Salisbury. 307 
Drift of the North German Lowland. 
and filled it. As it advanced to the southward, it rose from the 
basin of the Baltic onto the higher land to the south, carrying 
with it much material which it had scooped out of the basin, and 
especially, much that it gathered from the southern slope of the 
same, during its ascent to the land beyond. As the ice pushed 
out upon the land with its great load of debris thus acquired, its 
velocity was diminished. Where the greatest retardation took 
place, there would be the most extensive accumulation of glacial 
debris (p. 102). The site of this retardation and consequent ex- 
tensive accumulation is marked, according to Dr. Wahnschatfe, by 
the Baltic ridge, which indeed owes its existence largely to the 
accumulation of drift brought about in this way. The ‘ground 
moraine landscape” is associated with the ridge, and is, according 
to Dr. Wahnschaffe, the result of this peculiar method of drift 
accumulation, for where the drift accumulation was greatest, there 
would it be piled up in rough topographic forms. The author sees 
no insuperable difficulty in believing that this sort of topography-, 
developed beneath the advancing ice sheet, could be subsequently 
overridden by the further advance of the ice, without being de- 
stroyed. 
From: Dr. Wahnschatfe’s view concerning the origin of the 
‘knob and basin” topography of the Baltic ridge, we are com- 
pelled to dissent. According to his view the last ice sheet ad- 
vanced far beyond the Baltic ridge, at least as far as Magdeburg. 
If this opinion be correct, the Baltic ridge must have been buried 
under a very great depth of ice. The Baltic ridge is a very con- 
spicuous ridge. In many places its topography is very rough—of 
the pronounced knob and basin type. To suppose that glacier 
ice buried and overrode such a ridge with such a topography to 
such a depth as must have been if the ice advanced so far south 
as Magdeburg, is to attribute to the ice a degree of plasticity 
which we are not prepared to admit. It seems to the writer that 
Dr. Wahnschatfe’s position practically denies to glacier ice much 
power of erosion, even when overriding to great depth the rough 
surface of a conspicuous ridge, composed of loose sand, gravel, 
and till, while it attributes to the same ice extraordinary power of 
erosion in passing through the Baltic basin, a little further north. 
The depth of the ice in the basin was of course greater than that 
of the ice which passed over the ridge, and in its erosive action 
in the basin it possessed whatever advantage comes from increased, 
