22S THE EARTirs INTERIOR. 



in spite of occasional earthquakes and volcanic 

 eru])tions, the inhabitants of this peaceful and 

 eas^'-going planet so greatly pride themselves, 

 once passed, for its own part, through a similar 

 stage of molten rock, and only slowly settled 

 down, like all the rest of us, into a placid, calm, 

 and respected old age. It was natural to conclude, 

 therefore, that the earth's interior consisted really 

 still of liquid fire, and that the solid crust, which 

 composes to most of us all that we ever think of as 

 the world, was the cooled surface of an internally 

 igneous and distracted mass. We walk, said geol- 

 ogists, with perfect confidence, and, on the whole, 

 justly so, upon the thin and quivering caked ex- 

 terior of an indescribably hot and molten globe. 

 A few miles of hardened outside, at best, divide us 

 from a vast core of unspeakable fire ten thousand 

 times hotter than the hottest furnace. And that 

 the seething mass thus pictured as the earth's 

 main body was really liquid, a tremendous sea of 

 white hot molten material, was until lately the al- 

 most universal belief, expressed or implied, of all 

 the greatest and most learned geologists. 



Still later, however, new trains of physical 

 reasoning were brought to bear upon the correc- 

 tion and rectification of this somewhat crude and 

 unfixed idea. For if the earth's molten centre 

 were really liquid, how was it, people asked, that 

 the solid crust was able to float upon it, instead 



