-6 THE f SCHISTE8 LUSTRES ' OF MONT JOVET (SAVOY). [Feb. 1 896. 



of limestones sometimes massive, sometimes passing into calc-schists, 

 the beds of which are separated by beds of crushed phyllites ; 

 2nd, gritty quartzites and irregular quartzitic schists ; and 3rd, talcose 

 lustrous schists. These three sets of rocks occupy the whole of the 

 central part of the mountain, including the summit of Mont 

 Jovet and the four subordinate peaks, namely, the Grande Cote 

 (2543 metres), La Cote (2058 m.), Mont des Arrhets (2440 m. and 

 2492 m.), and the ridge including the 2272 and 2370 metre-points 

 north of Mont Jovet, between the upper valleys of Nant de Thionet 

 land the Yallon des Frasses. The main problem is the relation 

 of this group of rocks to the Trias upon its margin. 



The position of the junction of the Triassic limestones and the 

 rocks of this central series, or, as we may at once, for convenience, 

 call them, the ' schist series,' can be easily determined to within a 

 few yards. The actual junctions, however, are hidden. I did not, 

 in fact, find a single case where, in a clear cliff-section, the actual 

 superposition of the two could be seen. In several points, as at the 

 junction of the gypsum and the schists in the hollow between the 

 2067 metre-point and the western end of the Mont des Arrhets, it 

 certainly appears as if the Trias underlay the schists ; for the 

 apparent dip in the gypsum is to the south-east, and under the 

 schists. It is not, however, certain that this bidding in the gypsum 

 is true stratification ; but even if this be so, the apparent super- 

 position can be explained as due to an overfold, or to the subsidence 

 of the limestones, owing to the solution of the gypsum along lines 

 of drainage. The latter cause has certainly rendered the apparent 

 dip in the gypsiferous beds very unreliable. 



The most instructive case illustrating the relation of the two 

 series was found a little to the north-west of the western end of the 

 Mont des Arrhets. There occurs a hummock of the gypsiferous 

 part of the Trias, marked on the map as the 2067 metre-point. The 

 stratigraphical relations of this mass are clear, for the junction 

 between it and the schists can be traced all round, excepting for a 

 few yards on the north-eastern side. The evidence is sufficient to 

 show that this hillock is simply a mass of the Trias, left as an out- 

 lier on the flanks of a slope of schists. 



The relations of this Trias are illustrated by the accompanying 

 sketch (fig. 2). The fir-covered boss in the centre is the 2067 m. 

 point ; the lower knoll to the left (the 1894 m. point) is the upper 

 termination of the main outcrop of the Trias. On the extreme 

 right is a low cliff of schist, which is part of the western end of the 

 Mont des Arrhets. The schists can also be seen in some low crags 

 on the eastern side of the valley, to the right of the 1894 m. hill. 

 They can moreover be traced over the whole of the grassy slope from 

 the end of the Mont des Arrhets, round the southern side of the 

 2067 metre-boss, to the valley to the west, and thence up the lower 

 part of the slope of the 1894 m. point. Fortunately, the ground 

 on the southern side of the 2067 m. point is moutonnee, and the 

 crests of the ridges either just reach the surface, or can be exposed 

 with but little trouble. It is thus possible to prove that the schists 



