320 THE BEAUTIES OF NATURE CHAP. + 
feet above the sea level, but rises towards the 
Kast and North until near Fine it reaches an 
elevation of 972 feet. As this terrace must 
have been originally horizontal we have here 
a lake barrier, due to a difference of elevation, 
amounting to over 600 feet. | 
In the same way we get a clue to the curi- 
ous cruciform shape of the Lake of Lucerne 
as contrasted with the simple outline of such 
lakes as those of Neuchatel or Zurich. That 
of Lucerne is a complex lake. Soundings 
have shown that the bottom of the Urner See 
is quite flat. It is in fact the old bed of the 
Reuss, which originally ran, not as now by 
Lucerne, but by Schwytz and through the 
Lake of Zug. In the same way the Alpnach 
See is the old bed of the Aa, which likewise 
ran through the Lake of Zug. The old river 
terraces of the Reuss can be traced in places 
between Brunnen and Goldau. Now these 
terraces must have originally sloped from the 
upper part downwards, from Brunnen towards 
Goldau. But at present the slope is the other 
way, 2.e. from Goldau towards Brunnen. 
From this and other evidence we conclude 
