GEOLOGY. 631 



However, the fact that volcanoes are almost always situ- 

 ated in the neighborhood of the sea leads us to suppose 

 that it must play a certain part in their phenomena ; and 

 such, indeed, is the opinion of several philosophers of the 

 first rank. According to M. Sainte Clair Deville, the so- 

 called smoke that issues from volcanoes is composed even to 

 the extent of 9 9 9- thousandths of the vapor of water, and it 

 is to the condensation of this in the upper regions of the 

 atmosphere that the deluges of rain that sometimes accom- 

 pany great eruptions are due. Thus the ancient legend 

 would appear to be realized that represents Mount Etna 

 vomiting in vapor the waves that are sucked down into the 

 whirlpool of Charybdis. 



Earthquakes are essentially united to volcanic phenom- 

 ena, and often accompany them. They apparently result 

 from the effort which the igneous materials of the globe 

 make to launch themselves from their furnace. In coun- 

 tries where there are volcanoes they are looked upon as 

 being in some measure safety-valves ; so long as they are 

 in full activity, and 4he centre, when over-filled, empties 

 itself by the fire-spouting mouth, the country is tranquil. 



No phenomenon offers such a dreadful spectacle as the 

 earthquake. The naturalist who explores a dangerous vol- 

 cano arrives at it armed with patience and courage. He 

 knows the monster he proposes to face; its fury is an- 

 nounced by warning signs ; whilst the earthquake, in the 

 twinkling of an eye, entirely annihilates a large town. 



The celebrated earthquake of Lisbon took place the 1st of 

 November, 1755. Nothing had occurred to make men sus- 

 pect such an occurrence, when, at five-and-twenty minutes 



