86 M. Brochant on the 



3. There also exist in the Alps many deposits entirely 

 superficial, most frequently in isolated masses of little ex- 

 tent ; these gypsums most frequently rest on a formation of 

 transition argillaceous slate or anthracite (as in the Taren- 

 taise or AUee blanche) ; sometimes on transition limestone 

 (as at Pesey and elsewhere in the Tarentaise ; lastly, even 

 on primitive rocks (as at the Val Canaria ) ; many have an 

 analogous appearance to a deposit in basins. 



I am fully sensible, that it will be necessary to determine 

 in a more precise manner the geological relations of those 

 last gypsums that are met with on the surface. 



But I confess that I am not in possession of sufficient 

 data to resolve this question completely. 



In the first place, these gypsums do not contain any fo- 

 reign rock; at least I do not know of any ; and they are not 

 covered by others. They bear many mineralogical resem- 

 blances to the transition gypsums ; they often rest on transi- 

 tion rocks ; I am acquainted with a locality (near Bex, in 

 the direction of the mountains on the N.E.) where they 

 almost form a continuation of the decided transition gyp- 

 sum, and for an extent of many leagues, except with some 

 interruptions. 



One would be led to imagine that these superficial gyp- 

 sums were posterior to the former^ but that they equally 

 belonged to the transition series ; that gypsum was deposited 

 at different times during this period of formation, so that 

 the first deposit was in the heart of the series, and the latter 

 on its surface, without however shewing itself associated 

 with rocks of later formation. But on the other hapd, these 

 same superficial gypsums of the Alps, bear many resem- 

 blances to the ancient secondary gypsums observed in Bava- 

 ria, Salzbourg, Thuringia, and elsewhere. The latter are 

 also for the most part equally white ; they contain like the 

 former, anhydrous sulphate of lime, rock salt, and saline 

 springs : they are frequently close to fetid limestone, which 

 is not rare in the transition rocks of the Ajps ; in a word, 

 there is but one difference between them, but that is in 

 truth important ; it is, that they rcbt on secondary rocks, 



