GEOLOGICAL HISTORY OF SERPENTINES. 189 
great “mass of non-stratified rocks, comprising euphotides, serpentines, variolites, and 
various rocks of passage between these types.” These ophiolitic rocks, which correspond 
to the lower part of the pietre-verdi zone of Gastaldi, are regarded by Lory as eruptive, 
and have not been recognized in his scheme of the divisions of the primitive schists. Their 
appearance among the lustrous schists is thus, according to him, an irruption in the midst 
of the trias, instead of being, as we should rather regard it, a protrusion of a portion of 
the pietre-verdi zone in the midst of the lustrous schists, which are here unconformably 
superimposed upon it, as elsewhere upon the ancient gneisses. 
§ 66. The history of the upper or argillo-talcose schists of the section under considera- 
tion will be found discussed at some length by the present writer in a review of Favre on 
the geology of the Alps in 1872. It was there shown that these, though very distinct from 
and unlike the underlying micaceous, hornblendic schists and gneiss, are really crystalline 
schists, and very unlike the normal trias of the region, to the horizon of which they had 
been referred by most geologists. The section of them afforded by the Mont Cenis tunnel 
was then and there discussed, and many reasons were given for rejecting the notion 
of their triassic age, and for assigning them to the eozoic period. As was shown in a sub- 
sequent note to that review, Favre, after publishing his book in 1867, was led to adopt 
the view advanced by Gastaldi in 1871, that these schists were pre-carboniferous, though 
probably paleozoic, a conclusion which the latter subsequently exchanged for that of their 
eozoic age, as maintained by the present writer since 1872. * 
§ 67. The section traversed by the St. Gothard tunnel furnishes important details for 
Alpine geology. This work, beginning at Goschenen, on the north, ends at Airolo on the 
south side of the mountain, the entire distance being 14,920 meters. The first 2,000 meters 
from the northern portal are in the massive rock of the Finsteraarhorn, called by various 
observers granite or granitic gneiss, and by Stapff regarded as an older gneiss than that 
of the remaining part of the section. Between this and the mountain of St. Gothard is 
included the clesely-folded synclinal basin of Urseren, while the southern portal, at Airolo, 
is on the northern side of the similar basin of Ticino; the great intermediate mountain-mass 
of highly inclined and faulted strata, presenting a fan-shaped arrangement. The basin of 
Urseren holds, folded in gneiss and mica-schist, a group of strata consisting of argillites, 
sometimes calcareous and often graphitic, with grey lustrous, unctuous sericite-schists, 
together with quartzose layers, and others which, from a development of feldspars, pass into 
an imperfect gneiss. With these are interstratified granular crystalline limestones, white 
or banded with grey, with dolomite and karstenite. Some of the limestones included in 
this synclinal have aflorded indistinct organic forms, and the series has been referred, like 
the similar rocks noticed in previous sections, to the mesozoic period. A repetition of these 
is met with in the Ticino basin, on the south side of the mountain. Apart from these, the 
great mass of strata along the line of the tunnel consists of micaceous gneisses and mica- 
schists with hornblendic bands, the whole having the characters of the younger gneissic 
series, and very distinct from the older gneiss of the northern portion. f If this latter be 
the central gneiss, the pietre-verdi zone is here absent. 


* Amer, Jour. Science, (3) iii. pp. 1-15, also Chem, and Geol. Essays, pp. 333, 336 and 347. 
7 For full details of this sec.ion see Profil géologique du St. Gothard, etc., par Dr. F. M. Stapff ; Berne, 
1881. 
