THE PROBABLE CONDITION OF THE EARTH'S INTERIOR. 7 



of the liquid, and its constantly increasing density ; while the heat imparted 

 to the sinking material would tend to bring it to about the same specific 

 gravity with the liquid portion as the sinking mass neared its melting point. 

 But — what is of still greater importance — the sinking material would 

 soon reach a liquid of different composition and greater density than the 

 crust; and farther than this it could not sink. That sinking of the crust 

 to the centre, which Sir William Thomson supposed would take place, could 

 only do so in case the hot solid was heavier than the liquid interior, and 

 that liquid homogeneous. But both these conditions appear opposed to 

 what we know of the properties of matter and of the heterogeneous com- 

 position of the earth. 



The structure of the earth that would naturally follow, from what has 

 been above stated, would be a heterogeneous crust floating on a den.ser 

 heterogeneous liquid, and one which the interior pressure tends to keep 

 liquid at a lower temperature than on the surface, so far as it affects it 

 at all. 



In an earth like this, owing to the gradual passage of the crust into the 

 viscous liquid interior, no shrinking of the nucleus from the exterior could 

 take place, but the earth would contract as a whole. A linear shortening 

 of the crust would occur that would crush it together, and cause its depres- 

 sion in some places and its elevation in others. The depression of any por- 

 tion of the crust into the li([uid interior would naturallj^ cause an equivalent 

 weight of the heavier liquid to rise, and perhaps overllow. This simple 

 sinking of a portion of the crust on one side with its corresponding but less 

 elevation on the other, with the attendant Assuring, would afford all 

 the dynamic agencies needed to raise lavas to the tops of our highest 

 mountains, and would account for the association of volcanoes with de- 

 pressed basins, for fissure eruptions, etc.* The contraction could hardly 

 be expected to be equal in every portion, while the depression of portions 

 of the crust with the attendant outflows would cause an unequal thickness 

 of the crust, with great irregularities in its base adjacent to the liquid in- 

 terior. The outflows, themselves, would cause this crust to be tied through 

 and through by the different eruptive materials, 



This great irregularity in thickness, which the earth's crust is supposed 

 to present, coupled with the viscosity of its interior portion next the crust, 

 would apparently prevent any direct or special connection between different 



* Whituey, Eartliquakes, Volcanoes, and Mountaiii-Buikliiig, p. 90. 



