192 M. Br oKGN I ART 07i the position 



those of Bristol ;* those of the environs of Cherbourg, which 

 I have described, and which are composed of yellowish and 

 not effervescent argillaceous slate, clay slate, aluminous 

 slate, felspathic and granitic rocks, &c. those of the environs 

 of Angers, which principally consist of a spangled clay 

 slate, containing organic remains, but not effervescent; all 

 these rocks, I say, compared with the calcareo-sandstones 

 of the Apennines, present numerous and striking differences. 



Even in the Pyrenees, the black spangled slates with 

 vegetable impressions, and the brownish and micaceous 

 schistose sandstones of the port of Gavernec, which some 

 geologists refer to the transition series, possess an exterior 

 aspect, a colour, a general disposition which distinguishes 

 the arenaceous and slaty rocks of the Apennines ; and what 

 is still more remarkable is, that in the Pyrenees, notwith- 

 standing the vicinity of these rocks and the calcareous for- 

 mation, none of them effervesce, whilst all those of the 

 Apennines that may be compared to them are mixed with 

 carbonate of lime. 



If we draw nearer the countries which contain the sub- 

 ject of our observations, taking as an object of compari- 

 son the Tarentaise in the chain of the Alps, a transition 

 country rendered classic by the learned description M. Bro- 

 chant has given of it, we find, notwithstanding the prox- 

 imity of the places, but very few points of resemblance. 

 The general mass of rocks in the Tarentaise is crystallised 

 or granular ; the striped schist of la Magdeleine, the base of 

 which is compact, is traversed by crystalline limestone in 

 every direction ; the only limestone of a compact appearance 

 there noticed, is that of the Bonhomme, which, by its 

 yellowish white colour, by the fineness of its grain, which 

 renders it almost translucent, by the remarkable presence of 

 felspar and quartz, and in the disseminated crystals it con- 

 tains, is considerably removed from the compact limestone 

 that is seen beneath the serpentines in the parts of the Apen- 



■ *y It has been stated in a former note that the Bristol rocks do not 

 belong to the submedial or transition class. [Translator.) 



