T H E T A R E N T A I S E .
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time in tlie Tarentaise, was, I believe, one
of the first who advanced the opinion, that
many of the rocks in this district ought to
be classed with transition rocks, and that
the gypsum which is of such frequent occurrence,
is a later formation, covering the
other rocks unconformably. M. Brochant
was assuredly right in removing the calcareous
rocks from the rank of primary, to
which they are so far from being entitled,
that I believe they belong to the upper secondary
strata, corresponding in position
to the English strata above the coal-form-
tion. With respect to the gypsum in the
Tarentaise, I have decisively ascertained
that it is subordinate to the limestone, and
interstratified with it, and therefore both
must be considered as cotemporaneoiis.
The coal-formation, or anthracite, in this
part of the Alps will be found, I believe,
to correspond in position with the regular
coal-formation in England, though it may
differ from it in quality; but not entirely
so, for some of the coal in our regular coal-
formation s is also anthracite. *
* Anthracite is that species of coal which burns without
smoke or flame; it bears a strong resemblance to
plumbago (graphite), into which it is supposed to pass.
On the other hand, many of those rocks
which bear the characteristic marks of secondary,
are associated with talcous slate,
which again passes into talcy mica slate,
and is apparently associated with the granite
of the Alps. That this granite is also of
comparatively recent date, may seem too
bold an inference to be admitted, at least
by the geologists of the school of Werner.
M. Brogniart, in a small work, entitled,
“ Sur le Gisment ou Position relative, des
Ophiolites, EupJiotides et Jaspes, ^-c. dans
quelques Parties des Jppennines,'' which he
obligingly gave me as I passed through
Paris, has proved that certain rocks, allied
to talcous slate and serpentine, which have
been generally regarded as cotemporaneoiis
with primary, or with the older transition-
rocks, are in reality posterior to secondary
limestones, and sandstones, of comparatively
recent date, as they may be seen
covering the latter rocks. Hence we may
feel less hesitation in admitting that the
talcous slate of the Alps, with the talcy
mica slate, and the talcy granite, (improperly
called protogine,) are more nearly
allied to secondary rocks, than has been
hitherto imagined. But geologists have
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