Volcanos and Earthquakes. 57 



If the melted nucleus of the earth be the common seat of the 

 volcanic activity of the whole earth, subterranean communica- 

 tions subsist between all volcanos. The existence of such com- 

 munications cannot be doubted. Immediately after the earth- 

 quake which overthrew Caraca^^ there followed the great erup- 

 tion of the volcano of ^S*^ Vincent^ and the earth no longer trem- 

 bled at Venezuela. When the dense, black column of smoke, 

 which, in the year of 1797, had issued for several months from 

 the volcano near that city, disappeared, the cities of Riobamba^ 

 Hambato, and Tacunga^ 280 English miles distant, were at 

 the same hour destroyed by a violent shock.* Other instances 

 of this kind will be mentioned afterwards. 



Andrea Lorenzo Curbeto's description of the great vol- 

 canic eruption in the island of Lancerote, for which we are in- 

 debted to Von Buch,-f- also shews how for six years, from 1730 

 to 1736, the gaseous fluids in the interior found new vents in 

 all directions, sometimes here and sometimes there, and yet 

 were not capable of preserving a single one permanently open. 

 Sometimes two or three openings were formed at once with a tre- 

 mendous crash accompanied with flames, (?) which alarmed the 

 whole island. At one time three apertures united suddenly 

 into one very high cone ; lava flowed out below and reached the 

 sea. If, says that acute geologist, the unhappy Laiiccrote had, 

 like Teneriffe, possessed a volcano, perhaps not one of those 

 numerous cones would have been thrown up, and probably not 

 a single village would have been destroyed.^ He thinks it 

 highly probable that this eruption took place entirely from one 

 great rent. 



'^ Von Humboldt Reise, t. 1. p. 498. t Loco cit. 



X Von Buch supposes that only the gaseous matters, but not solid sub- 

 stances, viz. lavas, slags, rapilli, and ashes, proceed from the focus of the 

 volcanic plienomena. He observes that these masses always shew them- 

 xelves to be of a nature corresponding to the roclvs out of which they are 

 ejected. 



We must not forget that Von Buch avjis at that time still attached to 

 Davy's hypothesis, which ascribes volcanic phenomena to the combustion 

 «)f the metals of the alkalies and earths, and which does not require us to 

 ssupposc the origin of volcanic action to lie at any great depth. It is in- 



