6QS Geological Society. 



nowhere else outside of them ; and in the identity of the fresh- 

 water Chelonia of the two river-systems, the species being either 

 peculiar to these drainage-areas or represented outside of them by 

 distinct varieties. 



April 9th.— Mr. G. W. Laruplugh, F.E.S., President, 

 in the Chair. 



The following communication was read : — 



'The Section at "Worms Heath (Surrey), with Eemarks on 

 Tertiary Pebble-Beds and on Clav-with-Flints.' By William 

 Whitaker, B.A., F.R.S., F.G.S. (With ' Penological Not3s on 

 the Beds at Worms Heath,' bv George MacDonald Davies, 



M.Sc, F.G.S.) 



The chief pit now shows a fine set of more or less vertical pipes 

 in the Chalk, filled with pebbles and sand of the Blackheath Beds, 

 separated from the Chalk by Clay- with- Flints. 



The pebble-beds here, like those elsewhere, consist of well-rolled 

 black flint-pebbles, amongst which pebbles of a brownish quartzite 

 are occasionally found. It is concluded that the water in which 

 these flint-pebbles were formed touched no other firm rock than 

 Chalk ; but, as there are no subangular flints, the deposition of the 

 beds cannot have taken place close along a Chalk coast. 



The great mass of these pebbles is confined to the western part 

 of Kent and the adjoining part of Surrey, and they go but little 

 way underground beneath the London Clay northwards. A few 

 patches of pebbles at the same horizon have been mapped in the 

 Hampshire Basin, but heretofore have not been classed as 

 Blackheath Beds. 



From a consideration of older Tertiary pebble-beds, it seems 

 that these are not big enough to have afforded the material for the 

 Blackheath Beds. On the other hand, the Blackheath Beds nmy 

 have yielded the pebbles of the Bagshot Series in Essex, though 

 not in Hampshire. 



An examination of the various Tertiary pebble-beds (up to the 

 Barton Series) points to overlaps of considerable extent ; so much so 

 that the probable thinning of beds below the Barton Sand, in the 

 London Basin, and its former southward extension is comparable 

 with the underground thinning of the Wealden and Lower Creta- 

 ceous in that area, though smaller and in a contrary direction. 



As to the Clay-with-Flints, it is inferred that it is not a deposit 

 of definite age, out a residual product, representing a condition of 

 things that may have held through long geologic ages, from the 

 start of the Blackheath Beds to the present time. 



Mr. G. M. Davies gives a penological description of the Chalk, 

 of the Clay- with- Flints (both grey and red), of the Eocene sands, 

 sandstones, and pebble-beds. He also describes the presumed 

 allophane originating from the base of the Eocene deposits, and 

 discusses the probable sequence of events which resulted in the 

 formation and infilling of the pipes and the deposition of the strata 

 overlying the Chalk. 



