the Chemical Theory of Volcanos. 15 



former publications in this Journal concerning the natural 

 history of volcanos and earthquakes, I flatter myself that I 

 have shewn, as far as it is possible to elucidate a subject which 

 is beyond the limits of direct observation, and which can for 

 the most part only be mentally appreciated, that watery va- 

 pours may be supposed to be the means by which nature is 

 able to carry melted masses from the greatest depths to the 

 surface of the earth. Any hypothesis endeavouring to explain 

 the volcanic action, must embrace watery vapours or other 

 elastic fluids, in order to account for the rising up of lava. 

 The theory in question, consequently, reduces the explanation 

 of the phenomena presented to the most simple point. 



Let us now consider, somewhat minutely, the theory which 

 ascribes volcanic actions to chemical processes taking place 

 between bodies having a powerful affinity for each other, and 

 by which so considerable a heat is produced as to melt lava. 

 First, the advocates of this hypothesis must be asked, whether 

 they are inclined to deny a high internal heat of the globe in- 

 creasing with the depth to the point of melted lava, or 

 whether they suppose chemical changes supported by this in- 

 tense temperature ? Admitting for an instant the former case, 

 all the heat required to melt lavas must be produced by these 

 actions. Professor Daubeny seems to be inclined to suppose 

 this ; for, to my objections that these metals are not sufficient- 

 ly oxidizable to kindle on the access of water, he replies, that 

 silicon is combustible when united either with a little hydro- 

 gen or with alkaline carbonates, and that calcium and mag- 

 nesium appear to be still more inflammable. The Professor 

 seems, therefore, not to consider the internal heat as a co- 

 operative power, but to think it possible that the metals, even 

 at a common temperature, generate heat enough, by combin- 

 ing with oxygen, to melt the produced earths. 



It is scarcely possible to confirm or to refute this assertion 

 in an experimental way. Indeed, the combustion of a mix- 

 ture of the earthy and alkaline metals, in such proportions as 

 are contained in lava, would give a satisfactory conclusion only 

 by applying these metals in such large quantities, that the 

 heat absorbed by surrounding bodies should be insignificant in 

 proportion to that which is generated. Supposing, on the 



