PLASTIC CLAY FORMATION. ^65 



immediately above the chalk; although organic remains have been noticed 

 in it only at Heading*." 



Between Castle Hill and Seaford, a flat alluvial tract intervenes, 

 through wliich the Ouse flows into the British Channel. To the east of 

 this marshy plain, the perpendicular slopes in which the Downs terminate, 

 are covered with a cap of fawn coloured and greenish sand, with rolled 

 blocks of chalk, and flint pebbles. An excavation on the side of the hill, 

 near the road leading from Newhaven to Seaford, exhibits a good section 

 of these deposits. The rolled pebbles and sand, occupy about fifteen feet 

 of the upper part of the bank, and he in a hollow or basin of chalk 

 rubble; and wherever the chalk is accessible to observation along this 

 margin of the Downs, it is invariably in a broken and ruinous state. 



At Chimting Castle, about half a mile to the east of Seaford, the upper 

 part of the cliffs is composed of a bed of sand, about fifty feet thick. 

 Here a stratum of the ferruginous breccia, previously mentioned, is seen 

 in situ, lying beneath the sand, and immediately upon the chalk. The 

 sand is of a fawn colour, passing into olive green ; it contains numerous 

 irregular veins, and concretions of mammillated ironstone. The pudding- 

 stone, or breccia, is precisely similar to that of Castle Hill, with which, 

 there can be no doubt, it was once continuous. The flints that compose 

 it, present the same characters ; some being rolled, others angular, and 

 all of them either of a dark green or yellow colour externally. The bed 

 of breccia, in some places, is nearly four feet thick. These deposits 

 extend eastward about half a mile, and disappear near the Signal House ; 

 they dip to the west at an angle of from 10° to 20°. 



Eastward of this place, the chalk has only a covering of ochraceous 

 clay, and vegetable mould, and, with the exception of the blocks of breccia 

 at Brighton, &c. previously alluded to, and a few insular patches of olive 

 green sand in hollows of the chalk at Piddinghoe, I am not aware of the 

 existence of any other decided examples of the Plastic clay, in the south- 

 eastern part of Sussex. 



In the western division of the county, Professor Buckland observed a 



* Professor Buckland on the Plastic Clay, Geolog. Trans. Vol. iv. 



M M 



