STRUCTURE OF CORAL ISLANDS. LTP 
tides, as they rise, cover it with water throughout, and 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. / On moving these masses, which gener- 
ally rest on their projecting angles and have an open space 
beneath, the waters at once become alive with fish, shrimps, 
and crabs, escaping from their disturbed shelter; and beneath, 
appear various Actiniz or living flowers, the spiny echini and 
sluggish biche-de-mar, while swarms of shells, having a soldier 
crab for their tenant, walk off with unusual life and stateliness. 
Moreover, delicate corallines, Ascidiz and sponges tint with 
lively shades of red, green and pink, the under surface of the 
block of coral which had formed the roof of the little grotto. 
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. They are 
probably a result of a subterranean movement or shaking. 
The beach consists of coral pebbles or sand, with some 
worn shells, and occasionally the exuvie 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 arti- 
ficial wall or embankment running parallel with the shores. . 
On Clermont Tonnerre, the first of these islands visited by us, 
the natives seen from shipboard, standing spear in hand along 
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