THE MASSIF OF MONT BLANC. 
I I I 
Rendu suggested the explanation. A smaller 
glacier from the Buet joins that of the Arve at Ser- 
voz, and continues with it down the valley. This 
affluent, however, came from a calcareous region; the 
blocks forming its moraine, therefore, are undis- 
tinguishable from the debris which have fallen from 
the mountains, and are moreover more perishable 
than the blocks of Protogine coming from the Mont 
Blanc range. At the Waterfall of Arpeuaz (Fig. i, vol. i. 
p. 56) the foldings of the rocks are beautifully shown. 
The whole plain between Cluses and the SaRve is 
covered with glacial deposit, and strewn with blocks 
of Protogine, except a calcareous band of very vari- 
able width extending from the opening of the valley 
of Bornand, by St. Laurent, La Roche, and Cornier, 
and ending somewhat to the east of Regnier. This 
is known as “Les Rocailles,” is sterile and com- 
paratively uncultivated. It is, in fact, a moraine 
belonging to the ancient glacier of the Bornand 
valley. 
Fig. 104 shows the fan structure so characteristic 
of the Alpine massives. 
The junction of the Crystalline Schists and the 
Protogine is well seen at L’ Angle, on the edge of the 
Mer de Glace, above Montanvert. The schists be- 
come more Crystalline as we approach the Central 
