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262 P O S I T IO N OF
and turns southward, which is also the
direction of the Vouache. The beds ot
the Jura are, at this extremity, nearly perpendicular
to the horizon, not declining
from the vertical line more than 15 : their
dip is to the east. This position of the
strata is seen above the fort, and lower down
from the fort to the Rhone, and still moie
distinctly behind the little chapel, about
300 feet east of the fort. The beds of the
Vouaches have exactly the same position ;
they cut the course of the Rhone transversely,
a little above the fort of L ’Ecluse ;
their planes, like those of the Jura, are
nearly perpendicular to the horizon, dipping
at about 15° east from the vertical line.
The position of these beds is so remarkable,
and so singularly and precisely determined,
that it proves, in my opinion, as
much as a fact of this nature can be pioved,
that th e Vouache and the Jura were formerly
united, and, consequently, afforded
no passage for the waters inclosed in our
basin.” Voyages dans les Alpes, vol. i.
Perhaps the different opinions that have
been entertained respecting the position
of the strata here, originates in an optical
illusion that they present, when seen fiom
different points of view : this the annexed
figures may serve to explain.
Fig 2, represents the strata on the south
o f the Rhone, seen in the direction of their
bearing, which gives the true angle of
the dip, towards b , eastwards. The lower
part of the mountain, on the western side,
w, is much broken, and covered with fragments,
which conceal the stratification.
s 4