Cu. XX.] 



ACTION OF THE SEA. 



505 



while the matrix in which they were enclosed, being of the 

 same substance, but of a firmer texture, has remained un- 

 altered. Thus, long narrow ravines, sometimes twenty feet 

 wide, are laid open, and often give access to the waves. 

 After describing some huge cavernous apertures into which 



Fig. 40. 



Grind of the Navir— passage forced by the sea through rocks of hard porphyry 



Hibbert 



enumerates 



A mass of 



rock, the average dimensions of which may perhaps be rated 

 at twelve or thirteen feet square, and four and a half or five 



moved from 



since 



turned over. 



$ forced 

 sublime 



But 



escaping the process of disintegration that is devastating the 



ram 



the inroads of the ocean ;— the Atlantic, when provoked by 

 wintry gales, batters against it with all the force of real 

 artillery — the waves having, in their repeated assaults, forced 

 themselves an entrance. This breach, named the Grind of 



