THE EARTH'S INTERIOR. 229 



of sinking through it? Consider the vast extent 

 of the pressure exercised by whole solid square 

 miles of rock and mountain superimposed upon a 

 liquid central body. Could any one believe for a 

 moment that even a single mountain, much less 

 a whole hemisphere, could be so supported upon 

 a sea of liquid? This vast weight ft)rever press- 

 ing down upon the hot interior must surely reduce 

 it, however high its temperature, to the condition 

 of a solid, by mere force of gravity and condensa- 

 tion. You can press a gas till it assumes the form 

 first of a liquid and then of a solid ; you can reduce 

 carbonic acid itself, which looks and feels as thin 

 as air, first to the condition of a body like water, 

 and then to a solid resembling ice. If the mere 

 slight pressure which man's mechanical appliances 

 enable him to effect can produce such solidifj'ing 

 results as this, what are we to believe must be 

 done by the crushing weight of whole seas and 

 continents, hemispheres and oceans, piled on top 

 of the supposed fiery Mediterranean? No; the 

 idea of a liquid centre to the earth becomes clearly 

 impossible when viewed in the rational light of 

 modern physics ; however great the original heat 

 due to the falling together of the earth's atoms, 

 and that due to the pressure itself, the centre 

 cannot even so be regarded as liquid; it must be 

 squeezed solid by the enormous mass of mountains 

 and seas imposed on top of it, with their incalcu- 



