of Serpentine^ 8(c. in the Apennines. 195 



nines I have described. In the last formation, on the con- 

 trary, the general mass of the rocks is compact, sedimen- 

 tal (sedimenteuse), even arenaceous ; and, whoever has seen 

 both, will have perceived that the real and apparent diflfer- 

 ences are immense. M. Brochant says that the transition 

 rocks of the Tarentaise ought to be regarded as the most 

 ancient of that class ; we assert that if the calcareo-sand- 

 stone of the Apennines is referred to the transition for- 

 mation, it ought to be placed among the most recent of 

 that class. 



These subjects of comparison appear to me suflScient to 

 establish the difference between the calcareo-sandstone rocks, 

 (which, in the part of the Apennines I have described, are 

 beneath the diallage rocks), and the ancient transition rocks, 

 and consequently those only which may be regarded as be- 

 longing to a very distinct epoch. 



If the same rocks are now compared with those I have 

 mentioned under the name of inferior sediment rocks, and 

 which are commonly called secondary Alpine rocks, we 

 shall find many points of resemblance notwithstanding the 

 differences still presented. I shall confine myself to giving 

 as examples the rocks that I have had occasion to visit, and 

 which, as much by the exact comparison which I have been 

 enabled to make, as according to the general opinion of the 

 most distinguished geologists, may with certainty be referred 

 to the true Alpine formation. 



§ III, Comparison of the rocks beneath the Serpentines with 

 the inferior sediment rocks termed Alpine. 



I shall take my first example on the southern side of the 

 Alps, and on the shore of the lake of Como, from the town 

 of Como to Nobialla, towards the middle of the lake and 

 even a little beyond. 



The rocks that border this lake, especially on the western 

 bank, are, towards the base of the hills, a more or less 

 bituminous blackish limestone in numerous beds, generally 



N 



