DESCRIPTION OF THE EXPEDITION. 137 
the flat extends out for 2} miles, its two sides being quite similar to the reefs of the 
island, while a bare patch in the centre represents the former position of a sandbank 
sketched by the late Admiral Sir W. L. Wharton when in the ‘Shearwater’ in 1875. 
Shoal patches stretch out from its point for an additional 2 miles, and there are many 
isolated patches and reefs to the south-west. Elsewhere the bank presents no changes, 
its rim being very regular with 11 to 14 fathoms of water, and the centre with 15 to 
18 fathoms. 
f Sea Miles 
Coetivy (after the Admiraity chart). 
The east, weather or seaward, reef differs in certain points from any reefs which either 
of us had up to that time seen; instead of a single line of breakers, there is a broad belt 
in which the same wave rises and breaks a second time. This is due to the slope 
to seaward being gradual for the first 10 fathoms or more, even down to the edge 
of the steep, and also to the bottom being covered with long sea-grass (Cymodocea), 
which by its friction prevents the pounding action of the breakers and certainly goes 
far to prevent the formation of a distinct edge to the reef. The latter can scarcely be 
said to exist as a definite structure, although there is an area which shows a number of 
masses exposed at low tide, broken by relatively broad channels with sloping sides. The 
20* 
