﻿xlviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



invented of a more plausible kind, unless we escape from the diffi- 

 culty by explaining away what is called ft physical evidence " or the 

 " order and position of the beds." It is conceded on all hands that 

 in no region of the globe, hitherto studied by geologists, has the 

 original arrangement of strata been subsequently so much altered by 

 complicated foldings and dislocations, and by metamorphic action, 

 which last has sometimes superinduced a crystalline structure on older 

 formations, while those of newer date retain their ordinary mineral 

 condition. 



In a district of such chaotic confusion, we may well despair of being 

 able to trace out the true chronological sequence of fossiliferous groups, 

 and we therefore hail with pleasure the discovery of an undisturbed 

 region not very remote, where strata wearing the same mineral and pa- 

 Iseontological aspect occur. It appears that recently, in 1850, the two 

 Italian professors, Meneghini and Savi, have detected near Yolterra 

 anthracitic schists containing coal plants like those of the Alps, such 

 as Pecopteris arborescens and Annularia longifolia, on which beds of 

 lias with the ordinary marine shells repose. These schists belong to the 

 Verrucano or oldest conglomerate of Italy, which, so long as no fossils 

 were obtained from it, had been regarded in Tuscany as the base of the 

 lias, but which will henceforth be classed as a carboniferous con- 

 glomerate and schist supporting the Jurassic series. Such facts seem 

 to have a direct bearing on the enigmatical question of Petit- Cceur, 

 from the circumstance that in many parts of the Alps, as in the 

 well-known instance of the Valorsine, which I have myself exa- 

 mined, the plant-bearing schists are associated with a conglomerate 

 doubtless analogous to the Verrucano. This fact Sir Roderic Mur- 

 chison and Professor Heer have remarked, when commenting on the 

 statements of Signori Meneghini and Savi*. We have merely then 

 to imagine, that in the Tarantaise Alps, as in Tuscany, Jurassic strata 

 were first thrown down on horizontal coal-measures, and that in the 

 Tarantaise these were afterwards crumpled and folded together by 

 more than one series of movements, which extended in the central 

 Alps, as we know, even to the cretaceous and eocene deposits. When 

 we consider that occasionally the Permian group is wanting in Eng- 

 land, and the Muschelkalk universally, we ought not to be surprised 



* Quart. Journ. Geol. Soc. vol. vi. p. 382 ; and Heer, Mittheilungen der Naturf. 

 Gesellsch. in Zurich, January 1850. 



