CRUST-M 



Lisbon earthquake in 1755 was 

 and the succession of such waves (three in number) that 

 desolated the town of Simoda (Japan) in 1854 were little 

 inferior in violence and dimensions. 



On the whole the effects of the earthquake are much more 

 disastrous than those of the volcano. The discharges of 

 the one, being at considerable altitude, are chiefly felt for a 

 few miles round its crater or in long narrow streams down 

 its sides ; but the other convulses for leagues, and this at 

 all levels and alike over land and over sea. The two, how- 

 ever, are usually in close connection; and in centres of 

 igneous activity, when the volcano begins to discharge, the 

 convulsions of the earthquake cease, or at all events lose 

 much of their intensity. The one acts as a sort of safety- 

 valve to the other, and this necessarily so if we regard them 

 as both arising from the same deep-seated source of igneous 

 intensity. This connection was long ago noticed by Dr 

 Hutton, who quaintly but somewhat bitterly remarks " A 

 volcano is not made on purpose to frighten superstitious 

 people into fits of piety and devotion, nor to overwhelm 

 devoted cities with destruction. A volcano should be con- 

 sidered as a spiracle to the subterranean furnace, in order to 

 prevent the unnecessary elevation of land and fatal effects 

 of earthquakes. And we may rest assured that they, in 

 general, wisely answer the end of their intention, without 

 being in themselves an end, for which nature had exerted 

 such amazing power and excellent contrivance." 



The third great manifestation of the reaction of the 

 earth's interior upon its external crust consists in those 

 slow movements by which certain portions of the land are 

 stage by stage elevated above the waters, and other por- 

 tions as gradually depressed beneath them. To this 

 manifestation we may apply the name of Crust-Motion, as 



