259 



reous breccia, and very recent compact lime- 

 stone, which is found united at the western 

 extremity of Punta Araya, as well as at the 

 castle of St. Antonio at Cumana. We have now 

 to speak of a fourth formation, which probably 

 reposes * on the calcareous sandstone of Araya, 

 I mean the muriatiferous clay. 



This clay, hardened, impregnated with petro- 

 leum, and mixed with lamellar and lenticular 

 gypsum, is analogous to the salzthon, which in 

 Europe accompanies the sal gem of Berchtesga- 

 den, and in South America -f- that of Zipaquira. 

 It is generally of a smoke gray color, earthy, 



* I would wish mineralogical travellers, to examine 

 more particularly the Cerro de la Vela. The lime-stone of 

 the Pennas Negras reposes on a slate-clay, mixed with 

 quartzose sand ; but there is no proof of the muriatiferous 

 clay of the salt works being of a more ancient formation than 

 this slate.clay, or of it's alternating with banks of sand-stone. 

 No well having been dug in these countries, we can have no 

 information respecting the superposition of the strata. The 

 banks of calcareous sand-stone, which are found at the 

 mouth of the salt lake, and near the fishermen's huts on the 

 coast opposite Cape Macano, appeared to me to lie beneath 

 the muriatiferous clay. 



f- Near Santa Fe de Bogota, this formation of muriatiferous 

 clay, long neglected in the systems of geognosy, characterizes 

 the gem salt more than the ancient secondary gypsum (aelte- 

 rer Flozgyps) which reposes on the zechstein, or Alpine cal- 

 careous stone, as I have shown in 1798, in my work on the 

 Moffettes of the Mines. (Ueber die unterirdischen Gasarten, 

 p. 143.) 



