VOLCANIC TOBMATIONS. 
457 
the country round Caracas we found gneiss, and mica-slate 
containing beds of primitive limestone. The strata are 
scarcely more fractured or irregularly inclined than near 
I- reyburg in Saxony, or wherever mountains of primitive 
formation rise abruptly to great heights. I found at Caracas 
neither basalt nor dorolite, nor even trachytes or trap-por- 
phyries ; nor in general any trace of an extinguished vol- 
cano, unless we choose to regard the diabases of primitive 
griinstem, contained in gneiss, as masses of lava, which have 
hlled up fissures. These diabases are the same as those of 
Bohemia, Saxony, and Franconia;* and whatever opinion 
may be entertained respecting the ancient causes of the 
oxidation of the globo at its surface, all those primitive 
mountains, which contain a mixture of hornblende and feld- 
spar, either in veins or in balls with concentric lavers, will 
not, I presume, be called volcanic formations. Mont Blanc 
and Mont d’Or will not be ranged in one and the same 
class. Even the partisans of the Huttonian or volcanic 
theory make a distinction between the lavas melted under 
the mere pressure of the atmosphere at the surface of the 
globe, and those layers formed by fire beneath the immense 
weight of the ocean and superincumbent rocks. They would 
not confound Auvergne and the granitic valley of Caracas 
in the same denomination; that of a country of extinct 
volcanos. 
I never could have pronounced the opinion, that the Silla 
and the Ceno dc Avila, mountains ol gneiss and mica-slate 
were in dangerous proximity to the city of Caracas because 
they contained a great quantity of pyrites in subordinate 
beds ol primitive limestone. But I remember bavin" said, 
during my stay at Caracas, that the eastern extremity of 
lerra Firma appeared, since the great earthquake of Quito, 
m a state of agitation, which warranted apprehension that 
the province of Venezuela would gradually be exposed to 
violent commotions. I added, that when a country had 
been long subject to frequent shocks, new subterranean 
communications seemed to open with neighbouring coun- 
tries; and that the volcanos of the West India Islands, 
These griinsteins are found in Bohemia, near Pilsen, in granite ; in 
-axony, in the mica-slates of Scheenberg; in Franconia, between Steebeu 
»llfl hauenstein, in transition-slates. 
