INORGANIC GEOLOGICAL DYNAMICS. 609 



effects, and calculations which we can compare with 

 measures. It was found, as we have said, that in 

 descending below the surface of the earth, the tem- 

 perature of its materials increased. Now it fol- 

 lowed from Fourier's mathematical investigations 

 of the distribution of heat in the earth, that if there 

 be no primitive heat, (chaleur d'origine,) the tem- 

 perature, when we descend below the crust, will be 

 constant in each vertical line. Hence an observed 

 increase of temperature in descending, appeared to 

 point out a central heat resulting from some cause 

 now no longer in action. 



The doctrine of a central heat has usually been 

 combined with the supposition of a central igneous 

 fluidity ; for the heat in the neighbourhood of the 

 center must be very intense, according to any law 

 of its increase in descending which is consistent 

 with known principles. But to this central fluidity 

 it has been objected that such a fluid must be in 

 constant circulation by the cooling of its exterior. 

 Mr. Daniell found this to be the case in all fused 

 metals. It has also been objected that there must 

 be, in such a central fluid, tides produced by the 

 moon and sun ; but this inference would require 

 several additional suppositions and calculations to 

 give it a precise form. 



Again, the supposition of a central heat of the 

 earth, considered as the effect of a more ancient 

 state of its mass, appeared to indicate that its cool- 

 ing must still be going on. But if this were so, the 



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