458 FORMATION OF ATOLLS. [chaF 



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 une meruille de voir chacun de ces 

 atollons, enuironn^ d'un grand banc de pierre tout autour, 

 n'y ayant point d'artifice humaln." A mere sketch can 

 give 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 instinctively built up their great circles to afford 

 themselves protection 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. Moreover, on this 

 view, many species of distinct genera and families are 

 supposed to combine for one end ; and of such a combina- 

 tion, 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 forty-four geographical 

 miles in diameter in one line, by thirty -four miles in 

 another line ; Rimsky is fifty -four by twenty miles across, 

 and it has a strangely sinuous margin ; Bow atoll is thirty 

 miles long, and on an average only six in width ; Menchicoff 

 atoll consists of three atolls united or tied together. This 

 theory, moreover, is totally inapplicable to the northern 

 Maldiva atolls in the Indian Ocean (one of which is eighty- 

 eight miles in length, and between ten and twenty in 

 breadth), for they are not bounded like ordinary atolls by 

 narrow reefs, but by a vast number of separate little atolls ; 

 other little atolls rising out of the great central lagoon-like 

 spaces. A third and better theory was advanced by 

 Chamlsso, who thought that from the corals growing 

 mbre vigorously where exposed to the open sea, as 

 undoubtedly is the case, the outer edges would grow up 



