Remarks on Volcanoes. 281 



coinpanying them, result from an oxidation of alkaline and 

 earthy metals, determined by a decomposition of water, it 

 admits of being proved, that the quantity of the hydrogen 

 evolved from volcanoes, bears a perfect relation to the mag- 

 nitude of the streams of lava formed." 



A single one of the vapour springs of Krisuvik yields, ac- 

 cording to Bunsen's own calculations, about twelve cubic 

 metres of hydrogen in twenty-four hours. 



" Assuming, then, that the remaining innumerable springs, 

 together with the large fumaroles occurring there, yield to- 

 gether a quantity only 100 times as great, which may safely 

 be regarded as far less than the quantity of this gas which is 

 actually evolved, we may, by means of this assumption and 

 simple calculation, shew that the formation of lava, which 

 would be equivalent to such an evolution of gas within the 

 period which elapses between two great eruptions, is suffi- 

 cient to produce immense streams of lava." 



" Nor is it any longer possible to attach importance to the 

 second of the principal objections which have been made to 

 Davy's hypothesis, namely, that it is unusual to observe any 

 sensible appearance of flames during great volcanic eruptions. 

 For if, from the known composition of the first-mentioned 

 fumarole gas, we estimate the temperature of its flame, we 

 find it to be 305° 6' ; consequently a temperature which is far 

 below the. point of ignition of hydrogen. These gases are, 

 therefore, combustible only at a red heat, and even under 

 the most favourable circumstances can only produce by such 

 a combustion an increase of temperature amounting to 305° 6', 

 which in a red heat must necessarily altogether escape ob- 

 servation by the eye." 



Satisfied with having obtained the weighty testimony of 

 Professor Bunsen in favour of the facts which I had alleged 

 in confirmation of the theory to which I had given my ad- 

 hesion, I shall the less regard the opposition that exists be- 

 tween my views and his with respect to the source of the 

 hydrogen evolved. 



Professor Bunsen derives this gas from the process in which 

 pyroxenic lava is converted into palagonite through the 



