Granitic Rocks of Mont Blanc. 121 



Blanc, considered geologically, it would appear then must 

 be referred to the talcose formation of the Alps. 



I mention these rocks under the name of talcose rocks, 

 and not under that of serpentine, because I consider that 

 they cannot, in many respects, be identified with the ser- 

 pentine rocks observed elsewhere. 



What appeared to me certain is, that they possess very 

 great differences which separate them from granites, and 

 from the relations tkey bear to serpentine rocks, one is in- 

 clined to presume that they are not the most ancient of the 

 primitive class. But until their junction with rocks that 

 are essentially different, has been observed in a positive 

 manner, their epoch of priority cannot be definitively as- 

 signed them. 



No doubt we might be compelled to form groupes in the 

 midst of these rocks, and to consider separately some mem- 

 bers of this formation ; but we have not as yet sufficient ob- 

 servations to establish these subdivisions. 



I have only spoken of the rocks of Mont Blanc, but I 

 might extend my conclusions to many other granitic rocks 

 of the high Alps, which almost always bear a great analogy 

 to those of Mont Blanc, according to all observers; those I 

 saw at St. Bernard are altogether referable to them : it is the 

 same with many other mountains which follow this last, 

 ascending nearly to Mont Rosa. 



This resemblance of numerous granitic rocks of the Alps 

 to a talcose rock, and of the formations containing them to a 

 talcose formation, is founded on a long examination, and 

 continued comparison of the rocks of the Alps, less in col- 

 lections, than in nature ; and it very well accords with the 

 conjectures that I have above brought forward as to the re- 

 lative antiquity of the greater part of the primitive rocks of 

 the Alps, In fact, if I have before confined myself to sus- 

 pecting the validity of the titles on which were founded the 

 perogative of antiquity which was accorded to Mont Blanc 

 and the other summits of the Alps, it will be found that I at 

 present destroy that perogative, at least according to received 

 geological ideas, by taking their granite away from them, 



