VI THE GORGE OF THE AAR AND ITS TEACHINGS 139 



which Professor Bonney has advanced as an argument 

 against the theory I am advocating. He says : " This 

 grassy basin might well be claimed as an instance of 

 glacial erosion — by which indeed it possibly may have 

 been deepened ; but if we attribute to this agency the 

 removal of all the rock between the summit level of the 

 barrier and the present meadow-floor, how are we to 

 explain the existence of the steep rocky slope down which 

 the road to Imhof descends in zigzags ? The slopes, in 

 the teeth of an advancing glacier are always compara- 

 tively gentle, and very unlike those which are presented 

 by this rocky rib." This would be a valid objection if 

 the Aar glacier had continued its course in a straight, or 

 nearly straight, line to Meiringen; but the influx of a 

 large glacier-stream from the north-east must have so 

 diverted that of the Aar, that the resultant flow would 

 have been across the lower valley and almost along the 

 steep face of Kirchet instead of directly across it. This 

 would have been the case, because the glacier stream 

 from the north-east was not only equal in size to that of 

 the Aar valley, but had a more rapid descent, and, there- 

 fore, a quicker flow. In the last five miles the Aar 

 valley has a fall of about 1,500 feet, while the two north- 

 eastern valleys have an average fall of about 2,000 feet ; 

 and they are also much wider, which would still further 

 facilitate raj)idity of outflow. 



The influx of this powerful glacier stream from the north- 

 east well explains the main physical features of the 

 district, especially the nearly uniform plateau of the 

 Geissholz Alp, at about the same level as the top of the 

 Kirchet, bounded by the line of precipices extending to 

 the Reichenbach falls, and continued along the south side 

 of the valley. On the north side the plateaux are at a 

 higher level, indicating that the motion of the glacier was 

 there less rapid, and its grinding power correspondingly 

 diminished. While the main body of the glacier thus 

 moved onward towards Thun, the meeting of three glacier 

 streams, of unequal size and velocity and from different 

 directions, would produce a vast ice-eddy at their junction, 



