ee eee 
Natural History of Volcanos and Earthquakes. 263 
the great eruption of this voleano in 1822, at the beginning of 
January, the springs at Resina, St. Jorio, and particularly in the 
Places in the immediate vicinity of Vesuvius, diminished percep- 
tibly.* Monticelli observed similar phenomena before the erup- 
tion in 1813, and he thinks that, in general, they are a sure sign 
of one. It is hardly to be doubted that rents were opened by 
the earthquakes, through which the water descended to greater 
depths, accumulating, perhaps, in great caverns, and from thence 
found its way to the source of the volcanic action. 
We find considerable accumulations of water in all mountains 
taversed by numerous fissures. We will only now mention the 
Western declivity of the T'eutoburger Wald, in which such con- 
siderable rivers have their source ; the Jura mountains; and the 
emmi.t The volcanic inundations, of which Von Humboldt 
gives such extraordinary examples,{ are an additional evidence of 
the existence of such great subterranean accumulations of water, 
mM the Vicinity of volcanos. Lastly, we have, further, examples 
of volcanos coming into action after violent storms of rain; for 
Instance, the Mer-Api, in Java.§ In the Andes of Quito, the 
idians imagine they have observed, that the quanity of percola- 
ting snow-water increases the activity of volcanos.|| Can it, then, 
any longer be doubted, that the proximity of the ocean is by no 
SE pense Se a a 
of the Canary Islands, notwithstanding the height of the mountains, and the mass 
of clouds which travellers always see collected over this Archipelago. Reise, 
Ep. 173, 
Von Humboldt (Reise, t. iii, p. 229) mentions several rivers which lose them- 
selves in the gneiss rocks. When these gneiss mountains were upraised, consid- 
frable caverns may have been formed, which were afterwards filled with water. 
 Annal. de Chim. et de Phys. t. xxvii, p. 128. This cireumstance, however, 
Must be considered, that the strong heat over the active volcano dilates the atmos- 
— fr 
*S Inondat. Voleaniques. Journ. de Physique, t. tank 103. 
§ Memoir of the Conquest of Java. London, 1815, p. 40 
| Von Humboldt’s Reise, t. i, p. 263. 
