MICA-SL\TE, ETC. 
3S3 
the limits here assigned to gneiss, as a predominant rock 
(long. 681° 70J®), gneiss passes sometimes to mica-slate, 
Vhile the appearance of a transition to granite is only found 
on the summit of the SiUa of Caracas.* It would require a 
more careful examination than I was able to devote to the 
suhiect to ascertain whether the granite of the peak ot tst. 
Gothard, and of the Silla of Caracas, really lies over mica- 
slate and gneiss, or if it has merely pierced those rocks, 
rising in the form of needles or domes. The gneiss of the 
littoral Cordillera, in the province of Caracas, contains almost 
exclusively garnets, rutile titanite, and graphite, disseminated 
in the whole mass of the rock, shelves of granular limestone, 
and some metalliferous veins. I shall not decide whether 
the grauitiferous serpentine of the table-land of Buenansta 
is inclosed in gneiss, or whether, superposed upon that 
rock it does not rather belong to a formation of weisstein 
(heptinite) similar to that of Peiiig and Mittweyde in 
^'*In”uiat part of the Sierra Parime which M. Bonpland and 
myself visited, gneiss forms a less marked zone, and oscillates 
more frequently towards granite than mica-slate. I found 
no garnets in the gneiss of Panme. There is no doubt that 
the gneiss-granite of the Orinoco is slightly auriferous on 
some points. 
(c) Mica-sIiATE, with clay-slate (thonschiefer), forms a 
continuous stratum in the northern chain of the littoral Cor- 
dillera, from the point of Araya beyond the meridian of 
Cariaco, as well as m the island of 3Iarguerita. It contains, 
in the peninsula of Araya, garnets disseminated m the mass 
cyanite, and, when it passes to clayey-slate, small layers of 
native alum. Mica-slate constituting an independent forma- 
tion, must be distinguished from mica-slate subordinate to a 
stratum of gneiss, on the east of Cape Codera. The niica- 
slate subordinate to gneiss, presents, m thevaUey ot iu>, 
shelves of primitive limestone and small strata of graphic 
ampelite (zmcheschiefer) ; between Cabo Blanco and Catia, 
layers of chloritic, granitiferous slate, and slaty amphibole , 
• The Silla is a mountain of gneiss like Adam s Peak, in the island ol 
Ceylon, and of nearly the same height. 
