242 COSMOS. 



shores of Sciacca and the purely volcanic island of Pat*. 

 tellaria.* 



The geographical distribution of the volcanoes which have 

 been in a state of activity during historical times, the great 

 number of insular and littoral volcanic mountains, and the 

 occasional, although ephemeral, eruptions in the bottom of 

 the sea, early led to the belief that volcanic activity was con- 

 nected with the neighbourhood of the sea, and was dependent 

 upon it for its continuance. " For many hundred years," 

 says Justinian, or rather Trogus Pompeius, whom he follows,f 



* Prgvost, in the Bulletin de la Societt Geologique, t. iii. p. 34 ; 

 Friedrich Hoffman, Hinterlassene Werke, bd. ii. s. 451-456. 



t "Accedunt vicini et perpetui JStnae mentis ignes et insularum 

 JEolidum, veluti ipsis undis alatur incendium ; neque enim aliter durare 

 tot seculis tantus ignis potuisset, nisi humoris nuirimentis aleretur." 

 (Justin, Hist. Philipp., iv. i.) The volcanic theory with which the 

 physical description of Sicily here begins, is extremely intricate. Deep 

 strata of gulphur and resin ; a very thin soil full of cavities and easily 

 fissured ; violent motion of the waves of the sea, which, as they strike 

 together, draw down the air (the wind,) for the maintenance of the fire ; 

 such are the elements of the theory of Trogus. Since he seems from 

 Pliny (xi. 52) to have been a physiognomist, we may presume that 

 his numerous lost works were not confined to history alone. The 

 opinion that air is forced into the interior of the earth, there to act on 

 the volcanic furnaces, was connected by the ancients with the supposed 

 influence of winds from different quarters on the intensity of the fires 

 burning in ^Etna, Hiera, and Stromboli (see the remarkable passage 

 in Strabo, lib. vi. p. 275 and 276.) The mountain island of Stromboli 

 (Strongyle,) was regarded therefore as the dwelling-place of JLolus, 

 "the regulator of the winds," in consequence of the sailors foretelling 

 the weather, from the activity of the volcanic eruptions of this island. 

 The connexion between the eruption of a small volcano with the state of 

 the barometer and the direction of the wind is still generally recognised, 

 (Leop. von Buch, Descr. pliys. des lies Canaries, p. 334 ; Hoffmann, in 

 Poggend. Annalen, bd. xxvi. s. viii.) although our present knowledge of 

 volcanic phenomena, and the slight changes of atmospheric pressure 

 accompanying our winds, do not enable us to offer any satisfactory 

 explanation of the fact. Bembo, who during his youth was brought up 

 in Sicily by Greek refugees, gave an agreeable narrative of his 

 wanderings, and in his JEtna Dialogue (written in the middle of the 

 sixteenth century,) advances the theory of the penetration of sea- water to 

 the very centre of the volcanic action, and of the necessity of the 

 proximity of the sea to active volcanoes. In ascending ^Etna the 

 following question was proposed. " Explana potius nobis quas petimus, 

 ea incendia unde oriantur et orta quomodo perdurent In omni tell are 

 uuspiam majores fistulas aut meatua ampliorea aunt Quam in locis, quro 



