218 Successive Geological Development. 



of organic forms to particular eras, shakes every theory 

 which rests on purely pal aeon tological data to its very foun- 

 dation. In the year 1828, M. Adolphe Brongniart published 

 an account of twenty-five species of fossil plants from Petit- 

 CcEur, twenty of which he was able to identify with carboni- 

 ferous species, M. Elie de Beaumont having found this as- 

 semblage of fossils in shales so intercalated with Jurassic 

 schists containing Belemnites (the strata containing the 

 plants and the Belemnites being parallel and conformable), 

 as to lead him to infer that they were all parts of one for- 

 mation. The dark shales containing Belemnites were recog- 

 nized as a portion of certain adjacent rocks, in which Am- 

 monites and other fossils characteristic of the Jurassic series 

 abound. Other able geologists afterwards visited the spot, 

 and at the meeting of the French geologists at Chambery in 

 1841, they confirmed the views previously announced by M. 

 de Beaumont. M. Favre, however, endeavoured to explain 

 the anomaly by supposing that true carboniferous schists, 

 originally underlying liassic strata, had been thrown to- 

 gether with them into a sharp anticlinal flexure, portions 

 of which had been subsequently denuded; and he pointed 

 out that in another part of the Alps similar schists, contain- 

 ing coal plants, constitute the conformable base of the liassic 

 group.* Sir Roderick Murchison visited Petit-Coeur in the 

 course of his Alpine excursions in 1847 and 1848, and gave 

 a section shewing that the plant-bearing anthracitic schists 

 can be traced within one foot of the parallel dark shales con- 

 taining Belemnites ; and, to cite his own words, " the Be- 

 lemnite and plant beds form parts of the same geological 

 mass, the upper and lower parts of which are of similar com- 

 position, consisting of talcose schist and sandstone. In fact 

 I cannot imagine how any geologist can look at this section, 

 and not declare that the whole of these strata form a natural 

 group of very small dimensions." t He also affirms, " that 

 if, by a modification of the flexure theoretically suggested by 

 M. Favre, we could get over the difficulty, the section at 



* Bulletin Soc. Geol. de France, vol. v., p. 263. 

 t Quart. Journ. Geol. Soc, vol. v., p. 177. 



