STRATA OF MURIATIFEROUS CLAT. 395 



gularity of the inclination of its strata, and its parallel 

 position with the two declivities of the Hartz and the 

 upheaved chain of the Alps; while the simultaneous presence 

 of sulphur, oligist iron, and the sulphurous acid vapours 

 which precede the formation of sulphuric acid, seem to 

 manifest the action of forces placed at a great depth in the 

 interior of the globe. 



XI. FORMATION OF MURIATIFEROUS CLAY (WITH BITU- 

 MEN AND LAMELLAE GYPSUM) OF THE PENINSULA OF 

 ARAYA. This soil presents a striking analogy with salzthon 

 or leberstein (muriatiferous clay), which I have found accom- 

 panying gem-salt in every zone. In the salt-pits of Araya 

 (Ha'raia), it attracted the attention of Peter Martyr 

 d'Anghiera, at the beginning of the sixteenth century. It 

 probably facilitated the rupture of the earth, and the forma- 

 tion of the gulf of Cariaco. This clay is of a smoky colour, 

 impregnated with petroleum, mingled with lamellar and 

 lenticular gypsum, and sometimes traversed by small veins 

 of fibrous gypsum. It incloses angular and less friable 

 masses of dark brown clay, with a slaty and sometimes con- 

 choidal fracture. Muriate of soda is found, in particles 

 invisible to the naked eye. The relations of position or 

 superposition between this soil and the tertiary rocks does 

 not appear sufficiently clear to enable me to pronounce with 

 certainty on this element, the most important of positive 

 geology. The co-ordinate layers of gem-salt, muriatiferous 

 clay, and gypsum, present the same difficulties in both hemi- 

 spheres ; these masses, the forms of which are very irregular, 

 everywhere exhibit traces of great commotions. They are 

 scarcely ever covered by independent formations ; and after 

 having* been long believed, in Europe, that gem-salt was 

 exclusively peculiar to Alpine and transition limestone, it is 

 now still more generally admitted, either from reasoning 

 founded on analogy or from suppositions on the prolongation 

 of the strata, that the true location of gem-salt is found in 

 variegated sandstone (buntersandstein). Sometimes gem- 

 salt appears to oscillate between variegated sandstone and 

 muschelkalk. 



I made two excursions on the peninsula of Araya. In 

 the first, I was inclined to consider the muriatiferous clay 



