in (he Neighbourhood of Chamounix, in Savoy. 83 



self made it separately, so that this number, added to the 

 barometrical height which I took, gives the height of the 

 Aiguille, without there being any other cause of error than 

 that arising fx'om the barometer. This total height, or ele- 

 vation of the summit of the Aiguilles Rouges above the level 

 of the sea, is 2944 metres. 



A geological examination of these 16 metres could give 

 me no farther knowledge, the rocks being entirely formed of 

 the same limestones on which I was walking, and which I 

 could examine at my ease. 



The following is a brief view of the observations which I 

 made on this extraordinary formation, and which had never 

 been examined by any of the numerous naturalists who have 

 visited this country. 



1. The most elevated part is formed by various calcareous 

 slates. They are blackish, containing beds of ferruginous 

 limestone, and a species of homstone. Others are yellow- 

 ish, and impregnated with a talcose matter, either more or 

 less argillaceous and kidney-shaped. They contain frag- 

 ments of belemnites, ammonites, and stalks of encrinites. 

 There can be no doubt that these beds belong to the Jurassic 

 formation. They are about 34 metres in thickness. 



2. Below, are found black slates and greyish-blue lime- 

 stone, traversed by veins formed of quartz and calcareous 

 spar ; further down we meet with cargneule. The two 

 former of these rocks are about 4 or 5 metres in thickness. 

 The thickness of the cargneule cannot be measured, but it 

 is only a few metres. I have not found distinctive characters 

 to induce me to refer these beds to the Jurassic formation 

 rather than to the anthraciferous formation. 



3. The anthraciferous formation, formed by red and green 

 argillo-ferruginous slates, and quartzy sandstone. The thick- 

 ness is 9 metres. 



4. Crystalline slates of a wine and green colour, which 

 are in vertical beds, and on which the preceding beds lie, 

 with a non-conforming stratification, that is, if we regard 

 the divisions of the crystalline slates as being <an indication 

 of stratification. 



The calcareous beds which form the most elevated peak 

 of the aiguille are horizontal ; tho. beds of the anthracife- 



