635 



kalk (limestone of Gottingue), and the salife- 

 rous and bituminous clay of Araya as repre- 

 senting variegated sandstone; but these pro- 

 blems can only be solved when the mines of 

 those countries are worked. Some geognosts, 

 who believe that the gemsalt of Italy penetrates 

 into a soil above the jura limestone, and even 

 chalks, may be led to take the limestone of 

 Penas Negras for one of the layers of compact 

 limestone, destitute of grains of quartz and 

 petrifications, which we meet with frequently 

 amidst the tertiary agglomerate of Barignon, 

 and of Castillo de Cumana ; the saliferous clay 

 of Araya, would appear to them analogous to 

 the plastic clay of Paris*, or to the clayey 

 shelves (dief et tourtia) of secondary sandstone 

 with lignites, which contain salt-springs, in Bel- 

 gium and Westphalia "f-. However difficult it 

 may be to distinguish separately the layers of 

 marl and clay belonging to variegated sand- 

 stone, muschelkalk, quadersandstone, jurassic 

 limestone, secondary sandstone with lignites 

 (green and iron sand), and to the tertiary soil 

 above chalk, I believe that the bitumen which 

 every where accompanies gemsalt, and most 



* Tertiary sandstone' with lignites, or molassus of Ar- 

 govia. 



t Manuscript notes of MM. Dechen and Oeyhausen (See 

 also Buff, in Noggerath, Bheinland Westph. Vol. iii, p. 53). 



