74 Professor Favre's Geological Researches 



de Martigny, as far as Mont de Lacha, near Ouches. This 

 junction is seen in a very great number of localities, among 

 others, on the right side of the glacier of Bois, on the road 

 leading to Chapeau, at a place called Bouchet. In this lo- 

 cality, the beds of which are nearly a pi'olongation of those of 

 the sides of Piget,* the fan-shaped structure is striking, the 

 beds inclined, as pointed out by M. Forbes,! about 30° south- 

 east ; the crystalline slates appear to dip under the crystalline 

 rocks, and to rest on the limestones, whose beds present the 

 same inclination. At the boundary of the crystalline slates 

 and the limestone, we find the cellular magnesian limestone, 

 named Cargneule, and between the Cargneule and the crystal- 

 line schist is found a thin layer of a white or greenish sort of 

 kaolin. This arrangement is seen along the whole line of 

 contact. I have also found it at the torrent of La Gria, at 

 the Col de Balme, &c., &c. 



As in the regular order of formation, tlie anthraciferous 

 formation is placed below the Jurassic formation, and since 

 we nowhere see this formation between the crystalline 

 slates and the limestone on this side of the chain, I have 

 thought that it is not the lower portion of the Jurassic for- 

 mation which is found in contact with the crystalline schists. 

 This absence of the anthraciferous formation seems to ex- 

 clude the possibility of explaining the fan-shaped structure 

 by the overturning of the beds resulting from the force and 

 nature of the rising upwai'ds of the crystallised rocks. I 

 know, however, that it is not thus throughout the whole cir- 

 cumference of the chain of Mont Blanc. In the Vale of 

 Ferret, for example, the Jurassic limestones rest upon the 

 crystalline .slates, and on the massive rocks. They ap- 

 pear to be in a normal position, and the fan-shaped structure 

 does not exist. This belief, therefore, as to the superposi- 

 tion of the crystalline slates on the upper part of the Juras- 

 sic formation, needs to be confirmed. With this object I 

 examined the line of junction of the Jurassic formation and 

 of the Brevent chain, in a locality frequently visited, named 



* De Saussure, Voyages, § 709. 

 t Travels, p. 63 and 66. 



