in the Pacific, ^c. 77 



great thickness of the reefs, to have been formed by a gradual 

 and long continued subsidence of the original shelf of coral, 

 while the surface was maintained at the same level as at first, 

 by the unceasing additions made by the polypes. Carrying 

 out this principle, he attributes the peculiar conformation of 

 lagoon islands to the operation of similar causes. That is to 

 say, he considers that the site of those islands of such a char- 

 acter, now sprinkled over the whole vast coralliferous belt of 

 ocean, was once occupied by islands of various elevation, sur- 

 rounded as many of the same class now are, by a fringing or 

 shore reef ; that as these have slowly sunk, the reef has grad- 

 ually receded from the shore, and on their total disappearance 

 left the lagoon only to mark the place of their existence. 

 Thus the coral islands instead of being looked upon as the 

 germs of a new continent, should be contemplated as the 

 wrecks, or rather as beacons, pointing out where lie the wrecks 

 of one, long since 



"In the deep bosom of the ocean buried.'' 



Having personally examined a large number of these 

 islands, and also resided eight months among the volcanic 

 class having shore and partially encircling reefs, I may be per- 

 mitted to state that my own observations have impressed a 

 conviction of the correctness of the theory here advanced by 

 Mr. Darwin. Indeed without being aware at the time that 

 such views were entertained by any one else, but failing 

 to discover in any author a satisfactory elucidation of the 

 apparent anomalies they exhibited, I was led, more than two 

 years ago, by a comparison of the features presented by the 

 reefs of Tahiti with those of the Dangerous Archipelago and 

 Paumotu Group, (of which I had just enjoyed an opportunity 

 of examining a very considerable number,) to similar conclu- 

 sions as to their origin, with those recently published by that 

 gentleman ; though not to entertain his opinions respecting 

 limited and definite areas of subsidence and elevation. 



My observations in MS. on this subject are now in the pos- 

 session of the Navy Department at Washington ; but not 

 being permitted to have access to them, I am compelled, in 



