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GEOLOGY OF
am inclined to believe, that it is the same
formation as the bed of dark schist under
the mountains of Servos, which contains
nodules with impressions of ammonites, as
at Whitby. 3dly, A darkish grey earthy
limestone in thin beds. This is seen in situ
near the bottom o f the Glacier de Bois; it
is a meagre water-setting lime, and bears a
strong resemblance to some of our beds of
blue lias, — which I believe it to be. I
saw. a limestone exactly similar over gypsum,
in the Valíais, east of Martigny, and I
have little doubt but that this limestone in
Chamouny, was originally associated with
the gypsum formation in the valley,
though the latter has been much worn
away and deranged, particularly about the
middle of the valley, where Saussure observes
that a portion of the primary and
secondary formations, appear to have fallen
down in a state of confusion. Indeed,
though the secondary calcareous strata in
the valley of Chamouny have most generally
the same range as the beds of primary rock,
they are in many places variable. Ebel, in
an imaginary section of the Alps, has represented
a vertical bed of primary limestone
on the northern side of Mont Blanc,
which I believe is erroneous, the limestone
on the northern side being assuredly
more of the nature of the English
lias, than of primary limestone. I f the p rimary
limestone in Ebel’s section be intended
to represent that of the Col de
Bon Homme, it should have been placed
south of the summit of Mont Blanc.
The gypsum of Chamouny and at St.
Gervaise, is undoubtedly the same as that
of the Tarentaise already described. The
specimen I got from St. Gervaise was precisely
of the same kind as that in the
valley of Brida, which appeared to have
passed from the state of anhydrous to
common gypsum, by exposure to the atmosphere.
Some of the gypsum in Chamouny
is fine-grained common gypsum,
and very white, like that of the pierre
blanche at the foot o f the Little St.
Bernard.
It will be recollected, that on the return
of Captain Boss from Baffin’s-Bay, much
surprise was excited by the account of
the red snow (as it was called) covering
some of the snow mountains near the coast
in those, high latitudes. It is a little remarkable
that it should have escaped pub