REVIEWS 381 
gravel deposits are known as the ‘‘Aeltere Deckenschotter, Jungere Deck- 
enschotter, Hochterrassen, and Niederterrassen,”’ while the corresponding 
drift sheets are named ‘‘Gunz, Mindel, Riss, and Wiirm,” the names being 
taken from type localities in the Alpine foreland. The relative ages of the 
deposits of each glaciation are determined by a study of the relative amounts 
of geologic work accomplished by erosion, sedimentation, and weathering 
since their deposition. The first two glaciations are found to be much more 
remote than the last two, and form what are called the older group, while 
the Riss and Wiirm form the younger group, yet the alteration of the Riss 
is sufficient to indicate that it is more than twice as old as the Wiirm. The 
classification here made was found to hold good throughout the entire Alpine 
field, and as a result of the wider study the relative ages of the several 
glaciations, as summed up in the concluding Lieferung, place the Riss 
three times as far back as the Wiirm, and the Mindel at least twelve times 
as far back as the Wiirm, while the Gunz is considered about one and 
one-half times as old as the Mindel, the data for estimating its age being 
rather imperfect. In this first volume Penck brings out clearly the minor 
oscillations shown in the last or Wiirm glaciation. To each readvance 
made by the ice he applies the term stadium and recognizes three that lie 
between the maximum limits of the Wiirm glaciation and the limits of the 
present glaciation, namely the Biihlstadium, Gschnitzstadium, and Daun- 
stadium. These stadia are found to be capable of differentiation in many 
other parts of the Alps. This first volume also discusses briefly the inter- 
glacial deposits and the difficulties of their interpretation. It is the custom 
of these authors to class deposits as interstadial rather than interglacial 
except in places where the evidence is very clear that they were laid down 
in a much warmer climate than would be consistent with a glacial stage. 
Where, for instance, warm-climate plants are found to be imbedded in the 
deposit, as in the Hétting breccia near Innsbruck, the deposits are referred 
confidently to an interglacial time. 
While the first volume is entirely from the pen of Penck, it should be 
stated in justice to the work done by Briickner, that the results of his studies 
in the Salzach district, which appeared in 1886 in the form of a monograph 
are here abstracted by Penck. 
In the second volume which deals with the glaciation north of the west- 
ern Alps, Briickner discusses the glaciers of Switzerland, while Penck 
discusses the Rhein glacier and the portion of the Rhone glacier in France 
and the Isére glacier. Penck also discusses the Quaternary fauna and 
Paleolithic man in the Rhodanischen district and on the north side of the 
Alps. The four glacial stages brought out in the first volume are clearly 
