260 Natural History of Volcanos and Earthquakes. 



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

 mutiications cannot be doubted. Immediately after the earth- 

 quake which overthrew Caraccas, there followed the great 

 eruption of the volcano of St. Vi?icent, and the earth no longer 

 trembled 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 Tacimga, 280 English miles dis- 

 tant, 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 volcanic 

 eruption in the island of Lancerote, for which we are indebted 

 to Yon Buch,t also shows how, for six years, from 1730 to 1736, 

 the gaseous fluids in the interior found new vents in all direc- 

 tions, sometimes here and sometimes there, and yet were not ca- 

 pable of preserving a single one permanently open. Sometimes 

 two or three openings were formed at once, with a tremendous 

 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 Lancerote had, like Tene- 

 riffe, 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. J He thinks it highly prob- 

 able that this eruption took place entirely from one great rent. 



* Von Humboldt Reise, t. 1. p. 498. t Loco cit. 



X Von Biich supposes that only the gaseous matters, but not solid substances, 

 viz. lavas, slags, iapilli,^ and ashes, proceed from the focus of the volcanic phe- 

 nomena. He observes that these masses always show^ themselves to be of a na- 

 ture corresponding to the rocks out of which they are ejected. 



We must not forget that Von Buch was at that time still attached to Davy's hy- 

 pothesis, which ascribes volcanic phenomena to the combustion of the metals of 

 the alkalies and earths, and which does not require us to suppose the origin of 

 volcanic action to lie at any great depth. It is indeed, very different, according 

 to the hypothesis which we are endeavoring to defend. In this, the seat of the 

 volcanic actions is supposed to be identical with the place where the elastic forces 

 producing them act. The connection between the lavas, and the slags, lapilli, 

 and ashes resulting from them, and the rocks at the surface, would only then 

 show that the same material which composed the rocks, raised at a former period, 

 and now spread over the surface, has also served for the production of the more 

 recent volcanic formations. But it still remains to be taken into consideration, 

 that aqueous vapor, generated in the lowest point of the volcanic focus, possessing 

 its maximum of elasticity, and heated to the melting point of lava, or above it, is 

 capable, as we have already said, without the assistance of any other power, of 

 converting fusible rocks into a state of hydro-igneous fusion. 



