330 CORALS AND CORAL ISLANDS. 



HI. EFFECT OF THE SUBSIDENCE. 



The facts surveyed give us a long insight into the past, 

 and exhibit to us the Pacific once scattered over with lofty 

 lands, where now there are only humble monumental atolls. 

 Had there been no growing coral, the whole would have 

 passed without a record. These permanent registers, exhibit 

 in enduring characters some of the oscillations which the 

 " stable " earth has since undergone. 



From the actual size of the coral reefs and islands, we 

 know that the whole amount of high land lost to the Pacific 

 by the subsidence was at the very least fifty thousand square 

 miles. But since atolls are necessarily smaller than the land 

 they cover, and the more so, the further subsidence has pro- 

 ceeded ; — since many lands, owing to their abrupt shores, 

 or to volcanic agency, must have had no reefs about them, 

 and have disappeared without a mark ; and since others may 

 have subsided too rapidly for the corals to retain themselves 

 at the surface ; it is obvious that this estimate is far below 

 the truth. It is apparent that in many cases, islands now 

 disjoined have been once connected, and thus several atolls 

 may have been made about the heights of a single subsiding 

 land of large size. Such facts show additional error in the 

 above estimate, evincing that the scattered atolls and reefs tell 

 but a small part of the story. Why is it, also, that the Pa- 

 cific islands are confined to the tropics, if not that beyond 

 thirty degrees the zoophyte could not plant its growing reg- 

 isters ? 



The island of Ponape, in the Caroline Archipelago, affords 

 evidence of a subsidence in progress, as Mr. Horatio Hale, the 

 Philologist of the Wilkes Expedition, gathered from a for- 

 eigner who had been for a while a resident on this island. 



