276 TOILERS IN THE SEA. 



growing upwards ; but, as the island sinks, the water 

 will gain inch by inch on the shore, the separate 

 mountains first forming separate islands within one 

 great reef, and finally, the last and highest pinnacle 

 disappearing. The instant this takes place a perfect 

 atoll is formed ; I have said, remove the high land 

 from within an encircling barrier-reef, and an atoll is 

 left, and the land has been removed. We can now 

 perceive how it comes that atolls, having sprung from 

 encircling barrier-reefs, resemble them in general 

 size, form, in the manner in which they are grouped 

 together, and in their arrangement in single or 

 double lines ; for they may be called rude outline 

 charts of the sunken islands over which they stand. 

 We can further see how it arises that the atolls, in 

 the Pacific and Indian oceans, extend in lines parallel 

 to the generally prevailing strike of the high islands, 

 and great coast-lines of those oceans. I venture, 

 therefore, to affirm, that on the theory of the upward 

 growth of the corals, during the sinking of the land, 

 all the leading features in those wonderful structures, 

 the lagoon islands, or atolls, which have so long 

 excited the attention of voyagers, as well as in the 

 no less wonderful barrier-reefs, whether encircling 

 small islands, or stretching for hundreds of miles along 

 the shores of a continent, are simply explained." x 



1 Darwin, "Journal of Researches," p. 473 (1852). 



