84 INTERNAL HEAT OF THE EARTH, 



/9. Internal Heat of the Earth, and its Distribution. 



(Enlargement of the Representation of Nature in Kosmos, 

 Bd. i. S. 179 184, 425427, Anm. 730; Engl. 

 Vol. i. p. 161167 and p. 405407 ; Notes 137140). 



Considerations respecting the internal heat of the earth, the 

 importance of which has been so much enhanced by their 

 now so generally acknowledged connection with volcanic 

 action and phsenomena of elevation, are based partly on 

 direct, and therefore incontestable observation of tempera- 

 tures in spring?, borings, and mines ; and partly on analytical 

 combinations respecting the gradual cooling down of our 

 planet, and the influence which the diminution of tempera- 

 ture may have exercised on its velocity of rotation,( 30 ) and 

 on the direction of internal thermal currents in primeval 

 time. The form of the flattened terrestrial spheroid is itself 

 again dependent on the law of increasing density in con- 

 centric superimposed non-homogeneous shells. The first- 

 mentioned, which is the experimental, and therefore more 

 assured portion of the investigation to which we here confine 

 ourselves, can, however, only shed light on the earth's 

 crust of inconsiderable thickness ; while the second, which 

 is the mathematical part of the inquiry, is, from the nature 

 of its applications, suited to afford negative rather than 

 positive results. Offering the charm which is afforded by 

 sagacious combinations of thought, ( 31 ) it leads to problems 

 which, together with conjectures respecting the origin of 

 volcanic forces, and the reaction of the molten interior 

 against the solid outer shell, or crust, cannot remain altogether 

 unnoticed. Plato's geognostic myth of the Pyriphlege- 

 thon,( 32 ) as the origin or fount of all hot springs and volcanic 



