196 AUGUST. 



generation after generation; each new-born shell-fish 

 makes a new bore for itself, never appropriating one 

 ready-made, and so there is a perpetual excavation of 

 the living rock with these shallow auger-holes, always 

 of the same width, or nearly ; about half-an-inch. The 

 result is what we see ; that the surface of the rock 

 knows no such thing as a plane surface, but a surface 

 covered with smooth borings, running in all directions, 

 so as continually to break in on one another ; and that 

 so close together, that the interspaces form narrow 

 knife-edges, and sharp angles and projecting points. 

 A particularly interesting circumstance is, that this 

 honeycombed condition is characteristic not only of 

 that level of the rock which is covered by the sea for 

 some portion of eveiy tide, but of that part, to a certain 

 height, which is never covered at all The Mollusca, it 

 is true, cannot live wholly deprived of sea- water, and, 

 in fact, there are none in this ever- dry portion, though 

 the burrows by thousands testify that they were there 

 once. We must infer that the coast has been generally 

 elevated ; perhaps by slow and imperceptible degrees, by 

 an operation still proceeding but unappreciated ; per- 

 haps by some sudden convulsion which took place at a 

 remote era, unrecorded and forgotten. 



When once raised beyond the level of the highest 

 tide, the eroded surface apprars to have a permanency 



