106 



land by a broad and deep cbannel of smooth water ; the outer 

 side of the encircling reef plunges into very deep water, whilst 

 the intervening channel represents the lagoon of an Atoll. 



Fig. 2. — Bolabola Island. 

 The accompanying sketch (Fig. 2) taken from the voyage of 

 the Coquille, representing the Barrier reef seen from within, 

 from one of the high peaks of the Island of Bolabola, gives a good 

 idea of this form of encircling reef, which imparts a most 

 singular and picturesque character to the scenery of the islands 

 they surroimd. As in Whitsunday Island, the whole of that 

 part of the reef which is above water is converted into land: 

 this is a circumstance of rare occurrence; more usually a snow- 

 white line of great breakers, with here and there an islet 

 crowned by cocoa-nut trees, separates the smooth waters of the 

 lagoon channel from the waves of the open sea. 



Balbi called Barrier reefs. Atolls "with high land rising from 

 within their central expanse," and Daewin has shewn that 

 they are Atolls in one phase of their growth. Ellis, in his 

 "Polynesian Researches," states that these reefs lie in general at 

 a distance of from one to one-and-a-half miles, or even three 

 miles, from the shore. The central mountains are generally 

 bordered by a fringe of flat, marshy land, from one to four miles 

 in width, consisting of Coral sand, and other detritus, derived 

 from the lagoon channel, or soU washed down from the hills; 

 this silting-up process is only the slow conversion of the lagoon 

 channel into dry land, by the gradual sinking of the island 

 and the upward growth of the Coral forming the Barrier reef 

 out at sea. 



