32 Rk. M. Deeley—The Glacial Succession. 
Geikie’s correlation of the Scottish deposits with those of England 
and Wales, for it was not necessary for his purpose to give us any 
facts, other than such as relate to the distribution of the Boulder- 
clays, so we cannot with certainty decide as to which English 
deposits he is sometimes referring. Still, from the localities he 
mentions, I judge that the “lower or oldest” Boulder-clay which 
“has the widest extension southwards, for it has been traced as far 
as the valley of the Thames,” must be the Chalky Boulder-clay— 
that is one of my Middle Pleistocene deposits. This view is 
supported by his statement that ‘‘ The Upper Boulder-clay, on the 
other hand, does not extend south of the Midlands of England.” 
He here seems to refer to the Purple pe which is possibly 
of Newer Pleistocene age. 
On p. 146 of his paper Prof. Geikie summarises in the form of an 
excellent table the succession he has adopted for Europe. This 
table I have somewhat abridged and placed alongside my own classi- 
fication in such a way as to show their points of agreement and 
disagreement. 
In this table he groups all the English Boulder-clays older than, 
and I suppose including, the Chalky Boulder-clay in his third group, 
or epoch of maximum glaciation. But there is yet an older glacial 
group mentioned, of the age of the Weybourn Crag, during which the 
ground moraine of the great Baltic glacier, underlying the ‘‘ Lower 
diluvium”’ of Germany, is supposed to have been formed. Can 
this epoch be the equivalent of my Older Pleistocene epoch? Un- 
fortunately the Boulder-clays and sands of this epoch occurring in the 
Trent Basin have not been traced into Hast Anglia. Their relation- 
ships with the Contorted Drift, White Sand, and Cromer Tills of 
Norfolk are therefore unknown, and it is impossible to say with 
certainty whether the Harly and Middle Pennine Boulder-clays, and 
the Quartzose Sand are any of them as old as the Weybourn Crag, 
but what evidence there is seems entirely against such a supposition. 
We must, therefore, regard the deposits of Prof. Geikie’s third 
group as belonging partly to my Middle Pleistocene and partly to 
my Older Pleistocene epoch, and regard such an early deposit as the 
Weybourn Crag as not being represented in the Trent Basin, but 
marking the commencement of the Older Pleistocene epoch. 
From Professor Geikie’s table it seems that he regards climatic 
changes as furnishing the most satisfactory basis for the classification 
of Pleistocene deposits ; physical changes, such as have occurred in 
the distribution of land and water, not being made use of for this 
purpose. In fact the succession simply changes alternately from 
Glacial to Interglacial. Possibly this method of classifying the 
deposits may prove to be the best in the long run, although it is 
in striking contrast to that adopted for the older rocks. However 
this may be, in studying the deposits of the Trent Basin, it was 
found most convenient to base the divisions chiefly upon physical 
considerations, such as the abnormal condition of ice-flow which 
obtained at one time in the Midlands of England; an ice-flow which 
brought into the Trent Basin an assemblage of rock fragments quite 
