Volcanoes, 435 



water at common temperatures, it may be boiled in that fluid. 

 But there is every reason to believe that silicon is not a metal, 

 but has a closer resemblance to carbon, a non-metallic sub- 

 stance. But, however this may be determined, it is so far 

 from alloying with the metals, that it has no tendency to unite 

 with other bodies, except when in a nascent state, or when 

 double affinities are exerted. We cannot help remarking 

 that it was only a short time after Berzelius had discovered 

 the properties of silicon, that Davy renounced his theory. A 

 consideration of the properties of aluminum is equally fatal 

 to the theory ; for it sustains no visible alteration by long boil- 

 ing in water, even when in the state of fine powder, and only 

 begins to oxidise when its temperature is raised to a red heat. 

 Of calcium and iron we need not speak : the former is only 

 an imaginary substance, and the properties of iron are too 

 well known to require a remark. 



That any compound of these substances, in any propor- 

 tion, should fulfil the conditions required in the theory, is 

 utterly impossible. It is true that metallic alloys are more 

 oxidisable than pure metals ; but we have given a reason for 

 the supposition that, if the substances of which we have spoken 

 were existent in a deoxidised state, it would not be in union 

 with each other. If it could be imagined that the earth was 

 originally a ball of potassium, there might be some reasons 

 to support the theory, for then the decomposition of water, 

 and the burning of potassuretted hydrogen, might be supposed 

 to mimic the exhibitions of Etna, if not of Tomboro. But, 

 as the constituent elements of lava evince no tendency to act 

 agreeably to the requisitions of the theory which we have 

 examined, we ought not to give them properties which do not 

 belong to them. 



Dr. Daubeny has modified the details of this theory. He 

 admits that the action of water is not of itself sufficient to 

 account for all the phenomena, and introduces the agency of 

 atmospheric air. But it must be quite evident that, if our 

 objections to Davy\s theory be sound, they are equally so as 

 applied to Dr. Daubeny's amendment. No one would have 

 a theory of volcanic action suggested from pouring water 

 upon a cold cannon shot, yet the chemical action is as strong 

 in this instance as that which would be produced upon the 

 unoxidised nucleus of the earth. Iron is much more readily 

 oxidised than the bases of silica and alumina; for in a spongy 

 state it will decompose water, and become red hot, on being 

 exposed to the air at common temperatures. We no more 

 believe that this theory can be received as an explanation of 

 the cause of volcanic action, than Southey's assertion as a 



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