S70 SIEATA OF THE SIEEEA PAEIME, 
tion, we would distinguish mineralogically between the rocks 
of granite, gneiss, and mica-slate, it must be borne in mind 
that coarse-grained granite, not passing to gneiss, is very rare 
in this country. It belongs peculiarly to the mountains that 
bound the basin of the lake of Valencia towards the north; 
lor in the islands of that lake, in the mountains near the 
Villa de Cura, and in the whole northern chain, between the 
meridian of Vittoria and Cape Codera, gneiss predominates, 
Bonietimos alternating with granite, or passing to mica-slate. 
Mica-slate is the- most frequent rock in the peninsula of 
Araya and the group of Macanao, which forma the western 
part of the island of Marguerita. On the west of Maui- 
quarez, the mica-slate of the peninsula of Araya loses bv 
degrees its semi-metallic lustre it is charged with carboii, 
and becomes a clay-slate (thonschiefer) even an ampelite 
(alaunschiefer). Beds of granular limestone are most com- 
mon in the primitive northern chain; and it is somewhat 
remarkable that they are found in gneiss, and not in mica- 
slate. 
We find at the back of this granitic, or rather micaslate- 
gneiss soil of the southern chain, on the south of the Villa de 
Cura, a transition stratum, composed of greenstone, amphi- 
bolic serpentine, micaceous limestone, and green and carbu- 
retted slate. The most southern limit of this district is 
marked by volcanic rocks. Between Parapara, Ortiz, and 
the Cerro de Plorea (lat. 9° 28'— 9“ 34' ; long. 70° 2' 70° 
15'), phonolites and amygdaloids are fouiifl on the very 
border of the basin of the Llanos, that vast inland sea which 
once filled the whole space between the Cordilleras of 
Venezuela and Parime. According to the observations of 
Major Long and Dr. James, trap-formations (bulleuses 
dolerites and amygdaloids with pyroxene) also border the 
plains or b^in of the Mississippi, towards the west, at the 
decli\'ity of the llocky Mountains. The ancient pyrogenic 
rocks which I found near Parapara where they rise in mounds 
with rounded summits, are the more remarkable as no others 
have hitherto been discovered in the whole eastern part of 
South America. The close connection observed in the strata 
of Parapara, between ^eenstone, amphibolic serpentine, 
and amygdaloids containing crystals of pyroxene; the form 
of the Morros of San Juan, which rise like cylinders above 
