254 
SCENERY OF SWITZERLAND. 
first very different from the present. The Vosges 
and the Black Forest were continuous, the subsidence 
which now separates them not having yet taken 
place, so that the Rhhie Valley at Basle was not in 
existence. 
Nor had the gorges by which the Rhone finds its 
exit through the Vuache yet been formed, and the 
consequence was that the whole drainage of Switzer- 
land north of the Alps found its way by the Danube 
to the Black Sea. There is reason to believe that 
for some time after the subsidence of the Basle Valley 
had taken place the upper waters of the Rhone still 
joined the Rhine, and ran over the plains of Germany 
to the North Sea; finally, however, it broke its way 
by the Fort de L’Echise, and falling into the Saone, 
runs to the Mediterranean. Another general change 
m the river system is that the crest of the Alps has 
retreated northwards. The southern slope being 
much steeper than that to the north, the Italian rivers 
have more power of erosion than their northern rivals, 
and are gradually eating their way back. The Upper 
Engadine is a conspicuous example. 
Many minor changes have taken place: partly (i) 
through recent changes of level, as for instance that 
which has diverted the Reuss from its old course by 
the Lake of Zug, and driven it round by Lucerne; 
