306 The American Geologist. May, 1882 
commonly believed to have contributed to its development, most 
of the German geologists appear to give a prominent place to ice- 
pressure, which is conceived to have bulged up drift material at 
the edge of the ice, producing hummocks and short, discontinuous 
folds. Dr. Keilhack places the development of the ‘ground 
moraine landscape’ topography under consideration, beneath the 
oscillating margin of the ice, at the time when this margin stood 
along the line of the Baltic ridge, during the last glaciation. He 
ascribes it to the unequal accumulations of drift beneath the mar- 
gin of the ice, and to the irregular bulging of the drift, effected 
by the pressure of the ice. Similar topography north of the Bal- 
tic ridge, is believed to have been produced in the same manner, 
at a later time, when the edge of the ice had receded to the posi- 
tion where such topography occurs. Schroeder is quoted as ad- 
vocating the view that the peculiar topography here described was 
developed beneath the ice during the time of its slow retreat (p. 98) ; 
but whether beneath the margin of the ice, or remote from it, or 
whether the peculiar topography is the result of unequal accumu- 
lation or of ice-pressure, is not indicated. 
Dr. Wahnschaffe believes that the ‘‘ground moraine landscape’ 
was developed beneath the ice during its advance in the later ice 
epoch, and that the topography thus developed was not materially 
altered during the final retreat of the ice over the same region 
(p. 100), although the ice edge remained stationary on the ridge 
for some considerable period during its retreat. It is to be borne 
in mind that the topography here described is best developed 
along the ‘Baltic ridge,” which is in a general way concentric 
with the shore of the Baltic. | Dr. Wahnschaffe sees much sig- 
nificance in this position. He points out the fact that this sort 
of topography stands in a similar relation to great basins in vari- 
ous other parts of the world. In northern Italy, ridge-like belts 
of drift with a similar topography, border the Italian lakes on the 
south. In the Bavarian Alps similar ridges of drift rise higher 
than the basins enclosed within them. More conspicuous exam- 
ples of the same relationship in America are referred to, where 
thickened belts of drift (our terminal moraines) exist, in a general 
way concentric with the Great Lakes of the interior. 
Dr. Wahnschaffe’s conception of the relation of the Baltic 
ridge to the Baltic sea, is something as follows: The ice starting 
from the Scandinavian mountains descended into the Baltic basin 
