GTBB OYSTER CONGLOMERATE BED AT BROMLEY. 335 
interesting localities he was acquainted with. At and around Bromley 
is an area of some extent, formed by the Lower London Tertiaries ; a 
small patch of chalk, however, crops out to the east of the town, in 
which are some ancient quarries. One of these possesses some interest 
from being underground, and containing, as I was informed, several 
intricate windings. 
The London clay, with the underlying plastic or "Woolwich clays, and 
Thanet sands, constitute the lower division of the Eocene strata of the 
Tertiary group of rocks. The London clay extends over several counties 
of England, constituting a large part of the soil of Essex, nearly the 
whole of Middlesex, and portions of Berkshire, Surrey, and Kent.* In 
the last two counties it more especially occupies the northern parts. The 
plastic or mottled clays and sands which underlie the London clay are 
seen in the Isle of "Wight in contact with the chalk, or in the London 
basin at Reading, at Blackheath, "Woolwich, and Bromley. These clays 
and sands have been well described by Mr. Prestwich, and termed by 
him the " "Woolwich and Reading Series," and the Thanet sands of the 
Lower London Tertiaries. However much the other divisions of the 
Eocene strata may have differed in their mineral character in the 
deposits of England and Paris, Sir Charles LycU has well observed that 
there is an exception to the general rule in the plastic and mottled claj's 
of this lower division of the Eocene series ; for whether it is studied in 
the basins of London, Hampshire, or Paris, we recognise everywhere 
the same mineral character. " This uniformity of aspect must be seen 
in order to be fully appreciated, since the beds consist simply of sand, 
mottled clays, and well-rolled flint pebbles derived from the chalk, and 
varying in size from that of a pea to an egg."f 
These characters are presented by an examination of the oyster-bed 
near Bromley, which consists of a series of thin layers of sand and 
pebbles, and an extensive deposit of oyster and other shells. In some 
parts the latter have formed with the pebbles and sand a distinct con- 
glomerate, several inches thick, the cementing medium being calcareous, 
and apparently derived from the shells themselves. This conglomerate 
has been extensively quarried at one time, and even now many of the 
houses, grottos, and garden-walls in Bromley are built with the rock 
thus ornamented with the shells, which are so naturally grouped 
* Geology of England and Wales, by Conjbeareand Phillips, 
t " Manual of Elementary Geology," p. 221. Fifth Edition. 
