k. 



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e 



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ions. 



Uhe 



the 



th! 

 ■ng 



the 



.ngh 

 lava 



ttflv 



nus 



)D11- 



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Cii. XXXIII.] ESCAPE OF IIYDEOGEN DUEING ERUPTIONS. 



225 



cent cinders. 



This explanation is sufficient ; but it may also be observed 

 that the flame of hydrogen would rarely be visible during an 

 eruption ; as that gas, when inflamed in a pure state, burns 

 with a very faint blue flame, which even in the night could 

 hardly be perceptible by the side of red-hot and incandes- 



Its immediate conversion into water when 

 inflamed in the atmosphere, might also account for its not 

 appearing in a separate form. 



The observations of Bunsen in Iceland in 1844, of St. 

 Claire Deville on Vesuvius in 1855 and 1861, and of Fouque 

 on Santorin in 1866, have proved that there is an abundant 

 escape of hydrogen, both in a free state and in combination 

 with other substances, during eruptions ; and the two last- 

 mentioned chemists have succeeded in demonstrating the 

 perfect accordance of the chemical composition of the pro- 

 ducts of volcanic eruptions, both gaseous and solid, with the 

 doctrine that salt water has been largely present in the vol- 

 canic foci. It had been asked why then are there no salts of 

 magnesia in volcanic fumeroles ? They reply that these salts 

 are readily decomposable by hot steam, and that when water 

 and heat are present they produce hydrochloric acid and 

 magnesia. That acid is found in the vapours which 

 disengaged from red-hot lava, and the 

 not volatile is left behind in the lava itself, constituting one 



are 

 magnesia which is 



most 



manner 



^ 



mentioned French chemists have shown that common salt 



of Etna 



can be resolved mto its elements by hot steam aloi 

 G-ay-Lussac had thought impossible. 



M. Fouque affirms that in the recent eruption _ _ 

 (in 1865) which he witnessed, the gaseous emanations agreed 

 in kind with those which we might have looked for if large 

 bodies of sea-water had gained access to reservoirs of sub- 

 terranean lava, and if they had been decomposed and ex- 

 pelled with the lava ; and more than this, he calculated that 



the quantity of aqueous vapour was relatively to othei 



m due proportion— that there was 



rases 



emission from 



^ * ^Fouque, Rapport sur les Ph<^nom^neB Chimiqucs. Eruption of Etna in 1865, 



VOL. II. 



Q, 



