I go SCENERY OF SWITZERLAND. 
prevails over deposition, the lateral streams have cut, 
and every year are cutting, more deeply into the 
terrace, and the Rhine itself is undermining it, so 
that the houses have in many places had to be set 
back. The formation of these masses of debris, their 
arrangement in a regular terrace, and the present 
period of removal, represent three different phases 
in the history of the river. 
Though the general line of the river was pro- 
bably determined by the great longitudinal fold of 
Switzerland, the exact course has been affected by 
various circumstances. It must be remembered that 
the river originally ran at a great height, at least 
2000 metres, above its present level, and it is there- 
fore by no means easy to ascertain what determined 
the exact line. Moreover, the strata not being 
horizontal, the centre of the present probably 
diverges more or less from that of the original 
valley. 
The following figures will, I think, give a better 
idea of the structure of the Upper Rhine Valley than 
even a long description. 
134 gives a section across the valley at 
Dissentis. The river runs on a deep bed of recent 
deposits, resting on steeply inclined crystalline 
rocks. 
