202 Dr. Du Riche Preller—Crystalline Rocks of Piémont. 
and eye-gneiss;1 a large area, about 12 by 10 kilometres, of granite 
intrusive in the gneiss nucleus; and asurrounding belt of great masses 
of small-grained gneiss and mica-schist. The primitive gneiss, and 
to a much lesser extent also the intrusive granite is traversed in all 
directions by countless thin veins of acid rocks, chiefly microgranite, 
aplite, quartziferous and hornblendic porphyrite, while the outer 
eneiss contains intercalated masses of both augitic and hornblendic 
diorite and of compact serpentine. These rocks, being here intimately 
associated with gneiss, are not pietre verdi with secondary elements ; 
but they show that the prototypes of the latter are not wanting even 
in the more ancient crystalline series. 
Professor Sacco regards the position of the gneiss and granite of the 
Argentera massif as reversed, viz. the granite not as intrusive, but as 
constituting the nucleus of the massif, enveloped by an enormous mass 
of gneiss intensely metamorphosed and of Permo-Carboniferous age*; 
but Franchi’s interpretation * is no doubt correct, the more so as there 
is no passage from gneiss to granite, and the intrusive character of the 
latter is beyond question. Moreover, the Triassic beds on the eastern 
as well as the Permian on the southern periphery of the massif 
overlie the gneiss with marked unconformity, thus pointing to a long 
interval of deposition and therefore to a considerable difference of age 
between the gneiss and the overlying younger formations. 
IJ. THe Monre Viso Grove. (Figs. 1 and 2.*) 
This area forms an elongated lenticular ellipsoid from south to north, 
about 40 kilometres in length and 2 to 6 kilometres in width, between 
the Maira Valley at its southern and the Pellice Valley at its northern 
end, while nearer the centre on its southern side it is cut by the 
Varaita Valley. In the centre itself, on the eastern side, rises the Po, 
which, although in its lower course it collects the drainage of all the 
rivers of the Piémontese Alps, is, in its upper torrential and cascade 
course, the shortest of all. 
1 The term ‘ primitive’ gneiss is used throughout this paper in its strictly 
stratigraphical sense as the ‘fundamental’ substratum of all the more recent 
formations. 
2 F. Sacco, ‘‘L’Age du massif de l’Argentére’’: Bull. Soc. géol. France, 
1907, vi, p. 484 et seq. Also ‘‘Gruppo dell’ Argentera’’: Mem. R. Acc. 
Scienze, Torino, 1911, lxi, p. 457 et seq. 
3S. Franchi, ‘‘ Osservazioni lavori geol. Alpi Marittime’’: Boll. R. Com. 
geol., 1907, p. 145 et seq. Among the excellent reports in the Boll. R. Com. 
geol., besides those already quoted in this and the preceding paper, are the 
following relating to the Cottian Alps :— 
8. Franchi, ‘‘ Tettonica della zona pietre verdi del Piemonte,’’ 1906, p. 118 
et seq.; ‘‘ Appunti geol. e petrogr. Monti di Bussoleno,’’ 1895, p. 3 et seq. 
S. Franchi and V. Novarese, ‘‘ Appunti geol. e petrogr. dintorni di Pinerolo,’’ 
1895, p. 385 et seq. \ 
V. Novarese, ‘‘ Rilevamento geol. Valle Germanasca,’’ 1895, p. 253 et seq. ; 
‘“Rilevamento geol. Valle Peliice,’’ 1896, p. 231 et seq. 
A. Stella, ‘‘Rilevamento geol. Valle Varaita;’’ 1895, p. 283 et seq. ; 
‘* Rilevamento geol. Valle Po,’’ 1896, p. 268 et seq. 
4 Figs. 2-4 will appear in the next part of this paper in June. 
