in the Neighbourhood of Chamounix, in Savoy. 81 



tions with doubt, since I reperused the paragi'aphs in the 

 Voyages refei'red to above, in which Saussure says, that the 

 crystalline slates and .the secondai'y rocks, lie in the same 

 direction. This is an observation, therefore, which deserves 

 to be verified. 



If the fact of the nonconformity of these two formations 

 be correct, it is new and important in the geology of Savoy, 

 although it has already been observed in Dauphiny, * and 

 M. de Charpentier has noticed it in the Valais, on the right 

 bank of the Rhone. t This observation is particularly im- 

 portant in the history of the anthraciferous formation. It 

 proves that it is independent of the crystalline slates. We 

 likewise know that it is sepai'ated from the Jurassic forma- 

 tion by this same character of discordancy! which is the 

 greatest that geognosy can furnish. 



I redescended the Buet by the Col de Salenton (2532 

 metres, by barometer) where the formations present, with 

 great distinctness, the same section as that which I have in- 

 dicated at the Buet, except that we may here observe in this 

 anthraciferous formation a thin bed of slate, placed between 

 the sandstone and red and gi'een argillo-ferruginous slate. 

 This bed is probably the same which, near De Moide, con- 

 tains such a large number of vegetable impressions. 



By following, as I afterwards did, the western slope of the 

 elongation of the chain of the Aiguilles Rouges, formed by 

 Mont Loguia, Gros Perron, Bel-Oiseau, &c., we find a series 

 of cols placed, like that of Salenton, between the ci'ystalline 

 chain and the secondary chain. These are the Col des Vieux 

 Emoussons, Col de Barberine, Col de Emmaney, and Col du 

 Salentin. All are exactly on the limit of the two orders of 

 formation, and present sections very nearly identical, 



I passed a most uncomfortable night in the frightful chalets 

 of Villy (1879 metres, by barometer) ; and on the following 

 day Couttet and I set out for the highest peak of the Aiguilles 



* My memoir, entitled Remarks on the Anthracites of the Alps, p. 17 ; Mem. 

 lie la iiac. de Phjs. et d'llist. Naturelle de Geneve, t. ix. p. 425. 



t Charpentier, Memoir on the Nature and Position of the Gypsum at Bex, 

 Annales des Mines, 1819. 



I Observations on the relative Position of the Formations of the Alps, &c. 

 Archives, 1847, t. vi. p. 121. 



VUL. XLV. NO. LXXXIX. — JULY 1818. P 



