Glaciers of the Isar and the Linth. 261 



Toelz, Laufen on the Salzach, and at Stefansbriicke near Innsbruck, 

 Penck has discovered moraines ; but at the base of the Nagelfluh, 

 Tertiary strata exclusively have been met with. 



Where we met with recently exposed surfaces, showing the depo- 

 sition of the moraine on the diluvial Nagelfluh (at Tutzing, Berg, 

 Starnberg), the surface of this latter was smoothed and polished as 

 distinctly as if it had been a homogeneous rock, and striated in 

 the same direction as the course of the valley. The individual 

 pebbles in the Nagelfluh were also evenly cut through in section. 



Also when the contact surface of the moraine and the glacial 

 gravels (b) was exposed, there was nearly always a sharply-marked, 

 often discordant, boundary between the two deposits, without dis- 

 turbance in the underlying gravel; and occasionally the projecting 

 boulders in the gravel were striated in the direction of the valley, 

 though no connected striated surface had been formed on them. 



North of the Starnberg Lake, we noticed a moraine irregularly 

 interpenetrated with beds of gravel and sand ; which we recognize 

 as a deposit formed near the terminal end of a glacier (Penck, Ver- 

 gletscherung, etc. p. 132, figs. 4, 5). 



IT. — The Quaternary Deposits in the District of the Lahe of Zurich. 



In the valley of the Lake of Zurich, as in the lake district of 

 Upper Bavaria, Upper Miocene strata form the foundation on which 

 the Quaternary deposits rest, and these latter are also divided into 

 gravels (Schotter) and moraines. 



In contrast, however, to the exceptional regularity with which the 

 gravel deposits in the Bavarian lake district succeed each other under 

 the moraines, those at the lower end of the Lake of Zurich show, on 

 the one hand, an extremely slight connected development, and on the 

 other, they present such great differences in regard to the respective 

 elevations at which they are deposited, that it seems almost impossible 

 definitely to mark out their limits, or to parallel the deposits of 

 different localities. 



(a.) There is indeed found occasionally, on certain particular 

 elevations between the valleys, a deposit of Nagelfluh, resembling 

 petrographically the Bavarian diluvial Nagelfluh (Uetliberg 870 m., 

 Baden 470 — 490 m., Sihlsprung near Hirzel [outside the bounds 

 of our united excursion] 580 — 640 m.) ; but this is so limited in its 

 distribution, and the places in which it appears are so far apart, 

 that, with our present knowledge, it cannot be considered as the 

 remains of a general covering. Besides, moraines occur under 

 the cavernous Nagelfluh of the Uetliberg, whilst they have never been 

 met with below the Bavarian diluvial Nagelfluh, and on the other 

 hand moraines do not any longer appear above this Nagelfluh as they 

 do in that of Bavaria. The cavernous Nagelfluh of Sihlsprung near 

 Hirzel rests, according to Heim, on ground-moraines, and is covered 

 by immense upper moraine deposits. 



(6.) A somewhat different formation of loose gravels (Schotter) 

 and Nagelfluh, either with or without decayed pebbles, is present, 

 though in very few localities, on the slopes of the valley of the Lake 



