Central Heat of the Earthy and Volcanic Phenomena. 135 



facts in favour of the idea that the interior of the globe has 

 a higher temperature than the surface ; the heat increasing 

 in mines the deeper we penetrate, and the number of warm 

 sources which rise from great depths in almost all countries, 

 are certainly favourable to the idea."* 



From the above quotation, which embraces the substance 

 of all objections as yet brought forward, it would appear 

 that they are founded upon the fact, deduced from observa- 

 tion, that there is an internal heat for which at the present 

 time no satisfactory explanation can be given by the advo- 

 cates of the chemical theory. That chemistry has as yet 

 failed to give the explanation referred to, is beyond doubt, 

 but that this should render null and void the probability of 

 the chemical theory accounting for volcanic phenomena, is 

 carrying the inference rather too far. No substantial objec- 

 tion has, so far as I am aware, been brought forward against 

 the probability of volcanic phenomena being caused by chemi- 

 cal action and reaction ; whereas many objections have been 

 directed to shew that the production of the central heat by 

 chemical means was untenable, and then the inference was 

 drawn that both effects were the result of one cause, and that 

 what failed to account for the one could not account for the 

 other. 



Internal heat and volcanic phenomena I ascribe to two 

 different causes ; and while I believe that chemical action 

 is quite competent to account for volcanic phenomena, at 

 the same time I conceive that the internal heat is not directly 

 due to this force, but is the inevitable consequence of the 

 matter composing the crust being at such a short distance 

 from the central nucleus. In the spheroidal theory of the 

 earth such an internal heat is fully accounted for, in the 

 proximity of the crust to the central nucleus. But while the 

 heat of the inner portion of the crust is attributable to the 

 central nucleus, there is no physical contact, and therefore 

 little or no possibility of fused matter being ejected from the 

 central sphere through the crust. 



* Collected works of Sir H. Davy, by Dr John Davy.—Consolations in Travel, 

 Dialogue 3, p. 295. 



