Vol.51.] AND INTERGXACIAL DEPOSITS IN SWITZERLAND. 387 



the terraces even at low levels. At the Uetliberg there was a thick 

 gravel now cemented into a calcareous conglomerate resting on 

 boulder-clay, and he rather doubted whether any very great glacial 

 extension had taken place since its formation, as in any such case 

 the materials would probably have been re-arranged. 



The Author said, in reply to Prof. Bonney's remarks, that the 

 Pliocene age of the Cavernous Nagelfluh appeared conclusively 

 proved (1) by the fact of its being undoubtedly older than the 

 Pleistocene gravels, but younger than the Miocene Nagelfluh, and 

 entirely different from both ; (2) by the fact that in one case in the 

 Kander district the younger gravel distinctly overlay the Cavernous 

 Nagelfluh, with an intermediate layer of boulder-clay ; and (3) by 

 the analogy between the Cavernous Nagelfluh and the old Phone, 

 Bresse, and Italian conglomerates, in which Upper Pliocene fossils 

 had been found. With reference to the correlation between the 

 fluvio-glacial Nagelfluh and the plateau-gravels in the British Isles, 

 he merely wished to suggest that, in time, some at least of these 

 gravel-deposits would come to be recognized as being older than the 

 lower and upper Till. 



In reply to Mr. Monckton's remarks, he said that the fact that such 

 Nagelfluh-deposits as those of the Uetliberg, Baden, and the Gebens- 

 dorfer Horn had not been swept away by subsequent glaciations 

 .appeared at first sight puzzling, but was easily explained by the well- 

 known phenomenon, that when advancing glaciers met any serious 

 obstacle, they either passed over it, or divided and went round it. 

 With reference to the alterations which, as Mr. Monckton suggested, 

 had taken place in the configuration of the hills on both sides of the 

 Lake of Zurich at its lower end, the hills on the right or north side 

 showed the characteristic, flat, dome-shaped outlines of the Molasse 

 formation, and had undergone very little change ; but the hills on 

 the Uetliberg side had undergone, and were still undergoing, con- 

 siderable change, owing to the river Sihl having, since the third 

 glaciation, scooped out its present bed between the lake and the 

 Uetliberg or Albis range, the erosion being still in active progress. 



