30 Dr. Du Biche Preller — Three Glaciations of Switzerland. 



is still preserved on the Utliberg. This moraine, which is much, 

 older than the moraine on which the town of Zurich is chiefly built, 

 passes gradually into moraine sand or surface moraine ; and this 

 again passes into hollow nagelfluh, which forms a cap with, per- 

 pendicular sides from 60 to 100 feet in depth. The superposition 

 referred to is exceedingly characteristic, and leaves no doubt what- 

 ever as to the fluvio-glacial origin of the hollow nagelfluh, viz. 

 as having been deposited, not by the glaciers themselves, 

 but subsequently by the streams emerging from them, and 

 following, in the main, the lines of the moraine deposit. The 

 occurrence of this Pliocene nagelfluh at such an altitude of 872 

 metres (2880 feet) above sea-level, or 460 metres (1520 feet) 

 above the present level of the Limmat valley at Zurich, led Prof. 

 Heim and also Prof. Muhlberg, an authority on the glacial deposits 

 of the Aare Valley, to conjecture that that nagelfluh had been de- 

 posited by a stream flowing at that altitude between the glaciers 

 of the Zurich and Zug valleys;^ but the occurrences of the same 

 Pliocene nagelfluh not only on the other side of the Zurich lake, but 

 throughout the north of Switzerland, in a line between Zurich and 

 the Khine, clearly show, as Dr. Du Pasquier also points out, that 

 it is not a local fluvio-glacial deposit, but forms part of the Swiss 

 Deckenschotter as a whole. 



The deposit near Baden is to be found in a ravine locally called 

 the " Teufelskeller," situated at about 470 metres above sea-level, 

 viz. about 1300 feet lower than the summit of the Utlibei-g. It 

 constitutes perpendicular banks thirty to a hundred feet in height, 

 and shows all the characteristics of the Utli deposit, which by the 

 much larger rounded ofi" pebbles and the extremely hard cement 

 consisting of thin calcareous films or skins, distinguish it from the 

 younger fluvio-glacial gravel deposits of the Limmat valley. In 

 this occurrence its composition is more or less uniform, and the 

 banks descend too much below the surface of the ground to show 

 either the moraine or the molasse on which it rests ; but on the 

 other side of the same hill there is a quarry about 40 feet in 

 vertical depth, which is not mentioned in Dr. Du Pasquier's ad- 

 mirable work, and in which I found distinct evidence of the hollow 

 nagelfluh becoming towards the base of the quarry gradually a 

 finer and looser conglomerate, and passing into sand and surface 

 moraine as shown in the diagram. The principal constituents of the 

 hollow nagelfluh are here, as on Utliberg and elsewhere, quartzite, 



^ Prof. Heim, Neujahrsblatt, 1891. Prof. Heim argues that the glaciers 

 preserved the Limmat and other lake valleys from being choked up by surface 

 moraine, since they carried it on their backs and thus served as a bridge. But 

 these valleys must have been, and were, filled up to a considerable extent by 

 ground moraine, part of which was subsequently again removed by fluvial erosion. 

 Judging from the depth at which the ground moraine must have been deposited at 

 the bottom of some of these preglacial or Miocene valleys, and the altitude at which 

 sheet-gravel is found (3300 feet above sea-level at the Bachtel east of Zurich, and 

 3500 feet near Bregenz on Lake Constance), the glaciers must in many places have 

 reached a thickness of 2000 feet and more. Above Amsteg, in the Eeuss valley, the 

 glacier scratches reach up to 6600 feet, and in the Ehone valley (Canton Vaud) 

 even up to 11,000 feet altitude above sea-level. 



