290 



the hornblendes better distinguished from the 

 pyroxenes and the gruensteines from the do- 

 lerites ; a great number of phenomena, which 

 now appear solitary and obscure, will be ranged, 

 as it were of themselves, under general laws. 

 The phonolites and other rocks of igneous origin 

 at Parapara are so much the more interesting, 

 as they indicate, ancient eruptions in a granitic 

 zone; as they belong to the shore of the basin 

 of the steppes, as the basaltes of Harusch belong- 

 to the shore of the desert of Sahara -f - ; and 

 lastly as they are the only rocks of the kind we 

 observed in the mountains of the Capitania 

 General of Caraccas, which are also destitute of 

 trachytes, or trap porphyry, basaltes, arid vol- 

 canic productions £ 



The southern declivity of the chain of the 

 West is pretty steep ; the steppes, according to 

 my barometrical measurements, being a thou- 

 sand feet lower than the bottom of the basin of 

 Aragua. From the extensive table-land of the 



* The gruensteins or diabases of the Fichtelgebirge in 

 Franconia, which belong to the transition slate, sometimes 

 contain pyroxenes. See Galdfuss und Bischqf tieher das 

 Fichtelgebirge, vol. i t p. 172 — 174. 



t Hornemann, Voyage en Afrique, vol. i, p. 81, and the 

 excellent Geography of Mr. Ritter, vol. i, p. 372. 



% From the Rio Negro to the coasts of Cumana and 

 Caraccas, to the East of the mountains of Merida, which we 

 did not visit. 



