214 COSMOS. 



the other; but no observation has hitherto justified us in 

 supposing that they are the forerunners of the formation of 

 true volcanoes vomiting lava and cinders. Their activity 

 is of another kind, perhaps originating at a smaller depth, 

 and caused by different^hemical processes. 



d. Volcanoes, according to the difference of their formation and 

 activity. Action by fissures and caldron-like depressions. 

 Circumvallation of the craters of elevation. Volcanic conical 

 and bell-shaped Mountains, *with open or closed summits. 

 Difference of the Rocks through which Volcanoes act. 



(Amplification of the Representation of Nature, Cosmos, vol. L, p. 

 228-248.) 



Among 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 un- 

 measured depths to the surface, either in a state of igne- 

 ous fusion, as lava streams, or in the form of cinders, or as 

 products 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 sum- 

 mit. Such views, however, lose their universality when the 

 observer has the opportunity of wandering through connect- 

 ed 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 Ori- 

 zaba, 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, be- 

 tween the Kasbegk, Elburuz, and Ararat. In Lower Italy, 

 between the Phlegraean Fields of the main land of Campa- 

 nia, 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 swallow- 

 ed by the sea. 



In the above-mentioned great districts of America and 

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



