92 Sir H. Davy on the Phenomena of Volcanoes, 



violent explosion. I need not say that when I was standing 

 on the edge of the crater witnessing this phenomenon, the 

 wind was blowing strongly from me : without this circumstance 

 it would have been dangerous to have stood on the edge of 

 the crater ; and whenever from the loudness of the thunder 

 the eruption promised to be violent, I always ran as far as pos- 

 sible from the seat of danger. 



As soon as the eruption had taken place, the ashes and 

 stones which rolled down the crater seemed to fill up the aper- 

 ture, so that it appeared as if the ignited and elastic matter 

 were discharged laterally ; and the interior of the crater as- 

 sumed the same appearance as before. 



I shall now offer some observations on the theory of these 

 phenomena. It appears almost demonstrable that none of 

 the chemical causes anciently assigned for volcanic fires can 

 be true. Amongst these, the combustion of mineral coal is 

 one of the most current ; but it seems wholly inadequate to 

 account for the phenomena. However large a stratum of 

 pit-coal, its combustion under the surface could never produce 

 violent and extensive heat; for the production of carbonic 

 acid gas, when there was no free circulation of air, must tend 

 constantly to impede the process : and it is scarcely possible 

 that carbonaceous matter, if such a cause existed, should not 

 be found in the lava, and be disengaged with the saline or 

 aqueous products from the bocca or craters. There are many 

 instances in England of strata of mineral coal which have been 

 long burning ; but the results have been merely baked clay 

 and schists, and it has produced no result similar to lava. 



If the idea of Lemery were correct, that the action of sul- 

 phur on iron may be a cause of volcanic fires, sulphate of iron 

 ought to be the great product of the volcano ; which is known 

 not to be the case ; and the heat produced by the action of 

 sulphur on the common metals, is quite inadequate to account 

 for the appearances. When it is considered that volcanic fires 

 occur and intermit with all the phenomena that indicate in- 

 tense chemical action, it seems not unreasonable to refer them 

 to chemical causes. But for phenomena upon such a scale, 

 an immense mass of matter must be in activity, and the pro- 

 ducts of the volcano ought to give an idea of the nature of the 

 substances primarily active. Now what are these products ? 

 Mixtures of the earths in an oxidated and fused state, and in- 

 tensely ignited ; water and saline substances, such as might be 

 furnished by the sea and air, altered in such a manner as might 

 be expected from the formation of fixed oxidated matter. But 

 it may be said, if the oxidation of the metals of the earths be 

 the causes of the phenomena, some of these substances ought 



occasionally 



