80 Px'ofessor Favre's Geological Researches 



consented to descend to Qhamounix, greatly disappointed at 

 not being able to verify this slate formation, but satisfied 

 that I had done all with that view that could be reasonably 

 expected. 



Couttet advised me not to give up my object, but to try the 

 ascent again by a ridge which descends from this mountain 

 to the Col de Berara, on the side of Buet.* I determined to 

 follow his advice, resolving at the same time, that if I 

 should again fail, to renew the attempt with a greater num- 

 ber of guides, provided with hatchets, cramp-irons, and ropes. 



For two days I was diverted from my object by other ob- 

 servations, but on the 16th of August, I went from Chamou- 

 nix, and passed the night at Valorsine, and on the following 

 day ascended to Buet. This journey was the more fatiguing, 

 as the bad weather did not allow me to refresh myself on the 

 summit, by enjoying the view. 



In my ascent from the Pierre a Berard to the top of Buet, 

 I found the following formations ; — 



1. Rose protogine, and crystalline slates. 



2. Quartzy sandstone, greenish, with rose-coloured grains. 



3. Quartzy sandstone, of a yellowish colour. 



4. Argillo-ferruginous slate, red and green. 



5. Cargneule, with sulphate of barytes and reddish lime- 



stone. 



6. Slate and limestone slate, with belemnites of great 



thickness. 



I observed that the anthraciferous formation which is re- 

 presented here by the beds, Nos. 2, 3, and 4, as well as the Ju- 

 rassic formation, No. 6, rest, with a discordant stratification, 

 on the crystalline slates which form the base of Buet. Not 

 only did I observe, as was done by Saussure (Voyages, § 555 

 and 556), that the rocks of the secondary formations rest 

 upon masses of crystalline slates, but I also noticed that 

 the crystalline slates were directed to the north or north 

 10°"0, and that the limestone I'ocks and slates were directed 

 to the north 20° or 25° east. Yet I indicate these two direc- 



* This col is situate on a line drawn from the Aiguilles Rouges to Buet, and 

 not on the north of that mountain, ns it is placed on many maps. 



