & 299), and five others near Braishfield, also in 

 Hampshire (Sheet 299). In the index of colours to 299, for 

 which I believe I am answerable, the pebble-beds are placed 

 ^between the London Clay and the Heading Beds, without being 

 bracketed with either; that is, where Blackheath Beds would come 

 in. In the index to 315 they are marked as at the top of the 

 Beading Beds. 



Another patch at Clapham, in Sussex (Sheet 317), is indexed 

 ;as at the bottom of the London Clay. It is worked for gravel. 



This diversit}^ in the index of colours on the maps shows the 

 open mind of the Geological Survey and a proper hesitation in the 

 classification of what seemed to be a somewhat doubtful deposit. 

 Now, when we are not dealing with isolated maps, but can take 

 all together, I have little hesitation in claiming these pebble-beds, 

 or nearlv all of them, as belonging to the Blackheath Series, though, 

 of course, there may be pebbles in the Beading Beds ; some of the 

 patches are mapped as directly underlying London Clay, while 

 others are outliers. All, so far as I know, are of the same character 

 as the beds in the like position in the London Basin ; but it 

 would be well for a search to be made for pebbles other than of 

 flint. I can find no record of any in the Memoirs accompanying 

 the maps in question. 



IV. Some other Eocene Pebble-Beds. 



(a) Below the Blackheath Beds. 



It has been inferred that the flint-pebbles of the Blackheath 

 Beds have been derived directly from the Chalk ; but, before 

 we accept that conclusion, it would be well to consider whether 

 there are any older pebble-beds from which they could have come. 



One of the characters of the lowest division of the Lower London 

 Tertiaries, the Thanet Beds, is the absence of pebbles, though, of 

 course, a stray pebble may occur. The flints of its base-bed are 

 either unrolled, or but partly rolled. 



The middle division, the Woolwich and Beading Beds, however, 

 commonly contains layers of pebbles. These occur very generally 

 in the greenish bottom-beds of the southern outcrop in the London 

 Basin, where this bed rests on Thanet Sand ; but, over the far larger 



