LAMPLUGH : SHELLY MORAINE OF THE SEFSTROM GLACIER. 241 
are of the scanty arctic type ; but under similar circumstances 
at lower latitudes, as for example, in Alaska and Patagonia, a 
dense covering of vegetation is found close up to the ice-margins. 
It is likely that throughout the Glacial period any part of our 
Islands that was permanently, or even temporarily, bare of ice 
would be tenanted by plants and animals in a similar manner. 
There is much probability that the Pleistocene fauna of Britain 
was adapted to such conditions, and was in part contempor- 
aneous Math the waxing and waning ice-sheets. 
(6) The local piling up of a mass of boulder-clay, to a thickness 
of 100 feet or more, by the Sefstrom glacier during its brief invasion 
of Cora Island, an invasion lasting certainly less than 10 years 
and prol^ably not more than 4 or 5 years, shows how rapidly the 
glacial deposits may sometimes be accumulated. The conditions 
in this case were comparable to those of our Eastern lowlands. 
It is e\ddent from this that no safe conclusion as to the duration 
of glaciation can be deduced from the thickness of the boulder - 
clay at any particular spot. We know from other evidence that 
the glaciation of our Islands was a slow and very lengthy process ; 
but it may nevertheless have happened that some of our thickest 
drifts in the marginal areas were accumulated during a particular 
phase of very short duration. The greatest amount of drift is 
deposited near the limits reached by the ice ; consequently, the 
thickness of the glacial deposits must often be in inverse ratio to 
the time-factor of glaciation. 
Note. — For the photographs reproduced in illustration of this paper, I am 
indebted to Prof. G. De Geer, Dr. A. Strahan. F.R.S., and Prof. R. S. Tarr, 
who have kindly consented to this use of them. I have further to thank 
Prof. De Geer for permission to reproduce liis map of the Sefstrom Glacier, 
and for the list of shells and much other information and ad\ ice ; and 
Dr. Strahan for ^vriting the description of the conditions around the 
glacier-remnant on Cora Island. 
