14 Proceedings of the Royal Society of Edinburgh. [Sess. 
Epoch. The outwash gravels are cemented and weathered, but the pebbles 
are not so highly decomposed as those in the Older Deckenschotter. 
The deposits of the Mindel-Riss or Second Interglacial Epoch separate 
the older from the younger drifts of the Alps. According to Penck and 
Brlickner it was probably the longest of the interglacial periods in the 
Alpine region, and was characterised by a warmer climate than the present. 
The well-known Hotting Breccia near Innsbruck in the Tyrol has been 
latterly referred by Penck to this stage, though he formerly assigned it to 
the Third Interglacial Period. The plants contained in it furnish important 
evidence regarding climatic change. Forty-two species of plants have 
been identified, four of which are new. Thirty species still survive in the 
neighbourhood. Three species are of special importance — a rhododendron 
(. R . ponticum), now living in the Caucasus in a climate about 3° C. warmer ; 
a buckthorn ( Rhamnus hoettingensis), related to R. latifolia from the 
Canaries; and the box (. Buxus sempervirens), a southern species. From 
the evidence Penck infers that the Hotting flora indicates a climate 
2° C. warmer than now, when the Alps were comparatively free of ice 
and snow. 
The morainic material and high terrace gravels accumulated during 
the Third or Rissian Glacial Epoch are not weathered and cemented to 
the same extent as the older glacial deposits. The detailed mapping of 
the glacial drifts has shown that, in Switzerland, France, and in the 
Po districts, the Riss glaciation exceeded that of the preceding Mindelian 
period, while in the valleys of the Inn, the Salzach, and the Iller, the 
reverse was the case. In order to account for this distribution of the 
glaciers, Penck has suggested that differential crustal movements may 
have produced a greater depression of the snowline in the northern part 
of the Eastern Alps. 
The Riss-Wtirm or Third Interglacial Period is proved bj^ the occurrence 
of interglacial deposits yielding evidence bearing on climatic change. Of 
these, reference may be made to the lignite or brown coal of Dtirnten and 
Unter-Wetzikon. At both localities they are overlain by the moraine 
of the Fourth Glacial Epoch, and are underlain by glacial accumulations. 
Eighteen species of plants have been found at Dtirnten, comprising, among 
others, the yew, the Swiss fir, white birch, sycamore, hazel, and water lily. 
The presence of the yew indicates that the climate at this stage must have 
been warmer than that now prevailing in the same region. The mammalian 
remains found at Dtirnten tend to support this conclusion. These include 
Elephas antiquus, Rhinoceros merckii, Bos primigenius, and Gervus 
elephas. 
