About the Long Past 



of pulling land to pieces, is checked ; for let the 

 waves strive as they may to wear away a coast- 

 line, a very slight upheaval is enough to counter- 

 balance their utmost exertions. 



Such changes are usually gradual so quiet, 

 so deliberate, as only to become apparent in the 

 course of centuries. 



Not that crust-movements are always sluggish. 

 The ceaseless sinking and crinkling of vast 

 extents of country, the crowding together into 

 a smaller space of immense masses of material, 

 cannot but cause enormous pressure ; and here 

 or there a portion suddenly gives under the 

 strain. Then the ground shakes and heaves, 

 or some terrible landslip takes place. 



Earthquakes are now looked upon generally 

 as signs of abrupt yielding to intense pressure. 

 Sometimes they indicate that a huge weight of 

 material deep down has slid to a lower level, 

 packing more closely or pushing aside other 

 masses, and causing what miners call "a fault" 

 that is a break or dislocation in the regular 

 lines of the stratified rocks. Or slip after slip 

 may take place, one mass being disturbed by 

 the movements of a neighbouring mass ; and so 

 the ground above may tremble again and again 

 with recurring shocks. 



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