1 76 Geotogtcat Delineation oj South ylmerka^ 



the heiglit of 300 to 63 toises above the level of the sca. 

 Every thing reminds one here of the mountains of Bihii 

 in Bohemia, or of Vienza in Italy. The primitive ser- 

 pcntin on the bank? of thcTucutunemo, which like that of 

 Silesia contains copper veins, becomes gradually mixed 

 with feldspar and hornblend, and makes the transition into 

 trapp or grunstein. Thistrapp is found in stratified masses 

 declining 70" towards the north, or in balls with concen- 

 tric strata, which, interspersed in calcareous clay, form 

 pyramidal hills ; sometimes the transition argillaceous 

 schist of W'crner is interspersed in green and very heavy 

 argillaceous schist, which consists of hornblend and argil- 

 laceous schist intimately mixed together. The same argil- 

 LicCous schist makes a transition near the Ouebrada de 

 Piedras Azules into the primitive argillaceous schist above 

 which it lies. The trapp or grunstein contains also foliace- 

 ous olivin, cry^stallizcd m pyramids of four faces, a fossil 

 which M. Friesleben discovered on our tour into Bohemia, 

 and described in the Mincralogical Journal of Freyberg, 

 augite with a shelly fracture, Icucite in dodecacdra, the 

 sides of the holes and cavities of Avhich are covered with 

 green earth like that of Verona, and a substance which 

 has the splendour of mother-of-pearl, and which I consi- 

 der as zeolite. All these interspersed fossils increase to- 

 wards Parapara, and the trapp there forms real amygdalite. 

 Above this amygdalite, near the hill Florez, at the entrance 

 into the large valley of Orinoco, lies that remarkable stone 

 which is scarce in Europe, and which Werner describes 

 inider the name of porphyry schist. The hornschist of 

 Charpentier, a kind of rock v.hich accompanies basaltes, 

 forms groups of irregular columns, and by the impression 

 of the ferns which it contains in the middle of the moun- 

 tains, as diseoven;d by M. Keuss, proves that it is not of 

 volcanic origin. The porphyry schist of Parapara is a green 

 mass of sonorous stohe, which is very hard, acute angled, 

 and has transparent fragments on the edges : it strikes fire 

 with steel, and contains vitreous feldspar. I did not ex- 

 pect to find this stone again in South America ; it however 

 does not form here such groups of grotesque appearance as 

 in Bohemia, and on mount Eugoneide in the \ enetlan ter- 

 ritories, where 1 have seen it. 



III. Alluvial Mountains. 



These secondary formations, which are of later origin 



than the organic bodies of the earth, follow each other in 



the order of their relative age, as in the plains of Europe, 



2 and 



