278 R. Chambers, Esq., on Glacial Phenomena 



from the neighbouring chain. 1 ' Contains scratched 

 fragments, but these supposed to be local. Frag- 

 ments of shells. 



1. Sand, a deep bed, with erratic detritus. 



At Weymouth, according to Sir Henry de la Beche,* the 

 rocks, inclusive of the chalk, have been subjected to great 

 disturbance, producing enormous faults ; but the surface has 

 subsequently been exposed to " a tremendous inundation, 

 which has swept away all the rubbish and ruins of the ele- 

 vated masses, and has excavated valleys of many hundred 

 feet in depth on the surface of the strata that remain. Out- 

 lying summits composed of residuary portions of the strata 

 which are continuous along the escarpments on the north 

 and east of the valley of Bredy, indicate the original conti- 

 nuity of these strata over large portions of that district from 

 which they have been removed.'' 



In the district of Chatham and Rochester, according to Mr 

 R. Dadd,t there is the following series of deposits above the 

 upper chalk : 



4. Alluvium. 



3. Diluvium : from 6 to 10 feet thick ; water-worn chalk, 

 with unworn flints. Remains of deer, elephant, rhino- 

 ceros, &c. 



2. London clay. 



1. Plastic clay. Shells of ostrea, cyclas, and cerithium. 



Amidst the obscurities produced by the want of a uniform 

 nomenclature, it is easy to see that the till, diluvium, and 

 northern drift are all one formation, identical with the till 

 or second boulder clay of Scotland. In the Silurian region 

 there is a lower drift, marked, like the lower or true boulder 

 clay of Scotland, by the comparatively local character of the 

 detritus, and which may be presumed to be contemporary 

 with that formation. Over the till or northern drift, again, 

 there are other deposits of a tranquil ocean, as in Scotland. 

 There are also, as in Scotland, about this part of the series, 

 remains of land vegetation. Subsequently come large un- 



* Geol. Proceedings, i., 220. t Ibid., i., 482. 



