s 



On Coral Reefs and Islands. 33 



^ 



^ 



Shore platform and emerged land. — The shore platform is 

 from one to three hundred feet in width, and has the general fea- 

 tures of a half-submerged outer reef. Its pecuharities arise solely 

 from the accumulations which have changed the reef into an 

 island. Much of it is commonly bare at low tide, though there 

 are places where it is always covered with a few inches or a foot 

 of water; and the elevated edge, the only part exposed, often 

 seems like an embankment preventing the water from running 

 oft. The tides, as they rise, cover it with water throughout, and 

 \i bear over it coral fragments and sand, comminuted shells and 



other animal remains, to add them to the beach. The heavier 

 seas transport larger fragments; and at the foot of the beach 

 there is often a deposit of blocks of coral or coral rock, a cubic 

 foot or so in size, which low tide commonly leaves standing in a 

 few inches of water. f 



Besides the deep channels cutting into the margin of the reef 

 and giving it a broken outline, there are in some instances long 

 fissures intersecting its surface. On Aratica, (Carlshoff*,) and 

 Ahii, (Peacock Island,) they extended along for a fourth to half 

 a mile, generally running nearly parallel with the shore, and at 

 top were from a fourth to half an inch wide. These fissures are 

 not essential features of the reef, and will come up for consider- 

 ation on a future page of this work. 



The headi usually slopes at an angle of 3a to Ao degrees, and 

 consists of coral pebbles or sand, with some worn shells, and oc- 

 casionally the exuvice of crabs and bones of fishes. Owing to 

 its whiteness, and the contrast it affords to the massy verdure 

 above, it is a remarkable feature in the distant view of these 

 islands, and often seemed like an artificial wall or embankment 

 running parallel with the shores. On Clermont Tonnerre, the 

 first of these islands visited by us, the natives seen from ship- 

 board, standing spear in hand along the top of the beach, were 

 believed by some to be keeping patrol on the ramparts o( a kind 

 of fortification. This deception arose from the dazzling white- 

 ' ness of the coral sand, in consequence of which, the slope of the 

 beach was not distinguished in so distant a view. 



The emerged lajid beyond the beach, in its earliest stage when 

 barely raised above the tides, appears like a vast field of ruin 

 Angular masses of coral rock, varying in dimensions from one to 

 a hundred cubic feet, lie pil^d together in the utmost confusion; 

 and they are so blackened by exposure, or from incrusting lich- 



im 



S, 



m 



t On moving these ma^ep, -wlxich gon^gAy reiit on ilnnr ]>rojectiri^^ angles and have 

 open space beneath, the waters :itouwL -Bae alive wiib fi^Ii, toLrimp, and crab- 



escaping 

 flowers, the spi 



umi^ 



jsoldier 6r:xh fftwmmB tenant walk oil with unii-iii.l lifu and strrtoiin^'sd. HoTnui^dtA- 

 jcate coraliine^^ ^''^Jdic-e and sj)onirf*s tint with Uvc-iy f^hud--- of red, «rreon. inui-pink, 

 the under surfalfW the block of a>ral mindi had ivrmS *^" t. K)f of \M UulAtfrotto. 



Set-vd Seeii:s, VoL^I,Xd. SI-t-JuIj, 185L ^ ,^5 ^ ^ 



¥ 



m*- ^ 



<^ * .. B 



