192 F O R M A T I O N O F M O U N T A I N V A L L E Y S . 193
is generally lost between the English strata
and those of Savoy, though a very great
number of our English fossils, have their
analogues in this part of the Alps. 1 do
not think the inference to be drawn from
similarity of organic remains in the strata
in distant parts of the globe, can generally
be extended so far as many geologists suppose,
yet 1 am persuaded that the fossil-
shells in the mountains near Annecy, prove
that they must be considered as belonging
to formations considerably above the coal
formations in England.
1 now wish to direct the attention of geologists
to the singular fact of thick beds
of soft sandstone occurring in a nearly vertical
position among strata of highly indurated
limestone, as I am inclined to believe
that it will satisfactorily explain the formation
of this valley where the coal-mine
is situated, and of many other mountain-
valleys in Savoy.
To render this intelligible, let us suppose
the valley at the coal-mine to be filled
up by prolonging the edges of the strata
to the dotted lines a a; this will represent
the strata when they were first elevated.
(See page 186.) Now if we suppose currents
of water to pass over the basset edges of
the strata, the sandstone, being soft, would
be excavated far more rapidly than the
limestone on each side of it, and thus a
deep trough would be formed, and portions
of the upper strata of limestone, for want
of the support of the sandstone strata,
would break down and widen the valley.
Such appears clearly to have been the case,
for the debris from the limestone-strata has
formed a talus or slope. (See page 186.) A
mountain that ranges on the western side
of the lake of Annecy, and which terminates
near the city of Annecy, when seen in profile,
offers a good illustration of valleys
formed in this manner on a small scale.
Several longitudinal valleys run parallel to
each other, from the top of the mountain,
which have evidently been excavated in the
edges of soft strata that occur in the limestone,
and dip at a very acute angle. At
the coal-mine, the vertical position of the
soft strata, containing coal and marine organic
remains, could not possibly have been
their original o n e ; nor have these strata
been dislocated by a partial fault, as they
are conformable to the position ofthe other
strata in a mountain which is about nine
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