CA^USTONE FORMATIONS. 373 



diately covers the sandstone of Calabozo, which appeared to 

 me, on the spot, to be identical with our red sandstone, 

 I am uncertain of the age of its formation. The secondary 

 rocks of the Llanos of Cumana, Barcelona, and Caracas, 

 occupy a space of more than 5000 square leagues. Their 

 continuity is the more remarkable, as they appear to have 

 no existence, at least on the east of the meridian of Porto 

 Cabello (70 37') in the whole basin of the Amazon, 

 not covered by granitic sands. The causes which have 

 favoured the accumulation of calcareous matter in the eastern 

 region of the coast chain, in the Llanos of Venezuela (from 

 104 to 8 north), cannot have operated nearer the equator, 

 in the group of the mountains of the Parime, and in the 

 plains of the liio Negro and the Amazon (lat. 1 north, to l c 

 south). The latter plains however, furnish some ledges of 

 fragmentary rocks, on the south-west of San Fernando de 

 Atabapo, as well as on the south-east, in the lower part of 

 the Bio Negro and the Rio Branco. I saw in the plains of 

 Jaen de Bracamoros a sandstone which alternates with ledges 

 of sand and conglomerate nodules of porphyry and Lydian 

 stone. MM. Spix and Martins affirm that the banks of 

 the Rio Negro, on the south of the equator, are composed of 

 variegated sandstone ; those of the R/io Branco, Jupura, and 

 Apoporis, of quadersandstein ; and those of the Amazon, on 

 several points, of ferruginous sandstone.* It remains to 

 examine if (as I am inclined to suppose) the limestone and 

 gypsum formations of the eastern part of the littoral Cordil- 

 lera of Venezuela differ entirely from those of the Llanos, and 

 to what series belongs that rocky wallf named the Galcra, 



Braunes eisenschttssiges Sandstein-Conglomerat (Iron-sand of the 

 English geologists, between the Jura limestone and green sandstone.) 

 MM. Sptx and Martius found on rocks of quadersandstein, between the 

 Apoporis and the Japura, the same sculptures which we have pointed out 

 from the Essequibo to the plains of Cassiquiare, and which seem to prove 

 the migrations of a people more advanced in civilization than the Indian! 

 who now inhabit those countries. 



^ Is this wall a succession of rocks of dolomite or a dyke of quader- 

 eandstein, like the Devil's Wall (Teufelsmauer), at the foot of the llarti ? 

 Calcareous shelves (coral banks), either ledges of sandstone (effects of the 

 revulsion of the waves) or volcanic eruptions, are commonly found on the 

 borders of great plains, that i, on the shores of ancient inland seas. The 

 Llanos of Venezuela furnish examples of such eruptions near 



