The Interior of the Earth 



care, among which we may quote the follow- 

 ing. 1 



Depth of the Centre 



Date. Locality of the Earthquake. of Disturbance in 



Miles. 



1884 Ischia .62 



1857 Calabria 3.41104.7 



1872 Central Germany 11.18 



1884 Andalusia 11.18 



1887 Genoese Riviera 11.18 



1886 Charleston 18 



1869 Cachar 29.8 



Thus all earthquakes investigated have arisen 

 within the thickness assigned by us to the solid 

 part of the globe. Is this merely an accident? 

 Apparently not. Whether we attribute earth- 

 quakes to the collapse of cavities excavated 

 by the erosion of subterranean waters, or whether 

 we consider them ruptures and dislocations 

 produced by the pressure of internal lavas, 

 striving to force a passage through the fissures 

 of the crust, we must postulate a solid medium. 

 The recent earthquakes in California, which 

 partially destroyed San Francisco, have once more 

 enabled us to ascertain that these cataclysms 

 are always accompanied by a dislocation of the 



1 De Lapparent, Traite de Geologic. 

 135 



