22 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 15, 



an angle of 60° or 70° ; it is irregularly jointed, but neither bedding 

 nor cleavage can be distinguished in it. On this rests a series of 

 slightly twisted beds of dark slates, some of them calcareous, others 

 of a more siliceous nature and with some subordinate beds of slaty 

 sandstone, dipping E.N.E. 60° ; at the Petit Ferret the beds form a 

 synclinal axis, up which the footpath runs. From this point to the 

 road up the Grand Ferret, the slates dip N.W. 40°, but on the south 

 side of that pass they dip N.E. 50°*. The anticlinal seen at the 

 Grand Ferret is the continuation of the anticlinal axis mentioned by 

 Professor Forbes, op. cit. p. 21 1, which runs down the whole of this 

 valley, and is continued for a short distance in the lower part of the 

 Allee Blanche. 



The cleavage planes are wavy, but on the whole vertical between 

 the two passes ; on the western side of the Petit Ferret they dip 

 E. 75°, meeting the folia of the gneiss of Mont Dolent in a steep 

 anticlinal, which is the continuation of the axis of cleavage which 

 runs down the valley, a turn of the valley having here separated the 

 axis of cleavage from that of the strata, which coincide lower down 

 the valley. As the arrangement of the cleavage planes is here very 

 nearly in harmony with that of the district, we may infer that the 

 beds have been very little disturbed since their lamination. 



For several miles down the valley there are no stratified rocks on 

 the western side, which is bounded by a steep wall of gneiss, whose 

 foliation dips towards the great chain about 60° ; the strike at the 

 head of the valley is N. or N. 10° E. ; but lower down it follows the 

 prevailing direction of this district, N. 30° E. On the east side of 

 the valley the slates dip steadily about N.N.E. 50°. 



In the lower part of the valley a considerable mass of slate rocks 

 lies on the west side of the valley, forming a low shoulder to the 

 great chain ; the beds all dip towards the gneiss, forming an anticlinal 

 axis with the slates on the opposite side of the valley. Their position 

 is shown in Section 4. I climbed the ravine which bounds Mont 

 Frety on the north side of the village of Entreves far enough to 

 satisfy myself that the slates rest against a steep wall of gneiss. 

 Saussure tells us that he spent a day in the examination of the 

 junction of the schists with the gneiss ; he says, § 872, " Les couches 

 s'appuyent contre la montagne;" § 874, "On voit toujours des 

 schists appliques contre la base des montagnes primitives." 



I was glad to find on my return that my view of the relative posi- 

 tions of the gneiss and slates of Val Ferret was thus confirmed by 

 the testimony of Saussure, since it is in direct contradiction to the 

 account given by Prof. J. Forbes, who throughout his 11th chapter 

 repeatedly asserts that the granite overlies the limestone on the west 

 side of the Val Ferret, especially mentioning the limestone beds of 

 Mont Frety as exhibiting this superposition, pp. 210, 212, 222, and 

 246 f. I can only conclude that this dip of the beds of slate 



* Prof. J. Forbes, op. cit. p. 246, calls all these beds, as well as all the secondary 

 beds of the Val Ferret, limestone. They are principally clay-slates with some 

 subordinate calcareous beds. Saussure describes them minutely, § 862 and 872. 



t Professor A. Sismonda also asserts that the protogine covers the calcareous 



