strata lie as shown in parts of Fig. 18, and
where it is obvious that strata corresponding to those in dots must have
been originally present.

In the Jura, for instance, a glance at any good map of the district will
show a succession of ridges running parallel to one another in a
slightly curved line from S.W. to N.E. That these ridges are due to
folds of the earth's surface is clear from the following figure in
Jaccard's work on the Geology of the Jura, showing a section from
Brenets due south to Neuchatel by Le Locle. These folds are
comparatively slight and the hills of no great height. Further south,
however, the strata are much more violently dislocated and compressed
together. The Mont Saleve is the remnant of one of these ridges.

[Illustration: Fig. 18.--Section across the Jura from Brenets to
Neuchatel.]

In the Alps the contortions are much greater than in the Jura. Fig. 19
shows a section after Heim, from the Spitzen across the Brunnialp, and
the Maderanerthal. It is obvious that the valleys are due mainly to
erosion, that the Maderaner valley has been cut out of the crystalline
rocks _s_, and was once covered by the Jurassic strata _j_, which must
have formerly passed in a great arch over what is now the valley.

However improbable it may seem that so great an amount of rock should
have disappeared, evidence is conclusive. Ramsay has shown that in some
parts of Wales not less than 29,000 feet have been removed, while there
is strong reason for the belief that in Switzerland an amount has been
carried away equal to the present height of the mountains; though of
course it does not follow that the Alps were once twice as high as they
are at present, because elevation and erosion must have gone on
contemporaneously.

[Illustration: Fig. 19.--_e_, Eocene strata; _j_, Jurassic; _s_,
Crystalline rocks.]

It has been calculated that the strata between Bale and the St. Gotthard
have been compressed from 202 miles to 130 miles, the Ardennes from 50
to 25 miles, and the Appalachians from 153 miles to 65! Prof. Gumbel has
recently expressed the opinion that the main force to which the
elevation of the Alps was due acted along the main axis of elevation.
Exactly the opposite inference would seem really to follow from the
facts. If the centre of force were along the axis of elevation, the
result would, as Suess and Heim have pointed out, be to extend, not to
compress, the strata; and the folds would remain quite u