THE EARTH'S INTERIOR n 



sedimentary beds, or come to the surface from beneath them. 

 Many of them are broken through by igneous rocks. 



Concerning the great interior of the earth, little is known except 

 by inference. From the weight of the earth, 1 it is inferred that its 

 interior is much more dense than its surface. From its 

 behavior under the attraction of other bodies, it is believed to be at 

 least as rigid as steel. Its interior cannot, therefore, be liquid, in 

 the usual sense of that term. From volcanoes, and from the tem- 

 peratures in deep borings, it is inferred that the interior is very hot. 



1 The specific gravity of its outer portion is about 2.7, less than half that of the 

 iMrth a* ;i whole (5.57). 



