Vol. 52.] lustres' of mont jovet (savoy). 11 



Conclusions. 



It is contended, on the evidence above cited, that Lor}- and Zaccagna 

 were right in identifying the central rocks of lEont Jovet as ' schistes 

 lustres,'" for this conclusion is supported by their lithological cha- 

 racters and the nature of the igneous rocks associated with them, 

 and is not opposed to their stratigraphical relations. 



It is further shown that the schists in question are older than 

 the Trias (1) by the occurrence of fragments of the schists in the 

 Trias ; (2) by the discordance of strike between the two series ; 

 (3) by the occurrence of masses of dolomite resting unconformably 

 on the flanks of the schists; and (4) by the fact, that the Trias 

 has escaped the metamorphism which the schists have undergone. 



The probabilities are all in favour of the schists occupying the 

 same relation to the Carboniferous as they do to the Trias ; while 

 the close approximation of the schists to the former show that the 

 schists are not the altered representatives of the Carboniferous. 

 We must therefore conclude that the ' schistes lustres ' are pre- 

 Carboniferous, but evidence by which finally to assign them to any 

 exact horizon before this date is still wanting. 



Discussion. 



Prof. Bonnet expressed his sense of the great value of Dr. 

 Gregory's paper, which he regretted had been pushed into a corner 

 by the time which he had been obliged to take up for his own. 

 From his general knowledge of the district and intimate acquaintance 

 with other parts of the Alps, he had no doubt that Dr. Gregory was 

 quite right in his interpretation, and that the crystalline schists, 

 often called the ' schistes lustres,' were certainly pre-Carboniferous, 

 and probably much older. 



Dr. Dc Riche Preller fully agreed with Prof. Bonney's remarks 

 as to the great importance of the subject dealt with in the paper, 

 and was gratified to see that the Author substantially endorsed the 

 views of Zaccagna, who had done so much excellent work in the 

 Western Alps from 1887 to 1889, and, by extending the survey on 

 the Italian side for fully 30 miles into the Vanoise district in 

 Savoy, as far as the valley of the Isere, had conclusively shown that 

 Lory's views as to the Upper Triassic age of the calcareous schists, 

 or ' schistes lustres,' were utterly untenable, and, further, that the 

 bulk of the mica-schists referred to by Termier as Permian are also, 

 like the ' schistes lustres,' pre-Carboniferous — indeed, of Archaean 

 age. The speaker had visited the Savoy district some years ago, and, 

 in his opinion, the occurrence in the central mass of Mont Jovet of 

 serpentine, gabbro, and so-called green Alpine marble (as quarried 

 near the summit), under conditions strictly analogous to those on 

 the Italian side near Susa, and also in Liguria, affords a strong 

 argument in favour of the Savoy ' schistes lustres ' being, like those 

 of the Italian localities, of Archaean age. 



The Author replied, thanking the Fellows for their reception of 

 his paper. 



