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sheets, streams that appear like real strata. 

 The lithoid masses cover here, if we may use 

 the expression, the shore of the ancient interior 

 sea ; whatever is subject to destruction, the li- 

 quid dejections, the scoriae filled with bubbles, 

 have been carried away. These phenomena 

 become particularly worthy of attention by the 

 intimate relations that are observed between 

 the phonolites and the amygdaloids, which in- 

 dubitably containing pyroxenes and hornblende 

 gruensteins, form strata in a transition slate* 

 In order to have an accurate idea of the whole 

 of the situation and superposition of these rocks, 

 we shall name the formations as they occur in a 

 profile drawn from North to South. 



We find at first in the Sierra de Mariara, 

 which belongs to the northern branch of the 

 Cordillera of the coast, a coarse-grained granite; 

 then, in the valleys of Aragua, on the borders of 

 the lake, and in the islands it contains, as well 

 as in the southern branch of the chain of the 

 coast, gneiss and mica-slate. These last two 

 rocks are auriferous in the Quebrada del Oro, 

 near Guigue ; and between Villa de Cura and 

 the Morros de San Juan, in the mountain of 

 Chacao. The gold is contained in pyrites, which 

 are found sometimes disseminated almost im- 

 perceptibly in the whole mass of the gneiss % 



* The four metals, which are found disseminated in the 



