1836.] LAGOON-ISLANDS, OR ATOLLS. 339 



of various minute and tender animals ! This is a wonder which does 

 not at first strike the eye of the body, but, after reflection, the eye of 



I will now give a very brief account of the three great classes of 

 coral-reefs ; namely, Atolls, Barrier, and Fringing-reefs, and will explain 

 my views * on their formation. Almost every voyager who has crossed 

 the Pacific has expressed his unbounded astonishment at the lagoon- 

 islands, or as I shall for the future call them by their Indian name of 

 atolls, and has attempted some explanation. Even as long ago as the 

 year 1605, Pyrard de Laval well exclaimed, " C'est unemeruille de voir 

 chacun de ces atollons, enuironne" d'un grand bane de pierre tout autour, 

 n'y ayant point d'artifice humain." The accompanying sketch of 

 Whitsunday Island in the Pacific, copied from Captain Beechey's 

 admirable Voyage, gives but a faint idea of the singular aspect of an 

 atoll ; it is one of the smallest size, and has its narrow islets united 



together in a ring. The immensity of the ocean, the fury of the breakers, 

 contrasted with the lowness of the land and the smoothness of the 

 bright green water within the lagoon, can hardly be imagined without 

 having been seen. 



The earlier voyagers fancied that the coral-building animals in- 

 stinctively built up their great circles to afford themselves protection m 

 the inner parts ; but so far is this from the truth, that those massive 

 kinds to whose growth on the exposed outer shores the very existence 

 of the reef depends, cannot live within the lagoon, where other deli- 

 cately-branching kinds flourish. Moreover, on this view, many species 

 of distinct genera and families are supposed to combine for one end ; 

 and of such a combination, not a single instance can be found in the 

 whole of nature. The theory that has been most generally received is, 

 that atolls are based on submarine craters ; but when we consider the 

 form and size of some, the number, proximity, and relative positions of 



* These were first read before the Geological Society in May, 1837, and have 

 since been developed in a separate volume on the " Structure and Distribu- 

 tion of Coral Reefs." 



