58 VULCANISM ITS NATUEE AND FUNCTION. 



indicating a slow and long -continued movement of the 

 solid crust in the region where it occurs, in contradis- 

 tinction to the volcano and earthquake, whose operations 

 are sudden and convulsive. "Whether these gradual crust- 

 movements result from the same igneous forces that give 

 rise to the earthquake and volcano is a matter open to 

 question, but in the present state of our knowledge we can 

 perceive no other adequate cause, and are therefore com- 

 pelled to associate them with the same pervading vulcan- 

 icity. Along the coasts of our own islands, and indeed 

 along the coasts of every other country, the attentive ob- 

 server will perceive at various levels above the present 

 sea-beach several shelves or terraces, which meet the eye 

 like reaches of former shore-line. On closer inspection, 

 their parallelism, the sand and gravel of which they are 

 composed, the shells, bones, and other marine exuviae which 

 they contain, prove incontestably that the sea formerly 

 stood at these levels, and that the land to this extent has 

 been successively elevated above the waters. Whether 

 such elevations took place suddenly or by slow degrees it 

 is often impossible to tell, but it is readily seen from the 

 old beaches and the cliffs that guard them that the sea 

 must have long stood at their successive levels. If the 

 movement takes place suddenly like that which during 

 the present century elevated the coast of Chile to the 

 height of eight or ten feet, or that which depressed the 

 Eun of Cutch, or that which more recently uplifted part of 

 the north island of New Zealand to the height of six feet or 

 thereby it is generally ascribed to earthquake convulsion ; 

 but if it occurs by slow stages it is regarded as crust-motion, 

 the proximate cause of which is at present unknown. 



As notable instances of this crust-motion we may point 

 to the shores of Scandinavia, which have been long known 

 to be rising at a slow and equable rate ; to the raised beaches 



