Reviews—Dr. Penck—Glaciation of the German Alps. 181 
to be more than double as great as that of merely running water. 
The moraines at the terminal ends of the glaciers do not by any 
means indicate the total amount of their erosive action, for the 
enormous beds of sand, gravel, and clay, extending far beyond the 
bounds of the morainic districts, are merely the results of the streams 
issuing from the glaciers upon the material which the glacier itself 
has transported, and thus should be considered as the products of 
glacial erosion. 
In the second division of the book, the author discusses the ques- 
tion of the recurrence of different periods of glaciation in Upper 
Bavaria and the Tyrol, and from observations on the relations of 
different morainic deposits, he concludes that there is evidence for at 
least three distinct glaciations during the Glacial period. Thus, for 
example, near Innsbruck, on the left slope of the Inn Vailey, there are 
well-marked beds of red and white breccia, with traces of plant- 
remains, which have caused them to be referred to Miocene age. 
But Penck discovered that this breccia is overlaid by the morainic 
materials of the last glaciation, whilst the breccia itself overlies a 
distinct ground moraine with crystalline erratic materials, showing 
a glaciation of the valley previous to the formation of the breccia by 
mountain streams. These facts cannot be explained by the mere 
oscillations of one and the same glacier, for the plants preserved in the 
breccia at 1000 m. S. L. clearly indicate that the ice must have retired 
from this level for these heights to have been covered with vegetation. 
Another fact discovered by the author is the presence of thin 
beds of coal inclosed in conglomerates 30 to 40m. in thickness on 
the slopes of the valley of the Iller near Sonthofen, at an elevation 
of 940m. above the sea. This coal-bearing conglomerate is both 
overlaid by moraines and rests upon moraines. ‘The course of events 
indicated by these deposits is thus stated by Penck :— 
1. The valley is filled with glaciers, which near Sonthofen descend 
to a level of 900m. 8.L. Temperature low. 
2. The glaciers have retreated. Masses of gravel up to 60m. in 
thickness are formed. LHlevation of temperature. j 
3. Vegetation spreads over the surfaces of gravel, and accumulates 
sufficiently to form beds of coal reaching to over 3m. in thickness, 
indicating an extended period of time. These coal-beds are covered 
by gravel. 
4. The Iller Valley is excavated to a depth of 210 to 220m. 
Temperature continuing higher. 
5. For the second time the glacier covers the district. The tem- 
perature falls. 
Penck also refers at length to the older conglomerates, or “ dilu- 
viale Nagelfluh,” so extensively developed near Munich and in the 
country between the Iller and the Lech, northwards to the Danube. 
These deposits of water-worn gravels show by their contents that 
only ice transport could have brought many of the fragments into 
the districts where they have been rolled and arranged by water, and 
now the upper surfaces of these consolidated gravels show the 
striations of the last glaciation, and are covered by its moraines. 
