2o8 PHYSIOGRAPHY. [chap. 



about eight feet in breadth. Each pit is a pear-shaped hole, 

 and at the bottom of the hole, which is the widest part, there 

 may generally be found the two halves, or valves, of a shell 

 not unlike that of the common mussel. Exactly the same 

 kind, or species of shell-fish^ as that represented in the 

 cavities of the marble, is found to-day living in the Medi- 

 terranean, where it may be seen boring its way into lime- 

 stone rocks, much in the same manner that the so-called 

 " shipworm " bores into timber. There is no difficulty then, in 

 understanding that the perforations in the columns of the 

 temple are the work of boring shell-fish. But it is clear that 

 the columns, when attacked, must have been washed by the 

 sea, for the shell-fish could not have lived in the holes when 

 left high and dry above water. The fact is thus established, 

 that the part of the marble pillars bored by the shells must 

 have been immersed in the sea, long enough for the creatures 

 to have drilled the multitude of holes which are now visible. 

 Here then is evidence of a considerable alteration in the 

 relative level of land and water. It is obvious, however, 

 that such an alteration of level may have been brought 

 about in one or other of two ways : cither the sea may have 

 been raised, or the land may have been carried down. At 

 first sight it appears much more likely that so mobile a 

 thing as the sea has changed its level, than that the surface 

 of the solid earth should have shifted its position. And yet 

 it needs scarcely a moment's consideration to show that 

 any local alteration of sea-level cannot possibly have 

 occurred. For, supposing the surface of the sea to have 

 been raised so as to reach the zone of shell-burrows, the 

 water must then have been forced up into a great heap ; but 

 directly this heap was formed, the particles at the top would 

 press upon those below, and thus urge them down the 



^ Lilhodonnis dactyhis. 



