GEOLOGY. T 
England and Wales”’ it is attributed to the Middle Glacial Age, 
but there is a passage in Mr. Jukes-Browne’s ‘‘Building of the 
British Isles” which appears to bear on the subject. Quoting the 
late Sir Joseph Prestwich, Mr. Jukes-Browne says: ‘‘He gives 
good reasons for concluding that at the beginning of the newer 
Pliocene Period the central area of the Weald was a plateau rising 
to a height of nearly 3,o00ft. above the sea, and that from its 
watershed streams ran northward and southward. Those which 
ran north swept the debris of the Lower Greensand, Chalk and 
Tertiaries on to the lower ground. It is not unlikely, as Prestwich 
suggests, that these tracts are portions of broad, fan-like, sub- 
aerial deltas, spread out on a plain which then stretched out over 
the Thames Valley.” 
It will be understood that the pebbles from igneous rocks, 
which are found at Shooters Hill, were twice ‘‘derived,” having 
been first transported from the north or west of England, where 
igneous rocks are at the surface, to the Wealden district, and then 
again from the Weald northwards. It is fairly certain that this 
drift has preserved Shooters Hill from the denudation which has 
gone on all around. There is little doubt that the whole of our 
district once had a mantle of at least sooft. of London Clay, and 
when this is borne in mind, the following records from borings will 
show how great, and yet how inequal, has been the denudation: 
New Cross Naval School (Goldsmiths’ Institute) 23 ft. 
Brockley, near the Cemetery... soe Be cia S5 1 4 
Lower eydennen bag oa ven sth eee TQ2. tes 
Beckenham . e oes Bey Pe *RCREE: 
The sea in which the tendon Clay was deposited no doubt 
extended over Kent, Surrey, Sussex, part of Hampshire, Essex, 
Suffolk, part of Norfolk: and over part of the German Ocean, 
British Channel, and north western France. The fossils indicate 
the prevalence of a warm climate at the time. As the clay was 
derived from the decomposition of felspathic rocks, the river or 
rivers which brought it to the London Clay-sea must needs have 
passed through regions where such rocks are exposed. Sir. 
Charles Lyell thought it was a large river which drained a con- 
tinent lying to the west or south-west of Britain. Other geologists 
have thought that the sediment was brought by several rivers 
from land lying to the south. 
As we now take leave of the clays, it will be well to say some- 
thing as to the distinction between brick-earth, a term frequently 
used in ‘‘ superficial” geology, and the Tertiary clays. 
Bricks have for years been made at Loampit Hill and Brockley 
of London Clay and the clays of the Woolwich beds ; hence people 
sometimes speak of such clays as brick-earth. But brick-earth, in 
the language of geology, is a superficial deposit of stiff loam, 
sometimes clayey and sometimes sandy, which has arisen from 
sediment left by the overflowing of rivers. Again, there are in our 
