in the Neighbourhood of Chamounix, in Savoy. 71 



other ; because, up to the present moment, I have been un- 

 able fully to satisfy myself whether these rocks are gneiss or 

 talcose rocks. The component part, consisting of leaflets, 

 often appear harder than talc, and less elastic than mica. 

 It seems intermediate between these two minerals. I be- 

 lieve that there is often true talc associated with the fel- 

 spar, and even that this rock plays as important a part in 

 the protoginous chain of Mont Blanc, as is done by the gneiss 

 in the granite chains. This foliated rock, which is essen- 

 tially composed of felspar and talc or chlorite, has been 

 named felspathic-steaschist by M. Omalius De Halloy ;* but 

 it is so widely diffused among the Pennine Alps as to de- 

 serve a special name ; and that of Dolerine, proposed by 

 M. Jurine,t appears to be the only one that can be adopted 

 to designate it. 



Near the glacier of Trient, I found large aiguilles entirely 

 formed of eclogite. 



During my stay at the Col de Balme, I often examined the 

 formation known by the name of Ponding ue de Valor sine, 

 especially in the locality named Ceblancs, rendered classical 

 by the observations of Saussure {Voyages, cli. xx.). These 

 pudding-stones, in which I have found neither true granite 

 nor limestone, constitute, along with sandstone and argilla- 

 ceous slates, the anthraciferous formation of the Alps. By 

 this name I do not pretend to decide its age, that being still 

 problematical ; nor to assimilate this formation to the an- 

 thraciferous formation of Belgium or the Ardennes. I merely 

 mean, that it contains the anthracites of the Alps, which, as 

 is known, are associated, according to M. Brongniart, with 

 plants of the coal formation.^ Here the formation is inferior 

 to the belemnite limestone ; and these two formations pre- 

 sent a geological j}assage from the one to the other — that is 

 to say, there is an alternation of the rocks of the two forma- 

 tions near the line of contact. 



I have had occasion to verify, in this singular formation. 



* Des Roches conslderecs Mineralogiquement, 1841, p. 70. 

 t Journal des Mines, 1806, t. xix., p. 374. 

 X AnnalcB des Scicn. Nut., t. xiv., p. 127. 



