224 COSMOS. 



d Volcanoes , according to the difference of their formation 

 and activity. Action ~by fissures and cauldron-like depres- 

 sions. Circumvallation of the craters of elevation. Vol- 

 canic conical and hell-shaped Mountains, with open or 

 closed summits, Difference of the Rocks through which 

 Volcanoes act. 



(Amplification of the Eepresentation of Nature : 

 Cosmos, vol. i., pp. 225247.) 



Amongst the various specific manifestations of force in 

 the reaction of the interior of our planet upon its uppermost 

 strata, the mightiest is that presented by the true Volcanoes : 

 that is to say, those openings through which, besides 

 gases, solid masses of various materials are forced up from 

 unmeasured depths to the surface, either in a state of igneous 

 fusion, as lava streams, or in the form of cinders, or as pro- 

 ducts of the finest trituration (ashes). If we regard the 

 words volcano and fiery mountain as synonymous, in accord- 

 ance with the old usage of speech, we thus, according to a 

 preconceived and very generally diffused opinion, attach to 

 the idea of volcanic phenomena, the picture of an isolated 

 conical mountain, with a circular or oval orifice at the 

 summit. Such views, however, lose their universality when 

 the observer has the opportunity of wandering through 

 connected volcanic districts, occupying a surface of many 

 thousand square geographical miles ; for example, the entire 

 central part of the highlands of Mexico, between the Peak 

 of Orizaba, Jorullo, and the shores of the South Sea; or 

 Central America ; or the Cordilleras of New Granada and 

 Quito, between the Volcano of Purace", near Popayan, that 

 of Pasto and Chimborazo ; or the isthmian chain of the 

 Caucasus, between the Kasbegk, Elburuz and Ararat. In 

 lower Italy, between the Phlegraean Fields of the mainland 

 of Campania, Sicily, and the islands of Lipari and Ponza, as 

 also in the Greek Islands, part of the intervening land has 

 not been elevated with the volcanoes, and part of it has 

 been swallowed by the sea. 



In the above-mentioned great districts of America and 

 the Caucasus, masses of eruptions (true Trachytes, and not 



