THE MASSIF OF MONT BLANC. 
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the S.E., separated by the longitudinal valley of 
Chamouni, and bounded by two others, the Vallee 
de Sixt on the irorth, and the Val Ferret on the 
south. These valleys have been greatly deepened 
by erosion, but are clearly due in the first instance 
to geotectonic action. Thus the Val Ferret extends 
from the Allee Blanche on the west to Sembranchier 
on the east, but with higher portions at the Alice 
Blanche and the Col de Ferret, so that the waters 
meet one another almost half-way between the two 
at the foot of the Glacier de la Brenva, where they 
turn south through a transverse valley to Villeneuve, 
S.W. of Aosta between Mont Chetif and the Mer de la 
Saxe, which seem to guard the entrance, as Studer says, 
like the pillars at the entrance of an Indian temple. 
The central range and the summit of Mont Blanc it- 
self (4810 metres) consists mainly of Protogine, flanked 
as we pass to the north by Crystalline Schists of 
undetermined age, succeeded by strata belonging to 
the Carboniferous, Jurassic, and Cretaceous periods. 
The Grands Mulcts and the Dome du Goute 
consist of Crystalline Schist, which indeed surrounds 
the whole massif, except on the south side, where 
it is wanting in the Val d’Entrives and the Val 
Ferret. In this respect the north and south sides of 
the chain present a remarkable contrast. 
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