i88 
SCENERY OF SWITZERLAND. 
for the same reason, the condition of the Aar below 
Soleure, which also on account of the general slope 
of the country receives all its important tributaries 
on the south. 
Several of these streams are dangerous torrents, 
and are still rapidly deepening their valleys. For 
instance, the Glenner, which drains the Lugnetz, and 
falls into the Rhine at Ilanz, is in very active opera- 
tion. Its valley is a deep notch, almost a gorge. 
The villages are situated high above the stream on 
an old river terrace, which in the lower part of the 
valley has a height of looo metres, and at Ober- 
lugnetz of about 1500, above the water.* None of 
the lateral streams are able to form cones, all the 
material they bring down being swept away by the 
Glenner. Under the village of Riem the whole 
slope is in a most insecure condition, the houses are 
continually cracking and giving way, and have to be 
supported and restored. 
The drainage area of the Upper Rhine was 
formerly larger than it is at present. The Italian 
rivers having a steeper course, have here, as else- 
where (for instance, in the Engadine [see p. 240], 
and indeed we may say along the ridge of the Alps 
generally), eaten their way northwards, invaded the 
* Heim, Beitr. z, Geol. K. d. Schw,^ L. xxjv. 
