236 
Notes on the London Clay and Bagshot Beds. 
south-west, some remnants of pebble-beds remain,—the 
pebbles enclosed in a bright reddish sand,—a specimen of 
which is exhibited. These are probably remains of the 
pebble-beds. At Tbeydon Mount and Brentwood the beds 
are very similar. They are best exposed at the latter place, 
where they have been extensively worked. The Bagshot 
Beds in this part of Essex unfortunately appear to be entirely 
unfossiliferous. The sandy beds of the London Clay at Oak- 
bill Quarry have some traces of organic remains, but I have 
not been fortunate enough to find any fossils. The upper 
part of the dark clay is said to contain sharks’ teeth and 
shells, but I have seen none. I have mentioned septaria 
being found there, and these are also constant at Tbeydon 
Mount and Brentwood; 8 and from Tbeydon Mount I exhibit 
two sharks’ teeth, lent me by W. Bonner, of the brickfield 
there, £ mile north of Hill Hall. 
In conclusion, the section at Oakbill illustrates the great 
denudation which lias taken place in the river-valleys of this 
neighbourhood; it shows the conformity of the beds of the 
London Clay and Bagshot Sands, the latter strata being 
evidently of the same formation as the Clays, revealing the 
history of the beds, the deposition of which commenced in a 
deep sea during a period of depression, and continued possibly 
during a period of elevation. It shows, at all events, after 
the deposition in deep water, a gradual shallowing until the 
shore deposits, becoming more and more sandy, at last ended 
in pure sand and pebbles ; and these patches of sand and 
pebbles on the highest grounds show the greatly extended 
area formerly covered by the Bagshot Beds, of which these 
isolated outliers once formed part. The dip of the beds has 
yet to be ascertained, and when this is found there still 
remains to be verified Mr. Searles Wood’s statement that 
there are faults on the western sides of the hills. Until this 
is accurately decided the actual thickness of the London Clay 
at High Beach cannot he given ; it may he nearer 600 than 
400 feet, but if so, it is exceptionally thick. The denuding 
power of aqueous and atmospheric agencies over a soft 
stratum like the London Clay is well illustrated by the 
section, as well as to the amount of elevation which took 
place subsequent to the deposition of the Clay. In con¬ 
clusion, I must thank one of our members, Mr. E. Heatlifield, 
for assisting me in measuring and examining the beds at the 
quarry. 
8 The specimen of septaria exhibited from Brentwood was remarkable 
for its nucleus. 
