ne. If these valleys were attributed to their
older occupiers we should therefore confine the name of the Rhone to the
portion of its course from the Rhone glacier to Martigny. From Martigny
it occupies successively the valleys of the Dranse, Guiers, Ain, and
Saone. In fact, the Saone receives the Ain, the Ain the Guiers, the
Guiers the Dranse, and the Dranse the Rhone. This is not a mere question
of names, but also one of antiquity. The Saone, for instance, flowed
past Lyons to the Mediterranean for ages before it was joined by the
Rhone. In our nomenclature, however, the Rhone has swallowed up the
others. This is the more curious because of the three great rivers which
unite to form the lower Rhone, namely, the Saone, the Doubs, and the
Rhone itself, the Saone brings for a large part of the year the greatest
volume of water, and the Doubs has the longest course. Other similar
cases might be mentioned. The Aar, for instance, is a somewhat larger
river than the Rhine.

[Illustration: Fig. 41.--Diagram in illustration of Mountain structure.]

But why should the rivers, after running for a certain distance in the
direction of the main axis, so often break away into lateral valleys? If
the elevation of a chain of mountains be due to the causes suggested in
p. 214, it is evident, though, so far as I am aware, stress has not
hitherto been laid upon this, that the compression and consequent
folding of the strata (Fig. 41) would not be in the direction _A B_
only, but also at right angles to it, in the direction _A C_, though the
amount of folding might be much greater in one direction than in the
other. Thus in the case of Switzerland, while the main folds run
south-west by north-east, there would be others at right angles to the
main axis. The complex structure of the Swiss mountains may be partly
due to the coexistence of these two directions of pressure at right
angles to one another. The presence of a fold so originating would often
divert the river to a course more or less nearly at right angles to its
original direction.

Switzerland, moreover, slopes northwards from the Alps, so that the
lowest part of the great Swiss plain is that along the foot of the
Jura. Hence the main drainage runs along the line from Yverdun to
Neuchatel, down the Zihl to Soleure, and then along the Aar to Waldshut:
the Upper Aar, the Emmen, the Wiggern, the Suhr, the Wynen, the lower
Reuss, the Sihl, and the Limmat, besides several smaller st