° REVIEWS 825 
bend of the latter, southeast of Glogau. From this point west the 
edge of the ice was south of the Oder, having a general west- 
northwest course to Magdeburg. West of Magdeburg the position of 
the edge of the ice has not been determined. It was perhaps along the 
Aller River, and perhaps farther north along the divide between this 
river and the Elbe. During this stage of the ice marginal drainage 
was westward along the valley of the Malapane to the junction of that 
stream with the Oder at Oppeln, thence down the Oder to Breslau and 
beyond. Here the drainage left the present course of the Oder 
(which beyond this point was buried by the ice) and flowed west- 
northwest to the valley of the schwarze Elster, thence along that 
valley to the Elbe, and down the Elbe to its junction with the 
Saale. 
The halting places of the ice during its retreat are recognized by 
three principal criteria. First, the exd@mordne, which are bowlder walls 
(as that term is used by the Germans); second, the great ridge-belts of 
markedly undulatory topography regarded as terminal moraines in the 
United States; and third, the sand and gravel plains outside the ridges 
just referred to. All these criteria are found in connection with the 
edge of the ice at its various stages, but in better development in some 
cases than in others. 
The edge of the ice during the first recognized halt in its retreat 
lay afew miles farther north, running in the same general direction. 
Roughly, it extended from Pleschen to Potsdam, and thence to a 
point near Lauenburg just north of the Elbe. West of Lauenburg the 
border has not been traced. The margin of the ice during this halt 
was more or less lobate. The marginal drainage was along the Bartsch- 
Baruth Valley to the Elbe north of Magdeburg. Farther west the 
course of the drainage is uncertain. 
The second halt of the ice, marking the third position of a more or 
less stationary edge, lies still farther north, along the divide between 
the Warthe and the Netze from longitude 36° E. to Frankfurt on the 
Oder. Here the edge of the ice crossed the present course of the 
Oder, and extended westward and northwestward to Schwerin and 
beyond. During this stage the marginal drainage was westward along 
the course of the Warthe to the longitude of Posen, thence westward 
to the Oder and down the latter nearly to Frankfurt, thence westward 
by way of the Spree to Berlin, and thence west-northwest to the Elbe, 
and thence to the North Sea. 
