STRUCTURE OF CORAL REEFS. 11 



The rock of the reef, wherever broken, exhibits a compact tex- 

 ture. In some parts it consists of coral fragments of quite large 

 size firmly cemented : other portions are a finer coral breccia, or 

 conglomerate : and still others, more common, are solid white 

 limestones, as impalpable and homogeneous in texture as the sec- 

 ondary limestone of our continents, and usually much harder. 

 It is rare to meet with any corals in this reef-rock retaining the 

 original position of growth. It is at once apparent that the rock 

 consists of the debris of the coral fields, consolidated by a calca- 

 reous cement ; and the great abundance of the finer variety of 

 rock indicates that much of it has originated from coral sand or 

 mud. Wherever broken, it is found to present the same charac- 

 ter as here described, a texture indicating a detritus origin. This 

 reef-rock is formed in the midst of the waves ; and we shall here- 

 after show that to this fact it owes many of its peculiarities. Be- 

 sides corals, the shells of the seas contribute to it, and it some- 

 times contains them as fossils, along with bones of fish, exuvias 

 of crabs, spines and fragments of echini, and other remains of or- 

 ganic life inhabiting reef-grounds. 



Inner reefs. — In the still waters of the inner channels or la- 

 goons, when of large extent, we find corals growing in their great- 

 est perfection, and the richest views are presented 10 the explorer 

 of coral scenery. There are many regions — in the Feejes, exam- 

 ples are common — where a remote barrier encloses as pure a sea 

 as the ocean beyond; and the greatest agitation is only such as 

 the wind may excite on a narrow lake or channel. This condi- 

 tion gives rise to some important peculiarities of structure in the 

 inner reefs. 



In the general appearance of the surface, however, they much 

 resemble the outer reefs. They are nearly flat, and though mostly 

 bare of life, and much covered with coral sand, there are seldom 

 any large accumulations of coral debris. The margin is generally 

 less abrupt : yet there is every variety, from the gradually sloping 

 bed of corals to the bluff declivity with its clinging clumps. In dif- 

 ferent parts, there are many portions still under water at the low- 

 est tides; and here, (as well as upon the outer banks,) fine fish- 

 ing sport is afforded the natives, who wade out at ebb tide with 

 spears, pronged sticks, and nets, to supply themselves with food. 

 The lover of the marvellous may find abundant gratification by 

 joining in such a ramble; among coral plants and flowers, with 

 fishes of fantastic colors, starfish, echini, and myriads of other 

 beings which science alone has named, fit inhabitants of a coral 

 world, there is on every side occasion for surprise and admiration. 



Between the large reefs, which spread a broad surface at the 

 water's edge of lifeless coral rock, sometimes of great extent, there 

 are other patches, still submerged, which are covered with grow- 

 ing corals throughout. They are of different elevations; and 

 though at times but a few yards in breadth, there is often along- 



