448 
huge masses of clialk, as well as by floods resulting from the 
breaking up of the ice-fields. To whatever agent, however, 
particular deposits may bo due, it is hazardous to attempt to be 
precise in our explanations. All we can do is to picture the great 
glaciation of the country, and to endeavour to give various icy 
agents credit for portions of the work, just as ice-sheets, icebergs, 
and coast-ice may now act, if not in concert, within no great 
distance one from the other, so that the several forces might come 
into play over the same tract in the course of no great extent 
of time. 
I have said nothing of man’s advent during this cold period, but 
there is no doubt that he was in existence in southern Europe ; 
and if, as seems probable, he was tempted or forced to make arctic 
expeditions in those days, we have the evidence of the interglacial 
brickearth at Brandon to countenance our view."^‘ 
It can, however, be asserted with confidence, that after the last 
glaciation of hforfolk, and whilst glaciers still lingered on the 
highlands of North Britain, the conditions became suitable for 
inciu’sions of the arctic mammalia, the Lemming, the Beindeer, 
the Woolly Elephant, and Bhinoceros, and also of the Hyaena, 
lliljpopotamus, and Lion. Man, too, made his appearance ; for bis 
ancient and rudely-chipped stone implements are found in the 
older valley-deposits of the Thames, and in several localities in 
West Norfolk near Thetford and Brandon. 
Most of our minor features commence to date from this time ; 
for the dei)Osits of the Glacial period formed an extensive 
plain, out of which our present rivers have shaped their courses. 
If we are right in considering that the latest Glacial deposits in 
Norfolk were formed on laud by an ice-sheet, and by the floods 
that resulted from its melting away, then our tract of land may 
not have been submerged since. Be this as it may, the climate 
gradually ameliorated, heavy rains and torrents probably ensued, 
and the wearing away of the river valleys may have proceeded at 
a greater rate than at present. Eventually a good deal of the West 
of England and North Wales Avas submerged to a considerable 
* Professor W. Boyd Dawkins now thinks that the palrcolithic implements 
of the Thames Valley brickearth at Erith and Crayford are quite as likely to 
he pre-glacial as post-glacial (Address to Department of Anthropology, 
British Association, 1882). 
