108 



we here repeat, not the transition from one rock 

 to another, but the geological affinity existing 

 between two formations. According to the ge- 

 neral type* of the secondary strata, recognised 



longing to the Alpine limestone, lies under the Jura lime- 

 stone, which forms Mount Saleve. 



* The succession of secondary formations seems to be on 

 the continent as follows, when they are all equally deve- 

 loped ; that is to say, when none of them are either wanting, 

 or involved in the neighbouring formations. 1°. Ancient 

 sandstone, lying on transition slate (alter sandstein, todes 

 liegende). 2°. Alpine limestone (alpenkalkstein, zechstein). 

 3°. Ancient gypsum (salzgyps). 4°. Jura limestone (jura- 

 kalkstein). 5°. Sandstone of the second formation, Molasse 

 (bunter sandstein). 6°. Fibrous gypsum (neuer gyps). 7°. 

 Limestone of the third formation (muschelkalkstein of Wer- 

 ner). 8°. Chalk. 9°. Limestone with cerites. 10°. Gyp- 

 sum with bones. 11°. Sandstone. 12°. Fresh water forma- 

 tion. We shall often have occasion to recur to this type, 

 the complete knowledge of which seems to be the principal 

 object of geognosj', and upon which accurate ideas have been 

 begun to be formed only within these twenty years. We 

 shall merely observe here, that the last formations, 8, 9, 10, 

 11, 12, examined with so much care by Brogniart and Cu- 

 vier, are wanting in a great part of Europe ; that the lime- 

 stones 2 and 4 often form only one mass; and that in 

 every place, where the two formations of gypsum (3 and 6) 

 are missing, the order of secondary rocks is reduced to the 

 very simple type of two sandstone formations alternating with 

 two calcareous formations. To account for a great number of 

 phenomena of superposition, which appear very singular at 

 first sight, we must recollect the two following laws, founded 

 upon the analogy of well observed facts $ 1°. When two 



