70 



a considerable time before the waters resumed their state of 

 equilibrium. 1 The sudden dislocation in New Zealand is, however, 

 admitted by Sness. 2 Another similar case is reported from 

 Western North America, by G. K. Gilbert * He says: „The 

 fault-scarps 4 of the Wasatch follow the western base. Those of 

 the Sierra Nevada follow the eastern base; and it happens that 

 one of them has been formed since the settlement of the 

 country. It occurred in 1872, and produced one of the most 

 notable earthquakes ever recorded in the United States. The 

 height of the scarp varies from five to twenty feet, and its 

 length is forty miles. Various tracts of land were sunk a 

 number of feet below their previous positions, and one tract, 

 several thousand acres in extent, was not only lowered, but car- 

 ried bodily about fifteen feet northward." We have, therefore, 

 at least two undoubted cases reported of a visible dislocation io 

 the solid rocks during earthquakes. 



Loose alluvial masses are sometimes displaced by earth- 

 quakes. This occurred in the Mississippi delta during an earth- 

 quake in 1811, and in the Ran of Kachh in India 1819. And 

 in Achaja, in 1858, littoral sediments were, by an earthquake in 

 the underlying massive rocks, suddenly submerged by a gli- 

 ding movement, so that in some places only the tops of the 

 trees were visible above the sea. 5 



In such cases the earthquakes are accompanied by visible 

 dislocations of the crust of the earth. And we must indeed 

 believe that earthquakes are caused, in general, by dislocations. A 

 dislocation of a few decimetres can, in many cases only be ob- 



