in the Pacific^ 6^c. 139 



plateau, but by these elevated islands, like Tahiti and others, 

 having both shore and barrier reefs, which are raised to the 

 same level, and where a shore reef does not exist, by the de- 

 tached masses and clusters of living coral that are found at 

 those islands in only three or four feet of water, and within a 

 few yards of the beach, quite equalling in size any that are 

 found upon the sea reefs, which clusters must both have 

 grown at a considerably greater depth, and required a long 

 time to attain their present magnitude. 



In the lectures to which allusion has been made, the island 

 of Tahiti was incorrectl}?' represented in ground plans of it 

 exhibited by Prof. Lyell, and also described by him, as sur- 

 rounded by a reef enclosing a continuous lagoon of nearly 

 uniform width between it and the shore. Of a fact so im- 

 portant in its geological bearings as the co-existence of a 

 fringing and lagoon-enclosing reef at this island, the distin- 

 guished lecturer was, I presume, not aware, inasmuch as it was 

 in no manner alluded to by him. There is scarcely any por- 

 tion of the reef which I have not visited, and so far from en- 

 circling the island, the lagoon only exists at intervals, and in 

 many of these a shore reef runs out so far as to leave but 

 a narrow boat channel between it and the outer one. Some- 

 times it terminates in a cul de sac ; in other places it commu- 

 nicates with the sea by two passages near its extremities, thus 

 isolating a portion of the outer reef, and there are parts of the 

 coast where for miles the two reefs appear to have united, and 

 there is no intervening canal ; so that the natives wade from 

 the beach to the breakers. It would be nearer the truth, to 

 state that instead of a continuous lagoon, there is a nearly 

 continuous fringing reef, surrounding the island and varying 

 from a few yards to more than a mile in width, and that the 

 lagoons merely form canals between this and the sea reef. 

 Like the latter, these shore reefs are in general very steep. 

 There is one in Pappeiti, the principal harbor, forming a sort 

 of natural pier, alongside of which a vessel can lie in thirty 

 or forty feet of water, so close that a person may step from 

 her channels, upon the reef, where it is not more than eighteen 

 inches or two feet deep. 



