4 PREFACE. 



the origin of the included channels and lagoons, and of the 

 distribution of reefs, together with a review of the facts with 

 reference to their geological bearing. 



The observations forming the basis of the work were made 

 in the course of the cruise of the Wilkes Exploring Expedi- 

 tion, around the world, during the four years from 1838 to 

 1842. The results then obtained are published in my Report 

 on Zoophytes, which treats at length of Corals and Coral 

 Animals, and in a chapter on Coral Reefs and Islands form- 

 ing part of my Geological Report. 



The opportunities for investigations in this department- 

 afforded by the Expedition, were large. We visited a number 

 of the coral islands of the Paumotu Archipelago, to the north 

 of east from Tahiti ; also, some of the Society, Navigator, and 

 Friendly Islands, all remarkable for their coral reefs; the 

 Feejee Group, one of the grandest regions of growing corals 

 in the world, where we spent three months ; several islands 

 north of the Navigator and Feejee Groups, including the Gil- 

 bert or Kingsmill Group; the Sooloo sea, between Borneo 

 and Mindanao, abounding in reefs ; and, finally, Singapore, 

 another East India reef-region. 



Most agreeable are the memories of events, scenes and 

 labors, connected with the cruise : — of companions in travel, 

 both naval and scientific; of the living things of the sea, 

 gathered each morning by the ship's side, and made the study 

 of the day, foul weather or fair ; of coral islands with their 

 groves, and beautiful life, above and within the waters; of 

 exuberant forests, on the mountain islands of the Pacific, 

 where the tree-fern expands its cluster of large and graceful 

 fronds in rivalry with the palm, and eager vines or creepers 

 intertwine and festoon the trees, and weave for them hangings 

 of new foliage and flowers ; of lofty precipices, richly draped, 



