CORAL REEFS AND ISLANDS. 31 
Coral reefs.—A wide platform of rock, covered with the sea except 
at low tide, borders most of the high islands of the Pacific. It is a 
vast accumulation of coral, based upon the bottom in the shallow 
waters of the shores. ‘This bank or table of coral rock, is of varying 
width, from a few hundred feet to a mile or more; and, although the 
surface is usually nearly flat, it is often intersected by irregular boat- 
channels, or occasionally incloses large bays, affording harbour pro- 
tection to scores of ships. In very many instances the reef stands at 
a distance from the shores like an artificial mole, leaving a wide and 
deep channel between it and the land; and within this channel are 
other coral reefs, some in scattered patches and others attached close 
to the shore. The inner reef in these cases is distinguished, as the 
fringing reef, and the outer, as the barrier reef. The sea rolls in 
heavy surges against the outer margin of the barrier; but the still 
waters of a lake prevail within, affording safe navigation for the 
tottling canoe, sometimes through the whole circuit of an island: and 
not unfrequently ships may pass, as by an internal canal, from harbour 
to harbour around the island. The reef is covered by the sea at high 
tide, yet the smoother waters indicate its extent, and a line of breakers 
its outline. Occasionally a green islet rises from the reef, and in 
some instances, a grove of palms stretches along the barrier for miles, 
where the action of the sea has raised the coral structure above the 
waves. 
The sketch annexed conveys some idea of the peculiar features 
presented by a Pacific island and its encircling reefs, though, in order 
to fill out the scene, the jagged heights and deep gorges of the island 
into all the peculiarities of coral formations. The author has deemed it therefore in- 
cumbent upon him to present a full account from his own observations, without special 
reference to the writings of others, excepting a faithful acknowledgment wherever any 
facts or views have been cited from them. The Report is therefore complete in itself, 
and has the advantage, where it agrees with previous observers, of being independent 
testimony to the facts. 
