184 . M. Brongniart on the position 



Thus the serpentine formation is no more covered here 

 than elsewhere. The rock on which it rests is certainly 

 not seen ; but the analogy of its structure and composition 

 with those I have described, lead me to presume that it be- 

 longs to the same epoch of formatiouj and that it is, like 

 them, posterior to the alpine limestone, such as I have des- 

 cribed it. 



To these rocks of serpentine that I have visited, I con- 

 sider myself able to add, as referable to the same epoch of 

 formation : — 



The serpentine of the mountain of Dragnon on the side of 

 Sasseto, in eastern Liguria, described by M. Viviani ; it is 

 so near the position of Rochetta, and the characters given 

 by this naturalist are so like those of the Rochetta serpen- 

 tine, that I have no doubt but that they belong to the same 

 formation : 



The serpentine of the mountain of La Guardia, on the 

 N. of Genoa, described by Saussure. I regret not being able 

 to visit this position ; for, from the description of Saussure, 

 it would appear, that the jasper is here replaced by red slate, 

 and that the grey alpine limestone, alternating with marly 

 limestone, found immediately under the serpentine, is strati- 

 fied unconformably to the calcareous slate, and the blackish 

 limestone traversed by spathose veins, which appears near 

 Genoa, and near the borders of the sea, and which affords, 

 better than all the limestones of this canton, the characters 

 of a transition rock. Now this discordance of stratification, 

 is, if not a certain, at least a very probable indication of 

 different epochs of formation. 



Every thing then coincides in shewing that the serpentine 

 formation of the Apennines, far from being beneath the tran- 

 sition schists, as some celebrated geologists have imagined ; 

 far from belonging to the primordial formation ; far even 

 from closely following and being either a last member of 

 that formation, or one of the most ancient rocks of the tran- 

 sition series, as has been said by Messrs Von Buch, Faujas, 

 Viviani, Cordier, Cortesi, Brocchi, and perhaps all geolo- 



