272 SUBSIDENCE OF COllAL-REEFS. 



of the upward growth of the corals duzing the sink- 

 ing of the land,* all the leading features in those 

 wonderful structures, the lagoon islands or atolls, 

 which have so long excited the attention of voya- 

 gers, as well as in the no less wonderful barrier- 

 reefs, whether encircling small islands or stretch- 

 ing for hundreds of miles along the shores of a 

 continent, are sim])ly explained. 



It may be asked whether I can offer any direct 

 evidence of the subsidence of bamer-reefs or atolls ; 

 but it must be bonie in mind how difficult it must 

 ever be to detect a movement the tendency of 

 which is to hide under water the part affected. 

 Nevertheless, at Keeling atoll I observed on all 

 sides of the lagoon old cocoa-nut trees undermined 

 and falling; and in one place the foundation-posts 

 of a shed, which the inhabitants asserted had stood 

 seven years before just above high-water mark, 

 but now was daily washed by every tide : on in- 

 quiry, I found that three earthquakes, one of them 

 severe, had been felt here during the last ten years. 

 At Vanikoro, the lagoon-channel is remarkably 

 deep, scarcely any alluvial soil has accumulated at 

 the foot of the lofty included mountains, and re- 

 markably few islets have been formed by the heap- 

 ing of fragments and sand on the wall-like barrier- 

 reef; these facts, and some analogous ones, led me 

 to believe that this island must lately have sub- 

 sided and the reef grown upwards : here, again, 

 earthquakes are frequent and very severe. In the 



* It has been highly satisfactory to me to find the following 

 passage in a pamphlet by Mr. Couthouy, one of the naturalists in 

 the great Antarctic Expedition of the United States : " Having 

 personally examined a large number of coral-islands, and resided 

 eight months among the volcanic class having shore and partial- 

 ly encircling reefs, I may be permitted to state that my own ob- 

 servations have impressed a conviction of the correctness of the 

 theory of Mr. Darwin." The naturalists, however, of this expe- 

 dition differ with me on some points respecting coral formations. 



