244 C0SM03. 



neighboring sea ?"* In order to explain the necessity of the 

 vicinity of the sea, recourse has been had, even in modern 

 times, to the hypothesis of the penetration of sea w^ater into 

 the foci of volcanic agency, that is to say, into deep-seated 

 terrestrial strata. When I collect together all the facts that 

 may be derived from my own observation and the laborious 

 researches of others, it appears to me that every thing in this 

 involved investigation depends upon the questions whether the 

 great quantity of aqueous vapors, which are unquestionably 

 exhaled from volcanoes even when in a state of rest, be de- 

 rived from sea water impregnated with salt, or rather, perhaps, 

 with fresh meteoric water ; or whether the expansive force of 

 the vapors (which, at a depth of nearly 94,000 feet, is equal 

 to 2800 atmospheres) would be able at different depths to 

 counterbalance the hydrostatic pressure of the sea, and thus 

 afford them, under certain conditions, a free access to the 

 focus ;t or whether the formation of metallic chlorids, the 

 presence of chlorid of sodium in the fissures of the crater, and 

 the frequent mixture of hydrochloric acid with the aqueous 

 vapors, 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 sulphureted hydrogen gas seems more characteristic of 

 Bolfataras than of active volcanoes) is not directly at variance 



* [Although extinct volcanoes seem by no means confined to the 

 neighborhood of the present seas, being often scattered over the most 

 inland portions of our existing continents, yet it will appear that, at the 

 time at which they were in an active state, the greater part were in the 

 neighborhood either of the sea, or of the extensive salt or fresh water 

 lakes, which existed at that period over much of what is now dry land. 

 This may be seen either by referring to Dr. Boue's map of Europe, or 

 to that published by Mr. Lyell in the recent edition of his Principles of 

 Geology (1847), from both of which it will become apparent that, at a 

 comparatively recent epoch, those parts of France, of Germany, of 

 Hungary, and of Italy, which afford evidences of volcanic action now 

 extinct, were covered by the ocean. Daubeney On Volcanoes, p. 605.] 

 — Tr. 



t Compare Gay-Lussac, Sur let Volcans, in the Annales de Chiinie, 

 t. xxii., p. 427, and Bischof, Wdrmelehre, s. 272. The eruptions of 

 smoke and steam which have at difierent periods been seen in Lance 

 rote, Iceland, and the Kurile Islands, during the eruption of the neigh 

 boring volcanoes, afford indications of the reaction of volcanic foci 

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

 cur when the expansive force of the vapor exceeds the hydrostatic 

 pressure. 



