Dr. Du Riche Preller — Three Glaciations of Switzerland. 33 



The general limit of this last glaciation in the North of Switzerland 

 M^ould therefore be indicated by a curve from Schaffhausen to Zurich 

 and Soleure.^ 



Upon each of these periods of filling up, there followed an mter- 

 glacial period of erosion, during which the rivers swept away and 

 carried towards the sea the greater part of the accumulated glacial 

 deposits. The first of these interglacial periods must have been 

 very long and the erosive action very powerful, seeing that in the 

 North of Switzerland the belt of hollow nagelfluh and isolated oc- 

 currences of moraine, such as that of Utliberg, are the only surface 

 remains of the vast amount of material which the first Pliocene 

 glaciation deposited, both through direct and through fluvio-glacial 

 action. The second interglacial period was of much shorter duration ; 

 Heer estimated it at 6000 years ; but it lasted at any rate long 

 enough to produce the lignite deposits near Durnten, Wetzikon, 

 Uzna'ch, and Eorschach and the similar lignite bands near the Lake 

 of Thune, which escaped or resisted the erosive action of the old 

 Linth and of the Kander respectively; and, together with the 

 debris-cone in the Lorze valley near Zug, constitute indisputable 

 evidence of that second interglacial period.'- The third period of 

 glaciation and filling-up was succeeded by our own alluvial time, 

 which is again a period of active erosion. This is evidenced by 

 such rivers as the Rhine, the Aare, and the Limmat, of which the 

 former has at various points eroded all the successive glacial and 

 fluvio-glacial deposits'^ down to the solid rock, and has thereby 



1 Broadly speaking, the three glaciations are typically represented in the Zurich 

 District by the three ranges of hills running parallel to the lake, viz. : — 



1st glaciation, moraine of Utliberg or Albiz range, mean altitude 2600 feet. 

 2nd „ ,, Zurichberg ,, ,, 1800 ,, 



3rd. ,, ,, Gattikon hills, and belt of ) j^-qq 



moraine walls in Zurich j " " 



above sea-level, or 1150, 450, and 150 feet above lake-level respectively. In all 

 cases, the moraine rests on molasse. Quite recently I had occasion again to examine 

 these deposits in the company of Prof. Bonney. , ^ , . ^i , wi, 



2 Amono- the deposits of the second interglacial period should be further noted the 

 " Loss "viz. the fine sand and loam which occurs extensively along the foot of the 

 Jura as well as in the Rhine valley near Rhinfelden and Basle, and also m the Aare 

 valley near Aaran, and again near the confluence of the Aare and the Rhme, and 

 generally rests on the fluvio-glacial deposits of the second glaciation. By some 

 ^eoloo-ists this Loss has been held to be simply mud, deposited by rivers when in 

 flood ^ by others as the product of chemical metamorphism ; and again by others, 

 such as Professors Eichthofen and Muhlberg, as of ^olian origin, viz. as blown 

 sand, this latter theory being the one now in vogue. Further interglacial evidence is 

 afforded by the so-called lake -chalk of Zurich, viz. the chalk which separates out ot 

 the lake water, aud a deposit of which was found in the bed of the Limmat at the lower 

 end of the lake, between the moraine of the second and third glaciations. 



3 The fluvio-glacial deposits or gravel-beds of the second and third glaciations, 

 which in the North of Switzerland extend along the principal rivers to their con- 

 fluence with the Rhine, and thence and beyond to Basle, are called by Dr. Du Pasquier 

 the Upper-Terrace and Lower-Terrace Gravels respectively. The moraines_ of the 

 second and third glaciations are called by Swiss geologists the "outer" and ''inner 

 moraines respectively; Dr. Du Pasquier, in deference perhaps to these time-honoured 

 desio-nations, and also to those of ' ' first and second glacial periods, or " last and 

 "penultimate" glaciation, terms the Pliocene (hollow nagelfluh) glaciation the 

 "old" flacial period; I have called them simply first, second, and third glaciations. 



DECADE IV. VOL. I. — NO. I. " 



