180 The Alps in September. 



valleys of the Rhine and Rhone, which start 

 within a short distance of each other, and are 

 only interrupted for a few miles, in the very 

 centre of the region, by the upper part of the 

 valley of the river Reuss, which here forms a 

 kind of elevated plain, enclosed, like the trench 

 itself, between vast mountains ; this plain is the 

 bed of an ancient lake, which once escaped from 

 its prison through a narrow opening at the eastern 

 end, where the Devils' Bridge now stands. On 

 the northern side of the trench, throughout its 

 whole length, the mountain barrier is pierced by 

 ordinary summer routes at three points only : 

 beginning from the west, at the Gemmi Pass, 

 north of the Rhone, where the opening is artificial 

 rather than natural ; at the Grimsel Pass, which 

 debouches upon the source of the Rhone in its 

 Glacier ; and at the point mentioned just now, 

 where the lake made its escape, and where a 

 tunnel driven through the rock has taken the 

 place of an ancient hanging bridge. Nothing can 

 be more striking to a geographical eye than the 

 fact that from the point where it abuts upon the 

 Jake of Geneva (where communication is of course 



