2C2 THE OCEAN. 



sink to the bottom of tne Ocean. Now, the water 

 which is continually thrown into the lagoon by the 

 surf breaking over the reef, can find an outlet only 

 through the openings of which I am speaking ; and 

 thus a constant current is maintained through them, 

 and particularly at the sides, where the opposing 

 waves offer less resistance, carrying out some of the 

 sediment, and depositing it in its course on the coral 

 margins of the aperture. The coral sand made by 

 these abraded fragments is quickly cemented by the 

 influence of the sun into a solid mass, where exposed 

 to the air ; and it is, perhaps, owing to this property, 

 that the numberless little islets are formed along the 

 reef, even where there is no aperture. The surf in 

 violent gales can roll up upon the reef masses of 

 torn-off coral, weighing many hundredweights ; such 

 a mass, once lodged, would be the nucleus of an islet ; 

 the sand would speedily accumulate around it, which 

 the sun would soon cement into a mass, and then 

 the islet would be ready for vegetation. 



The following lines are beautifully descriptive 

 of the formation of an atoll, though the author 

 seems to hold the erroneous notion of the wholo 

 structure being elevated from the bottom by the 

 coral polypes : — ■ 



" Millions of millions thus, from nge to age, 

 With simplest skill, and toil unweariable, 

 No moment and no movement unimproved, 

 Laid line on line, on terrace terrace sprtad, 

 To swell the heightening, brightening, gradual mound, 

 By marvellous structure climbing tow'rds the day. 

 Each wrought alone, yet all together wrought ; 

 Unconscious, not unworthy, instruments. 



