456 
SISKINS OP MOUNTAINS. 
having suffered as much, as the town, they could tind no 
shelter till they were beyond the mountains of los Teques, 
in the valleys of Aragua, and in the llanos or savannahs. 
No less than fifteen oscillations were felt in one day. On 
the 5th of April there was almost as violent an earthquake 
as that which overthrew the capital. During several hours 
the ground was in a state of perpetual undulation. Large 
heaps of earth fell in the mountains ; and enormous masses 
rf rock were detached from the Silla of Caracas. It was 
even asserted, and this opinion prevails still in the country, 
that the two domes of the Silla sunk fifty or sixty toises ; 
hut this statement is not founded on any measurement. I 
am informed that, in like mamier, in the province of Quito, 
the people, at every period of great commotions, imagine 
that the volcano of Tunguragua diminishes in height. It has 
been affirmed, in many published accounts of the destruction 
of Caracas, that the mountain of the Silla is an extinguish- 
ed volcano ; that a great quantity of volcanic substances 
are found on the road from La Guayra to Caracas ; that the 
rocks do not present any regular stratification; and that 
everything bears the stamp of the action of fire. It has 
even been stated that twelve years prior to the great catas- 
trophe, M. Bonpland and myself had, from our own obser- 
vations, considered the Silla as a very dangerous neighbour 
to the city of Caracas, because the mountain contained a 
great quantity of sulphur, and the commotions must come 
from the north-east. It is seldom that observers of nature 
have to justify themselves for an accomplished prediction; 
but I think it my duty to oppose ideas which arc too easily 
adopted on the local causes of earthquakes. 
In all places where the soil has been incessantly agitated 
for whole months, as at Jamaica in 1693, Lisbon in 1755, 
Cumana in 1766, and Piedmont in 1808, a volcano is ex- 
pected to open. People forget that we must seek the focus 
or centre of action, far from the surface of the earth ; that, 
acc ording to undeniable evidence, the undulations are pro- 
pagated almost at the same instant across seas of immense 
depth, at the distance of a thousand leagues ; and that the 
greatest commotions take place not at the foot of active 
volcanos, but in chains of mountains composed of the most 
heterogeneous rocks. In our geognostieal observation of 
