TERRESTRIAL PHENOMENA. 



supposing, with Fourier, the process of consolidation to 

 have commenced by radiation into space from the cool- 

 ing surface, the particles nearer to the center of the Earth 

 would have continued fluid and incandescent. After long 

 transmisson of heat from the center towards the surface, a 

 stable condition of the temperature would have been esta- 

 blished, when the heat would increase uninterruptedly with 

 increasing depth. The high temperature of water which 

 rises in very deep borings in Artesian wells, direct obser- 

 vation of the temperature of rocks in mines, and, above all, 

 the volcanic activity of the Earth, ejecting molten masses 

 from opened clefts or fissures, bear unquestionable evidence 

 to this increase for very considerable depths in the upper 

 terrestrial strata. Inferences, which are indeed founded 

 only on analogy, render the extension of this increase farther 

 towards the center more than probable. That which has 

 been learnt respecting the propagation of heat in homo- 

 geneous metallic spheroids, by means of an ingenious 

 analytical calculus perfected expressly for this class of in- 

 vestigations, ( l37 ) can only be applied with great caution to 

 the actual constitution of our planet, considering our igno- 

 rance of the substances of which the Earth may be com- 

 posed, of the different capacity for heat and conducting 

 power of the superimposed masses, and of the chemical 

 changes which solid and fluid matter may undergo from 

 enormous pressure. That which is most difficult for us to 

 conceive and to represent to ourselves, is the boundary line 

 between the fluid interior mas.s and the solidified rocks 

 which form the outer crust ; or the gradual change from 

 the solid strata to the condition of semi-fluidity, a 

 condition to which the known laws of hydraulics can only 



