~~ =e 
Vill RIVERS AND LAKES 805 
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 
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