Natural History of Volcanos and Earthquakes. 271 



flames, was only the ferilli in the smoke.* Lightning, caused by 

 the electricity excited by the rapid evaporation, was observed 

 there, as it is during the eruptions of Vesuvius and other igneous 

 mountains. At the end of December, 1830, this island, which 

 was 2100 feet in circumference, and the highest point of which 

 rose 210 feet above the sea, shared the fate of Sabrina, and dis- 

 appeared. From the bottom of the sea it had risen between 700 

 and 900 feet ; and from what depth below, may be conjectured 

 from the calculations previously given. 



Thus, then, the rising of islands. out of the sea, is a well au- 

 thenticated fact, and if we should for a moment be left in doubt 

 concerning the cause of this phenomenon, by the appearance of 

 steam in the presence of the sea-water, yet the evolution of 

 aqueous vapor from volcanic islands, enclosed on all sides by 

 solid rock, seems to dispel such doubts. 



Examples of elevations on land in historical times are much 

 more rare. Of these we are only acquainted with the elevation 

 of Monte Nuovo, near Piizzuoli, in 1528, which rose 400 feet in 

 about three days ; that of Monte Rosso, near Catania, in Sicily, 

 in 1669, which rose to a height of 820 feet in about four weeks, 

 and that of Jorullo, which rose to a height of 1480 feet above 

 the plain, in on« day, on the 29th September, 1759.f 



These are also formed, like the volcanic islands, in two differ- 

 ent ways. The Monte Nuovo was formed by the accumulation 

 of the loose masses ejected from the volcano, whilst mountains 

 of basalt, trachyte, phonolite, &c. which are so abundantly scat- 

 tered over the surface of the earth, have been formed by the up- 

 raising of solid rocks-l 



Vesuvius, or rather its cone, seems also to present an example 

 of an elevation in the historic area. Its formation perhaps does 

 not go farther back than the period of the famous eruption of 79 

 after the Christian era, in which Herculaneum and Pompeii were 

 destroyed ; for ancient writers never speak of the mountain as 



* Without exactly wishing to generalize, this circumstance is yet sufficient to 

 render us distrustful in judging of descriptions of similar phenomena in which 

 flames are so often mentioned. 



t Von Humboldt, Nouv. Espagne. v. ii. p. 290. See Burkart loco cit. vol. i, p. 

 226. 



X The late investigations of Buch, Dufrenoy, and Elie Beaumont, show that the 

 Monte JVuovo is a crater of elevation, therefore not entirely or chiefly composed 

 of loose masses of ejected rocks. — Ed. JYew. Phil. Journ. 



