332 THE GEOLOGY OF THE ALPS. [XIV. 



lished by the discovery of Favre that their position is inter- 

 mediate between the carboniferous and the strata containing 

 Avicula contorta (the Kossen beds, or the Rhsetic beds of 

 Giimbel), which are recognized as forming a passage between 

 the trias and the lias, at the base of the Jurassic system. To 

 these, to the northwest of Mont Blanc, succeed the higher 

 members of the system, followed by the neocomian, the creta- 

 ceous, and the nurnmulitic strata of the eocene, with overlying 

 sandstones and shales, the flysch of some Alpine geologists. 



Few questions in geology have been more keenly debated, or 

 given rise to more often-repeated examinations, than the asso- 

 ciation of a carboniferous flora with liassic belemnites in the 

 districts of Maurienne and Tarentaise, to the southwest of 

 Mont Blanc. As seen at Petit-Co3ur, the schists, with impres- 

 sions of ferns and beds of anthracite, were so long ago as 1828 

 described by Elie de Beaumont as apparently intercalated in 

 the Jurassic system. Scipion Gras, and Sismonda after him, 

 have agreed in regarding the rocks as constituting one great 

 system, which according to Gras is of carboniferous age, but 

 with a Jurassic fauna ; while De Beaumont and Sismonda, on 

 the contrary, regarded it as of Jurassic age, but with a carbon- 

 iferous flora, and imagined that by some means there had been 

 in this region a local survival of the vegetation of the palaeo- 

 zoic period. These conclusions were accepted by many geolo- 

 gists, though rejected by not a few. A brief account of the 

 controversy up to that date will be found in the American 

 Journal of Science for January, 1860, page 120; and in the 

 work of Favre now before us the whole matter is discussed at 

 great length in Chapter XXX. The anthracitic system of the 

 Alps, as recognized by Gras, was by him estimated to have a 

 thickness of from 25,000 to 30,000 feet, and included, besides 

 the dolomites and gypsums now referred by Favre to the trias, 

 coal-plants and layers of anthracite, together with limestones 

 holding belemnites of Jurassic age. Included in this great 

 system were, moreover, gneissic, micaceous, and talcose rocks, 

 with graphite, serpentine, euphotide, etc., all of which were 

 regarded by Gras as formed by the local alteration of portions 



