in the Erratic Basin of the Bhone. 253 



gi*eat diffusion, rendex's it of much value for distinguishing 

 the basin of the Rhone from contiguous basins. 



5. The Edogites, faithful companions of the euphotides, 

 and not less characteristic, also come exclusively from the 

 same localities. The base of this rock seems to be a sort of 

 granular amphibolite, of a gi-eyish-green, imperfectly slaty, 

 sprinkled regulai'ly with small grains, from one to four 

 millimeters in diameter, so numerous that they form an essen- 

 tial part of the rock, and with brilliant spangles of silveiy 

 mica, likewise numerous, of the same size, and remarkable 

 for their regular distribution and generally rounded form. 

 This rock, as widely distributed as the euphotide in the form 

 of pebbles and small blocks, is seldom found in blocks of 

 large size, although it descends, like the euphotide, by the 

 glacier Alalein ; I have likewise found it to the west of Saas- 

 grat, in the moraines of the glacier of Finnelen. 



6. The Serpentines, compact and slaty, belonging to the 

 mass of Mont Rosa, may be ranked among the rocks 

 characteristic of this great Pennine chain, and of the basin 

 of the Rhone. For, although it may be alleged that some of 

 them are likewise found in the neighbouring basins of the 

 Arve and Isere, they will always afford distinct indications, 

 by their particular varieties, abundance, and association with 

 rocks of a less questionable origin than themselves. 



The two preceding groups represent, in the plain, the great 

 central or Pennine chain ; the following species essentially 

 represent the lateral masses of Mont Blanc and of the Ber- 

 nese Oberland. 



7. The granites of the basin of the Rhone, forming gigantic 

 blocks scattered on the declivities of the Jura, and which 

 having been the first to attract the attention of the leai'ned 

 world, it is natural that they should have been considered 

 as the principal and most characteristic rock of this basin. 

 Such, however, is not the case ; for not only are they less 

 generally diffused than the Pennine rocks, but some of them 

 are common to it with the basin of the Arve, and others are 

 very analogous to those of the basin of the Aar. 



These granites are essentially of two sorts. 



One of them has a base of white felspar, sometimes very 



