40 CORAL FORMATIONS. 
to be found here, and frequently over large areas, the solid white lime- 
stone already described, showing internally no evidence of its coral 
origin, and containing only a few shells or imbedded fossils. 
The formation of inner reefs goes on at a less rapid rate than that 
of the outer, as the process depends on growth unaided, except in a 
comparatively small degree, by the action of the waves. Moreover, 
as we shall explain more particularly in another place, impure or fresh 
waters and currents often operate to retard their growth. 
Owing to the last-mentioned cause, the inner reefs are not usually 
joined close to the beach. ‘They stand off a little, separated by an 
interval of shallow water. At Mathuata, in the Feejees, however, the 
reef extends quite up; and it is the more remarkable as the country 
is a plain, the site of a Ieejee village, and a mile or two back stands 
a igh bluff. On an island off this part of Vanua Lebu is another 
example of this fact, and many more might be cited. In such cases, 
however, there is evidence that the shores upon which the corals grew 
were bare rocks, instead of moving beach-sands. 
From these descriptions it appears that the main distinction between 
the inner and outer reefs consists in the less fragmentary character of 
the rock in the former case, the less frequent accumulations of debris 
on their upper surface, and the more varied features and slopes of the 
margin. Moreover, the Nullipores, which seem to flourish best in the 
breakers, are of less extent, or but sparingly met with. 
The inner margin of a barrier reef, it should be observed, is entitled 
to rank with inner reefs, as its corals grow in the same quiet waters, 
and under like circumstances. The variety of coral zoophytes is also 
greater in the stiller waters, and there are species peculiar to the dif- 
ferent regions, as explained on a following page. 
Channels among reefs—To complete this review of the general 
appearance and constitution of reef formations, it remains to add some 
particulars respecting the channels which intervene between coral 
patches, or separate them from the shores of an island, and also to 
describe the coral accumulations forming beaches. 
The reef of New Holland has been instanced as affording an ex- 
ample of one of the larger reef-channels, varying from thirty to sixty 
miles in width, and as many fathoms in depth. The reefs west of the 
large Feejee Islands offer another remarkable example, the reef-grounds 
being in some parts twenty-five miles wide, and the waters within the 
barrier, where sounded, twelve to forty fathoms in depth. The barrier 
in this instance may be from a few hundred yards to a half a mile in 
