182 = Reviews—Dr. Penck—Glaciation of the German Alps. 
The third division of the work, on the formation of the Upper 
Bavarian Lakes, commences with a chapter on the changes which 
have taken place in the configuration of the surface of South Bavaria 
and North Tyrol in the Glacial Period. The author estimates that 
the Swabian-Bavarian plateau must have experienced a decided 
elevation of its surface by the enormous amount of transported 
material which has been spread over it by the old glaciers. Thus 
between the Iller and the Inn over a district 150 km. in length from 
south to north, and 60km. in width, Penck estimates that these 
transported materials form a surface layer of 60 metres in thickness. 
To furnish this amount, the northern chain of the Alps must have 
suffered an enormous erosion, equivalent to 36m. in thickness over 
their entire area. Large, however, as is the amount of material 
which the glaciers have abstracted from the Alps and spread over the 
plains in front of them, it would by no means be sufficient to fill up 
the Alpine valleys could it be replaced, and there appears to be clear 
evidence that the entire excavation of the Alpine valleys has not 
been due to glaciers, but is the result of ordinary meteorological 
influences in Pre-Glacial times. The erosion which took place 
during the Glacial Period must have taken place beneath the ice, 
since the entire region would have been covered by permanent snow, 
and therefore protected against destructive sub-aérial influence. 
The Bavarian plateau to the north of the Alps, like most other 
glaciated districts, is characterized by numerous lakes, both large and 
small. These lakes as a rule are not abundant in the valleys among 
the mountains, but are most numerous in the plains immediately in 
front of the exits of the valleys. Well-known examples are the 
Schliersee, Tegernsee, Kochelsee, and Walchensee, which occur in 
the tracks of large valleys which penetrate the northern or calcareous 
chain of the Alps; and the widely extended bogs of Rosenheim, 
Murnau, and Fiissen, are undoubtedly filled-up lakes, which from 
the outlets of the Inn, Loisach and Isar valleys extended far north- 
wards into the plateau. Further to the northwards are the Ammer 
See and the Wurm See, and beyond these in the same direction is a 
zone filled with an astonishing number of small depressions. The 
evidence brought forward shows very clearly that the larger lakes 
have been produced by the erosion of the glaciers at their exit from | 
the mountains. They have been mostly excavated out of the con- 
glomerates (Nagelfluh), and occasionally also out of the soft tertiary 
strata which underlie the conglomerates, and the material excavated 
has been carried onwards and upwards by the glacier and heaped 
up to form the walls of the terminal moraines already mentioned. 
The smaller lakes to the north of the larger are mostly con- 
tained in hollows produced by the unequal deposition of morainic 
material. It is a noteworthy fact that at the outlet of each Alpine 
valley in this area there is either a lake or a filled-up lake-basin. 
These latter are more frequently present in front of the more im- 
portant valleys, owing to the great quantity of material which the 
streams in these valleys are ceaselessly bringing down, whilst in 
front of the smaller valleys the lakes still remain. The character 
