viii RIVERS AND LAKES 305 



now at Geneva and by Lyons to the Mediter- 

 ranean, but near Lausanne by Cissonay and 

 Entreroches to Yverdun, and through the 

 Lake of Neuchatel into the Aar and the Rhine. 



But this is not the whole of the curious 

 history. At present the Aar makes a sharp 

 turn to the west at Waldshut, where it falls 

 into the Rhine, but there is reason to believe 

 that at a former period, before the Rhine had 

 excavated its present bed, the Aar continued 

 its course eastward to the Lake of Constance, 

 by the valley of the Klettgau, as is indicated by 

 the presence of gravel beds containing pebbles 

 which have been brought, not by the Rhine 

 from the Grisons, but by the Aar from the 

 Bernese Oberland, showing that the river 

 which occupied the valley was not the Rhine 

 but the Aar. It would seem also that at an 

 early period the Lake of Constance stood at a 

 considerably higher level, and that the outlet 

 was, perhaps, from Frederichshaven to Ulm, 

 along what are now the valleys of the 

 Schussen and the Ried, into the Danube. 



Thus the head-waters of the Rhone appear 

 to have originally run by Lausanne and the 



