2fiS Olservaiions on Volcanoes arid their Lara. 



determmed that lava proceeds from stra:ta similar to tho?c 

 Avith which we are acquainted. The operations of volca- 

 noes, those vast laboratories of nature, will always remain 

 unknown to us, and on this subject our conjectures will al- 

 wavs be very uncertain. 



\V^hat is the nature of that mixture which gives birth to 

 these eruptions, that produce lava and throw up mountains;? 

 What we observe as certain is, that the introduction of the 

 v,:Uer of the sea is necessary to excite these fermentations, 

 £5 containing marine acid and other salts, which, united to 

 t'ic sulphuric aciiJ, the bases of which are contained in 

 abundance in the subterranean strata, determine these fer- 

 mentations, which produce the disengagement of fire and 

 other fluids, and all the grand cftecrs Ihat arc the conse- 

 quence. 



Several naturalists have believed, and still believe, that 

 fresh or rain water is suiEcient for this purpose; but they 

 an; mistaken : this opinion is contradicted by every fact 

 known. To be convinced of this, nothing is necessary but 

 to take a short view of them. I have done it several times, 

 as it is necessary to consider them often. I shall here enu- 

 merate the principal ones : — No burning mountain exists 

 in the interior part of the earth ; and alf those which still 

 burn are, without exception, in the neighbourhood of the 

 sea, or surrounded by its waters. Among the deliquescent 

 salts deposited by the smoke of volcanoes, we distinguish 

 chiefly the niarine salt, united to difi'erent bases. Several of 

 the volcan;:c3 of Iceland, and Heckla itself, sometimes 

 throw up erujitlons of water, which deposit marine salt in 

 abundance. No extent of fresh water, however vast, gives 

 birth to a volcano. These facts are sufficient to prove that the 

 concurrence of sea-water is absolutely necessary to excite 

 those fermentations which proikice volcanoes. 



I shall here repeat the distinction I have already made 

 between burnt out volcanoes and the antient volcanoes, 

 that I may range them in two separate classes. 



When we simply give the name of harnt out or extin- 

 guished volcanoes to volcanic mountains which are in the 

 middle of the continents, it is to represent, them as having 

 burnt while the land was dry, and inhabited as it is at 

 present; which is not a just idea. These volcanoes have 

 burnt when the land on which they are raised was under 

 the waters of the antient sea, and none of them have burnt 

 ■since our continents became dry. It is even very apparent 

 thal^ nio«t of them were extinct before the retreat of the 

 sea, as we find by numerous examples iu the present sea. 



