VOLCANOES. 225 



trachytic conglomerates ; streams of obsidian ; quarried 

 blocks of pumice -stone, and not pumice boulders trans- 

 ported and deposited by water) make their appearance, 

 seeming to be quite independent of the mountains, which 

 only rise at a considerable distance. Why should not the 

 surface have been split in many directions during the pro- 

 gressive refrigeration of the upper strata of the earth by 

 radiation of heat, before the elevation of isolated mountains 

 or mountain chains had yet taken place ? Why should not 

 these fissures have emitted masses in a state of igneous 

 fusion, which have hardened into rocks and eruptive stones 

 (trachyte, dolerite, melaphyre, margarite, obsidian, and pu- 

 mice) ? A portion of these trachytic or doleritic strata which 

 have broken out in a viscid fluid state, as if from earth- 

 springs, 81 and which were originally deposited in a horizontal 

 position, have, during the subsequent elevation of volcanic 

 cones and bell-shaped mountains, been tilted into a position 

 which by no means belongs to the more recent lavas, pro- 

 duced from igneous mountains. Thus, to advert in the first 

 place to a very well-known European example, in the Val 

 del Bove on Etna (a depression which cuts deeply into the 

 interior of the mountain) the declination of the strata of 

 lava, which alternate very regularly with masses of boulders, is 

 25 to 30, whilst, according to Elie de Beaumont's exact 

 determinations, the lava streams which cover the surface of 

 Etna, and which have only flowed from it since its elevation 

 in the form of a mountain, only exhibit a declination of 3 

 to 5 on an average of 30 streams. These conditions indi- 

 cate the existence of very ancient volcanic formations, 

 which have broken out from fissures, before the production 

 of the volcano as an igneous mountain. A remarkable pheno- 

 menon of this kind is also presented to us by antiquity ; a 

 phenomenon which manifested itself on Eubcea, the modern 

 Negropout, in an extended plain, situated at a distance 

 from all active and extinct volcanoes. " The violent earth- 

 quakes, which partially shook the island, did not cease until 

 an abyss, which had opened on the plain of Lelantus, threw 

 up a stream of glowing mud (lava)."* 8 



81 Cosmos, vol. i, p. 229. 



82 Strabo i, p. 58, ed. Casaub. The epithet diairvpog, proves that in 

 this case mud-volcanoea are not spoken of. Where Plato, in his geog- 



VOL. V Q. 



