Ch. III. 
FRINGING REEFS. 
73 
more or less perfect, occur on other coasts. In these 
cases I suspect that the shallow channel, (which no 
iloubt during storms is occasionally obliterated,) is 
scooped out by the flowing away of the water thrown 
beyond the line on which the waves break with the 
greatest force. At Pernambuco the bar of hard sand- 
stone, before alluded to, has the same external form 
and height as a coral reef, and extends nearly parallel to 
the coast ; within this bar currents, apparently caused 
by the water thrown over it during the greater part of 
each tide, run strongly, and are wearing away its inner 
wall. From these facts it can hardly be doubted that 
within most fringing reefs, especially within those 
lying some distance from the land, a return stream 
must carry away the water thrown over the outer edge ; 
and the current thus produced would tend to prevent 
the channel being filled up with sediment, and might 
even deepen it under certain circumstances. To 
this latter belief I am led, by finding that channels are 
almost universally present within the fringing reefs of 
those islands which have undergone recent elevatory 
movements ; and this could hardly have been the case 
if the conversion of the very shallow channel into land 
had not been counteracted to a certain extent. 
A fringing-reef, if elevated in a perfect condition 
above the level of the sea, would present the singular 
appearance of a broad dry moat bounded by a low wall 
or mound. The author 1 of an interesting pedestrian 
1 Voyage & l’lsle de France, par un Officier du Roi, Part i. 
pp. 192, 200. 
