244 COSMOS. 



tion of metallic chlorides, the presence of chloride of sodium 

 in the fissures of the crater, and the frequent mixture of 

 hydrochloric acid with the aqueous vapours, necessarily 

 imply access of sea- water ; or finally, whether the repose of 

 volcanoes (either when temporary or permanent and complete) 

 depends upon the closure of the channels by which the sea or 

 meteoric water was conveyed, or whether the absence of flames 

 and of exhalations of hydrogen (and sulphuretted hydrogen 

 gas seems more characteristic of solfataras than of active vol- 

 canoes) is not directly at variance with the hypothesis of the 

 decomposition of great masses of water?* 



The discussion of these important physical questions docs 

 not come within the scope of a work of this nature ; but 

 whilst we are considering these phenomena, we would enter 

 somewhat more into the question of the geographical distri- 

 bution of still active volcanoes. We find, for instance, that 

 in the new world three, viz., Jorullo, Popocatepetl, and the 

 volcano of De la Fragua, are situated at the respective dis- 

 tances of 80, 132, and 196 miles from the sea-coast; whilst 

 in Central Asia, as Abel Remusatf first made known to 

 geognosists, the Tbianschan (celestial mountains), in which 

 are situated the lava-emitting mountain of Pe-schan, the 

 solfatara of Urumtsi, and the still active igneous moun- 

 tain (Ho-tseheu) of Turfan, lie at an almost equal distance 

 (1480 to 1528 miles) from the shores of the Polar Sea and 

 those of the Indian Ocean. Pe-schan is also fully 1360 

 miles distant from the Caspian Sca.;J! and 172 and 218 

 miles from the seas of Issikul and Balkasch. It is a fact 

 worthy of notice, that amongst the four great parallel moun- 

 tain chains which traverse the Asiatic continent from east 

 to west, the Altai, the Thianschan, the Kuen-Lun, and the 



through tense columns of water ; that is to say, these phenomena 

 occur when the expansive force of the vapour exceeds the hydrostatic 

 pressure. 



* [See Daubcney, On Volcanoes, pt. iii., ch. xxxvi. xxxviii. xxxix.l 

 Tr. 



f Abel Rcmusat, Lcttre a At. Cordier, in the Annales de Chimte, 

 t. v. p. 137. 



J Humboldt, Asie centrale, i. ii. p. 30-33, 38-52, 70-80, and 426- 

 428. The existence of active volcanoes in Kordofan, 540 miles from 

 the Red Sea, has been recently contradicted by Elippell, Reiften in 

 Nubien, 1829, s. 151. 



