THE MOUNTAINS OF SWITZERLAND. 
85 
Switzerland is divided roughly into equal parts 
by four great rivers, — the Rhine, the Rhone, the 
Reuss, and the Ticino. These four rivers rise on the 
same great “central massif.” The valleys are not, 
however, of the same character. The Rhine-Rhone 
valley from Martigny to Chur is a “geotectonic” 
valley; its direction coincides with the direction or 
“strike” of the strata, and it was originally deter- 
mined by a great fold in the strata. 
The Reuss and Ticino valleys (except the upper 
part of the Reuss in the Urserenthal, which is in fact 
a part of the Rhone-Rhine valley and the upper part 
of the Ticino in the Val Bedretto, which is also a 
longitudinal valley) are transverse; they cross the 
strata approximately at right angles, and consequently 
the rocks on the two sides are the same. They are 
entirely or almost entirely due to erosion. 
In the Jura, where the foldings are comparatively 
gentle and the denudation has been much less, the 
present configuration of the surface follows more 
closely the elevations and depressions due to geo- 
logical changes (see Fig. 5). 
In the Alps the case is different, and the de- 
nudation has so far advanced that we can at first 
sight trace but little relation between the valleys, as 
indicated by the river courses and the mountain 
