204 THE OCEAN. [Book IX. 



interior of the earth, the outer shell, not being 

 sufficiently strong to resist the power of gravitation 

 and support itself, must either bend or break, so as 

 to accommodate itself to the reduced circumference 

 which it has to enclose. A glance round the world 

 shows that it has bent all over, and in many places 

 broken. In some parts the bending is only sufficient 

 to form gentle, easy undulations ; in other places, 

 sufficient to form hills and valleys ; and where the 

 surface, after bending as much as its pliancy would 

 admit of, has at length broken, the broken edges, 

 crushing against each other, have piled up mountain 

 ranges of broken strata ; or, in other places, the 

 inward pressure of the stratified surface has forced 

 the liquid matter from below upwards through the 

 crack, forming chains of unstratified mountains. 



