40 ON CORAL REEFS AND ISLANDS. 



Shore platform narrow, and intersected by channels. Shores 

 lined by reef-rock, two or three feet out of water, indicating an 

 elevation of the island. This reef-rock consists of various corals 

 firmly cemented. Within the lagoon, knolls of coral, but none 

 near the shore on the leeward side. 



Fakaafo or Bow 'ditch's.— 9° 20' S., 171° 5' W. 6f miles 

 by 4. Shape nearly triangular. Circuit seventeen miles, about 

 six of which are wooded in several patches, separated by long bare 

 intervals. A large lagoon, but no ship entrance. Height of island, 

 fifteen feet. Width to the lagoon, one hundred to two hundred 

 yards. Soil of the island coral sand, speckled black with results 

 of vegetable decomposition. Shore platform narrow. At outer 

 edge a depth of three fathoms, and from thence gradually deep- 

 ens, and abounds in fine corals for fifty yards, when it deepens 

 abruptly. Coral reef-rock elevated three or four feet, indicating 

 an elevation of the island. Lagoon shallow, with some growing 

 coral, but none near the shore. Some corals growing on the 

 platform, near its margin, mostly small Madrepores, Astrseas, Nul- 

 lipores. Fragments of pumice were found among the natives, 

 which had floated to the island. 



Ahii, or Peacock's Island, Paumotu Archipelago. — 14° 30' S., 

 146° 20' W. 13 miles by 6, trending N. E. by E. Shape irreg- 

 ularly oblong. A large lagoon, having an entrance for small ves- 

 sels on the west. Reef wooded throughout nearly its whole cir- 

 cuit. Lagoon shallow, and much obstructed by growing coral, 

 the latter giving the water over it a clear light green color. Plat- 

 form, or outer coral shelf of the island, about two hundred and 

 fifty feet wide ; under water except at the lowest tides. Margin 

 highest, and covered with Nullipore incrustations, which give it 

 a variety of delicate shades of color, mostly reddish, or peach- 

 blossom red, rose, scarlet. For thirty to fifty feet from the mar- 

 gin, very cavernous, and containing many Tridacnae, lying half 

 imbedded, with the variously tinted mantle expanded when the 

 surface is covered with water. Rock of the platform either a 

 compact white limestone or a solid conglomerate ; dead over its 

 surface, excepting a few Madrepore tufts or Astraeas near the mar- 

 gin in pools. In this shelf there were long fissures, extending 

 nearly parallel with the shore, a quarter to half an inch wide at 

 top, and continuing sometimes a fourth of a mile or more. These 

 fissures were commonly filled with coral sand. The higher parts 

 of the island either consisting of loose blocks of coral or covered 

 with some soil ; the soil mostly of comminuted coral and shells, 

 with dark particles from vegetable decomposition intermingled. 

 On the bottom exterior to the shore platform, observed the same 

 corals growing as occurred in fragments upon the island ; but the 

 larger part of the bottom was without coral, or consisted only of 

 sand. 



