466 



LAGOON-ISLANDS, 



[chap. XX. 



de Laval well exclaimed, " C'est une meruille de voir chacun 

 de ces atollons, enuironne d'un grand banc de pierre tout autour, 

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

 of Whitsunday Island in the Pacific, copied from Capt. Beechey'g 

 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 

 arid 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 

 instinctively built up their great circles to afford themselves pro- 

 tection in 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 delicately-branching kinds flourish. More- 

 over, 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 

 others, this idea loses its plausible character : thus, Suadiva atoll 

 is 44 geographical miles in diameter in one line, by 34 miles in 

 another line ; Bimsky is 54 by 20 miles across, and it has a 

 strangely sinuous margin ; Bow atoll is 30 miles long, and on an 

 average only 6 in width ; MenchicofF atoll consists of three atolls 

 united or tied together. This theory, moreover, is totally inap- 



