OF VOLCANOS. 219 



to " Salses" or mud volcanos, argillaceous cones emitting 

 mud, asphalte, and hydrogen, as at Girgenti in Sicily, and 

 at Turbaco in South America ; to the Geysers, hot springs 

 in which, as in those of Iceland, the waters, pressed by 

 elastic vapours, rise in jets to a considerable altitude ; and, 

 in general, to all operations of natural forces having their 

 seat in the interior of our planet. In Central America 

 (Guatimala), and in the Philippine Islands, the natives even 

 distinguish formally between water- and fire-volcanos, Yol- 

 canes de agua y de fuego, giving the former name to those 

 mountains from which subterranean waters issue from time 

 to time with violent earthquake shocks and a hollow noise. 



Not denying the connexion of the different phenomena 

 which have been referred to, it yet appears desirable to give 

 greater precision to the terms empfcyed in the physical as 

 well as in the mineralogical part of geology, and not to 

 apply the word " volcano" at one moment to a mountain 

 terminating in a permanent igneous opening or fiery crater, 

 and at another to every subterranean cause of volcanic 

 phenomena. In the present state of our planet the most 

 ordinary form of volcanos is indeed in all parts of the globe 

 that of an isolated conical mountain, such as Vesuvius, 

 Etna, the Peak of Teneriffe, Tunguragua, and Cotapaxi. I 

 have myself seen such volcanos varying in size from the 

 smallest hill to an elevation of 18000 (19184 English) feet 

 above the sea. But besides these isolated cones there are 

 also permanent openings 'or craters, having established 

 channels of communication with the interior of the earth, 

 which are situated on long chains of mountains with serrated 



