466 DR. PRELLER ON PLIOCENE CONGLOMERATES [ Aug. 1902, 
(3) Even if the lowering of the Pliocene valley-floor near Zurich 
and Lausanne by about 400 metres had been solely effected by the 
agency of fluviatile erosion, denudation, and wastage, there would 
be nothing extraordinary in such a phenomenon, when it is 
considered that the Miocene material to be removed in the course 
of the two inter-Glacial Periods, of which the first at least is now 
commonly recognized to have been of very long duration, was, in 
the main, soft Molasse, clay, and gravel. Moreover, the apparently 
considerable depth of 400 metres represents barely one-twentieth of 
the width of the two, even now essentially shallow valleys ; while 
other valleys, as for example that of the Rhine near Bregenz, of 
the Aare near Berne, of the Reuss in its lower course, and of the 
Inn near Innsbruck, are all of about similar depth and width, and 
therefore give similar cross-sections :— 
Mean Approx. Cross- Mean flow 
width. Depth. Section. per second, 
Kilo- Square Cubic 
metres. Metres. metres. metres. 
Rhine Valley, near Bregenz ... 13°5 400 5,400,000 250 
Aare Valley, near Berne ...... 85 400 3,400,000 200 
Reuss Valley, near Muri ...... 70 400 2,800,000 150 
Inn Valley, near Innsbruck ... 4-0 400 1,600,000 160 
Limmat Valley, near Zurich ... 5D 400 2,200,000 100 
Rhone Valley, near Geneya ... 6:0 400 2,400,000 270 
(4) With reference to the altitude of 800 metres of the Pliocene 
Subalpine plateaux at Zurich and Lausanne, it may be asked, how 
does that elevation correspond with the then valley-floors in the 
Alps proper? And further, would not a subsequent zonal subsidence 
along the edge ot the Alps of 400 metres (or 1300 feet) raise the 
mean temperature, whereas the Pleistocene glaciations require a 
,owering of the same ? 
The answer to the first question would be that, given the altitude 
of the Plocene Subalpine plateaux as stated, that is, 400 metres 
above the present Lakes of Zurich and Geneva, the fjord-like Alpine 
valleys of the Rhine and the Linth (say at Sargans, Chur, and Glarus) 
and of the Rhone (say at Martigny and Sion) must of necessity have 
been correspondingly, that is, at least 400 metres, higher than at 
present. As regards Northern Switzerland, this is confirmed by the 
significant fact that certain characteristic rocks of the older Alpine 
series, such as Julier and Puntaiglas granite of the Rhine drainage- 
area, and more especially the well-known Sernifite or red sandstone 
of the Glarner Alps or Linth watershed, are entirely absent in the 
Miocene Nagelfluh, and extremely rare in the Plhocene Decken- 
schotter. They abound, on the other hand, in the Pleistocene 
gravels, thus showing that in the middle and at the end of the 
Tertiary Age, erosion and denudation in the Alps had not as yet 
reached those lower rock-formations. 
To the second question the answer would be that a zonal sub- 
sidence of 400 metres (or 1300 feet) is, after all, but a small fraction, 
that is, less than one-tenth of the maximum elevation of the Alps; 
