TRUE VOLCANOES. 



le Cone du Cantal, les Monts-Dore) ; Vivarais, in which the an- 

 cient lavas have broken out from gneiss (Coupe (TyAsac, and 

 the cone of Montpezat) ; Velay : eruptions of scoriae from 

 which no lava issue ; the Euganean hills ; the Alban mount- 

 ains, Rocca Monfina and Vultur, near Teano and Melfi ; the 

 extinct volcanoes about Olot and Castell Follit, in Catalo- 

 nia ;* the island group, Las Columbretes, near the coast of 

 Valencia (the sickle-shaped larger island Columbraria of the 

 Romans, upon which Montcolibre, latitude 39 54' accord- 

 ing to Captain Smyth, is full of obsidian and cellular tra- 

 chyte); the Greek island Nisyros, one of the Carpathian 

 Sporades, of a perfectly round form, in the middle of which, 

 at an elevation of 2270 feet according to Ross, there is a 

 deep, walled cauldron, with a strongly detonating solfatara, 

 from which at one time radiating lava streams poured them- 

 selves into the sea, where they now form small promontories, 

 and furnished volcanic millstones in Strabo's time (Ross, Rei- 

 sen aufden griechischen Inselii, bd. ii., s. 69, and 72-78). For 

 the British islands we have here still to mention, on account 

 of the antiquity of the formations, the remarkable effects of 

 submarine volcanoes upon the strata of the lower silurian 

 formation (Llancleilo strata), cellular volcanic fragments be- 

 ing baked into these strata, while, according to Sir Roderick 

 Murchison's important observation, even the eruptive trap- 

 masses penetrate into lower silurian strata in the Corndon 

 mountains (Shropshire and Montgomeryshire) ;t the dike-phe- 

 nomena of the isle of Arran ; and the other points in which 

 the interference of volcanic activity is visible, although no 

 traces of true platforms are to be discovered. 



II. ISLANDS OF THE ATLANTIC OCEAN. 



The volcano Esk, upon the island of Jan Mayen, ascended 

 by the meritorious Scoresby, and named after his ship ; height 

 scarcely 1600 feet. An open, not ignited summit-crater ; ba- 

 salt, rich in pyroxene and trass. 



Southwest of the Esk, near the North Cape of Egg Island, 



* With regard to Vivarais and Velay, see the very recent and ac- 

 curate researches of Girai'd, in his Geologischen Wanderungen, bd. i. 

 (1856), s. 161, 173, and 214. The ancient volcanoes of Olot were dis- 

 covered by the American geologist Maclure in 1808, visited by Lyell 

 in 1830, and well described and figured by the latter in his Manual of 

 Geology, 1855, p. 535-542. 



f Sir Roderick Murchison, Siluria, p. 20, and 55-58 (Lyell, Manual, 

 p. 563). 



