22 POLYNESIAN RESEARCHES. 
the spectator can follow the splendid aqueous 
gallery which they appear to have reared, with 
loud and hollow roar they fall in magnificent 
desolation, and spread the gigantic fabric in froth 
and spray upon the horizontal and gently broken 
surface of the coral. 
In each of the islands, and opposite the large 
valleys, through which a stream of water falls into 
the ocean, there is usually a break, or opening, in 
the line of reef that surrounds the shore—-a most 
wise and benevolent provision for the ingress and 
egress of vessels, as well as a singular phenomenon 
in the natural history of these marine ramparts. 
Whether the current of fresh water, constantly 
flowing from the rivers to the ocean, prevents the 
tiny architects from building their concentric walls 
in one continued line, or whether in the fresh 
water itself there is any quality inimical to the 
growth or increase of coral, is not easy to deter¬ 
mine ; but it is a remarkable fact, that few openings 
occur in the reefs which surround the South Sea 
Islands, excepting opposite those parts of the 
shore from which streams of fresh water flow into 
the sea. Reefs of varied, but generally circum¬ 
scribed extent, are frequently observed within the 
large outer barrier, and near the shore, or mouth 
of the river; but they are formed in shallow places, 
and the coral is of a different and more slender 
kind, than that of which the larger reef, rising from 
the depths of the ocean, is usually composed. There 
is no coral in the lagoons of the large islands. 
The openings in the reefs around Sir Charles 
Sanders’ Island, Maurua, and other low islands, 
are small and intricate, and sometimes altogether 
wanting, probably because the land, composing 
these islands, collects but a scanty portion of 
