50 THE SEA-SHORE 



covered rocks, which sometimes run far out into 

 the sea. Well, those rocks were not always 

 rocks. They were once the bottoms of cliffs. 

 But the piddocks and the sea, working together, 

 cut the cliffs down ; so that the sea gained, yard 

 by yard, upon the land. 



Indeed, I think that it may be said, quite truly, 

 that if it had not been for the work of the pid- 

 docks Great Britain would not be an island ! At 

 any rate we do know this, that once, a great many 

 hundreds of thousands of years ago, Great Britain 

 was not an island at all, but was joined to the 

 mainland of the Continent of Europe. And we 

 also know that the sea, acting by itself, could not 

 possibly have cut a passage through what we now 

 call the Straits of Dover. The piddocks helped it 

 to do so ! They kept on cutting away the founda- 

 tion of the cliffs by boring backwards and forwards 

 through the solid chalk, just below the level of the 

 waves ; and the sea finished the work which the 

 piddocks had begun, by breaking down the thin 

 dividing walls between their burrows. 



PLATE XVII 



THE LITTLE PIDDOCK (2 and 3) 



The common piddock grows to a length of from 

 three to five inches, and is almost always white 

 in colour, though sometimes it is stained by the 



