HT. H. Howorth—A Great Post-Glacial Flood. 413 
been said, I venture to think, to reveal the true cause of the green 
colouration which is so prevalent in. the Middle and Lower Bagshot 
Sands, and to show that a pure wholesome potable water is hardly 
obtainable from them without an extensive process of oxidation, 
which in time converts into water and carbonic acid all the soluble 
vegetable compounds, which are extracted from these sands by water. 
V.—T races or A Great Post-Guactat FLoop. 
Part 6. Tue Evipence or THE RoLLtED GRAVELS AND THE SANDS. 
By Henry H. Howorrn, F.S.A. 
(Continued from p. 368.) 
ET us move on again. The rolled gravels of Central and 
Southern England are divisible into two well-marked varieties, 
which were well discriminated, as Professor Phillips says, as long 
ago as 1815 by Dr. Kidd, and separated by him into a hill group 
and a valley group. 
The former of these is the gravel we have just described, which 
has been largely transported, and contains a large number of foreign 
pebbles. The other gravel is of local origin and its materials, so far 
as we know, have not been derived or transported very far. The two 
gravels are otherwise distinguished in the main by another feature; 
while the former set are barren, the latter contain the débris of a 
land fauna in many places in large quantities, whence they have 
been called ossiferous gravels. Although these gravels are thus 
differenced, -it seems most clear to me that their distribution as 
they are now found was contemporaneous, and that both were 
spread out, although not to the same extent, by the same potent 
cause. This seems to follow from two facts. In the first place 
they run into one another and dovetail together, passing in places 
from the one type to the other, as has been shown by Professor 
Phillips in the Thames Valley, and by others elsewhere ; secondly, 
the same débris of a land fauna which characterize the local gravels 
are found also in certain localities where the two are in close con- 
tiguity in the transported gravels. 
Phillips, who uses the term diluvium for the transported gravel, 
said long ago, “On the eastern side of the island, from the Tyne to 
the Humber, the gravelly deposits appear partly of local and partly 
of distant origin. On the Yorkshire coast, local gravel derived from 
the chalk wolds or oolitic moors, lies in very irregular beds, distinct 
altogether from the clays full of pebbles brought from the Cumbrian 
and Pennine mountains; at Bridlington local chalk and flint gravels 
lie over the other diluvium, and at Hessle, on the Humber, similar 
gravel lies under it. .... It is not solely, nor perhaps even prin- 
cipally, in this proper diluvium (i.e. the transported gravel) that the 
bones of elephants, hippopotami, horses, deer, etc., occur; they seem 
on the contrary to be rather more plentiful in the local gravel 
deposits. Cases, however, occur, as at Brandsburton, and at Middle- 
ton-on-the-Wolds, near Beverley, of elephantine and other remains 
