252 M. A. Guyot on the Distribution of Rocks 



may therefore assert that these rocks belong to the great 

 metamorphic chain which, according to M. Stucler, constitutes 

 the greater part of the enormous masses of the Pennine Alps 

 from the valleys of Bagnes and Entremont, as far as that of 

 Viege and beyond it.* 



With regard to the granular chlorites, or Bagnes rocks, 

 their original site is determined long since. Although de- 

 scending in greatest abundance by the valleys of Bagnes and 

 Entremont, they are found throughout the whole extent that 

 I have indicated, all varying much. They pass by diffei'ent de- 

 gi'ees to slates, more or less talcose, often with a filamentous 

 structure, and they are found under these diverse forms in the 

 southern chain as far as the Haut-A^alais. The arkesine, on 

 the contrary'-, and the chloriteous gneiss, never appear higher 

 than the valley of Viege, which is occupied by the rocks which 

 have descended from the valley of Saas. 



We may join to this group of the Pennine rocks, properly 

 so called, that of the rooks of Mont Rosa, which likewise 

 contains three species particularly characteristic. 



4. The Euphotidcs of Saas are here placed in the first 

 rank. This beautiful rock, whose varieties, more or less rich 

 in Saussurite, Smaragdite, and yellow or white talc, are very 

 numerous, is distinguished from the rare euphotides or gra- 

 nitones of the basins of the Isere and Rhine. It is spread 

 over almost the whole surface of the basin of the Rhone, 

 and is, notwithstanding, known to be derived from the valley 

 of Saas alone. It descends the higli ridges of Saasgrat by 

 one route, the glacier Alalein, behind which I could not per- 

 ceive a single fragment. This exclusive origin, joined to its 



* These conclusions have been fully justified, and placed beyond all doubt, 

 by my investigations last summer (18i6). I traversed the whole high chain 

 of the Pennine Alps, still so little known, from Mont Blanc to Mont l\osa. I 

 either reached or crossed the ridge at five different points. I examined the 

 bottom of all the valleys on the northern side, from the valley of Bagnes to that 

 of Saas, as well as a part of those on the southern slope ; and I had the great 

 satisfaction of discovering at last, in these almost inaccessible pealiS, the pre- 

 cise site of all the characteristic rocks of the erratic basin of the Rhone which 

 are here enumerated, and to collect them in situ, I shall give an account else- 

 where of the result of these researches, which complete the scries of my studies 

 on the Swiss erratic formation, — See p. 319. 



