STRATIFICATION OF ROCKS. 
391 
azure copper-ore* disseminated in veins of quartz, and small 
strata of plumbago (black lead), or earthy carburttted iron. 
This last is found in pretty large masses, and sometimes 
mingled with sparry iron-ore, in the ravine of Tocurne, to 
the west of the Silla. 
Between the spring of Sanchorquiz and the Cross of La 
Guayra, as well as still higher up, the gneiss contains consi- 
derable beds of saceharoidal bluish-grey primitive limestone, 
coarse-grained, containing mica, and traversed by veins of 
white calcareous spar. The mica, with large folia, lies in the 
direction of the dip of the strata. 1 found in the primitive 
limestone a great many crystallized pyrites, and rhomboidal 
fragments of sparry iron-ore of Isabella yellow. I endea- 
voured, but without success, to find tremolite,t which in the 
Fitchelberg, in Franconia, is common in the primitive lime- 
stone without dolomite. In Europe beds of primitive lime- 
stone are generally observed in the mica-slates ; but we find 
also saceharoidal limestono in gneiss of the most ancient for- 
mation, in Sweden near Upsala, in Saxony near Burkersdorf, 
and in the Alps in the road over the Simplon. These situa- 
tions are analogous to that of Caracas. The phenomena of 
geognosy, particularly those which are connected with the 
stratification of rocks, and their grouping, are never solitary, 
but are found the same in both hemispheres. I was the 
more struck with these relations, and this identity of forma- 
tions, as, at the time of my journey in these countries, mine- 
ralogists were unacquainted with the name of a single rock 
of Venezuela, JS'ew Grenada, and the Cordilleras of Quito. 
* Blue carbonate of copper. 
f Grammatite of Haiiy. The primitive limestone above the spring of 
Sanchorquiz, is directed, as the gneiss in that place, hor. 5 - 2, and dips 
45° north ; but the general direction of the gneiss is, in the Cerro de 
Avila, hor. 3 - 4 with G0° of dip N.W. Exceptions merely local are 
observed in a small space of ground near the Cross of La Guayra (hor. 
6 - 2, dip 8° N.); and higher up, opposite the Quebrada of Tipe (hor. 12, 
dip 50° W.). 
