488 Prof. B. Studcr on the Origin of the Swiss Lakes, 



convex rocks or roches 7iiouton?iees, whilst the second gives rise 

 to cavities. The hollows or marmites which occur as an excep- 

 tion to this rule in what appears to us to be the rocky bed of 

 ancient glaciers, are justly ascribed to the friction of gravel set 

 in rotation by falls of water through the glacier, or to the 

 moulins. 



Mr. Ramsay rightly assumes that the basins of our lakes can- 

 not have been hollowed out by running water. A certain incline 

 is necessary to enable rivers, even with a muddy bottom, to hol- 

 low out their bed ; and this slope does not occur either in the 

 lakes of the Jura or in those of Zurich and Constance. Other- 

 wise, if only a great mass of water were necessary, why do we 

 not find the Nile and the Ganges in their great floods hollowing 

 out basins for themselves ? And even if a great inclination be 

 added to the mass of water, and the soil is favourable to erosion, 

 deep holes or marmites only are produced, and their extent never 

 exceeds the radius of the direct action of the impact of the water 

 and of the pebbles which it sets in motion. Of this we have the 

 proof in our waterfalls, in those of Italy, and in the cataract of 

 Niagara, so well described by M. Desor, as quoted by M. Mor- 

 tillet. How, moreover, could we suppose that the Rhine, at so 

 great a distance from the high mountains, has had sufficient 

 force to hollow out a basin like that of the Lake of Constance ? 

 On the same principle one might suppose the Caspian Sea to be 

 due to the erosion of the Volga, or the Dead Sea to that of the 

 Jordan, and regard these great depressions as mere effects of the 

 erosion of the rivers which traverse them. And if we assume 

 that the basin of the Lake of Constance extended as far as the 

 Schollberg near Sargans, and that it was subsequently filled up 

 by detritus as far as Rheineck, how can we suppose that the 

 same river, which in the first place hollowed out its bed from the 

 Schollberg to Schaffhausen at more than a thousand feet below 

 the present surface of the soil, should have afterwards filled it 

 up ? Those who consider that our lakes have been hollowed out 

 by the action of water maintain no such doctrines. M. Desor, as 

 we have seen, requires great floods caused by the upheaval of the 

 Alps ; and the celebrated Escher von der Linth*, who knew better 

 than anyone the power of rivers, also calls for the intervention 

 of diluvian waters. It is always the great debacle of De Saussure 

 which, in the theories of its learned author and down to our own 

 day, has played so important a part in the geology of Switzerland. 

 But even if, with the view of increasing the force of the shock, 

 we suppose with von Buchf that the waters of the sea were 

 thrown, by the sudden upheaval of the Alps, over the highest 



* Gilbert's Annalen, vol. liii. (1816). 

 f Poggendorff's Annalen, vol. ix. (182/). 



