Reviews—Dr. Penck—Glaciation of the German Alps. 179 
the Inn is the Seefelder pass, 1200 m. 8. L. and 600m. above the 
Inn. The pass was one of the main channels through which the 
masses of ice from the heart of the Alps streamed northwards, carry- 
ing the crystalline rocks across the Inn Valley, and leaving them 
strewn over the sides of the pass to a height of 5000 feet. This icy 
stream extended down the valleys of the Ammer, Loisach, Kochel- 
see and Isar, and reached to the Bavarian plateau. It filled up the 
valleys in the passes to a height of 1580 m., and only the highest 
peaks and crests of the northern limestone-range projected above its 
surface. Still lower down the Inn is the pass of the Achensee, only 
400 m. above the Inn Valley. Though this lake has no rocky walls 
between it and the Inn, and is but a distance of 4 km. from it, yet 
it has its outlet to the north. The erratics in this pass show that a 
small branch of the Inn glacier must have flowed through it to con- 
nect with the Isar glacier. The most important glacier stream, 
however, which reached into the North Alpine plateau, is that which 
flowed down the Inn Valley itself. Still further westwards of the 
Inn, the valleys of the Iller and the Lech were also filled with 
enormous glaciers. 
As the individual glaciers debouched from the mountain passes in 
which they had been confined, they widened out on the plateau to 
the north, and joined together so as to form a sea of ice, which can 
be traced along the base of the Alps from Lyons to the Inn. The 
Swiss glaciers were dammed in by the Jura; but the glaciers which 
poured over the Bavarian high-level plateau had no barrier to hinder 
their progress northwards, and their former limits can be clearly 
traced by the ground moraines which they have left. This boundary 
in the Swabian-Bavarian plateau follows a wavy line with four very 
distinct northerly prolongations: the most westerly encircles the 
Rhine Valley, the next eastwards is north of the Lech, the third is 
morth of the exit of the Loisach Valley, through which the main 
portion of the Isar glacier streamed out of the mountains, and the 
fourth and most easterly extension reaches its maximum north of 
the exit of the Inn. The author observes that the development of 
glaciers on the north slopes of the Alps decreases from west to 
east, notwithstanding the fact that the district supplying the glaciers 
is more extended and also higher in the east than at the west, and 
the same law prevailed in the glacial period as at the present time. 
This result is probably owing to different temperatures and varia- 
tions of the snow-fall in different divisions of the Alps. 
‘That portion of the Bavarian plateau over which the ancient 
glaciers extended is distinguished by its covering of morainic 
material, but the chief part of the morainic deposits is situated in 
the peripheral margin of the district, and form the terminal moraines 
which in Upper Bavaria appear as elongated chains of hills from 20 
to 30 métres in height, whose longitudinal axes run parallel to the 
outermost margins of the glaciers, and mark their former borders. The 
composition of some of these terminal moraines is almost identical 
with the clay and scratched stones of a typical ground moraine, 
whilst others are composed almost exclusively of bedded clays and 
