182 G E O L O G I C A L O B S E R V A T I O N S .
The strata of sandstone and limestone in
the valley going to the town of Echelles
must have undergone a great disturbance,
as is proved by their occurrence in a vertical
position at the lower end of the valley,
though they are nearly horizontal at the
upper end. Hence I should be inclined to
believe, that this extraordinary valley was
formed by a subsidency of the ground.
The masses of limestone that form the
castellated summits of the mountains in
this part of Savoy, range generally from
3000 to 4500 feet above the level of the
valleys, and are all probably parts of one
vast stratum, that once was continuous ; but
this can only be determined by an actual
examination, which, in many instances,
would be difficult to make. The calcareous
strata here, have not the same regularity of
dip over a considerable extent, as the upper
calcareous strata in England, but they very
frequently dip in opposite directions on the
opposite sides of the same mountain, and
are nearly flat on the top ; and as the dip
on each side is often very considerable, to
this cause we may attribute the occurrence
of caps of limestone remaining on the tops
of the mountains, when the strata on the
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G E O L O G I C A L O B S E R V A T I O N S . 183
sides of tlie mountains have nearly or entirely
disappeared. Where the dip is less
considerable, they remain unbroken,forming
what the Wernerians call a mantle-shaped
stratiflcation ; which, however, is always
more or less broken. Now, it is evident
that those strata of limestone which contain
marine organic remains, were formed
under the waters of the ocean, and their
original position must have been nearly horizontal
; at least, it is impossible they could
have been deposited at an angle of sixty or
seventy degrees, or nearly vertical; in which
positions they very frequently occur in this
part of the Alps. It is equally obvious,
that strata of sandstone, or sandstone intermixed
with rounded holders, could not have
been originally deposited at angles exceeding
forty-five degrees, or nearly vertical; in
which position they are also found extending
from the bottom to the top of a mountain,
and preserving nearly the same
thickness throughout their whole extent.
In such instances, and they are of frequent
occurrence, we must admit that the strata
have changed their original position, and
have been elevated either by a subsidency
of one part of the strata, or by the action of
N 4
i-" I S.,
A.