On Coral Reefs and Islands. 359 
» A few small coral islands are simple reefs without lagoons. In 
some cases they are bare banks of coral; but generally, the usual 
vegetation of the islands has obtained a foothold, and affords some 
protection against the glare of the coral sand. ‘ 
With these general remarks we may enter upon the more par- 
ticular consideration of the characters of reefs and islands. 
2. Cyaractrers oF F'rincinc anp Barrier ReEers. 
a. General features. 
Fringing reefs have been described as those that directly adjoin 
the shores of an island; and the barrier, as the exterior reefs, 
separated from the fringing reef, or from. the shores when there 
is no inner reef, by an open channel. 
ile there are only narrow shore-reefs to many islands, around 
others, a distant barrier extends like an artificial mole, sometimes 
ten or even fifteen miles from the land, and enclosing not only 
one, but at times several islands. Between the narrow fringing 
platform and these remote barriers, there is every possible varia- 
tion as to extent and relative position. The inner channel is 
head wind with a depth of twenty, thirty, or even fifty fathoms. 
Yet hidden reefs make caution necessary. Patches from a few 
* These varieties of form and position are well exemplified in a 
single group of islands—the Feejees; and we would refer the 
er to a reduced copy of the admirable chart of this Archi- 
pelago by the Expedition.* 
Near the middle of the chart is the island Goro; its shores, 
excepting the western, are bordered by a fringing reef. The island 
Angau, south of Goro, is encircled by a coral breakwater, which 
on the southern and western sides runs far from the shores, and 
is a proper barrier reef, while on the eastern side, the same reef is 
attached to-the coast and is a fringing reef. From these exam- 
ples it is perceived that there. is no proper distinction as regards 
mode of formation between barrier and fringing reefs. It is also 
apparent that while a reef is sometimes quite encircling, in other 
instances it is interrupted along certain shores, or may want- 
ing along a large part of a line of coast; and occasionally the 
reef may- be confined to a single point of an island. . 
* For this chart, see Capt. Wilkes's Narrative of the Exploring Expedition, or the 
i iter. ‘ ae 
_ Geological Report of the wri 
. 
