1 73 Geological Delineation of South America. 



power of transmitting any excess of fluid above a given 

 quantity, suppose that produced bv S.'i four-inch plates. 



Some other theory must therefore, it appears to me, be 

 necessarily resorted to. I am, sir. 



Your obedient servant, 

 March 12, 1S04. B. E. 



XXXI. Sketch of a Geological DeUneatioJi of South Ame- 

 rica. By F. A. Von Humboldt. 



[Concluded from p. 36.] 



Jj-AVixG already given a cursor\' view of the general ap- 

 pearance which the mountains of South America exhibit to 

 the eve of the geologist, I shall now enumerate the different 

 kinds of mountains which I have hitherto discovered in that 

 country, beginning with the oldest. 



I. Primitive Mountains. 



Granite. — The whole cordillera of Parima, and particu- 

 larly the neighbourhood of the volcanoes of Duida and Mar- 

 ciclago, consist of aranite, which docs not form a transition 

 into gneiss. In the cordillera of the coast it is almost every 

 where covered and mixed with gneiss and micaceous schist. 

 I saw it disposed in strata of from two to three feet in thick- 

 ness, exceedingly regular, declining from three to four per 

 league, towards the north-west between Valencia and Porto- 

 cabello. I found it on the Eincon del Diablo south-east 

 from Portocabello, with large and beautiful crystals of feld- 

 spar an inch and a half in diameter, like the large grained 

 granite on the high summits of the Schneegebirg and the 

 Ficluclbero;, those of Scotland and Chamouni. It is here 

 spilt into regular prisms ; and I saw it on Calavera du Cerro 

 de Mariana beyond Cura, and on the Silla de Caracas, 

 in this prismatic form, which the learned mineralogist 

 ]M. Karsten observed on the Schneekoppe in Silesia. The 

 northern part of Cicrmany, and the lands on the Baltic in 

 Europe, but not the plain to the south of the Fichtelberg 

 in Swabia and Bavaria, arc full of monstrous blocks of gra- 

 nite which have rolled down from the heights. In neither 

 of the llanos of South America, that of Orinoco, and that 

 of the Amazon river, did wc find any such masses, and no 

 fragments of primitive mountains. The granite mountains 

 of Los Maricbcs near Caracas, and those of Torrito be- 

 tween 



