254 THE 0CEA2i. 



A close inspection will likewise show that the outline 

 of the whole reef possesses much less regularity of 

 form than its aspect from a distance indicated. The 

 form, however, is invariably a more or less close 

 approach to a circle. Sometimes the land is con- 

 tinuous through the whole circumference, with the 

 exception of a channel or two into the lagoon, which 

 presents the appearance of a circular pond with a 

 verdant border surrounding it ; again, another atoll 

 will be found which has brought its ring of reef 

 scarcely to the surface, exposing, perhaps, a single 

 bare spot on the windward edge at the lowest ebb of 

 spring tide. 



Captain Basil Hall, in his Voyage to Loo-Choo, has 

 recorded some pleasing observations on this singular 

 formation. He says — 



" The examination of a coral reef during the dif- 

 ferent stages of one tide, is particularly interesting. 

 When the sea has left it for some time it becomes 

 dry, and appears to be a compact rock, exceedingly 

 hard and rugged ; but no sooner does the tide rise 

 again, and the waves begin to wash over it, than 

 millions of coral worms protrude themselves from 

 holes on the surface, which were before quite in- 

 visible. These animals are of a great variety of 

 shapes and sizes, and in such prodigious numbers 

 that in a short time the whole surface of the rock 

 appears to be alive and in motion. The most com- 

 mon of the worms at Loo-Choo was in the form of a 

 star, with arms from four to six inches long, which 

 it moved about with a rapid motion in all directions, 

 probably in search of food. Others were so sluggish 



