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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 .
candid of’ all geological observers in the
last century: he scarcely ever snfl’ered his
judgment to be warped by an attachment
to theory, on those subjects to which
his attention was mainly directed. 1 have
said that the upper secondary strata scarcely
attracted his attention, otherwise he would
have found that tlie upper calcareous
mountains, on the western side of Savoy,
all rest upon an immense formation of
sandstone, and are interstratified with i t ;
and so far from sandstone being more recent
than the limestone, or of extraordinary
occurrence, it constitutes a considerable
portion of those mountains which are called
calcareous. It is this which gives to the
mountains in the Bauges, and in the neighbourhood
of Annecy and Chamberry, their
peculiar external form and character : it is
this which has determined the form and
extent of many of the valleys; and it is
this which offers a kind of key to the physical
structure of the outer range of the
Alps. The general appearance of the
mountains in the part of Savoy I have
been describing, is that of immense walls
or ridges of limestone, supported on very
steep slopes, which are frequently deeply
furrowed; but, except in these furrows,
the slopes are covered with verdure.
The delineations of the mountains on the
Lake of Annecy, and of the Dent D’Alen-
pon, (Plate II.) and of Mont Grenier, will
convey a tolerably correct idea of their general
form. Even before I had an opportunity
of examining these mountains closely,
I was convinced that their slopes were not
the debris of the upper limestone strata,
but were formed by the under strata, which
were much softer, and on which the limestone
immediately rested. In proportion
as these soft strata have been washed away
from the base of the limestone, they have
left it unsupported, and at length have
produced those fatal eboulements so frequent
in this part of Savoy ; eboulements
which could not take place to the great extent
they do, if the whole of the mountains
were limestone.
At the valley of les Echelles, the immediate
junction of the limestone with
the sandstone may be seen soon after
entering tbe valley from the archway.
This vast wall of limestone, nearly 1000
feet in thickness, rests upon a mass of
sandstone of unknown d e p th : there is
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